Measurement of the K_1hn0 inclusive cross section in pion-induced reactions at 1.15 GeV-c [Elektronische Ressource] / presented by Mohamed Lotfi Benabderrahmane

English
146 Pages
Read an excerpt
Gain access to the library to view online
Learn more

Description

Dissertationsubmitted to theCombined Faculties for the Natural Sciences and for Mathematicsof the Ruperto-Carola University of Heidelberg, Germanyfor the degree ofDoctor of Natural Sciencespresented byMSc Mohamed Lotfi Benabderrahmaneborn in Mila, AlgeriaOral examination: 18th April, 20070Measurement of the K Inclusive Cross Sectionin Pion-Induced Reactions at 1.15GeV/cReferees: Prof. Dr. Norbert HerrmannProf. Dr. Johanna Stachel0The K production cross section and the phase-space distributions were mea-−sured in the reaction + nucleus at an incident momentum of 1.15 GeV/c for C,0Al, Cu, Sn and Pb. For the first time the system-size (A) dependence of the K2/3production cross section has been measured and shows an A dependence. The0experimental ratio of the K momentum distribution produced in Lead to that inCarbon shows a suppression at low momenta. A comparison to the corresponding+ratio of K measured in proton-induced reactions shows a good agreement, which0indicates the sensitivity of this observable to the K N potential. Comparisons toHSD transport model calculations show that this model is not able to describe0momentum and rapidity distributions of the K as well as the behaviour of the in-0clusive cross section as a function of A. Microscopic calculations of the K crosssection in nuclear matter including the KN potential in the final state interactionare in good agreement with the measurements.

Subjects

Informations

Published by
Published 01 January 2007
Reads 21
Language English
Document size 2 MB
Report a problem

Dissertation
submitted to the
Combined Faculties for the Natural Sciences and for Mathematics
of the Ruperto-Carola University of Heidelberg, Germany
for the degree of
Doctor of Natural Sciences
presented by
MSc Mohamed Lotfi Benabderrahmane
born in Mila, Algeria
Oral examination: 18th April, 20070Measurement of the K Inclusive Cross Section
in Pion-Induced Reactions at 1.15GeV/c
Referees: Prof. Dr. Norbert Herrmann
Prof. Dr. Johanna Stachel0The K production cross section and the phase-space distributions were mea-
−sured in the reaction + nucleus at an incident momentum of 1.15 GeV/c for C,
0Al, Cu, Sn and Pb. For the first time the system-size (A) dependence of the K
2/3production cross section has been measured and shows an A dependence. The
0experimental ratio of the K momentum distribution produced in Lead to that in
Carbon shows a suppression at low momenta. A comparison to the corresponding
+ratio of K measured in proton-induced reactions shows a good agreement, which
0indicates the sensitivity of this observable to the K N potential. Comparisons to
HSD transport model calculations show that this model is not able to describe
0momentum and rapidity distributions of the K as well as the behaviour of the in-
0clusive cross section as a function of A. Microscopic calculations of the K cross
section in nuclear matter including the KN potential in the final state interaction
are in good agreement with the measurements.
0Der Wirkungsquerschnitt der K -Produktion und dessen Phasenraumverteilun-
−gen wurden in -Kern-Reaktionen bei einem Pion-Impuls von 1.15 GeV/c fu¨r
0C-, Al-, Cu-, Sn- und Pb-Kerne untersucht. Die Abha¨ngigkeit des K -Produktions-
wirkungsquerschnitts von der Systemgro¨ße A wurde zum ersten Mal gemessen
2/3und eine A -Abha¨ngigkeit wurde beobachtet. Das experimentell bestimmte
0Verha¨ltnis der K -Impulsverteilungen in Blei zu denen in Kohlenstoff ist fu¨r nie-
drige Impulse stark unterdru¨ckt. Ein Vergleich mit dem entsprechenden Verha¨lt-
+ ¨nis fu¨r K aus Proton-Kern-Reaktionen zeigt eine gute Ubereinstimmung, daher
ist diese Observable geeignet zur Untersuchung des KN-Potentials. Vergleiche
mit Berechnungen des HSD-Transportmodells verdeutlichen, dass dieses Mod-
0ell bisher noch nicht in der Lage ist, Impuls- und Rapidita¨tsverteilungen des K ,
0sowie die Abha¨ngigkeit der Inklusiven K -Produktion von der Systemgro¨ße zu
0beschreiben. Berechnungen des K -Produktionswirkungsquerschnitts im Rah-
men eines mikroskopischen Modells, welches ein KN-Potential fu¨r die Wech-
selwirkungen in Endzustand beeinhaltet, stimmen gut mit den Messergebnissen
u¨berein.
ppContents
Overview 1
1 Introduction 3
1.1 Properties of Nuclear Matter . . . . . . . . . . . . . . . . . . . . 3
1.1.1 The Phase Diagram . . . . . . . . . . . . . . . . . . . . . 4
1.1.2 The Equation of State (EOS) . . . . . . . . . . . . . . . . 5
1.2 Hadrons in Nuclear Matter . . . . . . . . . . . . . . . . . . . . . 7
1.3 Kaon Properties in Heavy-Ion Collisions . . . . . . . . . . . . . . 10
1.4 Kaon Production in proton-induced Reactions . . . . . . . . . . . 14
1.5 Kaon Production in pion-induced Reactions . . . . . . . . . . . . 16
2 The FOPI Detector and the S273 Experiment 21
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2 The secondary Pion Beam at GSI . . . . . . . . . . . . . . . . . . 21
2.2.1 The Pion Beam Experiment with FOPI . . . . . . . . . . 22
2.3 Target Properties of the S273 Experiment . . . . . . . . . . . . . 23
2.4 The Start Counter . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.5 The Veto Detector (Halo) . . . . . . . . . . . . . . . . . . . . . . 25
2.6 The Beam Scintillator Detector . . . . . . . . . . . . . . . . . . . 25
2.7 The Central Drift Chamber (CDC) . . . . . . . . . . . . . . . . . 25
2.7.1 The Mechanical Design . . . . . . . . . . . . . . . . . . 26
2.7.2 Observables measured by the CDC . . . . . . . . . . . . 26
2.7.3 The Calibration of the CDC . . . . . . . . . . . . . . . . 29
2.7.4 The z Coordinate Calibration . . . . . . . . . . . . . . . . 31
2.7.5 The Energy-Loss Calibration . . . . . . . . . . . . . . . . 33
2.8 The Scintillator Barrel . . . . . . . . . . . . . . . . . . . . . . . 34
2.9 The Helitron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.10 The Forward Wall . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.10.1 The Plastic Wall (PLAWA) . . . . . . . . . . . . . . . . . 37
2.10.2 The Zero Degree Detector . . . . . . . . . . . . . . . . . 37
2.11 The Silicon Strip Detector (SDD) . . . . . . . . . . . . . . . . . . 37
I2.12 Determination of the Cross Section . . . . . . . . . . . . . . . . . 38
3 Data Analysis 41
3.1 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.1.1 Rejection of non-target Reactions . . . . . . . . . . . . . 41
3.2 Detector Acceptance . . . . . . . . . . . . . . . . . . . . . . . . 43
3.3 Particle Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 45
03.4 Reconstruction Methods of V . . . . . . . . . . . . . . . . . . . 47
03.4.1 Invariant Mass Spectra of K and . . . . . . . . . . . . 48S
03.4.2 Reconstruction in the Forward Wall (PLAWA) . . . . . 57
4 GEANT Simulation 63
4.1 The CDC Digitizer . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2 Drift Path of a Hit . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3 Modeling of the Gain . . . . . . . . . . . . . . . . . . . . . . . . 66
4.4 Energy and z Resolutions of a Hit . . . . . . . . . . . . . . . . . 67
4.5 Position Resolution of Hits in the(x,y) Plane . . . . . . . . . . . 70
4.6 Momentum Resolution . . . . . . . . . . . . . . . . . . . . . . . 71
4.7 Efficiency Evaluation . . . . . . . . . . . . . . . . . . . . . . . . 72
4.7.1 Global Efficiency Estimation . . . . . . . . . . . . . . . . 72
4.7.2 Local Efficiency Evaluation . . . . . . . . . . . . . . . . 76
5 Experimental results 81
05.1 K Phase-Space Distributions . . . . . . . . . . . . . . . . . . . . 81S
05.2 K Invariant Production Cross Section . . . . . . . . . . . . . . . 83
05.3 K Rapidity Distributions . . . . . . . . . . . . . . . . . . . . . . 84
05.4 The K Inclusive Cross Section . . . . . . . . . . . . . . . . . . . 86
05.5 Inclusive Momentum Spectra of K in Pb and C . . . . . . . . . . 89
5.6 Systematic Error Evaluation . . . . . . . . . . . . . . . . . . . . 92
6 Model Comparisons 97
6.1 Invariant Cross Section . . . . . . . . . . . . . . . . . . . . . . . 98
06.2 K Rescattering in HSD . . . . . . . . . . . . . . . . . . . . . . . 100
6.3 Rapidity Distributions . . . . . . . . . . . . . . . . . . . . . . . . 101
6.4 Momentum Spectra . . . . . . . . . . . . . . . . . . . . . . . . . 102
6.5 Ratio of the Momentum Distributions . . . . . . . . . . . . . . . 103
06.6 K Inclusive Cross Section . . . . . . . . . . . . . . . . . . . . . 106
7 Summary and Outlook 109
A The Bethe-Bloch Formula 113
II
LLB Kinematical Variables and Invariant Cross Section 115
B.1 Particle Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
B.1.1 Golden Rule for Scattering . . . . . . . . . . . . . . . . . 116
Bibliography 119
Aknowledgments 129
IIIIV