Open Heavy flavor mesons in hot asymmetric strange hadronic matter -- A QCD sum rule approach

Abstract

The in-medium masses of the pseudoscalar open charm ($D$, $\bar D$, $D_s$ and $\bar {D_s}$) and open bottom ($B$, $\bar B$, $B_s$ and $\bar {B_s}$) mesons in hot asymmetric strange hadronic matter are studied within a QCD sum rule approach. These are computed using the medium modifications of the light quark condensates ($\langle{\bar{q_i}}{q_i}\rangle$, with $(q_i,i=1,2,3)\equiv(u,d,s)$), the gluon condensates and other operators in the operator product expansion upto mass dimension 5. Within a chiral SU(3) model, the quark condensates are obtained from the medium modifications of the non-strange and strange scalar-isoscalar fields ($\sigma$ and $\zeta$), and the scalar-isovector field, $\delta$, whereas, the gluon (scalar and twist-2) condensates are computed from the in-medium value of the dilaton field, $\chi$, which is incorporated within the chiral model to mimic the broken scale invariance of QCD. The splittings of the masses of the $D-\bar D$ ($B-\bar B)$, as well as $D_s-\bar {D_s} (B_s-\bar {B_s})$ in the hadronic medium are due to the odd part of the spectral function. For the strange-charm (strange-bottom) mesons ($(q_i,i=3)\equiv s$), the value of $\langle {q_i}^\dagger {q_i} \rangle$ dominates over the contributions from the other operators of the odd part of the spectral function. This is observed as opposite behaviour of the particle-antiparticle mass splittings with the mass of the particle to be larger (smaller) than the antiparticle mass in nuclear (hyperonic) matter. The density and isospin asymmetry effects are observed to be the dominant medium effects which might have observable consequences on the production of charmonia and open charm mesons, and, on the production ratios, $D^+/D^-$ and $D^0/\bar {D^0}$, in asymmetric heavy ion collisions in the CBM experiment at FAIR at the future facility at GSI.