Magnetic Field Effects on In-Medium ϒ Dissociation

Abstract

Abstract. The electromagnetic fields during relativistic heavy ion collisions are calculated using a simple model which characterises the emerging quark-gluon medium by its conductivity only. An estimate of the average magnetic field strength experienced by the bb mesons produced in the collision is made. In a sufficiently strong magnetic field, the individual spins of bb mesons can align with the field leading to quantum mixing of the singlet and triplet spin configurations. The extent of this intermixture, however, is found to be negligible at field strengths occurring in heavy ion collisions at LHC energies.

Bottomia physics at RHIC and LHC

“…The p T -dependence is rather flat and at 2.76 TeV in reasonable agreement with the available CMS data [7]. There is no rapidity dependence in our model, both minimum bias and centrality dependent yields are flat as functions of y.…”

“…1 for PbPb, and [7] for UU. The parameters for the density distributions of the lead and uranium ions are taken from [11].…”

“…This takes into account the red-or blueshifted temperatures and also correctly describes the nonexistence of bound states once the effective temperature in the blueshifted region exceeds the dissociation temperature, see [7] for more details. The p T -dependence is rather flat and at 2.76 TeV in reasonable agreement with the available CMS data [7].…”

“…To estimate the initial populations N i AA,nl of the six states, we consider the measured final populations N f pp,nl of the three Υ(nS)-states in pp collisions at the same energy and calculate the decay cascade [9] backwards to obtain the initial populations in pp, N i pp,nl [7] These are then scaled by the number of binary collisions N coll yielding the initial populations in the heavy-ion case. When the suppression factors are calculated, the number of binary collisions cancels out.…”

Hadron production and ϒ suppression at the LHC

“…It is very relevant to include at all impact parameters the corona zone where the temperature never rises above the critical value so that none of the QGP dissociation mechanisms play a role there, leading to an occupation of the excited states even in more central collisions where the excited states melt in the high-temperature region due to screening. In the corona, additional hadronic suppression that is mostly due to collisions with pions -which we have investigated separately -may occur [20]. Once the centrality-dependent suppression in the hot fireball and in the corona is established, the bottomia states de-excite in a feed-down cascade before being detected through the emission of μ + μ − pairs, with a branching ratio of approximately 2.48% for the 1S state, 1.93% for the 2S state, and 2.18% for the 3S state.…”