scholarly journals Exotic leptons: Collider and muon magnetic moment constraints

2015 ◽  
Vol 30 (32) ◽  
pp. 1550187 ◽  
Author(s):  
D. Cogollo

In light of the ongoing effort on reducing the theoretical uncertainties and an upcoming experiment concerning muon magnetic moment, we perform a detailed study of an 3-4-1 electroweak gauge extension of the standard model that contains exotic charged leptons in its spectrum. We discuss flavor changing neutral current, collider and electroweak bounds on the model and derive [Formula: see text] limits using current and projected limits on the muon magnetic moment. In summary, we exclude the masses of new gauge bosons that couple to muons and heavy charged leptons up to 700 GeV. Moreover, we find a projected lower bound on the scale of symmetry breaking to be 2 TeV.

2008 ◽  
Vol 23 (05) ◽  
pp. 347-358 ◽  
Author(s):  
B. B. ŞIRVANLI

We study the exclusive flavor changing neutral current process [Formula: see text] in the leptophobic Z′ model, where charged leptons do not couple to the extra Z′ boson. The branching ratio, as well as, the longitudinal, transversal and normal polarizations are calculated. It has been shown that all these physical observables are very sensitive to the existence of new physics beyond the standard model and their experimental measurements can give valuable information about it.


2019 ◽  
Vol 34 (09) ◽  
pp. 1950048 ◽  
Author(s):  
D. Banerjee ◽  
M. Kumar ◽  
P. Nayek ◽  
S. Sahoo

We investigate [Formula: see text] decays in a nonuniversal [Formula: see text] model derived from the extension of the Standard Model (SM). Considering the [Formula: see text]-mediated flavor-changing neutral current (FCNC) effects, we calculate the branching ratio and forward–backward asymmetry [Formula: see text] for [Formula: see text] decay processes. We compare the obtained results with predictions of the SM and discuss the sensitivity of the observables to [Formula: see text] boson coupling parameters. We find that the branching ratios are enhanced by one order from SM predictions in [Formula: see text] model scenario. We also observe that the variation of forward–backward asymmetry with the [Formula: see text] boson coupling parameters portrays discrimination between NP effects and SM results.


1993 ◽  
Vol 08 (36) ◽  
pp. 3397-3411 ◽  
Author(s):  
DAVID B. CLINE

We review the current studies and future prospects for studies of Flavor Changing Neutral Current (FCNC) processes, emphasizing rare B decays. These experiments will be very sensitive to physics beyond the standard model. A key problem in these studies is the method to trigger the detector. We discuss a novel technique that uses an optical-Cherenkov light trigger to select events with significant impact parameters.


2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Zhaofeng Kang ◽  
Yoshihiro Shigekami

Abstract To address the long-standing (g − 2)μ anomaly via a light boson, in ref. [1] we proposed to extend the standard model (SM) by the local (B − L)23, under which only the second and third generations of fermions are charged. It predicts an invisible Z′ with mass $$ \mathcal{O}(100) $$ O 100 MeV, and moreover it has flavor-changing neutral current (FCNC) couplings to the up-type quarks at tree level. Such a Z′, via KL→ π0 + Z′(→$$ v\overline{v} $$ v v ¯ ) at loop level, may be a natural candidate to account for the recent KOTO anomaly. In this article, we investigate this possibility, to find that Z′ can readily do this job if it is no longer responsible for the (g − 2)μ anomaly. We further find that both anomalies can be explained with moderate tuning of the CP violation, but may contradict the B meson decays.


2018 ◽  
Vol 33 (21) ◽  
pp. 1850125 ◽  
Author(s):  
Soram Robertson Singh ◽  
Barilang Mawlong ◽  
Ritu D’cruz

The rare semileptonic [Formula: see text] and [Formula: see text] decay modes mediated by the [Formula: see text] transition are studied in this paper. We analyze observables such as the differential branching ratio, lepton polarization asymmetry and forward–backward asymmetry within the standard model in the low [Formula: see text] region. We then perform an analysis of the same modes within the 331 or [Formula: see text] model in which a new heavy [Formula: see text] boson contributes. The effects of the [Formula: see text]-mediated flavor-changing neutral current (FCNC) transitions on these modes are investigated by varying the mass [Formula: see text] and the model parameter [Formula: see text]. The new [Formula: see text] couplings are constrained by flavor observables of [Formula: see text] mixing and branching ratio of [Formula: see text]. We find that for some values of these couplings, the observables are quite sensitive to [Formula: see text] effects and deviations from Standard Model can be large.


2012 ◽  
Vol 27 (08) ◽  
pp. 1250043 ◽  
Author(s):  
PRASANTA KUMAR DAS

The Belle collaboration has reported [Formula: see text] for the inclusive decay [Formula: see text]. Recently, the LHCb and the CMS collaboration has released the combined limit [Formula: see text]. The standard model results of the [Formula: see text] and [Formula: see text] are found to be within the 1σ of the experimental result. Taking a conservative viewpoint, we use these decays to constrain the braneworld Randall–Sundrum model. The stabilized radion in the Randall–Sundrum model, which is an electro-weak singlet, can cause the flavor changing neutral current (FCNC) b →s transition at the oneloop level. We investigate the possible impact of a stabilized radion on the above two decays and obtain the possible constraints on the radion vev 〈ϕ〉 for an ultra-light radion.


2019 ◽  
Vol 97 (12) ◽  
pp. 1270-1276
Author(s):  
P. Nayek ◽  
P. Maji ◽  
S. Sahoo

Motivated by the hints of lepton flavor violating (LFV) decays, we study Bd,s → μτ, Bs,d → τe, and τ– → e– + e+ + e– decays in [Formula: see text] model. These LFV decays present interesting patterns that may reveal the shape of new physics beyond the standard model. Considering the effect of both Z- and [Formula: see text]-mediated flavor-changing neutral current we calculate the branching ratios for these decays. We find the branching ratios [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].


2015 ◽  
Vol 42 (8) ◽  
pp. 085002 ◽  
Author(s):  
L G Benitez-Guzmán ◽  
I García-Jiménez ◽  
M A López-Osorio ◽  
E Martínez-Pascual ◽  
J J Toscano

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Jin Sun ◽  
Yu Cheng ◽  
Xiao-Gang He

Abstract General flavor changing Goldstone boson (GB) interactions with fermions from a spontaneous global U(1)G symmetry breaking are discussed. This GB may be the Axion, solving the strong QCD CP problem, if there is a QCD anomaly for the assignments of quarks U(1)G charge. Or it may be the Majoron, producing seesaw Majorana neutrino masses by lepton number violation, if the symmetry breaking scale is much higher than the electroweak scale. It may also, in principle, play the roles of Axion and Majoron simultaneously as far as providing solution for the strong CP problem and generating a small Majorana neutrino masses are concerned. Great attentions have been focused on flavor conserving GB interactions. Recently flavor changing Axion and Majoron models have been studied in the hope to find new physics from rare decays in the intensity frontier. In this work, we will provide a systematic model building aspect study for flavor changing neutral current (FCNC) GB interactions in the fermion sectors, or separately in the quark, charged lepton and neutrino sectors and will identify in detail the sources of FCNC interactions in a class of beyond standard model with a spontaneous global U(1)G symmetry breaking. We also provide a general proof of the equivalence of using physical GB components and GB broken generators for calculating GB couplings to two gluons and two photons, and discuss some issues related to spontaneous CP violation models. Besides, we will also provide some details for obtaining FCNC GB interactions in several popular models, such as the Type-I, -II, -III seesaw and Left-Right symmetric models, and point out some special features in these models.


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