0000000000893524
AUTHOR
Juan Miguel Nieves Pamplona
S-11-N(1535) and -N(1650) resonances in meson-baryon unitarized coupled channel chiral perturbation theory
The s-wave meson-baryon scattering is analyzed for the strangeness S = 0 sector in a Bethe-Salpeter coupled channel formalism incorporating chiral symmetry. Four channels have been considered: piN, etaN, K Lambda, K Sigma. The needed two-particle irreducible matrix amplitude is taken from lowest order chiral perturbation theory in a relativistic formalism and low energy constants are fitted to the elastic piN phase shifts and the pi (-) p-->etan and pi (-) p-->K-0 Lambda cross section data. The position of the complex poles in the second Riemann sheet of the scattering amplitude determines masses and widths of the S-11-N(1535) and -N(1650) resonances, in reasonable agreement with experiment…
Large N-c Weinberg-Tomozawa interaction and negative parity s-wave baryon resonances
It is shown that in the 70 and 700 SU(6) irreducible spaces, the SU(6) extension of the Weinberg-Tomozawa (WT) s-wave meson-baryon interaction incorporating vector mesons (hep-ph/0505233) scales as O(N-c(0)), instead of the well-known O(N-c(-1)) behavior for its SU(3) counterpart. However, the WT interaction behaves as order O(N-c(-1)) within the 56 and 1134 meson-baryon spaces. Explicit expressions for the WT couplings (eigenvalues) in the irreducible SU(2N(F)) spaces, for arbitrary N-F and N-c, are given. This extended interaction is used as a kernel of the Bethe Salpeter equation, to study the large N-c scaling of masses and widths of the lowest-lying negative parity s-wave baryon resona…
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.
S=-1 meson-baryon unitarized coupled channel chiral perturbation theory and the S-01 resonances Lambda(1405) and -Lambda(1670)
The s-wave meson-baryon scattering is analyzed for the strangeness S=-1 and isospin I=0 sector in a Bethe-Salpeter coupled channel formalism incorporating chiral symmetry. Four channels have been considered: piSigma, (K) over barN, etaLambda, and KXi. The required input to solve the Bethe-Salpeter equation is taken from lowest order chiral perturbation theory in a relativistic formalism. There appear undetermined low energy constants, as a consequence of the renormalization of the amplitudes, which are obtained from fits to the piSigma-->piSigma mass spectrum, to the elastic (K) over barN-->(K) over barN and (K) over barN-->piSigma t matrices and to the K(-)p-->etaLambda cross section data.…
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…
A lattice study of the form factors A(0) and A(3) in the decay (B)over-bar(0)->rho(+)l(-)(nu)over-bar(l)
We report on a lattice calculation of the form factors A(0) and A(3) for the pseudoscalar to vector meson semileptonic decay (B) over bar(0) --> rho(+)l(-)(1). We find that resonant (or pole-type) contributions alone are unable to describe these two form factors simultaneously. For the quantity A(0)(q(2) = 0), which is important phenomenologically for the determination of \V-ub\, we extract a range of values, A(0)(q(2) = 0) = (0.16-0.35)(-6)(+9), where the range is due to systematic uncertainty and the quoted error is statistical. We have also determined A(2)(q(2) = 0) = 0.28(-6-5)(+9+4).
Improved B ->pi l nu(iota) form factors from the lattice
We present the results of a lattice computation of the form factors for B-0 --> pi(-)l(+)nu(l) decays near zero-recoil. These results will allow a determination of the CKM matrix element \V-ub\ when measurements of the differential decay rate become available. We also provide models for extrapolation of the form factors and rate to the full recoil range. Our computation is performed in the quenched approximation to QCD on a 24(3) x 48 lattice at beta = 6.2, using a non-perturbatively O(a)-improved action. The masses of all light valence quarks involved are extrapolated to their physical values.
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.
Large-N(C) properties of the rho and f(0)(600) mesons from unitary resonance chiral dynamics
We construct pi-pi amplitudes that fulfill exact elastic unitarity, account for one loop Chiral Perturbation Theory contributions and include all 1/Nc leading terms, with the only limitation of considering just the lowest-lying nonet of exchanged resonances. Within such scheme, the Nc dependence of sigma and rho masses and widths is discussed. Robust conclusions are drawn in the case of the rho resonance, confirming that it is a stable meson in the limit of a large number of QCD colors, Nc. Less definitive conclusions are reached in the scalar-isoscalar sector. With the present quality of data, we cannot firmly conclude whether or not the Nc=3 f0(600) resonance completely disappears at larg…
Extracting vertical bar V-ub vertical bar from B ->pi l nu decays using a multiply-subtracted Omnes dispersion relation
We use a multiply-subtracted Omnes dispersion relation for the form factor f(+) in B ->pi semileptonic decay, allowing the direct input of experimental and theoretical information to constrain its dependence on q(2), thereby improving the precision of the extracted value of vertical bar V-ub vertical bar. Apart from these inputs we use only unitarity and analyticity properties. We obtain vertical bar V-ub vertical bar=(4.02 +/- 0.35)x10(-3), improving the agreement with the value determined from inclusive methods, and competitive in precision with them.
$K^-$-Nucleus Scattering at Low and Intermediate Energies
We calculate $K^-$-nucleus elastic differential, reaction and total cross sections for different nuclei ($^{12}$C,$^{40}$Ca and $^{208}$Pb) at several laboratory antikaon momenta, ranging from 127 MeV to 800 MeV. We use different antikaon-nucleus optical potentials, some of them fitted to kaonic atom data, and study the sensitivity of the cross sections to the considered antikaon-nucleus dynamics.
Study of the strong Sigma(b) -> Lambda(b)pi and Sigma*(b) -> Lambda(b)pi in a nonrelativistic quark model
We present results for the strong widths corresponding to the Sigma(b) -> Lambda(b)pi and Sigma*(b) -> Lambda(b)pi decays. We apply our model from Phys. Rev. D 72, 094022 (2005), where we previously studied the corresponding transitions in the charmed sector. Our nonrelativistic constituent quark model uses wave functions that take advantage of the constraints imposed by heavy quark symmetry. The partial conservation of axial current hypothesis allows us to determine the strong vertices from an analysis of the axial current matrix elements.
B -> rho semileptonic decays and vertical bar V-ub vertical bar
We reevaluate the B -> rho l(+) nu(l) decay width as a full B. pi pi iota(+)nu iota four-particle decay, in which the two final pions are produced via an intermediate. meson. The decay width can be written as a convolution of the B -> rho l(+) nu(l) decay width, for an off-shell., with the.. pp line shape. This allows us to fully incorporate the effects of the finite. meson width and a better comparison with actual experiments. We use an Omn s representation to provide the dependence of the B.. semileptonic form factors on q2. The Omn s subtraction constants and the overall normalization parameter jVubj are fitted to light cone sum rules and lattice QCD theoretical form-factor calculations,…
Study of the leptonic decays of pseudoscalar B,D and vector B-*,D-* mesons and of the semileptonic B -> D and B -> D-* decays
We present results for different observables in weak decays of pseudoscalar and vector mesons with a heavy c or b quark. The calculations are done in a nonrelativistic constituent quark model improved at some instances by heavy quark effective theory constraints. We determine pseudoscalar and vector meson decay constants that within a few percent satisfy f(V)M(V)/f(P)M(P)=1, a result expected in heavy quark symmetry when the heavy quark masses tend to infinity. We also analyze the semileptonic B -> D and B -> D-* decays for which we evaluate the different form factors. Here we impose heavy quark effective theory constraints among form factors that are not satisfied by a direct quark model c…
Lattice study of the decay (B)over-bar(0)->p(+)l(-)(v)over-bar(l): Model-independent determination of vertical bar V-ub vertical bar
We present results of a lattice computation of the vector and axial-vector current matrix elements relevant for the semileptonic decay (B) over bar(0) --> rho(+)l(-)(l). The computations are performed in the quenched approximation of lattice QCD on a 24(3) x 48 lattice at beta = 6.2, using an O(a) improved fermionic action. Our principal result is for the differential decay rate, d Gamma/dq(2), for the decay (B) over bar(0) --> rho(+)l(-)(l), in a region beyond the charm endpoint, allowing a model-independent extraction of \V-ub\ from experimental measurements. Heavy quark symmetry relations between radiative and semileptonic decays of (B) over bar mesons into light vector mesons are also d…
(B)over-bar(s) -> K semileptonic decay from an Omnes improved constituent quark model
We study the f(+) form factor for the semileptonic (B) over bar (s) -> K+ l(-) (V) over bar (l) decay in a constituent quark model. The valence quark estimate is supplemented with the contribution from the (B) over bar* pole that dominates the high q(2) region. We use a multiply-subtracted Omnes dispersion relation to extend the quark model predictions from its region of applicability near q(max)(2) = (M-Bs ¿ M-K)(2) similar to 23.75 GeV2 to all q(2) values accessible in the physical decay. To better constrain the dependence of f(+) on q(2), we fit the subtraction constants to a combined input from previous light cone sum rule by Duplancic and Melic (2008) [11] and the present quark model r…
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
Lattice study of semileptonic b-decays - (b)over-bar-]dl(nu)over-bar decays
We present a study of semileptonic ($) over bar B --> Dl ($) over bar v decays in quenched lattice QCD through a calculation of the matrix element [D\($) over bar c gamma(mu)b\($) over bar B] on a 24(3) x 48 lattice at beta = 6.2, using an O(alpha)-improved fermion action. We perform the calculation for several values of the initial and final heavy-quark masses around the charm mass, and three values of the light-(anti)quark mass around the strange mass. Because the charm quark has a bare mass which is almost 1/3 the inverse lattice spacing, we study the ensuing mass-dependent discretization errors, and propose a procedure for subtracting at least some of them nonperturbatively. We extract …
Vertical bar V-ub vertical bar from exclusive semileptonic B ->pi decays
We use Omnes representations of the form factors f(+) and f(0) for exclusive semileptonic B -> pi decays, paying special attention to the treatment of the B* pole and its effect on f(+). We apply them to combine experimental partial branching fraction information with theoretical calculations of both form factors to extract vertical bar V-ub vertical bar. The precision we achieve is competitive with the inclusive determination and we do not find a significant discrepancy between our result. vertical bar V-ub vertical bar (3.90 +/- 0.32 +/- 0.18) x 10(-3), and the inclusive world average value, (4.45 +/- 0.20 +/- 0.26) x 10(-3).
Nu induced threshold production of two pions and N* (1440) electroweak form factors
We study the threshold production of two pions induced by neutrinos in nucleon targets. The contribution of nucleon, pion, and contact terms are calculated using a chiral Lagrangian. The contribution of the Roper resonance, neglected in earlier studies, has also been taken into account. The numerical results for the cross sections are presented and compared with the available experimental data. It has been found that in the two-pion channels with pi(+)pi(-) and pi(0)pi(0) in the final state, the contribution of the N* (1440) is quite important and could be used to determine the N* (1440) electroweak transition form factors if experimental data with better statistics become available in the …
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.
Exclusive c -> s, d semileptonic decays of ground-state spin-1/2 doubly charmed baryons
We evaluate exclusive semileptonic decays of ground-state spin-1/2 doubly heavy charmed baryons driven by a c→s,dc→s,d transition at the quark level. Our results for the form factors are consistent with heavy quark spin symmetry constraints which are valid in the limit of an infinitely massive charm quark and near zero recoil. Only a few exclusive semileptonic decay channels have been theoretically analyzed before. For those cases we find that our results are in a reasonable agreement with previous calculations.
Deriving the existence of B(B)over-bar* bound states from the X(3872) and heavy quark symmetry
We discuss the possibility and the description of bound states between B and (B) over bar* mesons. We argue that the existence of such a bound state can be deduced from (i) the weakly bound X(3872) state, (ii) certain assumptions about the short-range dynamics of the D (D) over bar* system and (iii) heavy quark symmetry. From these assumptions the binding energy of the possible B (B) over bar* bound states is determined, first in a theory containing only contact interactions which serves as a straightforward illustration of the method, and then the effects of including the one-pion exchange potential are discussed. In this latter case three isoscalar states are predicted: a positive and neg…
Semileptonic bc to cc baryon decay and heavy quark spin symmetry
We study the semileptonic decays of the lowest-lying bc baryons to the lowest-lying cc baryons (Xi(('*))(bc)->Xi((*))(cc) and Omega(('*))(bc)->Omega((*))(cc)), in the limit m(b),m(c)>Lambda(QCD) and close to the zero-recoil point. The separate heavy quark spin symmetries make it possible to describe all these decays using a single form factor. We recover results derived previously by White and Savage in a manner which we think is more straightforward and parallels the method applied later to study B-c semileptonic decays. We further discuss the resemblance between the bc baryon decays and those of B-c mesons to eta(c) and J/psi mesons and comment on the relation between the slopes of the si…
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.
Vertical bar V-ub vertical bar from exclusive semileptonic Beta ->pi decays revisited
We update the extraction of |V-ub| from exclusive semileptonic B ->pi decays, combining experimental partial branching fraction information with theoretical form-factor calculations, using the recently revised HPQCD results for the form factors f(+) and f(0). We use Omnes representations to provide the required parametrizations of the form factors. The extracted value is |V-ub|=(3.47 +/- 0.29 +/- 0.03)x10(-3), in striking agreement with |V-ub| extracted using all other inputs in CKM fits and showing some disagreement with |V-ub| extracted from inclusive semileptonic B ->pi decays.
Bethe-Salpeter approach for the P-33 elastic pion-nucleon scattering in heavy baryon chiral perturbation theory
Heavy baryon chiral perturbation theory (HBChPT) to leading order provides a kernel to solve the Bethe-Salpeter equation for the P-33 [Delta (1232)-channel] pi -N system, in the infinite nucleon mass limit. Crossed Born terms include, when iterated within the Bethe-Salpeter equation, both all one- and some two-pion intermediate states, hence preserving elastic unitarity below the two-pion production threshold. This suggests searching for a solution with the help of dispersion relations and suitable subtraction constants, when all in-elasticities are explicitly neglected. The solution allows for a successful description of the experimental phase shift from threshold Lip to roots = 1500 MeV i…
Elastic s-wave B pi, D pi, DK and K pi scattering from lattice calculations of scalar form factors in semileptonic decays
We show how theoretical, principally lattice calculations of the scalar form factors in semileptonic pseudoscalar-to-pseudoscalar decays can be used to extract information about the corresponding elastic s-wave scattering channels. We find values for the scattering lengths m(pi)a=0.179(17)(14), 0.26(26) and 0.29(4) for elastic s-wave isospin-1/2 K pi, B pi and D pi channels, respectively. We also determine phase shifts. For the DK channel we find hints that there is a bound state which can be identified with the recently discovered D-s0(+)(2317).
Role of the N * (2080) resonance in the (gamma)over-right-arrowp -> K+ Lambda(1520) reaction
We investigate the Lambda (1520) photoproduction in the (gamma) over right arrowp -> K+ Lambda(1520) reaction within the effective Lagrangian method near threshold. In addition to the 'background' contributions from the contact, t-channel K-exchange, and s-channel nucleon pole terms, which were already considered in previous studies, the contribution from the nucleon resonance N*(2080) (spin-parity J(P) = 3/2(-)) is also considered. We show that the inclusion of the nucleon resonance N*(2080) leads to a fairly good description of the new LEPS differential cross-section data, and that these measurements can be used to determine some of the properties of this latter resonance. However, seriou…
Form Factors for B -> pi l nu-bar_l and B -> K* gamma Decays on the Lattice
We present a unified method for analysing form factors in B --> pi l ($) over bar nu(l) and B --> K*gamma decays. The analysis provides consistency checks on the q(2) and 1/M extrapolations necessary to obtain the physical decay rates. For the first time the q(2) dependence of the form factors is obtained at the B scale. In the B --> pi l ($) over bar nu(l) case, we show that pole fits to f(+) may not be consistent with the q(2) behaviour of f(0), leading to a possible factor of two uncertainty in the decay rate and hence in the value of /V-ub/(2) deduced from it. For B --> K*gamma, from the combined analysis of form factors T-1 and T-2, we find the hadronisation ratio R(K)* of the exclusiv…
Photon induced Lambda (1520) production and the role of the K* exchange
We study the photon induced Lambda(1520) production in the effective Lagrangian method near threshold, E_��^{LAB}<2 GeV, and in the quark-gluon string model at higher energies 3 GeV < E_��^{LAB} < 5 GeV. In particular, we study the role of the K^* exchange for the production of Lambda(1520) within the SU(6) Weinberg-Tomozowa chiral unitary model proposed in Phys. Rev. D74 (2006) 034025. The coupling of the Lambda(1520) resonance to the N \bar K^* pair, which is dynamically generated, turns out to be relatively small and, thus, the K exchange mechanism dominates the reaction. In the higher energy region, where experimental data are available, the quark-gluon string mechanism with th…
Combined nonrelativistic constituent quark model and heavy quark effective theory study of semileptonic decays of \Lambda_b and \Xi_b baryons
We present the results of a nonrelativistic constituent quark model study of the semileptonic decays $\Lambda_b^0 \to \Lambda_c^+ l^- {\bar \nu}_l$ and $\Xi_b^0 \to \Xi_c^+ l^- {\bar \nu}_l$. We work on coordinate space, with baryon wave functions recently obtained from a variational approach based on heavy quark symmetry . We develop a novel expansion of the electroweak current operator, which supplemented with heavy quark effective theory constraints, allows us to predict the baryon form factors and the decay distributions for all $q^2$ (or equivalently $w$) values accessible in the physical decays. Our results for the partially integrated longitudinal and transverse decay widths, in the …
First lattice study of semileptonic decays of Lambda(b) and Xi(b) baryons
We present the results of the first lattice study of semileptonic decays of baryons containing a b quark. Predictions for the decay distributions are given and the Isgur-Wise functions for heavy baryons are computed for values of the velocity transfer up to about omega = 1.2. The computations are performed on a 24(3) x 48 lattice at beta = 6.2 using the Sheikholeslami-Wohlert action in the quenched approximation.
What does the free space Lambda Lambda interaction predict for Lambda Lambda hypernuclei?
Data on LambdaLambda hypernuclei provide a unique method to learn details about the strangeness S=-2 sector of the baryon-baryon interaction. From the free space Bonn-Julich potentials, determined from data on baryon-baryon scattering in the S=0, -1 channels, we construct an interaction in the S=-2 sector to describe the experimentally known LambdaLambda hypernuclei. After including short-range (Jastrow) and RPA correlations, we find masses for these LambdaLambda hypernuclei in a reasonable agreement with data, taking into account theoretical and experimental uncertainties. Thus, we provide a natural extension, at low energies, of the Bonn-Julich one-boson exchange potentials to the S=-2 ch…
Double $\Lambda$ Hypernuclei and the Nuclear Medium Effective $\Lambda\Lambda$ Interaction
We fit the $^1 S_0 \Lambda\Lambda$ interaction in the nuclear medium to the masses of the experimentally known double-$\Lambda$ hypernuclei: $^{\phantom{6}6}_{\Lambda\Lambda}$He, $^{10}_{\Lambda\Lambda}$Be and $^{13}_{\Lambda\Lambda}$B. We derive this effective interaction from OBE J\"ulich $\Lambda\Lambda$-type potentials and using both Hartree-Fock and variational approaches. We find that the inclusion of $\Lambda\Lambda$ correlations in the variational scheme leads to significant differences and a better understanding of the dynamical features of the system. We investigate the sensitivity of the binding energies and the mesonic decay widths of the above double-$\Lambda$ hypernuclei to th…
Properties of the rho and sigma mesons from unitary chiral dynamics
The chiral limit of the rho and sigma masses and widths is discussed. We work within the inverse amplitude method to one loop in SU(2) chiral perturbation theory and analyze the consequences that all chiral logarithms cancel out in the rho channel, while they do not cancel for the sigma case, and how they strongly influence the properties of this latter resonance. Our results confirm and explain the different behavior of the sigma and rho poles for N(C) not far from 3, but we extend the analysis to very large N(C), where the behavior of these two resonances is reanalyzed. We note that the rather natural requirement of consistency between resonance saturation and unitarization imposes useful…
X(3872) and its Partners in the Heavy Quark Limit of QCD
In this letter, we propose interpolating currents for the X(3872) resonance, and show that, in the Heavy Quark limit of QCD, the X(3872) state should have degenerate partners, independent of its internal structure. Magnitudes of possible I=0 and I=1 components of the X(3872) are also discussed.
Study of the strong Sigma(c)->Lambda(c)pi,Sigma(*)(c)->Lambda(c)pi and Xi(*)(c)->Xi(c)pi decays in a nonrelativistic quark model
We present results for the strong widths corresponding to the Sigma(c)->Lambda(c)pi, Sigma(c)(*)->Lambda(c)pi and Xi(c)(*)->Xi(c)pi decays. The calculations have been done in a nonrelativistic constituent quark model with wave functions that take advantage of the constraints imposed by heavy quark symmetry. Partial conservation of axial current hypothesis allows us to determine the strong vertices from an analysis of the axial current matrix elements. Our results Gamma(Sigma(c)(++)->Lambda(c)(+)pi(+))=2.41 +/- 0.07 +/- 0.02 MeV, Gamma(Sigma(c)(+)->Lambda(c)(+)pi(0))=2.79 +/- 0.08 +/- 0.02 MeV, Gamma(Sigma(c)(0)->Lambda(c)(+)pi(-))=2.37 +/- 0.07 +/- 0.02 MeV, Gamma(Sigma(c)(*++)->Lambda(c)(+…
Exclusive c -> s, d semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy cb baryons
We evaluate exclusive semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy cb baryons driven by a c→s, d transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil. Based on those constraints we make model-independent, though approximate, predictions for ratios of decay widths.
Hidden charm N and Delta resonances with heavy-quark symmetry
A model is developed to describe odd-parity baryon resonances generated dynamically through a unitary baryon-meson coupled-channels approach. The scheme applies to channels with light- and/or heavy-quark content. Distinct features of the model are that i) the interaction is an S-wave contact one, ii) it reduces to the SU(3) Weinberg-Tomozawa Hamiltonian when light pseudoscalar mesons are involved, thus respecting chiral symmetry, iii) spin-flavor is preserved in the light-quark sector, and iv) heavy-quark spin symmetry is fulfilled in the heavy-quark sector. In particular, baryon-meson states with different content in c or in (c) over bar do not mix. The model is a minimal one and it contai…