13,841 research outputs found
SIMDET - Version 4 A Parametric Monte Carlo for a TESLA Detector
A new release of the parametric detector Monte Carlo program \verb+SIMDET+
(version 4.01) is now available. We describe the principles of operation and
the usage of this program to simulate the response of a detector for the TESLA
linear collider. The detector components are implemented according to the TESLA
Technical Design Report. All detector component responses are treated in a
realistic way using a parametrisation of results from the {\em ab initio} Monte
Carlo program \verb+BRAHMS+. Pattern recognition is emulated using a complete
cross reference between generated particles and detector response. Also, for
charged particles, the covariance matrix and information are made
available. An idealised energy flow algorithm defines the output of the
program, consisting of particles generically classified as electrons, photons,
muons, charged and neutral hadrons as well as unresolved clusters. The program
parameters adjustable by the user are described in detail. User hooks inside
the program and the output data structure are documented.Comment: 30 pages, 7 figure
Influence of electron-ion collisions on Coulomb crystallization of ultracold neutral plasmas
While ion heating by elastic electron-ion collisions may be neglected for a
description of the evolution of freely expanding ultracold neutral plasmas, the
situation is different in scenarios where the ions are laser-cooled during the
system evolution. We show that electron-ion collisions in laser-cooled plasmas
influence the ionic temperature, decreasing the degree of correlation
obtainable in such systems. However, taking into account the collisions
increases the ion temperature much less than what would be estimated based on
static plasma clouds neglecting the plasma expansion. The latter leads to both
adiabatic cooling of the ions as well as, more importantly, a rapid decrease of
the collisional heating rate
Dynamical Crystallization in the Dipole Blockade of Ultracold Atoms
We describe a method for controlling many-body states in extended ensembles
of Rydberg atoms, forming crystalline structures during laser excitation of a
frozen atomic gas. Specifically, we predict the existence of an excitation
number staircase in laser excitation of atomic ensembles into Rydberg states.
Each step corresponds to a crystalline state with a well-defined of regularly
spaced Rydberg atoms. We show that such states can be selectively excited by
chirped laser pulses. Finally, we demonstarte that, sing quantum state transfer
from atoms to light, such crystals can be used to create crystalline photonic
states and can be probed via photon correlation measurements
Charged Current Neutrino Nucleus Interactions at Intermediate Energies
We have developed a model to describe the interactions of neutrinos with
nucleons and nuclei, focusing on the region of the quasielastic and Delta(1232)
peaks. We describe neutrino nucleon collisions with a fully relativistic
formalism which incorporates state-of-the-art parametrizations of the form
factors for both the nucleon and the N-Delta transition. The model has then
been extended to finite nuclei, taking into account nuclear effects such as
Fermi motion, Pauli blocking (both within the local density approximation),
nuclear binding and final state interactions. The in-medium modification of the
Delta resonance due to Pauli blocking and collisional broadening have also been
included. Final state interactions are implemented by means of the
Boltzmann-Uehling-Uhlenbeck (BUU) coupled-channel transport model. Results for
charged current inclusive cross sections and exclusive channels as pion
production and nucleon knockout are presented and discussed.Comment: 26 pages, 24 figures; v2: 2 figures and discussion added, version
accepted for publication in Phys. Rev.
Relaxation to non-equilibrium in expanding ultracold neutral plasmas
We investigate the strongly correlated ion dynamics and the degree of
coupling achievable in the evolution of freely expanding ultracold neutral
plasmas. We demonstrate that the ionic Coulomb coupling parameter increases considerably in later stages of the expansion, reaching the
strongly coupled regime despite the well-known initial drop of
to order unity due to disorder-induced heating. Furthermore, we formulate a
suitable measure of correlation and show th at calculated from
the ionic temperature and density reflects the degree of order in the system if
it is sufficiently close to a quasisteady state. At later times, however, the
expansion of the plasma cloud becomes faster than the relaxation of
correlations, and the system does not reach thermodynamic equilibrium anymore
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