868 research outputs found
Light spin-1/2 or spin-0 Dark Matter particles
We recall and precise how light spin-0 particles could be acceptable Dark
Matter candidates, and extend this analysis to spin-1/2 particles. We evaluate
the (rather large) annihilation cross sections required, and show how they may
be induced by a new light neutral spin-1 boson U. If this one is vectorially
coupled to matter particles, the (spin-1/2 or spin-0) Dark Matter annihilation
cross section into e+e- automatically includes a v_dm^2 suppression factor at
threshold, as desirable to avoid an excessive production of gamma rays from
residual Dark Matter annihilations. We also relate Dark Matter annihilations
with production cross sections in e+e- scatterings. Annihilation cross sections
of spin-1/2 and spin-0 Dark Matter particles are given by exactly the same
expressions. Just as for spin-0, light spin-1/2 Dark Matter particles
annihilating into e+e- could be responsible for the bright 511 keV gamma ray
line observed by INTEGRAL from the galactic bulge.Comment: 10 page
Détermination du sexe de Globodera rostochiensis Woll. et influence des niveaux d'infestation sur la pénétration, le développement et le sexe de ce nématode
Upstream stimulators for recoding
Journal ArticleRecent progress in elucidation of 5' stimulatory elements for translational recoding is reviewed. A 5' Shine-Dalgarno sequence increases both +l and ? I frameshift efficiency in several genes; examples cited include the E. coli prfB gene encoding release factor 2 and the thuiX gene encoding the y and t subunits of DNA polymerase III holoenzyme. The spacing between the Shine-Dalgarno sequence and the shift site is critical in both the +l and ? 1 frameshift cassettes; however, the optimal spacing is quite different in the two cases. A frameshift in a mammalian chromosomal gene, ornithine decarboxylase antizyme, has recently been reported; 5' sequences have been shown to be vital for this frameshift event. Escherichia coli bacteriophage T4 gene 60 encodes a subunit of its type II DNA topoisomerase. The mature gene 60 mRNA contains an internal 50 nucleotide region that appears to be bypassed during translation. A 16 amino acid domain of the nascent peptide is necessary for this bypass to occur
Développement embryonnaire de Globodera rostochiensis et G. pallida en fonction de la température, en conditions contrÎlées et naturelles
Non-Minimal and Non-Universal Supersymmetry
I motivate and discuss non-minimal and non-universal models of supersymmetry
and supergravity consistent with string unification at GeV.Comment: 10 pages, Latex. Plenary talk given at 6th Workshop in High Energy
Physics Phenomenology (WHEPP 6), Chennai (Madras), India, 3-15 Jan 200
Study of the Gauge Mediation Signal with Non-pointing Photons at the CERN LHC
In this paper we study the gauge mediation signal with the ATLAS detector at
the CERN LHC. We focus on the case where the NLSP is the long-lived lightest
neutralino () which decays dominantly into a photon
() and a gravitino (). A non-pointing photon from the
neutralino decay can be detected with good position and time resolutions by the
electormagnetic calorimeter (ECAL), while the photon momentum would be
precisely measured if the photon is converted inside the inner tracking
detector before reaching the ECAL. A new technique is developed to determine
the masses of the slepton () and the neutralino from events with
a lepton and a converted non-pointing photon arising from the cascade decay
. A Monte Carlo
simulation at a sample point shows that the masses would be measured with an
error of 3% for (100) selected pairs. Once the sparticle
masses are determined by this method, the decay time and momentum of the
neutralino are solved using the ECAL data and the lepton momentum only, for all
pairs without the photon conversion. We estimate the sensitivity
to the neutralino lifetime for cm to (10) m.Comment: 19 page, 7 figures, revte
On non-universal Goldstino couplings to matter
Using the constrained superfields formalism to describe the interactions of a
light goldstino to matter fields in supersymmetric models, we identify
generalised, higher-order holomorphic superfield constraints that project out
the superpartners and capture the non-universal couplings of the goldstino to
matter fields. These arise from microscopic theories in which heavy
superpartners masses are of the order of the supersymmetry breaking scale
(\sqrt f). In the decoupling limit of infinite superpartners masses, these
constraints reduce to the familiar, lower-order universal constraints discussed
recently, that describe the universal goldstino-matter fields couplings,
suppressed by inverse powers of \sqrt f. We initiate the study of the couplings
of the Standard Model (SM) fields to goldstino in the constrained superfields
formalism.Comment: 28 pages; one comment adde
LHC Reach for Gauge Mediated Supersymmetry Breaking Models Via Prompt Photon Channels
We evaluate the supersymmetry reach of the Large Hadron Collider within the
gauge-mediated low energy supersymmetry breaking framework, assuming that a
neutralino is the second lightest sparticle and that it decays promptly into a
gravitino which escapes detection. We find that the maximum reach is obtained
via a search for inclusive \gamma\gamma+\eslt events coming dominantly from
chargino and neutralino production. Assuming an integrated luminosity of
10~, we find that LHC experiments will be able to probe values of the
model parameter \Lambda \alt 400 TeV, corresponding to
TeV. A measure of the model parameter may be possible from the photon
spectrum.Comment: 10 page Revtex file plus 4 EPS figure
Fitting Neutrino Physics with a U(1)_R Lepton Number
We study neutrino physics in the context of a supersymmetric model where a
continuous R-symmetry is identified with the total Lepton Number and one
sneutrino can thus play the role of the down type Higgs. We show that
R-breaking effects communicated to the visible sector by Anomaly Mediation can
reproduce neutrino masses and mixing solely via radiative contributions,
without requiring any additional degree of freedom. In particular, a relatively
large reactor angle (as recently observed by the Daya Bay collaboration) can be
accommodated in ample regions of the parameter space. On the contrary, if the
R-breaking is communicated to the visible sector by gravitational effects at
the Planck scale, additional particles are necessary to accommodate neutrino
data.Comment: 19 pages, 3 figures; v2: references added, constraints updated,
overall conclusions unchange
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