[PPT] - Measurement of high-p T azimuthal anisotropy in charged hadron PowerPoint Presentation

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Victoria Zhukova Quark Matter 2012, Washington DC

Measurement of high-pT azimuthal anisotropy in charged hadron production from 2.76 TeV PbPb collisions at CMS

Victoria Zhukova

(MIT)

for the CMS Collaboration Quark Matter Conference, Washington DC 14th Aug, 2012

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d3N pT dpT dηdφ = 1 2π d2N pT dpT dη (1 +

∞

X

k=1

2vn=km(pT , η)cos[n(φ − Ψpp

m )])

Victoria Zhukova Quark Matter 2012, Washington DC

Jet Quenching and Azimuthal Anisotropy

jet energy loss (

Fourier decomposition of charged hadron yields: Path length (L) dependence of jet energy loss (ΔE) ΔE~Lα Azimuthal anisotropy (v2, v3, v4 ) of high pT jets

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Victoria Zhukova Quark Matter 2012, Washington DC

Physics Motivation

ΔE~Lα
Phys. Lett. B (2012) 710 256
Phys. Rev. Lett. (2011) 106 312301
Eur. Phys. J. C. (2012) 72 1945

JHEP 1205 (2012) 063

α = 1 for pQCD, collisional α = 2 for pQCD, radiative α = 3 for AdS/CFT Initial Conditions:

Glauber
Color Glass Condensate

3

Phys. Usp. B 52, 659 (2009)
Nucl. Phys. A784, 426 (2007)
Phys. Rev. C 82, 024908 (2011)
Phys. Rev. C 84, 034904 (2011)
Phys. Rev. C 83, 024908 (2011)

) (GeV)

T

(m

T

p

20 40 60 80 100

AA

R

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

(0-5%) Charged particles b-quarks (0-100%) ) ψ (via secondary J/ > 20 GeV/c

µ T

* Z (0-100%) p > 25 GeV/c

µ T

W (0-100%) p Isolated photon (0-10%)

= 2.76 TeV

NN

s CMS (* preliminary) PbPb

1

b µ L dt = 7-150

∫

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Victoria Zhukova Quark Matter 2012, Washington DC

CMS Detector

Hadronic Calorimeter

EM Calorimeter Tracker

Hadronic calorimeters

Unprecedented kinematic range and acceptance

CMS Detector

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Victoria Zhukova Quark Matter 2012, Washington DC

High pT Single Track Trigger

Full 2011 HI Data set: Lint = 150 µb-1
Single-Track High-pT Triggers

(Total # of events: ~1.55M with pT > 20 GeV/c )

All triggers are at least 95% efficient (0-40%)

(GeV/c)

T max

p 10 12 14 16 18 20 22 24 26 28 30 Trigger Efficiency 0.2 0.4 0.6 0.8 1

CMS Preliminary Trigger Thresholds: > 12 GeV/c

T

p > 14 GeV/c

T

p > 20 GeV/c

T

p Centrality: 40 - 100% | < 1 η |

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Victoria Zhukova Quark Matter 2012, Washington DC

Event Plane Formalism

Event Plane Experimentally observable, used to estimate the true participant plane. v2 Coefficient

Centrality (%) 10 20 30 40 50 60 70 80 90 100 Resolution Correction Factor 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 < -3) ! " HF- (-5 < 5) ! " HF+ (3 2 Subevent =2.76 TeV

NN

s CMS PbPb

v2 EP

{ }

cos 2

EP

( )

% ' / R

Need to correct for ΨEP resolution (R).

Four-particle Cumulant

Resolution Correction: (3-subevent method)

6

x ( f m )

1

5

1
5

5 1 1 5 y ( f m )

1

5

1
5

5 1 1 5 b = 6 . f m = . 2 3 8

part

ε = 2 . 4 4 f m

x'

σ = 3 . 6 6 f m

y'

σ x' y'

R

Ψ

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Victoria Zhukova Quark Matter 2012, Washington DC

Avoiding Di-Jet Correlations

7

η φ 5

5
3

3 EP- V2- V2+ EP+

gap

To calculate v2 : v2+ with EP- and v2- with EP+ Particles from the positive η region are correlated with the event plane calculated in the negative η region.

Event Planes: EP+ (3<η<5) EP- (-5<η<-3) Hadronic Forward Calorimeters used for determining the Event Plane.

This minimizes systematic effects that result from back-to-back di-jets

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Victoria Zhukova Quark Matter 2012, Washington DC

η-Gap Study

8

{EP}

2

v

0.05 0.1 0.15 0.2 0.25 0.3

0 - 10%

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

10 - 20%

(GeV/c)

T

p 1.0 - 1.1 1.6 - 1.8 2.4 - 3.2 9.6 - 12.0 35.2 - 48.0

20 - 30%

gap

η Δ

1 2 3 4 5

{EP}

2

v

0.05 0.1 0.15 0.2 0.25 0.3

30 - 40%

gap

η Δ

1 2 3 4 5

40 - 50%

gap

η Δ

1 2 3 4 5

50 - 60%

Based on this study we conclude that the gap size of 3 is sufficient to suppress most of the back-to-back di-jet effects

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Victoria Zhukova Quark Matter 2012, Washington DC

η-Gap Study

9

{EP}

2

v

0.05 0.1 0.15 0.2 0.25 0.3

0 - 10%

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb CMS Preliminary

10 - 20%

(GeV/c)

T

p 1.0 - 1.1 1.6 - 1.8 2.4 - 3.2 9.6 - 12.0 35.2 - 48.0

20 - 30%

gap

η Δ

1 2 3 4 5

{EP}

2

v

0.05 0.1 0.15 0.2 0.25 0.3

30 - 40%

gap

η Δ

1 2 3 4 5

40 - 50%

gap

η Δ

1 2 3 4 5

50 - 60%

high pT Based on this study we conclude that the gap size of 3 is sufficient to suppress most of the back-to-back di-jet effects

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Victoria Zhukova Quark Matter 2012, Washington DC

v2 as a function of pT (|η|<1)

10

First v2 measurements for pT > 20GeV/c
Gradual decrease of v2 above pT ~ 10 GeV/c

1 2 3 4 5

2

v

.

5 . 5 . 1 . 1 5 . 2 . 2 5

CMS 2011 |<0.8 η CMS 2010, | ATLAS |<0.8 η ALICE, |

1

b µ = 150

i n t

CMS L = 2.76 TeV

N N

s PbPb

| < 1 η |

1

%

(GeV/c)

T

p

1 2 3 4 5

2

v

.

5 . 5 . 1 . 1 5 . 2 . 2 5

3

4

%

1 2 3 4 5

.

5 . 5 . 1 . 1 5 . 2 . 2 5

1

2

%

(GeV/c)

T

p

10 20 30 40 50

0.05

0.05 0.1 0.15 0.2 0.25

4

5

%

1 2 3 4 5

.

5 . 5 . 1 . 1 5 . 2 . 2 5

2

3

%

(GeV/c)

T

p

10 20 30 40 50

0.05

0.05 0.1 0.15 0.2 0.25

50-60%

PRL 109, 022301(2012) 0-10% 10-20% 20-30% 30-40% 40-50% 50-60%

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Victoria Zhukova Quark Matter 2012, Washington DC

v2 as a function of pT (1<|η|<2 )

11

20 40

2

v

. . 1 . 2

CMS 2011 ATLAS

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb

|<2 η 1<|

0-10%

(GeV/c)

T

p

20 40

2

v

. . 1 . 2

30-40%

20 40

. . 1 . 2

10-20%

(GeV/c)

T

p

20 40

. . 1 . 2

40-50%

20 40

. . 1 . 2

20-30%

(GeV/c)

T

p

20 40

. . 1 . 2 5

6

%

PRL 109, 022301(2012) 0-10% 10-20% 20-30% 30-40% 40-50% 50-60%

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Victoria Zhukova Quark Matter 2012, Washington DC

Theory Comparison

12

Data can constrain different theoretical scenarios

Theory: B.Betz,M.Gyulassy;arXiv:1201.0281 Data: PRL 109.022301(2012)

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Victoria Zhukova Quark Matter 2012, Washington DC

Higher Harmonics Results (v3)

13

NEW RESULTS!!!

20 40

3

v

0.00 0.05 0.10 0.15

|<1 η | |<2 η 1<|

CMS Preliminary

1

b µ = 150

int

L = 2.76 TeV

NN

s PbPb

0-10%

( G e V / c )

T

p

20 40

3

v

0.00 0.05 0.10 0.15

30-40%

20 40

0.00 0.05 0.10 0.15

10-20%

(GeV/c)

T

p

20 40

0.00 0.05 0.10 0.15

40-50%

20 40

0.00 0.05 0.10 0.15

20-30% (GeV/c)

T

p

20 40

0.00 0.05 0.10 0.15

5

6

%

PAS HIN-12-010

Small v3 signal above 20 GeV/c.

0-10% 10-20% 20-30% 30-40% 40-50% 50-60%

GLAUBER

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Victoria Zhukova Quark Matter 2012, Washington DC

Higher Harmonics Results (v4)

14

20 40

4

v

0.00 0.05 0.10 0.15

CMS Preliminary

1

b µ = 150

i n t

L = 2.76 TeV

N N

s PbPb

|<1 η | |<2 η 1<|

0-10%

(GeV/c)

T

p

20 40

4

v

0.00 0.05 0.10 0.15

30-40%

20 40

0.00 0.05 0.10 0.15

10-20%

(GeV/c)

T

p

20 40

0.00 0.05 0.10 0.15

40-50%

20 40

0.00 0.05 0.10 0.15

20-30% (GeV/c)

T

p

20 40

0.00 0.05 0.10 0.15

50-60%

NEW RESULTS!!!

PAS HIN-12-010 0-10% 10-20% 20-30% 30-40% 40-50% 50-60%

GLAUBER

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Victoria Zhukova Quark Matter 2012, Washington DC

v2 as a function of centrality

15

participants

εpart: 0.09 (0-10%) to 0.46 (50-60%)

Significant non-zero v2 up to pT~48 GeV/c for all the centralities.
For pT > 48 GeV/c v2 is consistent with 0 for all the centralities.

100 200 300

2

v

0.0 0.1 0.2

1

b µ = 150

int

CMS L = 2.76 TeV

NN

s PbPb

|<1 η | |<2 η 1<|

< 1.1 GeV/c

T

1.0 < p

part

N

100 200 300

2

v

0.0 0.1 0.2

< 35.2 GeV/c

T

28.8 < p

100 200 300

0.0 0.1 0.2

< 4.0 GeV/c

T

3.2 < p

part

N

100 200 300

0.0 0.1 0.2

< 48 GeV/c

T

35.2 < p

100 200 300

0.0 0.1 0.2

< 16 GeV/c

T

14 < p

part

N

100 200 300

0.0 0.1 0.2

< 60.8 GeV/c

T

48 < p

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Victoria Zhukova Quark Matter 2012, Washington DC

Summary

l

The v2 azimuthal anisotropy coefficient is determined over a wide coverage in pT: 1< pT < 60 GeV/c as a function of collision centrality based on the 2011 data sample.

l

The v3 and v4 coefficients are obtained up to pT~ 40 GeV/c.

l

Above pT~10GeV/c v2 values show a gradual decrease with pT, being consistent with zero only above pT~48 GeV/c for all the

centralities. The v3 and v4 asymmetries are small above 20 GeV/c.

l

Centrality dependence of v2 is observed for both very low and high-pT particles. It is consistent with path-length-dependent energy loss observed at high-pT up to pT ~ 35 GeV/c.

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Victoria Zhukova Quark Matter 2012, Washington DC 17

BACKUP

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03/02/12 9

Di-hadron Correlations Formalism

Signal pair distribution: Background pair distribution:

Δη = ηassoc – ηtrig Δφ = φassoc – φtrig

Associated hadron yield per trigger:

back-to-back di-jet correlations long-range near- side structure

jet peak

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Victoria.Zhukova@cern.ch Quark Matter 2012

Azimuthal Correlations at High pT

Clear and significant long-range near-side structure is observed for

the first time for pTtrig > 20 GeV/c.

η Δ

2

2

φ Δ

2 4

φ Δ d η Δ d

p a i r

N

2

d

t r i g

N 1 2 5 . 5 2 6 . 2 6 . 5

C M S P r e l i m i n a r y ( a )

1

b µ = 1 5

i n t

L = 2 . 7 6 T e V

N N

s P b P b > 2 G e V / c

t r i g T

p < 2 G e V / c

a s s

c

T

1 < p

3

% c e n t r a l i t y

| φ Δ |

1 2 3

φ Δ d

pair

d N

trig

N 1

2 5 . 6 2 5 . 8 2 6 . 2 6 . 2 2 6 . 4 ( b )

1

b µ = 1 5

i n t

L = 2 . 7 6 T e V

N N

s P b P b | < 3 . 5 η Δ 2 < | > 2 G e V / c

t r i g T

p < 2 G e V / c

a s s

c

T

1 < p

3

% c e n t r a l i t y C M S P r e l i m i n a r y 10