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CMS-PAS-HIN-17-008
Measurement of the B0s meson nuclear modification factor in PbPb collisions at sNN= 5.02 TeV
Abstract: The production cross sections of B0s mesons and charge conjugates are measured in pp and PbPb collisions via the exclusive decay channel B0sJ/ψϕμ+μK+K at a center-of-mass energy sNN= 5.02 TeV per nucleon pair and within the rapidity range (|y|< 2.4) using the CMS detector at the LHC. The proton-proton (pp) measurement is performed as a function of transverse momentum of the B0s meson in the range of 7 to 50 GeV/c and is compared to the predictions of next-to-leading order perturbative calculations. B0s production yield in PbPb collisions is measured in two pT intervals, 7 to 15 and 15 to 50 GeV/c, and compared to the pp production yield in the same kinematic region. The nuclear modification factor, comparing B0s meson yields in PbPb and pp collisions, was extracted and a comparison with the B+ mesons was made. An indication of less suppression in production yield for B0s mesons than for B+ mesons in the PbPb system is seen but the difference is not significant within the current experimental uncertainties.
Figures & Tables Summary Additional Figures References CMS Publications
Figures

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Figure 1:
Invariant mass distributions of B0s and ¯B0s candidates in pp (left) and PbPb (right) collisions measured in |y|< 2.4 and in the pT region 7-15 GeV/c.

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Figure 1-a:
Invariant mass distributions of B0s and ¯B0s candidates in pp collisions measured in |y|< 2.4 and in the pT region 7-15 GeV/c.

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Figure 1-b:
Invariant mass distributions of B0s and ¯B0s candidates in PbPb collisions measured in |y|< 2.4 and in the pT region 7-15 GeV/c.

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Figure 2:
Invariant mass distributions of B0s and ¯B0s candidates in pp (left) and PbPb (right) collisions measured in |y|< 2.4 and in the pT region 15-50 GeV/c.

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Figure 2-a:
Invariant mass distributions of B0s and ¯B0s candidates in pp collisions measured in |y|< 2.4 and in the pT region 15-50 GeV/c.

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Figure 2-b:
Invariant mass distributions of B0s and ¯B0s candidates in PbPb collisions measured in |y|< 2.4 and in the pT region 15-50 GeV/c.

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Figure 3:
The pT-differential production cross section of B0s in pp collisions at s= 5.02 TeV in three pTintervals from 7 to 50 GeV/c. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The systematic uncertainty boxes here include both the correlated and uncorrelated contributions added in quadrature. The global systematic uncertainty, listed in the legend and not included in the point-to-point uncertainties, comprises the uncertainties in the integrated luminosity measurement and in the branching fraction B. The pp cross section is compared to FONLL calculations [25,26,27] represented by the colored yellow boxes with the heights indicating the theoretical uncertainty.

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Figure 4:
(Left) The pT-differential production cross section of B0s in pp collisions and the pT-differential corrected yield of B0s scaled by TAA in PbPb collisions at s= 5.02 TeV in two pT intervals from 7 to 50 GeV/c. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The systematic uncertainty boxes here include both the correlated and uncorrelated contributions added in quadrature. The global systematic uncertainty comprises the uncertainties in TAA, NMB, and B. (Right) The nuclear modification factor RAA of B0s measured in PbPb collisions at sNN= 5.02 TeV from 7 to 50 GeV/c. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The global systematic uncertainty, represented as a grey box at RAA=1, comprises the uncertainties in the integrated luminosity measurement and TAA value.

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Figure 4-a:
The pT-differential production cross section of B0s in pp collisions and the pT-differential corrected yield of B0s scaled by TAA in PbPb collisions at s= 5.02 TeV in two pT intervals from 7 to 50 GeV/c. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The systematic uncertainty boxes here include both the correlated and uncorrelated contributions added in quadrature. The global systematic uncertainty comprises the uncertainties in TAA, NMB, and B.

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Figure 4-b:
The nuclear modification factor RAA of B0s measured in PbPb collisions at sNN= 5.02 TeV from 7 to 50 GeV/c. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The global systematic uncertainty, represented as a grey box at RAA=1, comprises the uncertainties in the integrated luminosity measurement and TAA value.

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Figure 5:
Nuclear modification factor RAA ratio between B0s and B+ measured in PbPb collisions at sNN= 5.02 TeV from 7 to 50 GeV/c
Tables

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Table 1:
Summary of systematic uncertainties from each factor in pp analysis. All the value is shown in percentage.
Summary
In summary, the first measurement of the differential production cross section of B0s mesons in both pp and nucleus-nucleus (PbPb) collisions at sNN= 5.02 TeV is presented. The B0s and ¯B0s mesons are measured with the CMS detector at the LHC in the rapidity range |y|<2.4 via the reconstruction of one of their exclusive hadronic decay channels, B0sJ/ψϕμ+μK+K. The nuclear modification factor of B0s is measured in pT from 7 to 50 GeV/c. An indication of an enhancement of the B0s/B+ ratio in PbPb with respect to pp collisions is observed. More precise measurements of the B0s and B± mesons RAA with the coming high-statistics LHC heavy ion runs will provide further constraints on the relevance of beauty recombination in heavy ion collisions.
Additional Figures

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Additional Figure 1:
Invariant mass distributions of B0s and ¯B0s candidates in pp (left) and PbPb (right) collisions measured in |y|<2.4 and in the pT region 7-50 GeV/c.

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Additional Figure 1-a:
Invariant mass distributions of B0s and ¯B0s candidates in pp collisions measured in |y|<2.4 and in the pT region 7-50 GeV/c.

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Additional Figure 1-b:
Invariant mass distributions of B0s and ¯B0s candidates in PbPb collisions measured in |y|<2.4 and in the pT region 7-50 GeV/c.

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Additional Figure 2:
The nuclear modification factor RAA of B0s and B+ [28] measured in PbPb collisions at sNN= 5.02 TeV from 7 to 50 GeV/c. Two theoretical calculations of B0s RAA are also shown for comparison: TAMU [45,46] and CUJET3.0 [47,48,49].

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Additional Figure 3:
Nuclear modification factor RAA ratio between B0s and B+ [28] measured in PbPb collisions at sNN= 5.02 TeV from 7 to 50 GeV/c. Two theoretical calculations are also shown for comparison: TAMU [45,46] and CUJET3.0 [47,48,49].
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