Post QM17 : Flow
Hiroshi Nakagomi
Univ. of Tsukuba

1

Contents•pp 13TeV at LHC•p/d/3He+Au at RHIC•Longitudinal direction-Event plane de-correlation-Forward/backward asymmetry of vn-HBT•Event shape engineering-HBT•Low energy(Fixed target HADES)-v3 w.r.t Psi12

v2 in p+p 13 TeV
CMS Zhenyu Chen•CMS Low mult. subtraction method•ATLAS Template fit-Template function using low mult. -Subtract low mult. from high mult.
-Assume v2 = 0 in low mult.
-Assume v2 ≠ 0 in low mult.
-Strong multiplicity dependence-No multiplicity dependence3

PID v2 in p+p 13 TeV

Low mult.

• v2{2} without subtraction-Non-flow is included-Low mult. does not show massordering-Mass ordering at high mult.
• v2{2} with subtraction-Suppress non-flow-Mass ordering is still seen

CMS Zhenyu Chen

High mult.

High - low mult.
4c2{4} in p+p 13 TeV(CMS)•Four particle correlationcn {4} = hhcos[n( 1 + 22hhcos[n( 1 +p4v2 {4} =cn {4}4 )]ii32 )]ii

2CMS Zhenyu Chen

-Negative cn{4} →positive vn{4}-Suppress non-flow, fluctuation•pp 13 TeV shows negative c2{4}-Indicate positive v2-Energy dependence- Collectivity ?
5c2{4} in p+p 13 TeV(ALICE,ATLAS)
ALICE K. Gajdosova

ATLAS M. Zhou

Method1:Event classification with 0.3<pT<3.0 GeV
Method2:Event classification with pT>0.4GeV(=CMS)Event classification with 0.2<pT<3.0 GeV•ALICE/ATLAS(Method1)-c2{4} and event classification with same pT range-c2{4} shows no negative sign
•ATLAS(Method2)-c2{4} shows negative sign, consistent with CMS result-c2{4} depends on event classification(multiplicity fluctuation)6c2{4} in p+p 13 TeV(ALICE,ATLAS)
ALICE K. Gajdosova

ATLAS M. Zhou

Method1:Event classification with 0.3<pT<3.0 GeV
Method2:Event classification with pT>0.4GeV(=CMS)Event classification with 0.2<pT<3.0 GeV

CMS Zhenyu Chen

•CMS-c2{4} and event classification with same pTrange-c2{4} shows negative sign
→CMS does not agree withATLAS(Method1)/ALICE7

d+Au v3

PHENIX Q. Xu•v3 in d+Au is observed-Event plane method•Hydrodynamics reproduces ordering of v3-v3 (3He+Au) > v3 (d+Au)
8

PID v2

3in p/d/ He+Au
PHENIX Q. Xu•Charged π and p v2 in p/d/3He+Au is observed- Event plane method•Mass-ordering feature is seen
- Less pronounced in p+Au
9

d+Au BES: v2 vs pT
PHENIX J. Velkovska•v2 at 200 and 62 GeV shows a similar pT dependence•v2 at 39 and 20 GeV increase at high pT- Non flow ?
10

d+Au BES: Ridge
PHENIX J. Velkovska•Long range correlation is observed in d+Au BES- pT>0, |Δη|>2, charged hadrons (Forward vertex detector)•Elliptic component decreases with decreasing energy
11

d+Au BES: v2 vs η
PHENIX J. Velkovska-Au-going side v2 drasticallychanged below 39GeV

12

Event plane de-correlation

ATLAS M.Soumya
P. Huohqn ( ⌘ref )qn ( ⌘)qn⇤ (+⌘)qn⇤ (+⌘ref )i
Rn,n|n,n =hqn ( ⌘ref )qn⇤ ( ⌘)qn (+⌘)qn⇤ (+⌘ref )icos(n[ n ( ⌘ref )n (⌘ref ) + ( n ( ⌘)⇠hcos(n[ n ( ⌘ref )( n ( ⌘)n (⌘ref )n (⌘))])n (⌘))])

iRn,n|n,n = 1 :η independent Ψnn(⌘ref ) =n (⌘) =n(⌘) =n (⌘ref )Rn,n|n,n < 1 : η dependent Ψn•De-correlation increasing linearly withincreasing η gap•De-correlation is smaller at lower energy•De-correlation is smallest at mid-central
13

Forward/Backward asymmetry of vn
Au-going
Cu-going
Cu+Au• F/B vn plotted as a function of F/B dNch/dη
-Au-going vn (dNch/dη) > Cu-going vn (dNch/dη)-εn,Au-going ≠ εn,Cu-going ?
• Empirical relation among v2, ε2 and dN/dηat mid-η-v2/ε2 ∝ f(dN/dη)-Study of eccentricity
14PHENIX M. Shimomura
H. Nakagomi
Au-goingCu-going

vn/εn : Asymmetric initial eccentricity

PHENIX M. Shimomura
H. Nakagomi

Initial eccentricity
AsymmetricAu

Cuvn, Au-going/εn,Au≠
vn, Cu-going/εn,Cu
15

vn/εn : Symmetric initial eccentricity
PHENIX M. Shimomura
H. Nakagomi

Initial eccentricity
SymmetricAu

Cuvn, Au-going/εn,Cu+Au=vn, Cu-going/εn,Cu+Au16

p+Pb HBT radii vs y(rapidity of pion pair)
ATLAS M. ClarkRside•y’ = y - 0.465
Rout-Center of momentum frame•Central: Pb-going > p-going•Peripheral : Pb-going~p-goingradiiPbp17Pbp

HBT w.r.t Ψn in Pb+Pb with event shape engineering✓Event shape engineering-Select larger flow vector Qn ∝vn
ALICE M. Saleh&N. Tanaka

Large Q2 :20%

Average Q2•Large q2 selection-20% larger v2-slightly enhance finaleccentricity•Large q3 selection-15% larger v3-Final eccentricity doesnot change

Large Q2

ε2, final

No Q2
selection
No Q3
selection

ε3, final18

Large Q3

HBT w.r.t Ψ2 in p+Pb with event shape engineering
RoutRsidecent 0-1%

• Rout: Smaller in-plane size
• Rside: Larger in-plane size
•Same sign of modulation as
seen in A+A•Does not show strong
dependence of Q selection
19

ATLAS M. Clark

Proton v3 w.r.t Ψ1,spec in Au+Au at 1.23AGeV
HADES Behruz Kardan•Proton v1 w.r.t spectator Ψ1-Forward :same direction as Ψ1-Backward:opposite direction as Ψ1•Proton v3 w.r.t spectator Ψ1-Never observed at collider energy-Forward:opposite direction as Ψ1-Backward:same direction as Ψ120

Summary•pp 13TeV at LHC- v2:ATLAS/CMS show different multiplicity dependence- v2:mass ordering is observed as seen in A+A- c2{4}:Inconsistency between ATLAS/ALICE and CMS•p/d/3He+Au at RHIC
-mass ordering is less pronounced in p+Au-d+Au BES pT and η dependence is changed between 39 and 62.4

•Longitudinal direction-η dependent EP-Initial geometry is almost η independent-HBT radii is η dependent•Event shape engineering-PbPb:Unlike ε2,Final , ε3,Final is less sensitive-pPb: HBT radii w.r.t Ψ2, same oscillation as seen PbPb

•Low energy(Fixed target HADES)-v3 w.r.t Psi1 is new observable at BES?
21

Template fit method (ATLAS)•Extract flow component(v2) via template function
Low mult.
=

v2 term+PRL 116, 172301

v2 termv2 term

22

Ridge yieldLow•v2,2 depends on baseline G- G and Yridge increase with NchtotalridgeHighzyam23

Subtraction method (CMS)•Extract flow component(v2) via low mult. subtraction

Phys. Lett. B 765 193

Short range
YnΔ(Δη<1)-Long range
YnΔ(Δη>2)

subV n = Vn

perVn

Yjet
Nasso

per
Yjet
per
Nasso

scale factor-Scale factor is fraction of jet yield-Unlike ATLAS, CMS assumes
24
v2=0 at low mult.

PID v2 in Pb+Pb at 5.02 TeV

25

v2 in p+p 13 TeV
ATLAS Adam Trzupek

CMS Zhenyu Chen26

εn : Asymmetric initial eccentricity
MC-Glauber modelhrn cos[n( Au(Cu)"n,Au(Cu) =hrn i

Cun,Cu+Au )]iz

Au
Au
Cun,Cu+Au

εn, Au: Au participant eccentricityεn, Cu: Cu participant eccentricity27

εn :Symmetric initial eccentricity
MC-Glauber model

hrn cos[n( Au(Cu)"n,Au(Cu) =hrn i

Cun,Cu+Au )]iz

Au
Au
Cu
n,Cu+Auεn, Cu+Au: Cu+Au participant eccentricityεn, Cu+Au: Cu+Au participant eccentricity
28

Additional removal of non-flow29

30

v2 in p+p 13 TeV
CMS Zhenyu Chen•CMS Low mult. subtraction method•ATLAS Template fit-No multiplicity dependence -Strong multiplicity dependence-Hydrodynamics well reproduce→Results depend on31

p+Pb HBT vs local dN/dy•HBT radii is highly correlatedwith local multiplicity
32

HBT w.r.t Ψ2 in p+Pb with event shape engineering
ATLAS M. Clark

cent 0-1%

33

34

35

Additional removal of non-flow:3sub method
ATLAS M. Zhou

• Sub-event method arXiv:1701. 03830•p+Pb-Larger Nch:non-flow is small-Smaller Nch:3sub method reduce
non-flow•p+p-Sub event method reduces non-flow
36

Final eccentricity with ESE

37

38

39

40

41

42

43