A closer look at the R sub( )Dand R sub( )Danomalies

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The measurement of R sub( )D(R sub( )D, the ratio of the branching fraction of ... to that of ..., shows 1.9 sigma (3.3 sigma ) deviation from its Standard Model (SM) prediction. The combined deviation is at the level of 4 s...

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Bibliographic Details
Published in:The journal of high energy physics 2017-01, Vol.2017 (1), p.1-37
Main Authors: Bardhan, Debjyoti, Byakti, Pritibhajan, Ghosh, Diptimoy
Format: Article
Language:English
Subjects:
Asymmetry
Decay
Deviation
Helicity
Invariants
Mathematical models
Operators
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Summary:(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The measurement of R sub( )D(R sub( )D, the ratio of the branching fraction of ... to that of ..., shows 1.9 sigma (3.3 sigma ) deviation from its Standard Model (SM) prediction. The combined deviation is at the level of 4 sigma according to the Heavy Flavour Averaging Group (HFAG). In this paper, we perform an effective field theory analysis (at the dimension 6 level) of these potential New Physics (NP) signals assuming SU(3) sub(C) SU(2) sub(L) U(1) sub(Y) gauge invariance. We first show that, in general, R sub( )Dand R sub( )Dare theoretically independent observables and hence, their theoretical predictions are not correlated. We identify the operators that can explain the experimental measurements of R sub( )Dand R sub( )Dindividually and also together. Motivated by the recent measurement of the tau polarisation in ... decay, P sub( ) tau D super(*)) by the Belle collaboration, we study the impact of a more precise measurement of P sub( ) tau D super(*)) (and a measurement of P sub( ) tau D)) on the various possible NP explanations. Furthermore, we show that the measurement of R sub( )Din bins of q super(2), the square of the invariant mass of the lepton-neutrino system, along with the information on tau polarisation and the forward-backward asymmetry of the tau lepton, can completely distinguish the various operator structures. We also provide the full expressions of the double differential decay widths for the individual tau helicities in the presence of all the 10 dimension-6 operators that can contribute to these decays.
ISSN:1029-8479
DOI:10.1007/JHEP01(2017)125