1,411 research outputs found
Limits on the neutron-antineutron oscillation time from the stability of nuclei
We refute a recent claim by Nazaruk that the limits placed on the free--space
neutron--antineutron oscillation time can be improved by
many orders of magnitude with respect to the estimate , where is a measured limit on the annihilation
lifetime of a nucleus and MeV is a typical antineutron-nucleus
annihilation width.Comment: 4 pages, Latex, submitted to Physics Letters
The Pion in Electromagnetic and Weak Neutral Current Nuclear Response Functions
The impact of pionic correlations and meson--exchange currents in determining
the (vector) response functions for electroweak quasielastic lepton scattering
from nuclei is discussed. The approach taken builds on previous work where the
Fermi gas model is used to maintain consistency in treating forces and currents
(gauge invariance) and to provide a Lorentz covariant framework. Results
obtained in first-order perturbation theory are compared with infinite-order
summation schemes (HF and RPA) and found to provide quite successful
approximations for the quasielastic response functions. The role of pionic
correlations in hardening the responses R_L and R_T is investigated in some
detail, including studies of the relative importance of central and tensor
pieces of the force and of exchange and self-energy diagrams; in addition,
their role in significantly modifying the longitudinal parity-violating
response R_{AV}^L is explored. The MEC are shown to provide a small, but
non-negligible, contribution in determining the vector responses.Comment: TeX, 21 figures (Postscript, available from the authors), MIT
preprint CTP\#219
Influence of nucleonic motion in Relativistic Fermi Gas inclusive responses
Impulsive hadronic descriptions of electroweak processes in nuclei involve
two distinctly different elements: one stems from the nuclear many-body physics
--- the medium --- which is rather similar for the various inclusive response
functions, and the other embodies the responses of the hadrons themselves to
the electroweak probe and varies with the channel selected. In this letter we
investigate within the context of the relativistic Fermi gas in both the
quasi-elastic and regimes the interplay between these two
elements. Specifically, we focus on expansions in the one small parameter in
the problem, namely, the momentum of a nucleon in the initial wave function
compared with the hadronic scale, the nucleon mass. Both parity-conserving and
-violating inclusive responses are studied and the interplay between
longitudinal () and transverse ( and ) contributions is highlighted.Comment: 11 pages, 1 figur
Feynman Diagrams and Rooted Maps
The Rooted Maps Theory, a branch of the Theory of Homology, is shown to be a
powerful tool for investigating the topological properties of Feynman diagrams,
related to the single particle propagator in the quantum many-body systems. The
numerical correspondence between the number of this class of Feynman diagrams
as a function of perturbative order and the number of rooted maps as a function
of the number of edges is studied. A graphical procedure to associate Feynman
diagrams and rooted maps is then stated. Finally, starting from rooted maps
principles, an original definition of the genus of a Feynman diagram, which
totally differs from the usual one, is given.Comment: 20 pages, 30 figures, 3 table
Non-extensive statistics effects in quark-gluon plasma and in relativistic heavy-ion collisions
The presence of memory effects and color long-range forces among the
many-parton system in the early stage of heavy-ion collisions can affect the
particle statistical behavior at the freeze-out temperature. In this context,
we calculate, in the framework of the equilibrium generalized non-extensive
thermostatistics, the shape of pion transverse mass spectrum and the value of
the transverse momentum correlation function of the pions emitted during the
central Pb+Pb collisions and we show that the experimental results is well
reproduced assuming very small deviations from the standard statistics.Comment: 4 pages, contribution to the proceedings of the International
Conference on Quark Nuclear Physics (Adelaide, February 21-25, 2000
Conditions for detecting CP violation via neutrinoless double beta decay
Neutrinoless double beta decay data together with information on the absolute
neutrino masses obtained from the future KATRIN experiment and/or astrophysical
measurements give a chance to find CP violation in the lepton sector with
Majorana neutrinos. We derive and discuss necessary conditions which make
discovery of such CP violation possible for the future neutrino oscillation and
mass measurements data.Comment: 15 pages, 4 figures, RevTe
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