0000000001167314
AUTHOR
Eulogio Oset Báguena
Chiral dynamics in the gamma p ->pi(0)eta p and gamma p ->pi K-0(0)Sigma(+) reactions
Using a chiral unitary approach for meson-baryon scattering in the strangeness zero sector, where the N∗(1535) resonance is dynamically generated, we study the reactions γp→π0ηp and γp→π0K0Σ+ at photon energies at which the final states are produced close to threshold. Among several reaction mechanisms, we find the most important is the excitation of the Δ∗(1700) state which subsequently decays into a pseudoscalar meson and a baryon belonging to the Δ(1232) decuplet. Hence, the reaction provides useful information with which to test current theories of the dynamical generation of the low-lying 3/2− states. The first reaction is shown to lead to sizable cross sections and the N∗(1535) resona…
Delta excitation in K+-nucleus collisions
We present calculations for \Delta excitation in the (K^+,K^+) reaction in nuclei. The background from quasielastic K^+ scattering in the \Delta region is also evaluated and shown to be quite small in some kinematical regions, so as to allow for a clean identification of the \Delta excitation strength. Nuclear effects tied to the \Delta renormalization in the nucleus are considered and the reaction is shown to provide new elements to enrich our knowledge of the \Delta properties in a nuclear medium.
(B)over-bar(0), B- and (B)over-bar(S)(0) decays into J/psi and K (K)over-bar or pi eta
12 pages.- 6 figures.- v2: discussion added, references added
Baryonic Resonances from Baryon Decuplet-Meson Octet Interactions and the Exotic Resonance S=1, I=1, J^P=3/2-
Using the lowest order chiral Lagrangian we study s-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons. We find two bound states in the flavour SU(3) limit corresponding to the octet and decuplet representations. These are found to split into eight different trajectories in the complex plane when the SU(3) symmetry is broken gradually. Finally, we are able to provide a reasonable description for a good number of 4-star 3/2- resonances listed by the Particle Data Group. In particular, the Xi(1820), the Lambda(1520) and the Sigma(1670) states are well reproduced. We predict a few other resonances and also evaluate the couplings of the observed resonances to the var…
Y(4260) as a J/Sigma KK system
A study of the J/ψππ and J/ψKK¯ systems, treating them as coupled channels, has been made by solving the Faddeev equations, with the purpose of investigating the possibility of generation of the JPC=1−−, Y(4260) resonance due to the interaction between these three mesons. In order to do this, we start by solving the Bethe-Salpeter equation for the two pseudoscalar and for the vector-pseudocalar meson systems using the amplitudes obtained from the lowest order chiral Lagrangians as potentials. With the t-matrices generated from these potentials, which contain the poles of the σ, f0(980) and a0(980) resonances for the pseudoscalar-pseudoscalar system and the pole of the X(3872), alongwith oth…
Study of the f(2)(1270), f '(2)(1525), and (K)over-bar(2)*(1430), f(0)(1370) and f(0)(1710) production from psi(nS) and Upsilon(nS) decays
Based on previous studies that support the important role of the f(2)(1270), f'(2)(1525), and (K) over bar (2)*(1430) resonances in the J/psi[psi(2S)] -> phi(omega)VV decays, we make an analysis of the analogous decays of Upsilon(1S) and Upsilon(2S), taking into account recent experimental data. In addition, we study the J/psi and psi(2S) radiative decays and we also made predictions for the radiative decay of Upsilon(1S) and Upsilon(2S) into gamma f(2)(1270), gamma f(2)'(1525), gamma f(0)(1370) and gamma f(0)(1710) comparing with the recent results of a CLEO experiment. We can compare our results for ratios of decay rates with eight experimental ratios and find agreement in all but one cas…
The $(\pi^-,\gamma\gamma)$ reaction in nuclei and the $\sigma$ meson in the medium
A theoretical analysis of the $(\pi^-,\gamma\gamma)$ reaction in nuclei is made in order to find the viability of this reaction to test modifications of the $\sigma$ meson mass in nuclear matter. The $\pi\pi$ correlation in the scalar-isoscalar channel in nuclear matter could, in principle, manifest itself in this reaction since it plays an important role in the $\pi\pi\to\gamma\gamma$ mechanism. But we conclude that this effect is hardly visible in this reaction due to the strong background of the pion-Bremsstrahlung terms. Only with some special cuts and for some polarization states are the effect visible at the cost of a strong reduction in the cross section.
A Theoretical approach to the (pi-, gamma gamma) reaction in nuclei
We have studied the pion^{-} capture in nuclei leading to two photons, using improved many body methods which have been tested with success in one photon pion^{-} radiative capture, muon^{-} capture and neutrino scattering. The qualitative features of the experimental data are reproduced but there are still some disagreement at small relative photon angles. The reaction is a potential source of information on details of the gamma-gamma-pion-pion vertex where chiral corrections can be relevant. New and more precise experiments are planned which make calculations like the present one relevant and opportune.
Improved fixed center approximation of the Faddeev equations for the (K)over-bar N N system with S=0
We extend the Fixed Center Approximation (FCA) to the Faddeev Equations for the K¯NN system with S=0, including the charge exchange mechanisms in the K¯ rescattering which have been ignored in former works within the FCA. We obtain similar results to those found before, but the binding is reduced by 6 MeV. At the same time we also evaluate the explicit contribution the πNΣ intermediate state in the three body system and find that it produces and additional small decrease in the binding of about 3 MeV. The system appears bound by about 35 MeV and the width omitting two body absorption, is about 50 MeV.
Transparency ratio in gamma A -> eta ' A ' and the in-medium eta ' width
The photoproduction of \eta'-mesons off different nuclei has been measured with the CBELSA/TAPS detector system for incident photon energies between 1500 - 2200 MeV. The transparency ratio has been deduced and compared to theoretical calculations describing the propagation of \eta'-mesons in nuclei. The comparison indicates a width of the \eta' -meson of the order of \Gamma= 15-25 MeV at \rho =\rho_0 for an average momentum p_{\eta'} = 1050 MeV/c, at which the \eta'-meson is produced in the nuclear rest frame. The inelastic \eta' N cross section is estimated to be 3 - 10 mb. Parameterizing the photoproduction cross section of \eta'-mesons by \sigma(A) = \sigma_0 A^{\alpha}, a value of \alph…
(B)over-bar(0) and (B)over-bar(s)(0) decays into J/psi and f(0)(1370), f(0)(1710), f(2)(1270), f(2)'(1525), K-2*(1430)
We make predictions for the ratios of branching fractions of (B) over bar (0) and (B) over bar (0)(s) decays into J/psi and the scalar mesons f(0)(1370), f(0)(1710) or tensor mesons f(2)(1270), f(2)'(1525), K-2*(1430). The theoretical approach is based on results of chiral unitary theory where these resonances are shown to be generated from the vector meson-vector meson interaction. Eight independent ratios can be predicted, and comparison is made with the recent data on (B) over bar (0)(s) decay into J/psi f(2)'(1525) versus the (B) over bar (0)(s) decay into J/psi f(2)(1270).
KD, eta Ds interaction in finite volume and the Ds*0(2317) resonance
An SU(4) extrapolation of the chiral unitary theory in coupled channels done to study the scalar mesons in the charm sector is extended to produce results in finite volume. The theory in the infinite volume produces dynamically the $D_{s^*0}(2317)$ resonance by means of the coupled channels $KD$, $\eta D_s$. Energy levels in the finite box are evaluated and, assuming that they would correspond to lattice results, the inverse problem of determining the bound states and phase shifts in the infinite volume from the lattice data is addressed. We observe that it is possible to obtain accurate $KD$ phase shifts and the position of the $D_{s^*0}(2317)$ state, but it requires the explicit considera…
phi decay in nuclei
We have studied the decay of the \phi meson in nuclear matter by taking into account the renormalization of the K and \bar{K} mesons in the medium. We separate the contribution of the total width into different reaction channels, K\bar{K} and KYh, the latter ones associated with the \phi N \to K^+ Y reactions. We find a total width at normal nuclear matter density of about 22 MeV, considerably larger than the free one.
Hidden charm dynamically generated resonances and the e(+)e(-) -> J/psi D(D)over-bar, J/psi D(D)over-bar * reactions
We analyze two recent reactions of Belle, producing DD¯ and DD¯∗ states that have an enhancement of the invariant DD¯, DD¯∗ mass distribution close to threshold, from the point of view that they might be indicative of the existence of a hidden charm scalar and an axial vector meson states below DD¯ or DD¯∗ thresholds, respectively. We conclude that the data is compatible with the existing prediction of a hidden charm scalar meson with mass around 3700 MeV, though other possibilities cannot be discarded. The peak seen in the DD¯∗ spectrum above threshold is, however, unlikely to be due to a threshold enhancement produced by the presence, below threshold, of the hidden charm axial vector meso…
Non-perturbative chiral approach to K(-)p ->gamma Y reactions
A recently developed nonperturbative chiral approach to describe the S=-1 meson-baryon reactions has been extended to investigate the near threshold K−p→γΛ,γΣ0 reactions. With the parameters governed by chiral SU(3) symmetry, we show that the predicted branching ratios ΓK−p→γΛ/ΓK−p→all and ΓK−p→γΣ0/ΓK−p→all are close to the experimental values. The coupling with the η channels, which was shown to be important in the S=−1 meson-baryon reactions, is also found to be significant here. Our results are consistent with the interpretation of the Λ(1405) as a quasi-bound meson-baryon state as found in other similar chiral approaches.
Chiral dynamics of the p wave in K(-)p and coupled states
We perform an evaluation of the p-wave amplitudes of meson-baryon scattering in the strangeness S=-1 sector starting from the lowest order chiral Lagrangians and introducing explicitly the Sigma^* field with couplings to the meson-baryon states obtained using SU(6) symmetry. The N/D method of unitarization is used, equivalent, in practice, to the use of the Bethe-Salpeter equation with a cut-off. The procedure leaves no freedom for the p-waves once the s-waves are fixed and thus one obtains genuine predictions for the p-wave scattering amplitudes, which are in good agreement with experimental results for differential cross sections, as well as for the width and partial decay widths of the S…
Decay of axial-vector mesons into VP and P gamma
We propose a phenomenological Lagrangian for the decay of the SU(3) nonets of the axial-vector mesons of $J^{PC}=1^{+-},1^{++}$ into a vector meson and a pseudoscalar constructed with tensor fields for the vector and axial-vector mesons. The formulation leads to a good reproduction of the different decay branching ratios and assuming vector meson dominance (VMD) it also leads to good results for the radiative decay of the $a_1$ into pion and photon, and in agreement with the structure proposed in the chiral tensor formulation of radiative decay of axial-vector mesons. The two SU(3) parameters and the mixing angle of $K_{1A}$ and $K_{1B}$ needed to give the physical $K_1(1270)$ and $K_1(1400…
Chiral Dynamics of Hadrons in Nuclei
In this talk I report on selected topics of hadron modification in the nuclear medium using the chiral unitary approach to describe the dynamics of the problems. I shall mention how antikaons, $\eta$, and $\phi$ are modified in the medium and will report upon different experiments done or planned to measure the $\phi$ width in the medium.
Lambda(b) -> J/psi K Xi decay and the higher order chiral terms of the meson baryon interaction
We study the weak decay of the Lambda(b) into J/psi K Xi. and J/psi eta Lambda states, and relate these processes to the Lambda(b) -> J/psi(K) over barN decay mode. The elementary weak transition at the quark level proceeds via the creation of a J/psi meson and an excited sud system with I = 0, which upon hadronization leads to (K) over barN or eta Lambda pairs. These states undergo final-state interaction in coupled channels and produce a final meson-baryon pair. The K. state only occurs via rescattering, hence making the Lambda(b) -> J/psi K Xi process very sensitive to the details of the meson-baryon interaction in strangeness S = -1 and isospin I = 0. We show that the corresponding inva…
On the background in the gamma p -> omega(pi(0)gamma)p reaction and mixed event simulation
In this paper we evaluate sources of background of the gamma p -> omega p reaction, with the omega detected through its pi(0)gamma decay channel, to compare with the experiment carried out at ELSA. We find background from gamma p -> pi(0)pi(0)p followed by decay of a pi(0) into two gamma, recombining one pi(0) and one gamma, and from the gamma p -> pi(0)eta p reaction with subsequent decay of the eta into two photons. This background accounts for the data at pi(0)gamma invariant masses beyond 700 MeV, but strength is missing at lower invariant masses which was attributed to photon misidentification events, which we simulate to get a good reproduction of the experimental background. Once thi…
LHCb pentaquark as a D^* Sigma_c-D^* Sigma_c^* molecular state
We perform a theoretical analysis of the Λb→J/ψK−p reaction from where a recent LHCb experiment extracts a Λ(1405) contribution in the K−p spectrum close to threshold and two baryon states of hidden charm in the J/ψp spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and JP of the experiment; concretely some states built up from the J/ψN, D¯∗Λc, D¯∗Σc, D¯Σ∗c and D¯∗Σ∗c coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the K−p mass distribution close to threshold and the peak of the J/ψp distribution, with valu…
Lambda(1405) production in the pi-p -> K-0 pi Sigma reaction
We discuss the mechanisms that lead to Lambda(1405) production in the pi(-)p-->K(0)piSigma reaction. The problem has gained renewed interest after different works converge to the conclusion that there are two resonances around the region of 1400 MeV, rather than one, and that they couple differently to the piSigma and (K) over barN channels. We look at the dynamics of that reaction and find two mechanisms which eventually filter each one of the resonances, leading to very different shapes of the piSigma invariant mass distributions. The combination of the two mechanisms leads to a shape of this distribution compatible with the experimental measurements.
The K(-)d -> pi Sigma n reaction revisited
The appearance of some papers dealing with the K(-)d -> pi Sigma n reaction, with some discrepancies in the results and a proposal to measure the reaction at forward n angles at J-PARC justifies to retake the theoretical study of this reaction. We do this in the present paper showing results using the Watson approach and the truncated Faddeev approach. We argue that the Watson approach is more suitable to study the reaction because it takes into account the potential energy of the nucleons forming the deuteron, which is neglected in the truncated Faddeev approach. The paper shows the strength and limitations of both approaches and we perform calculations using four different approximations.…
Inclusive Neutrino Scattering in C-12: Implications for nu_mu to nu_e Oscillations
We study inclusive nu_e and nu_mu cross sections in C-12 in a theory that takes into account significant nuclear renormalization of strengths. Our calculation is in excellent agreement with the measured inclusive muon capture rate and the flux-averaged nu_e cross section, but overestimates the flux-averaged nu_mu inclusive cross section. These reactions are of crucial relevance to the issue of possible nu_mu to nu_e oscillations.We also calculate the flux-averaged cross sections in C-13 and Al-27, which are found to be consistent with the available experimental result.
$A$ dependence of the $\gamma$- and $p$-induced production of the $\Lambda(1520)$ from nuclei
Using results of a recent calculation of the $\Lambda(1520)$ in the nuclear medium, which show that the medium width is about five times the free width, we study the A dependence of the $\Lambda(1520)$ production cross section in the reactions $\gamma ~A \to K^+ \Lambda(1520) A^\prime$ and $p~ A \to p~ K^+ \Lambda(1520) A^\prime$. We find a sizable A dependence in the ratio of the nuclear cross sections for heavy nuclei with respect to a light one due to the large value of the $\Lambda(1520)$ width in the medium, showing that devoted experiments, easily within reach in present facilities, can provide good information on that magnitude by measuring the cross sections studied here.
Possible omega bound states in nuclei produced with the (gamma, p) reaction
We perform calculations for ω production in nuclei by means of the (γ,p) reaction for photon energies and proton angles suited to currently running and future experiments in present laboratories. For some cases of possible ω optical potentials, we find that clear peaks are observable when a good resolution in the ω energy is available. We also study the inclusive production of π(0)γ in nuclei around the ω energy and find a double hump structure for the energy spectra, with a peak around a π(0)γ energy of m(ω) -100 MeV, which could easily be misidentified by a signal of an ω bound state in nuclei, while it is actually due to a different scaling of the uncorrelated π(0)γ production and ω prod…
Evaluation of the polarization observables I-S and I-C in the reaction gamma p -> pi(0)eta p
We evaluate the polarization observables I(S) and I(C) for the reaction gamma p -> pi(0)eta p, using a chiral unitary framework developed earlier. The I(S) and I(C) observables have been recently measured for the first time by the CBELSA/TAPS Collaboration. The theoretical predictions of I(S) and I(C), given for altogether 18 angle-dependent functions, are in good agreement with the measurements. Also, the asymmetry d Sigma/dcos theta evaluated here agrees with the data. We show the importance of the Delta(1700) D(33)-resonance and its S-wave decay into eta Delta(1232). The result can be considered as a further confirmation of the dynamical nature of this resonance. At the highest energies,…
Scalar isoscalar pion pairs in nuclei and the A(pi,pi pi)X reaction
The reaction A(pi,pi pi)X has been studied at low energies, paying particular attention to the interaction of the two final pions in the scalar isoscalar (I=J=0) channel. We have developed a microscopic model for the pion production, and then implemented the two pion final state interaction by using the results of a non-perturbative unitary coupled-channels method based in the standard chiral Lagrangians. The resulting model, describes well the reaction on the nucleon for all different isospin channels. Finally, we have considered the reaction in nuclei. Our calculation takes into account Fermi motion, Pauli blocking, pion absorption, and also the strong modification of the pi-pi interactio…
Theta(+) hypernuclei
We present results for the selfenergy of the Theta(+) pentaquark in nuclei associated with two sources: the KN decay of the Theta(+) and the two meson baryon decay channels of the Theta(+) partners in an antidecuplet of baryons. The first source is shown to produce a small potential, unable to bind the Theta(+) in nuclei, while the second source gives rise to a large attractive potential. At the same tune we show that the width of the Theta(+) in nuclei is small, such that, in light and medium nuclei, many bound Theta(+) states would appear with a separation between levels appreciably larger than the width of the states, thus creating an ideal scenario for pentaquark spectroscopy in nuclei.
Deeply bound pionic states with the (Sigma-, Lambda) reaction
We study the reactionΣ − +A→Λ + (Aπ −) with the π− bound in the nucleus, as a means of producing deeply bound pionic states in nuclei, so far unobserved. The reaction is similar to the (n, p) reaction but, because of theΣ −, Λ mass difference, it allows the reaction to occur with smaller momentum transfer, thus increasing the transition probability and reducing the effects of distortion. The ratios of signal to background are one to two orders of magnitude better than in the (n, p) reaction.
Reanalysis of lattice QCD spectra leading to the Ds0*(2317) and Ds1*(2460)
We perform a reanalysis of the energy levels obtained in a recent lattice QCD simulation, from where the existence of bound states of KD and KD* are induced and identified with the narrow D-s0*(2317) and D-s1*(2460) resonances. The reanalysis is done in terms of an auxiliary potential, employing a single-channel basis KD(*()), and a two-channel basis KD(*()), eta D-s(()*()). By means of an extended Luscher method we determine poles of the continuum t-matrix, bound by about 40 MeV with respect to the KD and KD* thresholds, which we identify with the D-s0*(2317) and D-s1*(2460) resonances. Using a sum rule that reformulates Weinberg compositeness condition we can determine that the state D-s0…
Faddeev fixed-center approximation to the N K K(bar) system and the signature of a N*(1920)(1/2+) state
We perform a calculation for the three body NK¯K scattering amplitude by using the fixed center approximation to the Faddeev equations, taking the interaction between N and K¯, N and K, and K¯ and K from the chiral unitary approach. The resonant structures show up in the modulus squared of the three body scattering amplitude and suggest that a NK¯K hadron state can be formed. Our results are in agreement with others obtained in previous theoretical works, which claim a new N∗ resonance around 1920 MeV with spin-parity JP=1/2+. The existence of these previous works allows us to test the accuracy of the fixed center approximation in the present problem and sets the grounds for possible applic…
NDK, (K)over-barDN, and ND(K)over-bar molecules
We investigate theoretically baryon systems made of three hadrons which contain one nucleon and one D meson, and in addition another meson, (D) over tilde, K, or (K) over tilde. The systems are studied using the fixed center approximation to the Faddeev equations. The study is made assuming scattering of a K or a (K) over tilde on a DN cluster, which is known to generate the Lambda(c)(2595), or the scattering of a nucleon on the D (D) over tilde cluster, which has been shown to generate a hidden charm resonance named X(3700). We also investigate the configuration of scattering of N on the KD cluster, which is known to generate the D*(s0)(2317). In all cases we find bound states, with the ND…
eta ->pi(0)gamma gamma decay within a chiral unitary approach revisited
n view of the recent experimental developments on the experimental side in the η→π0γγ decay, and the fact that the Particle Data Group in the on line edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of \cite{eta}, a reevaluation of the decay width of the η in this channel has been done, reducing its uncertainty by almost a factor of two. The new input of the PDG is used and invariant mass distributions and total widths are compared with the most recent results from AGS, MAMI and preliminary ones of KLOE. The agreement of the theory with the AGS and MAMI data is very good, both for the total rates as well as …
A new perspective on the Faddeev equations and the (K)over-bar N N system from chiral dynamics and unitarity in coupled channels
We review recent work concerning the K¯N interaction and Faddeev equations with chiral dynamics which allow us to look at the K¯NN from a different perspective and pay attention to problems that have been posed in previous studies on the subject. We show results which provide extra experimental evidence on the existence of two Λ(1405) states. We then show the findings of a recent approach to Faddeev equations using chiral unitary dynamics, where an explicit cancellation of the two body off shell amplitude with three body forces stemming from the same chiral Lagrangians takes place. This removal of the unphysical off shell part of the amplitudes is most welcome and renders the approach unamb…
Role of meson loops in the f(0)(1370), f(0)(1500), and f(0)(1710) decays into V gamma
We investigate the relevance of the meson loops in the f0(1710) scalar meson decay into one photon and one vector meson, (ρ, ω and ϕ). In particular we estimate the size of the loops coming from the decay of the f0(1710) into two pseudoscalar mesons, containing three pseudoscalar mesons in the loop or two pseudoscalar and one vector meson. The results, despite having large uncertainties, manifest that the contribution of the meson loops to these radiative decays is quite relevant and should be taken into account by the theoretical calculations which use this observables as a test of the possible glueball nature of this resonance.
Ds0*(+/-)(2317) and K D scattering from Bs(0) decay
We study the (B) over bar (0)(s) -> D-s(-)(KD)(+) weak decay, and look at the KD invariant mass distribution, for which we use recent lattice QCD results for the KDinteraction from where the D-s0*(2317) resonance appears as a KD bound state. Since there are not yet experimental data on this reaction, in a second step we propose an analysis method to obtain information on the D-s0* (2317) resonance from the future experimental KD mass distribution in this decay. For this purpose, we generate synthetic data taking a few points from our theoretical distribution, to which we add a 5% or 10% error. With this analysis method, we prove that one can obtain from these ¿data¿ the existence of a bound…
Isospin breaking and f(0)(980)-a(0)(980) mixing in the eta(1405) -> pi(0)f(0)(980) reaction
We make a theoretical study of the eta(1405) -> pi(0)f(0)(980) and eta(1405) -> pi(0)a(0)(980) reactions with an aim to determine the isospin violation and the mixing of the f(0)(980) and a(0)(980) resonances. We make use of the chiral unitary approach where these two resonances appear as composite states of two mesons, dynamically generated by the meson-meson interaction provided by chiral Lagrangians. We obtain a very narrow shape for the f(0)(980) production in agreement with a BES experiment. As to the amount of isospin violation, or f(0)(980) and a(0)(980) mixing, assuming constant vertices for the primary eta(1405) -> pi K-0 (K) over bar and eta(1405) -> pi(0)pi(0)eta production, we f…
Description of the f(2)(1270), rho(3)(1690), f(4)(2050), rho(5)(2350), f(6)(2510) resonances as multi-rho(770) states
In a previous work regarding the interaction of two rho(770) resonances, the f(2)(1270) (J(PC) = 2(++)) resonance was obtained dynamically as a two-rho molecule with a very strong binding energy, 135 MeV per rho particle. In the present work we use the rho rho interaction in spin 2 and isospin 0 channel to show that the resonances rho(3)(1690) (3(--)), f(4)(2050) (4(++)), rho(5)(2350) (5(--)), and f(6)(2510) (6(++)) are basically molecules of increasing number of rho(770) particles. We use the fixed center approximation of the Faddeev equations to write the multibody interaction in terms of the two-body scattering amplitudes. We find the masses of the states very close to the experimental v…
K-bar NN system with chiral dynamics
We have performed a calculation of the scattering amplitude for the three body system K¯NN assuming K¯ scattering against a NN cluster, using the Fixed Center approximation to the Faddeev equations. The K¯N amplitudes, which we take from chiral unitary dynamics, govern the reaction and we find a K¯NN amplitude that peaks around 40 MeV below the K¯NN threshold, with a width in |T|2 of the order of 50 MeV for spin 0 and has another peak around 27 MeV with similar width for spin 1. The results are in line with those obtained using different methods but implementing chiral dynamics. The simplicity of the approach allows one to see the important ingredients responsible for the results. In partic…
Chiral loops and VMD in the V -> P P gamma decays
We evaluate radiative decays of rho and omega going to two neutral mesons, pi(0)pi(0) and pi(0)eta. We use the sequential vector decay mechanisms in addition to chiral loops and rho-omega mixing. The chiral loops are obtained using elements of UchiPT successfully applied in the study of meson-meson interactions up to 1.2 GeV. The chiral loops are found very important in the case of the rho --> pi(0)pi(0)gamma decay and small in the other cases. A good agreement with present measurements of rho --> pi(0)pi(0)gamma and omega --> pi(0)pi(0)gamma is obtained and predictions are made for the other decays where the rates obtained are rather small.
Meson exchange in the weak decay of Lambda hypernuclei and the Gamma(n)/Gamma(p) ratio
We take an approach to the Lambda non-mesonic weak decay in nuclei based on the exchange of mesons. The one pion and one kaon exchange are considered, together with the exchange of two pions, either correlated, leading to an important scalar-isoscalar exchange (sigma-like exchange), or uncorrelated (box diagrams). Extra effects of omega exchange in the scalar-isoscalar channel are also considered. Constraints of chiral dynamics are used to generate these exchanges. A drastic reduction of the OPE results for the Gamma_n/Gamma_p ratio is obtained and the new results are compatible with all present experiments within errors. The absolute rates obtained for different nuclei are also in good agr…
$\Lambda(1520)$ and $\Sigma(1385)$ in the nuclear medium
Recent studies of the $\Lambda(1520)$ resonance within chiral unitary theory with coupled channels find the resonance as a dynamically generated state from the interaction of the decuplet of baryons and the octet of mesons, essentially a quasibound state of $\pi \Sigma^*(1385)$ in this case, although the coupling of the $\Lambda(1520)$ to the $\bar{K}N$ and $\pi \Sigma$ makes this picture only approximate. The $\pi \Sigma^*(1385)$ decay channel of the $\Lambda(1520)$ is forbidden in free space for the nominal mass of the $\Sigma^*(1385)$, but the coupling of the $\pi$ to $ph$ components in the nuclear medium opens new decay channels of the $\Lambda(1520)$ in the nucleus and produces a much …
Isoscalar roper(N*1440) excitation in the pp -> pp pi 0 reaction close to threshold
A new mechanism for the pp --> pp pi0 reaction close to threshold is suggested coming from the isoscalar excitation of the Roper and its decay into N(pi pi)S-wave, with one of the pi0 emitted and the other one reabsorbed on the second nucleon. The mechanism can lead to important interference with other mechanisms and, together with experiment, serves to exclude large ranges of the 2pi N* decay parameters allowed by the N* partial decay widths.
Reanalysis of the e(+)e(-) -> (D*(D*)over-bar)(+/-)pi(-/+) reaction and the claim for the Z(c)(4025) resonance
In this paper we study the reaction e(+)e(-) -> (D*(D*) over bar (+/-)pi(-/+) in which the BESIII collaboration has claimed the existence of a 1(+) resonance, named Z(c)(4025), in the (D*(D*) over bar invariant mass spectrum with a mass around 4026 MeV and width close to 26 MeV. We determine the (D*(D*) over bar invariant mass distribution and find that although the explanation considered by the BESIII collaboration is plausible, there are others which are equally possible, like a 2(+) resonance or a bound state. Even more, we find that the data can be explained without the existence of a resonance/bound state. In view of the different possible interpretations found for the BESIII data, we …
The DN, pi Sigma(c) interaction in finite volume and the Lambda(c)(2595) resonance
In this work the interaction of the coupled channels DN and pi Sigma(c) in an SU(4) extrapolation of the chiral unitary theory, where the Lambda(c)(2595) resonance appears as dynamically generated from that interaction, is extended to produce results in finite volume. Energy levels in the finite box are evaluated and, assuming that they would correspond to lattice results, the inverse problem of determining the phase shifts in the infinite volume from the lattice results is solved. We observe that it is possible to obtain accurate pi Sigma(c) phase shifts and the position of the Lambda(c)(2595) resonance, but it requires the explicit consideration of the two coupled channels. We also observ…
The gamma d -> K(+)K(-)np reaction and an alternative explanation for the "Theta(+)(1540) pentaquark" peak
We present a calculation of the gamma d -> K(+)K(-)np reaction with the aim of seeing whether the experimental peak observed in the K(+)n invariant mass around 1526 MeV, from where evidence for the existence of the Theta(+) has been claimed, can be obtained without this resonance as a consequence of the particular dynamics of the process and the cuts applied in the experimental setup. We find that a combination of facts leads indeed to a peak around 1530 MeV for the invariant mass of K(+)n without the need to invoke any new resonance around this energy. This, together with statistical fluctuations that we prove to be large with the statistics of the experiment, is likely to produce the narr…
Predictions for the Lambda(b) -> J/psi Lambda (1405) decay
We calculate the shape of the pi Sigma and (K) over bar N invariant mass distributions in the Lambda(b) -> J/psi pi Sigma and Lambda(b) -> J/psi (K) over bar N decays that are dominated by the Lambda (1405) resonance. The weak interaction part is the same for both processes and the hadronization into the different meson-baryon channels in the final state is given by symmetry arguments. The most important feature is the implementation of the meson-baryon final-state interaction using two chiral unitary models from different theoretical groups. Both approaches give a good description of antikaon-nucleon scattering data, the complex energy shift in kaonic hydrogen and the line shapes of pi Sig…
The sigma K coupling in the chiral unitary approach and the isoscalar (K)over-barN , (K)over-barA interaction
We evaluate the 'σ' exchange contribution to the K¯N→K¯N scattering within a chiral unitary approach. We show that the chiral transition potentials for ππ→KK¯ in the t-channel lead to a 'σ' contribution that vanishes in the K¯ forward direction and, hence, would produce a null 'σ' exchange contribution to the K− optical potential in nuclear matter in a simple impulse approximation. This is a consequence of the fact that the leading order chiral Lagrangian gives an I=0 ππ→KK¯ amplitude proportional to the squared momentum transfer, q2. This finding poses questions on the meaning or the origin of 'σ' exchange potentials used in relativistic mean field approaches to the K− nuclear selfenergy. …
Pion and Kaon Vector Form Factors: a Chiral Unitary Approach
The pion and kaon coupled-channel vector form factors are described by making use of the resonance chiral Lagrangian results together with a suitable unitarization method in order to take care of the final state interactions. A very good reproduction of experimental data is accomplished for the vector form factors up to s√≤1.2 GeV and for the ππ P-wave phase shifts up to s√≤1.5 GeV.
Transition form factors of the N(*()1535) as a dynamically generated resonance
We discuss how electromagnetic properties provide useful tests of the nature of resonances, and we study these properties for the N*(1535) which appears dynamically generated from the strong interaction of mesons and baryons. Within this coupled channel chiral unitary approach, we evaluate the A_1/2 and S_1/2 helicity amplitudes as a function of Q^2 for the electromagnetic N*(1535) to gamma* N transition. Within the same formalism we evaluate the cross section for the reactions gamma N to eta N. We find a fair agreement for the absolute values of the transition amplitudes, as well as for the Q^2 dependence of the amplitudes, within theoretical and experimental uncertainties discussed in the…
Testing the molecular nature of D-s0*(2317) and D-0*(2400) in semileptonic B-s and B decays
We study the semileptonic B-s and B decays into the D-s0*(2317) and D-0*(2400) resonances, respectively. With the help of a chiral unitarity model in coupled channels we compute the ratio of the decay widths of both processes. Using current values of the width for the (B) over bar (0) -> D-0*(2400)(+)(v) over bar (l)l(-) we make predictions for the rate of the (B) over bar (0)(s) -> D-s0*(2317)(+)(v) over bar (l)l(-) decay and for the DK invariant mass distribution in the (B) over bar (0)(s) -> DK (v) over bar (l)l(-) decay.
Radiative decays of the Y(3940), Z(3930) and the X(4160) as dynamically generated resonances
We study the radiative decay properties of the charmonium-like X, Y and Z mesons generated dynamically from vector meson-vector meson interaction in the framework of a unitarized hidden-gauge formalism. In the present work we calculate the one- and two-photon decay widths of the hidden-charm Y(3940), Z(3930) (or X(3915)) and X(4160) mesons in the framework of the vector meson dominance formalism. We obtain good agreement with experiment in case of the two photon width of the X(3915) which we associate with the $2^+$ resonance that we find at 3922 MeV.
Mixing of pseudoscalar-baryon and vector-baryon in the J(P)=1/2(-) sector and the N* (1535) and N* (1650) resonances
We study the meson-baryon interaction with J(P) = 1/2 using the hidden-gauge Lagrangians and mixing pseudoscalar meson-baryon with the vector meson-baryon states in a coupled channels scheme with pi N, eta N, K Lambda, K Sigma, rho N, and pi Delta (d wave). We fit the subtraction constants of each channel to the S-11 partial wave amplitude of the pi N scattering data extracted from the partial wave analysis of the George Washington group. We find two poles that we associate to the N*(1535) and the N*(1650) resonances, with negative subtraction constants of natural size, and compare the results with empirical determinations of these pole positions. We calculate the branching ratios for the d…
Chiral symmetry in the KḰ and kn systems
In this talk we present teh results of recent developments in the aplication of Chiral perturbation theory to the KḰ system and to de K+N →KNπ reaction close to threshosd. In the first case, we study the decay channels of the a0 and f0 mesons assumed to be made largely from KḰ. In the second case comparison is made with the present data. A qualitative agreement with experiment is both in found cases. Oset Baguena, Eulogio, Eulogio.Oset@ific.uv.es, Nieves Pamplona, Juan Miguel, Juan.M.Nieves@ific.uv.es
(K)over-bar* mesons in dense matter
We study the properties of (K) over bar* mesons in nuclear matter using a unitary approach in coupled channels within the framework of the local hidden gauge formalism and incorporating the (K) over bar pi decay channel in matter. The in-medium (K) over bar *N interaction accounts for Pauli blocking effects and incorporates the (K) over bar* self-energy in a self-consistent manner. We also obtain the (K) over bar* (off-shell) spectral function and analyze its behavior at finite density and momentum. At a normal nuclear matter density, the (K) over bar* meson feels a moderately attractive potential, while the (K) over bar* width becomes five times larger than in free space. We estimate the t…
Composite nature of the Lambda (1520) resonance
Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the Lambda (1520) resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-wave pi Sigma* and K Xi* and the d-wave (K) over bar N and pi Sigma channels, applying the techniques of the chiral unitary approach. We obtain the result that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only 15% weight of other kinds of c…
The role of the Lambda(1405) in the pp -> pK(+)Lambda(1405) reaction
We report a theoretical study of the pp -> pK(+)Λ(1405) reaction, which was recently investigated at COSY-Jülich by using a 3.65 GeV/c circulating proton beam incident on an internal hydrogen target. The reaction is driven by single-kaon exchange, single-pion exchange, and single-rho exchange terms which have very different shapes due to the two-pole structure of the Λ(1405) and the presence of background terms. The shape for the sum of the three contributions, as well as the total cross-section, are consistent with present data within experimental and theoretical uncertainties, using reasonable form factors for the meson-baryon vertices.
eta '-Nucleus optical potential and possible eta ' bound states
Starting from a recent model of the eta'N interaction, we evaluate the eta'-nucleus optical potential, including the contribution of lowest order in density, t rho/2m(eta'), together with the second-order terms accounting for eta' absorption by two nucleons. We also calculate the formation cross section of the eta' bound states from (pi(+), p) reactions on nuclei. The eta'-nucleus potential suffers from uncertainties tied to the poorly known eta'N interaction, which can be partially constrained by the experimental modulus of the eta'N scattering length and/or the recently measured transparency ratios in eta' nuclear photoproduction. Assuming an attractive interaction and taking the claimed …
Two pion electroproduction
We have extended a model for the γN→ππN reaction to virtual photons and selected the diagrams which have a Δ in the final state. The agreement found with the γvp→Δ0π+ and γvp→Δ++π− reactions is good. The sensitivity of the results to NΔ transition form factors is also studied. The present reaction, selecting a particular final state, is an extra test for models of the γvN→ππN amplitude.
Dynamically generated N* and Lambda* resonances in the hidden charm sector around 4.3 GeV
The interactions of $\bar{D}\Sigma_{c}$-$\bar D\Lambda_c$, $\bar{D}^{*}\Sigma_{c}$-$\bar D^*\Lambda_c$, and related strangeness channels, are studied within the framework of the coupled channel unitary approach with the local hidden gauge formalism. A series of meson-baryon dynamically generated relatively narrow $N^*$ and $\Lambda^*$ resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted resonances in $\bar{p} p $ collisions for PANDA at the forthcoming FAIR facility.
Delta rho pi Interaction Leading to N* and Delta* Resonances
We have performed a calculation for the three body Δρπ system by using the fixed center approximation to Faddeev equations, taking the interaction between Δ and ρ, Δ andπ, and ρ and π from the chiral unitary approach. We find several peaks in the modulus squared of the three-body scattering amplitude, indicating the existence of resonances, which can be associated to known I=1/2,3/2 and JP=1/2+,3/2+ and 5/2+ baryon states.
A model for pi Delta electroproduction on the proton
We have extended a model for the γN→ππN reaction to virtual photons and selected the diagrams which have a Δ in the final state. With this model we have evaluated cross sections for the virtual photon cross section as a function of Q2 for different energies. The agreement found with the γvp→Δ0π+ and γvp→Δ++π− reactions is good. The sensitivity of the results to NΔ transition form factors is also studied. The present reaction, selecting a particular final state, is an extra test for models of the γvN→ππN amplitude. The experimental measurement of the different isospin channels for this reaction are encouraged as a means to unravel the dynamics of the two pions photoproduction processes.
X(2175) as a resonant state of the phi K(K)overbar system
We perform a Faddeev calculation for the three mesons system, ϕKK¯, taking the interaction between two pseudoscalar mesons and between a vector and a pseudoscalar meson from the chiral unitary approach which generates dynamically the low lying scalar mesons in the first case and the low lying axial vector mesons in the second. We obtain a neat resonance peak around a total mass of 2150 MeV and an invariant mass for the KK¯ system around 970 MeV, very close to the f0(980) mass. The state appears in I=0 and qualifies as a ϕf0(980) resonance. No state is seen in I=1. This finding provides a natural explanation for the recent state found at BABAR and BES, the X(2175), which decays into ϕf0(980).
Projectile Delta and target Roper excitation in the p(d,d ') X reaction
In this paper we compare a model that contains the mechanisms of Δ excitation in the projectile and Roper excitation in the target with experimental data from two (d, d') experiments on a proton target. The agreement of the theory with the experiment is fair for the data taken at T_d = 2.3 GeV. The Δ excitation in the projectile is predicted close to the observed energy with the correct width. The theory, however, underpredicts by about 40% the cross sections measured at T_d = 1.6 GeV at angles where the cross section has fallen by about two orders of magnitude. The analysis done here allows to extract an approximate strength for the excitation of the Roper [N^*(1440)] excitation and a qual…
Production of pionic atoms with the ( pi -, pi +) reaction
We have evaluated the cross section for the π-+A→π++(Aπ-) reaction in heavy nuclei producing deeply bound π- atom states still unobserved. The cross sections found, although in the measurable range, are only a small fraction of the background from the inclusive (π-,π+) reaction, which makes this experiment not very suited for the investigation of these elusive pionic states.
Pion double charge exchange reactions leading to deeply bound double pionic atoms
We study theoretically pion double charge exchange reactions leading to double pionic atoms. The reaction cross-sections with two pions in the deeper bound pionic orbits in 208Pb are calculated with realistic pionic atom wave functions and distortion effects. The cross-sections are found to be d2σ/dEdΩ~10−3−10−4 µb/srMeV, which are only a small fraction of the double charge exchange background.
Prediction of a Z(c)(4000) state and relationship with the claimed Z(c)(4025)
After discussing the OZI suppression of one light meson exchange in the interaction of with isospin I = 1 , we study the contribution of the two-pion exchange to the interaction and the exchange of heavy vectors, J/psi for diagonal transitions and D-* for transitions of to J/psi rho. We find these latter mechanisms to be weak, but enough to barely bind the system in J = 2 with a mass around 4000 MeV, while the effect of the two-pion exchange is a net attraction, though weaker than that from heavy-vector exchange. We discuss this state and try to relate it to the Z (c) (4025) state, above the threshold, claimed in an experiment at BES from an enhancement of the distribution close to threshol…
(K)over-bar N N absorption within the framework of the fixed-center approximation to Faddeev equations
We present a method to evaluate the (K) over bar absorption width in the bound (K) over bar N N system. Most calculations of this system ignore this channel and only consider the (K) over bar N -> pi Sigma conversion. Other works make a qualitative calculation using perturbative methods. Since the (1405) resonance is playing a role in the process, the same resonance is changed by the presence of the absorption channels andwe find that a full nonperturbative calculation is called for, which we present here. We employ the fixed center approximation to Faddeev equations to account for (K) over bar rescattering on the (NN) cluster and we find that the width of the states found previously for S …
Scattering of unstable particles in a finite volume: the case of pi rho scattering and the a1(1260) resonance
We present a way to evaluate the scattering of unstable particles quantized in a finite volume with the aim of extracting physical observables for infinite volume from lattice data. We illustrate the method with the $\pi\rho$ scattering which generates dynamically the axial-vector $a_1(1260)$ resonance. Energy levels in a finite box are evaluated both considering the $\rho$ as a stable and unstable resonance and we find significant differences between both cases. We discuss how to solve the problem to get the physical scattering amplitudes in the infinite volume, and hence phase shifts, from possible lattice results on energy levels quantized inside a finite box.
Y(3940), Z(3930), and the X(4160) as dynamically generated resonances from the vector-vector interaction
We study the vector-vector interaction within the framework of the hidden gauge formalism for the channels with quantum numbers charm C=0 and strangeness S=0 in the energy region around 4000 MeV. By looking for poles in the complex plane we find three resonances that could be identified by the mass, width, and quantum numbers with the Y(3940), Z(3940), and X(4160), these poles appear with isospin I=0 and J(PC)=0(++), 2(++) and 2(++), respectively. Whereas the Y(3940) and Z(3940) are coupled more strongly to (DD*)-D-*, the X(4160) is basically a (DsDs*)-D-* molecular state. Another two extra resonances appear in our approach with I=0, 1 and J(PC)=1(+-), 2(++) which are not found in the PDG w…
Isoscalar S-wave π–π interaction in the nuclear medium
The s-wave isoscalar π π scattering amplitude in a nuclear medium has been evaluated using a non-perturbative unitary coupled channels method and the standard chiral Lagrangians. The method is successful describing the π π properties in vacuum, in the scalar-isoscalar channel up to 1.2 GeV giving rise to poles in the T matrix for the ƒ0(980) and the σ. The extension of the method to the nuclear medium implies the renormalization of the pions in the medium and also the introduction of interaction terms related to contact terms in the πN → ππN reaction. Vicente Vacas, Manuel Jose, Manuel.J.Vicente@ific.uv.es ; Oset Baguena , Eulogio, Eulogio.Oset@ific.uv.es
Weak Decay of Lambda Hypernuclei
We review recent developments concerning the weak decay of Lambda hypernuclei. New studies covering the mesonic decay channel as well as recent models for the non-mesonic one are discussed and compared with experimental data. The puzzle of the neutron- to proton-induced decay ratio, Gamma_n/Gamma_p, is addressed in connection to the two-nucleon induced decay channel and proposals for more efficient experimental analyses of this ratio are made.
Production of pionic atoms with the (e, E-prime) reaction
We study the reaction e+A→e+(Aπ-) with the π- bound in the nucleus as a means of producing deeply bound pionic states of heavy nuclei so far unobserved. Although the cross sections found can be rather large, they are overwhelmed by the background from the inclusive (e,e) reaction, which makes the reaction not well suited for the investigation of these pionic states. However, the ratio of signal to background is much bigger in light nuclei and the reaction could be used to observe pionic states of unstable light nuclei, provided the resolution in the beam and detectors is of the order of the width of the pionic state.
rho-rho-N and rho-rho-Delta molecules with $J^P=5/2^{+}$ and $J^P=7/2^{+}$
The rho-rho-N and rho-rho-Delta three-body systems have been studied within the framework of the fixed center approximation of Faddeev equation. The rho-rho interaction in isospin I=0, spin S=2 is strongly attractive, and so are the N-rho, Delta-rho interactions. This leads to bound states of both rho-rho-N and rho-rho-Delta. We find peaks of the modulus squared of the scattering matrix around 2227 MeV for rho-rho-N, and 2372 MeV for rho-rho-Delta. Yet, the strength of the peak for the rho-rho-N amplitude is much smaller than for rho-rho-Delta, weakening the case for a rho-rho-N bound state, or a dominant rho-rho-N component. A discussion is made on how these states can be searched for in p…
Coupling of (K)over-bar(*)N to the Lambda(1520)
We study the coupling of the Λ(1520)≡Λ* resonance to the K* vector meson and nucleon. This coupling is not directly measured from the resonance decay, but is expected to be important in hyperon production reactions, in particular for the exotic Θ+ production. We compute the coupling in two different schemes, one in the chiral unitary model where the Λ* is dominated by the quasibound state of mesons and baryons, and the other in the quark model where the resonance is a p-wave excitation in the three valence quarks. Although it is possible to construct both models such that they reproduce the KN and πΣ decays, there is a significant difference between the Λ*K*N couplings in the two models. In…
Prediction of an I=1 D(D)over-bar* state and relationship to the claimed Z(c)(3900), Z(c)(3885)
We study here the interaction of D (D) over bar* in the isospin I = 1 channel in light of recent theoretical advances that allow us to combine elements of the local hidden gauge approach with heavy quark spin symmetry. We find that the exchange of light q (q) over bar is Okubo-Zweig-Iizuka (OZI) suppressed and thus we concentrate on the exchange of heavy vectors and of two pion exchange. The latter is found to be small compared to the exchange of heavy vectors, which then determines the strength of the interaction. A barely D (D) over bar* bound state decaying into eta(c)rho and pi J/psi is found. At the same time we reanalyze the data of the BESIII experiment on e(+)e(-) -> pi(+/-)(D (D) o…
The K K bar π decay of the f1 (1285) and its nature as a K* K bar - cc molecule
We investigate the decay of f1 (1285) → πK K bar with the assumption that the f1 (1285) is dynamically generated from the K* K bar - cc interaction. In addition to the tree level diagrams that proceed via f1 (1285) →K* K bar - cc → πK K bar , we take into account also the final state interactions of K K bar → K K bar and πK → πK. The partial decay width and mass distributions of f1 (1285) → πK K bar are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions …
phi K+K- production in electron-positron annihilation
In this work we study the e(+)e(-)->phi K+K- reaction. The leading order electromagnetic contributions to this process involve the gamma(*)phi K+K- vertex function with a highly virtual photon. We calculate this function at low energies using R chi PT supplemented with the anomalous term for the (VVP)-P-' interactions. Tree-level contributions involve the kaon form factors and the (KK)-K-* transition form factors. We improve this result, valid for low photon virtualities, replacing the lowest order terms in the kaon form factors and (KK)-K-* transition form factors by the form factors as obtained in U chi PT in the former case and the ones extracted from recent data on e(+)e(-)-> KK* in the…
S-wave pion nucleon scattering lengths from $\pi N$, pionic hydrogen and deuteron data
The isoscalar and isovector scattering lengths (b_0,b_1) are determined using a unitarized coupled channel approach based on chiral Lagrangians. Using experimental values of pionic hydrogen and deuterium as well as low energy pi N scattering data, the free parameters of the model are calculated. Isospin violation is incorporated to a certain extent by working with physical particle masses. For the deuterium scattering length a_{pi-d} new significant corrections concerning real and imaginary parts are evaluated, putting new constraints from pi-d scattering on the values of (b_0,b_1). In particular, dispersion corrections, the influence of the Delta(1232) resonance, crossed terms and multiple…
Renormalization of the f(0)(980) and a(0)(980) scalar resonances in a nuclear medium
The meson-meson interaction in the scalar sector in the presence of a nuclear medium is studied with particular attention to the change of the properties of the f(0)(980) and a(0)(980) resonances. By using a chiral unitary approach which generates the f(0) and a(0) resonances and reproduces their free properties, we find that the position of the resonances in the medium is barely changed but their widths are considerably broadened. New many body corrections generating from higher orders in the chiral Lagrangian plus the contribution from N*h excitations, not considered before in connection with the pi pi interaction in the nuclear medium, are also investigated.
pi pi interaction in the rho channel in finite volume
The aim of this paper is to investigate an efficient strategy that allows one to obtain pi pi phase shifts and rho meson properties from QCD lattice data with high precision. For this purpose we evaluate the levels of the pi pi system in the rho channel in finite volume using chiral unitary theory. We investigate the dependence on the pi mass and compare this with other approaches which use QCD lattice calculations and effective theories. We also illustrate the errors induced by using the conventional Luscher approach instead of a more accurate one that was recently developed that takes into account exactly the relativistic two-meson propagators. Finally, we make use of this latter approach…
Limits to the fixed center approximation to Faddeev equations: The case of the phi(2170)
The Fixed Center Approximation to the Faddeev equations (FCA) has been used lately with success in the study of bound systems of three hadrons. It is also important to set the limits of the approach in those problems to prevent proliferation of inaccurate predictions. In this paper we study the case of the ϕ(2170), which has been described by means of Faddeev equations as a resonant state of ϕ and KK¯, and show the problems derived from the use of the FCA in its study. At the same time we also expose the limitations of an alternative approach recently proposed.
(B)over-bar(0) decay into D-0 and f(0)(500), f(0)(980), a(0)(980), rho and (B)over-bar(s)(0) decay into D-0 and kappa(800), K*(0)
We make predictions for ratios of branching fractions of (B) over bar (0) decays into D-0 and the scalar mesons f(0)(500), f(0)(980), a(0)(980), plus (B) over bar (0)(s) decay into D-0 and kappa(800). We also compare the pi(+)pi(-) production in the scalar channel with that observed in the rho channel and make predictions for the (B) over bar (0)(s) decay into D-0 and K*(892), comparing the strength of this channel with that of kappa(800) production. The work is based on results of the chiral unitary approach where the scalar resonances are generated from the pseudoscalar-pseudoscalar interaction. Up to an arbitrary normalization, the mass distributions and rates for decays into the scalar …
The properties of (K)over-bar in the nuclear medium
The self-energy of the K^- meson in nuclear matter is calculated in a self-consistent microscopic approach, using a \bar{K}N interaction obtained from the lowest-order meson-baryon chiral Lagrangian. The effective \bar{K}N interaction in the medium is derived by solving the coupled-channel Bethe-Salpeter equation including Pauli blocking on the nucleons, mean-field binding potentials for the baryons and the self-energy of the \pi and \bar{K} mesons. The incorporation of the self-consistent {\bar K} self-energy in the description, in addition to the Pauli blocking effects, yields a weaker attractive in-medium {\bar K}N interaction and a \Lambda(1405) which dissolves faster with increasing ma…
Non-perturbative chiral approach to s-wave (K)over-barN interactions
The s-wave meson-nucleon interaction in the S=−1 sector is studied by means of coupled-channel Lippmann Schwinger equations, using the lowest order chiral Lagrangian and a cut off to regularize the loop integrals. The method reproduces succesfully the Λ(1405) resonance and the K−p→K−p,K¯0n,π0Λ,π0Σ,π+Σ−,π−Σ+ cross sections at low energies. The inclusion of the ηΛ,ηΣ0 channels in the coupled system is found very important and allows a solution in terms of only the lowest order Lagrangian.
A model for the γN → ππN reaction
We have studied the γN → ππN reaction using a model wich includes N, Δ(1232), N*(1440) and N*(1520) intermediate baryonic states and the ρ-meson as a intermediate ππ resonance. The model reproduces fairly well experimental cross sections below Eγ=800 MeV and invariant-mass distributions even at higher energies. One of the interesting findings of study is what the γN → N*(1520) → Δπ process is very important and interferes strongly with the dominant Δ-Kroll-Ruderman term to produce the experimental peak of the kross section. Oset Baguena, Eulogio, Eulogio.Oset@ific.uv.es
Unitary coupled channel analysis of the Lambda(1520) resonance
We study the $\Lambda(1520)$ resonance in a coupled channel approach involving the $\pi\Sigma(1385)$, $K\Xi(1530)$, $\bar{K}N$ and $\pi\Sigma$ channels. Implementing unitarity in coupled channels, we make an analysis of the relative importance of the different mechanisms which contribute to the dynamical structure of this resonance. From experimental information on some partial wave amplitudes and constraints imposed by unitarity, we get a comprehensive description of the amplitudes and hence the couplings to the different channels. We test these amplitudes in different reactions like $K^-p\to\Lambda\pi\pi$, $\gamma p\to K^+K^-p$, $\gamma p\to K^+\pi^0\pi^0\Lambda$ and $\pi^- p\to K^0 K^-p$…
Lambda(1405) and (Lambda)over-bar(1405) in J/psi four-body decays
We study the structure of the baryon resonances Λ(1405) and Λ¯(1405) in J/ψ four body decays J/ψ→ΣΣ¯ππ in the framework of a coupled channel chiral unitary approach. With still sufficient freedom for model parameters, the Λ(1405) and Λ¯(1405) resonances are generated by simultaneously taking the meson baryon and meson anti-baryon final state interactions into account. The πΣ (πΣ¯) invariant mass distributions peak around 1410 MeV, which favors the assertion that the Λ(1405) (Λ¯(1405)) is a superposition of the two Λ(1405) (Λ¯(1405)) states which dominantly couple to K¯N (KN¯) and πΣ (πΣ¯), respectively. We also calculate the amplitude for isospin I=1 which gives hints on a possible I=1 bary…
Double-delta production in the gamma-d-]pn-pi(+)pi(-) reaction
We have studied the gamma d ---> Delta++ Delta- reaction which requires the collaboration of the two nucleons in deuteron. By means of a model previously developed for the gamma p ----> p pi+ pi- reaction, the two body exchange currents leading to double delta creation are derived. A fair agreement is obtained with a recent experiment, but more precise measurements and the extension to higher photon energies look advisable in order to see the limits of the present theoretical approach
Two-photon and one photon-one vector meson decay widths of the $f_0(1370)$, $f_2(1270)$, $f_0(1710)$, $f'_2(1525)$, and $K^*_2(1430)$
We calculate the radiative decay widths, two-photon ($\gamma\gamma$) and one photon-one vector meson ($V\gamma$), of the dynamically generated resonances from vector meson-vector meson interaction in a unitary approach based on the hidden-gauge Lagrangians. In the present paper we consider the following dynamically generated resonances: $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^*_2(1430)$, two strangeness=0 and isospin=1 states, and two strangeness=1 and isospin=1/2 states. For the $f_0(1370)$ and $f_2(1270)$ we reproduce the previous results for the two-photon decay widths and further calculate their one photon-one vector decay widths. For the $f_0(1710)$ and $f_2'(1525)$ the…
Bound states of Theta(+) in nuclei
We study the binding energy and the width of the Theta(+) in nuclei, associated to the KN and K pi N components. The first one leads to negligible contributions while the second one leads to a sizeable attraction, enough to bind the Theta(+) in nuclei. Pauli blocking and binding effects on the KN decay reduce considerably the Theta(+) decay width in nuclei and medium effects associated to the K pi N component also lead to a very small width, as a consequence of which one finds separation between the bound levels considerably larger than the width of the states.
Energy And Width Of A Narrow I=1/2 Dnn Quasibound State
The energies and widths of DNN quasibound states with isospin I = 1/2 are evaluated in two methods, the fixed center approximation to the Faddeev equation and the variational method approach to the effective one-channel Hamiltonian. The DN interactions are constructed so they dynamically generate the Lambda(c)(2595) (I = 0, J(pi) = 1/2(-)) resonance state. We find that the system is bound by about 250 MeV from the DNN threshold, root s similar to 3500 MeV. Its width, including both the mesonic decay and the D absorption, is estimated to be about 20-40 MeV. The I = 0 DN pair in the DNN system is found to form a cluster that is similar to the Lambda(c)(2595).
Theoretical study of the gamma gamma -> meson-meson reaction
We present a unified picture which studies simultaneously the gamma gamma-->pi^+ pi^-, pi^0 pi^0, K^+ K^-, K^0 bar{K}^0, pi^0 eta reactions up to about sqrt(s)=1.4 GeV reproducing the experimental cross sections. The present work implements in an accurate way the final state interactions of the meson-meson system, which is shown to be essential in order to reproduce the data, particularly the L=0 channel. This latter channel is treated here following a recent theoretical work in which the meson-meson amplitudes are well reproduced and the f_0, a_0, sigma resonances show up clearly as poles of the t matrix. The present work, as done in earlier ones, also incorporates elements of chiral symme…
Predictions for the X(YZ) and X(YZ) with X(4160), Y(3940), Z(3930)
We investigate the decay of and with R being the , , resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predict the order of magnitude of the branching ratios which we find of the order of , well within t…
Explanation of the Delta(-)(5/2)(1930) as a rho Delta bound state
19 pags, 8 figs.-- ISI article identifier:000263816400064.-- ArXiv pre-print avaible at:http://arxiv.org/abs/0812.3368
Plausible explanation for the Delta(5/2)+(2000) puzzle
From a Faddeev calculation for the π−(Δρ)N5/2−(1675) system we show the plausible existence of three dynamically generated I(JP)=3/2(5/2+) baryon states below 2.3 GeV whereas only two resonances, Δ5/2+(1905)(∗∗∗∗) and Δ5/2+(2000)(∗∗), are cataloged in the Particle Data Book Review. Our results give theoretical support to data analyses extracting two distinctive resonances, Δ5/2+(∼1740) and Δ5/2+(∼2200), from which the mass of Δ5/2+(2000)(∗∗) is estimated. We propose that these two resonances should be cataloged instead of Δ5/2+(2000). This proposal gets further support from the possible assignment of the other baryon states found in the approach in the I=1/2,3/2 with JP=1/2+,3/2+,5/2+ secto…
Nuclear medium effects on the (K)over-bar* meson
The K¯∗ meson in dense matter is analyzed by means of a unitary approach in coupled channels based on the local hidden gauge formalism. The K¯∗ self-energy and the corresponding K¯∗ spectral function in the nuclear medium are obtained. We observe that the K¯∗ develops a width in matter up to five times bigger than in free space. We also estimate the transparency ratio of the γA→K+K∗−A′ reaction. This ratio is an excellent tool to detect experimentally modifications of the K¯∗ meson in dense matter.
eta ->pi(0)gamma gamma decay within a chiral unitary approach
We improve the calculations of the η⃗ π0γγ decay within the context of meson chiral Lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the a0(980) resonance and fixing the long standing sign ambiguity on its contribution. This also allows us to calculate the loops with one vector meson exchange, thus removing a former source of uncertainty. In addition we ensure the consistency of the approach with other processes, first, by using vector meson dominance couplings normalized to agree with radiative vector meson decays and, second, by checking the consistency of the calculations with the related γγ⃗ π0η reaction. We find an η⃗ π0γγ decay width of 0.…
Inclusive omega photoproduction from nuclei and omega in the nuclear medium
With the aim of extracting information on the shift of the $\omega$ mass in the nuclear medium we analyze data obtained at ELSA from where claims for evidence of a mass shift of the $\omega$ have been made. We develop a Monte Carlo simulation code which takes into account the possible reactions in the experimental set up of $(\gamma ~ A \to \pi^0 \gamma ~X)$ in the vicinity of the $\omega$ production region with subsequent $\omega \to \pi^0 \gamma$ decay. We compare our results with experiment for the distribution of $\pi^0 \gamma$ invariant masses and conclude that the distribution is compatible with an enlarged $\omega$ width of about 90 MeV at nuclear matter density and no shift in the m…
Weak decay of Lambda_c^+ for the study of Lambda(1405) and Lambda(1670)
We study the Lambda_c decay process to pi^+ and the meson-baryon final state for the analysis of Lambda resonances. Considering the Cabibbo-Kobayashi-Maskawa matrix, color suppression, diquark correlation and the kinematical condition, we show that the final meson-baryon state should be in a pure I=0 combination, when the meson-baryon invariant mass is small. Because the I=1 contamination usually makes it difficult to analyze Lambda resonances directly from experiments, the Lambda_c decay is an ideal process to study Lambda resonances. Calculating the final state interaction by chiral unitary approaches, we find that the piSigma invariant mass distributions have the same peak structure in t…
Meson–meson and meson–baryon interactions in a chiral non-perturbative approach
A qualitative account of the meson-meson and meson-baryon interactions using chiral Lagrangians and the inverse amplitude method in coupled channels is done. The method, imposing exact unitarity, proves to be a very useful tool to extend the information contained in the chiral Lagrangians at energies beyond the realm of applicability of chiral perturbation theory. Oset Baguena, Eulogio, Eulogio.Oset@ific.uv.es
The role of vector-baryon channels and resonances in the γp→K0Σ+ and γn→K0Σ0 reactions near the K⁎Λ threshold
AbstractWe have studied the γp→K0Σ+ reaction in the energy region around the K⁎Λ and K⁎Σ thresholds, where the CBELSA/TAPS cross section shows a sudden drop and the differential cross section experiences a transition from a forward-peaked distribution to a flat one. Our coupled-channel model incorporates the dynamics of the vector meson–baryon interaction which is obtained from the hidden gauge formalism. We find that the cross section in this energy region results from a delicate interference between amplitudes having K⁎Λ and K⁎Σ intermediate states. The sharp downfall is dictated by the presence of a nearby N⁎ resonance produced by our model, a feature that we have employed to predict its…
B-0 and B-s(0) decays into J/psi f(0)(980) and J/psi f(0)(500) and the nature of the scalar resonances
We describe the B-0 and B-s(0) decays into J/psi f(0)(500) and J/psi f(0)(980) by taking into account the dominant process for the weak decay of B-0 and B-s(0) into J/psi and a q (q) over bar component. After hadronization of this q (q) over bar component into pairs of pseudoscalar mesons we obtain certain weights for the meson-meson components and allow them to interact among themselves. The final state interaction of the meson-meson components, described in terms of chiral unitary theory, gives rise to the f(0)(980) and f(0)(500) resonances and we can obtain the pi(+)pi(-) invariant mass distributions after the decay of the resonances, which allows us to compare directly to the experiment…
Testing the nature of the Lambda(1520) in the J / psi ---> anti-Lambda K- p and J / psi ---> anti-Lambda pi+ pi- Lambda reactions
We study the reactions J/ψ→Λ¯K−p and J/ψ→Λ¯π+π−Λ with a unitary chiral approach. We predict the ratio of the invariant mass distributions of these two reactions at the Λ(1520) peak position, which is free of the unknown production mechanism and reflects only the properties of the Λ(1520). An experimental measurement of this ratio will provide the couplings of the Λ(1520) to its decay channels, allowing to test the predictions of the chiral unitary approach on this resonance, which appears as dynamically generated in that approach.
rho rho interaction in the hidden gauge formalism and the f(0)(1370) and f(2)(1270) resonances
We have studied the interaction of vectors mesons within the hidden gauge formalism and applied it to the particular case of the ρρ interaction. We find a strong attraction in the isospin, spin channels I,S=0,0 and 0,2, which is enough to bind the ρρ system. We also find that the attraction in the I,S=0,2 channel is much stronger than in the 0,0 case. The states develop a width when the ρ mass distribution is considered, and particularly when the ππ decay channel is turned on. Using a regularization scheme with cut offs of natural size, we obtain results in fair agreement with the mass and the width of the f0(1370) and f2(1270) meson states, providing a natural explanation of why the tensor…
Clues for the existence of two K-1(1270) resonances
The axial-vector meson K1(1270) was studied within the chiral unitary approach, where it was shown that it has a two-pole structure. We reanalyze the high-statistics WA3 experiment K-p-->K-pi+pi-p at 63 GeV, which established the existence of both K1(1270) and K1(1400), and we show that it clearly favors our two-pole interpretation. We also reanalyze the traditional K-matrix interpretation of the WA3 data and find that the good fit of the data obtained there comes from large cancellations of terms of unclear physical interpretation.
Signature of an h(1) state in the J/psi -> eta h(1) -> eta K*(0)(K)over-bar*(0) decay
The BES data on the J/psi -> eta K*(0)(K) over bar*(0) reaction show a clear enhancement in the K*(0)(K) over bar*(0) mass distribution close to the threshold of this channel. Such an enhancement is usually a signature of an L = 0 resonance around threshold, which in this case would correspond to an h1 state with quantum numbers I-G(J(Pc))= 0(-)(1(+-)). A state around 1800 MeV results from the interaction of the K*TC* using the local hidden gauge approach. We show that the peak observed in J/psi -> eta K*(0)(K) over bar*(0) naturally comes from the creation of this h(1) state with mass and width around 1830 MeV and 110 MeV, respectively. A second analysis, model independent, corroborates th…
B-0 And B-S(0) Decays Into J/Psi Plus A Scalar Or Vector Meson
We extend a recent approach to describe the B-0 and B-s(0) decays into J/psi f(0)(500) and J/psi f(0)(980), relating it to the B-0 and B-s(0) decays into J/psi and a vector meson, phi, rho, K*. In addition, the B-0 and B-s(0) decays into J/psi and kappa(800) are evaluated and compared to the K* vector production. The rates obtained are in agreement with the available experiment while predictions are made for the J/psi plus kappa(800) decay.
Chiral unitary approach to the pi N*N*, eta N*N* couplings for the N* (1535) resonance
Using a chiral unitary model in which the negative parity nucleon resonance N∗≡N∗(1535) is generated dynamically by means of the Bethe Salpeter equation with coupled meson baryon channels in the S=0 sector, we have obtained the π0N∗N∗ and ηN∗N∗ couplings. The π0N∗N∗ coupling has smaller strength and the same sign as the π0NN coupling. This rules out the mirror assignment of chiral symmetry where the ground state nucleon N and the negative parity resonance N∗ are envisaged as chiral partners in the baryon sector.
Recent developments in one and two pion production in elementary reactions and few-body systems
In this talk we cover several issues concerning pion production. The first one is the p p ----> p p pi^0 reaction where an alternative explanation based on the off shell extrapolation of the pi N amplitude is offered. A recent model for the gamma N ----> pi pi N reaction is presented and a new kind of exchange current is constructed from it which allows one to address problems like double Delta photoproduction from the deuteron. Finally the (gamma, pi pi) reaction in nuclei is studied and shown to be highly sensitive to the renormalization of the pions in nuclei.
Role of the N*(1535) resonance and the pi(-)p -> KY amplitudes in the OZI forbidden pi N ->phi N reaction
We study the pi N --> phi N reaction close to the phi N threshold within the chiral unitary approach, by combining the pi^- p --> K^+ Sigma^-, pi^- p --> K^0 Sigma^0 and pi^- p --> K^0 Lambda amplitudes with the coupling of the phi to the K components of the final states of these reactions via quantum loops. We obtain a good agreement with experiment when the dominant pi^- p --> K^0 Lambda amplitude is constrained with its experimental cross section. We also evaluate the coupling of the N*(1535) to phi N and find a moderate coupling as a consequence of partial cancellation of the large KY components of the N*(1535). We also show that the N*(1535) pole approximation is too small to reproduce…
X(3872) -> J/psi gamma decay in the D(D)over-bar* molecular picture
From a picture of the X(3872) where the resonance is a bound state of D (D) over bar*- c.c., we evaluate the decay width into the J/psi gamma channel, which is sensitive to the internal structure of this state. For this purpose we evaluate the loops through which the X(3872) decays into its components, and the J/psi and the photon are radiated from these components. We use the local hidden gauge approach extrapolated to SU(4) with a particular SU(4) breaking. The radiative decay involves anomalous couplings, and we obtain acceptable values which are compared to experiments and results of other calculations. Simultaneously, we evaluate the decay rate for the X(3872) into J/psi omega and J/ps…
Role of the N-*(1535) in the J/psi -> pp and J/psi -> p(+)Lambda reactions
We study the J/psi -> p eta p and J/psi -> pK(+)Lambda reactions with a unitary chiral approach. We find that the unitary chiral approach, which generates the N-*(1535) dynamically, can describe the data reasonably well, particularly the ratio of the integrated cross sections. This study provides further support for the unitary chiral description of the N-*(1535). We also discuss some subtle differences between the coupling constants determined from the unitary chiral approach and those determined from phenomenological studies
Radiative decay into $\gamma P$ of the low lying axial-vector mesons
We evaluate the radiative decay into a pseudoscalar meson and a photon of the whole set of the axial-vector mesons dynamically generated from the vector-pseudoscalar meson ($VP$) interaction. We take into account tree level and loop diagrams coming from the axial-vector decay into a vector and a pseudoscalar meson. We find a large span for the values of the radiative widths of the different axial-vector mesons. In particular, we evaluate the radiative decay into $K \gamma$ of the two $K_1(1270)$ states, recently claimed theoretically, and discuss the experimental values quoted so far on the assumption of only one state.
Baryon states with open beauty in the extended local hidden gauge approach
In this paper we examine the interaction of \bar B N, \bar B \Delta, \bar B^* N and \bar B^* \Delta states, together with their coupled channels, using a mapping from the light meson sector. The assumption that the heavy quarks act as spectators at the quark level automatically leads us to the results of the heavy quark spin symmetry for pion exchange and reproduces the results of the Weinberg Tomozawa term, coming from light vector exchanges in the extended local hidden gauge approach. With this dynamics we look for states dynamically generated from the interaction and find two states with nearly zero width, which we associate to the \Lambda_b(5912) and \Lambda_b(5920) states. The states c…
Photoproduction of $K^*$ for the study of $\Lambda(1405)$
The photo-induced $K^*$ vector meson production is investigated for the study of the $\Lambda(1405)$ resonance. This reaction is particularly suited to the isolation of the second pole in the $\Lambda(1405)$ region which couples dominantly to the $\bar K N$ channel. We obtain the mass distribution of the $\Lambda(1405)$ which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the $\pi^- p \to K^0 \pi \Sigma$ which favours the first pole, this detailed study will reveal a novel structure of the $\Lambda(1405)$ state.
Light scalar mesons in J/psi -> N(N)over-bar meson meson decays in a chiral unitary approach
We study the four-body decays J/psi --> N(N) over bar meson meson using a chiral unitary approach to account for the meson meson final state interaction (FSI). The calculation of the J/psi --> N(N) over bar pi(+)pi(-) process properly reproduces the experimental data after taking the FSI of mesons and the contribution of intermediate rho meson into account. The isoscalar resonances sigma,f(0)(980) and the isovector resonance a(0)(980) are generated through the FSI of the mesons in the channels J/psi --> N(N) over bar pi(0)pi(0) and J/psi --> N(N) over bar pi(0)eta, respectively. We also calculate the two mesons invariant mass distribution and the partial decay width of J/psi --> N(N) over b…
Test of h(1)(1830) made of K*K* with the eta(c) ->phi K*K* decay
We present a new reaction, complementary to from which an h (1) resonance with mass around 1830 MeV was reported from a BESIII experiment. The new reaction is , or . Using the information from the analysis of , we find that the invariant mass distribution for those two Iu decays exhibits a clear peak around 1830 MeV perfectly distinguishable from what one obtains with pure phase space. We suggest the implementation of these reactions to assert the existence of this elusive resonance which, by its nature as a vector-vector molecule with 0(-)(1(+-)) quantum numbers, only couples to the channel.
Critical view on the deeply bound K- pp system
We briefly review the situation around the claimed deeply bound K^- states in different recent experiments and concentrate particularly on the state K^- pp advocated by the FINUDA collaboration in nuclear K^- absorption. We perform a theoretical simulation of the process and show that the peak in the Lambda p spectrum that was interpreted as a deep K^- pp bound state corresponds mostly to the process K^- p p --> Lambda p followed by final state interactions of the produced particles with the daughter nucleus.
Study of B* and B** interactions in I=1 and relationship to the Z(b)(10610), Z(b)(10650) states
We use the local hidden gauge approach in order to study the B (B) over bar* and B*(B) over bar* interactions for isospin I = 1. We show that both interactions via one light meson exchange are not allowed by the Okubo-ZweigIizuka rule and, for that reason, we calculate the contributions due to the exchange of two pions, interacting and noninteracting among themselves, and also due to the heavy vector mesons. Then, to compare all these contributions, we use the potential related to the heavy vector exchange as an effective potential corrected by a factor which takes into account the contribution of the other light meson exchanges. In order to look for poles, this effective potential is used …
The pp -> p Lambda K(+) and pp -> p Sigma(0)K(+) reactions with chiral dynamics
We report on a theoretical study of the pp->p Lambda K+ and pp->p Sigma0 K+ reactions near threshold using a chiral dynamical approach. The production process is described by single-pion and single-kaon exchange. The final state interactions of nucleon-hyperon, K-hyperon and K-nucleon systems are also taken into account. We show that our model leads to a fair description of the experimental data on the total cross section of the pp->p Lambda K+ and pp->p Sigma0 K+ reactions. We find that the experimental observed strong suppression of Sigma0 production compared to Lambda production at the same excess energy can be explained. However, ignorance of phases between some amplitudes does not allo…
gamma gamma decay of the f(0)(1370) and f(2)(1270) resonances in the hidden gauge formalism
Using recent results obtained within the hidden gauge formalism for vector mesons, in which the f0(1370) and f2(1270) resonances are dynamically generated resonances from the ρρ interaction, we evaluate the radiative decay of these resonances into γγ. We obtain results for the width in good agreement with the experimental data for the f2(1270) state and a width about a factor five smaller for the f0(1370) resonance, which would agree with preliminary results from the Belle collaboration, hinting at an order of magnitude smaller width for this resonance than for the f2(1270).