Seminars of 2005

Past Seminars


Supersymmetry breaking as the origin of flavor


Dr. Javier Ferrandis

Lawrence Berkeley National Laboratory

Seminari del IFIC

Wednesday, January 12th, 2005 at 12:00

Abstract

We present an effective flavor model for the radiative generation of fermion masses and mixings based on a SU(5)XU(2) symmetry. We argue that the original source of flavor breaking resides in the supersymmetry breaking sector. Flavor violation would be transmitted radiatively to the fermion Yukawa couplings at low energy through finite supersymmetric threshold corrections. If this is the case one could fit the fermion mass ratios and CKM matrix elements, suppress the dimension five operators which contribute to proton decay, solve the SUSY CP-problem and overcome the present constraints on supersymmetric contributions to flavor changing processes through an approximate radiative alignment between the Yukawa and the soft supersymmetry breaking sector. We will argue that this possibility is supported by recently discovered patterns between dimensionless fermion mass ratios and CKM elements. We present an effective flavor model for the radiative generation of fermion masses and mixings based on a SU(5)xU(2) symmetry. We assume that the original source of flavor breaking resides in the supersymmetry breaking sector. Flavor violation is transmitted radiatively to the fermion Yukawa couplings at low energy through finite supersymmetric threshold corrections. This model can fit the fermion mass ratios and CKM matrix elements, explain the non-observation of proton decay, solve CP-problems and overcome present constraints on susy contributions to flavor changing processes through an approximate radiative alignment between the Yukawa and the soft trilinear sector. The model predicts new relations between dimensionless fermion mass ratios in the three fermion sectors, and the quark mixing angles.

Displaced vertices at the Tevatron from neutralino decays


Dr. Diego Restrepo

IFIC - Universidad de Antioquia

Seminari del IFIC

Tuesday, January 18th, 2005 at 12:00

Abstract

Supersymmetric extensions of the standard model exhibiting bilinear $R$--parity violation can generate naturally the observed neutrino mass spectrum as well as mixings. One interesting feature of these scenarios is that the lightest supersymmetric particle (LSP) is unstable, with decay properties predicted in terms of neutrino parameters. A smoking gun of this model in colliders is the presence of displaced vertices due to LSP decays. In this work we focus on the simplest model of this type that comes from minimal supergravity with universal R--parity conserving soft breaking of supersymmetry (RmSUGRA). We evaluate the potentiality of the Fermilab Tevatron to probe the RmSUGRA parameters through the analysis of events possessing two displaced vertices stemming from LSP decays. We show that requiring two displaced vertices in the events leads to a reach in $m_{1/2}$ twice the one in the usual multilepton signals in a large fraction of the parameter space.

The sensitivity of cosmic ray air shower experiments for excited lepton detection


Prof. Jorge C. Romão

Instituto Superior Tecnico, Lisboa

Sala Seminarios IFIC

Tuesday, February 15th, 2005 at 16:00

Abstract

In models with substructure in the fermionic sector, excited fermionstates are expected. Excited leptons could be produced in theinteraction of high energy quasi-horizontal cosmic neutrinos with theatmosphere via neutral and charged current processes, \nu N -> \nu^* X and \nu N -> \ell^* X. The hadronic component X, and possibly part of the excited lepton decay products,would originate an extensive air shower, observable in large cosmic ray experiments. In this paper, the sensitivity of present and plannedvery high energy cosmic ray experiments to excited lepton production is estimated and discussed.

Lepton masses and mixing in minimal renormalizable SUSY SO(10) and beyond


Dr. Michal Malinsky

SISSA Trieste

Sala de Juntas del IFIC planta baja

Friday, February 11th, 2005 at 12:30

Abstract

The status of the fit of fermion masses and mixings within the minimal renormalizable SUSY SO(10) for dominant triplet seesaw for neutrinos is reviewed and the possible effects of an additional antisymmetric representation are briefly discussed.

The flhiggs model


Dr. Federica Bazzocchi

SISSA Trieste

Sala de Juntas del IFIC planta baja

Tuesday, February 8th, 2005 at 16:00

Abstract

We present a unified picture of flavor and electroweak symmetry breaking based on a nonlinear sigma model spontaneously broken at the TeV scale. Flavor and Higgs bosons arise as pseudo-Goldstone modes. Explicit collective symmetry breaking yields stable vacuum expectation values and masses protected at one loop by the little-Higgs mechanism. The coupling to the fermions generates well-definite mass textures--according to a U(1) global flavor symmetry--that correctly reproduce the mass hierarchies and mixings of quarks and leptons. The model is more constrained than usual little-Higgs models because of bounds on weak and flavor physics. The main experimental signatures testable at the LHC are a rather large mass around 300 GeV for the (lightest) Higgs boson and a characteristic spectrum of new bosons and fermions at the TeV scale.

Superstring phenomenology


Prof. Graham Ross

Univ. of Oxford

Sala Seminarios IFIC (Edf. Institutos Paterna)

Friday, February 4th, 2005 at 11:00

Abstract

The prospect for observational tests of superstring unification of the fundamental forces is explored. The unification of the gauge couplings provides quantitative support for an underlying unification and its success limits the possible new physics at high scales. In string theory the unification extends to the gravitational interaction and leads to a further quantitative prediction for the unification scale which is related to the Planck scale. After including heavy threshold corrections the weakly coupled heterotic string prediction is in excellent agreement with experiment. We discuss the general profile of the underlying string theory which maintains this success and identify general features of the effective low energy theory that can be experimentally tested.

Precision measurement of large mixing angles theta_12 and theta_23


Prof. Hisakazu Minakata

Tokyo Metropolitan Univ.

Sala Seminarios IFIC (Edf. Institutos Paterna)

Wednesday, March 9th, 2005 at 12:00

Abstract

After oscillatory behavior has been seen by three experiments (SK, K2K, KamLAND) the neutrino oscillation studies entered into the era of precision measurement. I address some of the features of determination of theta_12 and theta_23; What is the principle of determining them accurately, how it can be performed, what would be the achievable ultimate accuracies, etc.

How Can the Neutrino Seesaw Mechanism Be Tested?


Ernest Ma

University of California, Riverside

Sala Seminarios IFIC (Edf. Institutos Paterna)

Monday, May 16th, 2005 at 16:00

Abstract

The famous canonical seesaw mechanism for naturally small Majorana neutrino masses is discussed in a broader context. A specific test of its validity is proposed.

Discrete and Unified ideas for fermion mixing


Dr. Michele Frigerio

U California Riverside

Sala Seminarios IFIC (Edf. Institutos Paterna)

Monday, March 14th, 2005 at 15:00

Abstract

In recent years, our knowledge of the flavor structure in the leptonsector greatly improved thanks to neutrino oscillation experiments.The pattern of fermion masses and mixing angles gives importantindications about what is the physics beyond the Standard Model.We investigate two complementary approaches to this Flavor Problem.First, we consider discrete groups as family symmetries, in particular as a tool to generate a maximal 2-3 mixing or a zero 1-3 mixing.Recently proposed models are discussed, based on the permutation group $S_3$, the quaternion group $Q_8$, or the rectangle group $Z_2 \times Z_2$, with definite predictions for quark and lepton masses and mixing. The phenomenology of the associated electroweak Higgs sector is presented.Second, we consider some recent analyses of the Flavor Sector in SUSY SO(10) Grand Unification Theories. The merits and limits of the "minimal SUSY GUT" model are discussed: maximal mixing is related with $b-\tau$ unification, but the global fit of all masses and mixing is problematic. We suggest a minimal extensionof the GUT Higgs sector which improves the fit in a predictive way.

New Physics Beyond the Standard Model: the Astroparticle Frontier


Prof. Antonio Masiero

Univ. Padova & INFN

Sala Seminarios IFIC (Edf. Institutos Paterna)

Friday, March 11th, 2005 at 11:00

Abstract

The major breakthrough we have witnessed in physics at thetransition between XX and XXI century is a new picture of the entireUniverse emerging from an impressive amount of data from observationalcosmology: a flat Universe which is expanding at an accelerated rate anddominated by a large amount of a mysterious "Dark Energy" together with asubdominant component of "Dark Matter" ( and, surprisingly enough, only aminor part of such dark matter is made of the same baryons we are made of, whilst most of it should be provided by some exotic new particles we havenever seen, not even in our high energy accelerators). These new data arefascinating and challenging not only for cosmologists, but also forparticle physicists: indeed, there we find some of the very few "smokingguns" for the presence of new physics beyond the Standard Model ofparticle physics. This will be the main focus of this colloquium: how"physics from the Sky" can drive us to the new particle physics, part ofwhich we should be able to see at machines like LHC.

CP-violating effects in supersymmetric models


Dr. Karl Hohenwarter-Sodek

Univ. of Vienna

Sala de Juntas IFIC planta baja

Thursday, February 24th, 2005 at 16:00

Abstract

I will talk about CP-violating effects in supersymmetricprocesses. Our framework is the MSSM with complex parameters.In order to identify unambiguously an effect of CP violation,the measurement of certain CP sensitive observables will benecessary. I will discuss CP sensitive observables in neutralino andchargino production at a linear collider with arbitrarybeam polarization. Further I will talk about various CP sensitiveobservales which can be studied in the decay of a scalar top.

Are light scalar mesons the first exotic hadrons?


Joseph Schechter

Syracuse University

Sala Seminarios IFIC (Edf. Institutos Paterna)

Friday, June 24th, 2005 at 12:00

Abstract

I will discuss the possibility that light scalar mesons
may actually be the first exotic hadrons

How not to solve the coincidence problem


Urbano França

SISSA/ISAS

Sala de Juntas IFIC planta baja

Thursday, June 9th, 2005 at 12:00

Abstract

A set of cosmological observations indicate that currentlythe ratio between dark energy (the homogenous component withnegative pressure responsible for the present acceleration ofthe universe) and dark matter densities is approximately 2.Since that ratio varies with time, the so-calledcoincidence problem arises: Why are weliving exactly in the moment it is of order of unity? In this seminarsome tentatives to answer that question will reviewed, especiallyfocusing on the interacting dark energy models (also known asVAMPS - VAriable Mass Particles - models) and why, despiteof not solving the problem, they could give some hints towardsa solution.

Dark Energy with the Atacama Cosmology Telescope


Raul Jimenez

University of Pennsylvania

Seminari del IFIC

Tuesday, May 24th, 2005 at 12:00

Abstract

I will describe an ongoing Cosmic Microwave Background experiment (ACT) designed to measure CMB anisotropies on a scale of 1 arcminute and discover clusters of galaxies through the Sunyaev-Zeldovich effect. I will discuss how to unveil the nature of dark energy, in particular how the shape of the potential of the scalar field that is driving expansion today can be reconstructed using ACT observations.

Supernova neutrino signal and neutrino masses: A powerful statistical approach


Enrico Nardi

Laboratori Nazionali di Frascati -Italy and Univer

Sala Seminarios IFIC

Tuesday, May 10th, 2005 at 12:00

Abstract

Extracting informations on the neutrino mass values from a Supernova neutrino signal, without any reference to additional astrophysical events as time benchmarks for measuring possible neutrino time of flight delays, is a challeging statistical problem and requires powerful as well as robust methods. We describe a strategy that, with the present neutrino detectors, could allow to reach a sensitivity of the order of 1 eV. Therefore,a Galactic Supernova explosion occuring the next few years could still provide interesting informations on the neutrino masses; however we argue that future megatonne neutrino detectors will not be competitive with the next generation of triitum beta decay experiments.

CP Violation in SUSY


Prof. Walter Majerotto

Inst for High Energy Phys of the Austrian Acad Sci

Sala Seminarios IFIC (Edf. Institutos Paterna)

Tuesday, April 19th, 2005 at 11:00

Abstract

Supersymmetric models contain new sources of CP violation if the parameters are complex. These new phases lead to important effects in production and decay processes of SUSY particles. They also might strongly affect the Higgs sector. We discuss some of these effects. In particular, we concentrate on CP violating observables: triple product and decay rate asymmetries. The triple product asymmetries usually involve spin correlations between production and decay and already appear at tree level. We discuss these in chargino and neutralino production and decay. The decay asymmetries are due to loop effects. We calculate such asymmetries for H± and chargino decays.

Weighing neutrinos with cosmological observables


Sergio Pastor

IFIC

Sala Seminarios IFIC

Friday, June 17th, 2005 at 12:00

Abstract

Cosmology can provide information on the absolute scale of neutrino masses that is not fixed by data on flavour neutrino oscillations, complementary to the results of tritium beta decay and neutrinoless double beta decay experiments. After a short introduction on the predicted cosmic neutrino background in the Universe, I will review the present cosmological bounds on neutrino masses and describe the sensitivities of future observations.

Cross-correlating UHE cosmic rays and large scale structures


Alessandro Cuoco

Univ. Naples & IFIC

Sala de Juntas IFIC planta baja

Thursday, July 7th, 2005 at 12:00

Abstract

Intergalactic magnetic fields are believed weak enough to permit an almost rectilinear propagation of UHECRs above an energy of about 5x10^19 eV opening the possibility of making astronomy of very high energies. We discuss the distribution of local astronomical sources (in the GZK sphere of about 100 Mpc) as seen by all sky surveys like 2MASS and IRAS PSCz and forecast the sensitivity of the AUGER experiment to correlate UHECRs with the anisotropies expected by these sources.

Dark Matter Search in the form of WIMPs with the WARP Experiment


Enrico Borriello

Univ. Naples

Sala de Juntas IFIC planta baja

Wednesday, July 6th, 2005 at 12:00

Abstract

The WARP Programmme (WIMP ARgon Programme) is a graded programme intended to search for cold dark metter in the form of WIMPs (Weakly Interacting Massive Particles). WARP is based on a direct detection technique. It consists of observing secondary effects induced by the rare phenomenon of interaction of a WIMP with a nucleus of ordinary matter. A small prototype of the WARP detector already reach a sensitivity level wich is comparable with the present value of other similar experiments. It is evident that in order to explore exhaustively the whole range of the theoretical predictions (SUSY models for example) the detector must be very large. A 100 litres detector is proposed, in order to get an improvement of two magnitude orders in sensitivity. This sensitivity will make WARP capable to test the SUSY models at a level compatible with future accelerators, such as CERN's LHC collider.

Efectos de las oscilaciones de sabor sobre el desacoplamiento de neutrinos cósmicos


Teguayco Pinto Cejas

IFIC

Sala Seminarios IFIC

Friday, September 9th, 2005 at 12:00

Abstract

Lectura del trabajo de investigación

Directores: Sergio Pastor y J.W.F. Valle

Neutrino masses, LSP decay and dark matter


Martin Hirsch

IFIC

Sala Seminarios IFIC

Thursday, September 29th, 2005 at 12:00

Abstract

In the past few years experimental neutrino physics has enjoyed rapid progress. Experiments like Super-K, SNO and KamLAND have established non-zero neutrino masses (and mixing) beyond any reasonable doubt. The status of the theoretical modeling of neutrino masses, on the other hand, is far less satisfactory: Neither do we know the mechanism nor the energy scale at which neutrino masses are produced. In this talk I will focus on the idea that neutrino masses are generated around the electro­weak scale, with special emphasis on R-parity violating supersymmetric models. Compared to the classical seesaw mechanism, this kind of scenario has the advantage of being testable in the near future at the LHC and a possible International Linear Collider. Finally, I will briefly discuss the problem of dark matter in R-parity violating SUSY and one possible idea how to solve it.

Collective neutrino-plasma interaction and magnetic helicity generation in hot plasma of early Universe


Victor Semikoz

IZMIRAN

Sala Seminarios IFIC (Edf. Institutos Paterna)

Friday, November 25th, 2005 at 12:00

Abstract

We argue that the magnetic helicity conservation is violated at the lepton stage in the evolution of early universe due to the parity violation in SM of electroweak interactions. As a result a cosmological magnetic field which can be a seed for the galactic dynamo obtains from the beginning a substantial magnetic helicity which has to be taken into account in the magnetic helicity balance at the later stage of galactic dynamo. The particle physics mechanism suggested in our works depends neither on helicity of matter turbulence with plasma vortices resulting in the standard $\alpha$ - effect in dynamo theory nor on general rotation. The mechanism can result in a self-exitation of an (almost) uniform cosmological magnetic field.

Desintegraciones doble beta


Martin Hirsch

IFIC

Sala de Juntas IFIC Planta Baja

Monday, October 17th, 2005 at 12:00

Abstract

Revisión sobre todos los aspectos de las desintegraciones doble beta (en castellano). Parte 2 el 20 de Octubre

Minimally finetuned SUSY SO(10) with low-scale B-L breaking


Michal Malinsky

School of Physics and Astronomy, Southampton U.

Sala de Juntas del IFIC

Monday, November 28th, 2005 at 16:00

Abstract

A potentially realistic SUSY SO(10) model of neutrino masses with low-scale B-L breaking is reviewed in detail and its further prospects are briefly discussed.

SUSY phenomenology at the LHC


Sabine Kraml

CERN

Sala Seminarios IFIC (Edf. Institutos Paterna)

Thursday, October 27th, 2005 at 12:00

Abstract

If supersymmetry (SUSY) exists at or around the TeV scale, a wealth of new particles will be produced at the LHC. The phenomenology of these particles will depend on the breaking of SUSY at some high-energy scale.
In this talk, I will briefly review the most importent scenarii and the signatures they lead to. Then I will discuss possible LHC measurements of SUSY particles, as well as strategies to derive information on the high-scale boundary conditions of the SUSY breaking.

Probing new physics with coherent neutrino scattering off nuclei


Timur Rashba

Max-Planck-Institut für Physik

Sala de Juntas IFIC

Monday, November 7th, 2005 at 12:00

Abstract

The possibility of measuring for the first time neutrino-nuclei coherent scattering has been recently discussed by several experimental collaborations. It is shown that such a measurement may be very sensitive to non-standard interactions of neutrinos with quarks and might set better constraints than those coming from future neutrino factory experiments. We also comment on other types of new physics tests, such as extra heavy neutral gauge bosons, where the sensitivity to some models is slightly better than the Tevatron constraint and, therefore, could give complementary bounds. The talk is based on the preprint hep-ph/0508299.

Leptogenesis and partial lepton asymmetries


Prof. Luis Bento

Centro de Fisica Nuclear da Universidade de Lisboa

Sala Seminarios IFIC

Friday, December 2nd, 2005 at 12:00

Abstract

Leptogenesis is a mechanism that relates the generation of baryon asymmetry with the spectrum of light neutrino masses. An upper bound on the light neutrino mass scale has been derived from the observed baryon asymmetry in the framework of the original Fukugita and Yanagida proposal, based on the decays of the lightest heavy Majorana neutrino. We review the dynamics of leptogenesis in the simplified form that has been most studied and extend the system to include the generation and evolution of partial lepton asymmetries. The relation bewtween baryon asymmetry and light neutrino masses is explored in this context.

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