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| CMS-BPH-24-011 ; CERN-EP-2025-162 | ||
| First exclusive reconstruction of the $ \mathrm{B}^{*+} $, $ \mathrm{B}^{*0} $, and $ \mathrm{B}_{s}^{*0} $ mesons and precise measurement of their masses | ||
| CMS Collaboration | ||
| 6 August 2025 | ||
| Submitted to Phys. Rev. Lett. | ||
| Abstract: Using proton-proton collision data collected by the CMS experiment at $ \sqrt{s}= $ 13 TeV in 2016-2018, corresponding to an integrated luminosity of 140 fb$^{-1}$, the first full reconstruction of the three vector $ {\mathrm{B}} $ meson states, $ \mathrm{B}^{*+} $, $ \mathrm{B}^{*0} $, and $ \mathrm{B}_{s}^{*0} $, is performed. The mass differences between the excited mesons and their corresponding ground states are measured to be $ m(\mathrm{B}^{*+})-m({\mathrm{B}^{+}}) = $ 45.277 $ \pm $ 0.039 $ \pm $ 0.027 MeV, $ m(\mathrm{B}^{*0})-m({\mathrm{B}^0}) = $ 45.471 $ \pm $ 0.056 $ \pm $ 0.028 MeV, and $ m(\mathrm{B}_{s}^{*0})-m(\mathrm{B}_{s}^{0}) = $ 49.407 $ \pm $ 0.132 $ \pm $ 0.041 MeV, where the first uncertainties are statistical and the second are systematic. These results improve on the precision of previous measurements by an order of magnitude. | ||
| Links: e-print arXiv:2508.05820 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper left), $ {\mathrm{B}^0}\gamma $ (upper right), and $ \mathrm{B}_{s}^{0}\gamma $ (lower) invariant mass in the lowest $ |\eta(\gamma)| $ range, which has the best invariant mass resolution. The simultaneous fit projections are shown with thick red lines, and the other components are described in the legends. The error bars represent statistical uncertainties in data. |
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Figure 1-a:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper left), $ {\mathrm{B}^0}\gamma $ (upper right), and $ \mathrm{B}_{s}^{0}\gamma $ (lower) invariant mass in the lowest $ |\eta(\gamma)| $ range, which has the best invariant mass resolution. The simultaneous fit projections are shown with thick red lines, and the other components are described in the legends. The error bars represent statistical uncertainties in data. |
png pdf |
Figure 1-b:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper left), $ {\mathrm{B}^0}\gamma $ (upper right), and $ \mathrm{B}_{s}^{0}\gamma $ (lower) invariant mass in the lowest $ |\eta(\gamma)| $ range, which has the best invariant mass resolution. The simultaneous fit projections are shown with thick red lines, and the other components are described in the legends. The error bars represent statistical uncertainties in data. |
png pdf |
Figure 1-c:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper left), $ {\mathrm{B}^0}\gamma $ (upper right), and $ \mathrm{B}_{s}^{0}\gamma $ (lower) invariant mass in the lowest $ |\eta(\gamma)| $ range, which has the best invariant mass resolution. The simultaneous fit projections are shown with thick red lines, and the other components are described in the legends. The error bars represent statistical uncertainties in data. |
png pdf |
Figure A1:
The measured distributions of the diphoton invariant mass near the $ \pi^{0} $ mass with the fit results overlaid, before (left) and after (right) the PES correction, in the kinematic range 0.8 $ < p_{\mathrm{T}}(\gamma) < 0.9\,\text{Ge\hspace{-.08em}V} $, 0.8 $ < |\eta(\gamma)| < $ 0.9. The green vertical line shows the world-average value of the $ \pi^{0} $ mass of 134.98 MeV [28]. |
png pdf |
Figure A1-a:
The measured distributions of the diphoton invariant mass near the $ \pi^{0} $ mass with the fit results overlaid, before (left) and after (right) the PES correction, in the kinematic range 0.8 $ < p_{\mathrm{T}}(\gamma) < 0.9\,\text{Ge\hspace{-.08em}V} $, 0.8 $ < |\eta(\gamma)| < $ 0.9. The green vertical line shows the world-average value of the $ \pi^{0} $ mass of 134.98 MeV [28]. |
png pdf |
Figure A1-b:
The measured distributions of the diphoton invariant mass near the $ \pi^{0} $ mass with the fit results overlaid, before (left) and after (right) the PES correction, in the kinematic range 0.8 $ < p_{\mathrm{T}}(\gamma) < 0.9\,\text{Ge\hspace{-.08em}V} $, 0.8 $ < |\eta(\gamma)| < $ 0.9. The green vertical line shows the world-average value of the $ \pi^{0} $ mass of 134.98 MeV [28]. |
png pdf |
Figure A2:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper), $ {\mathrm{B}^0}\gamma $ (lower left), and $ \mathrm{B}_{s}^{0}\gamma $ (lower right) invariant mass corresponding to the most forward one or two $ |\eta(\gamma)| $ regions, together with the simultaneous fit projections (thick red lines). The error bars represent statistical uncertainties in data. |
png pdf |
Figure A2-a:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper), $ {\mathrm{B}^0}\gamma $ (lower left), and $ \mathrm{B}_{s}^{0}\gamma $ (lower right) invariant mass corresponding to the most forward one or two $ |\eta(\gamma)| $ regions, together with the simultaneous fit projections (thick red lines). The error bars represent statistical uncertainties in data. |
png pdf |
Figure A2-b:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper), $ {\mathrm{B}^0}\gamma $ (lower left), and $ \mathrm{B}_{s}^{0}\gamma $ (lower right) invariant mass corresponding to the most forward one or two $ |\eta(\gamma)| $ regions, together with the simultaneous fit projections (thick red lines). The error bars represent statistical uncertainties in data. |
png pdf |
Figure A2-c:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper), $ {\mathrm{B}^0}\gamma $ (lower left), and $ \mathrm{B}_{s}^{0}\gamma $ (lower right) invariant mass corresponding to the most forward one or two $ |\eta(\gamma)| $ regions, together with the simultaneous fit projections (thick red lines). The error bars represent statistical uncertainties in data. |
png pdf |
Figure A2-d:
The measured distributions (filled circles) of the $ {\mathrm{B}^{+}}\gamma $ (upper), $ {\mathrm{B}^0}\gamma $ (lower left), and $ \mathrm{B}_{s}^{0}\gamma $ (lower right) invariant mass corresponding to the most forward one or two $ |\eta(\gamma)| $ regions, together with the simultaneous fit projections (thick red lines). The error bars represent statistical uncertainties in data. |
| Tables | |
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Table 1:
Systematic uncertainties in the measured mass differences, in keV. |
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Table 2:
Results of the measurement. The first uncertainties are statistical, the second are systematic, and the third, where present, are related to the masses or mass differences of the ground states taken from Ref. [28]. |
png pdf |
Table A1:
Values, statistical, and systematic uncertainties, in keV, of the measured differences of the three mass differences. |
png pdf |
Table A2:
Values, statistical, and systematic uncertainties of the measured ratios of the three mass differences. |
| Summary |
| In summary, three vector $ {\mathrm{B}} $ meson states, $ \mathrm{B}^{*+} $, $ \mathrm{B}^{*0} $, and $ \mathrm{B}_{s}^{*0} $, have been fully reconstructed in exclusive final states for the first time by detecting low-energy photons through their conversion to $ \mathrm{e}^+\mathrm{e}^- $ pairs in the beam pipe and detector material. The data sample of $ \sqrt{s}= $ 13 TeV proton-proton collisions was collected by the CMS experiment and corresponds to an integrated luminosity of 140 fb$ ^{-1} $. The measurements benefit from a new photon energy scale calibration method that uses $ \pi^{0}\to\gamma\gamma $ decays in which both photons convert to $ \mathrm{e}^+\mathrm{e}^- $ pairs. The masses of the three vector states are measured with respect to the corresponding ground states to be $ m(\mathrm{B}^{*+})-m({\mathrm{B}^{+}}) = $ 45.277 $ \pm $ 0.039 $ \pm $ 0.027 MeV, $ m(\mathrm{B}^{*0})-m({\mathrm{B}^0}) = $ 45.471 $ \pm $ 0.056 $ \pm $ 0.028 MeV, and $ m(\mathrm{B}_{s}^{*0})-m(\mathrm{B}_{s}^{0}) = $ 49.407 $ \pm $ 0.132 $ \pm $ 0.041 MeV, where the first uncertainties are statistical and the second are systematic. A number of difference and ratio measurements between the reported masses and mass differences are also provided, where, due to cancellations in the computations of these quantities, both experimental and theoretical uncertainties are lower. These results are either the first measurement or an order of magnitude more precise than previous measurements. The new measurements are more precise than the available theoretical predictions and provide an important input to our understanding of heavy-quark systems. |
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Compact Muon Solenoid LHC, CERN |
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