Production cross sections of charm-beauty mesons in proton-nucleus and nucleus-nucleus collisions at LHC

TL;DR

The paper addresses the production of B_c mesons, specifically the 1S and 1P states, in pp, pA, and AA collisions at LHC and RHIC energies. Using NRQCD factorization with QCD factorization and LO accuracy, it computes cross sections and kinematic distributions while incorporating nuclear PDFs to account for shadowing, and it includes both gluon fusion and quark-antiquark annihilation subprocesses. The study extends prior work by including all 1P states, evaluating their cascades to the ground state, and providing nuclear modification factors R_pA and R_AA across multiple collision systems, energies, and nuclei. The results offer large-scale LO baselines for RUN III, highlight the sensitivity to heavy-quark masses and factorization scales, and outline implications for identifying undiscovered B_c states and testing NRQCD in heavy-ion environments. The work also lays the groundwork for improved precision with future NLO calculations.

Abstract

In this work, we calculate the production cross sections of the 1S and 1P states of the $B_{c}$ meson for proton-nucleus and nucleus-nucleus colliding beam experiments at LHC and RHIC. We provide estimates for the Au nucleus at RHIC energies and for the Pb and Xe nuclei at LHC energies. Previous estimates of these cross sections have ignored quark anti-quark annihilation diagrams and are confined to S states for Pb and Au nuclei. The cross sections of the P states are also equally important as these states lie below the BD threshold and cascade into $B_{c}$ ground states with 100\% probability. In addition to calculating the $p_{T}$, rapidity, and pseudo-rapidity distributions of the cross sections, we also determine the nuclear modification factors $R_{pA}$ and $R_{AA}$ for $A=\textrm{Pb}$, $\textrm{Xe}$, and $\textrm{Au}$. The results provide a baseline for the upcoming experimental studies of $B_{c}$ mesons in pp, pA, and AA collisions in RUN III of LHC and could help develop experimental strategies for identification of hitherto undiscovered states of the $B_{c}$ meson.

Figures (15)

• Figure 1: Diagramatic representation of production of $B_{c}$ meson through partonic interaction $ij\rightarrow B_{c}X$ in a heavy-ion collision.
• Figure 2: Breakdown of all systematic differences between our results and those of Ref. Chang:2005bf, in which CTEQ6L PDF set is used, at $\sqrt{S}=14$ TeV, and $\left\vert R(0)\right\vert ^{2}=1.54$ GeV$^{3}$. The difference due to numerical implementation is at most 5%.
• Figure 3: Variation of the production cross sections of the 1S and 1P states of the $B_{c}^{+}$ meson for p-Pb (left), p-Xe (middle), and p-Au (right) collisions with factorization scale $\mu$, varied from $0.25\mu_{F}$ to $4\mu_{F}$.
• Figure 4: Variation of the production cross sections of the 1S and 1P states of the $B_{c}^{+}$ meson for Pb-Pb (left), Xe-Xe (middle), and Au-Au (right) collisions with factorization scale $\mu$, varied from $0.25\mu_{F}$ to $4\mu_{F}$.
• Figure 5: $p_{T}$ distributions of the 1S and 1P states of the $B_{c}^{+}$ meson for p-Pb (left), p-Xe (middle), and p-Au (right) collisions at $\sqrt{S_{pA}}=8.16$, 8.3, 0.2 TeV, respectively.