Bdecay anomalies in an effective theory

Abstract

We investigate how far a new physics scenario affecting primarily the third-generation fermions can ameliorate the tension between B decay observables and Standard Model expectations. Adopting a modelindependent approach, we find that among the three observables that show signs of such a tension, viz., the branching fractions for B þ ! , B d ! DðD Ã Þ, and the like-sign dimuon anomaly in neutral B decays, the first two can be explained adequately, while there is only a marginal improvement for the third. As a spin-off, it is shown that one can also accommodate a change in the branching fraction of the Higgs boson to a lepton pair from the Standard Model expectation, if such a change is established in future data.

Anomalous enhancement observed inB→D(*)τν¯τdecays

“…In the infinite heavy quark mass limit, formalized by the heavy quark effective theory (HQET), the form factors in (7)(8) can all be related to the Isgur-Wise function ξ [28]. The result is known [29,30]: expressing F 1 (q 2 ) and F 0 (q 2 ) in terms of two other form factors h + (w) and h − (w):…”

“…The measurements have been estimated to deviate at the global level of 3.4σ with respect to SM predictions [1,2]. Therefore, there is the possibility that semileptonic processes involving heavy quarks and the τ lepton are unveiling the effects of particles with large couplings to the heavier fermions, as it is natural for charged scalars which could contribute to the tree-level b → c ν transitions [2][3][4][5][6][7][8][9]. Before the observation of these possible hints of new physics (NP) in semileptonic b → c decays, the first experimental analyses of the purely leptonic B − → τ −ν τ mode also reported an excess of events.…”

Reconciling anomalous measurements inBs−B¯smixing: The role ofCPT-conserving andDighe1, Ghosh2, Kundu3 et al. 2011Phys. Rev. DSelf Cite

“…The resolutions of the above anomalies, separately or simultaneously, have been discussed in the context of specific NP models: a scalar leptoquark model [4,5], models with an extra flavor-changing neutral gauge boson Z ′ or R-parity violating supersymmetry [6,7], two-Higgs doublet model [8,9], models with a fourth generation of fermions [10,11], supersymmetric grand unified models [12], supersymmetric models with split sfermion generations [13] or models with a very light spin-1 particle [14]. Possible four-fermion effective interactions that are consistent with the data have been analyzed by [15] and the results are consistent with [5].…”

SemileptonicB→D¯transition in a nuclear medium

“…After the BABAR [1] measurement of the ratio of branching fractions in τ and ℓ = µ, e channels, i.e. R(D) = B(B → Dτ − ν τ )/B(B → Dℓ − ν ℓ ) = 0.440 ± 0.058 ± 0.042 which deviates with the standard model expectations with a 3.4 σ, this channel together with a similar anomaly in B → D * transition have raised interests to study these channels via different models (for some of them see [2][3][4][5][6][7][8][9][10][11][12] and references therein).…”