the cbm experiment at fair claudia höhne, gsi darmstadt cbm collaboration outline motivation,...

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The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline • motivation, physics case • observables • experiment • feasibility studies dileptons: e + e - + - ?

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Page 1: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

The CBM experiment at FAIR

Claudia Höhne, GSI Darmstadt

CBM collaboration

Outline

• motivation, physics case

• observables

• experiment

• feasibility studies

dileptons: e+e- ↔ +- ?

Page 2: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

2 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

CBM

• Compressed Baryonic Matter experiment

• SIS 300 → U92+ 15-35 GeV/nucleon with beam intensities up to 109/s

Z/A = 0.5 nuclei up to 45 GeV/nucleon

→ exploration of the QCD phase diagram with heavy-ion collisions!

→ investigation of nuclear matter at highest baryon densities but still moderate temperatures in A+A collisions

Page 3: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

3 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

• milestone in mapping the QCD phase diagram would be the (unambiguous) discovery of either the critical point or the 1st order phase transition

• top SPS, RHIC, LHC :

high T, low B region –

most probably crossover

• high B region !

onset of deconfinement?

1st order phase transition?

critical point?

high baryon density!

in medium modifications of hadrons

• lower SPS, AGS:

limited in observables, statistics

CBM – physics casecritica

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→ SIS 300 @ FAIR

2nd generation experiment! → charm, dileptons, fluctuations, correlations

Page 4: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

4 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dense baryonic matter

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

• enormous energy and baryon densities reached! ( > crit)

[CBM physics group, C. Fuchs priv. com.]

Page 5: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

5 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Phase diagram

[Bratkovskaya et al., PRC 69 (2004) 054907]

• UrQMD calculation of T, B as function of reaction time

(open symbols – nonequilibrium,

full symbols – appr. pressure equilibrium)

• phase border crossed already at rather low energies

(see also results from 3-fluid hydrodynamics)

• critical point in reach?

CBM energy range: 15 - 35 AGeV for Au+Au

Page 6: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

6 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

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 which will be created

• (partial) restoration of chiral symmetry?

D

Page 7: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

7 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Physics of CBM

physics topics

deconfinement at high B ?

softening of EOS ?

order of phase transition ?

Critical point ?

in-medium properties of hadrons

onset of chiral symmetry restoration at high B

observables

strangeness production: K,

charm production: J/, D

flow excitation function

event-by-event fluctuations

e+e-

open charm

CBM: rare probes → high interaction rates!

Page 8: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

8 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Strangeness productiondeconfinement

[NA49, C.Blume et al., nucl-ex/0409008]

• s-production mechanism different in hadronic / partonic scenario

• maximum of strangeness production at 30 AGeV

→ change from hadronic to partonic phase?

• CBM energy range: 15 – 35/45 AGeV (depending on A)

• verify and extend energy dependence!

Page 9: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

9 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Transverse-mass spectra

seen for pions, kaons, protons and their antiparticles

filled symbol: particleopen symbol: antiparticle

energy dependence of mt changes at lower SPS energies

deconfinement

Page 10: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

10 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

J/ suppression

• screening of cc pairs in partonic phase

• anomalous J/ suppression observed at top-SPS and RHIC energies

• signal of deconfinement?

• energy dependence?!

[E. Scomparin for NA 60, QM05]

deconfinement

Page 11: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

11 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

collective flow

• collapse 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)]

deconfinement

Page 12: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

12 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

K/ fluctuationsCritical point

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

• not reproduced by UrQMD: resonance contribution?

• acceptance effects?

Energy dependence needed also for lower energies!

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

S. Das, SQM06]

22mixeddatadyn

Page 13: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

13 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

In medium effects: Dileptons

[Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/9909229]

• dileptons are penetrating probes!

• modifications in hot and dense matter expected –

see CERES, NA50, NA60, HADES

best way to measure? e+e- ↔ +-

Page 14: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

14 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

modifications → l+l- In medium

within acceptance

• high quality data at low and high energies now coming in from NA60 (SPS, 158 AGeV, In+In) and HADES (SIS, 2 AGeV, C+C)

• enhancement of low-mass dilepton pairs!

[R. Holzmann for HADES, QM05][E. Scomparin for NA 60, QM05]

Page 15: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

15 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

modifications → e+e-

• intermediate energies with highest baryon densities?

• pioneering measurement of CERES

• study full energy dependence!

CERES [Phys. Rev. Lett. 91, 042301 (2003)]

In medium

Page 16: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

16 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

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

SIS18 SIS100/ 300

Consequences for charmonium states if DD threshold drops below their mass!

D-mesons sensitive to medium!

In medium[M

ishra et al .,

PR

C 69, 0152

02 (200

4) ]

Page 17: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

17 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

D-mesons (II)

[E. Bratkovskaya, W. Cassing, private communication]

In medium

• Dropping D-meson masses with increasing light quark density

might give a large enhancement of the open charm yield at 25 A GeV !

Page 18: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

18 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

detector requirements

Systematic investigations:A+A collisions from 8 to 45 (35) AGeV, Z/A=0.5 (0.4) (up to 8 AGeV: HADES)p+A and p+p collisions from 8 to 90 GeV

observables detector requirements & challenges

strangeness production: K,

charm production: J/, D

flow excitation function

event-by-event fluctuations

e+e-

open charm

tracking in high track density environment (~ 1000)

hadron ID

lepton ID

myons, photons

secondary vertex reconstruction

(resolution 50 m)

large statistics: large integrated luminosity:

high beam intensity (109 ions/sec.) and duty cycle

beam available for several months per year

high interaction rates (10 MHz)

fast, radiation hard detector

efficient trigger

rare signals!

Page 19: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

19 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

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

• electron ID: RICH & TRD (& ECAL) suppression 104

• hadron ID: TOF (& RICH)

• photons, 0, : ECAL

• high speed DAQ and trigger

• not necessarily fixed layout!

• more like „facility“

STS

Page 20: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

20 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

STS tracking

Challenge: high track density 600 charged particles in 25o

task

• track reconstruction for tracks with 0.1 GeV/c < p 10-12 GeV/c and with a momentum resolution of order 1% at 1 GeV/c

• primary and secondary vertex reconstruction (resolution 50 m)

• V0 track pattern recognition (hyperons, e+e- pairs from -conversion)

D+ → ++K- (c = 317 m)

D0 → K-+ (c = 124 m)

Page 21: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

21 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

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

• 2-3 vertex detectors with high resolution, minimum thickness (e.g. MAPS)• 2-3 pixel detectors for tracking seeds• outer stations: Si-strip

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

so far: simple standard layout with 7/8 stations (3 + 4)/ (2+2+4) in use

MAPSStripHybrids

Should deliver unambiguous seeds

High resolution tracking

With large coverage

Ultimate vertex resolution

optimization of layout is ongoing work

robust tracking!!

Page 22: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

22 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Open charm production• D0 → K-+ (c= 124 m), minimum bias Au+Au collisions at 25 AGeV

• <D0> = 4∙ 10-5

• ~50 m secondary vertex resolution

• proton identification via TOF

• even better signal for D+ → K-++

(3-particle 2nd vertex)

Page 23: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

23 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Hyperons• identification via 2nd vertices in the STS, no hadron ID• acceptance: (17 %), (6.5 %) (7.5 %)• current reconstruction efficiency: (56 %), (26 %) (36 %)→ optimize/ improve 2nd vertex finder, STS layout

= 0.85 MeV

Page 24: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

24 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Hadron identification – TOF (RPC)

• challenge: counting rate, large area, sufficient position resolution, time resolution < 80ps

• simulations: • central Au+Au at 25 AGeV, UrQMD• time resolution 80ps, TOF wall in 10m distance to target• no track reconstruction and mismatch yet!

Squared mass measured with TOF

Page 25: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

25 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dynamical fluctuations

4 acceptance identified

particles

K/ 3.2 0.3 2.6 0.6

p/ -5.3 0.07 -5.9 0.1

datamixed events

2 2dyn data mixed

• UrQMD: central Au+Au collisions at 25 AGeV, no track reconstruction

• resonance contribution?!

• little influence of limited detector acceptance

• lower detectable limit of dyn. fluctuations?

Page 26: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

26 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dileptons

• dileptons are penetrating probes!

• modifications in hot and dense matter expected –

see CERES, NA50, NA60, HADES

best way to measure? e+e- ↔ +-

Page 27: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

27 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-4

10-3

10-2

10-1

100

101

102

0.0 0.2 0.4 0.6 0.8 1.0 1.210-4

10-3

10-2

10-1

100

free in-medium

M [GeV/c2]

Au+Au->e+e-+X 25 A GeV, 5% central

dN/d

M [

1/(G

eV/c

2 )]

HSD

free in-medium

M [GeV/c2]

Au+Au->+-+X 25 A GeV, 5% central

dN/d

M [

1/(G

eV/c

2 )]Dileptons: electrons ↔ muons

0.0 0.2 0.4 0.6 0.8 1.0 1.2

10-4

10-3

10-2

10-1

100

101

102

0.0 0.2 0.4 0.6 0.8 1.0 1.210-4

10-3

10-2

10-1

100

free in-medium

M [GeV/c2]

Au+Au->e+e-+X 25 A GeV, 5% central

dN/d

M [

1/(G

eV/c

2 )]

HSD

free in-medium

M [GeV/c2]

Au+Au->+-+X 25 A GeV, 5% central

dN/d

M [

1/(G

eV/c

2 )]

HSD: in-medium modifications of low-mass vector mesons in e+e- channel and +- channel are very similar!

important: mass region from ~ 0.2 – 0.7 GeV/c2

(below under vivid discussion)

[E. Bratkovskaya, priv. com.]

Page 28: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

28 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Conceptional studies: MC tracks, ideal particle ID

Major background sources: π0 → γ e+e-, γ → e+e-

track segment

reconstructed no PID

reconstructed PID

no magnetic field constant magnetic field 7.5 kG

0 cm 15 cm 200 cm

Physical background: small pair opening angle often: one hard, one soft electron

Dileptons - electrons

N/event Decay BR

36 e+ e- 5.×10-3

38 e+ e- 0

e+ e-

5.9×10-4

7.07×10-5

1.28 e+ e- 3.1×10-4

0 28 e+ e- 4.44×10-5

Page 29: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

29 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dileptons - electrons• low-mass vector mesons: develop sophisticated cut strategy

→ (so far) signal quality mainly limited by ability of background rejection

• J/: cut on pt (1GeV) seems sufficient

• so far no track reconstruction, PID included

J/ψ→e+e-

central Au+Au, 25 AGeV

pt >100 MeV

φω

Page 30: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

30 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

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

Page 31: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

31 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dileptons - muonsfirst study:

• minimum bias Au+Au, 25 AGeV

• low efficiency for soft muons → early cutoff in invariant mass spectrum of low-mass vector mesons

• phantastic J/, even ' should be accessible

J/ψ→μ+μ-

ρ φω

Page 32: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

32 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dileptons – muons (II)

problems: low efficiency for soft muons!

→ accepted phase space shifted to forward rapidities for low-mass vector mesons

challenging muon detector (high particle densities!)

J/

Page 33: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

33 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

Dileptons – muons (III)ongoing simulations studies: momentum dependent muon identification

optimization of absorbers (material, thickness, position)

p = 3 GeV/c

p = 2 GeV/c

p = 0.5 GeV/c

p = 1 GeV/c

preliminary !

Page 34: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

34 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

CBM – summary • CBM offers a very interesting physics program studying the QCD phase-diagram

• unique features expected in CBM energy range: first order phase transition, critical point

• CBM as 2nd generation experiment will be able to study rare probes, fluctuations and correlations!

• detector development under way

• increasingly realistic feasibility studies are performed

→ Technical proposal ~ in 2007

Page 35: The CBM experiment at FAIR Claudia Höhne, GSI Darmstadt CBM collaboration Outline motivation, physics case observables experiment feasibility studies dileptons:

35 Claudia Höhne CBM meeting at VECC, India, Juy 21, 2006

CBM collaboration

Croatia: RBI, Zagreb

China:Wuhan Univ.Hefei Univ.

Cyprus: Nikosia Univ.  Czech Republic:CAS, RezTechn. Univ. Prague

France: IReS Strasbourg

Hungaria:KFKI BudapestEötvös Univ. Budapest

India:VECC KolkataIOP Bhubaneswar*Univ. Chandighar*Univ. Varanasi*

Korea:Korea Univ. SeoulPusan National Univ.

Norway:Univ. Bergen

Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. KaiserslauternUniv. Mannheim Univ. MünsterFZ RossendorfGSI Darmstadt

Poland:Krakow Univ.Warsaw Univ.Silesia Univ. KatowiceNucl. Phys. Inst. Krakow* Portugal: LIP Coimbra

Romania: NIPNE Bucharest

Russia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. PetersburgKurchatov Inst., MoscowLHE, JINR DubnaLPP, JINR DubnaLIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.

Ukraine: Shevshenko Univ. , Kiev

* to be approved by CB

CBM Collaboration : > 40 institutions, > 350 Members