4,411 research outputs found
Analysis of the BATSE Continuous MER data
The CGRO/BATSE database includes many types of data such as the 16-channel
continuous background or medium energy resolution burst data (CONT and MER data
types). We have calculated some four hundred burst's medium energy resolution
spectra and Principal Component Analysis has been applied. We found five
components can describe GRBs' spectra.Comment: 4 pages, 2 figures, accepted in Nuovo Ciment
Heavy-ion physics results from CMS
This paper summarizes recent experimental results related to heavyion collisions from the CMS Collaboration. Global features, like charged particle and transverse-energy density as a function of pseudorapidity, as well as correlations, elliptic flow, and the production of hard probes like isolated photons, Z and W bosons, jets, J/ψ and Υ particles will be presented. Many of these observations
are possible for the first time at the LHC, and the CMS experimental apparatus is well suited to conduct detailed studies of hard probes in the recently collected
high-luminosity Pb + Pb data
Laser thermoelastic generation in metals above the melt threshold
An approach is presented for calculating thermoelastic generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation. Detailed consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the appearance and subsequent growth and then contraction of the melt pool, and the time dependent thermal conduction in the melt and surrounding solid throughout. The excitation of the ultrasound takes place during and shortly after the laser pulse and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. It is shown how, because of this, the output of the thermal simulations can be expressed as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response to these force distributions is obtained by two methods, the one based on the elastodynamic Green’s functions for plate geometry determined by the Cagniard generalized ray method and the other using a finite
element numerical method. The two approaches are in very close agreement. Numerical simulations are reported on the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshol
Analysis of the Swift Gamma-Ray Bursts duration
Two classes of gamma-ray bursts have been identified in the BATSE catalogs
characterized by durations shorter and longer than about 2 seconds. There are,
however, some indications for the existence of a third type of burst. Swift
satellite detectors have different spectral sensitivity than pre-Swift ones for
gamma-ray bursts. Therefore it is worth to reanalyze the durations and their
distribution and also the classification of GRBs. Using The First BAT Catalog
the maximum likelihood estimation was used to analyzed the duration
distribution of GRBs. The three log-normal fit is significantly (99.54 %
probability) better than the two for the duration distribution. Monte-Carlo
simulations also confirm this probability (99.2 %).Comment: NANJING GAMMA-RAY BURST CONFERENCE 200
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