Present and future measurements on
hadronization in strongly interacting
partonic matter at RHIC and RHIC-II.
“It is better to begin in the evening than not at all”
Old English Proverb
Helen Caines
Yale University
DNP Hawaii– Sept. 2005
Particle production in RHI collision
LHC, RHIC-II
SPS, RHIC-I
Soft
0
Parton
recombination
and
coalescence
~ 2 GeV/c
Helen Caines
Medium
modified
fragmentation
(jet quenching)
~ 6 GeV/c
DNP Hawaii – Sept. 2005
Fragmentation
~ 30 GeV/c ?
pT
2
Reaching the fragmentation regime
QM’05
RAA flat for pT > 5 GeV
Same RCP for pT>~5 GeV
Dominance of fragmentation pT > 5 GeV/c - medium modified
Helen Caines
DNP Hawaii – Sept. 2005
3
Calculated fragmentation functions
C. Bourrely and J. Soffer, PRD 68 (2003) 014003
Parton fragmentation functions
to p and  vary as function of z
If energy loss in medium
different for light and heavy
quarks will see differences in pp and A-A
z
z
Au-Au not enough - Need measurements in p-p
Helen Caines
DNP Hawaii – Sept. 2005
4
First “direct” look at medium modification
QM’ 05
1/Ntrig dN/d(Df)
pT(assoc) > 2 GeV/c
Au+Au, 0-5%
STAR Preliminary
8 < pT(trig) < 15 GeV/c
Emergence of the away side
peak with increased trigger pT
Away-side D(zT) suppressed,
shape unchanged
No striking flavor dependence of modification - need PID
Helen Caines
DNP Hawaii – Sept. 2005
5
PID jet correlations
Nch/NTrigger
Au+Au 0-5% 1.0<pTAssociated<2.0
● 50% p/pbar
Near Side
■Λ
□ Λbar
● 95% п
■K0s
pTTrigger
Meson/baryon difference?
Near side – more likely to findp
Away side – find p orp
Need more stats and measure of z
Helen Caines
DNP Hawaii – Sept. 2005
6
Can we do that?
Large acceptance in h and f essential
g tagged jets
Need triggering
pq,g > 10 GeV/c
all h
Multiply pp events by factor of ~ 8 x 1015 for
AuAu events in 30 nb-1 RHIC year
106 particles in AA
Helen Caines
RHIC-II luminosities
essential
DNP Hawaii – Sept. 2005
7
Comprehensive new detector at RHIC (R2D)
HCal and m-detectors
Central detector (|h|  3.4)
HCal and m-detectors
Superconducting coil (B = 1.3T)
Forward tracking:
2-stage Si disks
EM Calorimeter
Forward magnet
(B = 1.5T)
Vertex tracking
RICH
PID:
RICH
ToF
Aerogel
Helen Caines
ToF
Aerogel
h = 1.2 – 3.5
Tracking:
Si, mini-TPC(?),
m-pad chambers
Forward spectrometer:
(h = 3.5 - 4.8)
RICH
EMCal (CLEO)
HCal (HERA)
m-absorber
SLD magnet
|h|  1.2
6m
DNP Hawaii – Sept. 2005
8
Detector coverage
PID
Hadronic and EM Calorimetry:
η = +/- 3.4
Tracking: η = (-3.5 – +4.5)
PID: h = +/- 1.2 (2.8)
RICH : C5F12 - n = 1.00175
PID (p, K, p)
dE/dx, ToF
A1+ToF
1.
2.
Helen Caines
3.
A1+A2+RICH
4.
5.
6.
7.
RICH
8.
9.
10
12.
DNP Hawaii – Sept. 2005
14.
16
18.
p (GeV/c)
9
Summary
The New Comprehensive Detector designed for the
new era of UNIQUE physics at RHIC-II :
♦
♦
♦
♦
♦
High rates
Large acceptance
High pT tracking
PID out to high pT
Good momentum resolution
Large program of measurements for RHIC-II era
 Understand medium produced via jets/leading particle
 New (as yet) undetermined physics
Helen Caines
DNP Hawaii – Sept. 2005
10
Requirements for an Ideal Detector
• High rate detectors, DAQ
– Required for high luminosity A+A, p+A and p+p collisions at RHIC II
• Uniform high magnetic field over “large volume”
– Good quality tracking/momentum measurements
• Precision Vertex tracking
• 4p EM and Hadronic Calorimeters
– Missing energy measurements and m identification
• e/h discrimination
– At low pT as well as at high pT
 p/K/p identification
– Momentum up to ~ 25 GeV/c
• Forward capabilities
– High-rapidity measurement/identification possibility
Helen Caines
DNP Hawaii – Sept. 2005
11
Geometrical Dependence of RAA
• RAA scales smoothly
Helen Caines
DNP Hawaii – Sept. 2005
See poster, van Leeuwen (91)
12
Can’t rely too heavily on NLO calculations
p+p->p0 + X
Work for light mesons
don’t work for heavy baryons
Helen Caines
DNP Hawaii – Sept. 2005
13