99 research outputs found
Dimensionally regulated one-loop box scalar integrals with massless internal lines
Using the Feynman parameter method, we have calculated in an elegant manner a
set of oneloop box scalar integrals with massless internal lines, but
containing 0, 1, 2, or 3 external massive lines. To treat IR divergences (both
soft and collinear), the dimensional regularization method has been employed.
The results for these integrals, which appear in the process of evaluating
oneloop point integrals and in subdiagrams in QCD loop
calculations, have been obtained for arbitrary values of the relevant kinematic
variables and presented in a simple and compact form.Comment: 14 pages, 2 figures included, SVJour, journal versio
IR finite one-loop box scalar integral with massless internal lines
The IR finite one-loop box scalar integral with massless internal lines has
been recalculated. The result is very compact, simple and valid for arbitrary
values of the relevant kinematic variables. It is given in terms of only two
dilogarithms and a few logarithms, all of very simple arguments.Comment: 7 pages, 2 figure
Absorption of solar radiation by solar neutrinos
We calculate the absorption probability of photons radiated from the surface
of the Sun by a left-handed neutrino with definite mass and a typical momentum
for which we choose |p_1|=0.2 MeV, producing a heavier right-handed
antineutrino. Considering two transitions the \nu_1 -> \nu_2 and \nu_2 -> \nu_3
we obtain two oscillation lengths L_{12}=4960.8 m, L_{23}=198.4 m, two
absorption probabilities P_{12}^{abs.}=2.5 10^{-67}, P_{23}^{abs.}=1.2 10^{-58}
and the two absorption ranges R_{12}^{abs.}=4.47 10^4 R_{\odot}=208.0 au,
R_{23}^{abs.}=0.89 10^4 R_{\odot}=41.4 au, using a neutrino mass differences of
\sqrt{|\Delta m^2_{12}|}=10 meV, \sqrt{|\Delta m^2_{23}|}=50 meV and associated
transition dipole moments. We collect all necessary theoretical ingredients,
i.e. neutrino mass and mixing scheme, induced electromagnetic transition dipole
moments, quadratic charged lepton mass asymmetries and their interdependence.Comment: 5 pages, 3 figures, typos corrected and reference added, version to
appear in Eur. Phys. J.
The impact of bars and interactions on optically selected AGNs in spiral galaxies
Aims. With the aim of performing a suitable comparison of the internal
process of galactic bars with respect to the external effect of interactions on
driving gas toward the inner most region of the galaxies, we explored the
efficiency of both mechanisms on central nuclear activity in active galactic
nuclei (AGN) in spiral galaxies. Methods. We selected samples of barred AGN and
active objects residing in pair systems, derived from the Sloan Digital Sky
Survey (SDSS). In order to carry out a reliable comparison of both samples
(AGNs in barred hosts in isolation and in galaxy pairs), we selected spiral AGN
galaxies with similar distributions of redshift, magnitude, stellar mass, color
and stellar age population from both catalogs. With the goal of providing an
appropriate quantification of the influence of bars and interactions on nuclear
activity, we also constructed a suitable control sample of unbarred spiral AGNs
with similar host properties than the other two samples. Results. We found that
barred AGNs show an excess of nuclear activity (as derived from the
) and accretion rate () with respect to AGN in pairs. In
addition, both samples show an excess of high values of and with respect to unbarred AGNs in the control sample. We also found that the
fractions of AGNs with powerful nuclear activity and high accretion rates
increase toward more massive hosts with bluer colors and younger stellar
populations. Moreover, AGNs with bars exhibit a higher fraction of galaxies
with powerful and efficient with respect to AGNs
inhabiting pair systems. Regarding to AGN belonging to pair systems, we found
that the central nuclear activity is remarkably dependent on the galaxy pair
companion features.Comment: 13 pages, 9 figures. Accepted for publication in A&
Hadronic Form Factors: Combining QCD Calculations with Analyticity
I discuss recent applications of QCD light-cone sum rules to various form
factors of pseudoscalar mesons. In this approach both soft and hard
contributions to the form factors are taken into account. Combining QCD
calculation with the analyticity of the form factors, one enlarges the region
of accessible momentum transfers.Comment: 12 pages, 3 figures, Talk at the Workshop "Shifmania, Crossing the
boundaries: Gauge dynamics at strong coupling", May 14-17,2009, Minneapolis,
USA; table entry and reference update
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