T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Nucleon Structure and Quark-Gluon-Plasma:
HERMES and ALICE/STAR
Thomas PeitzmannUtrecht University/NIKHEF
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Outline
• HERMES– fragmentation in nuclei
• STAR – elliptic flow– jet physics
• ALICE– silicon strip detector– analysis preparations
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
NIKHEF Research programs
LHCb& Babar
ATLAS& D0
ALICE& STAR
Antares
Theory
R&D
GRID
OutreachLEP
HERA ~16 M€ per annum excluding investments
2005
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
HERMES• HERA/DESY• investigate spin structure of the nucleon– DIS with polarized leptons on polarized hydrogen target
• fragmentation in the nucleus– lepto-production of hadrons off nuclei
hardware contribution from NIKHEF: Lambda wheels
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
HERMESspin decomposition
Analysis highlights:
• N spin decomposition• hyperon production• transversity
PhDs:
• 10 completed• 7 now @ institutes abroad
• +5 in preparation
Publications:
• expect ~100 by 2007
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Absorption/Energy Loss in Nuclei?
• production of hadrons in nuclei vs deuterium
• significant suppression of large z hadrons in heavy nuclei– absorption?– energy loss?
RM
h z,n( ) =Nh z,n( ) Ne n( )( )
A
Nh z,n( ) Ne n( )( )D
n>7GeV
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Fragmentation in the Nucleus?
• ratio of di-hadron to single hadron for different nuclei
• very little dependence on mass of nucleus
• important reference measurement for heavy ion collisions
R2h z2( ) =
N2h z2,z1( ) N1h z1( )( )A
N2h z2,z1( ) N1h z1( )( )D
z1 > 0.5
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
ALICE/STAR
• 7 PhD – 4 STAR, 3 ALICE
• 45 publications – STAR from 2002 up to now
• group will shift completely to ALICE in the near future
• part of one FOM programme
• ALICE at LHC/CERN– hardware contribution: silicon strip detector
– data taking from 2007
• STAR at RHIC/BNL– joined in 2002– data taking and analysis
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
QCD phase diagram• QCD predicts transition from hadronic phase to a quark-gluon-plasma– Tc ≈ 160-170 MeV– order of transition unknown (but much larger number of d.o.f.)
– deconfinement and chiral symmetry restoration
• studied in high-energy heavy ion collisions
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
The focus of our group• The properties of the QCD Equation of State
above Tc – dp/d calculable in lattice QCD – observables: collective motion of low transverse momentum particles as function of mass
• The color density of hot and dense QCD matter– induced soft gluon radiation by partons traversing the medium
– observables: medium modifications of jets and heavy particle production
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
The STAR DetectorMagnetMagnet
CoilsCoils
Central Central TriggerTriggerBarrel Barrel (CTB)(CTB)
ZCalZCal
Time Time Projection Projection
ChamberChamber(TPC)(TPC)
Year 2000Year 2000
Barrel EM Cal Barrel EM Cal (BEMC)(BEMC)
Silicon Vertex Silicon Vertex Tracker (SVT)Tracker (SVT)Silicon Strip Silicon Strip Detector (SSD)Detector (SSD)
FTPCFTPCEndcap EM CalEndcap EM CalFPDFPD
TOFp, TOFrTOFp, TOFr
FPDFPD
Year 2001+Year 2001+
PMD
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Elliptic flow
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Collective motion: velocity of sound
• buildup of collective flow depends on the magnitude of the velocity of sound and the relative time spend in various phases
• sensitive to difference in equation of state (EoS)
P.F. Kolb and U. Heinz, in Quark Gluon Plasma, nucl-th/0305084
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Self-quenching of elliptic flow
• the driving force of elliptic flow (anisotropy of pressure gradient) dominates at “early” times
• elliptic flow “monitors” early collective (i.e. equilibrated) behaviour
P.F. Kolb and U. Heinz, in Quark Gluon Plasma, nucl-th/0305084
Measurement of elliptic flow
• asymmetry of number distribution of particles with respect to the reaction plane
• Fourier-decomposition:
strong 2. order (v2)
• early result from STAR: strength of elliptic flow reaches predictions of ideal hydrodynamics at RHIC
STARcharged hadrons
ideal hydrodynamics
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Identified particle flow• hierarchy of momentum dependent flow for different hadrons– onset of v2 shifts to larger pT for heavier particles
– consistent with ideal hydrodynamics
– magnitude of difference not consistent with hadron gas, but with QGP
parallel talk by Bai Yuting
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Jets and jet quenching
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Parton energy loss: current understanding
• collisional energy loss– original idea by Bjorken
– very small effect
• more important:induced gluon radiation
• interference leads to non-linearity
• dominant feature:– energy loss determined by density of color charges• parameterized by transport coefficient
DE ª
CR
4aS ◊q ◊L2
q =
kT2
lµ r glue
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
p+p dijet+X
Au+Au ???
Measuring jets in AA?
(STAR@RHIC)
how to find this in here?
two observables: - high pT single hadron distributions- dihadron distributions
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Inclusive Hadron Suppression
• nuclear modification factor
• suppression requires initial density 30x larger than cold nuclear matter– compare to HERMES results
• very close to maximum suppression– provides only lower bound on density
q 5
GeV2
fm
Eskola et al., hep-ph/0406319
q = 0 GeV2 fm
q = 1GeV2 fm
q = 5- 15 GeV2 fm
RAA ∫
d 2N AA dydpT
d 2N pp dydpT ◊ NcollAA
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Surface emission
• large energy loss: opaque core– emissions from surface
• inclusive measurements insensitive above certain density– more information from correlation measurements?
?Eskola et al., hep-ph/0406319
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Dihadrons in heavy ion collisions
• near-side correlation unchanged
• away-side peak suppressed in central Au+Au– consistent with surface emission
• distributions in d+Au similar to p+p– suppression is final state effect
• more intuitive hint for “jet” suppression, but quantitatively much more difficult
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Emergence of away-side peak
pT(trig)
pT(assoc) > 2 GeV/c
STAR Preliminary
Au+Au, 0-5%
High statistics year 4 dataset allows increase in Q2
Emergence of the away side peak with increased trigger pT
Equivalent to year 2 analysis
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Emergence of dijets
increase associated pT threshold also:
clear jet-like peaks seen on near and away side in central Au+Au collisions!
yields info on upper and lower limit of density!
8 < pT(trig) < 15 GeV/c
STAR Preliminary
pT(assoc)>6 GeV
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Where does the energy go?
Leading hadrons
Medium
significant softening of associated hadrons!
mean pT of away-side associated hadrons= remaining jet fragments?
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
The perfect fluid at RHIC, the wQGP at the LHC?
wQGP = weakly-interacting plasma
less flow at higher energies?beware: remember the predictions for RHIC!
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Elliptic flow at LHC energies from ideal
hydrodynamics
• Whatever the outcome will be, elliptic flow is a day-one measurement at the LHC with very likely similar impact as at RHIC
From Heinz, Kolb, Sollfrank
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
ALICE: the dedicated HI experiment
Solenoid magnet 0.5 T
Central tracking system:• ITS •TPC• TRD• TOF
MUON Spectrometer:• absorbers• tracking stations• trigger chambers• dipole
Specialized detectors:• HMPID• PHOS
Forward detectors:• PMD• FMD, T0, V0, ZDC
Cosmic rays trigger
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
The Alice ITS
•FE moduleFE module
•EndcapEndcap
•FEROMFEROM
•DAQDAQSSD
•Support Support and coolingand cooling
•Main vertex 15 µm in central PbPb
•Vertex charm, strange decays 50 µm
•Δp/p (pT>1 GeV, with TPC) 14%->3%
•Particle ID (dE/dx)
•Strong contribution to outer layers (SSD)
•project leader SSD (6 labs)
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
SSD: the first real ladder!
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
NIKHEF/UU ALICE hardware activities (SSD)
• Design of SSD support (with Turin)• Design ladder frames (with St. Petersburg)• Design of SSD cooling system (with CERN)• Design of front-end modules (with Kharkov and Strasbourg)• Design ladder cabling (with Kharkov)
• Design SSD cabling (industrial production)• Design and production of front-end module test equipment• Design and production of EndCap electronics• Design and production of read-out modules
• Ladder assembly (with Nantes)• Final SSD assembly
• Bottom line: ITS project on schedule and NIKHEF SSD contribution will finish on time (2006)
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
ALICE group: current manpower
• Utrecht and NIKHEF Amsterdam• Amsterdam manpower:
– Staff physicist: 3 – PhD students: 2
• Utrecht manpower:– Staff physicist: 4– Post-doc: 1– PhD students: 5– Students: 2
• Amsterdam infrastructure:– Mechanical and electronics workshop– Ladder assembly room
• Utrecht infrastructure:– Faculty mechanical and electronics workshop– Mechanical and electronic workshop of the SAP department (4
fte)– Assembly room
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
ALICE group: current physics activities• Have strong role in STAR EMC analysis
– 1 fte staff, 1 post-doc, 3 PhD's (until 2009) and 2 students
• Had a leading role in correlation analysis with the reaction plane in STAR– Effort is scaled down to 1 PhD (until 2007) and 0.2 fte staff
• Have a coordinating role in correlation analysis with the reaction plane in ALICE (Physics Performance Report)– Effort 4 fte staff and 2 PhD – Will increase further with 3 PhD’s and 1 post-doc
T. Peitzmann, NUPECC Groningen, Nov. 18, 2005
Summary
• important nuclear physics contributions from NIKHEF– HERMES with nuclear physics program in parallel to spin
– ALICE/STAR nuclear physics at the highest energies
• rich physics harvest from STAR– elliptic flow– jet quenching
• ALICE well under way for data taking in 2007– strong Dutch contribution to SSD
– prepare physics analysis• elliptic flow as day-one topic