arXiv subjects

J. W. F. Valle

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

At least 127 records · Page 7Linked to original sources

arXiv2007

Minimal supergravity radiative effects on the tri-bimaximal neutrino mixing pattern

We study the stability of the Harrison-Perkins-Scott (HPS) mixing pattern, assumed to hold at some high energy scale, against supersymmetric radiative corrections. We work in the framework of a reference minimal supergravity model (mSUGRA) where supersymmetry breaking is universal and flavor-blind at unification. The radiative corrections considered include both RGE running as well as threshold effects. We find that in this case the solar mixing angle can only increase with respect to the HPS reference value, while the atmospheric and reactor mixing angles remain essentially stable. Deviations from the solar angle HPS prediction towards lower values would signal novel contributions from physics beyond the simplest mSUGRA model.

hep-ph↗

arXiv2007

Probing the internal solar magnetic field through g-modes

The observation of g-mode candidates by the SoHO mission opens the possibility of probing the internal structure of the solar radiative zone (RZ) and the solar core more directly than possible via the use of the p-mode helioseismology data. We study the effect of rotation and RZ magnetic fields on g-mode frequencies. Using a self-consistent static MHD magnetic field model we show that a 1% g-mode frequency shift with respect to the Solar Seismic Model (SSeM) prediction, currently hinted in the GOLF data, can be obtained for magnetic fields as low as 300 kG, for current measured modes of radial order n=-20. On the other hand, we also argue that a similar shift for the case of the low order g-mode candidate (l=2, n=-3) frequencies can not result from rotation effects nor from central magnetic fields, unless these exceed 8 MG.

astro-ph↗

arXiv2007

Probing non-standard neutrino interactions with supernova neutrinos

We analyze the possibility of probing non-standard neutrino interactions (NSI, for short) through the detection of neutrinos produced in a future galactic supernova (SN).We consider the effect of NSI on the neutrino propagation through the SN envelope within a three-neutrino framework, paying special attention to the inclusion of NSI-induced resonant conversions, which may take place in the most deleptonised inner layers. We study the possibility of detecting NSI effects in a Megaton water Cherenkov detector, either through modulation effects in the $\barν_e$ spectrum due to (i) the passage of shock waves through the SN envelope, (ii) the time dependence of the electron fraction and (iii) the Earth matter effects; or, finally, through the possible detectability of the neutronization $ν_e$ burst. We find that the $\barν_e$ spectrum can exhibit dramatic features due to the internal NSI-induced resonant conversion. This occurs for non-universal NSI strengths of a few %, and for very small flavor-changing NSI above a few$\times 10^{-5}$.

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arXiv2007

Predictive flavour symmetries of the neutrino mass matrix

Here we propose an $A_4$ flavour symmetry model which implies a lower bound on the neutrinoless double beta decay rate, corresponding to an effective mass parameter $M_{ee} \gsim 0.03$ eV, and a direct correlation between the expected magnitude of CP violation in neutrino oscillations and the value of $\sin^2θ_{13}$, as well as a nearly maximal CP phase $δ$.

hep-ph↗

arXiv2006

Neutrinos in astroparticle physics

I briefly discuss the role of neutrinos as probes in astroparticle physics and review the status of neutrino oscillation parameters as of June 2006, including recent fluxes, and latest SNO, K2K and MINOS results. I comment on the origin of neutrino masses in seesaw-type and low-scale models and mention some of their experimental signals.

hep-ph↗

arXiv2006

Neutrino masses and electroweak symmetry breaking

Neutrino mass generation may affect the basic structure of the electroweak symmetry breaking sector. We consider a broad class of elementary particle theories where neutrinos get mass at a low mass scale. We show how these can be made natural up to few TeV or so, in the absence of supersymmetry or other possible stabilizing mechanisms. Although the standard signatures for which LHC has been optimized are absent, others are expected. A generic one among these is the possibility of an invisibly decaying Higgs boson which is characteristic of models with spontaneous breaking of lepton number symmetry below TeV or so.

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arXiv2006

Are solar neutrino oscillations robust?

The robustness of the large mixing angle (LMA) oscillation (OSC) interpretation of the solar neutrino data is considered in a more general framework where non-standard neutrino interactions (NSI) are present. Such interactions may be regarded as a generic feature of models of neutrino mass. The 766.3 ton-yr data sample of the KamLAND collaboration are included in the analysis, paying attention to the background from the reaction ^13C(α,n) ^16O. Similarly, the latest solar neutrino fluxes from the SNO collaboration are included. In addition to the solution which holds in the absence of NSI (LMA-I) there is a 'dark-side' solution (LMA-D) with sin^2 theta_Sol = 0.70, essentially degenerate with the former, and another light-side solution (LMA-0) allowed only at 97% CL. More precise KamLAND reactor measurements will not resolve the ambiguity in the determination of the solar neutrino mixing angle theta_Sol, as they are expected to constrain mainly Delta m^2. We comment on the complementary role of atmospheric, laboratory (e.g. CHARM) and future solar neutrino experiments in lifting the degeneracy between the LMA-I and LMA-D solutions. In particular, we show how the LMA-D solution induced by the simplest NSI between neutrinos and down-type-quarks-only is in conflict with the combination of current atmospheric data and data of the CHARM experiment. We also mention that establishing the issue of robustness of the oscillation picture in the most general case will require further experiments, such as those involving low energy solar neutrinos.

hep-ph↗

arXiv2006

Neutrino physics overview

Seesaw-type and low-scale models of neutrino masses are reviewed, along with the corresponding structure of the lepton mixing matrix. The status of neutrino oscillation parameters as of June 2006 is given, including recent fluxes, as well as latest SNO, K2K and MINOS results. Some prospects for the next generation of experiments are given. This writeup updates the material presented in my lectures at the Corfu Summer Institute on Elementary Particle Physics in September 2005.

hep-ph↗

arXiv2006

Thermal leptogenesis in extended supersymmetric seesaw

We consider an extended supersymmetric SO(10) seesaw model with only doublet Higgs scalars, in which neutrino masses are suppressed by the scale of D-parity violation. Leptogenesis can occur at the TeV scale through the decay of a singlet Sigma, thereby avoiding the gravitino crisis. Washout of the asymmetry can be effectively suppressed by the absence of direct couplings of Sigma to leptons.

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arXiv2006

Radiative zone solar magnetic fields and g-modes

We consider a generalized model of seismic-wave propagation that takes into account the effect of a central magnetic field in the Sun. We determine the g-mode spectrum in the perturbative magnetic field limit using a one-dimensional Magneto-Hydrodynamics (MHD) picture. We show that central magnetic fields of about 600-800 kG can displace the pure g-mode frequencies by about 1%, as hinted by the helioseismic interpretation of GOLF observations.

astro-ph↗

arXiv2006

Constraining non-standard interactions in nu_e e or bar{nu}_e e scattering

We present a new analysis of non-universal and flavor changing non-standard neutrino interactions (NSI) in ν_e e or \barν_e e scattering. Our global analysis of these process includes all relevant experiments, such as the most recent MUNU measurement from reactor neutrinos, both in the context of the Standard Model as well as extensions where NSI are present. We also compare our constraints on non-universal and flavor changing NSI with results from previous analyses. We stress the importance of combining neutrino and anti-neutrino data in the resulting constraints on electroweak paramaters, and the important role that future low energy solar neutrino experiments can play in improving existing sensitivities.

hep-ph↗

arXiv2006

Production and decays of supersymmetric Higgs bosons in spontaneously broken R-parity

We study the mass spectra, production and decay properties of the lightest supersymmetric CP-even and CP-odd Higgs bosons in models with spontaneously broken R-parity (SBRP). We compare the resulting mass spectra with expectations of the Minimal Supersymmetric Standard Model (MSSM), stressing that the model obeys the upper bound on the lightest CP-even Higgs boson mass. We discuss how the presence of the additional scalar singlet states affects the Higgs production cross sections, both for the Bjorken process and the "associated production". The main phenomenological novelty with respect to the MSSM comes from the fact that the spontaneous breaking of lepton number leads to the existence of the majoron, denoted J, which opens new decay channels for supersymmetric Higgs bosons. We find that the invisible decays of CP-even Higgses can be dominant, while those of the CP-odd bosons may also be sizeable.

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arXiv2006

A Theory Perspective on Neutrino Oscillations

I summarize the status of neutrino oscillations that follow from current data, including the status of the small parameters ratio of solar-over-atmospheric splitting and $\sin^2θ_{13}$ characterizing the strength of CP violation in neutrino oscillations. I briefly discuss the impact of oscillation data on the prospects for probing the absolute scale of neutrino mass in neutrinoless double beta decay. I also comment on the theoretical origin of neutrino mass, mentioning recent attemps to explain current data from first principles.

hep-ph↗

arXiv2005

Enhanced mu-e conversion in nuclei in the inverse seesaw model

We investigate nuclear mu-e conversion in the framework of an effective Lagrangian arising from the inverse seesaw model of neutrino masses. We consider lepton flavour violation interactions that arise from short range (non-photonic) as well as long range (photonic) contributions. Upper bounds for the LFV parameters characterizing mu-e conversion are derived in the inverse seesaw model Lagrangian using the available limits on the mu-e conversion branching ratio, as well as the expected sensitivities of upcoming experiments. We comment on the relative importance of these two types of contributions and their relationship with the measured solar neutrino mixing angle theta_12 and the dependence on theta_13. Finally we show how the LFV mu-e conversion and the mu -> e gamma rates are strongly correlated in this model.

hep-ph↗

arXiv2005

R-parity violation assisted thermal leptogenesis in the seesaw mechanism

Successful leptogenesis within the simplest type I supersymmetric seesaw mechanism requires the lightest of the three right-handed neutrino supermultiplets to be heavier than $\sim10^9$ GeV. Thermal production of such (s)neutrinos requires very high reheating temperatures which result in an overproduction of gravitinos with catastrophic consequences for the evolution of the universe. In this letter, we let R-parity be violated through a $λ_i \hat{N}_i \hat{H}_u \hat{H}_d$ term in the superpotential, where $\hat{N}_i$ are right-handed neutrino supermultiplets. We show that in the presence of this term, the produced lepton-antilepton asymmetry can be enhanced. As a result, even for $\hat{N}_1$ masses as low as $10^6$ GeV or less, we can obtain the observed baryon asymmetry of the universe without gravitino overproduction.

hep-ph↗

arXiv2005

Neutrino masses and oscillations

I summarize the status of three--neutrino oscillations that follow from combining the relevant world's data. The discussion includes the small parameters Delta_m-sol/Delta_m-atm and \sin^2θ_{13}, which characterize the strength of CP violation in neutrino oscillations, the impact of oscillation data on the prospects for probing the absolute scale of neutrino mass in \nbb and the robustness of the neutrino oscillation interpretation itself in the presence of non-standard physics. I also comment on the theoretical origin of neutrino mass, mentioning recent attemps to explain current oscillation data.

hep-ph↗

arXiv2005

Neutrino oscillations and new physics

I discuss the theoretical background and the status of neutrino oscillation parameters from the current worlds' global data sample and latest flux calculations. I give their allowed ranges, best fit values and discuss the small parameters and sin2theta13, which characterize CP violation in neutrino oscillations. I mention the significance of neutrinoless double beta decay and current expectations in view of oscillation results.

hep-ph↗

arXiv2005

Novel Supersymmetric SO(10) Seesaw Mechanism

We propose a new seesaw mechanism for neutrino masses within a class of supersymmetric SO(10) models with broken D-parity. It is shown that in such scenarios the B-L scale can be as low as TeV without generating inconsistencies with gauge coupling unification nor with the required magnitude of the light neutrino masses. This leads to a possibly light new neutral gauge boson as well as relatively light quasi-Dirac heavy leptons. These particles could be at the TeV scale and mediate lepton flavour and CP violating processes at appreciable levels.

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