5,624 research outputs found
Indirect Detection of CMSSM Neutralino Dark Matter with Neutrino Telescopes
We review the prospects of detecting supersymmetric dark matter in the
framework of the Constrained Minimal Supersymmetric Standard Model, and compare
indirect with direct detection capabilities.Comment: 6 pages, 4 figures, presented by J. Orloff at the York IDM02 workshop
(http://www.shef.ac.uk/~phys/idm2002
Neutrino Indirect Detection of Neutralino Dark Matter in the CMSSM
We study potential signals of neutralino dark matter indirect detection by
neutrino telescopes in a wide range of CMSSM parameters. We also compare with
direct detection potential signals taking into account in both cases present
and future experiment sensitivities. Only models with neutralino annihilation
into gauge bosons can satisfy cosmological constraints and current neutrino
indirect detection sensitivities. For both direct and indirect detection, only
next generation experiments will be able to really test this kind of models.Comment: 16 pages, 19 figures; v4: a few clarifications and significant
improvement of reference
Jamming transition of a granular pile below the angle of repose
We study experimentally the relaxation towards mechanical equilibrium of a
granular pile which has just experienced an avalanche and discuss it in the
more general context of the granular jamming transition. Two coexisting
dynamics are observed in the surface layer: a short time exponential decay
consisting in rapid and independent moves of grains and intermittent bursts
consisting in spatially correlated moves lasting for longer time. The
competition of both dynamics results in long-lived intermittent transients, the
total duration of which can late more than a thousand of seconds. We measure a
two-time relaxation function, and relate it via a simple statistical model to a
more usual two-time correlation function which exhibits strong similarities
with auto-correlation functions found in aging systems. Localized perturbation
experiments also allow us to test the pile surface layer receptivity.Comment: 9 pages, 10 figure
Trap models with slowly decorrelating observables
We study the correlation and response dynamics of trap models of glassy
dynamics, considering observables that only partially decorrelate with every
jump. This is inspired by recent work on a microscopic realization of such
models, which found strikingly simple linear out-of-equilibrium
fluctuation-dissipation relations in the limit of slow decorrelation. For the
Barrat-Mezard model with its entropic barriers we obtain exact results at zero
temperature for arbitrary decorrelation factor . These are then
extended to nonzero , where the qualitative scaling behaviour and all
scaling exponents can still be found analytically. Unexpectedly, the choice of
transition rates (Glauber versus Metropolis) affects not just prefactors but
also some exponents. In the limit of slow decorrelation even complete scaling
functions are accessible in closed form. The results show that slowly
decorrelating observables detect persistently slow out-of-equilibrium dynamics,
as opposed to intermittent behaviour punctuated by excursions into fast,
effectively equilibrated states.Comment: 29 pages, IOP styl
Global fluctuations and Gumbel statistics
We explain how the statistics of global observables in correlated systems can
be related to extreme value problems and to Gumbel statistics. This
relationship then naturally leads to the emergence of the generalized Gumbel
distribution G_a(x), with a real index a, in the study of global fluctuations.
To illustrate these findings, we introduce an exactly solvable nonequilibrium
model describing an energy flux on a lattice, with local dissipation, in which
the fluctuations of the global energy are precisely described by the
generalized Gumbel distribution.Comment: 4 pages, 3 figures; final version with minor change
Orion revisited. II. The foreground population to Orion A
Following the recent discovery of a large population of young stars in front
of the Orion Nebula, we carried out an observational campaign with the DECam
wide-field camera covering ~10~deg^2 centered on NGC 1980 to confirm, probe the
extent of, and characterize this foreground population of pre-main-sequence
stars. We confirm the presence of a large foreground population towards the
Orion A cloud. This population contains several distinct subgroups, including
NGC1980 and NGC1981, and stretches across several degrees in front of the Orion
A cloud. By comparing the location of their sequence in various color-magnitude
diagrams with other clusters, we found a distance and an age of 380pc and
5~10Myr, in good agreement with previous estimates. Our final sample includes
2123 candidate members and is complete from below the hydrogen-burning limit to
about 0.3Msun, where the data start to be limited by saturation. Extrapolating
the mass function to the high masses, we estimate a total number of ~2600
members in the surveyed region. We confirm the presence of a rich, contiguous,
and essentially coeval population of about 2600 foreground stars in front of
the Orion A cloud, loosely clustered around NGC1980, NGC1981, and a new group
in the foreground of the OMC-2/3. For the area of the cloud surveyed, this
result implies that there are more young stars in the foreground population
than young stars inside the cloud. Assuming a normal initial mass function, we
estimate that between one to a few supernovae must have exploded in the
foreground population in the past few million years, close to the surface of
Orion A, which might be responsible, together with stellar winds, for the
structure and star formation activity in these clouds. This long-overlooked
foreground stellar population is of great significance, calling for a revision
of the star formation history in this region of the Galaxy.Comment: Accepted for publication in A&
Analysis of the low-energy differential cross sections of the CHAOS Collaboration
This paper presents the results of an analysis of the low-energy
differential cross sections, acquired by the CHAOS Collaboration at TRIUMF
\cite{chaos,denz}. We first analyse separately the and the
elastic-scattering measurements on the basis of standard low-energy
parameterisations of the - and p-wave -matrix elements. After the removal
of the outliers, we subject the truncated elastic-scattering
databases into a common optimisation scheme using the ETH model \cite{glmbg};
the optimisation failed to produce reasonable values for the model parameters.
We conclude that the problems we have encountered in the analysis of these data
are due to the shape of the angular distributions of their
differential cross sections
- …