Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method

(Belle Collaboration)

doi:10.1103/PhysRevLett.124.161803

Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method

(Belle Collaboration)

Department of Physics

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66 Citations (Scopus)

Abstract

The experimental results on the ratios of branching fractions R(D)=B(B→Dτ-ντ)/B(B→Dℓ-νℓ) and R(D∗)=B(B→D∗τ-ντ)/B(B→D∗ℓ-νℓ), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D∗), based on a data sample containing 772×106 BB events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e+e- collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D∗)=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D∗), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D∗) performed to date as well as the first result for R(D) based on a semileptonic tagging method.

Original language	English
Article number	161803
Journal	Physical review letters
Volume	124
Issue number	16
DOIs	https://doi.org/10.1103/PhysRevLett.124.161803
Publication status	Published - 2020 Apr 24

Bibliographical note

Funding Information:
We thank the KEKB group for excellent operation of the accelerator; the KEK cryogenics group for efficient solenoid operations; and the KEK computer group, the NII, and PNNL/EMSL for valuable computing and SINET5 network support. We acknowledge support from MEXT, JSPS and Nagoya’s Tau-Lepton Physics Research Center of Nagoya University (TLPRC); ARC (Australia); FWF (Austria); NSFC and CAS Center for Excellence in Particle Physics(CCEPP) (China); MSMT (Czechia); Carl Zeiss Foundation (CZF), DFG, Excellence Cluster Universe (EXC153), and VolkswagenStiftung (VS) (Germany); DST (India); INFN (Italy); MOE, MSIP, NRF, Radiation Science Research Institute (RSRI), Foreign Large-size Research Facility Application Supporting project (FLRFAS) project, GSDC of KISTI and KREONET/GLORIAD (Korea); MNiSW and NCN (Poland), Agreement No. 14.W03.31.0026 (Russia); ARRS (Slovenia); IKERBASQUE (Spain); SNSF (Switzerland); MOE and MOST (Taiwan); and DOE and NSF (U.S.A.). We acknowledge the support provided by the Albert Shimmins Fund for the writing of this Letter.

Publisher Copyright:
© 2020 authors.

All Science Journal Classification (ASJC) codes

Physics and Astronomy(all)

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10.1103/PhysRevLett.124.161803

Cite this

@article{2c4a949e0e474de3a9a286b4bae027a1,

title = "Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method",

abstract = "The experimental results on the ratios of branching fractions R(D)=B(B→Dτ-ντ)/B(B→Dℓ-νℓ) and R(D∗)=B(B→D∗τ-ντ)/B(B→D∗ℓ-νℓ), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D∗), based on a data sample containing 772×106 BB events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e+e- collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D∗)=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D∗), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D∗) performed to date as well as the first result for R(D) based on a semileptonic tagging method.",

author = "{(Belle Collaboration)} and G. Caria and P. Urquijo and I. Adachi and H. Aihara and {Al Said}, S. and Asner, {D. M.} and H. Atmacan and T. Aushev and V. Babu and I. Badhrees and S. Bahinipati and Bakich, {A. M.} and P. Behera and C. Bele{\~n}o and J. Bennett and B. Bhuyan and T. Bilka and J. Biswal and A. Bozek and M. Bra{\v c}ko and Browder, {T. E.} and M. Campajola and D. {\v C}ervenkov and P. Chang and R. Cheaib and V. Chekelian and A. Chen and Cheon, {B. G.} and K. Chilikin and Cho, {H. E.} and K. Cho and Y. Choi and S. Choudhury and D. Cinabro and S. Cunliffe and N. Dash and {De Nardo}, G. and {Di Capua}, F. and {Di Carlo}, S. and Z. Dole{\v Z}al and Dong, {T. V.} and S. Eidelman and D. Epifanov and Fast, {J. E.} and T. Ferber and D. Ferlewicz and Fulsom, {B. G.} and R. Garg and V. Gaur and Kwon, {Y. J.}",

note = "Funding Information: We thank the KEKB group for excellent operation of the accelerator; the KEK cryogenics group for efficient solenoid operations; and the KEK computer group, the NII, and PNNL/EMSL for valuable computing and SINET5 network support. We acknowledge support from MEXT, JSPS and Nagoya{\textquoteright}s Tau-Lepton Physics Research Center of Nagoya University (TLPRC); ARC (Australia); FWF (Austria); NSFC and CAS Center for Excellence in Particle Physics(CCEPP) (China); MSMT (Czechia); Carl Zeiss Foundation (CZF), DFG, Excellence Cluster Universe (EXC153), and VolkswagenStiftung (VS) (Germany); DST (India); INFN (Italy); MOE, MSIP, NRF, Radiation Science Research Institute (RSRI), Foreign Large-size Research Facility Application Supporting project (FLRFAS) project, GSDC of KISTI and KREONET/GLORIAD (Korea); MNiSW and NCN (Poland), Agreement No. 14.W03.31.0026 (Russia); ARRS (Slovenia); IKERBASQUE (Spain); SNSF (Switzerland); MOE and MOST (Taiwan); and DOE and NSF (U.S.A.). We acknowledge the support provided by the Albert Shimmins Fund for the writing of this Letter. Publisher Copyright: {\textcopyright} 2020 authors.",

year = "2020",

month = apr,

day = "24",

doi = "10.1103/PhysRevLett.124.161803",

language = "English",

volume = "124",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "16",

}

TY - JOUR

T1 - Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method

AU - (Belle Collaboration)

AU - Caria, G.

AU - Urquijo, P.

AU - Adachi, I.

AU - Aihara, H.

AU - Al Said, S.

AU - Asner, D. M.

AU - Atmacan, H.

AU - Aushev, T.

AU - Babu, V.

AU - Badhrees, I.

AU - Bahinipati, S.

AU - Bakich, A. M.

AU - Behera, P.

AU - Beleño, C.

AU - Bennett, J.

AU - Bhuyan, B.

AU - Bilka, T.

AU - Biswal, J.

AU - Bozek, A.

AU - Bračko, M.

AU - Browder, T. E.

AU - Campajola, M.

AU - Červenkov, D.

AU - Chang, P.

AU - Cheaib, R.

AU - Chekelian, V.

AU - Chen, A.

AU - Cheon, B. G.

AU - Chilikin, K.

AU - Cho, H. E.

AU - Cho, K.

AU - Choi, Y.

AU - Choudhury, S.

AU - Cinabro, D.

AU - Cunliffe, S.

AU - Dash, N.

AU - De Nardo, G.

AU - Di Capua, F.

AU - Di Carlo, S.

AU - DoleŽal, Z.

AU - Dong, T. V.

AU - Eidelman, S.

AU - Epifanov, D.

AU - Fast, J. E.

AU - Ferber, T.

AU - Ferlewicz, D.

AU - Fulsom, B. G.

AU - Garg, R.

AU - Gaur, V.

AU - Kwon, Y. J.

N1 - Funding Information: We thank the KEKB group for excellent operation of the accelerator; the KEK cryogenics group for efficient solenoid operations; and the KEK computer group, the NII, and PNNL/EMSL for valuable computing and SINET5 network support. We acknowledge support from MEXT, JSPS and Nagoya’s Tau-Lepton Physics Research Center of Nagoya University (TLPRC); ARC (Australia); FWF (Austria); NSFC and CAS Center for Excellence in Particle Physics(CCEPP) (China); MSMT (Czechia); Carl Zeiss Foundation (CZF), DFG, Excellence Cluster Universe (EXC153), and VolkswagenStiftung (VS) (Germany); DST (India); INFN (Italy); MOE, MSIP, NRF, Radiation Science Research Institute (RSRI), Foreign Large-size Research Facility Application Supporting project (FLRFAS) project, GSDC of KISTI and KREONET/GLORIAD (Korea); MNiSW and NCN (Poland), Agreement No. 14.W03.31.0026 (Russia); ARRS (Slovenia); IKERBASQUE (Spain); SNSF (Switzerland); MOE and MOST (Taiwan); and DOE and NSF (U.S.A.). We acknowledge the support provided by the Albert Shimmins Fund for the writing of this Letter. Publisher Copyright: © 2020 authors.

PY - 2020/4/24

Y1 - 2020/4/24

N2 - The experimental results on the ratios of branching fractions R(D)=B(B→Dτ-ντ)/B(B→Dℓ-νℓ) and R(D∗)=B(B→D∗τ-ντ)/B(B→D∗ℓ-νℓ), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D∗), based on a data sample containing 772×106 BB events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e+e- collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D∗)=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D∗), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D∗) performed to date as well as the first result for R(D) based on a semileptonic tagging method.

AB - The experimental results on the ratios of branching fractions R(D)=B(B→Dτ-ντ)/B(B→Dℓ-νℓ) and R(D∗)=B(B→D∗τ-ντ)/B(B→D∗ℓ-νℓ), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D∗), based on a data sample containing 772×106 BB events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e+e- collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D∗)=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D∗), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D∗) performed to date as well as the first result for R(D) based on a semileptonic tagging method.

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U2 - 10.1103/PhysRevLett.124.161803

DO - 10.1103/PhysRevLett.124.161803

M3 - Article

C2 - 32383937

AN - SCOPUS:85084721463

SN - 0031-9007

VL - 124

JO - Physical Review Letters

JF - Physical Review Letters

IS - 16

M1 - 161803

ER -

Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method

Abstract

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