Neutral gauge boson contributions to the dimuon charge asymmetry in B decays

Abstract

Recently, the DØ Collaboration measured the CP-violating like-sign dimuon charge asymmetry in neutral B decays, finding a 3.2σ difference from the standard-model (SM) prediction. A non-SM charge asymmetry a s sl suggests a newphysics (NP) contribution to B s -B s mixing. In this case, in order to explain the measured value of a s sl within its 1σ range, NP must be present in Γ s 12 , the absorptive part of the mixing. In this paper, we examine whether such an explanation is possible in models with flavor-changing Z (ZFCNC) or Z ′ (Z ′ FCNC) gauge bosons. The models must also reproduce the measured values of the indirect CP asymmetry S ψφ in B s → J/ψφ, and ∆Γ s , the B s -B s width difference. We find that the ZFCNC model cannot reproduce the present measured values of S ψφ and a s sl within their 1σ ranges. On the other hand, in the Z ′ FCNC model, the values of all three observables can be simultaneously reproduced.

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

“…Thus, the NP that contributes to Γ NP 12 has to do so via the interaction b → sτ + τ − , but without affecting related decays like b → se + e − or b → sµ + µ − [15]. This can be achieved only in a limited subset of models, for example those with second and third generation scalar leptoquarks, R-parity violating supersymmetry [4], or extra Z ′ bosons [7]. It turns out that the former can provide enough contribution to Γ NP 12 to increase ∆Γ s up to its current experimental upper bound [4,5].…”

“…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].…”

CP violation in the Bs0 system

“…in (Bertolini et al, 2014;Lee and Nam, 2012); extended gauge sectors were discussed e.g. in (Alok et al, 2011;Chang et al, 2014Chang et al, , 2011Fox et al, 2011;Kim et al, 2013;Li et al, 2012;Sahoo et al, 2011Sahoo et al, , 2013; additional fermions 16 which were discussed e.g. in (Alok and Gangal, 2012;Botella et al, 2012).…”

Randall-Sundrum corrections to the width difference andCP-violating phase inBs0-meson decays

“…Note that this is not a general statement about NP models. If there is a tree-level transition sb →τ τ mediated by light NP particles in the range of ∼ 100 GeV, the double NP insertion becomes comparable to the SM diagrams [34]. Possible candidates are scalar leptoquarks [9,35].…”