Das CBM Experiment bei FAIR - Untersuchungen des QCD Phasendiagrams bei hohen Baryonendichten - Claudia Höhne, GSI Darmstadt CBM collaboration

Das CBM Experiment bei FAIR

- Untersuchungen des QCD Phasendiagrams bei hohen Baryonendichten -

Claudia Höhne, GSI Darmstadt

CBM collaboration

2 Claudia Höhne Seminar des Instituts für Kernphysik, Mainz, 29.10.2007

Outline

• Introduction & motivation

• phase diagram of strongly interacting matter

• A+A collisions

• theoretical status

• experimental status

• CBM experiment

• observables

• detector layout

• detector R&D

• feasibility studies

• Summary & Outlook


Phasediagram of water

H2O


Phasediagram of strongly interacting matter

baryochemical potential (~b/0)

tem

pera

ture

hadron liquid

QGPcritical point ?

super conductivity

nucleus

K.Rajagopal, Nucl. Phys. A661 (1999) 150

hadron gas

compression

heat


Strongly interacting matter

T

big bang & early universe

"normal" nuclear matter=0=0.17 fm-3

neutron stars

hadron gas

quark gluon plasma

How to access ???


Heavy ion collisions

simulation of a U+U collision at 23 GeV/A (UrQMD)

nucleons mesons excited baryons


Heavy ion collisions (II)

UrQMD 160 GeV Au+Au

before collision

compression and heating (T >> Tchem ~ 160 MeV)

thermalization of the "fireball"

(high T and reached for ~10fm/c = 3.3 10-23 s)

expansion

chemical freezeout (number and type of particles frozen)

kinetic freezeout (particle momenta frozen)

Tchem ~ 160 MeV ~ 2∙1012 K)

(kT unit system, k=8.6∙10-5 eV K-1 → 100 MeV = 1.16∙1012 K !!!)


Heavy ion collisions (III)

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

simulation of Au+Au collisions at different beam energies

→ maximum baryon densities increase with beam energy

→ energy densities also increase with beam energy


Heavy ion collisions (IV)• in heavy ion collisions nuclear matter can be compressed and heated

• statistical ansatz: describe "final state" hadron gas as grandcanonical ensemble → temperature T, baryochemical potential b (relation to baryon density ) → higher beam energy: higher T, lower b

• QCD calculations: difficult ....

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

baryochemical potential (~b/0)

tem

pera

ture

QGPcritical point ?

nucleus

K.Rajagopal, Nucl. Phys. A661 (1999) 150

hadron gasbeam energy


SB CSC

QGP

Lattice QCD

Ginzburg-Landau + RG

Nuclear theory

Perturbative QCD

effective models

Theoretical status


Lattice - QCD

• calculations limited to certain observables and regions of the QCD phase diagram

• in particular calculations for ≠ 0 are difficult and conceptual problems could only be solved a few years ago!

T

b

• b = 0

→ transition to deconfinement above a certain Tc!

Tc ~ 175 MeV

driven by energy density

c ~ 1 GeV/fm3

• quarks and gluons become relevant degrees of freedom


Lattice – QCD (II)

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

• phase transition at b = 0 : crossover

= rapid change of properties but no clearly defined phase boundary

• b > 0 not yet completely settled ... but:

• first order phase transition at large b

→ e.g. latent heat phase coexistence region

• critical point

Tcrit ~ 160 MeV crit ~ 360 MeV

• chiral symmetry restoration at high T, large b


Experimental status


AGS Brookhaven2-10 GeV/nucleon

SPS CERN20 -160 GeV/nucleon

RHIC Brookhaven√s = 130 - 200 GeV/nucleon future: LHC

• since 1980s heavy ion collision experiments at AGS, SPS

• 2000 start of RHIC, 2008 LHC


Experimental Status (II)

• "limiting temperature" T~160 MeV

→ phase boundary reached, additional energy goes into heating the QGP


SPS, RHIC

fireball in chemical equilibrium

• hadron production successfully described by a statistical model ansatz

→ all hadron yields (even strangeness!) in chemical equilibrium


Experimental status (III)

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

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

NN

NN

NNN ss

msF

41

43

2

hadron gas

QGP

transition

?


Experimental status – CERNNew State of Matter created at CERN

At a special seminar on 10 February, spokespersons from the experiments on CERN* 's Heavy Ion programme presented compelling evidence for the existence of a new state of matter in which quarks, instead of being bound up into more complex particles such as protons and neutrons, are liberated to roam freely.

10.02.2000


elliptic flow v2

• particle emission pattern in plane transverse to the reaction plane

• initial overlap eccentricity is transformed in momentum anisotropy

• driven by pressure from overlap region

Fourier expansion of the dN/dϕ distribution:

v2


Experimental status (IV)• all flow observations scale extremely well if taking the underlying number of quarks into account!

• flow also seen for charm quarks!

→ 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!)

KE m m mT T T ( ) 1

baryons n=3mesons n=2


Experimental status (V)

• partons should loose energy in a dense and hot medium

→ jet suppression!

→ results imply huge gluon densities corresponding to an initial temperature of ~2Tcrit and ~ 14-20 GeV/fm-3 in the fireball!


Experimental status – RHIC

RHIC Scientists Serve Up "Perfect" LiquidNew state of matter more remarkable than predicted - raising many new questions

April 18, 2005

TAMPA, FL -- The four detector groups conducting research at the Relativistic Heavy Ion Collider (RHIC) -- a giant atom "smasher" located at the U.S. Department of Energy's Brookhaven National Laboratory -- say they've created a new state of hot, dense matter out of the quarks and gluons that are the basic particles of atomic nuclei, but it is a state quite different and even more remarkable than had been predicted. In peer-reviewed papers summarizing the first three years of RHIC findings, the scientists say that instead of behaving like a gas of free quarks and gluons, as was expected, the matter created in RHIC's heavy ion collisions appears to be more like a liquid.


Experimental status - summary

[An

dro

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et

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Nu

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Ph

ys.

A 7

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, 1

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6).

• partonic phase created in the early phase of A+A collisions for SPS + RHIC energies

• characterization of this phase? → RHIC: more an ideal liquid than a gas of quarks and gluons, crossover? → LHC: weakly coupled QGP reachable? → high baryon density region?

• where is deconfinement reached first?

• order of the phase transition? critical point?

• characteristics of high baryon density matter?

2nd generation experiment!

CBM at FAIR!10-45 GeV/nucleon


CBM

[Bra

tkov

skay

a et

al.,

PR

C 6

9 (2

004)

054

907

]

UrQMD calculation of T, B as function of reaction time

(open symbols – nonequilibrium,

full symbols – appr. pressure equilibrium)

... should be in the right energy range for the "onset of deconfinement", the first order phase transition (and the critical point)

... as a 2nd generation experiment can built on the knowledge gained over the last 20 years (observables, experimental techniques)

... will be able to use probes never measured before at these energies but expected to be sensitive to the created matter


FAIR at GSI

Ion and Laser induced plasmas: High energy density in matter

high intensity ion beamCompressed Baryonic Matter

Cooled antiproton beam: hadron spectroscopy - PANDA

Structure of nuclei far from stability - NUSTAR

SIS 300 p beam 2 – 90 GeVCa beam 2 – 45 AGeVAu beam 2 – 35 AGeVmax. beam intensity 109 ions/s

November 7-8, 2007FAIR Kick-Off Event !


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 identified hadrons• particle production at threshold energies (open charm)

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

• mostly new measurements• CBM Physics Book (theory) in preparation

rare probes!

systematic measurements!

→ comprehensive picture with CBM as 2nd generation experiment!


Chiral symmetry restoration

• chiral broken world:

→ chiral partners show different spectral functions!

for example: nonstrange I=J=1 multiplet: and a1 - meson

• chiral symmetry restoration requires that vector and axialvector spectral functions become degenerate

→ dramatic reshaping of spectral functions expected!


– meson

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

• hadronic properties are expected to be affected by the high density matter

• -meson couples to the medium, direct radiation from the early phase

• vector-meson dominance!

• vacuum lifetime 0 = 1.3 fm/c → dileptons = penetrating probe

• connection to chiral symmetry restoration?

pn

++

p

e+, μ+

e-, μ-

-meson spectral function


Charm production at threshold

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

HSD simulations

• CBM will measure charm production at threshold

→ after primordial production, the survival and momentum of the charm quarks depends on the interactions with the dense and hot medium!

→ direct probe of the medium!

• do c and c quarks behave differently in baryon-rich matter?

• charmonium (cc) in hot and dense matter?

• relation to deconfinement?

D/ ~ 10-7 → experimental challenge!


interaction rates

• FAIR will provide high intensity beams up to 109 ions/s

• high availability of beam due to parallel operation of FAIR

• 1% interaction target → 10 MHz interaction rate

→ rare probes!

(rates for D limited because of readout speed of silicon pixel detectors)

BR = branching ratio = efficiencyT = trigger? Y/10w = yield in 10 weeks


STS tracking – heart of CBM

Challenge: high track density 600 charged particles in 25o

→ trigger on D-mesons for background rejection!

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)

silicon pixel

and strip detectors

D0+D0 ~ 1.5∙10-4 central Au+Au, 25 GeV/nucleon


CBM – detector concept• fixed target experiment, "medium" energies

→ large solid angle to be covered

• high rate, multipurpose detector including open charm reconstruction

→ fast, excellent tracking based on silicon pixel and strip detectors directly behind the target and inside a magnetic field

→ add particle identification afterwards (leptons, hadrons)

beam

magnet

STS

RICH

TRDTOF

drives layout


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 (up to 10 MHz int. rates) → rare probes!

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

MVD + STS

... measuring both channels would be the best crosscheck of results we can ever do!


DAQ & FEE

• for rare probes highly efficient triggers needed!

• D-meson → online tracking and 2ndary vertex finding

• DAQ and FEE concept based on "self triggered readout" electronics

FEE

CNet

BNet

HNet

to archive

TNet

FEE boards

CNet links

DCB: data combiner boards

CDL: CBM detector links

ABB: active buffer boards

EB Switch

Backend processors

General Network

Clock/Trigger distributiondata are shipped to PC farm with a time stamp

online event reconstruction: trigger decision

system throughput limited!archiving rate 25 kHz

storage: 1Gb/s

FEE provides self-triggered hit detection, pre-processing


STS and FEE R&D

Strip sensor development with CIS ErfurtFirst test sensor delivered spring 2007

Fast self-triggered readout chip n-XYTER in collaboration with DETNIprospect: CBM-XYTER


Detector R&D – TRD

• main issue for many detectors: high rates!

• for example: TRDs → reduce gas gap/ operate with pad plane in the middle of gas gap


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 (UrQMD)


Hadrons and Hyperons

K

p

• layout of CBM provides also good hyperon (tracking in the STS) and hadron (TOF) identification

→ flow, correlations, fluctuations ....

25 AGeVcentral AuAu


Open charm production• D0 → K-+ and D0 → K+- (c= 124 m), full event reconstruction

• <D0 + D0> = 1.5 ∙ 10-4 (central Au+Au collisions, 25 AGeV)

• first pixel detector (MAPS) at 10cm

• ~53 m secondary vertex resolution

• proton identification with TOF

1012 central Au+Au collisions, 25 AGeV

25 AGeVcentral AuAu

0


Low mass vector mesons

invariant mass spectra

• electrons: pt > 0.2 GeV/c background dominated by physical sources (75%)

• muons: intrinsic p>1.5 GeV cut (125 cm Fe absorber), use TOF information background dominated by misidentified muons

electrons: 200k events background 4 ∙108 events – signal 20k ev.All eAll e++ee--

Comb. bgComb. bgρρ ee++ee--

ee++ee--

φφ ee++ee--

ππ0 0 γγee++ee--

ππ00ee++ee--

ηη γγee++ee--

m = 14 MeV/c2 m = 11 MeV/c2

25 AGeVcentral AuAu


electrons: 2.4 ∙1010 events

J/ m = 38 MeV/c2

' m = 45 MeV/c2

J/ and '

invariant mass spectra

• electrons: p < 11 GeV/c, pt > 1 GeV, 1‰ interaction target (25 m Au)

• muons: 225 cm Fe absorber, no pt-cut

muons: 4 ∙108 events

J/ m = 22 MeV/c2

' m = 33 MeV/c2

25 AGeVcentral AuAu


CBMCBM@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

• 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 2015


CBM collaborationRussia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg

China:CCNU WuhanUSTC Hefei

Croatia:

University of SplitRBI, 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

Univ. MünsterFZ RossendorfGSI Darmstadt

Czech Republic:CAS, RezTechn. Univ. Prague

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

Hungaria:KFKI BudapestEötvös Univ. BudapestIndia:Aligarh Muslim Univ., AligarhIOP BhubaneswarPanjab Univ., ChandigarhUniv. Rajasthan, JaipurUniv. Jammu, JammuIIT KharagpurSAHA KolkataUniv Calcutta, KolkataVECC KolkataUniv. Kashmir, SrinagarBanaras Hindu Univ., Varanasi

Korea:Korea Univ. SeoulPusan National Univ.

Norway:Univ. Bergen

Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR Dubna

51 institutions, > 400 members

Dresden, September 2007

Cyprus: Nikosia Univ.


additional slides


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


Sequential dissociation of charmonium?

Quarkonium dissociation temperatures – Digal, Karsch, Satz

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

Preliminary! Preliminary!

[NA60]


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


K/ fluctuations

• 2nd order phase transition at the critical point

→ fluctuations expected

• measure e.g. particle ratios (K/) event-by-event and compare to an event average

22mixeddatadyn

• increase of K/ fluctuations for lower energies observed

• interpretation open


Even charm quarks flow!

• even charm quarks participate in the flow!


Relation to EOS

• maximum mass in dependence on radius depends strongly on underlying EOS (compressibility of neutron matter!)

→ compare with measurements!

• same for maximum mass and density in the center

• try to use constraints on EOS from A+A collisions!

Grig

orian, Blaschke, K

lähn, astro-ph

/0612783


Detector R&D – RPC

• main issue for many detectors: high rates!

• RPC development together with HADES, FOPIupgrades

• study different materials!

R&D HADES

Documents

Das CBM Experiment bei FAIR - Untersuchungen des QCD Phasendiagrams bei hohen Baryonendichten - Claudia Höhne, GSI Darmstadt CBM collaboration