120842226
GALACTIC MODEL UNCERTAINTIES IN INDIRECT DARK MATTER SEARCH
If Dark Matter (DM) particles are a thermal relic from the early universe, they are expected to annihilate into quarks and leptons in order to reduce the number density with respect to the number of photons. The annihilation into quarks is expected to be dominant which may lead to a significant excess in gamma rays, antiprotons and positrons, as discussed in recent reviews. An excess in gamma rays above the background from interactions between cosmic rays (CR) and the interstellar medium has indeed been observed by the EGRET gamma ray spectrometer on board of the NASA Compton Gamma Ray Observatory, which has been taken data in space between the years 1991 and 2000. This excess shows all the properties of the annihilation of a 60 GeV Weakly Interacting Massive Particle (WIMP), as discussed by de Boer et al. . Especially the distribution of the excess could be used to predict the shape of the rotation curve of the Galaxy, thus proving that the excess is a tracer of Dark Matter. The main assumption in this analysis was that the shape of the CR background is the same everywhere in the Galaxy, as is expected from the fact that the energy loss time for protons is large compared with the diffusion time. The interaction of CR protons with the interstellar gas is the major source of background for gamma ray energies in the few GeV range. The CR electrons have large energy losses by inverse Compton scattering and Bremsstrahlung, which are additional sources of gamma rays. It is the main purpose of the present note to study the uncertainties in the shape of the CR background and the corresponding uncertainties in the gamma ray spectra. This was done with the publicly available GALPROP propagation model after modifying it to include DMA. In addition the effects of the inhomogeneous local solar neighborhood were studied. Furthermore anisotropic diffusion, expected in spiral galaxies with strong anisotropic magnetic fields, was studied which increases the uncertainties of charged secondary particles by a wide margin. The latter is relevant, since in a recent paper Bergstrom et al. claimed that the flux of antiprotons excludes the DMA interpretation of the EGRET excess. This conclusion was based on their isotropic propagation model in the DarkSusy program.
16250559
Determination of the local dark matter density in our Galaxy
Context. The rotation curve, the total mass and the gravitational potential of the Galaxy are sensitive measurements of the dark matter halo profile. Aims. Cuspy and cored DM halo profiles are analysed with respect to recent astronomical constraints in order to constrain the shape of the Galactic DM halo and the local DM density. Methods. All Galactic density components (luminous matter and DM) are parametrized. Then the total density distribution is constrained by astronomical observations: 1) the total mass of the Galaxy, 2) the total matter density at the position of the Sun, 3) the surface density of the visible matter, 4) the surface density of the total matter in the vicinity of the Sun, 5) the rotation speed of the Sun and 6) the shape of the velocity distribution within and above the Galactic disc. The mass model of the Galaxy is mainly constrained by the local matter density (Oort limit), the rotation speed of the Sun and the total mass of the Galaxy from tracer stars in the halo. Results. We showed from a statistical χ 2 fit to all data that the local DM density is strongly positively (negatively) correlated with the scale length of the DM halo (baryonic disc). Since these scale lengths are poorly constrained the local DM density can vary from 0.2 · �
55821746
Trilepton final state from neutralino-chargino production in mSUGRA.
The direct production of neutralino-chargino pairs in the mSUGRA scenario with decays into pure trilepton final states has a significant cross section for low neutralino masses. The trilepton signature was studied with the full and fast CMS detector simulations. The 5 signal can be observed in the dilepton invariant mass distribution at the integrated luminosity of L 30 fb for GeV.
125660697
IS THE DARK MATTER INTERPRETATION OF THE EGRET GAMMA RAY EXCESS COMPATIBLE WITH ANTIPROTON MEASUREMENTS
119402979
Antimatter and matter production in heavy ion collisions at CERN (The NEWMASS experiment NA52)
Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. Together with previous data taking at a rigidity of -20 GeV/c we obtained 10^6 antiprotons 10^3 antideuterons and two antihelium3 without centrality requirements. We measured nuclei and antinuclei (p,d,antiprotons, antideuterons) near midrapidity covering an impact parameter range of b=2-12 fm. Our results strongly indicate that nuclei and antinuclei are mainly produced via the coalescence mechanism. However the centrality dependence of the antibaryon to baryon ratios show that antibaryons are diminished due to annihilation and breakup reactions in the hadron dense environment. The volume of the particle source extracted from coalescence models agrees with results from pion interferometry for an expanding source. The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide with each other and with the thermal freeze-out of hadrons.
55139157
SLHC tracker upgrade: challenges and strategies in ATLAS
The Large Hadron Collider (LHC) will be upgraded to the Super-LHC in ≈2016 to provide a ten-fold increased luminosity and data rate. The inner silicon tracking detectors of the ATLAS and CMS experiments will be replaced by even more powerful devices. The new detectors will face unprecedented particle densities and radiation levels. Limiting the power consumption of the front-end electronics, distributing power efficiently and minimizing detector mass, while keeping the costs of the detector affordable, are key challenges. Possible design solutions and the status of R&D for ATLAS are described.
7496605
Serial Powering for Silicon Strip Detectors at SLUC
Serial powering of silicon sensors is a novel powering scheme that would reduce the total power, the number of cables, the passive detector material, and the costs of future silicon trackers by large factors. Modules are chained in series and are served by a single current source. Serial powering is of great interest for future large-scale silicon tracking detectors for particle physics with many thousands of densely packed detector modules. Tests with six ATLAS semiconductor tracker (SCT) modules using both serial powering and the conventional independent powering have been carried out. The electrical performance of SCT modules powered in series is excellent. We present selected results and discuss the system aspects of a serial powering.
116194687
Scintillator materials for calorimetry
Requirements for fast, dense scintillator materials for calorimetry in high energy physics and approaches to satisfying these requirements are reviewed with respect to possible hosts and luminescent species. Special attention is given to cerium-activated crystals, core-valence luminescence, and glass scintillators. The present state of the art, limitations, and suggestions for possible new scintillator materials are presented.
121921718
Hadronic response and e / pi separation with the H1 lead / fiber calorimeter
Hadronic response and electron identification performance of the new H1 lead-scintillating fibre calorimeter are investigated in the 1 to 7 GeV energy range using data taken at the CERN Proton Synchrotron. The energy response to minimum ionizing particles and interacting pions are studied and compared to Monte Carlo simulations. The measured energy of pions interacting either in the electromagnetic or in the hadronic section is found to scale linearly with the incident energy, providing an energy resolution σE ∼ 38% within a depth of one interaction length and σE ∼ 29% for a total depth of two interaction lengths. Several electron identification estimators are studied and combined as a function of energy and impact point. The probability for pions to be misidentified as electrons of any measured energy above 1 GeV ranges from 5% (for 2 GeV incident pions) to 0.4% (at 7 GeV) for an electron detection efficiency of 90%. The probability for pions of a given energy to be misidentified as electrons of the same energy falls to 0.25% at 7 GeV.