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The Compressed Baryonic Matter experiment at the future accelerator
facility in Darmstadt
Claudia Höhne
GSI Darmstadt, Germany
Claudia Höhne NPDC 18 Prague
nuclei
hadronic phase
SPS
RHIC
lattice QCD : Fodor / Katz, Nucl. Phys. A 715 (2003) 319
SIS300
dilute hadron gasdense baryonic medium
Motivation
Phase diagram of strongly interacting matter
• high T, low B
top SPS, RHIC, LHC
• low T, high B
SIS
• intermediate range ?
low energy runs SPS, AGS
SIS 300 @ GSI !
Highest baryon densities
Critical point?
Deconfinement?
Claudia Höhne NPDC 18 Prague
Motivation
SIS300 light, heavy ions
Phase diagram of strongly interacting matter
• high T, low B
top SPS, RHIC, LHC
• low T, high B
SIS
• intermediate range ?
low energy runs SPS, AGS
SIS 300 @ GSI !
Highest baryon densities
Critical point?
Deconfinement? and region of maximum of relative strangeness production
Claudia Höhne NPDC 18 Prague
Motivation
[Allton et al., Phys. Rev. D68, 014507 (2003)][Allton et al., Phys. Rev. D66, 074507 (2002)] *[Fodor, Katz, JHEP 0404, 050 (2004)]
q/T=1
critical point *
recent improvements in lattice-QCD allow for calculations at finite B :
• large baryon-number density fluctuations at the phase border for q/T=1
• critical point at TE=162 2 MeV, E=360 40 MeV *
intermediate range of phase diagram!
Claudia Höhne NPDC 18 Prague
Known so far ...
Low energy run at SPS (20, 30, 40 AGeV): Relative strangeness production shows ...
• sharp maximum in energy dependence: transition from hadronic to partonic phase?
• dynamical fluctuations which increase towards lower energies: critical point?
[J. Phys. G 30, 1381 (2004)]
4
1
43
2
NN
NNN
s
msF
KKEs
2
NA49
NA49
[J. Phys. G 30, 701 (2004)]
Claudia Höhne NPDC 18 Prague
Known so far ...
Low energy run at SPS (40 AGeV): e+e-
• enhancement of low-mass dilepton pairs, larger at 40 AGeV compared to 158 AGeV
• in medium modification of ?
need more and better measurements also at lower energies!
CERES [Phys. Rev. Lett. 91, 042301 (2003)]
Claudia Höhne NPDC 18 Prague
Known so far ...
A+A collisions at SIS : strangeness production in medium
[M. Lutz, Phys. Lett. B 426, 12 (1998)]KAOS Collaboration
experimental evidence for modification of kaon energy in medium!
• yields, rapidity spectra, azimuthal distributions ...
K+
RBBU KN Pot.
no KN Pot.
Claudia Höhne NPDC 18 Prague
Open questions ...
various QCD inspired models predict a change of the D-mass in a hadronic medium
• in analogy to kaon mass modification, but drop for both, D+ and D-
• substantial change (several 100 MeV) already at =0
• effect for charmonium is substantially smaller
[Mishra et al ., Phys. Rev. C 69, 015202 (2004) ]
Claudia Höhne NPDC 18 Prague
Open questions ...
Consequence of reduced D mass: DD threshold drops below charmonium states
[Mishra et al., Phys. Rev. C 69, 015202 (2004) ]
• decay channels into DD open for ’, c, J/
broadening of charmonium states suppression of J/ lepton pair channel (large fraction of J/ from higher states) (slight) enhancement of D mesons
Claudia Höhne NPDC 18 Prague
Open questions ...
... but even charm production near threshold is not known
[Gorenstein et al J. Phys. G 28 (2002) 2151]
central Au+Au
ccN
Predictions of open charm yield for central A+A collisions differ by orders of magnitude for different production scenarios, especially at low energies
[W. Cassing et al., Nucl. Phys. A 691, 753 (2001)]
Claudia Höhne NPDC 18 Prague
CBM experiment
physics topics observables
deconfinement at high B ?
softening of EOS ?
strangeness production: K,
charm production: J/, D
flow excitation function
Critical point ? event-by-event fluctuations
e+e-
open charm
in-medium properties of hadrons
onset of chiral symmetry restoration at high B
Claudia Höhne NPDC 18 Prague
CBM experiment
observables detector requirements
strangeness production: K,
charm production: J/, D
flow excitation function
event-by-event fluctuations
e+e-
open charm
all-in-one device suitable for every purpose
tracking in high track density environment (~ 1000)
hadron ID
lepton ID
myons, photons
secondary vertex reconstruction
(resolution 50 m)
large statistics: high beam intensity (109 ions/sec.)
high interaction rates (10 MHz)
fast, radiation hard detector
efficient trigger
rare signals!
Claudia Höhne NPDC 18 Prague
CBM detector layout
• tracking, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field
• electron ID: RICH1 & TRD (& ECAL) suppression 104
• hadron ID: TOF (& RICH2)
• photons, 0, : ECAL
• high speed DAQ and trigger
beam
target STS
TRDs
TOF
ECAL
RICHs
magnet
Claudia Höhne NPDC 18 Prague
SIS 100 Tm
SIS 300 Tm
U: 35 AGeV
p: 90 GeV
CBM @ FAIR
Facility for Antiproton and Ion Research
„next generation“ accelerator facility:
• double-ring synchrotron
• simultanous, high quality, intense primary and secondary beams
• cooler/ storage rings (CR, NESR, HESR)
Ion and Laser induced plasmas: High energy density in matter
Compressed baryonic matter
Cooled antiproton beam: hadron spectroscopy
Structure of nuclei far from stability
Claudia Höhne NPDC 18 Prague
Tracking with STS
Experimental conditions:• 5cm (1st STS) up to 2 hits/mm2 per event • 100cm (7th STS) < 0.01 hits/mm2
7 planar layers of pixel/ strip detectors:• high precision vertex reconstruction: 2 pixel layers at 5cm, 10 cm downstream of target • fast strip detectors for outer stations (20, 40, 60, 80, 100 cm from target)
Reconstruction efficiency > 95 %Momentum resolution ≈ 0.6 %
frac
tion
of r
econ
stru
cted
tra
cks
p [GeV/c]
Claudia Höhne NPDC 18 Prague
STS
Requirements:
• radiation hardness
• low material budget: d < 200 m
• fast read out
• good position resolution < 20 m
MIMOSA IVIReS/ LEPSI Strasbourg
R&D on Monolithic Active Pixel Sensors (MAPS):
• pitch 20 m
• thickness < 100 m
• single hit resolution ~ 3m
• problem: radiation hardness and readout speed ( event pile up in first 2 STS)
• fallback solution: hybrid detectors (problem: thickness, granularity!)
Claudia Höhne NPDC 18 Prague
electron ID with RICH 1
radiator gas: N2 th = 41 , p,th = 5.7 GeV/c (almost) hadron blind
photodetectors: photomultipliers (or gas detectors)
aim: suppression ~ 104 - 103
-spectrum at for central Au+Au collision at 25 AGeV (UrQMD)
Claudia Höhne NPDC 18 Prague
RICH 1
two mirrors: beryllium covered with glass, R = 450 cm
two focal planes (3.6 m2 each) separated vertically, shielded by magnet yoke
layout RICH: side view
z (beam)
y
rings in focal plane
Claudia Höhne NPDC 18 Prague
TRD
Task: e/ separation > 100, tracking
Setup: 9 layers in three stations (4m, 6m, 8m from target) area per layer 25, 50, 100 m2
efficiency < 1% reachable with 9 layers:
R&D
• for most of the system state-of-the art is appropriate (ALICE)
• inner part: R&D on fast gas detectors in progress (drift chamber/ GEM/ straw tubes)
Requirements:
• high counting rate (up to 150 kHz/cm2)
• fast readout (10 MHz)
• large area
• position resolution ~ 200 m
Claudia Höhne NPDC 18 Prague
Hadron ID with TOF
bulk of hadrons (, K, p) can be well identified with TOF = 80 – 100 ps
identification probability of K- for TOF = 80 ps
Claudia Höhne NPDC 18 Prague
RPC as TOF detector
Challenge for TOF : high counting rate (25 kHz/cm2)
large area (130 m2 @ 10 m)
time resolution ~ 80 ps
R&D Coimbra, Portugal
prototype: single gap counters with metal and plastic electrodes (resistivity 109 cm)
Claudia Höhne NPDC 18 Prague
RICH 2 (?)
Kaon ID by TOF quickly deteriorates above 4 GeV
Option for RICH2 ?e.g. thr = 30 p,thr = 4.2 GeV, pK,thr=15 GeV
problem: ring finding in high hit density environment
Kaon ID by RICH for p > 4 GeV would be desirable
identification probability of K- for TOF = 80 ps Momentum distribution of kaons from D0 decays
Claudia Höhne NPDC 18 Prague
DAQ & trigger architechtureRequirements• efficient detection of rare probes (D, J/, low-mass dilepton pairs): event rate 25 kHz
evaluation of complex signatures• fast: 1st level trigger at full design interaction rate of 10MHz
reconstruct ~ 109 tracks/s, secondary vertices ...• data volume in 1st level trigger ~ 50 Gbytes/s
event size ~ 40kbyte
clock
Detectors
Frontend electronics
Buffer pool
Event builder and selectorstorage
(1Gbyte/s)
self-triggered hit detectionpre-processing
feature extraction
each hit transported as address/ timestamp/ value
extraction of physical signaturestrigger decision
essential performance limitation not latency but throughput
Claudia Höhne NPDC 18 Prague
Feasibility Study: D0
Key variable to suppress background: secondary vertex position
D0 K-+ (c=124.4 m, BR 3.9 0.1%)
central Au+Au @ 25 AGeV (HSD): <D0> ~ 10-3
simulation including various cuts (vz !)
S/B ~ 1
detection rate ~ 13k/h at 1MHz interaction rate
Crucial detector parameters• material in STS• single hit resolution
Claudia Höhne NPDC 18 Prague
Feasibility Study: J/ e+e-
extremely rare signal (central Au+Au @ 25 AGeV ~ 10-5 /event)
6% branching ratio e+e-background from various sources: conversion, Dalitz decays of 0 and , , misidentified very efficient cut on single electron pt, pair opening angle
S/B > 1 should be feasible
Claudia Höhne NPDC 18 Prague
Feasibility Study: e+e-
branching ratio ~ 4.44 10-5 () – 3.1 10-4 ()
background from various sources: conversion, Dalitz decays of 0 and , misidentified no easy pt-cut as for J/ sophisticated cutting strategy necessary
depends crucially on elimination of conversion pairs by tracking
and charged pion discrimination by RICH and TRD ( 104 !)
idealized simulation:• no momentum resolution• no misidentification
• cut on pt, pair opening angle, prim. vertex track S/B 0.5-1
Claudia Höhne NPDC 18 Prague
Status of project
So far ...
• November 2001 Conceptual Design Report, Cost estimate 675 M €
• July 2002 German Wissenschaftsrat recommends realisation
• February 2003 German Federal Gouvernment decides to build the facility, will pay 75%
• January 2004 CBM Letter of Intent submitted
• CBM collaboration is formed: 250 scientiest from 39 institutions
• work in progress: detector design and optimization
R&D on detector components
feasibility studies of key observables
• next step: Technical Proposal January 2005
• could run in 2012!
Claudia Höhne NPDC 18 Prague
CBM collaboration
Croatia: RBI, Zagreb
Cyprus: Nikosia Univ. Czech Republic:Czech Acad. Science, RezTechn. Univ. Prague France: IReS Strasbourg
Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. Mannheim Univ. MarburgUniv. MünsterFZ RossendorfGSI Darmstadt
Romania: NIPNE Bucharest
Russia:CKBM, St. PetersburgIHEP ProtvinoINR TroitzkITEP MoscowKRI, St. PetersburgKurchatov Inst., MoscowLHE, JINR DubnaLPP, JINR DubnaLIT, JINR DubnaPNPI GatchinaSINP, Moscow State Univ.
Spain: Santiago de Compostela Univ. Ukraine: Univ. Kiev
Hungaria:KFKI BudapestEötvös Univ. Budapest
Italy: INFN Frascati
Korea:Korea Univ. SeoulPusan National Univ.
Norway:Univ. Bergen
Poland:Jagiel. Univ. Krakow Silesia Univ. KatowiceWarsaw Univ.Warsaw Tech. Univ. Portugal: LIP Coimbra
Claudia Höhne NPDC 18 Prague
CBM time schedule
Subproject 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Si-Tracker
RICH
TRD
TOF-RPC
ECAL
Trigger/DAQ
Electronics
Magnet
Infrastructure
simulations, R&D, design Prototyping Construction Installation, test
Milestones: 1. Technical Proposal begin of 2005 2. Technical Design Report end of 2007
Claudia Höhne NPDC 18 Prague
Hit rates for 107 minimum bias Au+Au collisions at 25 AGeV:
Rates of > 10 kHz/cm2 in large part of detectors ! main thrust of our detector design studies
experimental conditions
Claudia Höhne NPDC 18 Prague
CBM R&D working packages
Feasibility, Simulations
D Kπ(π)GSI Darmstadt, Czech Acad. Sci., RezTechn. Univ. Prague
,ω, e+e-
Univ. KrakowJINR-LHE Dubna
J/ψ e+e-
INR Moscow
Hadron ID Heidelberg Univ,Warsaw Univ.Kiev Univ. NIPNE BucharestINR Moscow
GEANT4: GSI
TrackingKIP Univ. HeidelbergUniv. MannheimJINR-LHE Dubna
Design & constructionof detectors
Silicon PixelIReS StrasbourgFrankfurt Univ.,GSI Darmstadt,RBI Zagreb,Univ. Krakow
Silicon StripSINP Moscow State U.CKBM St. PetersburgKRI St. Petersburg
RPC-TOFLIP Coimbra, Univ. Santiago de Com.,Univ. Heidelberg,GSI Darmstadt,Warsaw Univ.NIPNE BucharestINR MoscowFZ RossendorfIHEP ProtvinoITEP Moscow
Fast TRDJINR-LHE, DubnaGSI Darmstadt,Univ. MünsterINFN Frascati
Straw tubesJINR-LPP, DubnaFZ RossendorfFZ JülichTech. Univ. Warsaw
ECAL ITEP Moscow GSI DarmstadtUniv. Krakow
RICH IHEP Protvino GSI Darmstadt
Trigger, DAQKIP Univ. HeidelbergUniv. MannheimGSI DarmstadtJINR-LIT, DubnaUniv. BergenKFKI BudapestSilesia Univ. KatowiceUniv. Warsaw
MagnetJINR-LHE, DubnaGSI Darmstadt
AnalysisGSI Darmstadt,Heidelberg Univ,
Data Acquis.,Analysis
Claudia Höhne NPDC 18 Prague
Acceptance of D0 and J/p
t [G
eV
/c]
D0 J/ψ
Claudia Höhne NPDC 18 Prague
misidentification
0 %
1 %0.1 %
0.01 %
Claudia Höhne NPDC 18 Prague
Granularity:inner region 2x2 cm2
intermediate region 5x5 cm2
outer region 10x10 cm2
Lead-scintillator calorimeter:• 0.5 – 1 mm thick tiles• 25 X0 total length• PM read out
Distance between electron and closest track in the innermost region
Tests of detector module prototype: July 2004 at CERN
Design of ECAL
Design goals of sampling calorimeter:• energy resolution of 5/E (%)• high-rate capability up to 15 kHz/cm2
• e//() discrimination of 25-200• total area ~200m2
Claudia Höhne NPDC 18 Prague
FAIR @ GSI