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The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt - PowerPoint PPT Presentation

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The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt. Claudia Höhne GSI Darmstadt, Germany. RHIC. SPS. SIS300. hadronic phase. nuclei. Motivation. Phase diagram of strongly interacting matter.

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The Compressed Baryonic Matter experiment at the future accelerator facility in Darmstadt

Claudia Höhne

GSI Darmstadt, Germany




hadronic phase



Phase diagram of strongly interacting matter

lattice QCD : Fodor / Katz, Nucl. Phys. A 715 (2003) 319

  • high T, low mB

  •  top SPS, RHIC, LHC

  • low T, high mB

  •  SIS

  • intermediate range ?

     low energy runs SPS, AGS

     SIS 300 @ GSI !

  • Highest baryon densities

  • Critical point?

  • Deconfinement?

dense baryonic medium

dilute hadron gas


Phase diagram of strongly interacting matter

SIS300 light, heavy ions

  • high T, low mB

  •  top SPS, RHIC, LHC

  • low T, high mB

  •  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

critical point *



  • recent improvements in lattice-QCD allow for calculations at finite mB :

  • large baryon-number density fluctuations at the phase border for mq/T=1

  • critical point at TE=162  2 MeV, mE=360  40 MeV *

  •  intermediate range of phase diagram!

[Allton et al., Phys. Rev. D68, 014507 (2003)]

[Allton et al., Phys. Rev. D66, 074507 (2002)]

*[Fodor, Katz, JHEP 0404, 050 (2004)]

Known so far ...

Low energy run at SPS (20, 30, 40 AGeV): Relative strangeness production shows ...

[J. Phys. G 30, 701 (2004)]

[J. Phys. G 30, 1381 (2004)]



  • sharp maximum in energy dependence: transition from hadronic to partonic phase?

  • dynamical fluctuations which increase towards lower energies: critical point?

Known so far ...

Low energy run at SPS (40 AGeV): r, w, f e+e-


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

  • enhancement of low-mass dilepton pairs, larger at 40 AGeV compared to 158 AGeV

  • in medium modification of r ?

  •  need more and better measurements also at lower energies!



no KN Pot.

Known so far ...

A+A collisions at SIS : strangeness production in medium

KAOS Collaboration

[M. Lutz, Phys. Lett. B 426, 12 (1998)]

  • experimental evidence for modification of kaon energy in medium!

  • yields, rapidity spectra, azimuthal distributions ...

Open questions ...

various QCD inspired models predict a change of the D-mass in a hadronic medium

[Mishra et al ., Phys. Rev. C 69, 015202 (2004) ]

  • 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

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/y

  • broadening of charmonium states

  • suppression of J/y  lepton pair channel (large fraction of J/y from higher states)

  • (slight) enhancement of D mesons

Open questions ...

... but even charm production near threshold is not known

[Gorenstein et al J. Phys. G 28 (2002) 2151]

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)]

central Au+Au

physics topics


deconfinement at high rB ?

softening of EOS ?

strangeness production: K, L, S, X, W

charm production: J/y, D

flow excitation function

in-medium properties of hadrons

 onset of chiral symmetry restoration at high rB

r, w, f e+e-

open charm

Critical point ?

event-by-event fluctuations

CBM experiment

strangeness production: K, L, S, X, W

charm production: J/y, D

flow excitation function

rare signals!

r, w, f e+e-

open charm

event-by-event fluctuations

CBM experiment


detector requirements

tracking in high track density environment (~ 1000)

hadron ID

lepton ID

myons, photons

secondary vertex reconstruction

(resolution  50 mm)

large statistics: high beam intensity (109 ions/sec.)

high interaction rates (10 MHz)

fast, radiation hard detector

efficient trigger

all-in-one device suitable for every purpose

CBM detector layout

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

  • electron ID: RICH1 & TRD (& ECAL)  p suppression  104

  • hadron ID: TOF (& RICH2)

  • photons, p0, m: ECAL

  • high speed DAQ and trigger









SIS 100 Tm

SIS 300 Tm

U: 35 AGeV

p: 90 GeV


  • 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)

Cooled antiproton beam: hadron spectroscopy

Ion and Laser induced plasmas: High energy density in matter

Structure of nuclei far from stability

Compressed baryonic matter

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)

fraction of reconstructed tracks

Reconstruction efficiency > 95 %

Momentum resolution ≈ 0.6 %

p [GeV/c]


  • Requirements:

  • radiation hardness

  • low material budget: d < 200 mm

  • fast read out

  • good position resolution < 20 mm


IReS/ LEPSI Strasbourg

  • R&D on Monolithic Active Pixel Sensors (MAPS):

  • pitch 20 mm

  • thickness < 100 mm

  • single hit resolution ~ 3mm

  • problem: radiation hardness and readout speed ( event pile up in first 2 STS)

  • fallback solution: hybrid detectors (problem: thickness, granularity!)

electron ID with RICH 1

radiator gas: N2 gth = 41 , pp,th = 5.7 GeV/c  (almost) hadron blind

photodetectors: photomultipliers (or gas detectors)

aim: p suppression ~ 104 - 103

p-spectrum at for central Au+Au collision at 25 AGeV (UrQMD)


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

rings in focal plane


z (beam)


Task: e/p separation > 100, tracking

Setup: 9 layers in three stations (4m, 6m, 8m from target) area per layer 25, 50, 100 m2

p efficiency < 1% reachable with 9 layers:

  • Requirements:

  • high counting rate (up to 150 kHz/cm2)

  • fast readout (10 MHz)

  • large area

  • position resolution ~ 200 mm

  • 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)

Hadron ID with TOF

identification probability of K- for sTOF = 80 ps

bulk of hadrons (p, K, p) can be well identified with sTOF = 80 – 100 ps

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 109Wcm)

RICH 2 (?)

Kaon ID by TOF quickly deteriorates above 4 GeV

identification probability of K- for sTOF = 80 ps

Momentum distribution of kaons from D0 decays

Kaon ID by RICH for p > 4 GeV would be desirable

Option for RICH2 ?

e.g. thr = 30  p,thr = 4.2 GeV, pK,thr=15 GeV

problem: ring finding in high hit density environment

self-triggered hit detection


feature extraction


each hit transported as

address/ timestamp/ value

Frontend electronics


Buffer pool

extraction of physical signatures

trigger decision



Event builder and selector

DAQ & trigger architechture

  • Requirements

  • efficient detection of rare probes (D, J/y, 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

essential performance limitation not latency but throughput

Feasibility Study: D0

D0 K-p+ (ct=124.4 mm, BR 3.9  0.1%)

Key variable to suppress background: secondary vertex position

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

Feasibility Study: J/y  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 p0 and h, r, misidentified p, ...

very efficient cut on single electron pt, pair opening angle

S/B > 1 should be feasible

Feasibility Study: r, w, f e+e-

branching ratio ~ 4.44 10-5 (r) – 3.1 10-4 (f)

background from various sources: conversion, Dalitz decays of p0 and h, misidentified p, ...

no easy pt-cut as for J/y  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 p misidentification

  • cut on pt, pair opening angle, prim. vertex track

  • S/B 0.5-1

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!

CBM collaboration


RBI, Zagreb


Nikosia Univ.

Czech Republic:

Czech Acad. Science, Rez

Techn. Univ. Prague


IReS Strasbourg


Univ. Heidelberg, Phys. Inst.

Univ. HD, Kirchhoff Inst.

Univ. Frankfurt

Univ. Mannheim

Univ. Marburg

Univ. Münster

FZ Rossendorf

GSI Darmstadt


NIPNE Bucharest


CKBM, St. Petersburg

IHEP Protvino

INR Troitzk

ITEP Moscow

KRI, St. Petersburg

Kurchatov Inst., Moscow




PNPI Gatchina

SINP, Moscow State Univ.


Santiago de Compostela Univ.


Univ. Kiev


KFKI Budapest

Eötvös Univ. Budapest


INFN Frascati


Korea Univ. Seoul

Pusan National Univ.


Univ. Bergen


Jagiel. Univ. Krakow

Silesia Univ. Katowice

Warsaw Univ.

Warsaw Tech. Univ.


LIP Coimbra

CBM time schedule

Milestones: 1. Technical Proposal begin of 2005

2. Technical Design Report end of 2007

experimental conditions

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

CBM R&D working packages



Design & construction

of detectors

Data Acquis.,



Silicon Pixel

IReS Strasbourg

Frankfurt Univ.,

GSI Darmstadt,

RBI Zagreb,

Univ. Krakow

Fast TRD


GSI Darmstadt,

Univ. Münster

INFN Frascati

Trigger, DAQ

KIP Univ. Heidelberg

Univ. Mannheim

GSI Darmstadt


Univ. Bergen

KFKI Budapest

Silesia Univ. Katowice

Univ. Warsaw

,ω, e+e-

Univ. Krakow


Straw tubes


FZ Rossendorf

FZ Jülich

Tech. Univ. Warsaw

D  Kπ(π)

GSI Darmstadt,

Czech Acad. Sci., Rez

Techn. Univ. Prague

Silicon Strip

SINP Moscow State U.

CKBM St. Petersburg

KRI St. Petersburg


GSI Darmstadt,

Heidelberg Univ,

J/ψ e+e-

INR Moscow


ITEP Moscow

GSI Darmstadt

Univ. Krakow


LIP Coimbra,

Univ. Santiago de Com.,

Univ. Heidelberg,

GSI Darmstadt,

Warsaw Univ.

NIPNE Bucharest

INR Moscow

FZ Rossendorf

IHEP Protvino

ITEP Moscow

Hadron ID

Heidelberg Univ,

Warsaw Univ.

Kiev Univ.

NIPNE Bucharest

INR Moscow


IHEP Protvino

GSI Darmstadt



GSI Darmstadt


KIP Univ. Heidelberg

Univ. Mannheim


Acceptance of D0 and J/y



pt [GeV/c]

p misidentification

0 %

0.01 %

0.1 %

1 %

Design of ECAL

  • Design goals of sampling calorimeter:

  • energy resolution of 5/E (%)

  • high-rate capability up to 15 kHz/cm2

  • e/p/(m) discrimination of 25-200

  • total area ~200m2

  • 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


inner region 2x2 cm2

intermediate region 5x5 cm2

outer region 10x10 cm2

Tests of detector module prototype:

July 2004 at CERN