Updates on the study of dihadron correlationLiang Zheng EIC task force meeting

What we have done up to now and where are we going?1. We have made the plots benchmarking possible

underlying physics channel through the measurements of dihadron correlation.

2. We come up with a comparison between our Monte Carlo results and a theoretical prediction with saturation.

3. Possible detector effect is studied by a fast smearing method.

4. Performance of measurements with different luminosities.

5. Webpage as a memo note for the work has been updated in our wikipage: https://wiki.bnl.gov/eic/index.php/Dihadron

2013/4/42

Part One: Benchmark plots for ep

∆φ distribution for All process

e+p 20x100GeV, PYTHIA default setting1<Q2<1.5, 0.65<y<0.75, <x>=2.2e-4charged hadrons, 0.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

No realistic luminosity issue considered.

2013/4/43

Part One: Benchmark plots for ep

∆φ distribution for DIS process

e+p 20x100GeV, PYTHIA default setting1<Q2<1.5, 0.65<y<0.75, <x>=2.2e-4charged hadrons, 0.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

PGF process 61.06% QCDC process 10.51%

2013/4/44

Part One: Benchmark plots for ep

∆φ distribution for Resolved process

e+p 20x100GeV, PYTHIA default setting1<Q2<1.5, 0.65<y<0.75, <x>=2.2e-4charged hadrons, 0.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

g+g channel 1.76% q+g channel 17.82%

q+q channel 8.59%

2013/4/45

Part One: Benchmark plots for ep

Fraction of different processes out of total versus ∆φ

e+p 20x100GeV, PYTHIA default setting1<Q2<1.5, 0.65<y<0.75, <x>=2.2e-4charged hadrons, 0.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

2013/4/46

Part One: Benchmark plots for ep

∆φ distribution and QCD radiation

e+p 20x100GeV1<Q2<1.5, 0.65<y<0.75charged hadrons, 0.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

With particle decay contribution Without particle decay contribution

1. Intrinsic kT2. Initial state Parton Shower3. Final state Parton Shower4. Fragmentation pT5. Particle decay

Near side

Away side

dominate

2013/4/47

Part One: Benchmark plots for eA

eA with nuclear PDF vs ep (all process included)

e+p/Au 20x100GeV, PYTHIA default setting1<Q2<1.5, 0.65<y<0.75charged hadrons, 0.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

eAu Energy loss vs nuclear PDF eAu vs ep

Relevant nuclear effects:1. Nuclear PDF2. Energy loss

2013/4/48

Part Two: Compare with CGC

ep ∆φ at different kT with JETSET fragmentation

kT = 0.4

kT = 0.7kT = 0.6

e+p 30x100GeV0.5<Q2<1.5, 0.65<y<0.750.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

Parton shower switched off, blue curve from Bowen’s calculation without fragmentation pT

2013/4/49

Part Two: Compare with CGC

ep ∆φ with JETSET fragmentation when frag pT on

e+p 30x100GeV0.5<Q2<1.5, 0.65<y<0.750.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

Parton shower switched off, blue/green curve from Bowen’s calculation w/o or with fragmentation pTFrag pT = 0.3 Frag pT = 0.4

kT distribution changed from PYTHIA default:

to a gauss distribution

No decay result rescaled based on the decay integral

with σ=0.6

2013/4/410

Part Two: Compare with CGC

ep ∆φ with DSS fragmentation

e+p 30x100GeV1.0<Q2<2.0, 0.65<y<0.750.25 < z trig, z asso < 0.35pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

kT from a gauss distribution function

Parton shower switched off, blue/green curve from Bowen’s calculation w/o or with fragmentation pT

with σ=0.6

No frag pT frag pT = 0.4

Factorization scale:

2013/4/411

Part Two: Compare with CGC

ep ∆φ with DSS fragmentation

e+p 30x100GeV3.5<Q2<4.5, 0.65<y<0.750.25 < z trig, z asso < 0.35pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

Parton shower switched off, blue/green curve from Bowen’s calculation w/o or with fragmentation pTNo frag pT frag pT = 0.4

kT from a gauss distribution function

with σ=0.6

Factorization scale:

2013/4/412

Part Three: Detector smearing

Smearing detector layout

Central tracker -1< η < 1, point resolution 80 microns, 45 fit pointsForward/backward tracker 1< η < 3.5, -3.5 < η < -1, point resolution 80 microns, 6 planes

Far forward/backward tracker 3.5 < η < 4.5, -4.5 < η < -3.5, point resolution 20 microns, 12 planes

Magnetic Field: B=0.3TRadiation length: 0.03

Central: radial trackerForward/Backward: planar tracker

Simply tracking resolution considered.

2013/4/413

Part Three: Detector smearing

Kinematics migration

20x100 GeV Q2 vs x unsmeared 20x100 GeV Q2 vs x smeared

Unsmeared event sample with cuts: 0.5 < y < 0.9, 2 < Q2 < 6

Unsmeared scattered electron direction

Electrons in forward/backward tracking region

2013/4/414

Part Three: Detector smearing

Kinematics migration

20x100 GeV smeared loss due to kinematics migration

30x100 GeV smeared loss due to kinematics migration

Smeared variable cut:2.5<Q2<5, 0.55<y<0.8out from the event sample with unsmeared kinematics: 2<Q2<6, 0.5<y<0.90.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

Smearing loss mainly come from kinematics migration.Tracking information for electron not good enough in such a region…Tracking worse for

higher electron momentum

2013/4/415

Part Three: Detector smearing

detector smearing effect

e+p 30x100GeV2<Q2<6, 0.5<y<0.90.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

No kinematics migration. (No smeared Q2/y cuts)

Hadron pairs in center and forward/backward tracking region!

2013/4/416

Part Three: Detector smearing

Two particle correlation with smearing

Trig pT smearing Associate pT smearing

e+p 30x100GeV2<Q2<6, 0.5<y<0.90.2 < z trig, z asso < 0.4pT

trig > 2 GeV, 1 GeV < pT asso < pT trig

If no Q2/x migration, no strong smearing effect.

No kinematics migration. (No smeared Q2/y cuts)

2013/4/417

Part Four: Double gauss fit

Underlying quark pT imbalance probed by correlation

ep 20x100 0.65<y<0.75, 0.5<Q2<1.5pT trig >2, 1 < pT asso < pT trig 0.2<z<0.4Charged particle, all effects/ no Initial radiation

“pT imbalance” means the vector sum of the transverse momentum of two outgoing quarks

2013/4/418

Part Four: Double gauss fit

∆φ at different kT studied by double gauss fit

Fit parameters

ep 20x100 0.65<y<0.75, 1<Q2<1.5pT trig >2, 1 < pT asso < pT trig 0.2<z<0.4Charged particleall effects on

2013/4/419

Part Five: Kinematics scan

Kinematics region in Q2 and x we will approach

Black : 30x100Red : 20x100Green:10x100

Kinematics span for ep 30/20/10 x100 GeVevent samples in the bin of y in [0.6, 0.8] , [0.25, 0.35]; and Q2 in [0.5, 1.5], [3, 5], [9, 11], [15.5, 20.5].

2013/4/420

Part Five: Kinematics scan

∆φ for ep and eAu with 10 fb-1

ep (dots)/ eAu(open triangle) 20x100 Lumi=10 fb-1ep/eAu20x100 GeVpT trig >2, 1 < pT asso < pT trig ,0.2<z<0.4Charged particleall effects on

y increasing

Black:allRed:PGF Q2

incr

easin

g

2013/4/421

Part Five: Kinematics scan

JeAu vs xAfrag with 10 fb-1

ep (dots)/ eAu(open triangle) 20x100 Lumi=10 fb-1ep/eAu20x100 GeVpT trig >2, 1 < pT asso < pT trig ,0.2<z<0.4Charged particleall effects on

Black:allRed:PGF

[Npair(xAfrag)/Nevt]eAu

[Npair(xAfrag)/Nevt]ep

JeA=Q2

incr

easin

g

y increasing

2013/4/422

Part Five: Kinematics scan

JeAu vs xg with 10 fb-1

Black:allRed:PGF Q2

incr

easin

g[Npair(xg)/Nevt(xg)]eAu

[Npair(xg)/Nevt(xg)]epJeA=

If analyzed in every xg bin, Pair dependence on xg will be canceled by event dependence.

y increasingep (dots)/ eAu(open triangle) 20x100 Lumi=10 fb-1ep/eAu20x100 GeV

pT trig >2, 1 < pT asso < pT trig ,0.2<z<0.4Charged particleall effects on

2013/4/423

Part Five: Kinematics scan

Fitted width from double gauss for ep/eAu

2013/4/424

Part Five: Kinematics scan

∆φ for ep and eAu with 1 fb-1

ep (dots)/ eAu(open triangle) 20x100 Lumi=10 fb-1ep/eAu20x100 GeVpT trig >2, 1 < pT asso < pT trig ,0.2<z<0.4Charged particleall effects on

y increasing

Black:allRed:PGF Q2

incr

easin

g

2013/4/425

Part Five: Kinematics scan

Fitted width from double gauss for ep/eAu with 1 fb-1

2013/4/426