34083016
The n_TOF Total Absorption Calorimeter for neutron capture measurements at CERN
The n_TOF Collaboration has built and commissioned a high-performance detector for (n, gamma) measurements called the Total Absorption Calorimeter (TAC). The TAC was especially designed for measuring neutron capture cross-sections of low-mass and/or radioactive samples with the accuracy required for nuclear technology and stellar nucleosynthesis. We present a detailed description of the TAC and discuss its overall performance in terms of energy and time resolution, background discrimination, detection efficiency and neutron sensitivity.
42512324
Charge-Changing Interaction of Ultrarelativistic Pb Nuclei
We present experimental results of nuclear-charge changing interactions for 158A-GeV ultrarelativistic In ions in Si, Ge, Sn, W, and Pb targets. Calculations based on the abrasion-ablation model for hadronic interaction and the RELDIS model for electromagnetic dissociation are compared to the data.
118535533
New description of the doublet bands in doubly odd nuclei
The experimentally observed {delta}I=1 doublet bands in some odd-odd nuclei are analyzed within the orthosymplectic extension of the interacting vector boson model (IVBM). A new, purely collective interpretation of these bands is given on the basis of the obtained boson-fermion dynamical symmetry of the model. It is illustrated by its application to three odd-odd nuclei from the A{approx}130 region, namely {sup 126}Pr, {sup 134}Pr, and {sup 132}La. The theoretical predictions for the energy levels of the doublet bands as well as E2 and M1 transition probabilities between the states of the yrast band in the last two nuclei are compared with experiment and the results of other theoretical approaches. The obtained results reveal the applicability of the orthosymplectic extension of the IVBM.
2076925
PT symmetry breaking and explicit expressions for the pseudo-norm in the Scarf II potential
Closed expressions are derived for the pseudo-norm, norm and orthogonality relations for arbitrary bound states of the PT symmetric and the Hermitian Scarf II potential for the first time. The pseudo-norm is found to have indefinite sign in general. Some aspects of the spontaneous breakdown of PT symmetry are analyzed.
1115406
Spin formalism in the algebraic scattering theory for heavy ions.
We develop a simple method of treating spin effects in the frame of algebraic scattering theory and apply it to the system {sup 16}O+{sup 65}Cu at {ital E}{sub c.m.}=44.77 MeV.
120041897
Level densities of transitional Sm nuclei
Experimentally determined level densities of the transitional isotopes $^{148,149,150,152}\mathrm{Sm}$ at excitation energies below and around the neutron binding energy are compared with microcanonical calculations based on a Monte Carlo approach to noncollective level densities, folded with a collective enhancement estimated in the frame of the interacting boson model (IBM). The IBM parameters are adjusted so as to reproduce the low-lying discrete levels of both parities, with the exception of the odd-mass nucleus, $^{149}\mathrm{Sm}$, where complete decoupling of the unpaired neutron from the core is assumed.
120940806
The muon high level trigger of the ATLAS experiment
The ATLAS experiment at CERN's Large Hadron Collider (LHC) has been designed and built for new discoveries in High Energy Physics as well as for precision measurements of Standard Model parameters. To satisfy the limited data acquisition and recording capability, at the LHC project luminosity, the ATLAS trigger system must select a very small rate of physically interesting events (~200 Hz) among about 40 million events per second. In the case of events containing muons, as described in this work, the first hardware-based level (Level-1) starts from coincidence of hits in the Muon Spectrometer trigger chambers to select Regions of Interest (RoI) where muons produce significant activity. Such RoIs are used as seeds for the two subsequent trigger levels (Level-2 and Event Filter), running on dedicated online farms, which constitute the High Level Trigger (HLT). This seeding strategy is crucial to drastically reduce the total processing time. Within the Muon HLT, few algorithms are implemented in different steps according to predefined sequences of Feature Extraction (FEX) and Hypothesis (HYPO) algorithms, whose goal is to validate the previously selected muon objects. The ATLAS muon trigger system, thanks to its particular design and to the peculiar structure of the Muon Spectrometer, is able to provide muon stand-alone event trigger decisions, that can be furtherly refined by exploiting the muon information coming from the other ATLAS subdetectors. Muon HLT algorithms are described here in terms of working functionality and performance both on simulated and real data, including non-standard trigger configurations (like cosmic data and LHC start-up scenarios).
122706822
Neutralino spin measurement with ATLAS
One of the goals of the ATLAS experiment at the LHC is to search for evidence of Supersymmetry (SUSY) signals and to measure, if discovered, the main properties of the new particles, like the spin. Left-handed squark cascade decay to second lightest neutralino (~ 0 ) which further decays to slepton represents a good opportunity for SUSY particles’ spin measurement. The observability of charge asymmetries in invariant mass distributions of some final products is investigated to prove that neutralino spin is 1/2. The criteria used to select signal events and to reject background are described, together with the applied cut efficiencies. Results on charge asymmetry are then shown and discussed.
51843235
The ATLAS Data Acquisition and Trigger: concept, design and status
This article presents the base-line design and implementation of the ATLAS Trigger and Data Acquisition system, in particular the Data Flow and High Level Trigger components. The status of the installation and commissioning of the system is also presented.
116941153
Beyond Standard Model and Exotics: Experimental overview
22148204
Implementation and performance of the third level muon trigger of the ATLAS experiment at LHC
The trigger system of the ATLAS experiment at the LHC aims at a high selectivity in order to keep the full physics potential while reducing the 40 MHz initial event rate imposed by the LHC bunch crossing down to /spl sim/100 Hz, as required by the data acquisition system. Algorithms working in the final stage of the trigger environment (Event Filter) are implemented to run both in a "wrapped" mode (reconstructing tracks in the entire Muon Spectrometer) and in a "seeded" mode (according to a dedicated strategy that performs pattern recognition only in regions of the detector where trigger hypotheses have been produced at earlier stages). The working principles of the offline muon reconstruction and identification algorithms (MOORE and MuId) implemented and used in the framework of the Event Filter are discussed in this paper. The reconstruction performance of these algorithms is presented for both modes in terms of efficiency, momentum resolution, rejection power and execution times on several samples of simulated single muon events, also taking into account the high background environment expected for ATLAS.