$U(1)_{B_3-L_2}$ Explanation of the Neutral Current $B-$Anomalies

Abstract

We investigate a speculative short-distance force, proposed to explain discrepancies observed between measurements of certain neutral current decays of B hadrons and their Standard Model predictions. The force derives from a spontaneously broken, gauged U (1) B3−L2 extension to the Standard Model, where the extra quantum numbers of Standard Model fields are given by third family baryon number minus second family lepton number. The only fields beyond those of the Standard Model are: three right-handed neutrinos, a gauge field associated with U (1) B3−L2 and a Standard Model singlet complex scalar which breaks U (1) B3−L2 , a 'flavon'. This simple model, via interactions involving a TeV scale force carrying Z vector boson, can successfully explain the neutral current B−anomalies whilst accommodating other empirical constraints. In an ansatz for fermion mixing, a combination of upto-date B−anomaly fits, LHC direct Z search limits and B s − B s mixing bounds imply that M Z > 1.9 TeV at the 95% confidence level. The model possesses a flavonstrahlung signal, where pp collisions produce a Z and a flavon, which subsequently decays into two Higgs bosons.

Muon $(g-2)$ and Flavor Puzzles in the $U(1)^{}_{X}$-gauged Leptoquark Model

“…The calculations of the restrictions on various Z models using the ATLAS results have been performed in plenty of literature, see, for example, Refs. [105,106,185], drawing the conclusion that a heavy Z boson with m Z 2 TeV will not exceed the LHC upper bounds. In this paper, instead of rigorous calculations, we just comment that one can find the allowed parameter space with m Z O(1) TeV that simultaneously explains the R K ( * ) anomaly and escapes the constraints from direct Z searches at LHC.…”

“…The above flavor anomalies, if confirmed by more accurate measurements, will be likely to call for explanations from NP. One intriguing way is to introduce the flavor-dependent U (1) X gauge symmetry [97][98][99][100][101][102][103][104][105][106][107][108]. The Z gauge boson associated with the U (1) X symmetry couples nonuniversally to different generations of quarks and leptons.…”

Frugal $U(1)_X$ models with non-minimal flavor violation for $b \to s \ell \ell$ anomalies and neutrino mixing

“…These parameters can be further constrained by collider searches and the neutral meson mixing data, which we describe in the following subsections. The constraints from neutrino trident production are sub-leading for the relevant mass-coupling range of Z [48], and electroweak precision constraints can be evaded when Z − Z mixing is taken to be small [59] and the other NP particles are decoupled; these constraints are not included in our analysis.…”

“…Several papers [28,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] have focused on U (1) X models as the solutions to the b → s anomalies, either in isolation or by combining them with some other well-motivated SM problems, like neutrino masses, dark matter, fermion mass heirarchy, etc. With the current stringent colliders constraints [31,32,51,52], the models have increasingly focused their attention on the scenarios where the collider constraints can be minimized.…”

“…With the current stringent colliders constraints [31,32,51,52], the models have increasingly focused their attention on the scenarios where the collider constraints can be minimized. Examples of these include the models with only third generation of quarks charged under the new gauge symmetry [37,43,44,48], and models with vector-like additional quarks charged under the new symmetry [34,37]. Some of the recent works have combined U (1) X symmetry and leptoquarks for simultaneously explaning b → s anomalies and the muon g − 2 discrepancy [53].…”