No Arabic abstract
We investigate the in-medium masses of open charm mesons ($D$($D^0$, $D^+$), $bar{D}$($bar{D^0}$, $D^-$), $D_s$(${D_{s}}^+$, ${D_{s}}^-$)) and charmonium states ($J/psi$, $psi(3686)$, $psi(3770)$, $chi_{c0}$, $chi_{c2}$) in strongly magnetized isospin asymmetric strange hadronic matter using a chiral effective model. In the presence of the magnetic field, the number density and scalar density of charged baryons have contributions from Landau energy levels. The mass modifications of open charm mesons arise due to their interactions with nucleons, hyperons, and the scalar fields (the non-strange field $sigma$, strange field $zeta$ and isovector field $delta$) in the presence of the magnetic field. The mass modifications of the charmonium states arise from the variation of dilaton field ($chi$) in the magnetized medium, which simulates the gluon condensates of QCD. The in-medium mass of open charm mesons and charmonia are observed to decrease with an increase in baryon density, whereas the charged $D^+$, $D^-$, ${D_{s}}^+$ and ${D_{s}}^-$ mesons have additional positive mass shifts due to Landau quantization in the presence of the magnetic field. The effects of strangeness fraction are found to be more dominant for the $bar{D}$ mesons as compared to the $D$ mesons. The mass shifts of charmonia are observed to be larger in hyperonic medium compared to the nuclear medium.
The NA61/SHINE collaboration has recently published high precision data on production of $pi^pm$ and $K^pm$ mesons, protons, antiprotons and $Lambda$ hyperons in ${rm pp}$ interactions at 20, 31, 40, 80 and 158 GeV/c, and in ${rm pC}$ interactions at 31 GeV/c. The collaboration also presented experimental data on production of particles - $pi^pm$, $K^pm$, $p^pm$, $rho^0$, $omega$ and $K^{*0}$ in $pi^-{rm C}$ collisions at 158 and 350 GeV/c. The collaboration has compared these data with various Monte Carlo model calculations: UrQMD, EPOS, GiBUU, and others. All of the models have various problems. The latest version of the FTF (Fritiof) model of Geant4 solves most of these problems. In the FTF model, we have improved the fragmentation of quark-gluon strings with small masses and introduced dependencies of probabilities of strange mesons and baryon-antibaryon pairs creation on string masses. Due to these changes, we describe the data of the NA61/SHINE collaboration on particle production in ${rm pp, pC}$, and $pi^-{rm C}$ interactions. The improved Geant4 FTF model also well reproduces experimental data on inclusive cross sections of $Lambda, bar{Lambda}$ and $K^{0}$ production in antiproton-proton interactions at various energies. The modified FTF model allows one to simulate realistic processes with two particle productions - $bar{p}p rightarrow Lambda bar{Lambda}$, $bar{p}p rightarrow K^{+} K^{-}$, $bar{p}p rightarrow Lambda bar{Sigma}$, and $bar{p}p rightarrowSigma bar{Sigma}$, which will be studied in the future by the PANDA experiment at FAIR (GSI, Germany).
We calculate spatial correlation functions of in-medium mesons consisting of strange--anti-strange, strange--anti-charm and charm--anti-charm quarks in (2+1)-flavor lattice QCD using the highly improved staggered quark action. A comparative study of the in-medium modifications of mesons with different flavor contents is performed. We observe significant in-medium modifications for the $phi$ and $D_s$ meson channels already at temperatures around the chiral crossover region. On the other hand, for the $J/psi$ and $eta_c$ meson channels in-medium modifications remain relatively small around the chiral crossover region and become significant only above 1.3 times the chiral crossover temperature.
In this presentation I explain our framework for dynamically generating resonances from the meson meson interaction. Our model generates many poles in the T-matrix which are associated with known states, while at the same time new states are predicted.
The mass modifications of the open charm ($D$ and $D^*$) mesons, and their effects on the decay widths $D^*rightarrow Dpi$ as well as of the charmonium state, $Psi(3770)$ to open charm mesons ($Psi(3770)rightarrow Dbar D$), are investigated in the presence of strong magnetic fields. These are studied accounting for the mixing of the pseudoscalar ($P$) and vector ($V$) mesons ($D-D^*$, $eta_c-Psi(3770)$ mixings), with the mixing parameter, $g_{PV}$ of a phenomenological three-point ($PVgamma$) vertex interaction determined from the observed radiative decay width of $Vrightarrow Pgamma$. For charged $D-D^*$ mixing, this parameter is dependent on the magnetic field, because of the Landau level contributions to the vacuum masses of these mesons. The masses of the charged $D$ and $D^*$ mesons modified due to $PV$ mixing, in addition, have contributions from the lowest Landau levels in the presence of a strong magnetic field. The effects of the magnetic field on the decay widths are studied using a field theoretic model of composite hadrons with quark (and antiquark) consittuents. The parameter for the charged $D-D^*$ mixing is observed to increase appreciably with increase in the magnetic field. This leads to dominant modifications to their masses, and hence the decay widths of charged $D^*rightarrow Dpi$ as well as $Psi(3770)rightarrow D^+D^-$ at large values of the magnetic field. The modifications of the masses and decay widths of the open and hidden charm mesons in the presence of strong magnetic fields should have observable consequences on the production of the open charm ($D$ and $D^*$) mesons as well as of the charmonium states resulting from non-central ultrarelativistic heavy ion collision experiments.
We discuss the stability of hidden and open heavy-flavor hadronic states made of either two or three mesons. References are made in passing to studies regarding two and three-body systems containing baryons. We perform a comparative study analyzing the results in terms of quark and hadron degrees of freedom. Compact and molecular states are found to exist in very specific situations. We estimate the decay width for the different scenarios: weak decays for bound states by the strong interaction, and strong decays for hadronic resonances above a decay threshold. The experimental observation of narrow hadrons lying well above their lowest decay threshold is theoretically justified.