rapidity dependency of azimuthal correlations for pp and dau xuan li (bnl&sdu) star...
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Xuan Li 1
Rapidity dependency of azimuthal correlations for pp and dAu
Xuan Li (BNL&SDU)
STAR Collaboration meeting (BNL, Nov 2010)
Xuan Li 2
Outline
• Motivation• Data analysis– cluster finder introduction– π0 like events selection and data & simulation
comparison– Preliminary correlation results
• Summary & To do
Xuan Li 3
Motivation• To probe nuclear gluon density at low x.
Proton gluon density
At a given x, nuclear (mass number A) gluon density ≈ A1/3* nucleon gluon density. And we lack data below x=0.02 for nuclear [Phys. Rev. C70 (2004)044905, hep-ph/0308248].
Can’t increase indefinitely.Saturation?
Fixed Target Experiments
Rapid rise of the gluon density at low-x evident from F2(x)/lnQ2 at fixed x (Prytz relation)
Xuan Li 4
Motivation• How to access low X gluon.
Q2 ~ pT2
s 2EN
ln(tan(2
))
xq xF / z
xF 2E
s
z E
Eq
xg pT
se g
• Large rapidity p production (hp~4) probes asymmetric partonic collisions.
• Mostly high-x valence quark + low-x gluon
• 0.3 < xq< 0.7
• 0.001< xg < 0.1 , this is broad distribution for gluon.
• If we measure two jets, we will limit the measured gluon x range.
Forward di-jets are more sensitive to low x gluon.
Xuan Li 5
Motivation• Test the phase boundary at fixed Q2.
€
ln(1
x)
€
ln(PT2)
Fix PT , look through different x region
τ related to rapidity of produced hadrons.
(Iancu and Venugopalan, hep-ph/0303204)
Fix Pt at forward rapidity π0, and vary the rapidity of associated π0.Vary the Pt to study the boundary.
Xuan Li 6
Motivation
FMS-BEMC(TPC) correlation
Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering.
• Provide direct sensitivity to gluon density at 0.001< x < 0.02.
arXiv:0907.3473
PT(FMS)>2.5GeV/c1.5GeV/c<PT(BEMC/TPC)<PT(FMS)
PT(FMS)>2.0GeV/c1.0GeV/c<PT(BEMC/TPC)<PT(FMS)
Xuan Li 7
Motivation
FMS-FMS correlation
Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering.
• Provide direct sensitivity to gluon density at 0.001< x < 0.02.
arXiv:1005.2378
Xuan Li 8
Motivation
FMS-EEMC correlation
Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering.
• Provide direct sensitivity to gluon density at 0.001< x < 0.02.
?
Xuan Li 9
π0 decay kinematics• Run8 STAR geometry
€
Mγγ = Eγγ 1− Zγγ2 sin
φγγ
2, where Eγγ = E1 + E 2,
Zγγ =E1 − E2
E1 + E2
and φγγ is angle between two photon
momentum vectors. dγγ is the seperation of the two
photons.
π0 decay into 2 photons. Assuming the energy of π0 is 3GeV to 10GeV, then the separation of photons in EEMC is from 25.2cm to 7.6 cm.
Proton (Deuteron)Proton (Gold)
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FMS π0 triggered event• Within the FMS triggered data, selecting events where di-
photon invariant mass is less than 0.2GeV/c2 and Pt is larger than 2.5 GeV/c.
For example, with pp FMS triggered data.
• Primary vertex associated with BBC coincidence requirements.
Xuan Li 11
Introduction to cluster finder• BEMC (EEMC) geometryEEMC η range [1.08,2.0], BEMC η range [-1,1].
Z
X(Y)
X
Y
ϕ
η
ϕ
η
EEMC BEMC
Xuan Li 12
Event display• Run 8 pp fms triggered data. Cluster is threshold bounded group
of towers. The energy threshold for the BEMC tower is 70MeV, and for EEMC is ADC pedestal plus 4sigma. Sorting the tower energy, then add in the tower near the high tower to construct cluster.
EEMC BEMC
cluster
cluster
BEMC tower energy depositedwithout energy threshold.
13
EEMC cluster properties in pp data• Single cluster tower multiplicity, energy, η and φ.
pp dAu
1: Tower multiplicity mean
1.84 1.93
2: cluster energy mean
0.93 0.94
3: cluster η mean 1.49 1.57
4 cluster ϕ χ2/ndf 76 406
1 2
34
14
BEMC cluster properties in pp data• Single cluster tower multiplicity, energy, η and φ.
pp dAu
1: Tower multiplicity mean
1.52 1.83
2: cluster energy mean
0.43 0.70
3: cluster η mean 0.02 0.02
4: cluster ϕ χ2/ndf 241 186
15
π0 like event (di-cluster)• PP part for BEMC η>=0 part.
Mass of di-clustersleading tower energy over cluster energy in leading cluster
Zγγ is energy sharing between two clusters
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, requirecluster detector η in [0,0.9]..
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, reuirecluster detector η in [0,0.9]. (3) Ratio of leading tower energyover cluster energy > 0.9(4) Zγγ < 0.7
π0 peak in BEMC di-clusters.
16
π0 like event (di-cluster)• PP part for EEMC
Mass of di-clusters Zγγ is energy sharing between two clusters
leading tower energy over cluster energy in leading cluster
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, requirecluster detector η in [1.1,1.9]..
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, reuirecluster detector η in [1.1,1.9]. (3) Ratio of leading tower energyover cluster energy > 0.9(4) Zγγ < 0.7
π0 peak in EEMC di-clusters.
17
π0 like event (di-cluster)• dAu part for BEMC η>=0 part.
Mass of di-clustersleading tower energy over cluster energy in leading cluster
Zγγ is energy sharing between two clusters
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, requirecluster detector η in [0,0.9]..
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, reuirecluster detector η in [0,0.9]. (3) Ratio of leading tower energyover cluster energy > 0.9(4) Zγγ < 0.7
π0 peak in BEMC di-clusters.
18
π0 like event (di-cluster)• dAu part for EEMC
Mass of di-clustersleading tower energy over cluster energy in leading cluster
Zγγ is energy sharing between two clusters
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, requirecluster detector η in [1.1,1.9]..
(1) 1.25GeV/c < Pt<2.5GeV/c(2) Fiducial Volume cut, reuirecluster detector η in [1.1,1.9]. (3) Ratio of leading tower energyover cluster energy > 0.9(4) Zγγ < 0.7
π0 peak in EEMC di-clusters.
Xuan Li 19
π0 events in the EEMC single cluster?• Assuming the tower is zero massed,
• Assuming the leading tower, sub-leading tower as the photon candidates in the EEMC single cluster,
• Dγγ is defined as the separation between the photons which is projected in the EEMC detector.
X
Y
Dγγ
Z
X(Y)
γ1
γ2
Dγγ
€
Ecluster = E i , i
∑r P cluster =
r P i ,
i
∑ i is the tower in the cluster
€
Zγγ =E1 − E2
E1 + E2
, E1 is the leading tower energy and E 2 is
the sub - leading tower energy.
Xuan Li 20
Simulated π0 decay kinematics• Projection on the EEMC, with the π0 Pt in [1.25GeV/c,
2.5GeV/c] and Zγγ<0.7 cuts.
Dγγ VS η of π0 Dγγ VS Zγγ
Most of the π0 events are in EEMC single clusters.
For FMS π0 events,Cuts on the single cluster is(1) 1.25GeV/c<Pt<2.5GeV/c(2) Zγγ < 0.7
21
π0 like event (single cluster)• PP part for EEMC
Mass of single cluster Leading and sub-leading tower energy over cluster energy
Zγγ is energy sharing between leading two towers.
1.25GeV/c < Pt<2.5GeV/c
(1) 1.25GeV/c < Pt<2.5GeV/c.(2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85].(3) Zγγ < 0.65
π0 candidates
22
π0 like event (single cluster)• dAu part for EEMC
Mass of single cluster Leading and sub-leading tower energy over cluster energy
Zγγ is energy sharing between leading two towers.
1.25GeV/c < Pt<2.5GeV/c
(1) 1.25GeV/c < Pt<2.5GeV/c.(2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85].(3) Zγγ < 0.65
π0 candidates
Xuan Li 23
MB data and simulation comparison• EEMC pp MB single cluster simulation.
ratio is Leading and sub-leading tower energy over cluster energy.Zγγ is energy sharing between leading two towers.
Simulation Simulation
Data
Data
Xuan Li 24
MB data and simulation comparison• EEMC pp MB single cluster propeties.
MB simulationMB data
Xuan Li 25
MB data and simulation comparison• EEMC pp MB single cluster invariant mass.
(1) 1.25GeV/c < Pt<2.5GeV/c.(2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85].(3) Zγγ < 0.65
scale different
Simulation Data
Xuan Li 26
MB data and simulation comparison• EEMC dAu MB single cluster invariant mass.
(1) 1.25GeV/c < Pt<2.5GeV/c.(2) Ratio of leading plus sub-leading tower energy over cluster energy in [0.5,0.85].(3) Zγγ < 0.65
scale different
Simulation Data
Xuan Li 27
Azimuthal correlation (FMS-BEMC)• FMS photon pair Pt > 2.5GeV/c and mass<0.2 GeV/c2. BEMC
di-cluster 1.25GeV/c < Pt < 2.5GeV/c and mass<0.2GeV/c2.
Fms triggered pp data Fms triggered dAu dataUnc
orre
cted
Coi
ncid
ence
Pro
babi
lity
(rad
ian
-1 )
Width 0.710 ± 0.030 Width 0.733± 0.041
Xuan Li 28
Azimuthal correlation (FMS-BEMC)• FMS photon pair Pt > 2.0GeV/c and mass<0.2 GeV/c2. BEMC
di-cluster 1.0GeV/c < Pt < 2.0GeV/c and mass<0.2GeV/c2.
Fms triggered pp data Fms triggered dAu dataUnc
orre
cted
Coi
ncid
ence
Pro
babi
lity
(rad
ian
-1 )
Width 0.815 ± 0.019 Width 0.752± 0.031
Xuan Li 29
Azimuthal correlation (FMS-EEMC)• FMS photon pair Pt > 2.5GeV/c and mass<0.2 GeV/c2. EEMC di-
cluster 1.25GeV/c < Pt < 2.5GeV/c and mass<0.2GeV/c2.
Fms triggered pp data Fms triggered dAu data
Unc
orre
cted
Coi
ncid
ence
Pro
babi
lity
(rad
ian
-1 )
Width 0.961 ± 0.127 Width 0.817 ± 0.196
Xuan Li 30
Azimuthal correlation (FMS-EEMC)• FMS photon pair Pt > 2.0GeV/c and mass<0.2 GeV/c2. EEMC di-
cluster 1.0GeV/c < Pt < 2.0GeV/c and mass<0.2GeV/c2.
Fms triggered pp data Fms triggered dAu data
Unc
orre
cted
Coi
ncid
ence
Pro
babi
lity
(rad
ian
-1 )
Width 0.833 ± 0.048 Width 1.032 ± 0.179
Xuan Li 31
Azimuthal correlation (FMS-EEMC)• FMS photon pair Pt > 2.5GeV/c and mass<0.2 GeV/c2. EEMC
single cluster 1.25GeV/c < Pt < 2.5GeV/c and mass<0.2GeV/c2.
Fms triggered pp data Fms triggered dAu dataUnc
orre
cted
Coi
ncid
ence
Pro
babi
lity
(rad
ian
-1 )
Width 0.731 ± 0.021 Width 0.935 ± 0.061
Xuan Li 32
Azimuthal correlation (FMS-EEMC)• FMS photon pair Pt > 2.0GeV/c and mass<0.2 GeV/c2. EEMC
single cluster 1.0GeV/c < Pt < 2.0GeV/c and mass<0.2GeV/c2.
Fms triggered pp data Fms triggered dAu data
Unc
orre
cted
Coi
ncid
ence
Pro
babi
lity
(rad
ian
-1 )
Width 0.840 ± 0.015 Width 1.039 ± 0.053
Xuan Li 33
Summary• To find the 3rd point from FMS-EEMC azimuthal
correlation to approach gluon density at low x.• BEMC di-cluster π0 like correlation results are
consistent with Ermes’s correlation results.• There are π0 like hints in the EEMC tower clusters.
To do• To add in ESMD information to get clearer π0 events. • Need suggestions and help for he ESMD calibration.• Work on the
Xuan Li 34
Backup
Xuan Li 35
Motivation
FMS-FMS correlation
FMS-EEMC correlation
FMS-BEMC(TPC) correlation
Triggering on the forward rapidity π0, the rapidity of the associated π0 is correlated with the soft parton involved in the partonic scattering.
• Provide direct sensitivity to gluon density at 0.001< x < 0.02.
Xuan Li 36
Event display• Run 8 dAu fms triggered data.
EEMC BEMC
Xuan Li 37
Cluster width definition• BEMC• Unfold the barrel, and put in the Rϕ, Z plane.
Z
X(Y)
R
ϕ
Z
Rϕ
Large width
Small width
Xuan Li 38
Cluster width definition• EEMC• In xy plane.
X
Y
Large width
Small width
X
Y
Xuan Li 39
dAu FMS triggered data • FMS di-photon invariant mass.
With FMS photon pair which has mass less than 0.2GeV/c2 and Pt larger than 2.5 GeV/c.
Xuan Li 40
EEMC cluster property in dAu data• Single cluster tower multiplicity, energy, η and φ.
Xuan Li 41
BEMC cluster property in dAu data• Single cluster tower multiplicity, energy, η and φ.
Xuan Li 42
π0 like event (single cluster)• EEMC pp fms triggered single cluster mass.
Xuan Li 43
π0 like event (single cluster)• EEMC dAu fms triggered single cluster mass.
Xuan Li 44
MB data and simulation comparison• EEMC dAu MB single cluster simulation.
ratio is Leading and sub-leading tower energy over cluster energy.Zγγ is energy sharing between leading two towers.
Simulation Simulation
Data
Data
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