arXiv subjects

Jose W. F. Valle

Publications and source records attributed to Jose W. F. Valle.

At least 37 records · Page 2Linked to original sources

arXiv2014

Radiative neutrino mass in 331 scheme

We propose a new radiative mechanism for neutrino mass generation based on the 3-3-1 electroweak gauge group. Lepton number is a symmetry of the Yukawa sector but spontaneously broken in the gauge sector. As a result light Majorana masses arise from neutral gauge boson exchange at the one-loop level. In addition to the isosinglet neutrinos which may be produced at the LHC through the extended gauge boson "portals", the model contains new isosinglet quarks which can also lie at the TeV scale and provide a plethora of collider phenomena.

hep-ph↗

arXiv2014

Inflation and majoron dark matter in the seesaw mechanism

We propose that inflation and dark matter have a common origin, connected to the neutrino mass generation scheme. As a model we consider spontaneous breaking of global lepton number within the seesaw mechanism. We show that it provides an acceptable inflationary scenario consistent with the recent CMB B-mode observation by the BICEP2 experiment. The scheme may also account for the baryon asymmetry of the Universe through leptogenesis for reasonable parameter choices.

hep-ph↗

arXiv2014

The low-scale approach to neutrino masses

In this short review we revisit the broad landscape of low-scale $SU(3)_c \times SU(2)_L \times U(1)_Y$ models of neutrino mass generation, with view on their phenomenological potential. This includes signatures associated to direct neutrino mass messenger production at the LHC, as well as messenger-induced lepton flavor violation processes. We also briefly comment on the presence of WIMP cold dark matter candidates.

hep-ph↗

arXiv2014

Is charged lepton flavour violation a high energy phenomenon?

Searches for rare processes such as mu --> e gamma put stringent limits on lepton flavour violation expected in many Beyond the Standard Model physics scenarios. This usually precludes the observation of flavour violation at high energy colliders such as the LHC. We here discuss a scenario where right-handed neutrinos are produced via a Z' portal but which can only decay via small flavour violating couplings. Consequently, the process rate is unsuppressed by the small couplings and can be visible despite unobservably small mu --> e gamma rates.

hep-ph↗

arXiv2013

Updated CMB, X- and gamma-ray constraints on majoron dark matter

The majoron provides an attractive dark matter candidate, directly associated to the mechanism responsible for spontaneous neutrino mass generation within the standard model framework. Here we update the cosmological and astrophysical constraints on majoron dark matter which come from the Cosmic Microwave Background (CMB) and a variety of X- and gamma-ray observations.

astro-ph.HE↗

arXiv2010

Three-flavour neutrino oscillation update

We review the present status of three-flavour neutrino oscillations, taking into account the latest available neutrino oscillation data presented at the Neutrino 2008 Conference. This includes the data released this summer by the MINOS collaboration, the data of the neutral current counter phase of the SNO solar neutrino experiment, as well as the latest KamLAND and Borexino data. We give the updated determinations of the leading 'solar' and 'atmospheric' oscillation parameters. We find from global data that the mixing angle $θ_{13}$ is consistent with zero within $0.9σ$ and we derive an upper bound of $\sin^2θ_{13} < 0.035 (0.056)$ at 90% CL (3$σ$).

hep-ph↗

arXiv2008

X-ray photons from late-decaying majoron dark matter

An attractive way to generate neutrino masses as required to account for current neutrino oscillation data involves the spontaneous breaking of lepton number. The resulting majoron may pick up a mass due to gravity. If its mass lies in the kilovolt scale, the majoron can play the role of late-decaying Dark Matter (LDDM), decaying mainly to neutrinos. In general the majoron has also a sub-dominant decay to two photons leading to a mono-energetic emission line which can be used as a test of the LDDM scenario. We compare expected photon emission rates with observations in order to obtain model independent restrictions on the relevant parameters. We also illustrate the resulting sensitivities within an explicit seesaw realisation, where the majoron couples to photons due to the presence of a Higgs triplet.

astro-ph↗

arXiv2008

Can OPERA help in constraining neutrino non-standard interactions?

We study how much the unique ability of the OPERA experiment to directly detect ν_τcan help in probing new, non-standard contact interactions of the third family of neutrinos. We perform a combined analysis of future, high-statistics MINOS and OPERA data. For the case of non-standard interactions in ν_μto ν_e transitions we also include the impact of possible DoubleCHOOZ data. In all cases we find that the ν_τsample of OPERA is too small to be statistically significant, even if one doubles the nominal exposure of OPERA to 4.5E20 pot. OPERA's real benefit for this measurement lies in its very high neutrino energy and hence very different L/E compared to MINOS.

hep-ph↗

arXiv2007

CP Violation and Neutrino Oscillations

We review the basic mechanisms of neutrino mass generation and the corresponding structure of the lepton mixing matrix. We summarize the status of three-neutrino oscillation parameters as determined from current observations, using state-of-the-art solar and atmospheric neutrino fluxes, as well as latest experimental data as of September 2007. We also comment on recent attempts to account for these results and to understand flavour from first principles. We discuss extensively the prospects for probing the strength of CP violation in two near term accelerator neutrino oscillation experiments, T2K and NOvA, as well as possible extensions such as T2KK and a second large off-axis detector near the NOvA detector. We also briefly discuss the possibility of probing the effect of Majorana phases in future neutrinoless double beta decay searches and discuss other implications of leptonic CP violation such as leptogenesis. Finally we comment on the issue of robustness of the current oscillation interpretation and possible ways of probing for non-standard neutrino interactions in precision oscillation studies.

hep-ph↗

arXiv2006

Concluding talk at NOW 2006

This writeup summarizes the status of neutrino oscillations, including recent fluxes and experimental data, as of summer 2006. A discussion is given on the current status of absolute scale of neutrino mass from tritium, neutrinoless double beta decay and cosmological observations, as well as the prospects for the next generation of experiments, including lepton flavor violation searches, and their theoretical significance.

hep-ph↗

arXiv2002

Neutrinos: summarizing the state-of-the-art

I review oscillation solutions to the neutrino anomalies and discuss how to account for the required pattern of neutrino masses and mixings from first principles. Unification and low-energy bottom-up approaches are discussed, the latter open up the possibility of testing neutrino mixing at high energy colliders, such as the LHC. Large \ne mixing is consistent with Supernova (SN) astrophysics and may serve to probe galactic SN parameters at Cherenkov detectors. I discuss the robustness of the atmospheric neutrino oscillation hypothesis against the presence of Flavor Changing (FC) Non-Standard neutrino Interactions (NSI), generally expected in models of neutrino mass. Atmospheric data strongly constrain FC-NSI in the \nm-\nt channel, while solar data can be explained by FC-NSI in the \ne-\nt channel, or, alternatively, by spin flavor precession. I illustrate how a neutrino factory offers a unique way to probe or FC-NSI and argue that a near-site detector is necessary in order to probe for leptonic mixing and CP violation.

hep-ph↗

arXiv2001

Broken R-parity, stop decays, and neutrino physics

We discuss the phenomenology of the lightest stop in models where R-parity is broken by bilinear superpotential terms. In this class of models we consider scenarios where the R-parity breaking two-body decay ~t_1->τ^+b competes with the leading three-body decays such as ~t_1->W^+b~χ^0_1. We demonstrate that the R-parity violating decay can be sizable and in some parts of the parameter space even the dominant one. Moreover we discuss the expectations for t_1->μ^+b and ~t_1->e^+b. The recent results from solar and atmospheric neutrinos suggest that these are as important as the tau bottom mode. The t_1->l^+b decays are of particular interest for hadron colliders, as they may allow a full mass reconstruction of the lighter stop. Moreover these decay modes allow cross checks on the neutrino mixing angle involved in the solar neutrino puzzle complementary to those possible using neutralino decays. For the so--called small mixing angle or SMA solution ~t_1->e^+b should be negligible, while for the large mixing angle type solutions all ~t_1->l^+b decays should have comparable magnitude.

hep-ph↗

arXiv2000

Two-Body Decays of the Lightest Stop in Supergravity with and without R-Parity

We study the decays of the lightest top squark in supergravity models with and without R-parity. Using the simplest model with an effective explicit bilinear breaking of R-parity and radiative electroweak symmetry breaking we show that, below the threshold for decays into charginos $\tilde t_1\to cχ^+_1$, the lightest stop decays mainly into third generation fermions, $\tilde t_1\to bτ$ instead of the R-parity conserving mode $\tilde t_1\to cχ^0_1$, even for tiny tau--neutrino mass values. Moreover we show that, even above the threshold for decays into charginos, the decay $\tilde t_1\to bτ$ may be dominant. We study the role played by the universality of the boundary conditions on the soft supersymmetry breaking terms. This new decay mode $\tilde t_1\to bτ$ as well as the cascades originated by the conventional $\tilde t_1\to cχ^0_1$ decay followed by the R-parity violating neutralino decays can provide new signatures for stop production at LEP and the Tevatron.

hep-ph↗

arXiv1999

Supersymmetry Unification Predictions for M_top V_cb and tan(beta)

We study the predictions for M_top, tan(beta) and V_cb in a popular texture ansatze for the fermion mass matrices. We do this both for the Minimal Supersymmetric Standard Model (MSSM) and for the simplest model (MSSM-BRpV) where a bilinear R-Parity violating term is added to the superpotential. We find that taking the experimental values for M_top and V_cb at 99 % C.L. and the GUT relations h_b=h_tau and (V_cb)^2=h_c/h_t within 5 %, the large tan(beta) solution, characteristic in the MSSM with bottom--tau unification, becomes disallowed. In contrast the corresponding allowed region for the MSSM-BRpV is slightly larger. We also find that important modifications occur if we relax the texture conditions at the GUT scale. For example, if the GUT relations are imposed at 40 %, the large tan(beta) branch in the MSSM becomes fully allowed. In addition, in MSSM-BRpV the whole tan(beta)-M_top plane become allowed, finding unification at any value of tan(beta).

hep-ph↗

arXiv1999

Lepton Flavour Violation in a Left-Right Symmetric Model

We consider in this paper a Left-Right symmetric gauge model in which a global lepton-number-like symmetry is introduced and broken spontaneously at a scale that could be as low as 10^4 GeV or so. The corresponding physical Nambu-Goldstone boson, which we call majoron and denote J, can have tree-level flavour-violating couplings to the charged fermions, leading to sizeable majoron-emitting lepton-flavour-violating weak decays. We consider explicitly a leptonic variant of the model and show that the branching ratios for μ-> e+J, τ-> e + J and τ-> μ+ J decays can be large enough to fall within the sensitivities of future μand τfactories. On the other hand the left-right gauge symmetry breaking scale may be as low as few TeV.

hep-ph↗

arXiv1998

Neutrino Masses, where do we stand?

I review the status of neutrino physics post-Neutrino~98, including the implications of solar and atmospheric neutrino data, which strongly indicate nonzero neutrino masses. LSND and the possible role of neutrinos as hot dark matter (HDM) are also mentioned. The simplest schemes proposed to reconcile these requirements invoke a light sterile neutrino in addition to the three active ones, two of them at the MSW scale and the other two maximally-mixed neutrinos at the HDM/LSND scale. In the simplest theory the latter scale arises at one-loop, while the solar and atmospheric parameters $Δ{m^2}_\odot$ & $Δ{m^2}_{atm}$ appear at the two-loop level. The lightness of the sterile neutrino, the nearly maximal atmospheric neutrino mixing, and the generation of $Δ{m^2}_\odot$ & $Δ{m^2}_{atm}$ follow naturally from the assumed lepton-number symmetry and its breaking. These two basic schemes can be distinguished at future solar & atmospheric neutrino experiments and have different cosmological implications.

hep-ph↗

arXiv1998

Tau Lepton Mixing with Charginos and its Effects on Chargino Searches at e+e- Colliders

In bilinear R-Parity violating models where a term ε_3L_3H_2 is introduced in the superpotential, the tau lepton can mix with charginos. We show that this mixing is fully compatible with LEP1 precision measurements of the Zττand Wτν_τcouplings even for large values of ε_3 and of the induced vacuum expectation value v_3 of the tau-sneutrino. The single production of charginos at e+e- colliders is possible in this case and we present numerical values of the cross-section at LEP1, LEP2 and an NLC. We find maximum values of 10 pb at LEP1 and 1 fb at NLC, while the corresponding values at LEP2 are too small to observe.

hep-ph↗

arXiv1998

Neutrino Electron Scattering and Electroweak Gauge Structure: Future Tests

Low-energy high-resolution neutrino-electron scattering experiments may play an important role in testing the gauge structure of the electroweak interaction. We propose the use of radioactive neutrino sources (e.g. $^{51}$Cr) in underground experiments such as BOREXINO, HELLAZ and LAMA. As an illustration, we display the sensitivity of these detectors in testing the possible existence of extra neutral gauge bosons, both in the framework of E_6 models and of models with left-right symmetry.

hep-ph↗