Search results for " Standard Model"
showing 10 items of 645 documents
Neutrino oscillations and Non-Standard Interactions
2017
Current neutrino experiments measure the neutrino mixing parameters with an unprecedented accuracy. The upcoming generation of experiments will be sensitive to subdominant effects that can give information on the unknown neutrino parameters: the Dirac CP-violating phase, the mass ordering and the $\theta_{23}$ octant. Determining the exact values of neutrino mass and mixing parameters is crucial to test neutrino models and flavor symmetries. In the first part of this review, we summarize the current status of neutrino oscillation parameters. We consider the most recent data from solar experiments and the atmospheric data from Super-Kamiokande, IceCube and ANTARES. We implement the data from…
New ambiguity in probing CP violation in neutrino oscillations
2016
If neutrinos get mass via the seesaw mechanism the mixing matrix describing neutrino oscillations can be effectively non-unitary. We show that in this case the neutrino appearance probabilities involve a new CP phase, phi, associated to non-unitarity. This leads to an ambiguity in extracting the "standard" three--neutrino phase delta_CP, which can survive even after neutrino and antineutrino channels are combined. Its existence should be taken into account in the planning of any oscillation experiment aiming at a robust measurement of delta_CP.
Lepton Number Violation in Higgs Decay at LHC
2015
We show that within the Left-Right symmetric model, lepton number violating decays of the Higgs boson can be discovered at the LHC. The process is due to the mixing of the Higgs with the triplet that breaks parity. As a result, the Higgs can act as a gateway to the origin of heavy Majorana neutrino mass. To assess the LHC reach, a detailed collider study of the same-sign di-leptons plus jets channel is provided. This process is complementary to the existing nuclear and collider searches for lepton number violation and can probe the scale of parity restoration even beyond other direct searches.
Search for extra dimensions in diphoton events from proton-proton collisions at root s=7 TeV in the ATLAS detector at the LHC
2013
The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton–proton collisions at √s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9fb[superscript −1]. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani–Hamed, Dimopoulos and Dvali, 95% confidence le…
Vector boson scattering: Recent experimental and theory developments
2018
This document summarises the talks and discussions happened during the VBSCan Split17 workshop, the first general meeting of the VBSCan COST Action network. This collaboration is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.
Dark matter-neutrino interactions through the lens of their cosmological implications
2018
Dark matter and neutrinos provide the two most compelling pieces of evidence for new physics beyond the Standard Model of Particle Physics but they are often treated as two different sectors. The aim of this paper is to determine whether there are viable particle physics frameworks in which dark matter can be coupled to active neutrinos. We use a simplified model approach to determine all possible renormalizable scenarios where there is such a coupling, and study their astrophysical and cosmological signatures. We find that dark matter-neutrino interactions have an impact on structure formation and lead to indirect detection signatures when the coupling between dark matter and neutrinos is …
Higgs-portal assisted Higgs inflation with a sizeable tensor-to-scalar ratio
2014
We show that the Higgs portal interactions involving extra dark Higgs field can save generically the original Higgs inflation of the standard model (SM) from the problem of a deep non-SM vacuum in the SM Higgs potential. Specifically, we show that such interactions disconnect the top quark pole mass from inflationary observables and allow multi-dimensional parameter space to save the Higgs inflation, thanks to the additional parameters (the dark Higgs boson mass $m_{\phi}$, the mixing angle $\alpha$ between the SM Higgs $H$ and dark Higgs $\Phi$, and the mixed quartic coupling) affecting RG-running of the Higgs quartic coupling. The effect of Higgs portal interactions may lead to a larger t…
Hadronic τ Decays as New Physics Probes in the LHC Era
2019
We analyze the sensitivity of hadronic tau decays to non-standard interactions within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the $\tau \to \pi\pi\nu_\tau$ channel representing an unexpected powerful New Physics probe. We find that the ratios of non-standard couplings to the Fermi constant are bound at the sub-percent level. These bounds are complementary to the ones from electroweak precision observable…
Progress towards the first measurement of charm baryon dipole moments
2021
Electromagnetic dipole moments of short-lived particles are sensitive to physics within and beyond the Standard Model of particle physics but have not been accessible experimentally to date. To perform such measurements it has been proposed to exploit the spin precession of channeled particles in bent crystals at the LHC. Progress that enables the first measurement of charm baryon dipole moments is reported. In particular, the design and characterization on beam of silicon and germanium bent crystal prototypes, the optimization of the experimental setup, and advanced analysis techniques are discussed. Sensitivity studies show that first measurements of $\Lambda_c^+$ and $\Xi_c^+$ baryon dip…
CP Violation in Correlated Production and Decay of Unstable Particles
2011
We study resonant CP-violating Einstein--Podolsky--Rosen correlations that may take place in the production and decay of unstable scalar particles at high-energy colliders. We show that as a consequence of unitarity and CPT invariance of the S-matrix, in 2 --> 2 scatterings mediated by mixed scalar particles, at least three linearly independent decay matrices associated with the unstable scalar states are needed to obtain non-zero CP-odd observables that are also odd under C-conjugation. Instead, for the correlated production and decay of two unstable particle systems in 2 --> 4 processes, we find that only two independent decay matrices are sufficient to induce a net non-vanishing CP…