119340113
Medium effects in the pion pole mechanism (photon photon -->pion-zero -->neutrino-R antineutrino-L (neutrino-L antineutrino-R)) of neutron star cooling
Nuclear medium effects in the neutrino cooling of neutron stars through the exotic reaction channel \gamma \gamma -->\pi^0-->\nu_R \bar{\nu_L} (\nu_L \bar{\nu_R}) are incorporated. Throughout the paper we discuss different possibilities of right-handed neutrinos, massive left-handed neutrinos and standard massless left-handed neutrinos (reaction is then allowed only with medium modified vertices). It is demonstrated that multi-particle effects suppress the rate of this reaction channel by 6-7 orders of magnitude that does not allow to decrease existing experimental upper limit on the corresponding \pi^0\nu\bar{\nu} coupling. Other possibilities of the manifestation of the given reaction channel in differente physical situations, e.g. in the quark color superconducting cores of some neutron stars, are also discussed. We demonstrate that in the color-flavor-locked superconducting phase for temperatures T<(0.1-10) MeV (depending on the effective pion mass and the decay width) the process is feasibly the most efficient neutrino cooling process, although the absolute value of the reaction is rather small.
3210437
Glueballs in peripheral heavy-ion collisions
Abstract We estimate the cross-section for glueball production in peripheral heavy-ion collisions through two-photon and double-Pomeron exchange, at energies that will be available at RHIC and LHC. Glueballs will be produced at large rates, opening the possibility to study decays with very small branching ratios. In particular, we discuss the possibility of observing the subprocess γγ ( PP ) → G → γγ .
35333132
Photon-photon and pomeron-pomeron processes in peripheral heavy ion collisions
Instituto de Fisica Teorica Universidade Estadual Paulista, Rua Pamplona, 145, 01405-900, Sao Paulo, SP
120803068
A limit on the fermion masses in a technicolor scenario
Recently it has been pointed out that no limits can be put on the scale of fermion mass generation (M) in technicolor models, because the relation between the fermion masses (mf) and M depends on the dimensionality of the interaction responsible for generating the fermion mass. Depending on this dimensionality it may happens that mf does not depend on M at all. We show that exactly in this case mf may reach its largest value, which is almost saturated by the top quark mass. We make few comments on the question of how large can be a dynamically generated fermion mass.
125867298
Limit on Gamma (pi0 ---> neutrino anti-neutrino) from SN1987A
121884739
The strength of trilinear higgs boson coupling in composite models
In this work we discuss the strength of the trilinear Higgs boson coupling in composite models in a model independent way. The coupling is determined as a function of a very general ansatz for the fermionic self-energy, and turns out to be equal or smaller than the one of the Standard Model Higgs boson depending on the dynamics of the theory.
55809021
Heptagonic symmetry for quarks and leptons
The non-Abelian discrete symmetry D(7) of the heptagon is successfully applied to both quark and lepton mass matrices, including CP violation.