A multi-charged particle model with local $U(1)_{\mu - \tau}$ to explain muon $g-2$, flavor physics, and possible collider signature

We consider a model with multi-charged particles including vector-like fermions and a charged scalar under a local $U(1)_{\mu - \tau}$ symmetry. We search for allowed parameter region explaining muon anomalous magnetic moment (muon $g-2$) and $b \to s \ell^+ \ell^-$ anomalies, satisfying constraints from the lepton flavor violations, $Z$ boson decays, meson anti-meson mixing and collider experiments. Carrying out numerical analysis, we explore the typical size of the muon $g-2$ and Wilson coefficients to explain $b \to s \ell^+ \ell^-$ anomalies in our model when all other experimental constraints are satisfied. We then discuss the collider physics of the multicharged vectorlike fermions, considering some benchmark points in the allowed parameter space. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Addressing the CKM unitarity problem with a vector-like up quark

We point out that hints of deviations from unitarity in the first row of the CKM matrix may be explained by the presence of a single vector-like top. We study how the stringent experimental constraints arising from CP Violation in the kaon sector and from meson mixing such as $$ {D}^0\hbox{-} {\overline{D}}^0,{K}^0\hbox{-} {\overline{K}}^0 $$ D 0 ‐ D ¯ 0 , K 0 ‐ K ¯ 0 and $$ {B}_{d,s}^0\hbox{-} {\overline{B}}_{d,s}^0 $$ B d , s 0 ‐ B ¯ d , s 0 can be satisfied in the proposed framework. In order for the deviations from unitarity to be of the required size while keeping the theory perturbative, the new top quark should have a mass mT ≲ 7 TeV which could be probed in upcoming experiments at the energy frontier.

Exploring charm decays with missing energy in leptoquark models

We investigate the possibility that scalar leptoquarks generate consequential effects on the flavor-changing neutral-current decays of charmed hadrons into final states with missing energy "Image missing" carried away by either standard model or sterile neutrinos. We focus on scenarios involving the R2, $$ {\tilde{R}}_2 $$ R ˜ 2 , and $$ {\overline{S}}_1 $$ S ¯ 1 leptoquarks and take into account various pertinent constraints, learning that meson-mixing ones and those inferred from collider searches can be of significance. We find in particular that the branching fractions of charmed meson decays D →"Image missing", M = π, ρ, and Ds→"Image missing" and singly charmed baryon decays $$ {\Lambda}_c^{+} $$ Λ c + →"Image missing" and Ξc→"Image missing" are presently allowed to attain the 10−7-10−6 levels if induced by R2 and that the impact of $$ {\tilde{R}}_2 $$ R ˜ 2 is comparatively much less. In contrast, the contributions of $$ {\overline{S}}_1 $$ S ¯ 1 , which couples to right-handed up-type quarks and the sterile neutrinos, could lead to branching fractions as high as order 10−3. This suggests that these charmed hadron decays might be within reach of the BESIII and Belle II experiments or future super charm-tau factories and could serve as potentially promising probes of leptoquark interactions with sterile neutrinos.

Averages of b-hadron, c-hadron, and $$\tau $$-lepton properties as of 2018

This paper reports world averages of measurements of b-hadron, c-hadron, and $$\tau $$ τ -lepton properties obtained by the Heavy Flavour Averaging Group using results available through September 2018. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, $$C\!P$$ C P violation parameters, parameters of semileptonic decays, and Cabibbo–Kobayashi–Maskawa matrix elements.

Flavour Anomalies in a U(1) SUSY Extension of the SM

Flavour anomalies have attracted a lot of attention over recent years as they provide unique hints for possible New Physics. Here, we consider a supersymmetric (SUSY) extension of the Standard Model (SM) with an additional anomaly-free gauge U(1) group. The key feature of our model is the particular choice of non-universal charges to the gauge boson Z′, which not only allows a relaxation of the flavour discrepancies but, contrary to previous studies, can reproduce the SM mixing matrices both in the quark and lepton sectors. We pay special attention to the latter and explicitly enumerate all parameters relevant for our calculation in the low-energy effective theory. We find regions in the parameter space that satisfy experimental constraints on meson mixing and LHC Z′ searches and can alleviate the flavour anomalies. In addition, we also discuss the predictions for lepton-flavour violating decays B+→K+μτ and B+→K+eτ.