The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt

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?


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


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!


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)]


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)]


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.


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) ]


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


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)]


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


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!


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


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


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]


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!)


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)


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


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


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


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)


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


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


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


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


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


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

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


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


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


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


Acceptance of D0 and J/p

t [G

eV

/c]

D0 J/ψ


misidentification

0 %

1 %0.1 %

0.01 %


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


FAIR @ GSI

The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt

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