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CBMThe future of relativistiv heavy-ion physics at GSI
V. FrieseGesellschaft für Schwerionenforschung
Darmstadt, [email protected]
Tracing the Onset of Deconfinement in Nucleus-Nucleus CollisionsTrento Workshop April 2004
2 Deconfinement Workshop, Trento, April 2004 V. Friese
The planned facility in Darmstadt
SIS 100/300
Unilac SIS
HESR
NESR
SuperFRS
A "next generation" accelerator facility:
Double-ring synchrotron 1100 m circumference
100 / 300 Tm
Cooler/Storage rings(CR, NESR, HESR)
Experimental areas for: nuclear structure plasma physics antiproton physics nuclear collisions atomic physics
Existing facility serves as injector
3 Deconfinement Workshop, Trento, April 2004 V. Friese
Design Goals
Highest beam intensities Excellent beam quality
4 Deconfinement Workshop, Trento, April 2004 V. Friese
Design Goals (2)
Parallel operation for different physics programmes
5 Deconfinement Workshop, Trento, April 2004 V. Friese
Design goals (3)
Higher beam energies
Heavy-ion beams 2 – 35 AGeV
Slow extraction, continuous beam
1010 ions/s up to Uranium
Light ions (Z/A=1) up to 45 AGeV
6 Deconfinement Workshop, Trento, April 2004 V. Friese
Project Status
November 2001 Conceptual Design ReportCost estimate 675 M €
July 2002 German Wissenschaftsrat recommendsrealisation
February 2003 German Federal Gouvernment decides to build the facility.Will pay 75 %
January / April 2004 Letters of Intent submitted
7 Deconfinement Workshop, Trento, April 2004 V. Friese
Timescale
8 Deconfinement Workshop, Trento, April 2004 V. Friese
The Times they are a' changing
9 Deconfinement Workshop, Trento, April 2004 V. Friese
The Future GSI and the QCD Phase Diagram
nuclei
hadronic phase
SPS
RHIC
SIS300
lattice QCD : Fodor / Katz, Nucl. Phys. A 715 (2003) 319
dilute hadron gasdense bayonic medium
... operating at highest baryon densities
... maybe reaching deconfinement
... maybe close to the critical point
10 Deconfinement Workshop, Trento, April 2004 V. Friese
Why another experiment?
We have data from AGS ( - 12 AGeV) and SPS (20 AGeV - )
but : studying the dense hadronic phase requires penetrating probes:
dileptons studying the onset of deconfinement requires systematic (energy,
system size) measurements of hadronic observables
The qualitatively new feature of the future accelerator:
Highest beam intensities (109 ions/s) give access to rare probes (ρ,dileptons, Ω, D, J/Ψ)
11 Deconfinement Workshop, Trento, April 2004 V. Friese
1. In-medium modifications of hadrons onset of chiral symmetry restoration at high B
measure: , , e+e- open charm (D mesons) 2. Indications for deconfinement at high B enhanced strangeness production ? measure: K, , , , charm production ? measure: J/, D softening of EOS measure flow excitation function 3. Critical point event-by-event fluctuations 4. Color superconductivity precursor effects at T>Tc ?
Physcis Topics and Observables
12 Deconfinement Workshop, Trento, April 2004 V. Friese
A physics example : Charm production
Hadron gas in chemical equilibriumCanonical suppression analoguous to strangeness
Equilibrated QGP+ statistical coalescence
Gorenstein et alJ. Phys. G 28 (2002) 2151
Predictions of open charm yield differby orders of magnitude for differentproduction scenarios, especially at lowenergies
Soft A dependence : <D> ~ <h-> ~ Np
pQCD : <D> ~ A2 ~ Np4/3
13 Deconfinement Workshop, Trento, April 2004 V. Friese
Open charm in dense matter
Various QCD inspired models predict a change of D mass in hadronic medium
Mishra et al, nucl-th/0308082
Substantial change (several 100 MeV) already at =0
In analogy to kaon mass modification, but drop for both D+ and D-
Effect for charmonium is substantially smaller
14 Deconfinement Workshop, Trento, April 2004 V. Friese
Reduced D meson mass : consequences
If the D mass is reduced in the medium: DD threshold drops below charmonium states
Mishra et al, nucl-th/0308082
Decay channels into DD open for ’, c, J/ broadening of charmonium states suppression of J/ enhancement of D mesons
HSD : D yield enhanced by a factor of 7 at 25 AGeV!
Cassing et al, Nucl. Phys. A 691 (2001) 753
15 Deconfinement Workshop, Trento, April 2004 V. Friese
Caveats and Advantages
Only one slot for relativistiv nuclear collisions at future GSI
Build an "universal experiment" for both hadronic and leptonic probes, covering as many obervables as possible
High beam intensity, quality and duty cycleHigh availability due to parallel operation of accelerator
Possibility of systematic measurements:beam energy (10 – 35/45 AGeV)system sizeeven of very rare probes!
16 Deconfinement Workshop, Trento, April 2004 V. Friese
Challenges : rare probes in heavy-ion environment
Au+Au @ 25 AGeV
W. Cassing et al, Nucl. Phys. A 691(2001) 753
charge muliplicity ≈ 1000
D multiplicity 10-4 – 10-3
need : high event rateshighly selective trigger
17 Deconfinement Workshop, Trento, April 2004 V. Friese
Conditions and requirements
High track multiplicity (700-1000)Beam intensity 109 ions/sec.High interaction rate (10 MHz)
Detector tasks:Tracking in high-density environment STS + TRDReconstruction of secondary vertices (resolution 50 m) STSHadron identification : / K / p separation (t 80 ps) TOFLepton identification : / e separation (pion suppression 10-4) TRD + RICHMyon / photon measurements ECAL
central Au+Au @ 25 AGeV, UrQMD + GEANT
Need fast and radiation hard detectors
18 Deconfinement Workshop, Trento, April 2004 V. Friese
The CBM detector
Setup in GEANT4
19 Deconfinement Workshop, Trento, April 2004 V. Friese
Tracking System
Radiation hard Silicon pixel/strip detectors
magnet
Requirements: Radiation hardnessLow material budgetFast detector responseGood positon resolution
Monolothic Active Pixel Sensors
Pitch 20 m
Low material budget : Potentially d = 20 m
Excellent single hit resolution : 3 m
S/N = 20 - 40
20 Deconfinement Workshop, Trento, April 2004 V. Friese
Trackingreconstructed tracks
Reconstruction efficiency > 95 %Momentum resolution ≈ 0.6 %
21 Deconfinement Workshop, Trento, April 2004 V. Friese
Hadron identification
σTOF = 80 ps
Bulk of kaons (protons) can well be identified with σTOF = 80 – 100 ps
22 Deconfinement Workshop, Trento, April 2004 V. Friese
RPC developments for TOF
90 cm-14 strips-4 gaps
t < 80 ps
Tail < 2%
Detector resolution
R&D FOPI Upgrade
Challenge for TOF :Huge counting rate (25 kHz/cm2)Large area (130 m2 @ 10 m)
23 Deconfinement Workshop, Trento, April 2004 V. Friese
TRD
Duties• e/ separation• tracking
Requirements• hit rate up to 500 kHz per cell• fast readout (10 MHz)
Anticipated setup• 9 layers in three stations (z = 4m / 6m / 8m)• area per layer 25 / 50 / 100 m2
• channels per layer 35 k / 55 k / 100 k
Readout options : drift chamber / GEM / straw tubes
For most of the system state-of-the art (ALICE) is appropriate.For the inner part, R&D on fast gas detectors in progress
24 Deconfinement Workshop, Trento, April 2004 V. Friese
TRD
Wire chamber readout studied at GSIrequires small drift times thin layers more layers
Pion efficiency of < 1% reachable with 9 layers
extrapolated from single ALICE-type chamber
25 Deconfinement Workshop, Trento, April 2004 V. Friese
RICH
Duties• e/ separation• K/ separation ?
vertical plane
horizontal plane
Optical layout for RICH1
Mirror: Beryllium / glassTwo focal planes (3.6 m2) separated vertically
26 Deconfinement Workshop, Trento, April 2004 V. Friese
RICH
Radiator gas: C4H10 + N2 (thr = 16 – 41)
Photodetectors: photomultipliers or gas detectors
RICH1: thr = 41 p,thr = 5.7 GeV (almost) hadron blind
27 Deconfinement Workshop, Trento, April 2004 V. Friese
RICH
Option for RICH2 ?thr = 30 p,thr = 4.2 GeV, pK,thr=15 GeV
Problem: Ring finding in high hit density environment
Kaon ID by RICH for p > 4 GeV would be desirable
Kaon ID by TOF deteriotes quickly above 4 GeV
28 Deconfinement Workshop, Trento, April 2004 V. Friese
DAQ / Trigger Architecture
clock
Practically unlimited size
Max. latency uncriticalAvr. latency relevant
Detector
Front endADC
Buffer memory
Event builderand selector
Self triggered digitization: Dead time free
Each hit transported asAddress/Timestap/Value
Compensates builder/selector latency
Use time correlation of hits to define events.Select and archive.
Challenge : reconstruct 1.5 x 109 track/sec.data volume in 1st level trigger 50 Gbytes/sec.
29 Deconfinement Workshop, Trento, April 2004 V. Friese
Feasibility study : open charm
Key variable to suppress background: secondary vertex position
D0 K-+ (central Au+Au @ 25 AGeV)
c = 124 m, BR = 3.8 %BG suppression 2 x 105
Assuming <D0> = 10-3 :
S/B 1SNR = 3 at 2 x 106 eventsdetection rate 13,000 / h
Similar study for D+ K- + + (c = 315 m, BR = 9 %)
First estimate S/B 3
Crucial detector parameters: Material in tracking stationsSingle hit resolution
30 Deconfinement Workshop, Trento, April 2004 V. Friese
Feasibility study: J/ e+e-
Extremely rare signal!Background from various sources: Dalitz, conversion, open charm...Very efficient cut on single electron pT
S/B > 1 should be feasible
31 Deconfinement Workshop, Trento, April 2004 V. Friese
Feasibility study : Light vector mesons
Background sources: Dalitz, conversionno easy pT cut; sophisticated cutting strategy necessarydepends crucially on elimination of conversion pairs by trackingand charged pion discrimination by RICH and TRD (104)
S/B = 0.3 (ρ+)S/B = 1.2 ()
idealised: no momentum resolution
32 Deconfinement Workshop, Trento, April 2004 V. Friese
Croatia: RBI, Zagreb
Cyprus: Nikosia Univ. Czech Republic:Czech Acad. Science, RezTechn. Univ. Prague France: IReS Strasbourg
Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. Mannheim Univ. MarburgUniv. MünsterFZ RossendorfFZ JülichGSI Darmstadt
Russia:CKBM, St. PetersburgIHEP ProtvinoINR TroitzkITEP MoscowKRI, St. PetersburgKurchatov Inst., MoscowLHE, JINR DubnaLPP, JINR DubnaLIT, JINR DubnaObninsk State UniversityPNPI St. PetersburgSINP, Moscow State Univ.
Spain: Santiago de Compostela Univ. Ukraine: Shevshenko Univ. , KievUniversity of Kharkov
USA: LBNL Berkeley
Hungaria:KFKI BudapestEötvös Univ. Budapest
Italy: INFN CataniaINFN Frascati
Korea:Korea Univ. SeoulPusan Univ.
NorwayUniv. of Bergen
Poland:Krakow Univ.Warsaw Univ.Silesia Univ. Katowice Portugal: LIP Coimbra
Romania: NIPNE Bucharest
The CBM Collaboration
33 Deconfinement Workshop, Trento, April 2004 V. Friese
Summary
• CBM will operate at the future facility from 2012 on
• It will measure nucleus-nucleus collisions from 10 – 35 / 45 AGeV at interaction rates of 10 MHz
• The key observables will be rare probes like multiple strange hyperons, open and hidden charm and dileptonic decays of light vector mesons
• These will (hopefully) give insight into the properties of baryonic matter at extreme densities and into the transition to a deconfined state
• (Still) open for new ideas!
• The collaboration has been formed; detector R&D is started or starting
• CDR : November 2001, LoI : January 2004
• Next milestone: Progress Report 2004 / 2005