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| CMS-PAS-BPH-22-012 | ||
| Test of lepton flavor universality violation in semileptonic $ \mathrm{B}_{\mathrm{c}}^+ $ meson decays at CMS | ||
| CMS Collaboration | ||
| 31 August 2023 | ||
| Abstract: A measurement of the ratio of branching fractions $ \mathrm{R}(\mathrm{J}/\psi) = \mathcal{B}(\mathrm{B}_{\mathrm{c}}^+\rightarrow\mathrm{J}/\psi\tau^+\nu_{\tau}) / \mathcal{B}(\mathrm{B}_{\mathrm{c}}^+\rightarrow\mathrm{J}/\psi\mu^+\nu_{\mu}) $ in the $ \mathrm{J}/\psi\rightarrow\mu^+\mu^- $, $ \tau^+\rightarrow\mu^+\nu_{\mu}\nu_{\bar{\tau}} $ decay channel is presented. This measurement uses a sample of proton-proton collision data at a center of mass energy of 13 TeV collected by the CMS experiment in 2018 and corresponding to 59.7 fb$ ^{-1} $ of integrated luminosity. The measured ratio $ \mathrm{R}(\mathrm{J}/\psi) = $ 0.17 $ ^{+ 0.18}_{- 0.17} $ (stat) $^{+ 0.21}_{- 0.22} $ (syst) $^{+ 0.19}_{- 0.18} $ (theo) $ = $ 0.17 $ \pm $ 0.33 agrees within 0.3 standard deviations with the value predicted by the standard model of particle physics. | ||
| Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Distributions of the $ L_{xy}/\sigma_{L_{xy}} $ (left) observable for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) signal channel, the fakes background (red) and the $ H_\mathrm{b} $ background (green); distributions of the $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} $ (center) and $ q^2 $ (right) observables for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) and $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \tau^+\nu_{ \tau} $ (purple) signal channels and the fakes background (red). In all plots, events are selected in the region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $. |
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Figure 1-a:
Distributions of the $ L_{xy}/\sigma_{L_{xy}} $ (left) observable for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) signal channel, the fakes background (red) and the $ H_\mathrm{b} $ background (green); distributions of the $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} $ (center) and $ q^2 $ (right) observables for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) and $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \tau^+\nu_{ \tau} $ (purple) signal channels and the fakes background (red). In all plots, events are selected in the region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $. |
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Figure 1-b:
Distributions of the $ L_{xy}/\sigma_{L_{xy}} $ (left) observable for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) signal channel, the fakes background (red) and the $ H_\mathrm{b} $ background (green); distributions of the $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} $ (center) and $ q^2 $ (right) observables for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) and $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \tau^+\nu_{ \tau} $ (purple) signal channels and the fakes background (red). In all plots, events are selected in the region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $. |
png pdf |
Figure 1-c:
Distributions of the $ L_{xy}/\sigma_{L_{xy}} $ (left) observable for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) signal channel, the fakes background (red) and the $ H_\mathrm{b} $ background (green); distributions of the $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} $ (center) and $ q^2 $ (right) observables for the $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \mu^+\nu_{ \mu} $ (blue) and $ \mathrm{B}_{c}^{+} \to \mathrm{J}/\psi\, \tau^+\nu_{ \tau} $ (purple) signal channels and the fakes background (red). In all plots, events are selected in the region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $. |
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Figure 2:
Likelihood scan of the $ \mathrm{R}(\mathrm{J}/\psi) $ measurement. The blue dashed line includes only statistical uncertainty, whereas the red dashed line includes also theoretical systematic uncertainties and the solid black line includes all uncertainties. |
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Figure 3:
Distributions of the $ q^2 $ observable in the signal-enriched data region, defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 > $ 5.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 2 (left); of the $ L_{xy}/\sigma_{L_{xy}} $ observable in the data region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 < $ 4.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 0 (center) and in the data region defined by $ m(3\mu) > m_{\mathrm{B}_{c}^{+}} $(right). In each figure, data are compared to the expectation, with the normalization, shape parameters for the different contributions as well as $ \mathrm{R}(\mathrm{J}/\psi) $ shown at their best-fit values. The ratio between the data and the expected stack of signal and background contributions is shown in the lower panel. The post-fit total uncertainty of the expectation is represented by the hashed band. |
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Figure 3-a:
Distributions of the $ q^2 $ observable in the signal-enriched data region, defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 > $ 5.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 2 (left); of the $ L_{xy}/\sigma_{L_{xy}} $ observable in the data region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 < $ 4.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 0 (center) and in the data region defined by $ m(3\mu) > m_{\mathrm{B}_{c}^{+}} $(right). In each figure, data are compared to the expectation, with the normalization, shape parameters for the different contributions as well as $ \mathrm{R}(\mathrm{J}/\psi) $ shown at their best-fit values. The ratio between the data and the expected stack of signal and background contributions is shown in the lower panel. The post-fit total uncertainty of the expectation is represented by the hashed band. |
png pdf |
Figure 3-b:
Distributions of the $ q^2 $ observable in the signal-enriched data region, defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 > $ 5.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 2 (left); of the $ L_{xy}/\sigma_{L_{xy}} $ observable in the data region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 < $ 4.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 0 (center) and in the data region defined by $ m(3\mu) > m_{\mathrm{B}_{c}^{+}} $(right). In each figure, data are compared to the expectation, with the normalization, shape parameters for the different contributions as well as $ \mathrm{R}(\mathrm{J}/\psi) $ shown at their best-fit values. The ratio between the data and the expected stack of signal and background contributions is shown in the lower panel. The post-fit total uncertainty of the expectation is represented by the hashed band. |
png pdf |
Figure 3-c:
Distributions of the $ q^2 $ observable in the signal-enriched data region, defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 > $ 5.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 2 (left); of the $ L_{xy}/\sigma_{L_{xy}} $ observable in the data region defined by $ m(3\mu) < m_{\mathrm{B}_{c}^{+}} $ in the bin of $ q^2 < $ 4.5 GeV$^2$ and $ \mathrm{IP3D}/\sigma_{\mathrm{IP3D}} > $ 0 (center) and in the data region defined by $ m(3\mu) > m_{\mathrm{B}_{c}^{+}} $(right). In each figure, data are compared to the expectation, with the normalization, shape parameters for the different contributions as well as $ \mathrm{R}(\mathrm{J}/\psi) $ shown at their best-fit values. The ratio between the data and the expected stack of signal and background contributions is shown in the lower panel. The post-fit total uncertainty of the expectation is represented by the hashed band. |
| Tables | |
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Table 1:
Leading systematic uncertainties for the measurement of $ \mathrm{R}(\mathrm{J}/\psi) $. The second column reports the uncertainty type: shape or normalization. For shape uncertainties we also include the number of shapes considered (except for bin-by-bin), while for normalization uncertainties the relative contribution (%) is reported in the third column. The last column shows the resulting uncertainty on the $ \mathrm{R}(\mathrm{J}/\psi) $ measurement ($ \Delta\mathrm{R}(\mathrm{J}/\psi) $). |
| Summary |
|
In summary, using data collected by the CMS experiment in 2018 at a center of mass energy of 13 TeV and corresponding to 59.7 fb$ ^{-1} $ of integrated luminosity, the measurement of the ratio of branching fractions gives: |
| References | ||||
| 1 | UA1 Collaboration | Studies of Intermediate Vector Boson Production and Decay in UA1 at the CERN Proton - Antiproton Collider | Z. Phys. C 44 (1989) 15 | |
| 2 | ALEPH, DELPHI, L3, OPAL, SLD, LEP Electroweak Working Group, SLD Electroweak Group, SLD Heavy Flavour Group Collaboration | Precision electroweak measurements on the $ Z $ resonance | Phys. Rept. 427 (2006) 257 | hep-ex/0509008 |
| 3 | ATLAS Collaboration | Precision measurement and interpretation of inclusive $ W^+ $, $ W^- $ and $ Z/\gamma ^* $ production cross sections with the ATLAS detector | EPJC 77 (2017) 367 | 1612.03016 |
| 4 | M. Tanaka | Charged Higgs effects on exclusive semitauonic $ B $ decays | Z. Phys. C 67 (1995) 321 | hep-ph/9411405 |
| 5 | A. Crivellin, C. Greub, and A. Kokulu | Explaining $ B\to D\tau\nu $, $ B\to D^*\tau\nu $ and $ B\to \tau\nu $ in a 2HDM of type III | PRD 86 (2012) 054014 | 1206.2634 |
| 6 | M. Freytsis, Z. Ligeti, and J. T. Ruderman | Flavor models for $ \bar{B} \to D^{(*)} \tau \bar{\nu} $ | PRD 92 (2015) 054018 | 1506.08896 |
| 7 | A. Crivellin, G. D'Ambrosio, and J. Heeck | Addressing the LHC flavor anomalies with horizontal gauge symmetries | PRD 91 (2015) 075006 | 1503.03477 |
| 8 | ATLAS Collaboration | Search for new phenomena in $ pp $ collisions in final states with tau leptons, b-jets, and missing transverse momentum with the ATLAS detector | PRD 104 (2021) 112005 | 2108.07665 |
| 9 | CMS Collaboration | Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at $ \sqrt{s} $ = 13 TeV | JHEP 11 (2021) 153 | CMS-EXO-20-004 2107.13021 |
| 10 | CMS Collaboration | Search for heavy resonances and quantum black holes in e\ensuremath\mu, e\ensuremath\tau, and \ensuremath\mu\ensuremath\tau final states in proton-proton collisions at $ \sqrt{s} $ = 13 TeV | JHEP 05 (2023) 227 | CMS-EXO-19-014 2205.06709 |
| 11 | CMS Collaboration | Search for a high-mass dimuon resonance produced in association with b quark jets at $ \sqrt{s} $=13 TeV | CMS-EXO-22-016 2307.08708 |
|
| 12 | BaBar Collaboration | Measurement of an Excess of $ \bar{B} \to D^{(*)}\tau^- \bar{\nu}_\tau $ Decays and Implications for Charged Higgs Bosons | PRD 88 (2013) 072012 | 1303.0571 |
| 13 | Belle Collaboration | Measurement of the branching ratio of $ \bar{B} \to D^{(\ast)} \tau^- \bar{\nu}_\tau $ relative to $ \bar{B} \to D^{(\ast)} \ell^- \bar{\nu}_\ell $ decays with hadronic tagging at Belle | PRD 92 (2015) 072014 | 1507.03233 |
| 14 | Belle Collaboration | Measurement of the branching ratio of $ \bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau} $ relative to $ \bar{B}^0 \rightarrow D^{*+} \ell^- \bar{\nu}_{\ell} $ decays with a semileptonic tagging method | PRD 94 (2016) 072007 | 1607.07923 |
| 15 | Belle Collaboration | Recent Belle II results on semileptonic B decays and tests of lepton-flavor universality | Talk given at 31st International Symposium on Lepton Photon Interactions at High Energies, July 2023 link |
|
| 16 | LHCb Collaboration | Measurement of the ratio of branching fractions $ \mathcal{B}(\bar{B}^0 \to D^{*+}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}^0 \to D^{*+}\mu^{-}\bar{\nu}_{\mu}) $ | PRL 115 (2015) 111803 | 1506.08614 |
| 17 | LHCb Collaboration | Measurement of the ratio of the $ B^0 \to D^{*-} \tau^+ \nu_{\tau} $ and $ B^0 \to D^{*-} \mu^+ \nu_{\mu} $ branching fractions using three-prong $ \tau $-lepton decays | PRL 120 (2018) 171802 | 1708.08856 |
| 18 | LHCb Collaboration | Measurement of the ratios of branching fractions $ \mathcal{R}(D^{*}) $ and $ \mathcal{R}(D^{0}) $ | 2302.02886 | |
| 19 | Y. Amhis et al. | Averages of $ b $-hadron, $ c $-hadron, and $ \tau $-lepton properties as of 2021 | PRD 107 (2023) 052008 | 2206.07501 |
| 20 | LATTICE-HPQCD Collaboration | $ R(J/\psi) $ and $ B_c^- \rightarrow J/\psi \ell^-\bar{\nu}_\ell $ Lepton Flavor Universality Violating Observables from Lattice QCD | PRL 125 (2020) 222003 | 2007.06956 |
| 21 | A. Y. Anisimov, I. M. Narodetsky, C. Semay, and B. Silvestre-Brac | The $ B_c $ meson lifetime in the light front constituent quark model | PLB 452 (1999) 129 | hep-ph/9812514 |
| 22 | V. V. Kiselev | Exclusive decays and lifetime of $ B_c $ meson in QCD sum rules | hep-ph/0211021 | |
| 23 | M. A. Ivanov, J. G. Korner, and P. Santorelli | Exclusive semileptonic and nonleptonic decays of the $ B_c $ meson | PRD 73 (2006) 054024 | hep-ph/0602050 |
| 24 | E. Hernandez, J. Nieves, and J. M. Verde-Velasco | Study of exclusive semileptonic and non-leptonic decays of $ B_c $ - in a nonrelativistic quark model | PRD 74 (2006) 074008 | hep-ph/0607150 |
| 25 | LHCb Collaboration | Measurement of the ratio of branching fractions $ \mathcal{B}(B_c^+\,\to\,J/\psi\tau^+\nu_\tau) $/$ \mathcal{B}(B_c^+\,\to\,J/\psi\mu^+\nu_\mu) $ | PRL 120 (2018) 121801 | 1711.05623 |
| 26 | CMS Collaboration | The CMS Experiment at the CERN LHC | JINST 3 (2008) S08004 | |
| 27 | CMS Collaboration | Performance of the CMS Level-1 trigger in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | JINST 15 (2020) P10017 | CMS-TRG-17-001 2006.10165 |
| 28 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 29 | CMS Collaboration | Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC | JINST 16 (2021) P05014 | CMS-EGM-17-001 2012.06888 |
| 30 | CMS Collaboration | Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $ \sqrt{s}= $ 13 TeV | JINST 13 (2018) P06015 | CMS-MUO-16-001 1804.04528 |
| 31 | CMS Collaboration | Description and performance of track and primary-vertex reconstruction with the CMS tracker | JINST 9 (2014) P10009 | CMS-TRK-11-001 1405.6569 |
| 32 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
| 33 | CMS Collaboration | Performance of reconstruction and identification of $ \tau $ leptons decaying to hadrons and $ \nu_\tau $ in pp collisions at $ \sqrt{s}= $ 13 TeV | JINST 13 (2018) P10005 | CMS-TAU-16-003 1809.02816 |
| 34 | CMS Collaboration | Identification of hadronic tau lepton decays using a deep neural network | JINST 17 (2022) P07023 | CMS-TAU-20-001 2201.08458 |
| 35 | CMS Collaboration | Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV | JINST 12 (2017) P02014 | CMS-JME-13-004 1607.03663 |
| 36 | CMS Collaboration | Performance of missing transverse momentum reconstruction in proton-proton collisions at $ \sqrt{s} = $ 13 TeV using the CMS detector | JINST 14 (2019) P07004 | CMS-JME-17-001 1903.06078 |
| 37 | LHCb Collaboration | Precision measurement of the $ B_{c}^{+} $ meson mass | JHEP 07 (2020) 123 | 2004.08163 |
| 38 | C.-H. Chang, X.-Y. Wang, and X.-G. Wu | BCVEGPY2.2: a newly upgraded version for hadronic production of the meson $ \rm B_c $ and its excited states | Comput. Phys. Commun. 197 (2015) 335 | 1507.05176 |
| 39 | D. J. Lange | The EvtGen particle decay simulation package | NIM A 462 (2001) 152 | |
| 40 | S. Frixione, E. Laenen, P. Motylinski, and B. R. Webber | Single-top production in MC@NLO | JHEP 03 (2006) 092 | hep-ph/0512250 |
| 41 | T. Sjostrand, S. Mrenna, and P. Z. Skands | A Brief Introduction to PYTHIA 8.1 | Comput. Phys. Commun. 178 (2008) 852 | 0710.3820 |
| 42 | Particle Data Group Collaboration | Review of particle physics | Prog. Theor. Exp. Phys. 2022 (2022) 083C01 | |
| 43 | LHCb Collaboration | Measurement of the $ B_c^- $ meson production fraction and asymmetry in 7 and 13 TeV $ pp $ collisions | PRD 100 (2019) 112006 | 1910.13404 |
| 44 | LHCb Collaboration | Observation of $ B^+_c \rightarrow J/\psi D_s^+ $ and $ B^+_c \rightarrow J/\psi D_s^{*+} $ decays | PRD 87 (2013) 112012 | 1304.4530 |
| 45 | ATLAS Collaboration | Study of the $ B_c^+ \rightarrow J/\psi D_s^+ $ and $ B_c^+ \rightarrow J/\psi D_s^{*+} $ decays with the ATLAS detector | EPJC 76 (2016) 1 | 1507.07099 |
| 46 | LHCb Collaboration | Observation of $ B_{c}^{+} \to J/\psi D^{(*)} K^{(*)} $ decays | PRD 95 (2017) 032005 | 1612.07421 |
| 47 | V. Kiselev, A. Likhoded, and A. Onishchenko | Semileptonic bc-meson decays in sum rules of qcd and nrqcd | Nuclear Physics B 569 (2000) 473 | |
| 48 | F. U. Bernlochner et al. | Das ist der HAMMER: Consistent new physics interpretations of semileptonic decays | EPJC 80 (2020) 883 | 2002.00020 |
| 49 | T. D. Cohen, H. Lamm, and R. F. Lebed | Precision model-independent bounds from a global analysis of $ b \rightarrow c\ell\nu $ form factors | PRD 10 (2019) 094503 | |
| 50 | CMS Collaboration | Measurement of the total and differential inclusive $ B^+ $ hadron cross sections in pp collisions at $ \sqrt{s} $ = 13 TeV | PLB 771 (2017) 435 | CMS-BPH-15-004 1609.00873 |
| 51 | Z. Was, P. Golonka, and G. Nanava | PHOTOS Monte Carlo and its theoretical accuracy | Nucl. Phys. B Proc. Suppl. 18 (2008) 1 | 0807.2762 |
| 52 | J. Allison et al. | Geant4 developments and applications | IEEE Trans. Nucl. Sci. 53 (2006) 270 | |
| 53 | CMS Collaboration | Measurement of the B$ ^0_\mathrm{S} \to \mu^+\mu^- $ decay properties and search for the B$ ^0 \to \mu^+\mu^- $ decay in proton-proton collisions at $ \sqrt{s} $ = 13 TeV | PLB 842 (2023) 137955 | CMS-BPH-21-006 2212.10311 |
| 54 | M. J. Oreglia | A study of the reactions $ \psi^\prime \to \gamma \gamma \psi $ | PhD thesis, Stanford University, SLAC Report SLAC-R-236, 1980 link |
|
| 55 | S. Algeri, J. Aalbers, K. Dundas Mor\r a , and J. Conrad | Searching for new phenomena with profile likelihood ratio tests | Nature Rev. Phys. 2 (2020) 245 | 1911.10237 |
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