CMS-BPH-21-001

CMS-BPH-21-001 ; CERN-EP-2022-248
Measurement of the dependence of the hadron production fraction ratio $ f_\mathrm{s}/f_\mathrm{u} $ on B meson kinematic variables in proton-proton collisions at $ \sqrt{s} = $ 13 TeV
CMS Collaboration
5 December 2022
Phys. Rev. Lett. 131 (2023) 121901
Abstract: The dependence of the ratio between the $ \mathrm{B}_{\mathrm{s}}^{0} $ and $ {\mathrm{B}^{+}} $ hadron production fractions, $ f_\mathrm{s}/f_\mathrm{u} $, on the transverse momentum ($ p_{\mathrm{T}} $) and rapidity of the B mesons is studied using the decay channels $ \mathrm{B}_{\mathrm{s}}^{0} \! \to \! \mathrm{J}/\psi \, \phi $ and $ {\mathrm{B}^{+}} \! \to \! \mathrm{J}/\psi \, \mathrm{K}^{+} $. The analysis uses a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 61.6 fb$ ^{-1} $. The $ f_\mathrm{s}/f_\mathrm{u} $ ratio is observed to depend on the B $ p_{\mathrm{T}} $ and to be consistent with becoming asymptotically constant at large $ p_{\mathrm{T}} $. No rapidity dependence is observed. The ratio of the $ {\mathrm{B}^0} $ to $ {\mathrm{B}^{+}} $ hadron production fractions, $ f_\mathrm{d}/f_\mathrm{u} $, measured using the $ {\mathrm{B}^0} \! \to \! \mathrm{J}/\psi \, \mathrm{K^{\ast}(892)}^{0} $ decay channel, is found to be consistent with unity and independent of $ p_{\mathrm{T}} $ and rapidity.
Links: e-print arXiv:2212.02309 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The $ \mathrm{J}/\psi \, \phi $, $ \mathrm{J}/\psi \, \mathrm{K^+} $, and $ \mathrm{J}/\psi \, \mathrm{K^{\ast}(892)}^{0} $ invariant mass distributions for B meson candidates with 20 $ < p_{\mathrm{T}} < $ 23 GeV, and associated fits as described in the text.
png pdf	Figure 2: Efficiency-corrected yield ratio $ {\mathcal R_\mathrm{s}} $, as a function of $ p_{\mathrm{T}} $ (left) and $ \|y\| $ (right). The vertical bars (boxes) represent the statistical (bin-to-bin systematic) uncertainties, while the horizontal bars give the bin widths. The global uncertainty (of 2.3%) is not graphically represented. The blue line represents the average for $ p_{\mathrm{T}} > $ 18 GeV. For comparison, the LHCb measurement [14] is also shown.
png pdf	Figure 3: The ratio of the $ {\mathrm{B}^0} $ to $ {\mathrm{B}^{+}} $ hadron production fractions $ f_\mathrm{d}/f_\mathrm{u} $, as a function of $ p_{\mathrm{T}} $ (left) and $ \|y\| $ (right). The vertical bars (boxes) represent the statistical (bin-to-bin systematic) uncertainties, while the horizontal bars give the bin widths. The global uncertainty (of 4.9%) is not graphically represented. The blue line represents the average of all the points.

Tables
png pdf	Table A1: The measured $ {\mathcal R_\mathrm{s}} $ values as a function of $ p_{\mathrm{T}} $, with the statistical ($ \sigma_{\text{stat}} $) and bin-to-bin systematic ($ \sigma_{\text{sys}} $) uncertainties, in percent. All the results are also affected by an extra global systematic uncertainty of 2.3%, reflecting the track reconstruction efficiency.
png pdf	Table A2: The measured $ {\mathcal R_\mathrm{s}} $ values as a function of $ \|y\| $, with the statistical ($ \sigma_{\text{stat}} $) and bin-to-bin systematic ($ \sigma_{\text{sys}} $) uncertainties, in percent. All the results are also affected by an extra global systematic uncertainty of 2.3%, reflecting the track reconstruction efficiency.
png pdf	Table A3: The measured $ f_\mathrm{d}/f_\mathrm{u} $ values as a function of $ p_{\mathrm{T}} $, with the statistical ($ \sigma_{\text{stat}} $) and bin-to-bin systematic ($ \sigma_{\text{sys}} $) uncertainties, in percent. All the results are also affected by an extra global systematic uncertainty of 4.9%, reflecting the track reconstruction efficiency and the branching fractions needed to convert $ {\mathcal R_\mathrm{d}} $ into $ f_\mathrm{d}/f_\mathrm{u} $.
png pdf	Table A4: The measured $ f_\mathrm{d}/f_\mathrm{u} $ values as a function of $ \|y\| $, with the statistical ($ \sigma_{\text{stat}} $) and bin-to-bin systematic ($ \sigma_{\text{sys}} $) uncertainties, in percent. All the results are also affected by an extra global systematic uncertainty of 4.9%, reflecting the track reconstruction efficiency and the branching fractions needed to convert $ {\mathcal R_\mathrm{d}} $ into $ f_\mathrm{d}/f_\mathrm{u} $.

Summary

In summary, the ratio of the $ \mathrm{B}_{\mathrm{s}}^{0} $ and $ {\mathrm{B}^{+}} $ hadron production fractions, $ f_\mathrm{s}/f_\mathrm{u} $, directly proportional to the ratio of the efficiency-corrected meson yields, $ {\mathcal R_\mathrm{s}} $, is studied as a function of the B meson transverse momentum $ p_{\mathrm{T}} $ and rapidity, using the $ \mathrm{B}_{\mathrm{s}}^{0} \! \to \! \mathrm{J}/\psi \, \phi $ and $ {\mathrm{B}^{+}} \! \to \! \mathrm{J}/\psi \, \mathrm{K}^{+} $ decay channels. The analysis uses an event sample of pp collisions at a center-of-mass energy of 13 TeV, collected by CMS in 2018 and corresponding to an integrated luminosity of 61.6 fb$ ^{-1} $. While no $ {\mathcal R_\mathrm{s}} $ dependence on the B meson rapidity is seen, a strong variation is observed in the 12 $ < p_{\mathrm{T}} < $ 18 GeV range, followed by a flat trend for higher $ p_{\mathrm{T}} $ values. The $ f_\mathrm{d}/f_\mathrm{u} $ ratio, measured using the $ {\mathrm{B}^0} \! \to \! \mathrm{J}/\psi \, \mathrm{K^{\ast}(892)}^{0} $ decay channel, is found to be compatible with unity and independent of rapidity and $ p_{\mathrm{T}} $, as predicted by strong isospin symmetry. The b hadron production fractions presented in this Letter provide a crucial input to measurements by ATLAS and CMS of the $ \mathrm{B}_{\mathrm{s}}^{0} \to \mu^{+}\mu^{-} $ branching fraction.

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