Search results for "SPECTRA"
showing 10 items of 3542 documents
Hydrodynamical Description of 200 A GeV/c S+Au Collisions: Hadron and Electromagnetic Spectra
1996
We study relativistic S+Au collisions at 200 A GeV/c using a hydrodynamical approach. We test various equations of state (EOSs), which are used to describe the strongly interacting matter at densities attainable in the CERN-SPS heavy ion experiments. For each EOS, suitable initial conditions can be determined to reproduce the experimental hadron spectra; this emphasizes the ambiguity between the initial conditions and the EOS in such an approach. Simultaneously, we calculate the resulting thermal photon and dielectron spectra, and compare with experiments. If one allows the excitation of resonance states with increasing temperature, the electro-magnetic signals from scenarios with and witho…
Photon emission in heavy ion collisions at the CERN SPS
2001
We compute the thermal photon spectrum in the Pb+Pb collisions at the CERN SPS energy using thermal emission rates and a hydrodynamic description for the evolution of produced hot matter and compare our results with the measurements of the excess photons by the WA98 collaboration. Our results show that the measured photon spectrum can be reproduced with realistic initial conditions which take properly into account also the finite longitudinal size of the initial collision zone and which simultaneously describe well both the transverse and longitudinal hadron spectra. In the scenario with initial formation of QGP the recently calculated emission rate, complete to order alpha_s, reproduces th…
Response of BGO detectors to photons of 3–50 MeV energy
1993
Abstract The response of an array of 7 hexagonal BGO detectors each 7.5 cm long (6.7 radiation lengths) with 3.6 cm side-to-side distance was measured using monochromatic photons from the tagged-photon facility at the electron accelerator MAMI A at Mainz. The experimental spectra of the deposited energy for a single detector and for the array of seven modules compare very well with the predictions of Monte Carlo shower simulations using the code GEANT3. Significant improvement of the energy resolution is observed for the summed energy spectra compared to the resolution of a single module. This improvement deteriorates at higher photon energies because the length of the detector is not suffi…
Optical properties and spectrometric performance of TlBr detector crystals
2006
Abstract It is shown that preliminary TlBr crystals optical parameters testing can be used for detector crystal selection. Absorption in fundamental spectral region was used for the band gap width definition and determination of homological impurities presence. The luminescence was applied for impurity and defects content study. Radionuclide spectra 241Am were measured using the ionizing radiation detectors with planar electrodes made from TlBr crystals. The detector energy resolution for TlBr detectors produced from different row materials was summarized and the results of detector testing parameters and results of optical investigation were compared.
Optical investigations of TlBr detector crystals
2004
Shift of fundamental absorption edge, the position of main luminescence bands, the luminescence decay and transient absorption spectra in three TlBr crystals were studied. The γ-quanta detector made from TlBr crystals with similar transient absorption and luminescence parameters shows similar detector properties. The iodine impurity in TlBr was detected by optical methods. The role of impurities and crystal defects in γ-quanta detectors manufactured is discussed.
Investigation of multiparticle final states in12C photoreactions
1998
The ${}^{12}\mathrm{C}(\ensuremath{\gamma},pn)$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},pp)$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},ppp)$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},pp{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}})$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},p{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}})$ reactions have been studied using tagged photons of energy ${E}_{\ensuremath{\gamma}}=250$--600 MeV. A model which includes all major absorption mechanisms and final state interactions gives results that agree well with the shapes of missing energy spectra, but for some channels the predicted cross sections are too large.
Neutron and proton spectra from the decay ofΛhypernuclei
1997
We have determined the spectra of neutrons and protons following the decay of {Lambda} hypernuclei through the one- and two-nucleon-induced mechanisms. The momentum distributions of the primary nucleons are calculated and a Monte Carlo simulation is used to account for final state interactions. The shape of the proton spectrum is sensitive to the value of {Gamma}{sub n}/{Gamma}{sub p} the ratio of neutron- to proton-induced decay, and the available experimental information favors larger values than those predicted by the one-pion-exchange model. From the spectra we calculate the number of neutrons (N{sub n}) and protons (N{sub p}) per {Lambda} decay and show how the measurement of these qua…
Conversion-electron study of 0+excitations in208Pb
2005
The 208Pb(p,p'e−) reaction has been studied at a proton energy of 17.3 MeV. Singles data show E0 transitions from the 0+2 and 0+3 states at 4868 and 5241 keV, respectively, to the ground state. Proton–electron gated spectra indicate that few electrons from the 0+2 state are in coincidence with backscattered protons, while those from the 0+3 state are somewhat more abundant. From the singles spectra, an upper limit for the E3(0+3 → 3−1)/E0(0+3 → 0+1) branching ratio of less than four has been measured. This observation is in agreement with previous predictions for a two-phonon octupole excitation.
Neutron yields from a thick 13C target irradiated by 30 MeV protons
2002
Abstract Total neutron yields resulting from the proton bombardment of a thick 13 C target have been measured for 30 MeV protons. Absolute intensities, angular distributions and energy spectra of neutrons have been obtained by the time-of-flight technique where the detectors provided continuous coverage from 0° to 120°. Resonances have been found, some of which can be attributed to known states in 14 N. A total yield of 0.022(3) n/p was observed with a slight angular anisotropy towards forward angles. The measured yields are compared to the neutron yields produced by using deuterons on thick 12 C and 9 Be targets.
Two-proton decay of the isobaric analogue state of Ar-31
1998
8 pages, 1 table, 4 figures.-- Journal issue title: "Nucleus-Nucleus Collisions".