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Register a new userCharmonium decay widths in magnetized matter
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We study the partial decay widths of the charmonium states ($J/psi$, $psi(3686)$, $psi(3770)$, $chi_{c0}$, $chi_{c2}$) to $Dbar D$ ($D^+D^-$ or $D^0bar {D^0}$) in isospin asymmetric nuclear matter, in the presence of strong magnetic fields. The in-medium partial decay widths of charmonium states to $Dbar D$ are calculated within a light quark--antiquark pair creation model, namely the $^3P_0$ model, using the in--medium masses of the charmonia as well as $D$ and $bar D$ mesons in the magnetized nuclear matter obtained within a chiral effective model. The presence of a magnetic field leads to Landau quantization of the energy levels of the proton in the nuclear medium. The effects of magnetic field and isospin asymmetry on the charmonium decay widths to $Dbar D$ are found to be quite prominent. The effects of the anomalous magnetic moments have also been taken into consideration for obtaining the in-medium masses of these heavy flavour mesons, used to calculate the partial decay widths of the charmonium states. The medium modifications of the charmonium decay widths can have observable consequences on the production of the charmed mesons in high energy asymmetric heavy ion collision experiments.
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The in-medium partial decay widths of $Upsilon (4S) rightarrow Bbar B$ in magnetized asymmetric nuclear matter are studied using a field theoretic model for composite hadrons with quark/antiquark constituents. The medium modifications of the decay widths of $Upsilon (4S)$ to $Bbar B$ pair in magnetized matter, arise due to the mass modifications of the decaying $Upsilon (4S)$ as well as of the produced $B$ and $bar B$ mesons. The effects of the anomalous magnetic moments for the proton and neutron are taken into consideration in the present investigation. The presence of the external magnetic field is observed to lead to different mass modifications within the $B (B^+, B^0)$ as well as the $bar B (B^-, bar {B^0})$ doublets, even in isospin symmetric nuclear matter, due to the difference in the interactions of the proton and the neutron to the electromagnetic field. This leads to difference in the upsilon decay widths to the neutral ($B^0 bar {B^0}$) and the charged ($B^+ B^-$) pairs in the magnetized symmetric nuclear matter. The isospin asymmetry is observed to lead to quite different behaviours for the $Upsilon (4S)$ decay widths to the charged and neutral $Bbar B$. In the presence of the magnetic field, the Landau level contributions give rise to positive shifts in the masses of the charged $B$ and $bar B$ mesons. This leads to the decay of $Upsilon(4S)$ to the charged $B^+ B^-$ to be suppressed as compared to the neutral $Bbar B$ pair, especially at low densities. This may lead to suppression in the production of the charged $B^pm$ mesons as compared to the neutral $B^0$ and $bar {B^0}$ mesons at LHC and RHIC.
The decay widths of the charmonium states to $Dbar D$ in isospin asymmetric nuclear matter in the presence of a magnetic field are studied, using a field theoretical model for composite hadrons with quark/antiquark constituents. The medium modifications of these partial decay widths arise due to the changes in the masses of the decaying charmonium state and the produced $D$ and $bar D$ mesons in the magnetized hadronic matter, calculated within a chiral effective model. The decay widths are computed using the light quark--antiquark pair creation term of the free Dirac Hamiltonian in terms of the constituent quark field operators. The results of the present investigation are compared with the in-medium decay widths obtained within the $^3P_0$ model. Within the $^3P_0$ model, the charmonium decay widths are calculated using the creation of a light quark--antiquark pair in the $^3P_0$ state. In the presence of a magnetic field, the Landau level contributions give rise to positive shifts in the masses of the charged $D$ and $bar D$ mesons. This leads to the decay of charmonium to the charged $D^+ D^-$ to be suppressed as compared to the neutral $Dbar D$ pair in symmetric nuclear matter, whereas in asymmetric nuclear matter, the larger mass drop of the $D^+D^-$ pair, as compared to the $D^0 bar {D^0}$ pair leads to the production of charged open charm meson pairs to be enhanced as compared to the charmonium decay channel to $D^0 {bar {D^0}}$.
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 $Dbar D$ 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 $psi(3770) rightarrow Dbar D$ 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.
The partial decay widths of lowest lying negative parity baryons belonging to the 70-plet of SU(6) are analyzed in the framework of the 1/Nc expansion The channels considered are those with single pseudo-scalar meson emission. The analysis is carried out to sub-leading order in 1/Nc and to first order in SU(3) symmetry breaking. Conclusions about the magnitude of SU(3) breaking effects along with predictions for some unknown or poorly determined partial decay widths of known resonances are obtained.
The medium modifications of the open charm mesons ($D$ and $bar D$) are studied in isospin asymmetric nuclear matter in the presence of strong magnetic fields, using a chiral effective model. The mass modifications of these mesons in the effective hadronic model, arise due to their interactions with the protons, neutrons and the scalar mesons (non-strange isoscalar $sigma$, strange isoscalar, $zeta$ and non-strange isovector, $delta$), in the magnetized nuclear matter. In the presence of magnetic field, for the charged baryon, i.e., the proton, the number density as well as the scalar density have contributions due to the summation over the Landau energy levels. For a given value of the baryon density, $rho_B$, and isospin asymmetry, the scalar fields are solved self consistently from their coupled equations of motion. The modifications of the masses of the $D$ and $bar D$ mesons are calculated, from the medium modifications of the scalar fields and the nucleons. The effects of the anomalous magnetic moments of the nucleons on the masses of the open charm mesons are also investigated in the present work. The effects of isospin asymmetry as well as of the anomalous magnetic moments are observed to be prominent at high densities for large values of magnetic fields.
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