Search results for "Database"
showing 10 items of 2136 documents
Polar Sets in a Nonlinear Potential Theory
1988
In this lecture we discuss nonlinear potential theory based on “A-super-harmonic functions”; the theory can be viewed as a (nonlinear) extension of the classical study of superharmonic functions in ℝn.
Cosmic ray physics with the ALEPH detector
2000
Abstract ALEPH is one of the four detectors at the Large Electron–Positron Collider (LEP) at a depth of about 320 m.w.e. Its hadron calorimeter and scintillator arrays installed at distances up to about 1 km away from ALEPH are used to measure cosmic muon induced time coincidences over large distances. The aim of this experiment (CosmoALEPH) is (1) to study the muon component above 70 GeV of Extensive Air Showers (EAS) and (2) to test the feasibility of searching for time correlations over even larger distances (up to 8 km) between the four LEP detectors. Layout and first results of CosmoALEPH are presented demonstrating the potential for cosmic ray physics in the LEP tunnel. The multiplici…
CMB anisotropies: cosmic confusion and polarization
2001
Abstract Some physical effects producing Cosmic Microwave Background (CMB) anisotropies are briefly described. The CMB angular power spectrum is calculated -in appropriate cases- with the essential aim of estimating and comparing the effects produced by reionization and gravitational waves; thus a problem of Cosmic Confusion is pointed out. Accurate measurements of the CMB polarization could solve this problem in future. Some comments about the PLANCK mission —ESA project for anisotropy detection— are given.
Searching for localized cosmic particle sources with an unbinned maximum likelihood approach
2006
Abstract An unbinned method to search for localized cosmic particle sources is presented. The expected source shape, the measured background shape, and the estimated angular resolution of individual tracks are used to construct a likelihood function. Estimates of the flux, the position and—in particular—the significance of a source can be readily obtained. A full confidence belt construction to deduce flux limits is presented. General statistical issues when searching for sources of unknown position are discussed.
Commissioning the ATLAS silicon microstrip tracker
2009
Abstract The completed SemiConductor Tracker (SCT) has been installed inside ATLAS. Quick tests were performed last year to verify the connectivity of the electrical and optical services. Problems observed with the heaters for the evaporative cooling system have been resolved. This has enabled extended operation of the full detector under realistic conditions. Calibration data has been taken and analyzed to determine the noise performance of the system. In addition, extensive commissioning with cosmic ray events has started. The cosmic muon data has been used to align the detector, to check the timing of the front-end electronics as well as to measure the hit efficiency of modules. The curr…
Measurement of fission fragments energy loss
2002
Abstract The mean energy of 252 Cf fission fragments emerging from an absorber and the determination of the capture rate in the absorber itself have been measured using two independent and complementary nuclear techniques. The results can be applied to the measurement of the energy self-absorption in a non-zero thickness source and can be used to validate simulation programs.
Neutrino observatories can characterize cosmic sources and neutrino properties
2003
Neutrino telescopes that measure relative fluxes of ultrahigh-energy $\nu_{e}, \nu_{\mu}, \nu_{\tau}$ can give information about the location and characteristics of sources, about neutrino mixing, and can test for neutrino instability and for departures from CPT invariance in the neutrino sector. We investigate consequences of neutrino mixing for the neutrino flux arriving at Earth, and consider how terrestrial measurements can characterize distant sources. We contrast mixtures that arise from neutrino oscillations with those signaling neutrino decays. We stress the importance of measuring $\nu_{e}, \nu_{\mu}, \nu_{\tau}$ fluxes in neutrino observatories.
Improved unitarized Heavy Baryon Chiral Perturbation Theory for π N scattering
2000
We show how the unitarized description of pion nucleon scattering within Heavy Baryon Chiral Perturbation Theory can be considerably improved, by a suitable reordering of the expansion over the nucleon mass. Within this framework, the $\Delta$ resonance and its associated pole can be recovered from the chiral parameters obtained from low-energy determinations. In addition, we can obtain a good description of the six $S$ and $P$ wave phase shifts in terms of chiral parameters with a natural size and compatible with the Resonance Saturation Hypothesis.
Thermal leptogenesis in extended supersymmetric seesaw model
2006
We consider an extended supersymmetric SO(10) seesaw model with only doublet Higgs scalars, in which neutrino masses are suppressed by the scale of D-parity violation. Leptogenesis can occur at the TeV scale through the decay of a singlet Sigma, thereby avoiding the gravitino crisis. Washout of the asymmetry can be effectively suppressed by the absence of direct couplings of Sigma to leptons.
Modelling jet quenching
2013
Abstract High P T measurements of hard hadrons or jets at RHIC and LHC appear contradictory and in some cases counterintuitive, but upon closer investigation they represent a coherent picture of jet-medium interaction physics which can be established with systematic comparisons of models against a large body of data. This picture is consistent with a perturbative QCD mechanism and does not require exotic assumptions. This overview outlines how several key measurements each partially constrain shower-medium interaction physics and how from the sum of those the outlines of the mechanism of jet quenching can be deduced. Most current jet results from LHC can be naturally understood in this pict…