Simulation of a general purpose detector for the HESR project at GSI Darmstadt Conceptual Design Report: V.Hejny* for the

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)


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


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


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) ,…


A (first) view of the detector


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


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


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


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 !


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


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


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


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


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”


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


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


Detector components: Muon counter

Moun counter:

Position Outside of iron yoke

Covered angle 30° - 80°, = 360°

Bar thickness 2 cm

Detector performance:

identification

misidentification


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


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)


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

Documents

Simulation of a general purpose detector for the HESR project at GSI Darmstadt Conceptual Design Report: V.Hejny* for the