Search results for "Monte Carlo method."
showing 10 items of 1217 documents
New model and code for calculation of product yields in fusion-fission reactions
2003
A new version of the theoretical model and computing code for calculations of the pre- and post-scission light particle spectra and multiplicity distributions, the evaporation residue cross sections, and the fission product yield cross sections has been developed. The most important dynamical effects (nuclear friction and light particle emission at the descent from saddle to scission point) in the decay of heated rotating compound nuclei were included in consideration [1]. The fission characteristics have been calculated for every compound nucleus at excitation energy and angular momentum at the scission point. The contributions from different fission modes including the superasymmetric one…
Measurements of Higher Order Flow Harmonics inAu+AuCollisions atsNN=200 GeV
2011
Flow coefficients nu(n) for n = 2, 3, 4, characterizing the anisotropic collective flow in Au + Au collisions at root s(NN) = 200 GeV, are measured relative to event planes Psi(n), determined at large rapidity. We report nu(n) as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The nu(n) are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted …
A large area detector for high-energy neutrons
1992
Abstract We present design studies, results of test measurements, and Monte Carlo simulations which served as a basis for the realization of a large area neutron detector (LAND). It has a front area of 2m×2m and a depth of 1 m, and features a multilayer structure of passive converter and active scintillator material. The detector is subdivided in independently operating paddles which allow time-of-flight and position measurement. An energy resolution of ΔT n / T n =5.3% for a flight path of 15 m and an overall detection efficiency of ϵ ≈ 1 is anticipated for neutrons with T n ≈ 1 GeV. The operation of LAND at the SIS facility of GSI is described.
Non-mesonic weak decay of A hypernuclei
1998
Abstract The non-mesonic decay modes of Λ hypernuclei are examined. The one-nucleon induced decay (ΛN → NN) is studied in a shell-model framework using a meson-exchange picture. The total decay rates and parity-violating asymmetries reproduce the available experimental data. However, the model does not yet explain the partial rates and the resulting neutron- to proton-induced ratio Γ n /Γ p . The two-nucleon-induced decay rate (ΛNN -> NNN) is evaluated using the propagator formalism and the local-density approximation and is found to contribute about 15% to the total decay width of medium to heavy hypernuclei. The influence of this channel on the experimental determination of the ratio Γ n …
Hypernuclear physics at $\overline{\mbox{P}}$ ANDA
2012
Hypernuclear research will be one of the main topics addressed by the \(\overline{\mbox{P}}\) anda experiment at the planned Facility for Anti-proton and Ion Research FAIR at Darmstadt, Germany. A copious production of Ξ-hyperons at a dedicated internal target in the stored anti-proton beam is expected, which will enable the high-precision γ-spectroscopy of double strange systems for the first time. In addition to the general purpose \(\overline{\mbox{P}}\) anda setup, the hypernuclear experiments require an active secondary target of silicon layers and absorber material as well as high purity germanium (HPGe) crystals as γ-detectors. The design of the setup and the development of these det…
Inclusive B ¯ → X s ℓ + ℓ − $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ : complete angular analysis and a thorough study of collinear photons
2015
We investigate logarithmically enhanced electromagnetic corrections of all angular observables in inclusive $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ . We present analytical results, which are supplemented by a dedicated Monte Carlo study on the treatment of collinear photons in order to determine the size of the electromagnetic logarithms. We then give the Standard Model predictions of all observables, considering all available NNLO QCD, NLO QED and power corrections, and investigate their sensitivity to New Physics. Since the structure of the double differential decay rate is modified in the presence of QED corrections, we also propose new observables which vanish if only QCD correc…
Measurement of photon showers in lead produced by electrons of 150 MeV
1976
Abstract The photon energy spectra induced by 150 MeV electrons in lead were measured in the energy range from 40 MeV up to the primary electron energy. The target thickness was varied between 0.1 and 2.5 radiation lengths X 0 . The photons were analyzed by use of a technique based on deuteron photodisintegration. Differential and integral shower spectra are presented and compared with Monte Carlo calculations of Nagel and Messel et al., both interpolated to our primary energy of 150 MeV. The measured spectra show good agreement with these Monte Carlo calculations for the thickest target of 2.5 X 0 and with calculated bremsstrahlung spectra for the thinnest target of 0.1 X 0 . Considerable …
The Distribution of Slowing-Down Times of Positrons Emitted from <sup>22</sup>Na and <sup>68</sup>Ge\<sup>68</sup>…
2010
The results of the Monte Carlo simulation, using GEANT4 codes, of the slowing-down time prior to the thermalization in metals for positrons emitted from the 22Na and 68Ge\68Ga sources are presented. Due to the energy spectrum and probabilistic processes accompanying positrons traversing a medium the slowing-down time exhibits a distribution which has a long tail. Nevertheless, the average value of the time is ranged from 0.4 ps to 8 ps depending on the density of the medium as it is for the 22Na positrons. For positrons emitted from the 68Ga nucleus the average value of the slowing-down time increases and it is ranged from 1 ps to 20 ps.
Pathlength dependence of energy loss within in-medium showers
2010
Studying the pathlength dependence of high P_T hadron suppression in heavy-ion collisions by measuring the dependence of hard hadron production on the angle phi with the reaction plane in non-central collisions has so far been one of the most successful tools in constraining the microscopical picture of leading parton energy loss. With the imminent start of the LHC heavy-ion program and the possibility of full jet reconstruction, the focus has shifted to models which are capable of simulating full in-medium parton showers rather than tracing the leading parton only. Yet, on the level of single inclusive hadron observables, such shower models need to reproduce the findings of leading parton …
Inclusive Nucleon Emission Induced by Quasi--Elastic Neutrino--Nucleus Interactions
2005
We study the quasi--elastic contribution to the inclusive $(\nu_l,\nu_l N)$, $(\nu_l,l^- N)$, $({\bar \nu}_l,{\bar \nu}_l N)$ and $({\bar \nu}_l,l^+ N)$ reactions in nuclei using a Monte Carlo simulation method to account for the rescattering of the outgoing nucleon. As input, we take the reaction probability from the microscopical many body framework developed in Phys. Rev. {\bf C70} (2004) 055503 for charged-current induced reactions, while for neutral currents we use results from a natural extension of the model described in that reference. The nucleon emission process studied here is a clear signal for neutral--current neutrino driven reactions, that can be used in the analysis of futur…