262 research outputs found
New bounds on neutrino magnetic moment and re-examination of plasma effect in neutrino spin light
Recent discussion on the possibility to obtain more stringent bounds on
neutrino magnetic moment has stimulated new interest to possible effects
induced by neutrino magnetic moment. In particular, in this note after a short
review on neutrino magnetic moment we re-examine the effect of plasmon mass on
neutrino spin light radiation in dense matter. We track the entry of the
plasmon mass quantity in process characteristics and found out that the most
substantial role it plays is the formation of the process threshold. It is
shown that far from this point the plasmon mass can be omitted in all the
corresponding physical quantities and one can rely on the results of massless
photon spin light radiation theory in matter.Comment: to appear in Nuovo Cimento 35 C, No. 1, 2012 (based on the talk
presented at the 25th Rencontres de Physique de la Vallee d'Aoste on "Results
and Perspectives in Particle Physics", La Thuile, February 27 - March 5, 201
Scaling Properties of the Probability Distribution of Lattice Gribov Copies
We study the problem of the Landau gauge fixing in the case of the SU(2)
lattice gauge theory. We show that the probability to find a lattice Gribov
copy increases considerably when the physical size of the lattice exceeds some
critical value , almost independent of the lattice
spacing. The impact of the choice of the copy on Green functions is presented.
We confirm that the ghost propagator depends on the choice of the copy, this
dependence decreasing for increasing volumes above the critical one. The gluon
propagator as well as the gluonic three-point functions are insensitive to
choice of the copy (within present statistical errors). Finally we show that
gauge copies which have the same value of the minimisation functional () are equivalent, up to a global gauge transformation, and
yield the same Green functions.Comment: replaced with revised version; 23 pages, 7 figures, 27 table
Improved treatment of the molecular final-states uncertainties for the KATRIN neutrino-mass measurement
The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the
effective mass of the electron antineutrino via a high-precision measurement of
the tritium beta-decay spectrum in its end-point region. The target
neutrino-mass sensitivity of 0.2 eV / c^2 at 90% C.L. can only be achieved in
the case of high statistics and a good control of the systematic uncertainties.
One key systematic effect originates from the calculation of the molecular
final states of T_2 beta decay. In the first neutrino-mass analyses of KATRIN
the contribution of the uncertainty of the molecular final-states distribution
(FSD) was estimated via a conservative phenomenological approach to be 0.02
eV^2 / c^4. In this paper a new procedure is presented for estimating the
FSD-related uncertainties by considering the details of the final-states
calculation, i.e. the uncertainties of constants, parameters, and functions
used in the calculation as well as its convergence itself as a function of the
basis-set size used in expanding the molecular wave functions. The calculated
uncertainties are directly propagated into the experimental observable, the
squared neutrino mass m_nu^2. With the new procedure the FSD-related
uncertainty is constrained to 0.0013 eV^2 / c^4, for the experimental
conditions of the first KATRIN measurement campaign
Non-Perturbative Approach to the Landau Gauge Gluodynamics
We discuss a non-perturbative lattice calculation of the ghost and gluon
propagators in the pure Yang-Mills theory in Landau gauge. The ultraviolet
behaviour is checked up to NNNLO yielding the value
\Lambda^{n_f=0}_{\ms}=269(5)^{+12}_{-9}\text{MeV}, and we show that lattice
Green functions satisfy the complete Schwinger-Dyson equation for the ghost
propagator for all considered momenta. The study of the above propagators at
small momenta showed that the infrared divergence of the ghost propagator is
enhanced, whereas the gluon propagator seem to remain finite and non-zero. The
result for the ghost propagator is consistent with the analysis of the
Slavnov-Taylor identity, whereas, according to this analysis, the gluon
propagator should diverge in the infrared, a result at odds with other
approaches.Comment: To appear in the proceedings of the workshop "Hadron Structure and
QCD: from LOW to HIGH energies" (St. Petersburg, Russia, 20-24 September
2005
- …