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

Caria, G. and Urquijo, P. and Adachi, I. and Giri, Anjan Kumar et. al. (2020) Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method. Physical Review Letters, 124 (16). p. 161803. ISSN 0031-9007

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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 semile ===ptonic tagging method.

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IITH Creators:
IITH CreatorsORCiD
Giri, Anjan KumarUNSPECIFIED
Item Type: Article
Uncontrolled Keywords: Belle detectors; Branching fractions; Measured values; Precise measurements; Semileptonic decay; Simultaneous measurement; Standard deviation; The standard model
Subjects: Physics
Divisions: Department of Physics
Depositing User: . LibTrainee 2021
Date Deposited: 14 Jul 2021 08:13
Last Modified: 31 Aug 2021 06:59
URI: http://raiith.iith.ac.in/id/eprint/8319
Publisher URL:
OA policy: https://v2.sherpa.ac.uk/id/publication/13640
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