Standard model anomalies: lepton flavour non-universality, g − 2 and W-mass

Abstract

We critically analyze the body of results that hints to the existence of New Physics from possible violations of lepton universality observed by the LHCb experiment in the μ/e ratios RK and $$ {R}_{K^{\ast }} $$ R K ∗ to the g − 2 lepton anomalies. The analysis begins with a theoretical, in depth, study of the μ/e ratios RK and $$ {R}_{K^{\ast }} $$ R K ∗ as well as the process Bs→ μ+μ−. Here we consider the impact of complex Wilson coefficients and derive constraints on their imaginary and real parts. We then move to a comprehensive comparison with experimental results. We show that, by fitting a single Wilson coefficient, the deviations from the Standard Model are at the 4.7σ level when including only the hadronic insensitive observables while it increases to 6.1σ when including also the hadronic sensitive ones. When switching on all relevant Wilson coefficients and combining both hadronic sensitive and insensitive data into the fit, the deviation from the Standard Model peaks at 7.2σ and decreases at the 4.9σ level if we assume that the central values of RK and $$ {R}_K^{\ast } $$ R K ∗ are taken to be unity. We further estimate other unaccounted for SM contributions and show that their inclusion still requires New Physics to fit the data. We then introduce the g − 2 lepton anomalies as well as the most recent W-mass results. Different theoretical models are considered that can explain the discrepancies from the Standard Model. In the final part of our work we estimate the impact of the forthcoming data from LHCb (coming from LHC Run3) and Belle II, when it will have accumulated about 5 ab−1.

Anomalous and axial Z′ contributions to g−2

“…After parametrizing the anomalous three-gauge-boson couplings, we evaluate their contribution to the g−2 of the muon, first presented in general terms without using any 45,51,52,[84][85][86][87][88][96][97][98], without including the anomalous coupling. 6 In the presence of more than one Z s this is no longer the case [116].…”

Gravitational wave signals from leptoquark-induced first-order electroweak phase transitions

“…From the experimental side, the existence of leptoquarks is strongly indicated by lepton flavour universality violation (LFUV) in semi-leptonic B decay [10][11][12][13][14][15]. Besides LFUV, leptoquarks can also be related to a wide variety of phenomena beyond the standard model, including the muon g − 2 [16][17][18][19][20][21], the neutrino mass [22][23][24][25][26] and the W boson mass [27][28][29][30][31][32].…”

Study of quantum coherence, lifetime and electromagnetic properties of massive neutrinos

“…In (14), σ x is the effective size of the detection region that takes into account space and time intervals in which the neutrino and all particles in the detection process are overlapped. Since the neutrino that reached the detection process carries information about the production process, σ x takes into account features of both production and detection, in a similar way to σ p -the effective resolution with which the detection process can measure momentum: 7…”

“…Both are related by σ x σ p = 1 2 . Squaring the amplitude in (14) and integrating out the T dependence, we obtain…”

“…The fundamental questions the standard model leaves unanswered are neutrino masses and mixings (neutrinos are massless in the SM) [6], dark matter [7], dark energy [8], matterantimatter asymmetry [9], strong CP [10], Naturalness [11], GUT [12], flavor puzzle [13] and a couple of experimental anomalies [14].…”