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| CMS-HIN-17-008 ; CERN-EP-2018-257 | ||
| Measurement of $\mathrm{B}^{0}_{\mathrm{s}}$ meson production in pp and PbPb collisions at $\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 5.02 TeV | ||
| CMS Collaboration | ||
| 6 October 2018 | ||
| Phys. Lett. B 796 (2019) 168 | ||
| Abstract: The production cross sections of $\mathrm{B}^{0}_{\mathrm{s}}$ mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel ${\mathrm{B}^{0}_{\mathrm{s}} \to \mathrm{J}/\psi \phi \to \mu^{+}\mu^{-}\mathrm{K^{+}}\mathrm{K^{-}}}$ at a centre-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range $| y | < $ 2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum (${p_{\mathrm{T}}}$) of the $\mathrm{B}^{0}_{\mathrm{s}}$ meson in the range of 7 to 50 GeV/$c$ and is compared to the predictions of perturbative QCD calculations. The $\mathrm{B}^{0}_{\mathrm{s}}$ production yield in PbPb collisions is measured in two ${p_{\mathrm{T}}}$ intervals, 7 to 15 and 15 to 50 GeV/$c$, and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor (${R_{\mathrm{AA}}} $) is found to be 1.5 $\pm$ 0.6 (stat) $\pm$ 0.5 (syst) for 7-15 GeV/$c$, and 0.87 $\pm$ 0.30 (stat) $\pm$ 0.17 (syst) for 15-50 GeV/$c$, respectively. Within current uncertainties, the results are consistent with models of strangeness enhancement and a suppression as observed for the $\mathrm{B^{+}}$ mesons. | ||
| Links: e-print arXiv:1810.03022 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Invariant mass distributions of $ {\mathrm {B}^0_\mathrm {s}} $ candidates in pp (left) and PbPb (right) collisions measured in the range $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ range of 7-15 GeV/$c$. The $\chi ^2$ divided by the number of degrees of freedom (nDOF) is also given. |
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Figure 1-a:
Invariant mass distributions of $ {\mathrm {B}^0_\mathrm {s}} $ candidates in pp collisions measured in the range $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ range of 7-15 GeV/$c$. The $\chi ^2$ divided by the number of degrees of freedom (nDOF) is also given. |
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Figure 1-b:
Invariant mass distributions of $ {\mathrm {B}^0_\mathrm {s}} $ candidates in PbPb collisions measured in the range $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ range of 7-15 GeV/$c$. The $\chi ^2$ divided by the number of degrees of freedom (nDOF) is also given. |
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Figure 2:
Invariant mass distributions of $ {\mathrm {B}^0_\mathrm {s}} $ candidates in pp (left) and PbPb (right) collisions measured in the range $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ range of 15-50 GeV/$c$. The $\chi ^2$ divided by the number of degrees of freedom (nDOF) is also given. |
png pdf |
Figure 2-a:
Invariant mass distributions of $ {\mathrm {B}^0_\mathrm {s}} $ candidates in pp collisions measured in the range $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ range of 15-50 GeV/$c$. The $\chi ^2$ divided by the number of degrees of freedom (nDOF) is also given. |
png pdf |
Figure 2-b:
Invariant mass distributions of $ {\mathrm {B}^0_\mathrm {s}} $ candidates in PbPb collisions measured in the range $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ range of 15-50 GeV/$c$. The $\chi ^2$ divided by the number of degrees of freedom (nDOF) is also given. |
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Figure 3:
The ${p_{\mathrm {T}}} $-differential production cross section of $ {\mathrm {B}^0_\mathrm {s}} $ in pp collisions at $ {\sqrt {s}} = $ 5.02 TeV in three ${p_{\mathrm {T}}}$ 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, 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 $\mathcal {B}$. The pp cross section is compared to FONLL calculations [28] represented by the colored yellow boxes with the heights indicating the theoretical uncertainty. |
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Figure 4:
(left) The ${p_{\mathrm {T}}} $-differential production cross section of $ {\mathrm {B}^0_\mathrm {s}} $ mesons in pp collisions and the ${p_{\mathrm {T}}} $-differential corrected yield of $ {\mathrm {B}^0_\mathrm {s}} $ mesons scaled by ${T_{\mathrm {AA}}}$ in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV in two ${p_{\mathrm {T}}}$ 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 ${T_{\mathrm {AA}}}$, $N_{\text {MB}}$, and $\mathcal {B}$. (right) The nuclear modification factor ${R_{\mathrm {AA}}}$ of $ {\mathrm {B}^0_\mathrm {s}} $ measured in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV from 7 to 50 GeV/$c$. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The ${{\mathrm {B}^{+}}}$ ${R_{\mathrm {AA}}}$ measurement [29] is also shown for comparison. The global systematic uncertainty, represented by colored boxes at ${R_{\mathrm {AA}}} =$ 1, comprises the uncertainties in the integrated luminosity measurement and ${T_{\mathrm {AA}}}$ value. Two theoretical calculations are also shown for comparison: TAMU [49,19] and CUJET3.0 [46,47,48]. The line width of the theoretical calculation from Refs. [49,19] represents the size of its statistical uncertainty. |
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Figure 4-a:
The ${p_{\mathrm {T}}} $-differential production cross section of $ {\mathrm {B}^0_\mathrm {s}} $ mesons in pp collisions and the ${p_{\mathrm {T}}} $-differential corrected yield of $ {\mathrm {B}^0_\mathrm {s}} $ mesons scaled by ${T_{\mathrm {AA}}}$ in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV in two ${p_{\mathrm {T}}}$ 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 ${T_{\mathrm {AA}}}$, $N_{\text {MB}}$, and $\mathcal {B}$. |
png pdf |
Figure 4-b:
The nuclear modification factor ${R_{\mathrm {AA}}}$ of $ {\mathrm {B}^0_\mathrm {s}} $ measured in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV from 7 to 50 GeV/$c$. The vertical bars (boxes) correspond to statistical (systematic) uncertainties. The ${{\mathrm {B}^{+}}}$ ${R_{\mathrm {AA}}}$ measurement [29] is also shown for comparison. The global systematic uncertainty, represented by colored boxes at ${R_{\mathrm {AA}}} =$ 1, comprises the uncertainties in the integrated luminosity measurement and ${T_{\mathrm {AA}}}$ value. Two theoretical calculations are also shown for comparison: TAMU [49,19] and CUJET3.0 [46,47,48]. The line width of the theoretical calculation from Refs. [49,19] represents the size of its statistical uncertainty. |
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Figure 5:
Nuclear modification factor $\mathrm {{R_{\mathrm {AA}}}}$ ratio between $ {\mathrm {B}^0_\mathrm {s}} $ and $ {{\mathrm {B}^{+}}}$ measured in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV from 7 to 50 GeV/$c$. Two theoretical calculations are also shown for comparison: TAMU [49,19], and CUJET3.0 [46,47,48]. |
| Tables | |
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Table 1:
Summary of systematic uncertainties in percentage (%) from each factor in pp and PbPb analyses. |
| Summary |
| The first measurement of the differential production cross section of $\mathrm{B}^{0}_{\mathrm{s}}$ mesons (including both charge conjugates) in both pp and PbPb collisions at a centre-of-mass energy of 5.02 TeV per nucleon pair is presented. The $\mathrm{B}^{0}_{\mathrm{s}}$ and ${\mathrm{\overline{B}}^0}s$ mesons are studied 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, ${\mathrm{B}^{0}_{\mathrm{s}} \to \mathrm{J}/\psi \phi \to \mu^{+}\mu^{-}\mathrm{K^{+}}\mathrm{K^{-}}} $. The nuclear modification factor ${R_{\mathrm{AA}}}$ of $\mathrm{B}^{0}_{\mathrm{s}}$ is measured in the transverse momentum range from 7 to 50 GeV/$c$, inclusively for 0-100% event centrality. An indication of an enhancement of the $\mathrm{B}^{0}_{\mathrm{s}}$/$\mathrm{B^{+}}$ ratio in PbPb with respect to pp collisions is seen. More precise measurements of the $\mathrm{B}^{0}_{\mathrm{s}}$ and $\mathrm{B^{\pm}}$ mesons ${R_{\mathrm{AA}}}$ with the upcoming high-luminosity LHC heavy ion runs could provide further constraints on the relevance of recombination, a marker of deconfined matter, for beauty hadron production, and unambiguous information about the mechanisms of beauty hadronisation in heavy ion collisions. |
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