Search results for "Lepton"
showing 10 items of 1512 documents
Higgs CP properties using the tau decay modes at the ILC
2013
We investigate the prospects of determining the CP nature of the 126 GeV neutral spin-0 (Higgs) boson h, discovered at the LHC, at a future linear collider. We consider the production of h by the Higgsstrahlung process and its subsequent decays to tau leptons. We investigate how precisely a possible pseudoscalar component of h can be detected by the measurement of a suitably defined angular distribution, if all major decay modes of the tau lepton are used. From our numerical simulations, we estimate the expected precision to the scalar-pseudoscalar mixing angle, including estimates of the background and of measurement uncertainties, to be 2.8 degree for Higgs-boson production at a center-of…
Natural fourth generation of leptons
2009
We consider implications of a fourth generation of leptons, allowing for the most general mass patterns for the fourth generation neutrino. We determine the constraints due to the precision electroweak measurements and outline the signatures to search for at the LHC experiments. As a concrete framework to apply these results we consider the minimal walking technicolor (MWTC) model where the matter content, regarding the electroweak quantum numbers, corresponds to a fourth generation.
Bound-state dark matter with Majorana neutrinos
2019
We propose a simple scenario in which dark matter (DM) emerges as a stable neutral hadronic thermal relics, its stability following from an exact $\operatorname{U}(1)_D$ symmetry. Neutrinos pick up radiatively induced Majorana masses from the exchange of colored DM constituents. There is a common origin for both dark matter and neutrino mass, with a lower bound for neutrinoless double beta decay. Direct DM searches at nuclear recoil experiments will test the proposal, which may also lead to other phenomenological signals at future hadron collider and lepton flavour violation experiments.
Determining the CP parity of Higgs bosons at the LHC in the $\tau$ to 1-prong decay channels
2008
We propose a method for determining the CP nature of a neutral Higgs boson or spin-zero resonance $\phi$ at the CERN Large Hadron Collider (LHC) in its $\phi\to\tau^{-}\tau^{+}$ decay channel. The method can be applied to any 1-prong $\tau$-decay mode, which comprise the majority of the $\tau$-lepton decays. The proposed observables allow to discriminate between pure scalar and pseudoscalar Higgs-boson states and/or between a CP-conserving and CP-violating Higgs sector. We show for the decays $\tau\to\pi\nu_{\tau}$ that the method maintains its discriminating power when measurement uncertainties are taken into account. The method will be applicable also at a future linear $e^{+}e^{-}$ colli…
A model for right-handed neutrino magnetic moments
2010
A simple extension of the standard model providing Majorana magnetic moments to right-handed neutrinos is presented. The model contains, in addition to the standard model particles and right-handed neutrinos, just a singly charged scalar and a vector-like charged fermion. The phenomenology of the model is analysed and its implications in cosmology, astrophysics and lepton flavour violating processes are extracted. If light enough, the charged particles responsible for the right-handed neutrino magnetic moments could copiously be produced at the Large Hadron Collider.
Are the B decay anomalies related to neutrino oscillations?
2015
5 pages.- 2 figures.- v2: 1 ref. added.- v3: matches
Supersymmetric type-II seesaw mechanism: CERN LHC and leptón flavor violating phenomenology
2008
We study the supersymmetric version of the type-II seesaw mechanism assuming minimal supergravity boundary conditions. We calculate branching ratios for lepton flavor violating (LFV) scalar tau decays, potentially observable at the LHC, as well as LFV decays at low energy, such as l{sub i}{yields}l{sub j}+{gamma}, and compare their sensitivity to the unknown seesaw parameters. In the minimal case of only one triplet coupling to the standard model lepton doublets, ratios of LFV branching ratios can be related unambiguously to neutrino oscillation parameters. We also discuss how measurements of soft SUSY breaking parameters at the LHC can be used to indirectly extract information of the seesa…
Modelling tribimaximal neutrino mixing
2009
We model tribimaximal lepton mixing from first principles in a way that avoids the problem of the vacuum alignment characteristic of such models. This is achieved by using a softly broken A(4) symmetry realized with an isotriplet fermion, also triplet under A(4). No scalar A(4) triplet is introduced. This represents one possible realization of general schemes characterized by the minimal set of either three or five physical parameters. In the three parameter versions the neutrinoless double beta mass parameter m(ee) vanishes, while in the five parameter schemes the absolute scale of neutrino mass, although not predicted, is related to the two Majorana phases. The model realization we discus…
Search for the Standard Model Higgs boson in the decay channel H→ZZ(⁎)→4ℓ with 4.8 fb−1 of pp collision data at s=7 TeV with ATLAS
2012
This Letter presents a search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> l(+)l(-)l(-)+l(')-, where l,l' = e or mu, using proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb(-1). The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for …
Low-mass dileptons at high momenta in ultra-relativistic heavy-ion collisions
1992
Abstract We calculate the emission rate of low-mass dileptons at high momenta from a quark-gluon plasma. We find a large enhancement compared with the naive Born rate. Numerical estimates for relativistic heavy ions collisions at RHIC and LHC suggest, however, that the thermal signal is dominated by the background coming from meson decays and from hadronic bremsstrahlung.