the c ompressed b aryonic m atter experiment

The Compressed Baryonic Matter experiment

Claudia Höhne, GSI Darmstadt

CBM collaboration

Outline

• physics case, observables

• detector layout

• feasibility studies

• (R&D of detector components)

2 Claudia Höhne Schleching 2007

CBM @ FAIR


Physics case

Q: Why do we want to build yet another heavy-ion experiment?

What do we know from theory? → Predictions from lattice QCD:

• crossover transition from partonic to hadronic matter at small B and high T

• critical endpoint in intermediate range of the phase diagram

• first order deconfinement phase transition at high B but moderate T


Physics case (II)

What do we know from experiment? → Heavy-ion collisions:

• chemical freeze-out curve

• top SPS, RHIC (high T, low B):

partonic degrees of freedom ?

• lower SPS, AGS (intermediate T-B):

intriguing observations around 30 AGeV!

[Andronic et al. Nucl. Phys. A 772, 167 (2006).


Physics case (III)

CBM@FAIR – high B, moderate T:

searching for the landmarks of the QCD phase diagram• first order deconfinement phase transition • chiral phase transition• QCD critical endpoint

in A+A collisions from 10-45 AGeV (√sNN = 4.5 – 9.3 GeV) starting in 2015



Dense baryonic matter

• baryon density in central cell (Au+Au, b=0 fm) in transport calculations HSD (mean field, hadrons + resonances + strings)

• enormous energy and baryon densities reached! ( > crit ~ 1GeV/fm3)

[CB

M p

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cs g

rou

p, C

. F

uchs

, E

. B

ratk

ovsk

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priv

. co

m.]

Q: Do we reach energy densities high and long enough in order to reach a deconfined phase?


High baryon density matter!

[Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/9909229] [Mishra et al ., PRC 69, 015202 (2004) ]

• hadronic properties should be effected by the enormous baryon densities

• relation to (partial) restoration of chiral symmetry?

• equation of state?

D

Q: Why do we want to measure particles also at high baryon densities?


Physics topics and Observables

The equation-of-state at high B

• collective flow of hadrons • particle production at threshold energies (open charm)

Q: How to measure? What to look for?

Grig

orian, Blaschke, K

lähn

astro-ph/0612783

side remark:equation of state at high baryon densities → relation to inner core of neutron stars!


D-mesons in matter[W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745]

SIS18 SIS100/ 300

D-mesons sensitive to medium (EOS)!

[Mishra

et al ., PR

C 69, 01520

2 (2004)]


D-mesons in matter (II)

[E.

Bra

tkov

skay

a, W

. C

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ng,

priv

ate

com

mu

nica

tion]

• charm production studies at threshold: steeply rising cross section

• dropping D-meson mass might give a large enhancement

• measure energy dependence!

• impact on flow!

charm quark as probe for dense matter created at FAIR



Deconfinement phase transition at high B • excitation function and flow of strangeness (K, , , , ) • excitation function and flow of charm (J/ψ, ψ', D0, D, c)• sequential melting of J/ψ and ψ', charmonium suppression


• collective flow of hadrons• particle production at threshold energies (open charm)



Excitation function

NN

NN

NNN ss

msF

41

43

2

For (K, , , , ,..........) measure with high precision

• particle production

• kinetic distributions

• flow

• correlations

• .......

in dependence on energy, system-size (centrality),...

→ observe changes?

in ideal case for several observables at the same energy

[NA49]

QGP

hadron gas

transition


elliptic flow v2:

initial overlap eccentricity → particle azimuthal distributions

Collective flow

• collapse of elliptic flow of protons at lower energies signal for first order phase transition?! [e.g. Stoecker, NPA 750 (2005) 121, E. Shuryak, hep-ph/0504048]

• full energy dependence needed!

central

midcentral

peripheral [NA49, PRC68, 034903 (2003)]

v2


RHIC

• all particles flow: strong collective behaviour!

• impressive scaling of flow observed

relation to quark content of hadrons!

→ partonic degrees of freedom relevant in early phase!

• when does it break down?

Collective flow (II)

KET=mT-m


Collective flow (III)

• does charm flow at all energies?

• break down of charm flow?

charm quark as probe for dense matter created at FAIR


Charmonium suppression

cc production

• at threshold for CBM energies!

• cc produced in first inelastic interactions

• pp: certain probability to form a J/ (or ')

• AA: dissolved in medium?

... difference for J/ and '?

(sequential melting?)

Quarkonium dissociation temperatures – Digal, Karsch, Satz

measure energy and system-size dependence!



Deconfinement phase transition at high B • excitation function and flow of strangeness (K, , , , )• excitation function and flow of charm (J/ψ, ψ', D0, D, c)• sequential melting of J/ψ and ψ', charmonium suppression



QCD critical endpoint• excitation function of event-by-event fluctuations (K/π,...)



Fluctuations

• difficulty: subtract all "trivial" fluctuations (statistical, acceptance, other correlations,...)

• dynamical fluctuations of the K/ ratio increase towards lower energies

[C.Roland et al., nucl-ex/0403035

S. Das, SQM06]

22mixeddatadyn

K/

energy dependence needed for lower energies (and a better understanding)!



Onset of chiral symmetry restoration at high B

• in-medium modifications of hadrons (,, e+e-(μ+μ-), D)







Dileptons

pn

++

K

p

e+, μ+

e-, μ-

Dileptons are penetrating probes!

lifetime of -meson 1.3 fm/c → probe the early fireball!

(c of : – 23 fm/c, – 44 fm/c, J/ – 2.3 fm/c)


Dileptons (II)

hep-ph/0604269

• new results from top SPS energy (√sNN = 17.3 GeV):

→ modification of spectral function, importance of baryons!

CERES NA60

• measure in dependence on baryon density (energy)!


Dileptons (III)

Q: What is the best way to measure? e+e- ↔ +-



Onset of chiral symmetry restoration at high B

• in-medium modifications of hadrons (,, e+e-(μ+μ-), D)





CBM Physics Book (theory) in preparation



The CBM experiment• tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field

• electron ID: RICH & TRD suppression 104

• hadron ID: TOF (& RICH)

• photons, 0, : ECAL

• PSD for event characterization

• high speed DAQ and trigger

STS

high interaction rate

long beamtime

→ rare probes!


Modified CBM setup → dimuons• for investigation of dimuons study alternative CBM setup with active muon absorbers (Fe + C + detector layers) after the STS

• ... move absorbers out for hadron runs


Dileptons - electrons

• low-mass vector mesons: try to reject large physical background (-conversion, Dalitz decays) by high performance tracking

• J/: cut on pt (1.2GeV)

• high purity of electron identification needed!

S/B=1.7eff. 12%

J/ mesonlow-mass vector mesons

S/B = 0.2eff. 7.5%

central Au+Au, 25 AGeV


Dileptons - muons

• low efficiency for soft muons → use momentum dependent identification?

• phantastic J/, even ' should be accessible

• however:high hit densities in detectors!

J/ mesonlow-mass vector mesons

S/B = 0.42eff. 1.8%

S/B ~ 30eff. 13%



STS tracking

Challenge: high track density 600 charged particles in 25o

task

• track reconstruction:

0.1 GeV/c < p 10-12 GeV/c

p/p ~ 1% (p=1 GeV/c)

• primary and secondary vertex reconstruction (resolution 50 m)

• V0 track pattern recognition

D+ → ++K- (c = 317 m)

D0 → K-+ (c = 124 m)


Open charm production• D0 → K-+ (c= 124 m)

• <D0> = 4∙ 10-5 → ~ 2 D0/s for 1MHz interaction rate (minbias Au+Au)

• first MAPS detector at 10cm

• ~53 m secondary vertex resolution

• proton identification via TOF

• even better signal for D+ → K-++

(3-particle 2nd vertex)

1.6 107 central Au+Au collisions, 25 AGeV



CBM collaboration

Russia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg

China:CCNU WuhanUSTC Hefei

Croatia: RBI, Zagreb

Portugal: LIP Coimbra

Romania: NIPNE Bucharest

Poland:Krakow Univ.Warsaw Univ.Silesia Univ. KatowiceNucl. Phys. Inst. Krakow

LIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.

Ukraine: Shevchenko Univ. , Kiev

Cyprus: Nikosia Univ.

Univ. Mannheim Univ. MünsterFZ RossendorfGSI Darmstadt

Czech Republic:CAS, RezTechn. Univ. Prague

France: IPHC Strasbourg

Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. Kaiserslautern

Hungaria:KFKI BudapestEötvös Univ. Budapest

India:VECC KolkataSAHA KolkataIOP BhubaneswarUniv. ChandigarhUniv. VaranasiIlT Kharagpur

Korea:Korea Univ. SeoulPusan National Univ.

Norway:Univ. Bergen

Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR Dubna

46 institutions

> 400 members

Strasbourg, September 2006


Physics case

CBM@FAIR – high B, moderate T:

searching for the landmarks of the QCD phase diagram• first order deconfinement phase transition • chiral phase transition• QCD critical endpoint

in A+A collisions from 10-45 AGeV (√sNN = 4.5 – 9.3 GeV) starting in 2015



additional slides


CbmRoot simulation framework• detector simulation (GEANT3)

• full event reconstruction: track reconstruction, add RICH, TRD and TOF info

• result from feasibility studies in the following: central Au+Au collisions at 25 AGeV beam energy


STS tracking (II)• set of silicon tracking stations inside magnetic field („heart of CBM“)

• MVD for high precision vertex resolution

• Si strip for main tracker

• challenge: readout speed (10 MHz interaction rate), radiation hardness (109 ions/s), material budget, resolution

• layout simulations

• Si-strip sensor design

• system integration

• fast self-triggered readout


STS R&D

4"280 µm

Microstrip Sensors Tracking Stations

layout studies

module design


fast self-triggered readout electronics

NXYTER chip produced; DETNI − GSI

test system under construction

micro-strip sensor


Hadron identification – TOF (RPC)

simulations: time resolution 80ps, TOF wall in 10m distance to target


D-mesons in matter[W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745]

SIS18

[M. Lutz, Phys. Lett. B 426, 12 (1998)]

us repulsive potential

us attractive potential


Sequential dissociation of charmonium?

Quarkonium dissociation temperatures – Digal, Karsch, Satz

(J/)/DY = 29.2 2.3L = 3.4 fm

Preliminary! Preliminary!

[NA60]


Fluctuations (II)However ....

• mean-pt (pT) fluctuations rather constant

• changing fluctuations of net electric charge dyn?

importance of resonance decays?!

[CERES, NPA 727, 97 (2003)][H. Appelshaeuser and H. Sako for CERES, nucl-ex/0409022]

the c ompressed b aryonic m atter experiment

Documents

fair claudia hhne schleching

fair high mb

energy densities high

high baryon density

high baryon densities

rhic high t

high t critical endpoint

high b excitation function