8,517 research outputs found

### Heavy meson production at a low-energy photon collider

A low-energy $\gamma\gamma$ collider has been discussed in the context of a
testbed for a $\gamma\gamma$ interaction region at the Next Linear Collider
(NLC). We consider the production of heavy mesons at such a testbed using
Compton-backscattered photons and demonstrate that their production rivals or
exceeds those by BELLE, BABAR or LEP where they are produced indirectly via
virtual $\gamma\gamma$ luminosities.Comment: 13 pages, 4 figures. Submitted as a proceeding to the 5$^{th}$
International Workshop on e$^-$e$^-$ Interactions at TeV Energies. To appear
in the International Journal of Modern Physics A, World Scientifi

### Reduced Fine-Tuning in Supersymmetry with R-parity violation

Both electroweak precision measurements and simple supersymmetric extensions
of the standard model prefer a mass of the Higgs boson less than the
experimental lower limit of 114 GeV. We show that supersymmetric models with R
parity violation and baryon number violation have a significant range of
parameter space in which the Higgs dominantly decays to six jets. These decays
are much more weakly constrained by current LEP analyses and would allow for a
Higgs mass near that of the $Z$. In general, lighter scalar quark and other
superpartner masses are allowed and the fine-tuning typically required to
generate the measured scale of electroweak symmetry breaking is ameliorated.
The Higgs would potentially be discovered at hadron colliders via the
appearance of new displaced vertices. The lightest neutralino could be
discovered by a scan of vertex-less events LEP I data.Comment: 5 pages, 2 figures. Significant detail added to the arguments
regarding LEP limits - made more quantitative. Better figures used, plotting
more physical quantities. Typos corrected and references updated. Conclusions
unchange

### Extremal functions for the anisotropic Sobolev inequalities

The existence of multiple nonnegative solutions to the anisotropic critical
problem - \sum_{i=1}^{N} \frac{\partial}{\partial x_i} (| \frac{\partial
u}{\partial x_i} |^{p_i-2} \frac{\partial u}{\partial x_i}) = |u|^{p^*-2} u
{in} \mathbb{R}^N is proved in suitable anisotropic Sobolev spaces. The
solutions correspond to extremal functions of a certain best Sobolev constant.
The main tool in our study is an adaptation of the well-known
concentration-compactness lemma of P.-L. Lions to anisotropic operators.
Futhermore, we show that the set of nontrival solutions \calS is included in
$L^\infty(\R^N)$ and is located outside of a ball of radius $\tau >0$ in
$L^{p^*}(\R^N)$

### Radiation Rates for Low Z Impurities in Edge Plasmas

The role of impurity radiation in the reduction of heat loads on divertor
plates in present experiments such as DIII-D, JET, JT-60, ASDEX, and Alcator
C-Mod, and in planned experiments such as ITER and TPX places a new degree of
importance on the accuracy of impurity radiation emission rates for electron
temperatures below 250 eV for ITER and below 150 eV for present experiments. We
have calculated the radiated power loss using a collisional radiative model for
Be, B, C, Ne and Ar using a multiple configuration interaction model which
includes density dependent effects, as well as a very detailed treatment of the
energy levels and meta-stable levels. The "collisional radiative" effects are
very important for Be at temperatures below 10 eV. The same effects are present
for higher Z impurities, but not as strongly. For some of the lower Z elements,
the new rates are about a factor of two lower than those from a widely used,
simpler average-ion package (ADPAK) developed for high Z ions and for higher
temperatures. Following the approach of Lengyel for the case where electron
heat conduction is the dominant mechanism for heat transport along field lines,
our analysis indicates that significant enhancements of the radiation losses
above collisional radiative model rates due to such effects as rapid recycling
and charge exchange recombination will be necessary for impurity radiation to
reduce the peak heat loads on divertor plates for high heat flux experiments
such as ITER.Comment: Preprint for the 11th PSI meeting, gzipped postscript with 11
figures, 14 page

### Analysis of a diffusive effective mass model for nanowires

We propose in this paper to derive and analyze a self-consistent model
describing the diffusive transport in a nanowire. From a physical point of
view, it describes the electron transport in an ultra-scaled confined
structure, taking in account the interactions of charged particles with
phonons. The transport direction is assumed to be large compared to the wire
section and is described by a drift-diffusion equation including effective
quantities computed from a Bloch problem in the crystal lattice. The
electrostatic potential solves a Poisson equation where the particle density
couples on each energy band a two dimensional confinement density with the
monodimensional transport density given by the Boltzmann statistics. On the one
hand, we study the derivation of this Nanowire Drift-Diffusion Poisson model
from a kinetic level description. On the other hand, we present an existence
result for this model in a bounded domain

### Z'-induced Invisible Right-handed Sneutrino Decays at the LHC

The invisible signals of right-handed sneutrino decays originating from a Z'
are analysed at the Large Hadron Collider. The possibility of accessing these
events helps disentangling the B-L extension of Minimal Supersymmetric Standard
Model from more popular scenarios of Supersymmetry. We assess the scope of the
CERN machine in establishing the aforementioned signatures when accompanied by
mono-jet, single-photon or Z-radiation probes through sophisticated
signal-to-background simulations carried out in presence of parton shower,
hadronisation as well as detector effects. We find substantial sensitivity to
all such signals for standard luminosities at Run 2.Comment: 4 pages, 3 figure

### Contribution to the study of farming systems in the West Bank : the case of Deir-Elhatab village in the district of Nablus

Une étude a été menée au village de Deir-Elhatab dans le district de Naplouse(Palestine) pour contribuer au diagnostic des systèmes agraires en Palestine.Les aspects zootechniques et socio-économiques des exploitations ont été étudiés. L'étude a révélé l'importance de la production agricole pour la consommation familiale dans les petites exploitations et comme source derevenus dans les grandes exploitations. Cinq types d'exploitations agricoles ont été identifiés à partir de 47 exploitations. Parmi les contraintes majeures on a trouvé l'augmentation rapide des coûts d'alimentation des animaux, les problèmes sanitaires, la productivité faible et l'accès limitéaux pâturages naturels et aux plantations d'oliviers à cause de la présence d'une colonie israélienne à côté du village. L'amélioration des pratiquesde gestion peut résoudre une partie des problèmes

### Single and Pair Production of Doubly Charged Higgs Bosons at Hadron Colliders

Current searches for doubly charged Higgs bosons (H^{\pm\pm}) at the Fermilab
Tevatron are sensitive to single production of H^{\pm\pm}, although the pair
production mechanism q\bar q\to H^{++}H^{--} is assumed to be dominant. In the
context of a Higgs Triplet Model we study the mechanism q'\bar q\to
H^{\pm\pm}H^{\mp} at the Tevatron and CERN Large Hadron Collider, and show that
its inclusion can significantly improve the search potential for H^{\pm\pm}.
Moreover, assuming that the neutrino mass is generated solely by the triplet
field Yukawa coupling to leptons, we compare the branching ratios of
H^{\pm\pm}\to l^\pm l^\pm and H^{\pm\pm}\to H^\pm W^* for the cases of a normal
hierarchical, inverted hierarchical and degenerate neutrino mass spectrum.Comment: 17 pages, 15 figures, references added, version to appear in PR

### Inert Doublet Model and LEP II Limits

The inert doublet model is a minimal extension of the standard model
introducing an additional SU(2) doublet with new scalar particles that could be
produced at accelerators. While there exists no LEP II analysis dedicated for
these inert scalars, the absence of a signal within searches for supersymmetric
neutralinos can be used to constrain the inert doublet model. This translation
however requires some care because of the different properties of the inert
scalars and the neutralinos. We investigate what restrictions an existing
DELPHI collaboration study of neutralino pair production can put on the inert
scalars and discuss the result in connection with dark matter. We find that
although an important part of the inert doublet model parameter space can be
excluded by the LEP II data, the lightest inert particle still constitutes a
valid dark matter candidate.Comment: 12 pages, 9 figures; v2: published versio

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