CBM The future of relativistiv heavy-ion physics at GSI

CBMThe future of relativistiv heavy-ion physics at GSI

V. FrieseGesellschaft für Schwerionenforschung

Darmstadt, Germanyv.friese@gsi.de

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

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Design Goals

Highest beam intensities Excellent beam quality

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Design Goals (2)

Parallel operation for different physics programmes

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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

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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

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Timescale

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The Times they are a' changing

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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

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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)

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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

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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

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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

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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

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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!

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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

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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

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The CBM detector

Setup in GEANT4

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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

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Trackingreconstructed tracks

Reconstruction efficiency > 95 %Momentum resolution ≈ 0.6 %

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Hadron identification

σTOF = 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

extrapolated from single ALICE-type chamber

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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

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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.

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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

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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

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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

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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

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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