East Barrel

wiki.bnl.gov

East Barrel

Dijet Production in Polarized

Proton-Proton Collisions at

STAR

200 GeV at STAR

Matthew Walker

for the STAR Collaboration

April 12, 2011


✦ Brief theoretical motivation

✦ Experimental Overview

✦ Cross Section Analysis

✦ Asymmetry Analysis

✦ Status of ongoing analysis

Outline

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

2


x!u

0.02


to ∆χ = 1. In order to account for unexpected

stomary to consider instead of ∆χ2 = 1 between

e of uncertainty.

e first moments of u and d resemble a parabola

ix units relative to those from KRE, due to the

at the overall goodness of KKP fit is poorer than

es for δd computed with the respective best fits

to the ideal situation. However for δu, they only

very good example of how the ∆χ2 uation. However for δu, they only

ple of how the ∆χ

= 1 does not

rences between the available sets of fragmentation

2 = 1 does not

the available sets of fragmentation

Theoretical Motivation

0.04

✦ Polarized 0 DIS tells us that the

spin contribution 0.4 from quark

-0.02 spin is only ~30%.

x!g –

x!s –

DSSV

DNS KRE

-0.04

DNS KKP

DSSV !" 2 =1

DSSV !" 2 0.2

Without RHIC data =2%

With RHIC data

0.04

0.02

0

KRE -0.02 (NLO)

KKP (NLO)

unpolarized

KRE -0.04 " 2

KRE " min +1

KRE " 2

KRE " min +2%

10 -2

x!s –

x

0

-0.2

0.06

0.04

0.02

0

10 -1

-0.02

10 -2

x

KRE (NLO)

KKP (NLO)

unpolarized

KRE " 2

KRE " +1

1

0.4

0.2

0

-0.2

10 -1

D. de Florian et al., Phys. Rev. D71, 094018 (2005). D. de Florian et al., Phys. Rev. Lett. 101 (2008) 072001

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

-0.04

0.06

0.04

x!d –

1

2

x!g

= 1

GRSV maxg

GRSV ming

10 -2

x

10 -1

0.04

0.02

2 ∆Σ + Lq +∆G + Lg

x

0

-0.02

-0.04

1

0.3

0.2

0.1

0

-0.1

-0.2

Substantial

improvement for

0.05 < x < 0.2,

but large

uncertainties at

low x

3


Theoretical Motivation

✦ Extracting gluon polarization

ALL = d∆σ


= ∆f1 ⊗ ∆f2 ⊗ σh · aLL ⊗ D h f

f1 ⊗ f2 ⊗ σh ⊗ D h f

∆f1

∆f2

σh

long-range short-range long-range

Extract ∆g(x,Q 2 ) using a global fit

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

1

2

aLL

= 1

1

0.75

0.5

0.25

0

-0.25

-0.5

-0.75

-1

2 ∆Σ + Lq +∆G + Lg

qg → qg

qq → qq q¯q → q¯q

gg → q¯q

gg → gg

-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 1

∆G(Q 2 ) =

� 1

0

cosθ*

∆g(x, Q 2 )dx

4


Inclusive jets

✦ Run 6 results: GRSV-MAX/

GRSV-MIN ruled out, a gluon

polarization between GRSV-std

and GRSV-zero favored

See Pibero Djawotho’s talk for more on inclusive jets from STAR

A LL systematics (x 10 -3 )

Reconstruction +

Trigger Bias

Non-longitudinal

Polarization

Relative

Luminosity

Backgrounds

D. de Florian et al. PRL 101 (2008) 072001.

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

[-1,+3]

(p T dep)

~ 0.03

(p T dep)

0.94

1 st bin ~ 0.5

else ~ 0.1

p T systematic ± 6.7%

5


Correlation Measurements

✦ Reconstructing multiple physics

objects (di-jets, photon/jet)

provides information about

initial parton kinematics

✦ STAR well suited for correlation

measurements with its large

acceptance

x1 = 1 √ s (pT 3e η3 + pT 4e η4 )

x2 = 1 √ s (pT 3e −η3 + pT 4e −η4 )

M = √ x1x2s

η3 + η4 = ln x1

x2

STAR Collaboration

PRL 100 (2008) 232003

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

6


✦ RHIC produces

polarized proton

beams up to 250

GeV in energy

✦ Siberian snake

magnets in the

AGS and RHIC

help protect beam

from depolarized

resonances

Experimental Setup

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

7


Blue

East

!=-1

BBC

Tai Sakuma, Thesis, MIT (2010)

STAR Detector

BEMC

TPC

!=0

Not shown:

Zero-degree calorimeters,

time-of-flight, polarimeters

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

!=1

West

Yellow

Tai Sakuma

8


Jet

π +

π 0

g

q

Jet Terminology

parton particle detector

Tracks, Energy Depositions

Detector Effects

Hadrons, Leptons

Parton Branching, Hadronization,

Underlying Event

Partons

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

9


Data

✦ 2006 Data: 5.39 pb -1 taken during RHIC Run 6

✦ 2009 Data: ~10 pb -1 taken during RHIC Run 9

✦ Jet Patch Trigger:

✦ 1x1 in φxη patch

of towers in the

BEMC (400

towers)

✦ Midpoint Cone

Algorithm with Split-

Merge

✦ Cone Radius: 0.7

✦ Seed 0.5 GeV

Tai Sakuma, Thesis, MIT (2010)

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

10


Data/Simulation Run 6

✦ 2006 Simulation:

✦ 11 STAR MC productions

producing 4M events with

partonic pT between 3 GeV

and 65 GeV

✦ PYTHIA 6.410, CDF Tune A

✦ Run 6 data and simulation

agreement is good

Tai Sakuma, Thesis, MIT (2010)

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

11


d 3 !/dMd! 3d! 4 [pb/GeV]

10 5

10 4

10 3

10 2

10

1

d 3 !

dMd! 3d! 4

STAR Run-6

2006 Cross Section

Systematic Uncertainty

Theory

Dijet Cross Section

pp @ 200 GeV

Cone Radius = 0.7

max(p T) > 10 GeV, min(p T) > 7 GeV

-0.8 < ! < 0.8, |!!| < 1.0

|!!| > 2.0

NLO pQCD + CTEQ6M

Had. and UE. Corrections

STAR Preliminary

! !

Ldt = 5.39pb!1

30 40 50 60 70 80 90

Mjj [GeV]

Tai Sakuma, Thesis, MIT (2010)

✦ Unpolarized differential cross

section between 24 and 100

(GeV/c 2 )

✦ NLO theory predictions using

CTEQ6M provided by de

Florian with and without

corrections for hadronization

and underlying event from

PYTHIA

✦ Statistical Uncertainties as

lines, systematics as rectangles

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

12


(Data - Theory) / Theory

-1.0 -0.5 0.0 0.5 1.0

2006 Cross Section

Systematic Uncertainty

Theoretical Uncertainty

! STAR

!

Ldt = 5.39 pb!1

Data-theory Comparison

of Dijet Cross Section

pp @ 200 GeV

Cone Radius = 0.7

max(p T) > 10 GeV, min(p T) > 7 GeV

-0.8 < ! < 0.8, |!!| < 1.0, |!!| > 2.0

Preliminary

30 40 50 60 70 80 90

M jj [GeV]

STAR Run-6

Theory:

CTEQ6M

NLO pQCD

Had. UE. Corrections

Tai Sakuma, Thesis, MIT (2010)

✦ Comparison to theory

(including hadronization

and underlying event

correction) shows good

agreement within

systematic uncertainties

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

13


2006 Asymmetry

ALL = 1

PBPY

✦ Asymmetry formula:

✦ N ++ : like sign yields

✦ N +- : unlike sign yields

✦ R: relative luminosity

✦ P: polarization

N ++ − RN +−

N ++ + RN +−

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

14


✦ Run 6 Longitudinal double

helicity asymmetry

✦ Systematic uncertainties

show effects on trigger

efficiency from different

theory scenarios

✦ Scale uncertainty (8.3%)

from polarization

uncertainty not shown

2006 Asymmetry

A LL

M jj [GeV]

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

0.08

0.06

0.04

0.02

0.00

-0.02

Dijet A LL

pp @ 200 GeV

Cone Radius = 0.7

max(p T) > 10 GeV

min(p T) > 7 GeV

-0.8 < ! < 0.8, |!!| < 1.0

|!!| > 2.0

GRSV STD

DSSV

GRSV !g = 0

GRSV !g = ! g

Data Run-6

Sys. Uncertainty

STAR Preliminary

! !

Ldt = 5.39pb!1

30 40 50 60 70 80

15


2009 Simulation

✦ Different detector, different trigger, updated geometry

✦ 9 STAR MC productions with partonic pT > 2 GeV

✦ PYTHIA 6.4.23, proPt0 (PYTUNE 329)

✦ Virtual Machine prepared with STAR software stack and deployed to over 1000 machines

✦ Run using cloud computing resources at Clemson University in South Carolina (Ranked

#85 best supercomputer)

✦ Over 12 billion events

generated by PYTHIA, filtered

to allow only 36 million to

undergo detector simulation

(GEANT3), and 10 million

through full reconstruction

✦ Took over 400,000 CPU hours

and generated 7 TB of files

transferred to BNL

✦ Largest physics simulation on

cloud, largest STAR simulation

Jul17 Jul24 Jul31

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

N Machines

1400

1200

1000

800

600

400

200

0

Available Machines

Working Machines

Idle Machines

Date

16


✦ Run 9 data

simulation

agreement is

good

Data/Simulation Run 9

Normalized Yields

(Data-Simu)/Simulation

6

10

5

10

4

10

3

10

Data

Simulation

20 30 40 50 60 70 80 90 100

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1

20 30 40 50 60 70 80 90 100

2

Invariant Mass (GeV/c

STAR Run 9 Data Preliminary

)

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

5

10

4

10

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

η

34

5

10

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

0 0.1 0.2 0.3 0.4 0.5 0.6

1

Rcone

= 0.7

-0.8 < η < 0.8

| Δη|

< 1.0

| Δφ|

> 2.0

p+p → Jet + Jet + X

s = 200 GeV

STAR Preliminary

-1

0 0.1 0.2 0.3 0.4 0.5 0.6

cos( θ*)

17


LL

A

East Barrel - East Barrel and West Barrel - West Barrel

0.08

0.06

0.04

0.02

0

-0.02

MC GS-C(pdf set NLO)

2009 STAR Data

Systematic Uncertainties

20 30 40 50 60 70 80

Run 9 Asymmetry

2

M [GeV/c ]

LL

A

East Barrel - West Barrel

0.08

0.06

0.04

0.02

0

-0.02

Scale uncertainty

GRSV std

DSSV

20 30 40 50 60 70 80

East West East West

2

M [GeV/c ]

20 30 40 50 60 70 80

2

M [GeV/c ]

STAR Matthew Walker, MIT

March 29, 2011

Jet Meeting

LL

A

0.08

0.06

0.04

0.02

0

-0.02

Full Acceptance


s = 200 GeV

p + p → jet + jet + X

STAR

Preliminary

18


Kinematic Sensitivity

5

10

4

10

3

10

2

10

10

1

-1

10

-2

10

10

x

-1

10

-2

East Barrel - East Barrel East Barrel - West Barrel

-1

10 1

1

X X

STAR

X

Preliminary


s = 200 GeV

p + p → jet + jet + X

20 30 40 50 60 70 80 90 100

2

Invariant Mass (GeV/c )

5

10

4

10

3

10

2

10

-1

10

10

10

x

STAR Matthew Walker, MIT

March 29, 2011 Jet Meeting 19

10

1

-2

1

-1

10

-2

x1:

20.0 < M < 30.0

x2:

20.0 < M < 30.0

x1:

70.0 < M < 80.0

x2:

70.0 < M < 80.0

-1

10 1

x1

20 30 40 50 60 70 80 90 100

2

Invariant Mass (GeV/c )

x

2

X


Summary

✦ Correlations measurements provide constraints on parton

kinematics, which helps constrain the shape of Δg(x)

✦ 2006 Dijet cross section (5.39 pb -1 ) shows good agreement with

NLO calculations

✦ First Dijet double-spin asymmetry (FOM = 0.59 pb -1 ) from

2006 data suggests preference away from GRSV-std scenario

✦ 2009 Dijet asymmetry analysis underway with FOM = 1.21

pb -1 analyzed to date, and more to come, allows for the first

separation into multiple pseudorapidity acceptances

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

20


Backup

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

21


LL

A

2009 Projections

east barrel - east barrel and west barrel - west barrel

0.06

0.05

0.04

0.03

0.02

0.01

0

-0.01

MC

GRSV std

GRSV m03

GRSV zero

GS-C(pdf set NLO)

2009 STAR Data

-0.02

20 30 40 50 60 70 80

Wed Sep 22 15:18:55 2010 ]

2

M [GeV/c

-0.02

20 30 40 50 60 70 80

East West East West

2

M [GeV/c ]

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

LL

A

east barrel - west barrel

0.06

0.05

0.04

0.03

0.02

0.01

0

-0.01

Scale uncertainty

GRSV std

DSSV

STAR

Projected Precision

22


ALL,j =



k

2009 Asymmetry


k

αjk(

i PB,iPY,i(N5,i,k + N10,i,k) − PB,iPY,iRi(N6,i,k + N9,i,k))


αjk(

i P 2 B,iP 2 Y,i (N5,i,k + N10,i,k)+P 2 B,i,jP 2 Y,i,jRi(N6,i,k + N9,i,k))

✦ The value of ALL in a bin j is given by the above formula

✦ αjk are the matrix elements for the unfolding

✦ Changing the jet energy scale results in different unfolding

matrices

✦ The calculation is repeated for the different matrices to get the

uncertainty on ALL due to the jet energy scale

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

23


Dijet Run 9 Projected

STAR Matthew Walker, MIT

April 12, 2011

SPIN 2011

24

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