Search results for "STANDARD MODEL"
showing 10 items of 1206 documents
Oscillations, neutrino masses and scales of new physics
1999
We show that all the available experimental information involving neutrinos can be accounted for within the framework of already existing models where neutrinos have zero mass at tree level, but obtain a small Dirac mass by radiative corrections.
Heavy Resonances in the Electroweak Effective Lagrangian
2015
As a first step towards the construction of a general electroweak effective Lagrangian incorporating heavy states, we present here a simplified version where only vector and axial-vector spin-1 triplets are involved. We adopt an effective field theory formalism, implementing the electroweak chiral symmetry breaking SU(2)L x SU(2)R -> SU(2)L+R, which couples the heavy states to the SM fields. At low energies, the heavy degrees of freedom are integrated out from the action and their effects are hidden in the low-energy couplings of the Electroweak Effective Theory, which can be tested experimentally. Short-distance constraints are also implemented, requiring a proper behaviour in the high-…
Probing Supersymmetric Grand Unification through Flavor Physics
2007
Flavor Changing Neutral Current (FCNC) and CP violating processes are a powerful tool to probe the Standard Model (SM) and, hence, to constrain or obtain indirect hints of New Physics (NP) beyond it. Within Supersymmetric Grand Unified theories it is generally possible to link processes occurring in the leptonic and hadronic sectors; thus, their correlated analysis provides a very interesting low energy test for a Grand Unified theory at high energies. Similarly to the FCNC decays, we also show that the Lepton Flavor Universality tests in low-energy systems ( K l 2 and π l 2 ) offer a unique opportunity in shedding light on physics beyond the Standard Model; the smallness of NP effects is m…
Predicting charged lepton flavor violation from 3-3-1 gauge symmetry
2015
7 pages.- 2 figures.- v2: discussion extended
Yukawa sector of multi-Higgs-doublet models in the presence of Abelian symmetries
2013
A general method for classifying the possible quark models of a multi-Higgs-doublet model, in the presence of Abelian symmetries, is presented. All the possible sets of textures that can be present in a given sector are shown, thus turning the determination of the flavor models into a combinatorial problem. Several symmetry implementations are studied for two and three Higgs doublet models. Some models' implementations are explored in great detail, with a particular emphasis on models known as Branco-Grimus-Lavoura and nearest-neighbor-interaction. Several considerations on the flavor changing neutral currents of multi-Higgs models are also given.
Lepton flavor violation beyond the MSSM
2015
Most extensions of the Standard Model lepton sector predict large lepton flavor violating rates. Given the promising experimental perspectives for lepton flavor violation in the next few years, this generic expectation might offer a powerful indirect probe to look for new physics. In this review we will cover several aspects of lepton flavor violation in supersymmetric models beyond the Minimal Supersymmetric Standard Model. In particular, we will concentrate on three different scenarios: high-scale and low-scale seesaw models as well as models with R-parity violation. We will see that in some cases the LFV phenomenology can have characteristic features for specific scenarios, implying that…
CP violating lepton asymmetries in left-right models
1998
Lepton charge asymmetries can be used as an alternative means of searching for new physics. They are interesting because they are small in the Standard Model and therefore, necessarily evidence new physics. In this work we explore the use of lepton asymmetries as a probe of the flavour structure of the left-right symmetric model with spontaneous CP violation. We find that new physics may enhance the magnitude of $a_{SL}$ up to the precent level within the appropiate parameter space.
Extended Black Box Theorem for Lepton Number and Flavor Violating processes
2006
We revisit the well known "Black Box" theorem establishing a fundamental relation between the amplitude of neutrinoless double beta decay and the effective Majorana neutrino mass. We extend this theorem to the general case of arbitrary lepton number and lepton flavor violating (LFNV) processes and to the three generation Majorana neutrino mass matrix. We demonstrate the existence of a general set of one-to-one correspondence relations between the effective operators generating these processes, and elements of the neutrino mass matrix, such that if one of these two quantities vanishes the other is guaranteed to vanish as well, and moreover, if one of these quantities is non-zero the other is…
Searching for new physics in leptonic decays of bottomonium
2002
New Physics can show up in various well-known processes already studied in the Standard Model, in particular by modifying decay rates to some extent. In this work, I examine leptonic decays of $\Upsilon$ vector resonances of bottomonium below $B\bar{B}$ production, subsequent to a magnetic dipole radiative structural transition of the vector resonance yielding a pseudoscalar continuum state, searching for the existence of a light Higgs-like neutral boson that would imply a slight but experimentally measurable breaking of lepton universality.
Hints of new physics in bottomonium decays and spectroscopy
2004
A non-standard light CP-odd Higgs boson could induce a slight (but observable) lepton universality breakdown in Upsilon leptonic decays. Moreover, the mixing between such a pseudoscalar Higgs and $\eta_b$ states might shift the mass levels of the latter, thereby changing the values of the $m_{\Upsilon(nS)}-m_{\eta_b(nS)}$ splittings predicted in the standard model. Besides, also the $\eta_b$ width could be broader than expected, with potentially negative consequences for its discovery in both $e^+e^-$ and hadron colliders.