2,689 research outputs found
Pairing effect on the giant dipole resonance width at low temperature
The width of the giant dipole resonance (GDR) at finite temperature T in
Sn-120 is calculated within the Phonon Damping Model including the neutron
thermal pairing gap determined from the modified BCS theory. It is shown that
the effect of thermal pairing causes a smaller GDR width at T below 2 MeV as
compared to the one obtained neglecting pairing. This improves significantly
the agreement between theory and experiment including the most recent data
point at T = 1 MeV.Comment: 8 pages, 5 figures to be published in Physical Review
The decay in an EW-scale non-sterile RH neutrino model
We study in this research the phenomenology of decay in a
scenario of the class of extended models with non-sterile right-handed (RH)
neutrino at electroweak (EW) scale proposed by P.Q. Hung. Field content of the
standard model (SM) is enlarged by introducing for each SM fermion a
corresponding mirror partner with the same quantum numbers beside opposite
chirality. Light neutrino masses are generated via the type-I see-saw mechanism
and it is also proved to be relevant with low energy within the EW scale of the
RH neutrino masses. We introduce the model and derive branching ratio of the
decay at one-loop approximation with the participation of W
gauge boson, neutral and singly charged Higgs scalars. After that we set
constraints on relevant parameters and predict the sensitivities of the decay
channel under the present and future experiments.Comment: 19 pages, 8 figure
Muon anomalous magnetic dipole moment in a low scale type I see-saw model
Recent experimental results on muon anomalous magnetic dipole moment have
shown a tension with the SM prediction, which has blown a fresh
wind into the elementary particle physics community. The problem is believed to
be explained only by physics beyond the standard model. Current work considers
the anomalous moment in a scenario of models with mirror symmetry and type I
see-saw mechanism at low energy scale of electroweak interactions. After a
brief introduction to the model, a detailed numerical analysis of muon
anomalous phenomenology will be carefully performed.Comment: 15 pages, 2 tables, 5 figue
Revisiting Minimal Lepton Flavour Violation in the Light of Leptonic CP Violation
The Minimal Lepton Flavour Violation (MLFV) framework is discussed after the
recent indication for CP violation in the leptonic sector. Among the three
distinct versions of MLFV, the one with degenerate right-handed neutrinos will
be disfavoured, if this indication is confirmed. The predictions for leptonic
radiative rare decays and muon conversion in nuclei are analysed, identifying
strategies to disentangle the different MLFV scenarios. The claim that the
present anomalies in the semi-leptonic -meson decays can be explained within
the MLFV context is critically re-examined concluding that such an explanation
is not compatible with the present bounds from purely leptonic processes.Comment: 36 pages, 4 figures. V2: References added; version accepted for
publication on JHE
Damping of giant dipole resonance in hot rotating nuclei
The phonon damping model (PDM) is extended to include the effect of angular
momentum at finite temperature. The model is applied to the study of damping of
giant dipole resonance (GDR) in hot and noncollectively rotating spherical
nuclei. The numerical results obtained for Mo88 and Sn106 show that the GDR
width increases with both temperature T and angular momentum M. At T > 4 MeV
and M<= 60 hbar the increase in the GDR width slows down for Sn106, whereas at
M<= 80 hbar the GDR widths in both nuclei nearly saturate. By adopting the
nuclear shear viscosity extracted from fission data at T= 0, it is shown that
the maximal value of the angular momentum for Mo88 and Sn106 should be around
46 and 55 hbar, respectively, so that the universal conjecture for the lower
bound of the specific shear viscosity for all fluids is not violated up to T= 5
MeV.Comment: 19 pages, 6 figures, accepted in Phys. Rev.
Radiative Emission of Neutrino Pairs in Atoms and Light Sterile Neutrinos
The process of Radiative Emission of Neutrino Pair (RENP) in atoms is
sensitive to the absolute neutrino mass scale, the type of spectrum neutrino
masses obey and the nature - Dirac or Majorana - of massive neutrinos. We
analyse the possibility to test the hypothesis of existence of neutrinos with
masses at the eV scale coupled to the electron in the weak charged lepton
current in an RENP experiment. The presence of eV scale neutrinos in the
neutrino mixing is associated with the existence of sterile neutrinos which mix
with the active flavour neutrinos. At present there are a number of hints for
active-sterile neutrino oscillations driven by .
We perform a detailed analysis of the RENP phenomenology within the "3 + 1"
scheme with one sterile neutrino.Comment: LATEX file, 19 pages, the effects of the 3-4 mixing taken into
account, one table and four figures added, version to be published in Phys.
Lett.
Specific shear viscosity in hot rotating systems of paired fermions
The specific shear viscosity of a classically rotating system of
nucleons that interact via a monopole pairing interaction is calculated
including the effects of thermal fluctuations and coupling to pair vibrations
within the selfconsistent quasiparticle random-phase approximation. It is found
that increases with angular momentum at a given temperature .
In medium and heavy systems, decreases with increasing at
2 MeV and this feature is not affected much by angular momentum. But in
lighter systems (with the mass number 20), increases with
at a value of close to the maximal value , which is defined as
the limiting angular momentum for each system. The values of
obtained within the schematic model as well as for systems with realistic
single-particle energies are always larger than the universal lower-bound
conjecture up to =5 MeV.Comment: 19 pages, 7 figures, accepted for publication in Phys. Rev.
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