37,084 research outputs found
Exclusive pion electroproduction off nucleons and nuclei
We present our results for the exclusive electroproduction of pions off
nucleons and nuclei at high values of . In electroproduction of nuclei
we consider the Color Transparency (CT) effect recently observed
at JLAB. It is shown that the description of production off nucleons is
mandatory for the proof of the CT signal at JLAB. We further develop the models
for exclusive production of off nucleons at JLAB and HERMES. At first we
describe a model based on exclusive-inclusive connection. In the second
approach we combine a Regge pole approach with the residual effect of nucleon
resonances. The nucleon resonances are described using a dual connection
between the exclusive form factors and inclusive deep inelastic structure
functions. We present the results for the beam spin azimuthal asymmetries
measured at JLAB in exclusive electroproduction of charged and neutral pions.Comment: 15 pages, 10 figures. Invited talk at the NAPP 2010 - 3rd
International Conference on Nuclear and Particle Physics with CEBAF, October
3rd to 8th 2010, Dubrovnik, Croati
NMSSM with a singlino LSP: possible challenges for searches for supersymmetry at the LHC
A light singlino in the NMSSM can reduce considerably the missing transverse
energy at the end of sparticle decay cascades; instead, light NMSSM-specific
Higgs bosons can be produced. Such scenarios can be consistent with present
constraints from the LHC with all sparticle masses below ~1 TeV. We discuss
search strategies, which do not rely on missing transverse energy, for such
scenarios at the next run of the LHC near 14 TeV.Comment: 20 pages, 9 Figures. References and experimental constraints added;
slight change of benchmark point, conclusions unchange
Resolubility of Image-Potential Resonances
A theory of image-potential states is presented for the general case where
these surface electronic states are resonant with a bulk continuum. The theory
extends the multiple scattering approach of Echenique and Pendry into the
strong coupling regime while retaining independence from specific forms of
surface and bulk potentials. The theory predicts the existence of a
well-resolved series of resonances for arbitrary coupling strengths.
Surprisingly, distinct image-potential resonances are thus expected to exist on
almost any metal surface, even in the limiting case of jellium
Deep exclusive electroproduction of at HERMES
Deeply virtual electroproduction of pion in exclusive reaction
is studied using a two-component model which includes soft
hadronic and hard partonic reaction mechanisms. The results are compared with
the experimental data measured at HERMES in the deep inelastic region for
values of GeV and GeV. At forward angles the
cross section is longitudinal and is dominated by exchange of Regge poles, with
the dominant trajectory. The off-forward region with GeV is
transverse and shows the dominance of partonic subprocesses. An implication of
present results for the future JLAB facilities are briefly discussed.Comment: 10 pages, 4 figure
T cell-specific suppressor factor(s) with regulatory influence on interleukin 2 production and function
In this study we report that alloantigen-activated spleen cells produce both amplifying and suppressive factors under the same conditions. Both types of soluble mediators--as detected in different assay systems-- were present in the supernatants of in vivo sensitized and in vitro restimulated spleen cell populations and were separable by gel filtration. As shown by others, the amplifying factor (IL 2) was eluted in the size range of 30,000 m.w. The suppressive factor(s) (SF) was eluted in the size range of 10,000 m.w. SF was shown to inhibit the proliferative response of T cells to alloantigen, as well as the generation of regulatory T cells and cytotoxic T cells from their precursors when added at the beginning of the in vitro culture. Furthermore, SF inhibited the release of IL 2 from producer T cells but had no detectable effect on the interaction of IL 2 with receptive T cells. In addition it was shown that SF does not affect the generation of PFC from their precursors after activation by T cell-independent antigens. The results indicate that SF selectively acts on T cells and that it is involved in the regulation of the immune response by modulating early events in T cell activation
Deep exclusive charged electroproduction above the resonance region
A description of exclusive charged pion electroproduction
off nucleons at high energies is proposed. The model combines a Regge pole
approach with residual effect of nucleon resonances. The exchanges of
(140), vector and axial-vector and
Regge trajectories are considered. The contribution of nucleon resonances is
described using a dual connection between the exclusive hadronic form factors
and inclusive deep inelastic structure functions. The model describes the
measured longitudinal, transverse and interference cross sections at JLAB and
DESY. The scaling behavior of the cross sections is in agreement with JLAB and
deeply virtual HERMES data. The results for a polarized beam-spin azimuthal
asymmetry in are presented. Model predictions for JLAB
at 12 GeV are given.Comment: 29 page
LHC constraints on M_1/2 and m_0 in the semi-constrained NMSSM
Constraints from searches for squarks and gluinos at the LHC at sqrt{s}=8 TeV
are applied to the parameter space of the NMSSM with universal squark/slepton
and gaugino masses at the GUT scale, but allowing for non-universal soft Higgs
mass parameters (the sNMSSM). We confine ourselves to regions of the parameter
space compatible with a 125 GeV Higgs boson with diphoton signal rates at least
as large as the Standard Model ones, and a dark matter candidate compatible
with WMAP and XENON100 constraints. Following the simulation of numerous points
in the m_0-M_{1/2} plane, we compare the constraints on the sNMSSM from 3-5
jets + missing E_T channels as well as from multijet + missing E_T channels
with the corresponding cMSSM constraints. Due to the longer squark decay
cascades, lower bounds on M_{1/2} are alleviated by up to 50 GeV. For heavy
squarks at large m_0, the dominant constraints originate from multijet +
missing E_T channels due to gluino decays via stop pairs.Comment: 18 pages, 2 Tables, 3 Figure
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