Invisible Higgs Boson Decays in Spontaneously Broken R-Parity


Prof. Jorge Romão

Instituto Superior Tecnico, Lisboa


Seminari del IFIC

Wednesday, September 8th, 2004 at 15:00


Abstract

The Higgs boson may decay mainly to an invisible mode characterized by missing energy, instead of the Standard Model channels. This is a generic feature of many models where neutrino masses arise from the spontaneous breaking of ungauged lepton number at relatively low scales, such as spontaneously broken R-parity models. Taking these models as framework, we reanalyze this striking suggestion in view
of the recent data on neutrino oscillations that indicate non-zero neutrino masses. We show that, despite the smallness of neutrino masses, the Higgs boson can decay mainly to the invisible Goldstone boson associated to the spontaneous breaking of lepton number.
The search for invisibly decaying Higgs bosons should be taken into account in the planning of future accelerators,
such as the Large Hadron Collider and the Next Linear Collider.

Probing neutrino mass with multilepton production at the Tevatron in the simplest R-parity violation model


Prof. Mauricio B. Magro

Universidade de Sao Paulo


Aula Seminarios IFIC Planta Baja

Monday, January 12th, 2004 at 16:00


Abstract

We analyze the production of multileptons in the simplest supergravity model with bilinear violation of R parity at the Fermilab Tevatron. Despite the small R-parity violating couplings needed to generate the neutrino masses indicated by current atmospheric neutrino data, the lightest supersymmetric particle is unstable and can decay inside the detector. This leads to a phenomenology quite distinct from that of the R-parity conserving scenario. We quantify by how much the supersymmetric multilepton signals differ from the R-parity conserving expectations, displaying our results in the m0 m1/2 plane. We show that the presence of bilinear R-parity violating interactions enhances the supersymmetric multilepton signals over most of the parameter space, specially at moderate and large m0.

Modelo con tripletes de Higgs y violación bilineal de paridad-Rque relaciona las propiedades de neutrinos con los experimentos de aceleradores


Mr. Albert Villanova del Moral

IFIC


Sala Seminarios IFIC

Friday, January 30th, 2004 at 12:00


Abstract

Lectura del trabajo de investigación
Directores: Martin Hirsch y J.W.F. Valle

Neutrino oscillations driven by dark energy


Dr. Heinrich Paes

Univ of Wuerzburg


Sala Seminarios IFIC

Tuesday, February 17th, 2004 at 12:00


Abstract

We consider neutrinos with varying masses which arise in scenarios
relating neutrino masses to the dark energy density in the universe. We
point out that the neutrino mass variation can lead to level crossing and
thus a cosmo MSW effect, having dramatic consequences for the flavor ratio
of astrophysical neutrinos and the composition of the relic neutrino
background.

Determining the yet unknown neutrino parameters from future oscillation experimen
ts


Dr. Hiroshi Nunokawa

Pontificia Universidade Catolica do Rio de Janeiro


Seminari del IFIC

Friday, February 20th, 2004 at 12:00


Abstract

Assuming 3 neutrinos with CPT invariance (ignoring LSND), we already have significant amount of information on neutrino mass spectrum and mixing angles. The remaining important quantities which are not yet unknown but can be probed by future oscillation experiments are 1) value of $\theta_{13}$ (how small?), 2) sign of $\Delta m^2_{13}$, and 3) CP violating phase, $\delta$. In principle, all of them can be determined by the future long-baseline oscillation experiments. However, it is known that determination
of these quantities suffer from the problem of so called parameter degeneracy which could lead up to 8 solutions which give exactly the same probabilities for neutrino
and anti-neutrino for a given energy and baseline. I will give an overview of this problem and discuss some possible way way to lift the degeneracy. I will address that the reactor oscillation experiment which aim to measure $\theta_{13}$ can help in lifting this degeneracy.

Phenomenological Aspects of Supernova Neutrinos


Dr. Ricard Tomàs

Max-Planck-Institut fuer Physik, Munich


Seminari IFIC

Friday, February 27th, 2004 at 11:30


Abstract

Core-collapse Supernovae (SNe) are one of the most energetic explosive events known.
These occur at the end of a massive ($M \gtrsim 8 M_\odot$) star’s lifetime, and implies an energy release of the order of $O(10^{53})~erg$.
From a particle physics point of view neutrinos turn out to be essential in such events. First they are thought to play
a key role during the explosion phase and in the posterior cooling and
deleptonization of the star. On the other hand they are
responsible to carry away around $99\%$ of the total energy emitted.
Therefore these neutrinos could be easily detected in the case of a
nearby supernova in
the existent or planned neutrino detectors, what could provide a lot
of information about both neutrino properties and the supernova itself.
In this talk we will give an overview on the phenomenology involving
these neutrinos.
We will review the main features of the neutrino spectra and their
propagation through the SN envelope, as well as the current
uncertainties related.
Then we will describe the expected signal
in the case of a future galactic SN, and its implications in the
determination of neutrino properties, like the
mixing parameters and the mass hierarchy.

Update on neutrino oscillations


Dr. Maltoni Michele

SUNY Stony Brook


Sala de Juntas IFIC

Tuesday, May 4th, 2004 at 17:00


Abstract

I update the status of neutrino oscillation physics
including new solar and atmospheric fluxes

CP sensitive observables in chargino productionwith transverse $e^{\pm}$ beam polarization


Dr. Thomas Kernreiter

U. Vienna


Seminari IFIC

Wednesday, May 5th, 2004 at 16:00


Abstract

We consider the process $e^+e^- -> \chi^+_i \chi^-_j$
at a linear collider with transverse beam polarization.
We investigate the influence of the CP phases on azimuthal asymmetries in this process with subsequent chargino two-body decays.
We show that triple product correlations involving the transverse beam polarization vanish if at least one subsequent chargino
decay is not observed. We derive this result within the Minimal Supersymmetric
Standard Model (MSSM) with complex parameters, however, it holds also in the general
MSSM with SUSY flavour violation.

Recent developments in thermal leptogenesis


Dr. Pasquale Di Bari

IFAE-UAB, Barcelona


Sala Seminarios IFIC

Friday, June 25th, 2004 at 15:00


Abstract

Recent developments in thermal leptogenesis are reviewed. Neutrino mixing data support a simple picture where the asymmetry is generated by the decays of the heavy Majorana neutrinos mildly close to thermal equilibrium and, remarkably, in the full non relativistic regime. Neutrino masses larger than 0.1 eV are not compatible with the minimal scenario. We also discuss how this result is stable turning to the supersymmetric scenario or under addition of decoupled species or considering degenerate heavy neutrino mass spectrum.

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