simulation of a general purpose detector for the hesr project at gsi darmstadt conceptual design...
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Simulation of a general purpose detector for the HESR project at GSI Darmstadt
Conceptual Design Report:http://www.gsi.de/GSI-Future
V.Hejny* for the Antiproton Physics Study Group*Institut für Kernphysik, Forschungszentrum Jülich
• Why experiments with antiproton beams ?
• High Energy Storage Ring
• Overview of the detector system
• Simulation methods (Geant4, Pluto, Root)
• Simulation results
• Future tasks
DPG Meeting Münster, 13.03.2002
Why antiprotons ?
Strong interaction in the subnuclear regime: Quantum Chromodynamics (QCD)• high energies s << 1: perturbative QCD• low energies, hadrons s 1: non-perturbative QCD
“the hadron”
Open questions:• quark confinement• masses of strong interacting complex systems• firm establishment of hybrids and glueballs• …
pp – annihilation:(at 1.5 – 15 GeV/c)
• particle – antiparticle production (qq, hyperon – antihyperon, …)• strange and charm quarks interpolates between the extreme QCD limits (s 0.3, relativistic effects small)• gluonic degrees of freedom produced with high probability (ref. LEAR/CERN)
DPG Meeting Münster, 13.03.2002
Physics program
Structure of hadrons / interaction with nuclear matter Charmonium spectroscopy Poster HK 12.4
direct formation of all cc states, resolution given by beam Charmed hybrids and glueballs Poster HK 12.6
high probabilty for gluonic states in pp annihilation Charmed mesons in matter Poster HK 12.1
extension of the existing programs (,K) to the charm sector (D, J/, …) Hypernuclear physics Poster HK 12.7
hypernuclear states, medium effects, properties of hyperons Further options: Poster HK 12.5
• CP violation in the DD system and in hyperon decays• Rare decays of D-mesons
DPG Meeting Münster, 13.03.2002
GSI Future & HESR
High Energy Storage Ring (HESR):
Momentum range 1.5 – 15 GeV/cMomentum spread 10-4
(with electron cooling < 8GeV/c: 10-5)Beam diameter 100 mAntiprotons stored in ring 5 x 1010
Luminosity (pellet target) 2 x 1032 cm-2s-1
Integrated luminosity 10 pb-1/day
DPG Meeting Münster, 13.03.2002
Detector properties
Basic request: Build a modular, multi-purpose spectrometer for neutral and charged particle detection over the relevant angular (4?) andmomentum range (<1 GeV/c up to 10 GeV/c ?).
Demands: rate capability 2 x 107 annihilations/s
particle discrimination , e, , , K, p
vertex reconstruction for D, K0s, ( 100 m)
momentum reconstruction p/p 1 – 2 %
total pp cross section 100 mb
reaction cross sections nb range and smaller
various trigger conditions (e+e-), (), (+ -), (), (KK) ,…
DPG Meeting Münster, 13.03.2002
Simulation scheme:
Tools: ROOT for data handling and analysis http://root.cern.ch
PLUTO++ for event generation (ROOT library) http://www-hades.gsi.de/computing
phase space / exp. distributions for certain reactionsread in by Geant4 or processed directly in ROOT
Geant4 for detailed detector simulations http://geant4.web.cern.ch/geant4
currently used version: 4.4.0linked with ROOT to use ROOT file I/O
PLUTO++in ROOT
eventgeneration
(into ROOT files)
Detector simulationin Geant4
fast simulationin ROOT
Analysisin ROOT
direct outputinto ROOT files
results
DPG Meeting Münster, 13.03.2002
Detector components (a second view):
target spectrometer forward spectrometer
micro vertexdetector
electromagneticcalorimeter
DIRC:Detecting InternallyReflectedCherenkov light
straw tubetracker
mini driftchambers
muon counter
superconductivecoil
iron yoke
DPG Meeting Münster, 13.03.2002
Detector components: MVD
7.2 mio. barrel pixels50 x 300 μm 2 mio. forward pixels
100 x 150 μm
50 mm 200 mm
Micro Vertex Detector:(as implemented in Geant4)
Number of layers 5 in barrel, 5 in endcap
Thickness (single layer) 200 m
Thickness (5 layers) 1.25% of X0
Resolution z 25 … 100 m
DPG Meeting Münster, 13.03.2002
Detector components: MVD
Demanded resolution: 100 m
Simulation results:D0) = 51 m Z0) = 82 m
tracky
x
z
D0Z0
Matches resolution for D, K0s, identification !
DPG Meeting Münster, 13.03.2002
Detector components: STT
MVD
DIRC
STT
Straw Tube Tracker:
Number of double layers 15
Skew angle of layer 1 and 15 0°
Skew angle of layers 2-14 2°-3°
Straw tube wall thickness 26 m
Wire thickness 20 m
Gas 90:10 He and C4H10
Length 150 cm
Tube diameters (1-5, 6-10, 11-15) 4, 6, 8 mm
Total number of tubes 8734
Transverse resolution 150 m
Longitudinal resolution 1 mm
example event: pp 4K
DPG Meeting Münster, 13.03.2002
Detector components: MDC
Number of cathode planes 2 chambers x 3 layers x 2 planes
Orientation of wire planes 0°, 60°, 120°
Signal wire thickness 25 m
Field wire thickness 100 m
Cell size 1 cm x 1cm, i.e. 7000 channels
Gas 90:10 He and C4H10
Mini Drift Chamber:
Resolution: 150 m
DPG Meeting Münster, 13.03.2002
Overall performance
Track and momentumresolution:
Vertex resolution 50 – 80 m
Momentum resolution (TS) 1 – 2 %
pp J/ + (s = 4.4 GeV/c2):
J/ +- +-
(J/ = 35 MeV/c2
( = 3.8 MeV/c2
DPG Meeting Münster, 13.03.2002
Detector components: DIRC
Existing DIRC:BaBar @ SLAC
DIRC: Detecting Internally Reflected Cherenkov light
working scheme:
Angle coverage 22° - 140°
Quartz thickness and length 1.7 cm / 150 cm
Sensors Gas chambers with multi-pad readout
particle
lightcone
focal planewith light
sensors
quartz slab
DPG Meeting Münster, 13.03.2002
Detector components: DIRC
Particle identification: • reconstruction of light cone• momentum reconstruction used:
a) determination of the orientation of the light coneb) calculation of particle mass from and p
K eff.
miss-id.
reaction pp at s = 3.6 GeV/c2 “the real picture”
DPG Meeting Münster, 13.03.2002
Detector components: EMC
Electromagneticcalorimeter:
Detector material PbWO4
Photo sensors Avalanche Photo Diodes
Crystal size 35 x 35 x 150 mm3 (i.e 1.5 x 1.5 RM2 x 17 X0)
Decay constant < 20 ns
Energy resolution 1.54 % / E[GeV] + 0.3 %
Time resolution 130 ps
Total number of crystals 7150
Solid angle coverage 96 % x 4
barrel
backwardendcap
forwardendcap
DPG Meeting Münster, 13.03.2002
Detector components: EMC
Invariant mass resolution:
e/ particle discrimination:
Reaction:pp J/ + (s = 4.4 GeV/c2)
m() = 0.501 GeV/c2
() = 0.020 GeV/c2
DPG Meeting Münster, 13.03.2002
Detector components: Muon counter
Moun counter:
Position Outside of iron yoke
Covered angle 30° - 80°, = 360°
Bar thickness 2 cm
Detector performance:
identification
misidentification
DPG Meeting Münster, 13.03.2002
Overall performance
Reconstruction of a secondary vertex:
pp +-K0sK0
s
3+ 3-
Total acceptance:(geometry x detection eff. x reconstruction)
pp J/ + X
(s = 4.4 GeV/c2)
J/ +-J/ e+e-
suppressing of combinatorical background by momentum conservation:
primaryvertex secondary
vertex
(K0
s = 3 MeV/c2
DPG Meeting Münster, 13.03.2002
Summary and Outlook
Current status:• A general purpose detector for antiproton physics has to be designed for the
GSI Future Project• Simulations are performed in a framework of Geant4, ROOT and PLUTO++• The solenoid part (target spectrometer) is nearly fully implemented• Results show that the current design meets the requirements
Future tasks:• Completion of the detector implementation in Geant4 (forward spectrometer)• Setting up an easy-to-handle analysis framework for the simulation results• Intensive background simulations: Total annihilation cross section is 200 mb, typical reaction cross section is
in the order of nb for each valid event 108 events have to be simulated to prove
background suppression hardly to be handled by Geant4 fully ROOT based, fast simulation is in preparation
Workshop on experiments with antiprotons at the GSI future facilityApril 5 to 6, 2002 at GSI
(further information: http://www-wnt.gsi.de/pbar)
DPG Meeting Münster, 13.03.2002
Antiproton Physics Study Group
T. Barnes8, D. Bettoni6, R. Calabrese6, W. Cassing5, M. Düren5, S. Ganzuhr1, A. Gillitzer7, O. Hartmann2, V. Hejny7, P. Kienle9, H. Koch1, W. Kühn5, U. Lynen2, R. Meier11, V. Metag5, P. Moskal7, H. Orth2, S. Paul9, K. Peters1, J. Pochodzalla10, J. Ritman5, M. Sapozhnikov3, L. Schmitt9, C. Schwarz2, K. Seth4, N. Vlassov3, W. Weise9, U. Wiedner12
1 Experimentalphysik I, Bochum 2 GSI, Darmstadt 3 JINR, Dubna 4 Northwestern University, Evanston 5 Universität Gießen 6 INFN, Ferrara 7 Institut für Kernphysik, FZ Jülich 8 University of Tennessee, Knoxville 9 Technische Universität München10 Institut für Kernphysik, Mainz11 Physikalisches Institut, Tübingen12 ISV, Uppsala
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