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Title: Towards the discovery of new physics with lepton-universality ratios of b s decays

Abstract

Tests of lepton-universality as rate ratios in $$b{\rightarrow}s{\ell}{\ell}$$ transitions can be predicted very accurately in the Standard Model. The deficits with respect to expectations reported by the LHCb experiment in muon-to-electron ratios of the $$B{\rightarrow}{K}^{(*)}{\ell}{\ell}$$ decay rates thus point to genuine manifestations of lepton nonuniversal new physics. In this paper, we analyze these measurements in the context of effective field theory. First, we discuss the interplay of the different operators in $${R}_{K}$$ and $${R}_{{K}^{*}}$$ and provide predictions for $${R}_{{K}^{*}}$$ in the Standard Model and in new-physics scenarios that can explain $${R}_{K}$$. We also provide approximate numerical formulas for these observables in bins of interest as functions of the relevant Wilson coefficients. Secondly, we perform frequentist fits to $${R}_{K}$$ and $${R}_{{K}^{*}}$$. The Standard Model disagrees with these measurements at $$3.7{\sigma}$$ significance. We find excellent fits in scenarios with combinations of $${\mathcal{O}}_{9(10)}^{{\ell}}=\overline{s}{{\gamma}}^{{\mu}}{b}_{L}{\ell}{{\gamma}}_{{\mu}}({{\gamma}}_{5}){\ell}$$ operators, with pulls relative to the Standard Model in the region of $$4{\sigma}$$. An important conclusion of our analysis is that a lepton-specific contribution to $${\mathcal{O}}_{10}$$ is important to understand the data. Under the hypothesis that new-physics couples selectively to the muons, we also present fits to other $$b{\rightarrow}s{\mu}{\mu}$$ data with a conservative error assessment and comment on more general scenarios. Finally, we discuss new lepton universality ratios that, if new physics is the origin of the observed discrepancy, should contribute to the statistically significant discovery of new physics in the near future.

Authors:
 [1];  [2];  [3];  [4];  [5];  [1]
  1. Beihang Univ., Beijing (China). School of Physics and Nuclear Energy Engineering. International Research Center for Nuclei and Particles in the Cosmos
  2. Univ. of California, San Diego, CA (United States). Dept. of Physics
  3. Univ. of Sussex, Brighton (United Kingdom). Dept. of Physics and Astronomy
  4. European Organization for Nuclear Research (CERN), Geneva (Switzerland). Theoretical Physics Dept.
  5. Peking Univ., Beijing (China). State Key Lab. of Nuclear Physics and Technology. School of Physics; Ruhr Univ., Bochum (Germany). Inst. of Theoretical Physics II
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States); Beihang Univ., Beijing (China); Peking Univ., Beijing (China); Univ. of Sussex, Brighton (United Kingdom)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); National Natural Science Foundation of China (NNSFC); Science and Technology Facilities Council (STFC) (United Kingdom)
OSTI Identifier:
1409227
Alternate Identifier(s):
OSTI ID: 1498882
Grant/Contract Number:  
SC0009919; 11375024; 11522539; ST/L000504/1
Resource Type:
Published Article
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 96; Journal Issue: 9; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; effective field theory; hypothetical particle physics models; rare decays

Citation Formats

Geng, Li-Sheng, Grinstein, Benjamín, Jäger, Sebastian, Martin Camalich, Jorge, Ren, Xiu-Lei, and Shi, Rui-Xiang. Towards the discovery of new physics with lepton-universality ratios of b→sℓℓ decays. United States: N. p., 2017. Web. doi:10.1103/physrevd.96.093006.
Geng, Li-Sheng, Grinstein, Benjamín, Jäger, Sebastian, Martin Camalich, Jorge, Ren, Xiu-Lei, & Shi, Rui-Xiang. Towards the discovery of new physics with lepton-universality ratios of b→sℓℓ decays. United States. doi:10.1103/physrevd.96.093006.
Geng, Li-Sheng, Grinstein, Benjamín, Jäger, Sebastian, Martin Camalich, Jorge, Ren, Xiu-Lei, and Shi, Rui-Xiang. Fri . "Towards the discovery of new physics with lepton-universality ratios of b→sℓℓ decays". United States. doi:10.1103/physrevd.96.093006.
@article{osti_1409227,
title = {Towards the discovery of new physics with lepton-universality ratios of b→sℓℓ decays},
author = {Geng, Li-Sheng and Grinstein, Benjamín and Jäger, Sebastian and Martin Camalich, Jorge and Ren, Xiu-Lei and Shi, Rui-Xiang},
abstractNote = {Tests of lepton-universality as rate ratios in $b{\rightarrow}s{\ell}{\ell}$ transitions can be predicted very accurately in the Standard Model. The deficits with respect to expectations reported by the LHCb experiment in muon-to-electron ratios of the $B{\rightarrow}{K}^{(*)}{\ell}{\ell}$ decay rates thus point to genuine manifestations of lepton nonuniversal new physics. In this paper, we analyze these measurements in the context of effective field theory. First, we discuss the interplay of the different operators in ${R}_{K}$ and ${R}_{{K}^{*}}$ and provide predictions for ${R}_{{K}^{*}}$ in the Standard Model and in new-physics scenarios that can explain ${R}_{K}$. We also provide approximate numerical formulas for these observables in bins of interest as functions of the relevant Wilson coefficients. Secondly, we perform frequentist fits to ${R}_{K}$ and ${R}_{{K}^{*}}$. The Standard Model disagrees with these measurements at $3.7{\sigma}$ significance. We find excellent fits in scenarios with combinations of ${\mathcal{O}}_{9(10)}^{{\ell}}=\overline{s}{{\gamma}}^{{\mu}}{b}_{L}{\ell}{{\gamma}}_{{\mu}}({{\gamma}}_{5}){\ell}$ operators, with pulls relative to the Standard Model in the region of $4{\sigma}$. An important conclusion of our analysis is that a lepton-specific contribution to ${\mathcal{O}}_{10}$ is important to understand the data. Under the hypothesis that new-physics couples selectively to the muons, we also present fits to other $b{\rightarrow}s{\mu}{\mu}$ data with a conservative error assessment and comment on more general scenarios. Finally, we discuss new lepton universality ratios that, if new physics is the origin of the observed discrepancy, should contribute to the statistically significant discovery of new physics in the near future.},
doi = {10.1103/physrevd.96.093006},
journal = {Physical Review D},
number = 9,
volume = 96,
place = {United States},
year = {2017},
month = {11}
}

Journal Article:
Free Publicly Available Full Text
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DOI: 10.1103/physrevd.96.093006

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Cited by: 75 works
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