Light resonances and the low-q2 bin of \( {R}_{K^{*}} \)

  • Wolfgang Altmannshofer
  • Michael J. Baker
  • Stefania Gori
  • Roni Harnik
  • Maxim Pospelov
  • Emmanuel Stamou
  • Andrea Thamm
Open Access
Regular Article - Theoretical Physics
  • 17 Downloads

Abstract

LHCb has reported hints of lepton-flavor universality violation in the rare decays BK(*)+, both in high- and low-q2 bins. Although the high-q2 hint may be explained by new short-ranged interactions, the low-q2 one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb’s central value of \( {R}_{K^{*}} \) in the low-q2 bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately 10 MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential BK*e+e rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential BKe+e rate and R K , may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-q2 anomaly increases in significance, then the case for an experimental origin of the lepton-flavor universality violating anomalies would be strengthened. To further explore this, we also point out that, in analogy to J/ψ decays, e+e and μ+μ decays of ϕ mesons can be used as a cross check of lepton-flavor universality by LHCb with 5 fb−1 of integrated luminosity.

Keywords

Beyond Standard Model Heavy Quark Physics 

Notes

Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.

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Copyright information

© The Author(s) 2018

Authors and Affiliations

  • Wolfgang Altmannshofer
    • 1
  • Michael J. Baker
    • 2
  • Stefania Gori
    • 1
  • Roni Harnik
    • 3
  • Maxim Pospelov
    • 4
    • 5
    • 7
  • Emmanuel Stamou
    • 6
  • Andrea Thamm
    • 7
  1. 1.Department of PhysicsUniversity of CincinnatiCincinnatiU.S.A.
  2. 2.Physik-InstitutUniversität ZürichZürichSwitzerland
  3. 3.Theoretical Physics DepartmentFermilabBataviaU.S.A.
  4. 4.Department of Physics and AstronomyUniversity of VictoriaVictoriaCanada
  5. 5.Perimeter Institute for Theoretical PhysicsWaterlooCanada
  6. 6.Enrico Fermi InstituteUniversity of ChicagoChicagoU.S.A.
  7. 7.Theoretical Physics DepartmentCERNGenevaSwitzerland

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