24 research outputs found
MIMAC potential discovery and exclusion of neutralinos in the MSSM and NMSSM
The MIMAC project aims to provide a nominal fluorine detector for directional
detection of galactic dark matter recoil events. Its expected behavior reaches
an important part of the predicted spin dependent elastic scattering
interactions of the supersymmetric neutralino with protons. Hence, the
parameter space in the MSSM and the NMSSM models with neutralino dark matter
could be probed by such experimental efforts. In particular, a good sensitivity
to spin dependent interactions tackles parameter space regions to which the
predictions on spin independent interactions and indirect signatures are far
below current and projected experiments.Comment: Proceedings of the 3rd International conference on Directional
Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201
Three-dimensional track reconstruction for directional Dark Matter detection
Directional detection of Dark Matter is a promising search strategy. However,
to perform such detection, a given set of parameters has to be retrieved from
the recoiling tracks : direction, sense and position in the detector volume. In
order to optimize the track reconstruction and to fully exploit the data of
forthcoming directional detectors, we present a likelihood method dedicated to
3D track reconstruction. This new analysis method is applied to the MIMAC
detector. It requires a full simulation of track measurements in order to
compare real tracks to simulated ones. We conclude that a good spatial
resolution can be achieved, i.e. sub-mm in the anode plane and cm along the
drift axis. This opens the possibility to perform a fiducialization of
directional detectors. The angular resolution is shown to range between
20 to 80, depending on the recoil energy, which is however
enough to achieve a high significance discovery of Dark Matter. On the
contrary, we show that sense recognition capability of directional detectors
depends strongly on the recoil energy and the drift distance, with small
efficiency values (50%-70%). We suggest not to consider this information either
for exclusion or discovery of Dark Matter for recoils below 100 keV and then to
focus on axial directional data.Comment: 27 pages, 20 figure
Probing neutralino dark matter in the MSSM & the NMSSM with directional detection
We investigate the capability of directional detectors to probe neutralino
dark matter in the Minimal Supersymmetric Standard Model and the
Next-to-Minimal Supersymmetric Standard Model with parameters defined at the
weak scale. We show that directional detectors such as the future MIMAC
detector will probe spin dependent dark matter scattering on nucleons that are
beyond the reach of current spin independent detectors. The complementarity
between indirect searches, in particular using gamma rays from dwarf spheroidal
galaxies, spin dependent and spin independent direct search techniques is
emphasized. We comment on the impact of the negative results on squark searches
at the LHC. Finally, we investigate how the fundamental parameters of the
models can be constrained in the event of a dark matter signal.Comment: 21 pages, 16 figure
Molecular hydrogen in the z = 2.66 damped Lyman-alpha absorber toward Q J0643-5041
We use high signal-to-noise ratio, high-resolution VLT-UVES data of Q
J0643-5041 amounting to a total of more than 23 hours exposure time and fit the
neutral hydrogen, metals and H2 absorption features with multiple-component
Voigt profiles. We study the relative populations of H2 rotational levels and
the fine-structure excitation of neutral carbon to determine the physical
conditions in the H2-bearing cloud. We find some evidence for part of the
quasar broad line emission region not being fully covered by the H2-bearing
cloud. We measure a total neutral hydrogen column density of log N(H) = 21.03
+/- 0.08. Molecular hydrogen is detected in several rotational levels, possibly
up to J = 7, in a single component. The corresponding molecular fraction is log
f = -2.19+0.07-0.08, where f = 2N(H2)/(2N(H2)+N(H)). The H2 Doppler parameter
is of the order of 1.5 km/s for J = 0, 1 and 2 and larger for J>2. The
molecular component has a kinetic temperature of T = 80 K, which yields a mean
thermal velocity of about 1 km/s, consistent with the Doppler broadening of the
lines. The UV ambient flux is of the order of the mean ISM Galactic flux. We
discuss the possible detection of HD and derive an upper limit of log N(HD) <
13.65 +/- 0.07 leading to log HD/(2 H2) < -5.19 +/- 0.07 which is consistently
lower than the primordial D/H ratio. Metals span about 210 km/s with [Zn/H] =
-0.91 +/- 0.09 relative to solar, with iron depleted relative to zinc [Zn/Fe] =
0.45 +/- 0.06, and with the rare detection of copper. We follow the procedures
used in our previous works to derive a constraint on the cosmological variation
of the proton-to-electron mass ratio of (7.4 +/- 4.3 (stat) +/- 5.1 (syst))
ppm.Comment: 22 pages, 22 figures, submitted to & accepted by A&
The Higgs boson in the MSSM in light of the LHC
We investigate the expectations for the light Higgs signal in the MSSM in
different search channels at the LHC. After taking into account dark matter and
flavor constraints in the MSSM with eleven free parameters, we show that the
light Higgs signal in the channel is expected to be at most at
the level of the SM Higgs, while the from W fusion
and/or the can be enhanced. For the main discovery
mode, we show that a strong suppression of the signal occurs in two different
cases: low or large invisible width. A more modest suppression is
associated with the effect of light supersymmetric particles. Looking for such
modification of the Higgs properties and searching for supersymmetric partners
and pseudoscalar Higgs offer two complementary probes of supersymmetry.Comment: 19 pages, 8 figure
Primordial Nucleosynthesis
Primordial nucleosynthesis, or Big-Bang Nucleosynthesis (BBN), is one of the
three evidences for the Big-Bang model, together with the expansion of the
Universe and the Cosmic Microwave Background. There is a good global agreement
over a range of nine orders of magnitude between abundances of 4He, D, 3He and
7Li deduced from observations, and calculated in primordial nucleosynthesis.
This comparison was used to determine the baryonic density of the Universe. For
this purpose, it is now superseded by the analysis of the Cosmic Microwave
Background (CMB) radiation anisotropies. However, there remain, a yet
unexplained, discrepancy of a factor 3-5, between the calculated and observed
lithium primordial abundances, that has not been reduced, neither by recent
nuclear physics experiments, nor by new observations. We review here the
nuclear physics aspects of BBN for the production of 4He, D, 3He and 7Li, but
also 6Li, 9Be, 11B and up to CNO isotopes. These are, for instance, important
for the initial composition of the matter at the origin of the first stars.
Big-Bang nucleosynthesis, that has been used, to first constrain the baryonic
density, and the number of neutrino families, remains, a valuable tool to probe
the physics of the early Universe, like variation of "constants" or alternative
theories of gravity.Comment: Invited Plenary Talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Constraining the variation of fundamental constants at z ~ 1.3 using 21-cm absorbers
We present high resolution optical spectra obtained with the Ultraviolet and
Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT) and 21-cm
absorption spectra obtained with the Giant Metrewave Radio Telescope (GMRT) and
the Green Bank Telescope (GBT) of five quasars along the line of sight of which
21-cm absorption systems at 1.17 < z < 1.56 have been detected previously. We
also present milliarcsec scale radio images of these quasars obtained with the
Very Large Baseline Array (VLBA). We use the data on four of these systems to
constrain the time variation of x = g_p*alpha^2/mu where g_p is the proton
gyromagnetic factor, alpha is the fine structure constant, and mu is the
proton-to-electron mass ratio. We carefully evaluate the systematic
uncertainties in redshift measurements using cross-correlation analysis and
repeated Voigt profile fitting. In two cases we also confirm our results by
analysing optical spectra obtained with the Keck telescope. We find the
weighted and the simple means of Delta_x / x to be respectively -(0.1 +/-
1.3)x10^-6 and (0.0 +/- 1.5)x10^-6 at the mean redshift of = 1.36
corresponding to a look back time of ~ 9 Gyr. This is the most stringent
constraint ever obtained on Delta_x / x. If we only use the two systems towards
quasars unresolved at milliarcsec scales, we get the simple mean of Delta_x / x
= + (0.2 +/- 1.6)x10^-6. Assuming constancy of other constants we get
Delta_alpha / alpha = (0.0 +/- 0.8)x10^-6 which is a factor of two better than
the best constraints obtained so far using the Many Multiplet Method. On the
other hand assuming alpha and g_p have not varied we derive Delta_mmu / mu =
(0.0 +/- 1.5)x10^-6 which is again the best limit ever obtained on the
variation of mu over this redshift range. [Abridged]Comment: 22 pages, 15 figures, Accepted for publication in MNRA
Search for varying constants of nature from astronomical observation of molecules
The status of searches for possible variation in the constants of nature from
astronomical observation of molecules is reviewed, focusing on the
dimensionless constant representing the proton-electron mass ratio
. The optical detection of H and CO molecules with large
ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as
the detection of H with the Cosmic Origins Spectrograph aboard the Hubble
Space Telescope is discussed in the context of varying constants, and in
connection to different theoretical scenarios. Radio astronomy provides an
alternative search strategy bearing the advantage that molecules as NH
(ammonia) and CHOH (methanol) can be used, which are much more sensitive to
a varying than diatomic molecules. Current constraints are
for redshift , corresponding to
look-back times of 10-12.5 Gyrs, and for
, corresponding to half the age of the Universe (both at 3
statistical significance). Existing bottlenecks and prospects for future
improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the
International Space Science Institute, Bern 201
Les Houches 2011: Physics at TeV Colliders New Physics Working Group Report
We present the activities of the "New Physics" working group for the "Physics
at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our
report includes new agreements on formats for interfaces between computational
tools, new tool developments, important signatures for searches at the LHC,
recommendations for presentation of LHC search results, as well as additional
phenomenological studies.Comment: 243 pages, report of the Les Houches 2011 New Physics Group; fix
three figure