Search results for "Beyond the standard model"
showing 10 items of 453 documents
Interference effect in lepton number violating and conserving meson decays for a left-right symmetric model
2021
We study the effect of interference on the lepton number violating~(LNV) and lepton number conserving~(LNC) three-body meson decays $M_1^{+}\to l_i^{+} l_j^{\pm}\pi^{\mp}$, that arise in a TeV scale Left Right Symmetric model~(LRSM) with degenerate or nearly degenerate right handed~(RH) neutrinos. LRSM contains three RH neutrinos and a RH gauge boson. The RH neutrinos with masses in the range of $M_N \sim$ (MeV - few GeV) can give resonant enhancement in the semi-leptonic LNV and LNC meson decays. In the case, where only one RH neutrino contributes to these decays, the predicted new physics branching ratio of semi-leptonic LNV and LNC meson decays $M_1^{+}\to l_i^{+} l_j^{+}\pi^{-}$ and $M_…
Search at the Mainz Microtron for light massive gauge bosons relevant for the muon g-2 anomaly.
2014
A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40 MeV/c^{2} to 300 MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge …
Search for supersymmetry in events with four or more leptons in s=13 TeV pp collisions with ATLAS
2018
Results from a search for supersymmetry in events with four or more charged leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclu…
Theory of Neutrino Masses and Mixing
2002
In this talk I will review our present knowledge on neutrino masses and mixing trying to emphasize what has been definitively proved and what is in the process of being probed. I will also discuss the most important theoretical implications of these results: the existence of new physics, the estimate of the scale of this new physics as well as some other possible consequences such as leptogenesis origin of the baryon asymmetry.
B physics and extra dimensions
2003
We compute the dominant new physics contributions to the processes Z -> b b and B - B in the context of two representative models with extra dimensions. The main thrust of the calculations focuses on how to control the effects of the infinite tower of Kaluza-Klein modes inside the relevant one-loop diagrams. By comparing the results with the existing experimental data, most importantly those for Rb, we show that one may derive interesting lower bounds on the size of the compactification scale Mc.
Neutrinos properties beyond the Standard Model
1997
The present observational status of neutrino physics is sketched, with emphasis on the hints that follow from solar and atmospheric neutrino observations, as well as dark matter. I also briefly review the ways to account for the observed anomalies and some of their implications
Standard model large-ETprocesses and searches for new physics at HERA
1999
Existing and missing calculations of standard model processes producing large transverse energy in electron-proton interactions at HERA are reviewed. The adequacy of the existing standard model Monte Carlo programs for generic searches of exotic processes is analyzed.
Proposal for Testing Lepton Universality in Upsilon Decays at a B Factory Running at Υ(3S)
2006
We present a proposal for detecting new physics at a B-factory running at the $\Upsilon(3S)$ resonance by testing lepton universality to the few percent level in the leptonic decays of the $\Upsilon(1S)$ and $\Upsilon(2S)$ resonances tagged by the dipion in the chain decay: $\Upsilon(3S) \to pi^+\pi^-\Upsilon(1S,2S)$; $\Upsilon(1S,2S) \to \ell^+\ell^-$, $\ell=e,\mu,\tau$.
Observable traces of non-metricity: new constraints on metric-affine gravity
2018
Relaxing the Riemannian condition to incorporate geometric quantities such as torsion and non-metricity may allow to explore new physics associated with defects in a hypothetical space-time microstructure. Here we show that non-metricity produces observable effects in quantum fields in the form of 4-fermion contact interactions, thereby allowing us to constrain the scale of non-metricity to be greater than 1 TeV by using results on Bhabha scattering. Our analysis is carried out in the framework of a wide class of theories of gravity in the metric-affine approach. The bound obtained represents an improvement of several orders of magnitude to previous experimental constraints.
ICHEP 2014 Summary: Theory Status after the First LHC Run
2016
A brief overview of the main highlights discussed at ICHEP 2014 is presented. The experimental data confirm that the scalar boson discovered at the LHC couples to other particles as predicted in the Standard Model. This constitutes a great success of the present theoretical paradigm, which has been confirmed as the correct description at the electroweak scale. At the same time, the negative searches for signals of new phenomena tightly constrain many new-physics scenarios, challenging previous theoretical wisdom and opening new perspectives in fundamental physics. Fresh ideas are needed to face the many pending questions unanswered within the Standard Model framework.