Hadronic Lagrangian Research Articles

Strong decays of the hadronic molecule (2012)

Strong two- and three-body decays of the new excited hyperon Ω*(2012) are discussed in the hadronic molecular approach. The Ω*(2012) state is considered to contain the mixed and Ωη hadronic components. In our calculations we use a phenomenological hadronic Lagrangian for description of interaction of the Ω*(2012) state with constituents and of constituents to other hadrons occurring in the final state. Our results show that the decay widths of the two-body decay modes lie in the few MeV region and are compatible with or dominate over the rates of the three-body modes . The sum of two- and three-body decay widths is consistent with a width of the Ω*(2012) originally measured by the Belle collaboration. A possible scenario for the suppression of the three-body decay rate recently noticed by the Belle collaboration is due to the dominant admixture of the Ωη hadronic component in the Ω*(2012) state.

Baryonic sources of thermal photons

Thermal radiation of photons and dileptons from hadronic matter plays an essential role in understanding electromagnetic emission spectra in high-energy heavy-ion collisions. In particular, baryons and anti-baryons have been found to be strong catalysts for electromagnetic radiation, even at collider energies where the baryon chemical potential is small. Here, we conduct a systematic analysis of $\pi$- and $\omega$-meson-induced reactions off a large set of baryon states. The interactions are based on effective hadronic Lagrangians where the parameters are quantitatively constrained by empirical information from vacuum decay branchings and scattering data, and gauge invariance is maintained by suitable regularization procedures. The thermal emission rates are computed using kinetic theory but can be directly compared to previous calculations using hadronic many-body theory. The comparison to existing calculations in the literature reveals our newly identified contributions to be rather significant.

Masses and decay widths of charmonium states in the presence of strong magnetic fields

The masses and decay widths of charmonium states are studied in the presence of strong magnetic fields. The mixing between the pseudoscalar and vector charmonium states at rest is observed to lead to appreciable negative (positive) shifts in the masses of the pseudoscalar (longitudinal component of the vector) charmonium states in vacuum/hadronic medium in the presence of high magnetic fields. The pseudoscalar and vector charmonium masses in the hadronic medium, calculated in an effective chiral model from the medium changes of a scalar dilaton field, have additional significant modifications due to the mixing effects. The masses of the $D$ and $\bar D$ mesons in the magnetized hadronic matter are calculated within the chiral effective model. The partial decay widths of the vector charmonium state to $D\bar D$ are computed using a field theoretical model for composite hadrons with quark/antiquark constituents, and are compared to the decay widths calculated using an effective hadronic Lagrangian. The effects of the mixing are observed to lead to significant contributions to the masses of the pseusoscalar and vector charmonium states, and an appreciable increase in the decay width $\psi(3770) \rightarrow D\bar D$ at large values of the magnetic fields. These studies of the charmonium states in strong magnetic fields should have observable consequences on the dilepton spectra, as well as on the production of the open charm mesons and the charmonium states in ultra relativistic heavy ion collision experiments.

Dynamical Approach to Decays of XYZ States

We review the existing results on the exotic XYZ states and their decays obtained within the confined covariant quark model. This dynamical approach is based on a non-local Lagrangian of hadrons with quarks, has built-in quark confinement, and is suited well for the description of different multiquark states, including the four quark ones. We focus our analysis on the various decay modes of five exotic states, X ( 3872 ) , Z c ( 3900 ) , Y ( 4260 ) , Z b ( 10610 ) , and Z b ′ ( 10650 ) , aiming to clarify their internal quark structures. By considering mostly branching fractions and decay widths using the molecular-type or the tetraquark-type interpolating currents, conclusions about the nature of these particles are drawn: the molecular structure is favored for Z c ( 3900 ) , Z b ( 10610 ) , and Z b ′ ( 10650 ) and the tetraquark for X ( 3872 ) and Y ( 4260 ) .

Interactions of Bc mesons in relativistic heavy-ion collisions

We calculate the absorbtion cross-sections of $B_{c}$ mesons by $\pi$ and $\rho$ mesons including anomalous processes using an effective hadronic Lagrangian. The enhancement of Bc production is expected due to QGP formation in heavy-ion experiments. However it is also expected that the production rate of Bc meson can be affected due to the interaction with comovers. These processes are relevant for experiments at RHIC. Thermal average cross-sections of $B_{c}$ are evaluated with form factor when a cut off parameter in it is 1 and 2 GeV. Using these thermal average cross-sections in the kinetic equation we investigate the time evolution of $B_{c}$ mesons due to dissociation in the hadronic matter formed at RHIC.

Role of scalar mesons in the beam asymmetry of pp¯ and ΛΛ¯ photoproduction at JLab

We suggest a description of the beam asymmetry in $p \bar p$ and $\Lambda \bar \Lambda$ photoproduction off the proton $\vec\gamma + p \to p \bar p + p$ and $\vec\gamma + p \to \Lambda \bar\Lambda + p$, takes into account the contribution of the scalar mesons $f_0(1370)$, $f_0(1500)$, and $f_0(1710)$. These scalars are considered as mixed states of a glueball and nonstrange and strange quarkonia in the framework based on the use of effective hadronic Lagrangians. Present results can be used to guide the possible search for this reaction by the GlueX Collaboration at JLab. Also, we did an estimate of contribution of heavier scalar meson states $f_0(2020)$, $f_0(2100)$, and $f_0(2200)$.

Strong form factor of delta (1232)

Our article is devoted to study of the D®Np decay. Strong decay D®Np is one of the best modes to search for particles with spin 3/2. Strong decay is dominating channel of decay, i.e. D - isobar decay consist of 99% - hadronic decay, 1% - electromagnetic decay, therefore the decay is important for nuclear research. We calculate relevant form factors in the framework of the covariant quark model with infrared confinement in the full kinematical momentum transfer region. The covariant quark model has been applied to a large number of elementary particle processes. This model can be viewed as an effective quantum field approach to hadronic interactions, which based on an interaction Lagrangian of hadrons interacting with their constituent quarks. The coupling strength is determined by the compositeness condition ZH = 0 where ZH is the renormalization constant of the hadron wave function. We compare the obtained results with available experimental data and the results from other theoretical approaches.

Search for the glueball content of hadrons inγpinteractions at GlueX

We suggest a theoretical framework for the description of double photon and proton-antiproton photoproduction off the proton gamma + p -> 2 gamma + p and gamma + p -> antip + p + p which takes into account the contribution of the scalar mesons f0(1370), f0(1500) and f0(1710). These scalars are considered as mixed states of a glueball and nonstrange and strange quarkonia. Our framework is based on the use of effective hadronic Lagrangians that phenomenologically take into account two-gluon exchange effects governing the gamma + p -> 2 gamma + p and gamma + p -> antip + p + p processes. Present results can be used to guide the possible search for these reactions by the GlueX Collaboration at JLab.

Diffusion ofΛcin hot hadronic medium and its impact onΛc/Dratio

The drag and diffusion coefficients of the $\Lambda_c(2286$ MeV) have been evaluated in the hadronic medium which is expected to be formed in the later stages of the evolving fire ball produced in heavy ion collisions at RHIC and LHC energies. The interactions between the $\Lambda_c$ and the hadrons in the medium have been derived from an effective hadronic Lagrangian as well as from the scattering lengths, obtained in the framework of heavy baryon chiral perturbation theory (HB$\chi$PT). In both the approaches, the magnitude of the transport coefficients are turn out to be significant. A larger value is obtained in the former approach with respect to the latter. Significant values of the coefficients indicate substantial amount of interaction of the $\Lambda_c$ with the hadronic thermal bath. Furthermore, the transport coefficients of the $\Lambda_c$ is found to be different from the transport coefficients of $D$ meson. Present study indicates that the hadronic medium has a significant impact on the $\Lambda_c/D$ ratio in heavy ion collisions.

Physics input for modelling superfluid neutron stars with hyperon cores

Observations of massive ($M \approx 2.0~M_\odot$) neutron stars (NSs), PSRs J1614-2230 and J0348+0432, rule out most of the models of nucleon-hyperon matter employed in NS simulations. Here we construct three possible models of nucleon-hyperon matter consistent with the existence of $2~M_\odot$ pulsars as well as with semi-empirical nuclear matter parameters at saturation, and semi-empirical hypernuclear data. Our aim is to calculate for these models all the parameters necessary for modelling dynamics of hyperon stars (such as equation of state, adiabatic indices, thermodynamic derivatives, relativistic entrainment matrix, etc.), making them available for a potential user. To this aim a general non-linear hadronic Lagrangian involving $\sigma\omega\rho\phi\sigma^\ast$ meson fields, as well as quartic terms in vector-meson fields, is considered. A universal scheme for calculation of the $\ell=0,1$ Landau Fermi-liquid parameters and relativistic entrainment matrix is formulated in the mean-field approximation. Use of this scheme allow us to obtain numerical tables with the equation of state, Landau quasiparticle effective masses, adiabatic indices, the $\ell=0,1$ Landau Fermi-liquid parameters, and the relativistic entrainment matrix for the selected models of nucleon-hyperon matter. These data are available on-line and suitable for numerical implementation in computer codes modelling various dynamical processes in NSs, in particular, oscillations of superfluid NSs and their cooling.

Quark deconfinement in high-mass neutron stars

In this paper, we explore whether or not quark deconfinement may occur in high-mass neutron stars such as J1614 \ensuremath{-} 2230 ($1.97\ifmmode\pm\else\textpm\fi{}0.04\phantom{\rule{0.16em}{0ex}}{M}_{\ensuremath{\bigodot}}$) and J0348 + 0432 ($2.01\ifmmode\pm\else\textpm\fi{}0.04\phantom{\rule{0.16em}{0ex}}{M}_{\ensuremath{\bigodot}}$). Our study is based on a nonlocal extension of the SU(3) Nambu--Jona-Lasinio (n3NJL) model with repulsive vector interactions among the quarks. This model goes beyond the frequently used local version of the Nambu--Jona-Lasinio (NJL) model by accounting for several key features of QCD which are not part of the local model. Confined hadronic matter is treated in the framework of nonlinear relativistic mean field theory. We find that both the local as well as the nonlocal NJL model predict the existence of extended regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars with masses of 2.1 to $2.4\phantom{\rule{0.16em}{0ex}}{M}_{\ensuremath{\bigodot}}$. Pure quark matter in the cores of neutron stars is obtained for certain parametrizations of the hadronic lagrangian and choices of the vector repulsion among quarks. The radii of high-mass neutron stars with quark-hybrid matter and/or pure quark matter cores in their centers are found to lie in the canonical range of 12 to 13 km.

Form factors for BK l+l- decay

The exclusive BV(P)l+l- and BV decays, with a vector (V=K*, , …) or pseudo scalar (P=K, , …) meson in the final state are important for the search for flavour-changing new physics. In this paper we study one of the exclusive rare decays of pseudo scalar B mesons: BKl+l- by using a relativistic constituent quark model, including infrared connement. We calculate the relevant form factors of the (BP) transitions in the full kinematical range of momentum transfer. The calculated form factors are used to evaluate differential decay rates and polarization observables. We present numerical results on these observables using the covariant quark model. This model can be viewed as an effective quantum field theory approach based on an interaction Lagrangian of hadrons interacting with their constituent quarks. Universal and reliable predictions for exclusive processes involving both mesons composed from a quark and antiquark and baryons composed from three quarks result from this approach.

Subthreshold cascade production in heavy ion collisions

Using a gauged flavor SU(3)-invariant hadronic Lagrangian, we have calculated the cross sections for the strangeness-exchange reactions in the Born approximation. These cross sections are then used in the Relativistic Vlasov-Uehling-Uhlenbeck (RVUU) transport model to study Ξ production in Ar+KCl collisions at incident energy of 1.76A GeV and impact parameter b = 3.5 fm. We find that including the contributions of hyperonhyperon scattering channels strongly enhances the yield of Ξ, leading to the abundance ratio which is essentially consistent with the recently measured value of by the HADES collaboration at GSI.

Contributions of hyperon-hyperon scattering to subthreshold cascade production in heavy ion collisions

Using a gauged flavor SU(3)-invariant hadronic Lagrangian, we calculate the cross sections for the strangeness-exchange reactions $YY\ensuremath{\leftrightarrow}N\ensuremath{\Xi}$ ($Y=\ensuremath{\Lambda},\ensuremath{\Sigma}$) in the Born approximation. These cross sections are then used in the relativistic Vlasov-Uehling-Uhlenbeck transport model to study $\ensuremath{\Xi}$ production in $\mathrm{Ar}+\mathrm{KCl}$ collisions at incident energy of 1.76A GeV and impact parameter $b=3.5$ fm. We find that including the contributions of hyperon-hyperon scattering channels strongly enhances the yield of $\ensuremath{\Xi}$, leading to the abundance ratio ${\ensuremath{\Xi}}^{\ensuremath{-}}/(\ensuremath{\Lambda}+{\ensuremath{\Sigma}}^{0})=3.38\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, which is essentially consistent with the recently measured value of $(5.6\ifmmode\pm\else\textpm\fi{}{1.2}_{\ensuremath{-}1.7}^{+1.8})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ by the HADES Collaboration at GSI.

Absorption cross sections by nucleons

The cross sections of $B_{c}$\ absorption by nucleons are calculated in meson-baryon exchange model using hadronic Lagrangian based on SU(4)/SU(5) flavor symmetries. The values of different coupling constants used in the model are obtained from vector meson dominance model, QCD sum rule or SU(4)/SU(5) flavor symmetries. Calculated values of cross sections are found to be significantly different from the previous study in which b-flavored hadron exchange is neglected. These results could be useful in calculating production rate of $B_{c}$ meson in relativistic heavy ion collisions.

Hadronic absorption cross sections ofBc

The cross sections of $B_{c}$\ absorption by $\pi $ mesons are calculated using hadronic Lagrangian based on SU(5) flavor symmetry. Calculated cross sections are found to be in range 2 to 7 mb and 0.2 to 2 mb for the processes $B_{c}^{+}\pi \rightarrow DB$ and $B_{c}^{+}\pi \rightarrow D^{\ast}B^{\ast}$ respectively, when the monopole form factor is included. These results could be useful in calculating production rate of $B_{c}$ meson in relativistic heavy ion collisions.

High energy constraints in the octetSS−PPcorrelator and resonance saturation at next-to-leading order in1/NC

We study the octet SS-PP correlator within resonance chiral theory up to the one-loop level, i.e., up to next-to-leading order in the 1/Nc expansion. We will require that our correlator follows the power behaviour prescribed by the operator product expansion at high euclidian momentum. Nevertheless, we will not make use of short-distance constraints from other observables. Likewise, the high-energy behaviour will be demanded for the whole correlator, not for individual absorptive channels. The amplitude is progressively improved by considering more and more complicated operators in the hadronic lagrangian. Matching the resonance chiral theory result with chiral perturbation theory at low energies produces the estimates L_8(mu)^{SU(3)} = (1.0+-0.4)10^-3 and C_{38}(mu)^{SU(3)} = (8+-5) 10^-6 for mu=770 MeV. The effect of alternative renormalization schemes is also discussed in the article.

Three-particle model of the pion-nucleon system

A relativistic, three-particle model of the pion-nucleon system is constructed in the instant form of relativistic quantum mechanics using the Bakamjian-Thomas procedure. The model space includes subspaces for the nucleon $(N)$, the resonances $\ensuremath{\Delta}={P}_{33}(1232)$, ${P}_{11}(1440)$, ${D}_{13}(1520)$, ${S}_{11}(1535)$, and ${S}_{31}(1620)$, as well as $\ensuremath{\pi}N$, $\ensuremath{\pi}\ensuremath{\Delta}$, $\ensuremath{\eta}N$, and $\ensuremath{\pi}\ensuremath{\pi}N$ subspaces. The model specifies a Poincar\'e invariant mass operator that includes vertex interactions that couple the various subspaces, as well as renormalization terms. Projection operator techniques are used to reduce the equations arising from this mass operator to a set of three-dimensional Lippmann-Schwinger integral equations that couple only the $\ensuremath{\pi}N$, $\ensuremath{\pi}\ensuremath{\Delta}$, and $\ensuremath{\eta}N$ channels. After a partial wave analysis these three-dimensional equations simplify to three coupled, one-dimensional integral equations for each partial wave. The mass operator interactions are derived from effective, hadronic Lagrangians that introduce a set of coupling constants. Cutoff functions are introduced to take into account the nonelementary nature of the particles in the model. These cutoff functions introduce a set of cutoff masses. The coupling constants, cutoff masses, and bare baryon masses are determined by fitting to a partial wave analysis of pion-nucleon elastic scattering up to a c.m. energy of $W=1550$ MeV.

Dynamical coupled channels calculation of pion and omega meson production

The dynamical coupled-channels approach developed at the Excited Baryon Analysis Center is extended to include the $\ensuremath{\omega}N$ channel to study \ensuremath{\pi}- and \ensuremath{\omega}-meson production induced by scattering pions and photons from the proton. Six intermediate channels, including $\ensuremath{\pi}N$, $\ensuremath{\eta}N$, $\ensuremath{\pi}\ensuremath{\Delta}$, $\ensuremath{\sigma}N$, $\ensuremath{\rho}N$, and $\ensuremath{\omega}N$, are employed to describe unpolarized and polarized data. Bare parameters in an effective hadronic Lagrangian are determined in a fit to the data for $\ensuremath{\pi}N\ensuremath{\rightarrow}\ensuremath{\pi}N$, $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\pi}N$, ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\omega}n$, and $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\omega}p$ reactions at center-of-mass energies from threshold to $W<2.0$ GeV. The $T$ matrix determined in these fits is used to calculate the photon beam asymmetry for \ensuremath{\omega}-meson production and the $\ensuremath{\omega}N\ensuremath{\rightarrow}\ensuremath{\omega}N$ total cross section and $\ensuremath{\omega}N$-scattering lengths. The calculated beam asymmetry is in good agreement with the observed in the range of energies near threshold to $W\ensuremath{\lesssim}2.0$ GeV.

Loop corrections and naturalness in a chiral effective field theory

The loop expansion is applied to a chiral effective hadronic Lagrangian; with the techniques of Infrared Regularization, it is possible to separate out the short-range contributions and to write them as local products of fields that are already present in our Lagrangian. (The appropriate field variables must be re-defined at each order in loops.) The corresponding parameters implicitly include short-range effects to all orders in the interaction, so these effects need not be calculated explicitly. The remaining (long-range) contributions that must be calculated are nonlocal and resemble those in conventional nuclear-structure calculations. Nonlinear isoscalar scalar ( σ ) and vector ( ω ) meson interactions are included, which incorporate many-nucleon forces and nucleon substructure. Calculations are carried out at the two-loop level to illustrate these techniques at finite nuclear densities and to verify that the coupling parameters remain natural when fitted to the empirical properties of equilibrium nuclear matter. Contributions from the ωN tensor coupling are also discussed.