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Claudia Höhne, GSI Darmstadt CBM collaboration

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1 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 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

3 Phasediagram of water H2O

4 Phasediagram of strongly interacting matter
baryochemical potential (~b/0) temperature hadron liquid QGP critical point ? super conductivity nucleus K.Rajagopal, Nucl. Phys. A661 (1999) 150 hadron gas heat compression

5 Strongly interacting matter
quark gluon plasma big bang & early universe T hadron gas How to access ??? neutron stars r "normal" nuclear matter r=r0=0.17 fm-3

6 Heavy ion collisions simulation of a U+U collision at 23 GeV/A (UrQMD)
nucleons mesons excited baryons

7 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 r reached for ~10fm/c = 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 !!!)

8 Heavy ion collisions (III)
simulation of Au+Au collisions at different beam energies → maximum baryon densities r increase with beam energy → energy densities also increase with beam energy [CBM physics group, E. Bratkovskaya, C. Fuchs priv. com.]

9 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 mb (relation to baryon density r) → higher beam energy: higher T, lower mb QCD calculations: difficult .... temperature critical point ? QGP beam energy hadron gas nucleus baryochemical potential (~b/0) K.Rajagopal, Nucl. Phys. A661 (1999) 150 [Andronic et al. Nucl. Phys. A 772, 167 (2006).

10 Theoretical status QGP cSB CSC Lattice QCD Perturbative QCD
Ginzburg-Landau + RG Nuclear theory Perturbative QCD effective models cSB CSC QGP

11 Lattice - QCD T calculations limited to certain observables
and regions of the QCD phase diagram in particular calculations for m ≠ 0 are difficult and conceptual problems could only be solved a few years ago! mb mb = 0 → transition to deconfinement above a certain Tc! Tc ~ 175 MeV driven by energy density ec ~ 1 GeV/fm3 quarks and gluons become relevant degrees of freedom

12 Lattice – QCD (II) phase transition at mb = 0 : crossover
= rapid change of properties but no clearly defined phase boundary mb > 0 not yet completely settled ... but: first order phase transition at large mb → e.g. latent heat phase coexistence region critical point Tcrit ~ 160 MeV mcrit ~ 360 MeV chiral symmetry restoration at high T, large mb [F.Karsch, Z. Fodor, S.D.Katz]

13 Experimental status since 1980s heavy ion collision experiments at AGS, SPS 2000 start of RHIC, 2008 LHC RHIC Brookhaven √s = GeV/nucleon future: LHC SPS CERN GeV/nucleon AGS Brookhaven 2-10 GeV/nucleon [Andronic et al. Nucl. Phys. A 772, 167 (2006).

14 Experimental Status (II)
fireball in chemical equilibrium hadron production successfully described by a statistical model ansatz → all hadron yields (even strangeness!) in chemical equilibrium SPS, RHIC "limiting temperature" T~160 MeV → phase boundary reached, additional energy goes into heating the QGP [Andronic et al. Nucl. Phys. A 772, 167 (2006).

15 Experimental status (III)
energy dedendence of hadron production → changes in SPS energy regime discussions ongoing: hadron gas → partonic phase baryon dominated → meson dominated matter hadron gas transition QGP ?

16 Experimental status – CERN
New 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.

17 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 f

18 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!) baryons n=3 mesons n=2

19 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 e ~ GeV/fm-3 in the fireball!

20 Experimental status – RHIC
RHIC Scientists Serve Up "Perfect" Liquid New 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.

21 Experimental status - summary
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 [Andronic et al. Nucl. Phys. A 772, 167 (2006).

22 CBM ... 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 [Bratkovskaya et al., PRC 69 (2004) ] UrQMD calculation of T, mB as function of reaction time (open symbols – nonequilibrium, full symbols – appr. pressure equilibrium)

23 FAIR at GSI SIS 300 p beam 2 – 90 GeV Ca beam 2 – 45 AGeV
Au beam 2 – 35 AGeV max. beam intensity 109 ions/s high intensity ion beam Compressed Baryonic Matter Ion and Laser induced plasmas: High energy density in matter Cooled antiproton beam: hadron spectroscopy - PANDA So, just to remind you: CBM will be one of the major experiments at the future FAIR facility next to the existing GSI facility at Darmstadt. FAIR will cover a wide range of physics: From the study of nuclei far from stability with the NUSTAR experiments via hadron spectroscopy with PANDA and plasma physics to the investigation of compressed baryonic matter in nucleus-nucleus collisions with the CBM experiment. With CBM we thus will make use in particular of the high intensity ion beam which will be delivered by the SIS 300 synchrotron. Available beam energies for ions will spread a range from 2 to 35 AGeV for gold ions at beam intensities of up to 10-to-9 ions per second. Structure of nuclei far from stability - NUSTAR November 7-8, 2007 FAIR Kick-Off Event !

24 CBM: Physics topics and Observables
The equation-of-state at high B collective flow of identified hadrons particle production at threshold energies (open charm) rare probes! systematic measurements! → comprehensive picture with CBM as 2nd generation experiment! 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' ? QCD critical endpoint excitation function of event-by-event fluctuations (K/π,...) Onset of chiral symmetry restoration at high B in-medium modifications of hadrons (,, e+e-(μ+μ-), D) mostly new measurements CBM Physics Book (theory) in preparation

25 Chiral symmetry restoration
chiral broken world: → chiral partners show different spectral functions! for example: nonstrange I=J=1 multiplet: r- and a1 - meson chiral symmetry restoration requires that vector and axialvector spectral functions become degenerate → dramatic reshaping of spectral functions expected!

26 r – meson n  p p  ++ r e+, μ+ e-, μ-
hadronic properties are expected to be affected by the high density matter r-meson couples to the medium, direct radiation from the early phase vector-meson dominance! vacuum lifetime t0 = 1.3 fm/c → dileptons = penetrating probe connection to chiral symmetry restoration? n e+, μ+ e-, μ- r p p ++ r-meson spectral function [Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/ ]

27 Charm production at threshold
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! D/p ~ 10-7 → experimental challenge! [W. Cassing et al., Nucl. Phys. A 691 (2001) 753] do c and c quarks behave differently in baryon-rich matter? charmonium (cc) in hot and dense matter? relation to deconfinement? HSD simulations

28 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 e = efficiency T = trigger? Y/10w = yield in 10 weeks

29 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  GeV/c Dp/p ~ 1% (p=1 GeV/c) primary and secondary vertex reconstruction (resolution  50 mm) V0 track pattern recognition silicon pixel and strip detectors D+ → p+p+K- (ct = 317 mm) D0 → K-p+ (ct = 124 mm) D0+D0 ~ 1.5∙10-4 central Au+Au, 25 GeV/nucleon

30 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) drives layout beam RICH TRD TOF magnet STS

31 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, p0, h: ECAL PSD for event characterization high speed DAQ and trigger (up to 10 MHz int. rates) → rare probes! electron ID: RICH & TRD  p suppression  104 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!

32 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 provides self-triggered hit detection, pre-processing 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 distribution data are shipped to PC farm with a time stamp online event reconstruction: trigger decision system throughput limited! archiving rate 25 kHz storage: 1Gb/s

33 STS and FEE R&D Fast self-triggered readout chip n-XYTER in collaboration with DETNI prospect: CBM-XYTER Strip sensor development with CIS Erfurt First test sensor delivered spring 2007

34 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

35 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)

36 Hadrons and Hyperons 25 AGeV central AuAu
layout of CBM provides also good hyperon (tracking in the STS) and hadron (TOF) identification → flow, correlations, fluctuations .... p p K

37 Open charm production 25 AGeV central AuAu
D0 → K-p+ and D0 → K+p- (ct = 124 mm), full event reconstruction <D0 + D0> = 1.5 ∙ 10-4 (central Au+Au collisions, 25 AGeV) first pixel detector (MAPS) at 10cm ~53 mm secondary vertex resolution proton identification with TOF 1012 central Au+Au collisions, 25 AGeV

38 Low mass vector mesons 25 AGeV central AuAu 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 e+e- Comb. bg ρ  e+e-   e+e- φ  e+e- π0  γe+e-   π0e+e- η  γe+e- w,f sm = 14 MeV/c2 w,f sm = 11 MeV/c2

39 J/y and y' 25 AGeV central AuAu invariant mass spectra
electrons: p < 11 GeV/c, pt > 1 GeV, 1‰ interaction target (25 mm Au) muons: 225 cm Fe absorber, no pt-cut electrons: 2.4 ∙1010 events J/y sm = 38 MeV/c2 y' sm = 45 MeV/c2 muons: 4 ∙108 events J/y sm = 22 MeV/c2 y' sm = 33 MeV/c2

40 CBM CBM@FAIR – high mB, 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

41 CBM collaboration 51 institutions, > 400 members China: CCNU Wuhan
USTC Hefei Croatia: University of Split RBI, Zagreb Univ. Münster FZ Rossendorf GSI Darmstadt Korea: Korea Univ. Seoul Pusan National Univ. Russia: IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg Hungaria: KFKI Budapest Eötvös Univ. Budapest Norway: Univ. Bergen Kurchatov Inst. Moscow LHE, JINR Dubna LPP, JINR Dubna Poland: Krakow Univ. Warsaw Univ. Silesia Univ. Katowice Nucl. Phys. Inst. Krakow Cyprus: Nikosia Univ. India: Aligarh Muslim Univ., Aligarh IOP Bhubaneswar Panjab Univ., Chandigarh Univ. Rajasthan, Jaipur Univ. Jammu, Jammu IIT Kharagpur SAHA Kolkata Univ Calcutta, Kolkata VECC Kolkata Univ. Kashmir, Srinagar Banaras Hindu Univ., Varanasi Czech Republic: CAS, Rez Techn. Univ. Prague France: IPHC Strasbourg LIT, JINR Dubna MEPHI Moscow Obninsk State Univ. PNPI Gatchina SINP, Moscow State Univ. St. Petersburg Polytec. U. Portugal: LIP Coimbra Romania: NIPNE Bucharest Germany: Univ. Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst. Univ. Frankfurt Univ. Mannheim Ukraine: Shevchenko Univ. , Kiev 51 institutions, > 400 members Dresden, September 2007

42 additional slides

43 STS R&D Microstrip Sensors Tracking Stations layout studies
module design

44 fast self-triggered readout electronics
NXYTER chip produced; DETNI − GSI micro-strip sensor test system under construction

45 Sequential dissociation of charmonium?
Quarkonium dissociation temperatures – Digal, Karsch, Satz (J/)/DY = 29.2  2.3 L = 3.4 fm Preliminary! Preliminary! [NA60]

46 Collective flow elliptic flow v2:
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/ ] full energy dependence needed! elliptic flow v2: initial overlap eccentricity → particle azimuthal distributions v2 central midcentral peripheral f [NA49, PRC68, (2003)]

47 K/p fluctuations 2nd order phase transition at the critical point
→ fluctuations expected measure e.g. particle ratios (K/p) event-by-event and compare to an event average increase of K/p fluctuations for lower energies observed interpretation open

48 Even charm quarks flow! even charm quarks participate in the flow!

49 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! Grigorian, Blaschke, Klähn, astro-ph/

50 Detector R&D – RPC R&D HADES
main issue for many detectors: high rates! RPC development together with HADES, FOPI upgrades study different materials!

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