mit at the lhc - university of adelaide...analyzing hi collisions: 2-particle correlations...
TRANSCRIPT
Recent results from relativistic heavy ion collisions at the LHC
Camelia MironovMIT
A ‘teaser’ talk with very few (though recent) results
Collision systems
Center of mass colliding energy (TeV)
2.76 (2011, 2013)5.02 (2015)7,13
—5.02 (2013)
2.76 (2010, 2011)5.02 (2015)
LHC Heavy-Ion (HI) Program
2
Characterize HI collisions
➡ ‘Event-activity’ characteristics (Data, Monte Carlo)✓ central collisions: small impact parameter collision (high-multiplicity
events, large energy deposited in calorimeters, etc)✓ peripheral collision: large impact parameter collision
➡ At a certain colliding energy, for a certain impact parameter b✓ <Npart> — number of incoming nucleons participating in the collision✓ <Ncoll> — number of equivalent nucleon-nucleon collisions
- Glauber MC calculation3
5
4
A → ←A
➡ Particle production✓ transverse momentum: component perpendicular on the beam axis
- pT = p cosθ
✓ pseudorapidity: angular position in detector
Characterize HI collisions
4
⌘ = �ln[tan(✓/2)]
(GeV)NNs10 210 310 410
⟩η/d
chNd⟨ ⟩
part
N⟨2
0
2
4
6
8
10
12
14), INELppp(p AA, central
ALICE ALICECMS CMSUA5 ATLASPHOBOS PHOBOSISR PHENIX
BRAHMSpA(dA), NSD STARALICE NA50PHOBOS
| < 0.5 η|
0.103(2)s ∝
0.155(4)s ∝
LHC vs RHIC
➡ The charged particle multiplicity per colliding nucleon pair measured at LHC for the most central collisions is ✓ ~2x that measured at RHIC, where the collision energy is factor 14 lower✓ ~2x that measured at LHC in pp or pPb collisions at similar collision energy
5
PRL 116 (2016)
Ini$al-stateinhomogeneity
ΨEP
x
y
Ini$al-stateanisotropy
Ψ2
Ψ3
Analyzing HI collisions: 2-particle correlations
➡ Event-by-event
6
Trigger particlepTtrig,ηtrig, φtrig
Associated particlepTasssoc,ηassoc, φassoc
Δη = ηtrig - ηassoc
ΔΦ = φtrig - φassoc
η∆-4-2
02
4
φ∆ 02
4
φ∆
dη∆d
pair
N2 d
trig
N1 0.160.180.20
< 35trkoffline = 5.02 TeV, NNNsCMS pPb
< 3 GeV/cT
1 < p(a)
η∆-4
-3-2
-10
12
34
(radians)
φ∆
-1
0
1
2
3
4
φ∆
dη
∆d
pair
N2 d
trig
N1 0.14
0.16
0.18
< 35offline
trk = 13 TeV, NsCMS pp
< 3 GeV/cT
1 < p(a)
Back-to-back jet contribution
Single jet contribution
Collective motion: 2-particle correlations
7
Single jet contribution
Back-to-back jet contribution
JHEP 09 (2010)
RIDGE: “collective effect” 2 particles with very different η are “connected”
Collective motion: 2-particle correlations
8
RIDGE: “collective effect” 2 particles with very different η are “connected”
Single jet contribution
Back-to-back jet contribution
RIDGE Also in pPb high-multiplicity events
η∆-4
-2
0
2
4 (radians)
φ∆
0
2
4
φ∆
dη∆d
pair
N2 d
trig
N1 3.1
3.2
3.3
3.4
< 260offlinetrk N≤ = 5.02 TeV, 220 NNs(b) CMS pPb
< 3 GeV/ctrigT
1 < p < 3 GeV/cassoc
T1 < p
PLB 718 (2013)
JHEP 09 (2010)
Collective motion: pPb
9arXiv:1606.08170
PLB 718 (2013) PLB 719 (2013)
arXiv:1512.00439
ALICE
η∆-4
-2
0
2
4 (radians)
φ∆
0
2
4
φ∆
dη∆d
pair
N2 d
trig
N1 3.1
3.2
3.3
3.4
< 260offlinetrk N≤ = 5.02 TeV, 220 NNs(b) CMS pPb
< 3 GeV/ctrigT
1 < p < 3 GeV/cassoc
T1 < p
Collective motion everywhere!
10
RIDGE: “collective effect” 2 particles with very different η are “connected”
Single jet contribution
Back-to-back jet contribution
RIDGE Also in pp high-multiplicity events
η∆4−
2−
0
2
4
(radians)
φ∆
0
2
4
φ∆
dη
∆d
pair
N2 d
trig
N1 1.65
1.70
1.75
= 13 TeVsCMS pp < 150offline
trk N≤105 < 3 GeV/cassoc
T, ptrig
T1 < p
± - h±h
η∆4−
2−
0
2
4
(radians)
φ∆
0
2
4
φ∆
dη
∆d
pair
N2 d
trig
N1 1.70
1.75
1.80
± - h0SK
η∆4−
2−
0
2
4
(radians)
φ∆
0
2
4
φ∆
dη
∆d
pair
N2 d
trig
N1 1.60
1.65
± - hΛ/Λ
JHEP 09 (2010) CMS-PAS-FSQ-15-002 ATLAS-CONF-2016-026
LHC: PbPb @ 2.76, 5.02TeV
11
Z
l+l-
h/D/Binclusive jet / identified-jet
inclusive jet / identified-jetZ
l+l-
inclusive jet
A) Individual hadrons B) Reconstructed jets
r0,ΔE
C) Quarkonia
➡ Questions one addresses with these measurements✓ Is there a difference in how the light partons and heavy (charm and
beauty) quarks interact with the medium?✓ What are the properties of the medium created?
Analyzing HI collisions: RAA
➡ Nuclear modification factor:✓ if = 1 no medium effects✓ if < 1 suppression (e.g. energy loss in the medium)✓ if > 1 enhancement (e.g. kT broadening in the incoming nuclei)
12
RAA
=Y ield(A+A)
Y ield(p+ p) < Ncoll
>
Z boson: in-situ reference
➡ Z boson measured for the first time in HI collisions✓ confirm the Ncoll scaling: RAA = 1
13
partN0 50 100 150 200 250 300 350 400
AAR
0
0.5
1
1.5
2
2.5 = 2.76 TeVNNsCMS
> 0 GeV/cT
ll, |y| < 1.44, p→Z ll, 0-100% centrality→Z
pp luminosity uncertainty
JHEP 03 (2015PRL 110 (2013)
Z
l+l-
Charged hadrons (gluons & u/d/s quarks)
➡ Agreement between experiments at 2.76TeV➡ And same suppression at 2.76TeV and 5TeV
14
(GeV)T
p1 10 210
AAR
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0-5%
and lumi. uncertaintyAAT|<1η|
(5.02 TeV PbPb)-1bµ (5.02 TeV pp) + 404 -125.8 pb
CMSPreliminary
CMS 5.02 TeVCMS 2.76 TeVATLAS 2.76 TeVALICE 2.76 TeV
CMS-PAS-HIN-15-015
h
)2 (GeV/cKπm1.7 1.75 1.8 1.85 1.9 1.95 2
)2En
tries
/ (5
MeV
/c
0
20
40
60
80
100
120
140
160
180
200
220DataFit
Signal0D+0D swappedπK-
Combinatorial
PreliminaryCMS = 5.02 TeVNNsPbPb
< 30.0 GeV/cT
25.0 < p
Centrality 0-100%
|y| < 1.0
D mesons (charm quarks)
15
K
π
D0
D0 decay vertex
Primary
JHEP 09 (2012) CMS-PAS-HIN-16-001
D
Charm vs Light
➡ At high-pT (~4-5GeV/c) light partons (quarks and gluons) and charm quarks ‘products’ have same RAA
16
(GeV/c)T
p1 10 210
AA R0 D
0
0.2
0.4
0.6
0.8
1
1.2
1.4
(5.02 TeV PbPb)-1bµ (5.02 TeV pp) + 404 -125.8 pb
CMSPreliminary
Centrality 0-100%|y| < 1
0 DAAR
charged hadronsAAR and lumi.AAT
uncertainty
2.76 TeV 5.02 TeV CMS-PAS-HIN-16-001 CMS-PAS-HIN-15-015
JHEP 03 (2016)
B(J/𝜓X) mesons (beauty quark)
➡ First b-quark products measurement✓ B→J/𝜓+X
➡ First exclusive B reconstructed in pA collisions✓ B→J/𝜓+K17
(mm)ψJ/l-1 -0.5 0 0.5 1 1.5 2
Even
ts /
(0.0
35 m
m)
1
10
210
310
410CMS Preliminary
= 2.76 TeVNNsPbPb -1bµ = 150 intL |y| < 2.4
< 30 GeV/cT
6.5 < pCent. 0-100%
datatotal fitbkgd + non-promptbackground
BLxy
J/ψ µ+µ−
�J/� = LxymJ/�
pT
B+ Decay Vertex
J/ψ
B+ cτ = 492 µm
µ+
µ-
K+
m = 3.10 GeV/c2
)2 (GeV/cµµm2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5
)2Ev
ents
/ ( 0
.02
GeV
/c
0
500
1000
1500
2000
2500
3000
CMS Preliminary = 2.76 TeVNNsPbPb
-1bµ = 150 intL|y| < 2.4
< 30 GeV/cT
6.5 < pCent. 0-100%
177±: 8525 ψJ/N2 1 MeV/c± = 35 σ
datatotal fitbkgd + non-promptbackground
)2 (GeV/cBm5 5.2 5.4 5.6 5.8 6
)2En
tries
/ (2
0 M
eV/c
0
50
100
150
200
DataFitSignalCombinatorial
Xψ J/→B
(pPb 5.02 TeV)-134.6 nbCMS
-+B+B < 15 GeV/c
T10 < p
| < 2.4lab
|y
)2 (GeV/cBm5 5.2 5.4 5.6 5.8 6
)2En
tries
/ (3
0 M
eV/c
0
10
20
30
40
50
60
70
DataFitSignalCombinatorial
Xψ J/→B
(pPb 5.02 TeV)-134.6 nbCMS
0B+0B < 15 GeV/c
T10 < p
| < 2.4lab
|y
)2 (GeV/cBm5 5.2 5.4 5.6 5.8 6
)2En
tries
/ (4
0 M
eV/c
0
10
20
30
40
50
60
70
DataFitSignalCombinatorial
(pPb 5.02 TeV)-134.6 nbCMS
0sB+0
sB < 60 GeV/c
T10 < p
| < 2.4lab
|y
CMS-PAS-HIN-12-014
PRL 116 (2016)
Beauty vs Charm vs Light
➡ Smaller measured suppression between the b-quark products and charm or gluon/light-quarks products
18
B→J/𝜓
D, h
JHEP 11 (2015)
Fully reconstructed jets
19… in the kinematic regions where we can
Z+jet: in-situ reference
➡ Central PbPb xJZ distributions shifted to lower values wrt pp at all Z-pT : the back-parton suffers energy loss in the medium✓ theoretical models: energy loss directly related to the medium density
20
Z
l+l-
Jet
CMS-PAS-HIN-15-013
-weighted)coll
(N⟩partN⟨0 50 100 150 200 250 300 350 400
⟩ Jx⟨
0.56
0.58
0.6
0.62
0.64
0.66
0.68
0.7
0.72
0.74pp
30-100%
10-30%0-10%
(5.02 TeV PbPb)-1bµ (5.02 TeV pp) + 404 -125.8 pb
CMSPreliminary
Inclusive dijets
Data
pp-based reference
Beauty vs Light
➡ Blue: Inclusive-dijets imbalance increases from peripheral to central PbPb collisions➡ Red: Imbalance of b-dijets measured for the first time
✓ similar to that of inclusive jets (red vs blue)21
-weighted)coll
(N⟩partN⟨0 50 100 150 200 250 300 350 400
⟩ Jx⟨
0.56
0.58
0.6
0.62
0.64
0.66
0.68
0.7
0.72
0.74pp
30-100%
10-30%0-10%
(5.02 TeV PbPb)-1bµ (5.02 TeV pp) + 404 -125.8 pb
CMSPreliminary
b dijets
Data
pp-based reference
Jet 2
Jet 1
b-Jet 2
b-Jet 1CMS-PAS-HIN-16-005
xJ =p
Jet2T
p
Jet1T
pJet2T > 40GeV/c
pJet1T > 100GeV/c
LHC: the full picture
➡ Probes ‘blind’ to the medium: photons, Z, W➡ Probes affected by the medium:
✓ low-pT: different suppression pattern for b-quark vs c/q/gluon products✓ high-pT: similar suppression pattern no matter the color of the pattern
22
) [GeV]T
(mT
p0 20 40 60 80 100
AAR
0
0.5
1
1.5
2
2.5
| < 1ηCharged particles (0-5%) | (0-100%) |y| < 2.4ψ J/→*B
*Z (0-100%) |y| < 2| < 2.1µη, | > 25 GeV/cµ
TW (0-100%) p
| < 1.44ηIsolated photon (0-10%) |
[GeV]T
p100 150 200 250 3000
0.5
1
1.5
2
2.5 = 2.76 TeVNNsCMS *PRELIMINARY PbPb
-1bµ L dt = 7-150 ∫| < 2η*Inclusive jet (0-5%) |
| < 2η*b-jet (0-10%) |
Photons, W, Z
h , B→J/𝜓 Inclusive jet, b-jet!, h , D
Quarkonia
➡ Onia in a deconfined partonic medium: color screening at different medium temperatures for different states (depending on binding energy) ✓ sequential melting/destruction of the states
➡ Onia: thermometer of the medium
23
A. Mocsy Eur.Phys.J.C61,2008
T
r0,ΔE
partN0 50 100 150 200 250 300 350 400
AAR
0
0.2
0.4
0.6
0.8
1
1.2
1.4 = 2.76 TeVNNsCMS PbPb -1bµ = 150 PbPb
intL-1 = 230 nbpp
intL
0-5%5-10%10-20%
20-30%
30-40%
40-50%
50-100%
(1S)ϒ
(2S)ϒ
(3S), 95% upper limitϒ
0 0.5 1
AAR
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0-100%
Sequential melting: ϒ(1S, 2S, 3S)
➡ Sequential melting (proposed as key proof for existence of a QGP), first experimental proof of color screening picture
24
A. Mocsy Eur.Phys.J.C61,2008
T
RAAΥ(1S) > RAA
Υ(2S) > RAAΥ(3S)
PRL 109 (2012)
(GeV/c)T
p0 5 10 15 20 25 30
AAR
0
0.2
0.4
0.6
0.8
1
1.2
1.4 CMS Preliminary = 2.76 TeVNNsPbPb
Cent. 0-100%|y| < 2.4
ψPrompt J/
Quarkonium phenomena: J/𝜓
➡ Experimental confirmation of (old) theoretical ideas
25
Regeneration Parton/jet fragmentation and en loss
Low-pT
High-pT
Puts back some QQbar Destroys and/or shifts the kinematics via partonic/hadronic interactions
CMS-PAS-HIN-12-014JHEP 05 (2016)
pp, pPb, PbPb
➡ Sequential patterns also in pp & pPb✓ not clear whether it was the “medium” affecting the states (as in PbPb),
or the state affecting the “medium”26
JHEP 04 (2014)
|<2.4η|tracksN
10 210 310
(1S)
ϒ(2
S)/
ϒ
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
CMS
= 2.76 TeVNNspp
| < 1.93CM
|y
= 5.02 TeVNNspPb
| < 1.93CM
|y
= 2.76 TeVNNsPbPb
| < 2.4CM
|y
(1S)ϒ(2S)ϒ
0 < pT < 20 GeV/c
Low Track Multiplicity
High Track Multiplicity
|<2.4η|tracksN
0 20 40 60 80 100 120 140
(1S)
Υ(2
S)/
Υ
0
0.1
0.2
0.3
0.4
0.5(1S)Υ(2S)/Υ
)-1< 5 GeV (0.3 fbT
p≤0
)-1< 7 GeV (1.9 fbT
p≤5 < 9 GeV
T p≤7
< 11 GeVT
p≤9
< 13 GeVT
p≤11
< 18 GeVT
p≤13
< 25 GeVT
p≤18
50 GeV≤ T
p≤25
(7 TeV)-14.8 fbCMSPreliminary
)|<1.2µµ(y|
pp@7TeV
➡ Decrease of the excited/ground state ratio confirmed at 7TeV➡ The ratio decreases strongly at lower pT
✓ in PAS: stronger indications that it is not the state affecting the “medium”27
CMS-PAS-BPH-14-009
25 < pT < 50 GeV/c
0 < pT < 5 GeV/c
Low Track Multiplicity
High Track Multiplicity
LHC heavy-ions: Summary➡ Precision, Diversity and Surprises
✓ Precision: - charged hadrons measured up to 400GeV/c- separate measurements of charm & beauty quarks products
✓ Diversity- identified hadrons AND fully reconstructed jets
✓ Surprises: - collectivity also in pPb and pp collisions- ‘sequential’ pattern for onia also observed in pp and pPb collisions
28
Extra stuff
29
➡ 4 (6, 8) -particle cumulant (average over all events)✓ .
LHC: … collective motion EVERYWHERE
30
offlinetrkN
0 50 100 150
2v 0.05
0.10 = 13 TeVspp
< 3.0 GeV/cT
0.3 < p| < 2.4η|
PreliminaryCMS
|>2}η∆{2, |sub2v{4}2v{6}2v{8}2v{LYZ}2v
offlinetrkN
0 100 200 300
2v
0.05
0.10 = 2.76 TeVNNsPbPb
< 3.0 GeV/cT
0.3 < p| < 2.4η|
offlinetrkN
0 100 200 300
2v
0.05
0.10 = 5 TeVNNspPb
< 3.0 GeV/cT
0.3 < p| < 2.4η|
4 ≈ cos n φ1 +φ2 −φ3 −φ4( )#$ %&
1 2
z
3 4
cn{4} = 4 − 2 22, vn{4} = −cn{4}4
arXiv:1606.06198