Studies of beauty hadron and non-prompt charm hadron production in pp collisions at $\sqrt{s}$=13 TeV within a transport model approach

TL;DR

We address how beauty and non-prompt charm production in $pp$ collisions at $\sqrt{s}=13$ TeV reflect heavy-quark production and hadronization dynamics. Using AMPT with PYTHIA8 initial conditions, the authors tune the beauty quark mass to $m_b=6.6\ \mathrm{GeV}/c^2$ and apply a flavor-dependent coalescence parameter $r_{BM}^b=1.2$ to reproduce $b\bar{b}$ cross sections and beauty baryon-to-meson ratios, achieving reasonable agreement with beauty-hadron and non-prompt charm data. They analyze $p_T$ and multiplicity dependencies of beauty and non-prompt charm observables, showing that multiplicity trends are sensitive to flavor-dependent coalescence and that non-prompt charm can probe heavy-quark hadronization in small systems. The work provides a unified transport-hadronization framework for heavy quarks in small systems and highlights non-prompt observables as key constraints for heavy-flavor coalescence and transport models.

Abstract

In high-energy proton proton ($pp$) collisions at the LHC, non-prompt charm hadrons, originating from beauty hadron decays, provide a valuable probe for beauty quark dynamics, particularly at low transverse momentum where direct beauty measurements are challenging. We employ A Multi-Phase Transport Model (AMPT) of string melting version coupled with PYTHIA8 initial conditions to study the beauty hadron and non-prompt charm hadron productions in $pp$ collisions at $\sqrt{s} = 13$ TeV. In this work, the beauty quark mass during the generation stage has been increased to reproduce the measured $b\bar{b}$ cross section, and a beauty flavor specific coalescence parameter $r_{BM}^b$ is introduced to match LHCb measurements of beauty baryon to meson ratios. With these refinements, AMPT achieves a reasonable agreement with experimental data on beauty hadron yields and non-prompt charm hadron production from ALICE and LHCb. We present the transverse momentum and multiplicity dependence of non-prompt to prompt charm hadron ratios, providing new insights into the interplay between beauty quark production and hadronization process. We emphasize that the multiplicity dependence of the non-prompt to prompt charm hadron productions can be useful to constrain the flavor dependences of the coalescence dynamics. This work establishes a unified framework for future studies of heavy quark transport and collective flow behavior in small collision systems.

Figures (11)

• Figure 1: $y$ (left) and $\eta$ (right) distribution of the $b\bar{b}$ production cross section in $pp$ collisions at $\sqrt{s}=13$ TeV. The red and blue curves represent results generated by PYTHIA8 with the $b$ quark effective mass $m_b=4.8$ and $m_b=6.6$ GeV$/c^2$, respectively. Experimental data from ALICE ALICE:2024xln and LHCb LHCb:2016qpe are shown in black open and solid markers for $y$ and $\eta$, respectively.
• Figure 2: The $p_{T}$-differential cross section of beauty hadrons in $pp$ collisions at $\sqrt{s}=13$ TeV on mid-rapidity ($|y|<0.5$, panel (a)) and forward rapidity ($2<y<4.5$, panel (b)), and as a function of $y$ for $0<p_T<40$ GeV$/c$ (panel (c)). The black, red, blue, and green lines show AMPT results for $B^0$, $B^+$, $B_s$, and $\Lambda_b^0$, respectively. Solid and open black markers indicate $B^+$ results from LHCb LHCb:2017vec and ALICE ALICE:2024xln. The ALICE data are obtained by scaling the measured $b\bar{b}$ cross section with a fragmentation fraction of 0.399 DELPHI:2011aa.
• Figure 3: The $\Lambda_b^0/B^0$ ratios in $pp$ collisions at $\sqrt{s}=13$ TeV on forward-$y$ as a function of $p_T$ (a) and multiplicity (b). The red line and black points represent the AMPT and LHCb results LHCb:2023wbo, respectively. The vertical error bars on the LHCb points represent the quadratic sum of statistical and systematic uncertainties, and the boxes indicate global uncertainties associated with branching fractions.
• Figure 4: Double-differential cross section of non-prompt $c$-hadrons in $pp$ collisions at $\sqrt{s}=13$ TeV at mid-$y$, as a function of $p_T$. The $D^0$, $D^+$, $D_s^+$, and $\Lambda_c^+$ are shown in black, red, blue, and green, respectively. The $D_s^+$ and $\Lambda_c^+$ results were scaled by factors of 1/2 and 1/10 to allow better visual comparison. Lines represent AMPT results, while data points represent ALICE results ALICE:2024xlnALICE:2023wbx.
• Figure 5: Ratios of $D^+/D^0$ (left) and $D_s^+/(D^0+D^+)$ (right) in $pp$ collisions at $\sqrt{s}=13$ TeV within $|y|<0.5$ as a function of $p_T$. Black and red represent prompt and non-prompt particles, respectively. The lines represent AMPT results, while the points correspond to ALICE results ALICE:2024xlnALICE:2023sgl.