exploring the qcd phase diagram at high baryon densities: from sps to fair

Exploring the QCD Phase Diagram at High Baryon Densities: From SPS to FAIR

Claudia Höhne, GSI Darmstadt

• QCD phase diagram

• results from SPS and RHIC

• CBM physics topics and observables

feasibility studies and R&D

2 Claudia Höhne ISHIP 2008, GSI, November 2008

QCD phase diagram at high baryon densities

[F.Karsch, Z. Fodor, S.D.Katz]

• intermediate range of the QCD phase diagram with high net-baryon densities of strong interest because of

• expected structures as 1st order phase transition and critical point

• chiral phase transition

• deconfinement = chiral phase transition ?

• hadrons and quarks at high ?

• signatures (measurable!) for these structures/ phases?

• how to characterize the medium?


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

• chemical freeze-out curve

• top SPS, RHIC (high T, low B): partonic degrees of freedom, crossover (?)

• RHIC: first steps towards a quantitative characterization of the medium (gluon density, viscosity, energy loss...)

• lower SPS (intermediate T-B): intriguing observations around 30 AGeV!

• SIS, AGS: high density baryonic matter

QCD phase diagram & experiments

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


Within the next years we'll get a complete scan of the QCD phase diagram with 2nd generation experiments

• LHC, RHIC: bulk observables and rare probes (charm, dileptons)

• RHIC energy scan: bulk observables√s ~ (5)10 GeV – 200 GeV

• NA61: focus on fluctuations(√sNN = 4.5 – 17.3 GeV), A < 120

• NICA: strangeness, bulk observables (√sNN = 3 – 9 GeV)

• CBM: bulk observables and rare probes (charm, dileptons)beam energy 10 – 45 GeV/nucleon(√sNN = 4.5 – 9.3 GeV)

• HADES: bulk observables, dileptonsbeam energy 2 – 10 GeV/nucleon

Experimental scan of QCD phase diagram

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

HADES

CBM, NA61, NICA

LHCRHIC

FAIR beam intensities: up to 109 ions/s


SPS results

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

[NA49, PRC 77, 024903 (2008)]

• energy dedendence of hadron production→ changes in SPS energy regime

• discussions ongoing:• hadron gas → partonic phase • baryon dominated → meson dominated matter

• missing: high precision measurements, systematic investigations, correlations, rare probes→ quantitative characterization of the medium!


0SSppS

BBn

n

Statistical ModelF. Becattini et al., Phys. Rev. C73 (2006), 044905.

High net baryon densities at low SPS energies

BRAHMSPhys. Rev. Lett. 93 (2004), 102301

NA49 (158)Phys. Rev. Lett. 82 (1999), 2471

E802Phys. Rev. C 60 (1999), 064901

NA49 preliminary

Central Pb+Pb/Au+Au

[NA49, compilation C. Blume]• low SPS/ AGS energies: high net-baryon densities at mid-rapidity

• change to nearly net-baryon free region at RHIC

• change of shape most pronounced at SPS energies: peak → dip

construction of total net-baryon distribution:

Sx from stat. model fits


High net-baryon density matter at CBM

• high baryon and energy densities created in central Au+Au

• remarkable agreement between different models (not shown)

[CB

M p

hysi

cs g

rou

p, C

. F

uchs

, E

. B

ratk

ovsk

aya

priv

. co

m.]

beam energy

max. /0

max [GeV/fm3]

time span

~FWHM

5 AGeV 6 1.5 ~ 8 fm/c

40 AGeV 12 > 10 ~ 3.5 fm/c


Elliptic flow

KET=mT-m

• all particles flow (even D-mesons!)

• scaling if taking the underlying number of quarks into account!

→ like (all!) quarks flow and combine to hadrons at a later stage (hadronisation)

• data can only be explained assuming a large, early built up pressure in a nearly ideal liquid (low viscosity!)

baryons n=3mesons n=2

[PHENIX, PRL.98:162301,2007]

KE m m mT T T ( ) 1


Elliptic flow

• data at top SPS support hypothesis of early development of collectivity

• influence of hadronic rescattering phase, resonance decay?

• lack of complete thermalization, viscosity effect?

• larger pt-range needed

Pb+Pb collisions, √sNN = 17.3 GeV

[NA49, G. Stefanek, PoS CPOD2006:030,2006]


Elliptic flow

→ stiffness of medium (EOS), pressure

• collapse of elliptic flow of protons at lower energies signal for first order phase transition?!

central

midcentral

peripheral [NA49, PRC68, 034903 (2003)]

Elab ~ 30 AGeV

[Paech, Reiter, Dumitru, Stoecker, Greiner, NPA 681 (2001) 41]

?

particle identified flow data for large pt-range!


AMPT calculations: C.M. Ko at CPOD 2007

Elliptic flow at FAIR

... including charm!

probe for dense matter!


[A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel, arXiv:0708.1488]

Statistical hadronization model (SHM)(c-cbar in partonic phase)

O. Linnyk, E.L. Bratkovskaya, W. Cassing, H. Stöcker,Nucl.Phys.A786:183-200,2007

Hadronic model (HSD)

NN → D Λc NNN → DD NNNN → J/ψ NN

Charm production in hadronic and partonic matter


Charm production in hadronic and partonic matter

no charm (J/) data below 158 AGeV beam energy

detailed information including phase space distributions!


Critical point

• critical region might be small

• focussing effect?

• fluctuations would need time to develop

[Schaefer, Wambach, PRD75, 085015 (2007)] [Asakawa, Bass, Mueller, Nonaka, PRL 101, 122302 (2008)]


Event-by-event fluctuations

[NA49 collaboration, arXiv:0810.5580v2 [nucl-ex]]

• observation might become enormously difficult

• correlation length of sigma field, may become rather small for a finite lifetime of the fireball

• large acceptance needed!

2

2

pt

pt

pt zN

Z

N

ittipt

ttpt

ppZ

ppz

1

[Stephanov, Rajagopal, Shuryak, PRD60, 114028 (1999)]

1st try to identify 1st order phase transition line

fluctuations, correlations with large acceptance and particle identification


CBM: Physics topics and Observables

Onset of chiral symmetry restoration at high B

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

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)• charmonium suppression, sequential for J/ψ and ψ' ?

The equation-of-state at high B

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

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

predictions? clear signatures?→ prepare to measure "everything" including rare probes → systematic studies! (pp, pA, AA, energy)aim: probe & characterize the medium! - importance of rare probes!!


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

• hadron ID: TOF (& RICH)• photons, 0, : ECAL

• electron ID: RICH & TRD suppression 104

• PSD for event characterization• high speed DAQ and trigger → rare probes!

• muon ID: absorber + detector layer sandwich move out absorbers for hadron runs

RICHTRD

TOF ECAL

magnet

absorber +

detectorsSTS + MVD


STS tracking – heart of CBM

Challenge: high track density: 600 charged particles in 25o @ 10MHz

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

c = 312 m

radiation hard and fast silicon pixel and strip detectors

self triggered FEE

high speed DAQ and trigger

online track reconstruction!


• max: up to ~109 tracks/s in the silicon tracker (10 MHz, ~100 tracks/event)

• start scenario for D more like 0.1 MHz → 107 tracks/s

→ fast track reconstruction!

• optimize code, port C++ routines to dedicated hardware

• parallel processing → today: factor 120000 speedup of tracking code achieved!

• long term aim: make use of manycore architectures of new generation graphics cards etc.

Track reconstruction

GeForce 9600

64 core GPU


Double and triple GEM detectors2 Double-sided silicon microstrip detectors

Radiation tolerance studies for readout electronics Full readout and analysis

chain:

Front-end board with self-triggering

n-XYTER chip Readout controllerData Acquisition

System

online

offline

Go4

AnalysisDetector

signals

Successful test of CBM prototype detector systems with free-streaming read-out electronics using proton beams at GSI, September 28-30, 2008

GSI and AGH Krakow VECC Kolkata KIP Heidelberg


GSI, Darmstadt, GermanyJINR, Dubna, RussiaKIP, Heidelberg, GermanyVECC, Kolkata, IndiaAGH, Krakow, Poland

90Sr -spectra ...

Detector commissioning:

... in several channels of a silicon microstrip detector

... and in a GEM detector

Operation on the beam line:

Participants:

Beam spot seen on a GEM detector (every 2nd channel read out)

Correlation of fired channels in two silicon microstrip detectors

www-cbm.gsi.de


CBM hardware R&D

RICH mirror

n-XYTER FEB

Silicon microstrip detector

MVD: Cryogenic operation in vacuum RPC R&D

Forward Calorimeter

GEM

dipole magnet


Monolithic Acitive Pixel Sensors in commercial CMOS process1010 m2 pixels fabricated, > 99%, x ~ 1.5 – 2.5 m

Micro Vertex Detecor (MVD) DevelopmentArtistic view of the MVD

• mechanical system integration • material for cooling!→ material budget!• vacuum compatibility

die thinned to 50 mglued to support.IPHC, Strasbourg (M. Winter et al.)


D-meson Simulations• CbmRoot simulation framework, GEANT3 implemented through VMC

• full event reconstruction: track reconstruction, particle-ID (RICH, TRD, TOF), 2ndary vertex finder

• feasibility studies: central Au+Au collisions at 25 AGeV beam energy (UrQMD)

• several channels studied: D0, D±, Ds, c

signal multiplicities from HSD, stat model (SM); e.g. <D+>HSD = 8.410-5, SM ½ less

• important layout studies: MAPS position (5cm , 10cm), thickness (150 m – 500m)

D-

D+

MAPS thickness

D+

efficiency

D+

S/B (2)

150 m 4.2% 9

500 m 1.05% 1.9

D+ → ++K- (c = 312 m, BR 9%)D0 → K-+ (c = 123 m, BR 3.85%)c → pK-+ (c = 60 m, BR 5%)


CBM feasibility studies

• feasibility studies performed for all major channels including event reconstruction and semirealistic detector setup

D0

c

J/ J/

di-electrons di-muons

' '


b

p

p

Signal: strange dibaryon

(0)b (cτ=3cm)

M= 10-6, BR = 5%

Background:Au+Au @ 25 AGeV32 per central event11 reconstructable

π K p

χ2primary > 3()

Particle identification with CBM

KS0 Λ

Be prepared for exotica: multi-strange di-baryons


Detector layout optimization: RICH

• first ansatz: gaseous RICH detector (N2 radiator), ~ 100 m3 volume, 200k channels for photodetector (photomultiplier, pixel size appr. 6x6 mm2), Be mirrors (glass coating)

• optimization process: ~40 m3 volume, CO2 radiator, 55k channels, glass mirrors

RICH + TRD

75% efficiency104 suppression

photodetector:

H8500 MAPMT, UV glass window

15 – 22 hits/ring


Detector layout optimization: Muon absorber

40 20 20 20 25

30 20 20 20 35

20 20 20 30 35

10 20 30 30 35

central Au+Au collisions at 25 AGeV10 cm Fe

20 cm Fe

30 cm Fe

40 cm Fe

hit density after 1st absorber

total absorber length 125 cm = 7.5 I


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

→ systematic measurements, rare probes

• characterizing properties of baryon dense matter

• in medium properties of hadrons?

in A+A collisions from 10-45 AGeV (√sNN = 4.5 – 9.3 GeV) starting in 2016 at SIS 300

Summary – physics of CBM


CBM + HADES @ SIS 100 in 2014

Rigidity Bρ = 100 Tm:

Au beam 10 AGeVNi beam 14 AGeVp beam 30 GeV

HADES: electrons, hadrons

CBM "light" (magnet, Silicon tracker, TOF): p, K, π, Λ, Ξ, Ω, ..., flow, fluctuations, up to Au+Au


CBM @ SIS 100

• A+A collisions at 8 AGeV beam energy, p+A at 30 GeV/c

• first feasibility studies: charm production for p+C at 30 GeV/c

multiplicities from HSD

1012 events

J/→ +-

S/B ~150

23 %

4 J/ψ→μ+μ- in 109 central events


CBM collaborationRussia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg

China:Tsinghua Univ., BeijingCCNU WuhanUSTC Hefei

Croatia:

University of SplitRBI, Zagreb

Portugal: LIP Coimbra

Romania: NIPNE BucharestBucharest University

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: INR, KievShevchenko Univ. , Kiev

Univ. MannheimUniv. MünsterFZ RossendorfGSI Darmstadt

Czech Republic:CAS, RezTechn. Univ. Prague

France: IPHC StrasbourgGermany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. Frankfurt

Hungaria:KFKI BudapestEötvös Univ. BudapestIndia:Aligarh Muslim Univ., AligarhIOP BhubaneswarPanjab Univ., ChandigarhGauhati Univ., Guwahati Univ. Rajasthan, JaipurUniv. Jammu, JammuIIT KharagpurSAHA KolkataUniv Calcutta, KolkataVECC Kolkata

Univ. Kashmir, SrinagarBanaras Hindu Univ., Varanasi

Korea:Korea Univ. SeoulPusan National Univ.Norway:Univ. Bergen

Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR DubnaCyprus:

Nikosia Univ.

55 institutions, > 400 members

Dubna, Oct 2008

exploring the qcd phase diagram at high baryon densities: from sps to fair

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