Search results for "partícules"
showing 10 items of 522 documents
Charge and magnetic moment of the neutrino in the background field method and in the linear R-xi(L) gauge
1999
We present a computation of the charge and the magnetic moment of the neutrino in the recently developed electro-weak Background Field Method and in the linear $R_{\xi}^L$ gauge. First, we deduce a formal Ward-Takahashi identity which implies the immediate cancellation of the neutrino electric charge. This Ward-Takahashi identity is as simple as that for QED. The computation of the (proper and improper) one loop vertex diagrams contributing to the neutrino electric charge is also presented in an arbitrary gauge, checking in this way the Ward-Takahashi identity previously obtained. Finally, the calculation of the magnetic moment of the neutrino, in the minimal extension of the Standard Model…
Spin, parity and nature of the Xi(1620) resonance
2002
Using a unitary extension of chiral perturbation theory with a lowest-order s -wave SU(3) chiral Lagrangian we study low-energy meson-baryon scattering in the strangeness S = − 2 sector. A scattering-matrix pole is found around 1605 MeV which corresponds to an s -wave Ξ resonance with J P = 1 / 2 − . We identify this resonance with the Ξ ( 1620 ) state, quoted by the Particle Data Group with I = 1 / 2 but with unknown spin and parity. The addition of the S = − 2 state to the recently computed Λ ( 1670 ) , Σ ( 1620 ) , and N ( 1535 ) states completes the octet of J P = 1 / 2 − resonances dynamically generated in this chiral unitary approach.
Dark Matter and the Seesaw Scale
2018
We discuss the possibility to find an upper bound on the seesaw scale using the cosmological bound on the cold dark matter relic density. We investigate a simple relation between the origin of neutrino masses and the properties of a dark matter candidate in a simple theory where the new symmetry breaking scale defines the seesaw scale. Imposing the cosmological bounds, we find an upper bound of order multi-TeV on the lepton number violation scale. We investigate the predictions for direct and indirect detection dark matter experiments, and the possible signatures at the Large Hadron Collider.
Zooming in on neutrino oscillations with DUNE
2018
We examine the capabilities of the DUNE experiment as a probe of the neutrino mixing paradigm. Taking the current status of neutrino oscillations and the design specifications of DUNE, we determine the experiment's potential to probe the structure of neutrino mixing and CP violation. We focus on the poorly determined parameters $\theta_{23}$ and $\delta_{CP}$ and consider both two and seven years of run. We take various benchmarks as our true values, such as the current preferred values of $\theta_{23}$ and $\delta_{CP}$, as well as several theory-motivated choices. We determine quantitatively DUNE's potential to perform a precision measurement of $\theta_{23}$, as well as to test the CP vi…
Evidence for the two pole structure of the Lambda(1405) resonance
2005
The K^- p --> pi^0 pi^0 Sigma^0 reaction is studied within a chiral unitary model. The distribution of pi^0 Sigma^0 states forming the Lambda(1405) shows, in agreement with a recent experiment, a peak at 1420 MeV and a relatively narrow width of Gamma = 38 MeV. The mechanism for the reaction is largely dominated by the emission of a pi^0 prior to the K^- p interaction leading to the Lambda(1405). This ensures the coupling of the Lambda(1405) to the K^- p channel, thus maximizing the contribution of the second state found in chiral unitary theories, which is narrow and of higher energy than the nominal Lambda(1405). This is unlike the pi^- p --> K^0 ��Sigma reaction, which gives more w…
A Brief Discussion on the Performance of the MoEDAL and the LHCf Experiments
2018
The Monopole and Exotics Detector at the LHC (MoEDAL) experiment is an experiment dedicated to searching for beyond standard model (BSM) particles like magnetic monopoles, highly ionizing particles and slow-moving supersymmetric particles. In many ways, this detector complements the BSM searches of ATLAS and CMS. In this document, a brief description of the MoEDAL detector and performance is given. The Large Hadron Collider Forward (LHCf) experiment, on the other hand, is dedicated to measuring the neutral particles produced in the hadronic collision in the very forward region. This document also briefly discusses the LHCf detector and its performance.
Lepton number violation and scalar searches at the LHC
2013
We review the SM extensions with scalar multiplets including doubly- charged components eventually observable as di-leptonic resonances at the LHC. Special emphasis is paid to the limits on LNV implied by doubly- charged scalar searches at the LHC, and to the characterization of the multiplet doubly-charged scalars belong to if they are observed to decay into same-sign charged lepton pairs.
Distinguishing between lepton number violating scalars at the LHC
2013
Scalars with lepton number violating interactions decaying into lepton pairs, as those mediating the see-saw of type II, always include doubly-charged components. If these are observed at the LHC, their electroweak quantum numbers can be determined through their leptonic decays in pair and single production.
Search for Second-Class Currents inτ−→ωπ−ντ
2009
We report an analysis of tau- decaying into omega.pi-.nu_tau with omega -> pi+pi-pi0 using a data sample containing nearly 320 million tau pairs collected with the BABAR detector at the PEP-II B-Factory. We find no evidence for second-class currents and we set an upper limit of 0.69% at 90% confidence level for the fraction of second-class currents in this decay mode.
Search for Dimuon Decays of a Light Scalar Boson in Radiative Transitions Υ→γA0
2009
We search for evidence of a light scalar boson in the radiative decays of the {Upsilon}(2S) and {Upsilon}(3S) resonances: {Upsilon}(2S, 3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} {mu}{sup +}{mu}{sup -}. Such a particle appears in extensions of the Standaard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in the mass range 0.212 {<=} m{sub A{sup 0}} {<=} 9.3 GeV in the samples of 99 x 10{sup 6} {Upsilon}(2S) and 122 x 10{sup 6} {Upsilon}(3S) decays collected by the BABAR detector at the PEP-II B-factory and set stringent upper limits on the effective coupling of the b quark to the A{sup 0}. We also limit the dimuon b…