View
212
Download
0
Category
Preview:
Citation preview
The long-range pseudo-rapidity correlations in high-energy collisions
王福强Purdue University
Proton, neutron, meson (hadron)Quark Gluon Plasma (QGP)
The Big Bang and the Little Bang
7/1/2013 2
Nuclear Phase Diagram
7/1/2013 3
Heavy-Ion Collisions simulationHadron cascade
7/1/2013 4
CMSSTAR
ALICE
7/1/2013 5
PHENIX
Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL)
STAR and PHENIX experiments
New York BNL- RHIC
7/1/2013 6
7
Two types of discoveries
• Theoretically predicted, and experimentally verified, e.g.– J/Y– W, Z bosons
• Surprises, e.g.– Parity violation– Microwave background radiationLong-range pseudo-rapidity correlations
7/1/2013
Variables, observables
g = 100
13 fm
STAR: Solenoidal Tracker At RHICy
x
f
1ln
2
ln tan2
z
z
p p
p p
qz
ppT
pz
7/1/2013
x
y z
coordinate space anisotropy
py
px
momentum space anisotropy
Hydrodynamic bulk collectivity, elliptic flow
- 0 p p fparticle-FR.P. (rad)
7/1/2013 9
Collective expansion of QGP- elliptic (2nd order) and higher order event anisotropic collectivity and its Nquark scaling - hydro-dynamic properties of QGP
PHENIX Preliminary, QM12
7/1/2013 10
Elliptic expansion during the partonic (quark-gluon) phaseHadron formation via quark recombination / coalescence
Hadron
7/1/2013 11
jet
p p
Au Au
Energy loss (jet quenching) in QGP
Phys. Rev. Lett. 91, 072304 (2003) PRL109, 152302 (2012)arXiv: 1208.2254
central Au+Au
gq
7/1/2013 12
13
Novel phenomena in heavy-ions
• Double-peak away-side correlations• Odd harmonics• Long-range ridge correlations• Ridge in small systems• …
Au+Au ridge
Df Dh
7/1/2013
14
Jet Correlations
Jet event in e+e- collision STAR Au+Au collision
Jet produces high pT particles Select a high pT particle to trigger on jet.NB: trigger = off-line trigger
Df
trigger particlepT > 3 GeV/c
associatedparticle
7/1/2013
15
Dihadron correlationsSTAR, PRL 95 (2005); PRC82 (2010)
STAR, PRL91 (2003)
• Clear evidence of jet-quenching, and it’s a final-state effect
• Low pT enhancement and broadening• Away-side double peak; Large-Dh small-Df
ridge correlation• v2 subtracted but not higher harmonics
Away-side
triggerjet
0 p1-1 Df
pTtrig=4-6 GeV/c
pTassoc=0.15-4 GeV/c
7/1/2013
16
Relative to the Event Plane
• Ep-dep correl
7/1/2013
v2max {2,hgap=0.7}
v2max{2,hgap=0.7}, v3{2,hgap=0.7}
STAR, arXiv:1010.0690v1Todoroki (PHENIX) 1304.2852Trigger
Associated
Df
EPfS
• Evolution of structure seems to remain from in-plan to out-of-plane.• Single away-side peak in-plane, double-peak out-of-plane.• Jet interactions with QGP medium. Physics mechanisms?
|Dh| > 0.7
17
Three-particle correlations
• v2 and v4 subtracted.
• Does v3 remove all of the off-diag. peak strength? Need further study.
• Deflected jets contributions (to diag. peaks) must be present.
• Need to be followed up with v3 subtraction.
7/1/2013
Δ1
Trigger
Δ2
18
Df
trigger particlepT > 3 GeV/c
assoc. particlepT =1-2 GeV/c
d+Au
Au+Au ridge
Df Dh
The longitudinal ridge
h ~ 1h ~ 0
trigger particlepT > 3 GeV/c
Dh
assoc. particlepT =1-3 GeV/c
||
<0.7
7/1/2013
19 / 37
Ridge vs trigger anglev2
max {2,hgap=0.7}
v2max{2,hgap=0.7}, v3{2,hgap=0.7}
Df Dh7/1/2013
20 / 37
Ridge yield vs trigger anglev2
max {2,hgap=0.7}
v2max{2,hgap=0.7}, v3{2,hgap=0.7}
Subtractv3
7/1/2013
LHC-CMS
usual p-p collision high multiplicity p-p collision
7/1/2013 21
Ridge in small systems
22
• Why wasn’t it discovered long ago by HEP?
• Two types of discoveries: – Theoretically predicted, and experimentally verified– Surprises
• HEP moved on to more exclusive processes
• There may be still important physics that were missed in last half century.
7/1/2013
p-p collision (high Mul.)p-Pb collision (high Mul.)
7/1/2013 23
Physical origin unclear
24
CGC/Glasma
Dusling & Venugopalan 1211.3701
Dusling and Venugopalan, arXiv:1302.7018
7/1/2013
25
Another explanation: Hydro flow• In heavy-ions, large Dh small Df correlations:
subtract v2 non-zero finite correlation (ridge)
• In pp, pA, dA systems, large Dh small Df correlations:subtract flat pedestal non-zero finite correlation (ridge)
7/1/2013
26
d+Au ridge?
• Jet contribution within PHENIX acceptance• LHC+RHIC more stringent test on theoretical models.
7/1/2013
PHENIX, arXiv:1303.1794
1.25-1.5 GeV/c
Bozek, PRC85 (2012)
PHENIX acceptance
27
Straight differenceNo ZYAM involved
STAR PRELIMINARY STAR PRELIMINARY
Df projections in different Dh (TPC mult. |h|<1 as centrality)
• ZYAM syst. error from different sizes of Df region for ZYAM.• Efficiency corrected: 85 ± 5% .
0.15 < pTtrig < 3 GeV/c, 1 < pT
assoc < 2 GeV/c
ZYAM-edSTAR PRELIMINARY STAR PRELIMINARY
ZYAM-edSTAR PRELIMINARY
ZYAM-ed
STAR PRELIMINARY
7/1/2013
28
Dh projections in different Df (TPC mult. |h|<1 as centrality)
• ZYAM syst. error from different sizes of Df region for ZYAM.• Efficiency corrected: 85 ± 5% .
STAR PRELIMINARY STAR PRELIMINARY
ZYAM-edSTAR PRELIMINARY
ZYAM-edSTAR PRELIMINARY
0.15 < pTtrig < 3 GeV/c
1 < pTassoc < 2 GeV/c
7/1/2013
29
Central – Peripheral
• ZYAM syst. error from different sizes of Df region for ZYAM.• Efficiency corrected: 85 ± 5% .
0.15 < pTtrig < 3 GeV/c, 1 < pT
assoc < 2 GeV/c
FTPC 0-20% - 40-100%
STAR PRELIMINARY
TPC 0-20% - 50-80%
STAR PRELIMINARY
TPC 0-20% - 50-80%
STAR PRELIMINARY
TPC 0-20% - 50-80%
STAR PRELIMINARY
Minimalridge
7/1/2013
30
Very forward correlations
7/1/2013
31
TPC-FTPC correlations
Dh triangle acceptance
7/1/2013
32
Sanity check
4 23 20
2( .) 2acc
3 22 20
2( .) 1acc
3 20.5 5
2( .) 1acc
PHOBOS, PRC 72 (2005) 031901(R)
TPC-FTPC
TPC-TPC
All charged hadrons
7/1/2013
33
ZYAM’ed Dh Correlations(TPC mult. as centrality)
Discontinuity because it’s Dh not h distribution.At Dh=2, TPC-TPC and TPC-FTPC pairs come form different h’s.
Raw correl.
ZYAM’ed
7/1/2013
34
Fourier fit results
TPC-TPC Au-side TPC-TPC d-side
TPC-FTPC d-sideTPC-FTPC Au-side
7/1/2013
35
Fourier fit results (replot of previous slide)
Summary• Correlations have v1 and v2 components• v1 appears ~1/N. v2 ~constant over multiplicity• Even at very forward d-side, v2 component is large (maybe even larger than Au-
side).• Not sure what the data mean.
Au-side d-side
7/1/2013
36
Conclusions
• Particle correlations in heavy-ions– Novel phenomenon of v3– After v3 subtraction, features of jet-medium
interactions remain
• Ridge in small systems– Intriguing– May contain important physics
7/1/2013
37
The question of v1
• In the pt=1-2 GeV/c region, directed flow fluctuation effect may be negligible.
Pandit (STAR), arXiv:1211.7162
7/1/2013
38
Have to rethink about inclusive dihadron• We have used so far <vt{2}*va{2}>=<vt{2}>*<va{2}>. This is OK because fluctuations
are already included in v{2}.• However, if v{2} depends on slice, then <vt{2}slice*va{2}slice><vt{2}slice>*<va{2}slice>.
• <vt{2}slice*va{2} slice> = (vt{2}1*va{2}1 + vt{2}6*va{2}6)/2 = (vt{2}1*va{2}1 + vt{2}6*va{2}1 - vt{2}6*va{2}1 + vt{2}6*va{2}6)/2 = <vt{2}>*va{2}1 - vt{2}6* (va{2}1 - va{2}6)/2 > <vt{2}>*va{2}1 which is the maximum.
7/1/2013
39
ZYAM’ed Dh Correlations(ZDC as centrality)
7/1/2013
Recommended