CMS-PAS-HIN-22-001

CMS-PAS-HIN-22-001
Measurement of the B$^{+}$ differential cross section as a function of transverse momentum and multiplicity in pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV
CMS Collaboration
13 September 2023

Abstract: We present the measurement of the B$ ^+ $ meson production cross section with respect to the transverse momentum inclusively and, for the first time, in different charged particle multiplicities, in proton-lead collisions at a per nucleon center-of-mass energy of 8.16 TeV. The data were collected by the CMS detector during 2016 and correspond to an integrated luminosity of 175 nb$ ^{-1} $. The measurement uses the exclusive decay channel $ \mathrm{B}^{+}\!\to\! \mathrm{J}/\psi K^{+} $. The inclusive results show a good agreement with the FONLL calculations.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Reconstructed $ \mathrm{J}/\psi \mathrm{K^+} $ invariant mass distribution for B$^{+}$ meson candidates with 3 $ < p_{\mathrm{T}} < $ 50 GeV, in events with $ N_{\mathrm{trk}}^{\mathrm{corrected}} $ in the ranges 2 $ < N_{\mathrm{trk}}^{\mathrm{corrected}} < $ 60 (left) and 110 $ < N_{\mathrm{trk}}^{\mathrm{corrected}} < $ 250 (right). The result of the fit described in the text is also shown.
png pdf	Figure 1-a: Reconstructed $ \mathrm{J}/\psi \mathrm{K^+} $ invariant mass distribution for B$^{+}$ meson candidates with 3 $ < p_{\mathrm{T}} < $ 50 GeV, in events with $ N_{\mathrm{trk}}^{\mathrm{corrected}} $ in the ranges 2 $ < N_{\mathrm{trk}}^{\mathrm{corrected}} < $ 60 (left) and 110 $ < N_{\mathrm{trk}}^{\mathrm{corrected}} < $ 250 (right). The result of the fit described in the text is also shown.
png pdf	Figure 1-b: Reconstructed $ \mathrm{J}/\psi \mathrm{K^+} $ invariant mass distribution for B$^{+}$ meson candidates with 3 $ < p_{\mathrm{T}} < $ 50 GeV, in events with $ N_{\mathrm{trk}}^{\mathrm{corrected}} $ in the ranges 2 $ < N_{\mathrm{trk}}^{\mathrm{corrected}} < $ 60 (left) and 110 $ < N_{\mathrm{trk}}^{\mathrm{corrected}} < $ 250 (right). The result of the fit described in the text is also shown.
png pdf	Figure 2: (Left) B$^{+}$ differential cross section $ \mathrm{d}\sigma/\mathrm{d}p_{\mathrm{T}} $ in $ p_{\mathrm{T}} $ bins. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The global systematic uncertainty, not included in the data points, comprises the uncertainties in the integrated luminosity measurement and the B meson branching fractions. Results are compared to FONLL calculations, scaled by the number of binary NN collisions, represented by squares. The yellow boxes represent the theoretical uncertainties from FONLL [13,14,15]. (Right) B$^{+}$ differential cross section shown in $ p_{\mathrm{T}} $ bins divided into classes of reconstructed track multiplicity. The vertical bars represent the total uncertainties.
png pdf	Figure 2-a: (Left) B$^{+}$ differential cross section $ \mathrm{d}\sigma/\mathrm{d}p_{\mathrm{T}} $ in $ p_{\mathrm{T}} $ bins. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The global systematic uncertainty, not included in the data points, comprises the uncertainties in the integrated luminosity measurement and the B meson branching fractions. Results are compared to FONLL calculations, scaled by the number of binary NN collisions, represented by squares. The yellow boxes represent the theoretical uncertainties from FONLL [13,14,15]. (Right) B$^{+}$ differential cross section shown in $ p_{\mathrm{T}} $ bins divided into classes of reconstructed track multiplicity. The vertical bars represent the total uncertainties.
png pdf	Figure 2-b: (Left) B$^{+}$ differential cross section $ \mathrm{d}\sigma/\mathrm{d}p_{\mathrm{T}} $ in $ p_{\mathrm{T}} $ bins. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The global systematic uncertainty, not included in the data points, comprises the uncertainties in the integrated luminosity measurement and the B meson branching fractions. Results are compared to FONLL calculations, scaled by the number of binary NN collisions, represented by squares. The yellow boxes represent the theoretical uncertainties from FONLL [13,14,15]. (Right) B$^{+}$ differential cross section shown in $ p_{\mathrm{T}} $ bins divided into classes of reconstructed track multiplicity. The vertical bars represent the total uncertainties.

Tables
png pdf	Table 1: Fraction of the full event sample for each multiplicity class. The last two columns show the observed and corrected multiplicities, respectively, of charged particles with $ \|y\| < $ 2.4 and $ p_{\mathrm{T}} > $ 0.4 GeV. Systematic uncertainties are given for the corrected multiplicities, while statistical uncertainties are negligible.
png pdf	Table 2: Summary table of the $ p_{\mathrm{T}} $ differential cross sections of B$^{+}$ in pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV.

Summary

In summary, the B$^{+}$ meson production differential cross section has been measured as a function of the meson transverse momentum ($ p_{\mathrm{T}} $), $ \mathrm{d}\sigma/\mathrm{d}p_{\mathrm{T}} $, in proton-lead (pPb) collisions at a a per nucleon center-of-mass energy of $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 8.16 TeV, using an integrated luminosity of 175 nb$^{-1}$. The exclusive $ {\mathrm{B}^{+}}\!\to\! \mathrm{J}/\psi \mathrm{K^+} $ decay channel was used to reconstruct the B$^{+}$ mesons. The inclusive measurement is in excellent agreement with the FONLL predictions. Finally, the dependence of cross section on multiplicity classes has been measured for the first time in pPb collisions. This serves as a foundational result for potential future studies on medium effects, concerning b quark production in high-multiplicity events in pPb collisions.

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