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| CMS-PAS-HIN-17-008 | ||
| Measurement of the $\mathrm{B}_{s}^{0}$ meson nuclear modification factor in PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | ||
| CMS Collaboration | ||
| May 2018 | ||
| Abstract: The production cross sections of $\mathrm{B}_{s}^{0}$ mesons and charge conjugates are measured in pp and PbPb collisions via the exclusive decay channel $\mathrm{B}_{s}^{0}\to\mathrm{J}/\psi \phi\to\mu^{+}\mu^{-}\mathrm{K}^{+}\mathrm{K}^{-}$ at a center-of-mass energy ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 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 $\mathrm{B}_{s}^{0}$ meson in the range of 7 to 50 GeV/$c$ and is compared to the predictions of next-to-leading order perturbative calculations. $\mathrm{B}_{s}^{0}$ 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 pp production yield in the same kinematic region. The nuclear modification factor, comparing $\mathrm{B}_{s}^{0}$ meson yields in PbPb and pp collisions, was extracted and a comparison with the $\mathrm{B}^{+}$ mesons was made. An indication of less suppression in production yield for $\mathrm{B}_{s}^{0}$ mesons than for $\mathrm{B}^{+}$ mesons in the PbPb system is seen but the difference is not significant within the current experimental uncertainties. | ||
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These preliminary results are superseded in this paper, PLB 796 (2019) 168. The superseded preliminary plots can be found here. |
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| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in pp (left) and PbPb (right) collisions measured in $ | y | < $ 2.4 and in the $ {p_{\mathrm {T}}} $ region 7-15 GeV/$c$. |
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Figure 1-a:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in pp collisions measured in $ | y | < $ 2.4 and in the $ {p_{\mathrm {T}}} $ region 7-15 GeV/$c$. |
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Figure 1-b:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in PbPb collisions measured in $ | y | < $ 2.4 and in the $ {p_{\mathrm {T}}} $ region 7-15 GeV/$c$. |
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Figure 2:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in pp (left) and PbPb (right) collisions measured in $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ region 15-50 GeV/$c$. |
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Figure 2-a:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in pp collisions measured in $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ region 15-50 GeV/$c$. |
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Figure 2-b:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in PbPb collisions measured in $ | y | < $ 2.4 and in the ${p_{\mathrm {T}}}$ region 15-50 GeV/$c$. |
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Figure 3:
The $ {p_{\mathrm {T}}} $-differential production cross section of $ {\mathrm {B}_{s}^0} $ 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 [25,26,27] 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}_{s}^0} $ in pp collisions and the $ {p_{\mathrm {T}}} $-differential corrected yield of $ {\mathrm {B}_{s}^0} $ scaled by ${T_{\mathrm {AA}}}$ in PbPb collisions at $ {\sqrt {s}} = $ 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}_{s}^0} $ 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 global systematic uncertainty, represented as a grey box at $ {R_{\mathrm {AA}}} =1$, comprises the uncertainties in the integrated luminosity measurement and ${T_{\mathrm {AA}}}$ value. |
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Figure 4-a:
The $ {p_{\mathrm {T}}} $-differential production cross section of $ {\mathrm {B}_{s}^0} $ in pp collisions and the $ {p_{\mathrm {T}}} $-differential corrected yield of $ {\mathrm {B}_{s}^0} $ scaled by ${T_{\mathrm {AA}}}$ in PbPb collisions at $ {\sqrt {s}} = $ 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}_{s}^0} $ 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 global systematic uncertainty, represented as a grey box at $ {R_{\mathrm {AA}}} =1$, comprises the uncertainties in the integrated luminosity measurement and ${T_{\mathrm {AA}}}$ value. |
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Figure 5:
Nuclear modification factor $\rm {R_{\mathrm {AA}}} $ ratio between $ {\mathrm {B}_{s}^0} $ and $ {{\mathrm {B}^{+}}}$ measured in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 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 $\mathrm{B}_{s}^{0}$ mesons in both pp and nucleus-nucleus (PbPb) collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 5.02 TeV is presented. The $\mathrm{B}_{s}^{0}$ and $\overline{\mathrm{B}}_{s}^{0}$ 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, ${\mathrm{B}_{s}^{0}\to\mathrm{J}/\psi \phi\to\mu^{+}\mu^{-}\mathrm{K^{+}}\mathrm{K^{-}}} $. The nuclear modification factor of $\mathrm{B}_{s}^{0}$ is measured in ${p_{\mathrm{T}}}$ from 7 to 50 GeV/$c$. An indication of an enhancement of the $\mathrm{B}_{s}^{0}$/$\mathrm{B^{+}}$ ratio in PbPb with respect to pp collisions is observed. More precise measurements of the $\mathrm{B}_{s}^{0}$ and $\mathrm{B^{\pm}}$ mesons ${R_{\mathrm{AA}}}$ 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 | |
png pdf |
Additional Figure 1:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in pp (left) and PbPb (right) collisions measured in $ | y | < 2.4$ and in the $ {p_{\mathrm {T}}} $ region 7-50 GeV/$c$. |
png pdf |
Additional Figure 1-a:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in pp collisions measured in $ | y | < 2.4$ and in the $ {p_{\mathrm {T}}} $ region 7-50 GeV/$c$. |
png pdf |
Additional Figure 1-b:
Invariant mass distributions of $ {\mathrm {B}_{s}^0} $ and $ {\overline {\mathrm {B}_{s}^0}} $ candidates in PbPb collisions measured in $ | y | < 2.4$ and in the $ {p_{\mathrm {T}}} $ region 7-50 GeV/$c$. |
png pdf |
Additional Figure 2:
The nuclear modification factor $R_{\mathrm {AA}}$ of $ {\mathrm {B}_{s}^0}$ and $ {{\mathrm {B}^{+}}}$ [28] measured in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV from 7 to 50 GeV/$c$. Two theoretical calculations of $ {\mathrm {B}_{s}^0} $ $R_{\mathrm {AA}}$ are also shown for comparison: TAMU [45,46] and CUJET3.0 [47,48,49]. |
png pdf |
Additional Figure 3:
Nuclear modification factor $R_{\mathrm {AA}}$ ratio between $ {\mathrm {B}_{s}^0} $ and $ {{\mathrm {B}^{+}}}$ [28] 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 [45,46] and CUJET3.0 [47,48,49]. |
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