Measurement of the total and differential inclusive B+ hadron cross sections in pp collisions at sqrt(s) = 13 TeV

TL;DR

This work presents the first CMS measurement of inclusive B+ hadron production in pp collisions at 13 TeV using the B+ -> J/psi K+ decay with J/psi -> mu+ mu-. It uses an extended unbinned likelihood approach to extract signal yields from invariant-mass fits, combined with MC- and data-driven efficiency corrections to determine differential cross sections in pT^B and y^B, and compares results to FONLL and PYTHIA predictions. The findings show overall agreement with theory within uncertainties, with 13 TeV/7 TeV ratios favoring higher values than predicted. Together, these results provide a stringent test of perturbative QCD for heavy-flavor production at the LHC's 13 TeV run and establish a cross-check channel for future analyses.

Abstract

The differential cross sections for inclusive production of B+ hadrons are measured as a function of the B+ transverse momentum pT[B] and rapidity y[B] in pp collisions at a centre-of-mass energy of 13 TeV, using data collected by the CMS experiment that correspond to an integrated luminosity of 49.4 inverse picobarns. The measurement uses the exclusive decay channel B+ to J/psi K+, with J/psi mesons that decay to a pair of muons. The results show a reasonable agreement with theoretical calculations within the uncertainties.

Figures (4)

• Figure 1: Invariant mass distribution of ${\mathrm{B}^{+}} \to {J}\space/\space\psi\xspace \mathrm{K^+}$ candidates, integrated over the phase-space region of $10 \le p_{\mathrm{T}}\xspace^{{\mathrm{B}}} < 17 \,\text{Ge\spaceV}\xspace$ and $\lvert y^{{\mathrm{B}}} \rvert < 1.45$, and of $17 \le p_{\mathrm{T}}\xspace^{{\mathrm{B}}} < 100 \,\text{Ge\spaceV}\xspace$ and $\lvert y^{{\mathrm{B}}} \rvert < 2.1$. The solid curve shows the result of the fit. The shaded and hatched areas represent, respectively, the ${J}\space/\space\psi\xspace \mathrm{K^+}$ signal and the ${J}\space/\space\psi\xspace \pi^+$ component, while the dashed and dotted curves represent the combinatorial and misreconstructed ${\mathrm{B}} \to {J}\space/\space\psi\xspace + \text{hadrons}$ backgrounds, respectively.
• Figure 2: Invariant mass distributions of the ${\mathrm{B}^{+}} \to {J}\space/\space\psi\xspace \mathrm{K^+}$ candidates in the regions of (a) $17 \le p_{\mathrm{T}}\xspace^{{\mathrm{B}}} < 24 \,\text{Ge\spaceV}\xspace$, $\lvert y^{{\mathrm{B}}} \rvert < 2.1$, and (b) $10 \le p_{\mathrm{T}}\xspace^{{\mathrm{B}}} < 100 \,\text{Ge\spaceV}\xspace$, $0.4 \le \lvert y^{{\mathrm{B}}} \rvert < 0.6$. The solid curve shows the result of the fit. The shaded (hatched) area represents the signal (${\mathrm{B}^{+}} \to {J}\space/\space\psi\xspace \pi^+$) component, while the dashed and dotted curves represent the combinatorial and misreconstructed ${\mathrm{B}} \to {J}\space/\space\psi\xspace + \text{hadrons}$ background components, respectively.
• Figure 3: ${\mathrm{B}^{+}}$ differential production cross sections (a) ${d}\sigma/{d}p_{\mathrm{T}}\xspace^{{\mathrm{B}}}$ for $\lvert y^{{\mathrm{B}}} \rvert < 1.45$ or $\lvert y^{{\mathrm{B}}} \rvert < 2.1$, and (b) ${d}\sigma/{d} y^{{\mathrm{B}}}$ for $10 < p_{\mathrm{T}}\xspace^{{\mathrm{B}}} <100 \,\text{Ge\spaceV}\xspace$ or $17 < p_{\mathrm{T}}\xspace^{{\mathrm{B}}} <100 \,\text{Ge\spaceV}\xspace$, at $\sqrt{s} = 13\,\text{Te\spaceV}\xspace$ (squares, this measurement). The previous CMS measurements from $\sqrt{s}=7\,\text{Te\spaceV}\xspace$ data Khachatryan:2011mk (circles) are also presented as a function of $p_{\mathrm{T}}\xspace^{{\mathrm{B}}}$ ($y^{{\mathrm{B}}}$), scaled to the phase-space region of $\lvert y^{{\mathrm{B}}} \rvert < 2.1$ or $\lvert y^{{\mathrm{B}}} \rvert < 1.45$ ($10 < p_{\mathrm{T}}\xspace^{{\mathrm{B}}} <100 \,\text{Ge\spaceV}\xspace$ or $17 < p_{\mathrm{T}}\xspace^{{\mathrm{B}}} <100 \,\text{Ge\spaceV}\xspace$). The vertical bars show the total uncertainty in the measured cross sections, and the horizontal bars represent the bin width. The calculations from FONLL and pythia are shown as shaded boxes and dashed lines, respectively. The bottom panels display the ratio of the data at 13$\,\text{Te\spaceV}$ to the FONLL predictions (points) and the ratios of the pythia to the FONLL calculations (dashed lines), with the shaded region displaying the uncertainties in the FONLL predictions.
• Figure 4: Ratios of ${\mathrm{B}^{+}}$ differential production cross sections at $\sqrt{s}=13\,\text{Te\spaceV}\xspace$ and at $\sqrt{s}=7\,\text{Te\spaceV}\xspace$ as (a) a function of $p_{\mathrm{T}}\xspace^{{\mathrm{B}}}$ for $\lvert y^{{\mathrm{B}}} \rvert < 1.45$ or $\lvert y^{{\mathrm{B}}} \rvert < 2.1$ and (b) as a function of $\lvert y^{{\mathrm{B}}} \rvert$ for $10 < p_{\mathrm{T}}\xspace^{{\mathrm{B}}} <100 \,\text{Ge\spaceV}\xspace$ or $17 < p_{\mathrm{T}}\xspace^{{\mathrm{B}}} <100 \,\text{Ge\spaceV}\xspace$. The vertical bars show the total uncertainty in the measured ratios of the cross sections, and the horizontal bars represent the bin width. The calculations from FONLL and pythia are shown as shaded boxes and dashed lines, respectively.