214 research outputs found
Leptogenesis and rescattering in supersymmetric models
The observed baryon asymmetry of the Universe can be due to the
violating decay of heavy right handed (s)neutrinos. The amount of the asymmetry
depends crucially on their number density. If the (s)neutrinos are generated
thermally, in supersymmetric models there is limited parameter space leading to
enough baryons. For this reason, several alternative mechanisms have been
proposed. We discuss the nonperturbative production of sneutrino quanta by a
direct coupling to the inflaton. This production dominates over the
corresponding creation of neutrinos, and it can easily (i.e. even for a rather
small inflaton-sneutrino coupling) lead to a sufficient baryon asymmetry. We
then study the amplification of MSSM degrees of freedom, via their coupling to
the sneutrinos, during the rescattering phase which follows the nonperturbative
production. This process, which mainly influences the (MSSM) flat
directions, is very efficient as long as the sneutrinos quanta are in the
relativistic regime. The rapid amplification of the light degrees of freedom
may potentially lead to a gravitino problem. We estimate the gravitino
production by means of a perturbative calculation, discussing the regime in
which we expect it to be reliable.Comment: (20 pages, 6 figures), references added, typos corrected. Final
version in revte
Immunoglobulin free light chains are biomarkers of poor prognosis in basal-like breast cancer and are potential targets in tumor-associated inflammation
Inflammation is an important component of various cancers and its inflammatory cells and mediators have been shown to have prognostic potential. Tumor-infiltrating mast cells can promote tumor growth and angiogenesis, but the mechanism of mast cell activation is unclear. In earlier studies, we demonstrated that immunoglobulin free light chains (FLC) can trigger mast cells in an antigen-specific manner. Increased expression of FLC was observed within stroma of various human cancers including those of breast, colon, lung, pancreas, kidney and skin, and FLC expression co-localized with areas of mast cell infiltration. In a large cohort of breast cancer patients, FLC expression was shown associated with basal-like cancers with an aggressive phenotype. Moreover, lambda FLC was found expressed in areas of inflammatory infiltration and its expression was significantly associated with poor clinical outcome. Functional importance of FLCs was shown in a murine B16F10 melanoma model, where inhibition of FLC-mediated mast cell activation strongly reduced tumor growth. Collectively, this study identifies FLCs as a ligand in the pro-tumorigenic activation of mast cells. Blocking this pathway may open new avenues for the inhibition of tumor growth, while immunohistochemical staining of FLC may be helpful in the diagnosis and prognosis of cancer
Deep Inelastic Scattering from off-Shell Nucleons
We derive the general structure of the hadronic tensor required to describe
deep-inelastic scattering from an off-shell nucleon within a covariant
formalism. Of the large number of possible off-shell structure functions we
find that only three contribute in the Bjorken limit. In our approach the usual
ambiguities encountered when discussing problems related to off-shellness in
deep-inelastic scattering are not present. The formulation therefore provides a
clear framework within which one can discuss the various approximations and
assumptions which have been used in earlier work. As examples, we investigate
scattering from the deuteron, nuclear matter and dressed nucleons. The results
of the full calculation are compared with those where various aspects of the
off-shell structure are neglected, as well as with those of the convolution
model.Comment: 36 pages RevTeX, 9 figures (available upon request), ADP-93-210/T128,
PSI-PR-93-13, accepted for publication in Physical Review
Relationship between panicle differentiation and main stem leaf number in rice genotypes and red rice biotypes
Distribution and fluctuations of backswimmers (Notonectidae) in a tropical shallow lake and predation on microcrustaceans
Energy and system size dependence of \phi meson production in Cu+Cu and Au+Au collisions
We study the beam-energy and system-size dependence of \phi meson production
(using the hadronic decay mode \phi -- K+K-) by comparing the new results from
Cu+Cu collisions and previously reported Au+Au collisions at \sqrt{s_NN} = 62.4
and 200 GeV measured in the STAR experiment at RHIC. Data presented are from
mid-rapidity (|y|<0.5) for 0.4 < pT < 5 GeV/c. At a given beam energy, the
transverse momentum distributions for \phi mesons are observed to be similar in
yield and shape for Cu+Cu and Au+Au colliding systems with similar average
numbers of participating nucleons. The \phi meson yields in nucleus-nucleus
collisions, normalised by the average number of participating nucleons, are
found to be enhanced relative to those from p+p collisions with a different
trend compared to strange baryons. The enhancement for \phi mesons is observed
to be higher at \sqrt{s_NN} = 200 GeV compared to 62.4 GeV. These observations
for the produced \phi(s\bar{s}) mesons clearly suggest that, at these collision
energies, the source of enhancement of strange hadrons is related to the
formation of a dense partonic medium in high energy nucleus-nucleus collisions
and cannot be alone due to canonical suppression of their production in smaller
systems.Comment: 20 pages and 5 figure
Polarized deep-inelastic scattering from nuclei: a relativistic approach.
We discuss spin-dependent, deep-inelastic scattering from nuclei within a covariant framework. In the relativistic impulse approximation this is described in terms of the amplitude for forward, virtual-photon scattering from an off-mass-shell nucleon. The general structure of the off-shell nucleon hadronic tensor is derived, and the leading behavior of the off-shell nucleon structure functions computed in the Bjorken limit. The formalism, which is valid for nucleons bound inside nuclei with spin 1/2 or 1, is applied to the case of the deuteron.Piller, G. ; Melnitchouk, W. ; Thomas, A.W
SPIN-DEPENDENT NUCLEAR STRUCTURE FUNCTIONS: GENERAL APPROACH WITH APPLICATION TO THE DEUTERON
We study deep-inelastic scattering from polarized nuclei within a covariant
framework. A clear connection is established between relativistic and
non-relativistic limits, which enables a rigorous derivation of convolution
formulae for the spin-dependent nuclear structure functions g_1^A and g_2^A in
terms of off-mass-shell extrapolations of polarized nucleon structure
functions, g_1^N and g_2^N. Approximate expressions for g_{1,2}^A are obtained
by expanding the off-shell g_{1,2}^N about their on-shell limits. As an
application of the formalism we consider nuclear effects in the deuteron,
knowledge of which is necessary to obtain accurate information on the
spin-dependent structure functions of the neutron.Comment: 26 pages RevTeX, 9 figures available upon reques
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