CBMRelativistiv heavy-ion physics at FAIR

V. FrieseGesellschaft für Schwerionenforschung

Darmstadt, Germanyv.friese@gsi.de

The QCD phase diagram : From theory to experimentInternational Symposium, Skopelos, May 2004

2 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

The future at GSI : FAIR

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 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

Design Goals

Higher beam energies: 35 AGeV for heavy ions, 45 AGeV for light ions Highest beam intensities : 109 U / s continuous, 1012 U pulsed Excellent beam quality Parallel operation for different physics programmes :

Particle physicscharm spectroscopy, glueballs

Nucleus-nucleus collisionsQCD phase diagram, compressed baryonic matter

Nuclear structurenuclei far from stability, nucleosynthesis

Plasma physicsbulk high-density matter, inertial fusion

Atomic physicshigh precision studies of QED in extremely strong fields

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Parallel operation

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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

6 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

Timescale

7 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

Bad prospects for the trees...

8 Int. Symposium "The QCD phase diagram", Skopelos, May 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

... reaching deconfinement ?

... close to the critical point ?

9 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

What do we know : Strangeness production

Sharp structure in strangeness to pion ratio at low SPS energiesFailure of thermal models ?

A. Andronic, p. Braun-Munzinger, hep-ph/0402291

10 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

What do we know : Reaction volume

volume extracted from pion HBTexhibits non-monotonic behaviour

CERES, PRL 90(2003) 022301

11 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

What do we know: Fluctuations

•dynamical fuctuations reported by NA49•increase towards low energies•K/ : not reproduced by UrQMD•p/ : correlation due to resonance decays

NA49, nucl-ex/0403035

12 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

What we do know : Low-mass dileptons

are enhanced more at 40 AGeVthan at 158 AGeV

in-medium ρ could explain the enhancement

measurements need to be refined and carried out at lower energies

CERES, PRL91 (2003) 042301

13 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

What we do not know: Charm production near threshold

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

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What we do not know: 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

15 Int. Symposium "The QCD phase diagram", Skopelos, May 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

16 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

1. Indications for deconfinement at high B enhanced strangeness production ? K, , , , charm production ? J/, D softening of EOS measure flow excitation function 2. In-medium modifications of hadrons onset of chiral symmetry restoration at high B

, , e+e- open charm 3. Critical point event-by-event fluctuations

Physcis Topics and Observables

17 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

The good...

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!

...the bad...

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...and the ugly

Au+Au @ 25 AGeV

W. Cassing et al, Nucl. Phys. A 691(2001) 753

Rare probes in a heavy-ion environement:charged muliplicity ≈ 1000D multiplicity 10-4 – 10-3

need : high event rateshighly selective trigger

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central Au+Au @ 25 AGeV, UrQMD + GEANT

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

Need fast and radiation hard detectors

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The CBM detector : a strawman concept

Setup in GEANT4

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Tracking System

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

Solution for outer stations:fast strip detectors

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Trackingreconstructed tracks

Reconstruction efficiency > 95 %Momentum resolution ≈ 0.6 %Event pile-up in first tracking

stations (MAPS) not yet solved

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Hadron identificationσTOF = 80 ps

Bulk of kaons (protons) can well be identified with σTOF = 80 – 100 ps

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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)

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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

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TRD

Wire chamber readout studied at GSIrequires small drift times thin layers more layers

Pion efficiency of < 1% reachable with 9 layers

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RICH

Duties• e/ separation• K/ separation ?

vertical plane

horizontal plane

Optical layout for RICH1

Mirror: Beryllium / glassTwo focal planes (3.6 m2) separated vertically

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RICH

Radiator gas: C4H10 + N2 (thr = 16 – 41)

Photodetectors: photomultipliers or gas detectors

RICH1: thr = 41 p,thr = 5.7 GeV (almost) hadron blind

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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

30 Int. Symposium "The QCD phase diagram", Skopelos, May 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.

31 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

Feasibility study : open charmKey variable to suppress background: secondary vertex position

D0 K-+ (central Au+Au @ 25 AGeV)

Assuming <D0> = 10-3 :

S/B 1detection rate 13,000 / h

Similar studies for D+ K- + + ,D*±→D0 ± under way

Crucial detector parameters: Material in tracking stationsSingle hit resolution

32 Int. Symposium "The QCD phase diagram", Skopelos, May 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

33 Int. Symposium "The QCD phase diagram", Skopelos, May 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

34 Int. Symposium "The QCD phase diagram", Skopelos, May 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

35 Int. Symposium "The QCD phase diagram", Skopelos, May 2004 V. Friese

CBM : Status / Outlook

• CBM collaboration is formed: 250 scientists from 39 institutions

• CDR : November 2001, LoI : January 2004

• Work in progress: Detector design and optimisation

R&D on detetcor components

Feasibility studies of key observables

• Next step: Technical Proposal January 2005

• Could run in 2012!