Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAn Anomaly-free Atlas: charting the space of flavour-dependent gauged $U(1)$ extensions of the Standard Model
60
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Spontaneously broken, flavour-dependent, gauged $U(1)$ extensions of the Standard Model (SM) have many phenomenological uses. We chart the space of solutions to the gauge anomaly cancellation equations in such extensions, for both the SM chiral fermion content and the SM plus (up to) three right-handed neutrinos (SM$ u_R$). Methods from Diophantine analysis allow us to efficiently index the solutions arithmetically, and produce the complete solution space in particular cases. In order to solve the general case, we build a computer program which cycles through possible $U(1)$ charge assignments, providing all solutions for charges up to some pre-defined maximum absolute charge. Lists of anomaly-free $U(1)$ charge assignments result, which corroborate the results of our Diophantine analysis. We make these lists, which may be queried for further desirable properties, publicly available. This previously uncharted space of anomaly-free charge assignments has been little explored until now, paving the way for future model building and phenomenological studies.
rate research
Read More
Extensions of the minimal supersymmetric standard model (MSSM) gauge group abound in the literature. Several of these include an additional $U(1)_X$ gauge group. Chiral fermions charge assignments under $U(1)_X$ are constrained to cancel local anomalies in the extension and they determine the structure and phenomenology of it. We provide all anomaly-free charge assignments up to a maximum absolute charge of $Q_text{max}=10$, assuming that the chiral superfield content of the model is that of the MSSM plus up to three Standard Model (SM) singlet superfields. The fermionic components of these SM singlets may play the r^{o}le of right-handed neutrinos, whereas one of the scalar components may play the r^{o}le of the flavon, spontaneously breaking $U(1)_X$. Easily scanned lists of the charge assignments are made publicly available on Zenodo. For the case where no restriction is placed upon $Q_text{max}$, we also provide an analytic parameterisation of the general solution using simple techniques from algebraic geometry.
We investigate asymptotically safe extensions of the Standard Model with new matter fields arising in the TeV energy range. The new sector contains singlet scalars and vector-like fermions in representations which permit Yukawa interactions with the Standard Model leptons. Phenomenological implications are explored including charged lepton flavour violation, Drell-Yan processes and lepton anomalous magnetic moments. For the latter, we find that BSM contributions can be sizeable enough to explain the present experimental discrepancies of the electron and muon anomalous magnetic moments with the Standard Model.
The question of whether classically conformal modifications of the standard model are consistent with experimental obervations has recently been subject to renewed interest. The method of Gildener and Weinberg provides a natural framework for the study of the effective potential of the resulting multi-scalar standard model extensions. This approach relies on the assumption of the ordinary loop hierarchy $lambda_text{s} sim g^2_text{g}$ of scalar and gauge couplings. On the other hand, Andreassen, Frost and Schwartz recently argued that in the (single-scalar) standard model, gauge invariant results require the consistent scaling $lambda_text{s} sim g^4_text{g}$. In the present paper we contrast these two hierarchy assumptions and illustrate the differences in the phenomenological predictions of minimal conformal extensions of the standard model.
We propose a one-loop induced radiative neutrino mass model with anomaly free flavour dependent gauge symmetry: $mu$ minus $tau$ symmetry $U(1)_{mu-tau}$. A neutrino mass matrix satisfying current experimental data can be obtained by introducing a weak isospin singlet scalar boson that breaks $U(1)_{mu-tau}$ symmetry, an inert doublet scalar field, and three right-handed neutrinos in addition to the fields in the standard model. We find that a characteristic structure appears in the neutrino mass matrix: two-zero texture form which predicts three non-zero neutrino masses and three non-zero CP-phases from five well measured experimental inputs of two squared mass differences and three mixing angles. Furthermore, it is clarified that only the inverted mass hierarchy is allowed in our model. In a favored parameter set from the neutrino sector, the discrepancy in the muon anomalous magnetic moment between the experimental data and the the standard model prediction can be explained by the additional neutral gauge boson loop contribution with mass of order 100 MeV and new gauge coupling of order $10^{-3}$.
In this thesis we study some theoretical and phenomenological aspects of classical conformal symmetry in specific extensions of the SM. We consider both supersymmetric and non supersymmetric cases. We discuss the perturbative structure of the superconformal anomaly effective action. We show that the manifestation of the anomaly is in the presence of massless intermediate states in correlators involving the Ferrara-Zumino supercurrent with two vector supercurrents. This universal feature is typical both of chiral and conformal anomalies. These results are used in a study of a possible extension of the SM with a dilaton, deriving some bounds on a possible conformal scale. Then we turn to investigate a specific superconformal theory, the TNMSSM, which extends the MSSM with one extra triplet and a scalar singlet superfield. The manifestation of the classical conformal symmetry in this model is in the existence of a very light pseudoscalar in the physical spectrum. We study the main proprieties of this state and its potential discovery at the LHC. In the last part of this work we discuss an application of the graviton-photon-photon vertex to gravitational lensing for a Schwarzschild background. In particular, we introduce the notion of a semiclassical lens equation for the deflection of a photon nearing the horizon of a black hole.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
