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Analysis of electron pair production in the collision system Ar+KCl at 1.76 AGeV; Analyse der Elektronpaarproduktion im Stosssystem Ar+KCl bei 1,76 AGeV

Abstract

The HADES-spectrometer at GSI is used to measure the production of the light vector mesons {rho}, {omega} and {phi} at SIS energies. Therefore, the medium sized collision system Ar+KCl was measured at 1.76 AGeV kinetic energy of beam particles. In this system the density of particle tracks is much larger as compared to the formerly used collision system C+C, making it necessary to upgrade the data analysis. The previous method of hard-cuts - used for particle identification - was replaced by a newly developed multi-variate analysis based on an artificial neural network. This algorithm has the benefit, that it is more robust against fluctuations in one or more of the used detector observables. This increases the overall efficiency and purity of the analysis procedure. Furthermore, the reconstruction of particle tracks inside the HADES spectrometer is based on a few position information, only. During analysis of raw data, these information are combined to a artificially large manifold of tracks. This leads to the general problem that one has to select the maximum number of true physical tracks out of this set of tracks per event. A new method of track selection is used to filter the data not only to select  More>>
Publication Date:
Jun 30, 2008
Product Type:
Thesis/Dissertation
Report Number:
INIS-DE-0727
Resource Relation:
Other Information: TH: Diss. (Dr.rer.nat.)
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; PARTICLE TRACKS; PARTICLE DISCRIMINATION; NEURAL NETWORKS; ALGORITHMS; ELECTRONS; MASS SPECTRA; EFFECTIVE MASS; PAIR PRODUCTION; ARGON 40 REACTIONS; POTASSIUM 39 TARGET; CHLORINE 35 TARGET; RELATIVISTIC RANGE; GEV RANGE 10-100; POSITRONS; DATA ANALYSIS; MULTIVARIATE ANALYSIS; MASS SPECTROSCOPY; ELECTRON DETECTION; POSITRON DETECTION
OSTI ID:
21197603
Research Organizations:
Frankfurt Univ. (Germany). Fachbereich 13 - Physik
Country of Origin:
Germany
Language:
German
Other Identifying Numbers:
TRN: DE09F8323
Availability:
Commercial reproduction prohibited; INIS; OSTI as DE21197603
Submitting Site:
DEN
Size:
128 pages
Announcement Date:
Aug 21, 2009

Citation Formats

Lang, Simon Martin. Analysis of electron pair production in the collision system Ar+KCl at 1.76 AGeV; Analyse der Elektronpaarproduktion im Stosssystem Ar+KCl bei 1,76 AGeV. Germany: N. p., 2008. Web.
Lang, Simon Martin. Analysis of electron pair production in the collision system Ar+KCl at 1.76 AGeV; Analyse der Elektronpaarproduktion im Stosssystem Ar+KCl bei 1,76 AGeV. Germany.
Lang, Simon Martin. 2008. "Analysis of electron pair production in the collision system Ar+KCl at 1.76 AGeV; Analyse der Elektronpaarproduktion im Stosssystem Ar+KCl bei 1,76 AGeV." Germany.
@misc{etde_21197603,
title = {Analysis of electron pair production in the collision system Ar+KCl at 1.76 AGeV; Analyse der Elektronpaarproduktion im Stosssystem Ar+KCl bei 1,76 AGeV}
author = {Lang, Simon Martin}
abstractNote = {The HADES-spectrometer at GSI is used to measure the production of the light vector mesons {rho}, {omega} and {phi} at SIS energies. Therefore, the medium sized collision system Ar+KCl was measured at 1.76 AGeV kinetic energy of beam particles. In this system the density of particle tracks is much larger as compared to the formerly used collision system C+C, making it necessary to upgrade the data analysis. The previous method of hard-cuts - used for particle identification - was replaced by a newly developed multi-variate analysis based on an artificial neural network. This algorithm has the benefit, that it is more robust against fluctuations in one or more of the used detector observables. This increases the overall efficiency and purity of the analysis procedure. Furthermore, the reconstruction of particle tracks inside the HADES spectrometer is based on a few position information, only. During analysis of raw data, these information are combined to a artificially large manifold of tracks. This leads to the general problem that one has to select the maximum number of true physical tracks out of this set of tracks per event. A new method of track selection is used to filter the data not only to select single tracks, but also to identify electron pairs created during Dalitz-decay of {pi}{sup 0} mesons, which build the bulk of combinatorial background. The result of the analysis is an efficiency corrected invariant mass spectrum of electron pairs, normalized to the mean number of pions per event. The spectrum consists of more than 16,000 pairs with an invariant mass larger than 150 MeV. In total more than 150000 pairs were found. A first comparison with the spectra calculated by using the old analysis approach shows a 30% enhancement in yield of reconstructed electron pairs. A first comparison with a simple thermal model implemented by the Pluto event generator, opens the possibility to compare the measured pair yield of {omega} and {phi} mesons via m{sub T}-scaling with the yield of {eta} mesons found in other experiments. In this context an energy dependent enhancement of pair production F(1.76)=Y{sub total}/Y{sub PLUTO}=5.3 was found inside the mass region M=0.15..0.5 GeV/c{sup 2}. (orig.)}
place = {Germany}
year = {2008}
month = {Jun}
}