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

Caria, G and Urquijo, P and Adachi, I and Giri, Anjan Kumar and et al, . (2021) Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method. Physical Review Letters. 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 semileptonic tagging method.

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IITH Creators:

IITH Creators	ORCiD
Giri, Anjan Kumar	UNSPECIFIED

Item Type:

Article

Uncontrolled Keywords:

Atomic physics,Physics, High energy physics, Belle detectors,Branching fractions,Measured values,Precise measurements,Semileptonic decay,Simultaneous measurement,Standard deviation,The standard model

Subjects:

Physics
Physics > Classical mechanics
Physics > Modern physics

Divisions:

Department of Physics

Depositing User:

. LibTrainee 2021

Date Deposited:

06 Apr 2021 11:36

Last Modified:

31 Aug 2021 06:57

URI:

http://raiithold.iith.ac.in/id/eprint/7751