0000000001166821
AUTHOR
K. P. Khemchandani
Exploring the D* rho system within QCD sum rules
We present a study of the D* rho system made by using the method of QCD sum rules to determine the mass of possible resonances generated in the same system. Using isospin and spin projectors, we investigate the different configurations and obtain evidences for three D* mesons with isospin I = 1/2, spin S = 0, 1, 2 and with masses 2500 +/- 67, 2523 +/- 60, and 2439 +/- 119 MeV, respectively. The last state can be associated with D-2*(2460) ( spin 2) listed by the Particle Data Group, while one of the first two might be related to D* (2640), with unknown spin parity. In the case of I = 3/2 we also find evidences of three states with spin 0, 1, and 2, respectively, with masses 2467 +/- 82, 242…
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…
Solution to Faddeev equations with two-body experimental amplitudes as input and application toJP=1/2+,S=0baryon resonances
We solve the Faddeev equations for the two meson-one baryon system $\ensuremath{\pi}\ensuremath{\pi}N$ and coupled channels using the experimental two-body $t$ matrices for the $\ensuremath{\pi}N$ interaction as input and unitary chiral dynamics to describe the interaction between the rest of coupled channels. In addition to the ${N}^{*}(1710)$ obtained before with the $\ensuremath{\pi}\ensuremath{\pi}N$ channel, we obtain, for ${J}^{\ensuremath{\pi}}=1/{2}^{+}$ and total isospin of the three-body system $I=1/2$, a resonance peak whose mass is around 2080 MeV and width 54 MeV, while for $I=3/2$ we find a peak around 2126 with 42 MeV of width. These two resonances can be identified with the …
Searching for signatures around 1920 MeV of a N-* state of three hadron nature
We provide a series of arguments which support the idea that the peak seen in the gamma p -> K+ Lambda reaction around 1920 MeV should correspond to the recently predicted state of J(P) = 1/2(+) as a bound state of K(K) over bar N with a mixture of alpha(0)(980)N and f(0)(980)N components. At the same time we propose polarization experiments in that reaction as a further test of the prediction, as well as a study of the total cross-section for gamma p -> K(+)K(-)p at energies close to threshold and of d sigma/dM(inv) for invariant masses close to the two-kaon threshold.
Two, three, many body systems involving mesons
In this talk we show recent developments on few body systems involving mesons. We report on an 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 unambiguous, showing that only on shell two body amplitudes need to be used. Within this approach, systems of two mesons and one baryon are studied, reproducing properties of the low lying $1/2^+$ states. On the other hand we also report on multirho and $K^*$ multirho states which can be asso…
The role of $f_0(1710)$ in the $\phi \omega$ threshold peak of $J/\Psi \to \gamma \phi \omega$
We study the process $J/\Psi \to \gamma \phi \omega$, measured by the BES experiment, where a neat peak close to the $\phi \omega$ threshold is observed and is associated to a scalar meson resonance around 1800 MeV. We make the observation that a scalar resonance coupling to $\phi \omega$ unavoidably couples strongly to $K \bar K$, but no trace of a peak is seen in the $K \bar K$ spectrum of the $J/\Psi \to \gamma K \bar K$ at this energy. This serves us to rule out the interpretation of the observed peak as a signal of a new resonance. After this is done, a thorough study is performed on the production of a pair of vector mesons and how its interaction leads necessarily to a peak in the $J…
Reanalysis of thee+e−→(D*D¯*)±π∓reaction and the claim for theZc(4025)resonance
In this paper we study the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{({D}^{*}{\overline{D}}^{*})}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ in which the BESIII collaboration has claimed the existence of a ${1}^{+}$ resonance, named ${Z}_{c}(4025)$, in the ${D}^{*}{\overline{D}}^{*}$ invariant mass spectrum with a mass around 4026 MeV and width close to 26 MeV . We determine the ${D}^{*}{\overline{D}}^{*}$ 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 …
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…
Dynamically generated N* resonances from the interaction of two mesons and a baryon
We have studied the ππN system and coupled channels by using of the Faddeev equations and two N* and one Δ states, all of them with JP = 1/2+, have been found in the formalism as dynamically generated states. In addition, signatures for a new N* resonance with JP = 1/2+ are found around an energy of 1920 MeV in the three-body center of mass system.
The role of f0(1710) in the ϕω threshold peak of J/Ψ→γϕω
Abstract We study the process J / Ψ → γ ϕ ω , measured by the BES experiment, where a neat peak close to the ϕω threshold is observed and is associated to a scalar meson resonance around 1800 MeV. We make the observation that a scalar resonance coupling to ϕω unavoidably couples strongly to K K ¯ , but no trace of a peak is seen in the K K ¯ spectrum of the J / Ψ → γ K K ¯ at this energy. This serves us to rule out the interpretation of the observed peak as a signal of a new resonance. After this is done, a thorough study is performed on the production of a pair of vector mesons and how its interaction leads necessarily to a peak in the J / Ψ → γ ϕ ω reaction close to the ϕω threshold, due …
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 …
Study of the D*ρ system using QCD sum rules
In this talk I present a study of the $D^* \rho$ system made by using the method of QCD sum rules. Considering isospin and spin projectors, we investigate the different configurations and obtain three $D^*$ mesons with isospin $I=1/2$, spin $S=0$, $1$, $2$ and with masses $2500\pm 67$ MeV, $2523\pm60$ MeV, and $2439\pm119$ MeV, respectively. The last state can be related to $D^*_2(2460)$ (spin 2) listed by the Particle Data Group, while one of the first two might be associated with $D^*(2640)$, whose spin-parity is unknown. In the case of $I=3/2$ we also find evidences of three states with spin 0, 1 and 2, respectively, with masses $2467\pm82$ MeV, $2420\pm128$ MeV, and $2550\pm56$ MeV.
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. …
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 hiddengauge 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.
Partial decay widths of ϕ(2170) to kaonic resonances
In this work, we study the strong decays of $\ensuremath{\phi}(2170)$ to final states involving the kaonic resonances $K(1460)$, ${K}_{1}(1270)$, and ${K}_{1}(1400)$, on which experimental data have recently been extracted by the BESIII Collaboration. The formalism developed here is based on interpreting $\ensuremath{\phi}(2170)$ and $K(1460)$ as states arising from three-hadron dynamics, which is inspired by our earlier works. For ${K}_{1}(1270)$ and ${K}_{1}(1400)$, we investigate different descriptions, such as a mixture of states belonging to the nonet of axial resonances, or the former one as a state originating from the vector-pseudoscalar dynamics. The ratios among the partial widths…
Three-body hadron systems with strangeness
Recently, many efforts are being put in studying three-hadron systems made of mesons and baryons and interesting results are being found. In this talk, we summarize the main features of the formalism used to study such three hadron systems with strangeness S = -1, 0 within a framework built on the basis of unitary chiral theories and solution of the Faddeev equations. In particular, we present the results obtained for the pi(K) over barN, K (K) over barN and KK (K) over bar systems and their respective coupled channels. In the first case, we find four Sigma's and two A's with spin-parity J(P) = 1/2(+), in the 1500-1800 MeV region, as two meson-one baryon s-wave resonances. In the second cas…
Dynamically generated resonances
In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.
Three-body resonances in two-meson-one-baryon systems
We report four $\Sigma$'s and three $\Lambda$'s, in the 1500 - 1800 MeV region, as two meson - one baryon S-wave $(1/2)^+$ resonances. We solve Faddeev equations in the coupled channel approach. The invariant mass of one of the meson-baryon pairs and that of the three particles have been varied and peaks in the squared three body $T$-matrix have been found very close to the existing $S$ = -1, $J^P= 1/2^+$ low lying baryon resonances. The input two-body $t$-matrices for meson-meson and meson-baryon interaction have been calculated by solving the Bethe-Salpeter equation with the potentials obtained in the chiral unitary approach.
Baryon Resonances
10th International Conference on Hypernuclear and Strange Particle Physics. Tokai, JAPAN, SEP 14-18, 2009
Prediction of anI=1DD¯*state and relationship to the claimedZc(3900),Zc(3885)
We study here the interaction of $D{\overline{D}}^{*}$ 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 $q\overline{q}$ 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 $D{\overline{D}}^{*}$ bound state decaying into ${\ensuremath{\eta}}_{c}\ensuremath{\rho}$ and $\ensuremath{\pi}J/\ensuremath{\psi}$ is found. At the same time we…
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).
Exotic states in the S=1 N-pi-K system and low-lying 1/2+ S=-1 resonances
In this manuscript we discuss about our study of the $N \pi \bar{K}$ and the NπK systems made by solving the Faddeev equations with the two-body t-matrices obtained by solving the Bethe-Salpeter equations with the potentials obtained from chiral dynamics. In the strangeness = -1 case, we found that all the Λ and Σ resonances listed by the particle data group, with spin-parity 1/2+ , in the 1550-1800 MeV region get generated due to the involved three-body dynamics. This motivated us to study the strangeness =1 three-body system, i.e., NπK , where we did not find any evidence for the Θ + (1542) but found a broad bump around 1700 MeV which has a κ (800)N structure.
Chiral unitary dynamics of hadrons and hadrons in a nuclear medium
4th DAE-BRNS Workshop on Hadron Physics. Aligarh Muslim Univ, Dept Phys, Aligarh, INDIA, FEB 18-23, 2008
Prediction of an $I=1$ $D \bar D^*$ state and relationship to the claimed $Z_c(3900)$, $Z_c(3885)$
We study here the interaction of $D \bar D^*$ in the isospin $I=1$ channel in the light of recent theoretical advances that allow to combine elements of the local hidden gauge approach with heavy quark spin symmetry. We find that the exchange of light $q \bar q$ is 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 $D\bar{D}^*$ 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 $e^+ e^- \to \pi^{\pm} (D \bar D^*)^\mp$, from w…
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 N*(1710) as a resonance in the ππN system
We study the $\pi \pi N$ system by solving the Faddeev equations, for which the input two-body $t$-matrices are obtained by solving the Bethe-Salpeter equation in the coupled channel formalism. The potentials for the $\pi \pi$, $\pi N$ sub-systems and their coupled channels are obtained from chiral Lagrangians, which have been earlier used to study resonances in these systems successfully. In this work, we find a resonance in the $\pi\pi N$ system with a mass of $1704 - i 375/2$ MeV and with quantum numbers $I=1/2$, $J^\pi =1/2^+$. We identify this state with the $N^*(1710)$. This peak is found where the energies of the $\pi \pi$ sub-system fall in the region of the $\sigma$ resonance. We d…
Three-body hadronic molecules
In this talk, I discuss our recent studies of three-hadron systems and the resonances found therein. The studies consist of solving Faddeev equations with the input two body interactions obtained from the chiral Lagrangians. The systems which we study are either made of two mesons and a baryon or of three mesons. The motivation for these studies comes from the data on many baryon resonances, especially the ones with Jπ = 1/2+, which show a large branching ratio to the two meson-one baryon decay channels. In addition to this, several new studies at BES, BELLE, BABAR etc., claim the existence of new meson resonances which seem to couple strongly to three-meson systems, where mostly two out of…
Study of meson production in nuclei near threshold
We present a study of the η production at low energies in pd collision with 3He and pd nuclear systems in the final state. The η production mechanism is described by a two-step model and the final state interactions are included fully. The η - d and η - 3He final state interactions are incorporated through the solution of the Lippmann Schwinger equation for a half off-shell η - AT-matrix. For η - d this t -matrix is written in a factorized form, with an off-shell form factor multiplying an on-shell part having the scattering length representation. The p - d final state interaction is included by multiplying the production matrix element by the inverse of the Jost function which includes th…
Recent Developments in Chiral Unitary Dynamics of Resonances
In this talk I summarize recent findings made on the description of axial vector mesons as dynamically generated states from the interaction of peseudoscalar mesons and vector mesons, dedicating some attention to the two $K_1(1270)$ states. Then I review the generation of open and hidden charm scalar and axial states. Finally, I present recent results showing that the low lying $1/2^+$ baryon resonances for S=-1 can be obtained as bound states or resonances of two mesons and one baryon in coupled channels dynamics.
X(2175)as a resonant state of theϕKK¯system
We perform a Faddeev calculation for the three-meson system $\ensuremath{\phi}K\overline{K}$, taking the interaction between two pseudoscalar mesons and between a vector and a pseudoscalar meson from the chiral unitary approach. We obtain a neat resonance peak around a total mass of 2150 MeV and an invariant mass for the $K\overline{K}$ system around 970 MeV, very close to the ${f}_{0}(980)$ mass. The state appears in $I=0$ and qualifies as a $\ensuremath{\phi}{f}_{0}(980)$ resonance. We enlarge the space of states including $\ensuremath{\phi}\ensuremath{\pi}\ensuremath{\pi}$, since $\ensuremath{\pi}\ensuremath{\pi}$ and $K\overline{K}$ build up the ${f}_{0}(980)$, and find moderate changes…
Three body systems with strangeness and exotic systems
We report on four $\Sigma$'s and three $\Lambda$'s, in the 1500 - 1800 MeV region, as two meson - one baryon S-wave $(1/2)^+$ resonances found by solving the Faddeev equations in the coupled channel approach, which can be associated to the existing $S$ = -1, $J^P= 1/2^+$ low lying baryon resonances. On the other hand we also report on a new, hidden strangeness $N^*$ state, mostly made of $K \bar{K} N$, with mass around 1920 MeV, which we think could be responsible for the peak seen in the $\gamma p \to K^+ \Lambda$ around this energy. Finally we address a very novel topic in which we show how few body systems of several $\rho$ mesons can be produced, with their spins aligned up to J=6, and …
Reanalysis of the $e^+ e^- \to (D^* \bar D^*)^{\pm} \pi^{\mp}$ reaction and the claim for the $Z_c (4025)$ resonance
In this paper we study the reaction $e^+ e^- \to (D^* \bar D^*)^{\pm} \pi^{\mp}$ in which the BESIII collaboration has claimed the existence of a $1^+$ resonance, named $Z_c(4025)$, in the $D^*\bar D^*$ invariant mass spectrum with a mass around 4026 MeV and width close to 26 MeV. We determine the $D^*\bar D^*$ 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 …
N* resonances in the ππNsystem
We have solved the Faddeev equations for the ππN system and coupled channels resulting into the dynamical generation of two N* , N* (1710) and N* (2100), and one ∆ states, ∆ (1910), all of them with J P = 1/2+ . In addition, signatures for a new N* resonance with JP = 1/2+ are found around at an energy of 1920 MeV.
Searching for exotic states in the N pi K system
We study the N pi K system in order to investigate the possibility of existence of strangeness +1 resonance(s). The formalism consists of solving the Faddeev equations with the N pi, pi K and KN t-matrices obtained from chiral dynamics. The same formalism, which leads to the finding of several 1/2(+) resonances in the corresponding three-body S = -1 channels in the 1400-2000 MeV energy region, results into only one broad bump around 1700 MeV with isospin 0. The amplitudes in isospin 1 and 2 configuration do not have any resonant structure. (C) 2009 Published by Elsevier B.V.