Ref HAL: in2p3-00085111_v1
Ref Arxiv: hep-ex/0605079
DOI: 10.1140/epjc/s10052-006-0158-6
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
6 citations
Abstract:

A search for Higgs bosons produced in association with a fermion pair, and decaying to WW, is performed with the data collected by the ALEPH detector at centre-of-mass energies ranging from 191 to 209 GeV. The data correspond to an integrated luminosity of 453.2 pb^-1. Thirteen exclusive selections are developed according to the different final state topologies. No statistically significant evidence for a Higgs boson decaying into a WW pair has been found. An upper limit is derived, as a function of the Higgs boson mass, on the product of the e+e- -> Hff cross section and the H -> WW branching ratio. The data on the search for H -> WW are combined with previously published ALEPH results on the search for H -> gamma gamma, to significantly extend the limits on the mass of a fermiophobic Higgs boson.

Comments: 29 pages, 10 figures, Submitted to The European Physical Journal C

Ref HAL: hal-00288579_v1
Exporter : BibTex | endNote
Abstract:

The recent observations of sharp X-ray filaments in many young supernova remnants like CasA, Kepler or Tycho or in older ones like SN1006 led to the conclusion of an amplification of the magnetic field in regards to its standard interstellar medium values. This magnetic field is hardly of external origin and is certainly produced through the acceleration of cosmic-rays around the blast wave. The streaming instability driven by the upstream cosmic-ray gradient is one of the favourite way to generate the magnetic fluctuations to the required level. Recent theoretical progresses conclude that aside the usual resonant interaction an efficient non-resonant regime could be at the origin of the high magnetic fields in supernova blast waves. The present work, investigate this issue. In particular it shown that both non-resonant and resonant regimes should operate in supernova shocks. We discuss the saturation mechanisms of these regimes. We show that the turbulence spectrum is probably highly anisotropic both up- and downstream and we examine the consequences of anisotropy on the values of the magnetic field in the post shock regions as well as the cosmic-ray acceleration process.

Ref HAL: hal-00286553_v1
Exporter : BibTex | endNote
Abstract:

HESS is a Stereoscopic Astroparticle Experiment situed in the deserts of Namibia at 1800m of Altitude. Four 12m Telescopes provide stereoscopic data that permits a unique way of diminishing background events and best angular resolution. Its main characteristics are low energy threshold (100Gev) and substantial flux sensitivity (1% Crab units). We prsent here recent results for Galactic and ExtraGalactics Object as well as some more in depth studies from Data collected in the region of the Galactic Center.

Ref HAL: hal-00285058_v1
Exporter : BibTex | endNote
Abstract:

The current generation of very-high-energy (VHE) gamma-ray telescopes has revealed emission from a large number of sources which can be clearly identified with known supernova remnants (SNRs) or pulsar wind nebulae (PWNe). Most of these objects are also non-thermal X-ray emitters, and in many cases there is a remarkable morphological correspondence between the X-ray and TeV gamma-ray images. The current status of observational knowledge in the VHE gamma-ray domain for both categories of objects will be reviewed. Particular attention will be paid to the evidence for accelerated high-energy nuclei in SNRs, and to the complementarity of VHE observations and synchrotron X-ray observations in PWNe.

Ref HAL: in2p3-00252151_v1
Ref Arxiv: 0712.3151
DOI: 10.1103/PhysRevD.77.055014
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
6 citations
Abstract:

We study the complementarity between the indirect detection of dark matter with gamma-rays in H.E.S.S. and the supersymmetry searches with ATLAS at the Large Hadron Collider in the Focus Point region within the mSUGRA framework. The sensitivity of the central telescope of the H.E.S.S. II experiment with an energy threshold of ~ 20 GeV is investigated. We show that the detection of gamma-ray fluxes of O(10^-12) cm-2s-1 with H.E.S.S. II covers a substantial part of the Focus Point region which may be more difficult for LHC experiments. Despite the presence of multi-TeV scalars, we show that LHC will be sensitive to a complementary part of this region through three body NLSP leptonic decays. This interesting complementarity between H.E.S.S. II and LHC searches is further highlighted in terms of the gluino mass and the two lightest neutralino mass difference.

Comments: 11 pages, 6 figures, accepted for publication in Phys. Rev. D on February 7, 2008 (slight modifications: references updated and text improved)

Ref HAL: in2p3-00196769_v1
Ref Arxiv: 0712.1173
DOI: 10.1051/0004-6361:20078516
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
160 citations
Abstract:

Context.The detection of gamma rays in the very-high-energy (VHE) energy range (100 GeV-100 TeV) provides a direct view of the parent population of ultra-relativistic particles found in astrophysical sources. For this reason, VHE gamma rays are useful for understanding the underlying astrophysical processes in non-thermal sources. Aims.We investigate unidentified VHE gamma-ray sources that have been discovered with HESS in the most sensitive blind survey of the Galactic plane at VHE energies conducted so far. Methods.The HESS array of imaging atmospheric Cherenkov telescopes (IACTs) has a high sensitivity compared with previous instruments (~ in 25 h observation time for a point-source detection), and with its large field of view, is well suited for scan-based observations. The on-going HESS survey of the inner Galaxy has revealed a large number of new VHE sources, and for each we attempt to associate the VHE emission with multi-wavelength data in the radio through X-ray wavebands. Results. For each of the eight unidentified VHE sources considered here, we present the energy spectra and sky maps of the sources and their environment. The VHE morphology is compared with available multi-wavelength data (mainly radio and X-rays). No plausible counterparts are found.

Ref HAL: in2p3-00189509_v1
Ref Arxiv: 0711.3196
DOI: 10.1051/0004-6361:20078604
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
28 citations
Abstract:

AIMS: Very high energy (VHE; E>100 GeV) gamma-ray studies were performed for 18 active galactic nuclei (AGN) from a variety of AGN classes. METHODS: VHE observations of a sample of 14 AGN, considered candidate VHE emitters, were made with the High Energy Stereoscopic System (HESS) between January 2005 and July 2007. Large-zenith-angle observations of three northern AGN (Mkn 421, Mkn 501, 1ES 1218+304), known to emit VHE gamma rays, were also performed in order to sample their spectral energy distributions (SEDs) above 1 TeV. In addition, the VHE flux from 1ES 1101-232, previously detected by HESS in 2004-2005, was monitored during 2006 and 2007. RESULTS: As significant detections from the HESS observation program are reported elsewhere, the results reported here are primarily integral flux upper limits. The average exposure for each of the 14 VHE-candidate AGN is ~7 h live time, and the observations have an average energy threshold between 230 GeV and 590 GeV. Upper limits for these 14 AGN range from <0.9% to <4.9% of the Crab Nebula flux, and eight of these are the most constraining ever reported for the object. The brief (<2.2 h each) large-zenith-angle observations yield upper limits for Mkn 501 (<20% Crab above 2.5 TeV) and 1ES 1218+304 (<17% Crab above 1.0 TeV), and a marginal detection (3.5 sigma) of Mkn 421 (50% Crab above 2.1 TeV). 1ES 1101-232 was marginally detected (3.6 sigma, 1.7% Crab above 260 GeV) during the 2006 (13.7 h live time) observations, but not in the 2007 (4.6 h live time) data. The upper limit in 2007 (<1.9% Crab above 260 GeV) is below the average flux measured by HESS from 2004-2006.

Comments: 8 Pages, 2 Figures; Accepted on Nov 6, 2007 for publication in Astronomy & Astrophysics