2,015 research outputs found
Forward particle productions at RHIC and the LHC from CGC within local rcBK evolution
In order to describe forward hadron productions in high-energy nuclear
collisions, we propose a Monte-Carlo implementation of
Dumitru-Hayashigaki-Jalilian-Marian formula with the unintegrated gluon
distribution obtained numerically from the running-coupling BK equation. We
discuss influence of initial conditions for the BK equation by comparing a
model constrained by global fit of small-x HERA data and a newly proposed one
from the running coupling MV model.Comment: Talk given at conference Quark Matter 2011, 4 page
New Fermions at ee Colliders: II.~Signals and Backgrounds
We discuss the production, at high--energy ee linear colliders, of
new heavy fermions predicted by extensions of the Standard Model. We analyze in
great details the various signals and the corresponding backgrounds for both
pair production and single production in association with ordinary fermions.
Concentrating on new leptons, we use a model detector for ee collisions
at a center of mass energy of 500 GeV, to illustrate the discovery potential of
the Next Linear Colliders.Comment: 22 pages + 9 figures (not included: available by mail from A.
Djouadi), Preprint UdeM-LPN-TH-93-15
Slightly Non-Minimal Dark Matter in PAMELA and ATIC
We present a simple model in which dark matter couples to the standard model
through a light scalar intermediary that is itself unstable. We find this model
has several notable features, and allows a natural explanation for a surplus of
positrons, but no surplus of anti-protons, as has been suggested by early data
from PAMELA and ATIC. Moreover, this model yields a very small nucleon
coupling, well below the direct detection limits. In this paper we explore the
effect of this model in both the early universe and in the galaxy.Comment: 7 pages, 6 figures, v3: updated for new data, added discussion of
Ferm
Impact of the spectral hardening of TeV cosmic rays on the prediction of the secondary positron flux
The rise in the cosmic-ray positron fraction measured by the PAMELA satellite
is likely due to the presence of astrophysical sources of positrons, e.g.
pulsars, on the kpc scale around the Earth. Nevertheless, assessing the
properties of these sources from the positron data requires a good knowledge of
the secondary positron component generated by the interaction of cosmic rays
with the interstellar gas. In this paper, we investigate the impact of the
spectral hardening in the cosmic-ray proton and helium fluxes recently reported
by the ATIC2 and CREAM balloon experiments, on the predictions of the secondary
positron flux. We show that the effect is not negligible, leading to an
increase of the secondary positron flux by up to 60% above 100 GeV.
We provide fitting formulae that allow a straightforward utilization of our
results, which can help in deriving constraints on one's favorite primary
positron source, e.g. pulsars or dark matter.Comment: 8 pages, 4 figures (accepted in MNRAS 04-01-2011
Composition analysis of liquid particles in the Arctic stratosphere under synoptic conditions
International audienceSynoptic scale polar stratospheric clouds (PSCs) that formed without the presence of mountain lee waves were observed in early December 2002 from Kiruna/Sweden using balloon-borne instruments. The physical, chemical, and optical properties of the particles were measured. Within the PSC solid particles existed whenever the temperature was below the equilibrium temperature for nitric acid trihydrate and liquid particles appeared when the temperature fell below an even lower threshold about 3 K above the frost point with solid particles still present. The correlation of liquid supercooled ternary solution aerosols with local temperatures is a pronounced feature observed during this flight; average molar ratios H2O/HNO3 were somewhat higher than predicted by models. In addition HCl has been measured for the first time in liquid aerosols. The chlorine isotope signature served as a unique tool to identify unambiguously HCl dissolved in STS particles. Within a narrow temperature range of about three degrees above the frost point, the measured average amount of HCl in liquid particles is below 1 weight%
Composition analysis of liquid particles in the Arctic stratosphere
International audienceSynoptic scale polar stratospheric clouds (PSCs) that formed without the presence of mountain leewaves were observed in early December 2002 from Kiruna/Sweden using balloon-borne instruments. The physical, chemical, and optical properties of the particles were measured. Within the PSC solid particles existed whenever the temperature was below the equilibrium temperature for nitric acid trihydrate and liquid particles appeared when the temperature fell below an even lower threshold about 3 K above the frost point. The correlation of liquid supercooled ternary solution aerosols with local temperatures is a pronounced feature observed during this flight although the molar ratios H2O/HNO3 were about a factor of 2 higher than model predictions. In addition HCl has been measured for the first time in liquid aerosols. The chlorine isotope signature served as a unique tool to identify unambiguously HCl dissolved in STS particles. Within a narrow temperature range of about three degrees above the frost point, measured HCl molar ratios are below 1 weight%. There is only fair agreement with model predictions
- …