Open bottom mesons in hot asymmetric hadronic medium
  The in-medium masses and optical potentials of $B$ and ${\bar B}$ mesons are studied in an isospin asymmetric, strange, hot and dense hadronic environment using a chiral effective model. The chiral $SU(3)$ model originally designed for the light quark sector, is generalized to include the heavy quark sector ($c$ and $b$) to derive the interactions of the $B$ and ${\bar B}$ mesons with the light hadrons. Due to large mass of bottom quark, we use only the empirical form of these interactions for the desired purpose, while treating the bottom degrees of freedom to be frozen in the medium. Hence, all medium effects are due to the in-medium interaction of the light quark content of these open-bottom mesons. Both $B$ and $\bar B$ mesons are found to experience net attractive interactions in the medium, leading to lowering of their masses in the medium. The mass degeneracy of particles and antiparticles, ($B^+$, $B^-$) as well as ($B^0$, $\bar {B^0}$), is observed to be broken in the medium, due to equal and opposite contributions from a vectorial Weinberg-Tomozawa interaction term. Addition of hyperons to the medium lowers further the in-medium mass for each of these four mesons, while a non-zero isospin asymmetry is observed to break the approximate mass degeneracy of each pair of isospin doublets. These medium effects are found to be strongly density dependent, and bear a considerably weaker temperature dependence. The results obtained in the present investigation are compared to predictions from the quark-meson coupling model, heavy meson effective theory, and the QCD Sum Rule approach. 
Divakar Pathak and Amruta Mishra
nucl-th hep-ph