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TransversesinglespinasymmetriesatlargeFeynmanxintheSTARexperiment
atRHICMrigankaMouliMondal(fortheSTARCollaboraAon)
InsAtuteofPhysics,Bhubaneswar
LightCone2017,MumbaiUniversity,India
Outline
² TransverseSingleSpinAsymmetries² TheSTARexperimentandForwardMesonSpectrometer(FMS)
² EM-JetsinforwardandcentralrapidityandANmeasurementsatRHICRun11at√s=500GeV
² STARForwardUpgrades
20/09/2017 LightCone2017,MumbaiUniversity,India 2
π0ANMeasurementsatForwardRapidity
22
No indication of falling AN
as pT
as opposed to twist-3 expectations
π0 AN vs p
T
Forward rapidity hadron production
isolation cones
² RisingANwithxF² ANnearlyindependentof√s
TransverseSingleSpinAsymmetry
Inclusiveπ0produc9on
xF=2pZ/√s
20/09/2017 LightCone2017,MumbaiUniversity,India 3
A N
SiversandCollinseffect
}
TABLE VIII Experimental access to the leading twist TMD distributions in SIDIS with unpolarized (U), longitudinally (L)or transversely polarized (T) beam (modulation first subscript) and/or target (modulation second subscript).
Modulation Combination√s Target Observed Measurement
Distribution name GeV type hadron types
sin(φ+ φS)UT h1 ⊗H⊥1 18 d h±, π±,K±,K0 Ageev et al. (2007) and Alekseev et al. (2009a)
Transversity p h± Adolph et al. (2012b) and Alekseev et al. (2010b)
p π±,K± prelim. Pesaro (2011)
7.4 p π±,π0,K± Airapetian et al. (2005b, 2010a)
3.5 n π± Qian et al. (2011)
sin(φ− φS)UT f⊥1T ⊗D 18 d h±, π±,K±,K0 Ageev et al. (2007) and Alekseev et al. (2009a)
Sivers p h± Adolph et al. (2012c) and Alekseev et al. (2010b)
p π±,K± prelim. Pesaro (2011)
7.4 p π±,π0,K± Airapetian et al. (2005b, 2009b)
3.5 n π± Qian et al. (2011)
cos(2φ)UU h⊥1 ⊗H⊥
1 18 d h± prelim. Sbrizzai (2011)
Boer-Mulders 7.4 p π±,K± Airapetian et al. (2012a)
3.5 n π+ Osipenko et al. (2009)
sin(3φ− φS)UT h⊥1T ⊗H⊥
1 18 d h± prelim. Kotzinian (2007)
Pretzelosity 18 p h± prelim. Parsamyan (2011)
7.4 p π±,K± prelim. Pappalardo (2010)
sin(2φ)UL h⊥1L ⊗H⊥
1 18 d h± Alekseev et al. (2010a)
Worm-gear 1 7.4 p π±,π0 Airapetian et al. (2000b, 2001)
d π±,π0,K+ Airapetian et al. (2003)
3.5 n π±,π0 Avakian et al. (2010)
cos(φ− φS)LT g⊥1T ⊗D 18 d h± prelim. Kotzinian (2007)
Worm-gear 2 18 p h± prelim. Parsamyan (2011)
7.4 p π±,π0,K± prelim. Pappalardo and Diefenthaler (2011)
3.5 n π± Huang et al. (2012)
fect from COMPASS and HERMES. The Sivers, Collins,worm-gear and pretzelosity effects are all consistent withzero in the deuteron target data. The Collins and Siverseffects observed in the proton data therefore contain apredominant isovector contribution.We next focus on the Sivers, Boer-Mulders and Collins
effects.
1. The Sivers and Boer-Mulders TMD distributions
The Sivers distribution was first proposed in Sivers(1990) in an attempt to explain the large transverse sin-gle spin asymmetries observed in the 1970s and 1980s. Itdescribes the correlation between the transverse momen-tum kt of the struck quark and the spin S and momentump of its parent nucleon
fq/p↑(x, kt) = f q1 (x, k
2t )− f⊥q
1t (x, kt)S · (kt × p̂)
M. (36)
The kt dependence means that the Sivers distribution issensitive to non-zero parton orbital angular momentum
in the nucleon, though the mapping from Sivers observ-ables to quark (and gluon) orbital angular momentum is(so far) model dependent with present theoretical tech-nology.
The Sivers distribution has the interesting propertythat it is odd under time reversal. Due to this fea-ture, such a correlation was believed to be forbiddenfor more than a decade. Then Brodsky et al. (2002a,b)showed that, with initial- or final-state interactions, theSivers effect could be non-zero in QCD processes. Final-state interactions in SIDIS can generate the azimuthalasymmetry before the quark fragments into hadrons.Shortly afterwards, Collins (2002) realized that initial-state color interactions in the case of Drell-Yan and final-state interactions in the case of SIDIS would lead toa process-dependent sign difference in the Sivers dis-tribution. SIDIS measurements (Adolph et al., 2012c;Airapetian et al., 2005b, 2009b; Alekseev et al., 2010b;Pesaro, 2011; Qian et al., 2011), suggest sizable asymme-tries at the level of about 5−10% for a proton and a neu-tron target, while Drell-Yan measurements are plannedfor the future.
32
Siverseffect:thecorrelaAonbetweenthetransversemomentum(kt)ofthestruckquarkandthespin(S)andmomentum(p)ofitsparentnucleon
Sktp
Siversdistribu9on
Collinseffect:spin-momentumcorrelaAoninthehadronizaAonprocess
0
0.1
0.2
0
0.1
0.2
0.2 0.4 0.6 0.8
A 12
0.2 < z1 < 0.3
AUL
AUC
0.3 < z1 < 0.5
z2
A 12
0.5 < z1 < 0.7
z2
0.7 < z1 < 1
0.4 0.6 0.8
FIG. 20 Collins asymmetry for the double ratios of like-sign(L), unlike-sign (U) and any charged (C) pion pairs fromBelle (Seidl et al., 2008). AUL and AUC are sensitive to dif-ferent combinations of the favored and unfavored Collins frag-mentation functions. The bands indicate the systematic un-certainties.
2. The Collins TMD fragmentation function
The Collins TMD fragmentation function describes aspin-momentum correlation in the hadronization process,sq · (kq × pt), with a hadron produced in fragmentationhaving some transverse momentum pt with respect to themomentum direction k of a transversely polarized frag-menting quark with spin sq (Collins, 1993; Collins et al.,1994). The Collins fragmentation function has beeninvestigated in semi-inclusive lepton-nucleon scatteringand e+e− annihilation. The magnitude of the effect is ap-proximately 5–10%, like that found for the Sivers asym-metries.For e+e− annihilation the chiral-odd Collins fragmen-
tation function enters with a second Collins function inthe opposing jet. The Collins function has been measuredto be non-zero for the production of charged pions ine+e− annihilation at Belle (Abe et al., 2005; Seidl et al.,2008), as shown in Fig. 20, and in recent preliminary datafrom BABAR (Garzia, 2012).In SIDIS the second chiral-odd function is the transver-
sity distribution introduced in Section II and dis-cussed further below (or the Boer-Mulders distribu-tion). The HERMES (Airapetian et al., 2005b, 2010a),COMPASS (Adolph et al., 2012b; Ageev et al., 2007;Alekseev et al., 2009a, 2010b; Pesaro, 2011) and JLabHall A (Qian et al., 2011) experiments have performedSIDIS measurements of the Collins effect. The measure-ments for a proton target are shown in Figs. 21 and 22
−0.05
0
0.05
10−1 0.2 0.4 0.6x
Asin(φ
+ φ
S) U
T
HERMESπ+
π−
z pTh (GeV)0.5 1
FIG. 21 Collins amplitudes for charged pions measuredby HERMES with a proton target; from Airapetian et al.(2010a). The inner error bar represents the statistical un-certainty; the full bar the quadratic sum of statistical andsystematic uncertainties.
for HERMES and COMPASS respectively. (Note thatCOMPASS uses a definition of the Collins angle whichresults in Collins amplitudes with opposite sign to the“Trento convention” of Bacchetta et al. (2004) used byHERMES, JLab and commonly in theoretical papers).There is excellent agreement between the measurementsin similar kinematics. One finds the striking observationthat the Collins amplitude for π− is of similar size to π+
production but comes with opposite sign. This hints atan unfavored Collins function of similar size and oppositesign than the favored one, a situation very different fromthat observed with unpolarized fragmentation functions.
COMPASS 2010 proton data
x−2
10−1
10
p Coll
A
−0.1
−0.05
0
0.05
z0.5 1
positive hadronsnegative hadrons
(GeV)hTp0.5 1
FIG. 22 Collins amplitudes for unidentified charged hadronsmeasured by COMPASS with a proton target (Adolph et al.,2012b). The hadron yield is dominated by pions. Note that adifferent definition of the Collins angle results in amplitudeswith the opposite sign compared to other measurements. Thebands indicate the systematic uncertainties.
3. Probing transversity
The transversity distribution introduced in Section IIdescribes the transverse polarization of quarks within atransversely polarized nucleon. Along with the unpolar-ized and helicity distributions, it survives integration overpartonic transverse momentum and is thus a collineardistribution.The first moment of the transversity distribution is
proportional to the nucleon’s C-odd tensor charge, viz.
34
Scaberedquarku
du uu
X
u
π0,ηπ±,k±
FragmentaAon,ΔDhq
sq=spinofthefragmenAngquarkkq=momentumdirecAonofthequarkpt=transversemomentumofhadronwithrespecttothedirecAonofthefragmenAngquark
ptsq
D. Sivers, Phys. Rev. D 41, 83 (1990) J.C.Collins,Nucl.Phys.B396,161(1993)
SensiAvetoprotonspin-partontransversemo.oncorrelaAons
SensiAvetotransversity(δq)
20/9/2017 SeminaratIOP,Bhubaneswar,India 4
SeparaAngSiversandCollinseffects
needtomovebeyondinclusiveproducAon
• Siverseffect:FullJets,Directphotons,Drell-Yan• Collinseffect:azimuthalorienta9onofpar9cleswithinajet
)(),( 21 zDkxf h
qqT ⋅∝ ⊥⊥
Siversdistribu9on
),()( 221 ⊥
⊥⋅∝ kzHxqδ
CollinsFFQuarktransversespindistribu9on
AN= +
Observedtransversesingle-spinasymmetriesofinclusivehadronscouldarisefromtheSiverseffectorCollinseffect,orfromalinearcombina9onofthetwo
20/09/2017 SeminaratIOP,Bhubaneswar,India 5
RHIC:theworld’sfirstandonlypolarizedprotoncollider
Beams: √s 62.4 - 500 GeV pp
AGSLINACBOOSTER
PolarizedSource
200MeVPolarimeter
HydrogenJetPolarimeter
PHENIXSTAR
SiberianSnakes
SiberianSnakes
SpinFlipper
CarbonPolarimeters
RFDipole AGSInternalPolarimeter
AGSpCPolarimeter
StrongSnake
TuneJumpQuadsHelicalParAalSnake
SpinRotators
For2011:AverageBlueBeamPolariza9on=51.6%(Transverse)Luminosity=22pb-1
20/09/2017 LightCone2017,MumbaiUniversity,India 6
20/09/2017
FPD EM Calorimeter Small cells onlyTwo 7x7 arrays
FMSPbGlassEMCalorimeterpseudo-rapidity2.5<η<4.0Smallcells:Outercells:3.81x3.81cm5.81x5.81cm
ForwardECALinSTAR
LightCone2017,MumbaiUniversity,India 7
PhotonsinFMSTowersàClustersàPhotoncandidates(photons)
(showershapefits)
ForwardMesonSpectrometer(FMS)-2011:--PbglassEMcalorimetercovering2.5<η<4.0--Detect𝜋0,η,directphotonsandjet-likeeventsinthekinemaAcregionwheretransversespinasymmetriesareknowntobelarge.
EM-JetcharacterisAcs
20/09/2017
htempEntries 187224Mean 3.536RMS 1.771
no. photons0 2 4 6 8 10 12 140
10000
20000
30000
40000htemp
Entries 187224Mean 3.536RMS 1.771
nTowersj {energyj>60&&energyj<80}
EM-Jet Energy 60-80 GeVhtemp
Entries 29185Mean 0.2655RMS 0.19
aam0 0.2 0.4 0.6 0.8 10
500
1000
1500
2000
2500
3000
3500 htempEntries 29185Mean 0.2655RMS 0.19
mS {energyj>60&&energyj<80&&zgg<.8&&nTowersj==2}
EM-Jet Energy 60-80 GeV<0.8, no. phootns = 2aaZ
² 2-photonjetsaremostlyπ0
² Eventswithmorethan2photonsshowjet-likeenergyflowγγinvariantmass2-photonEM-jets
dE/d(ΔR)distribuAonofEM-Jets
EM-JetEnergy60-80GeVZγγ<0.8,no.photons=2
#Jets
2-photonEntries 138843Mean 0.06152RMS 0.09392R)
(arb
itrar
y sc
ale)
6dE
/d(
2-photonEntries 138843Mean 0.06152RMS 0.09392
4-photonEntries 572466Mean 0.1064RMS 0.08614
4-photonEntries 572466Mean 0.1064RMS 0.08614
6-photonEntries 522345Mean 0.1566
RMS 0.1049
0 0.2 0.4 0.6 0.8 1
6-photonEntries 522345Mean 0.1566
RMS 0.1049
3-photonEntries 384465Mean 0.07579RMS 0.07095
3-photonEntries 384465Mean 0.07579RMS 0.07095
5-photonEntries 611930Mean 0.1331RMS 0.09701
0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1
5-photonEntries 611930Mean 0.1331RMS 0.09701
7-photonEntries 348054Mean 0.1749RMS 0.1115
)jet,photonsR6d(0 0.2 0.4 0.6 0.8 1
7-photonEntries 348054Mean 0.1749RMS 0.1115
dE/d(ΔR)(arbitraryscale)
p+p√s=500GeVtransversedatasetsJetalgorithm:anA-ktR-parameter:0.7pTEM-Jet
>2.0GeV/cphotonswithpT>0.001GeV/cLeadingEM-Jets:MulA-photonJetswithhighestenergy2.8<ηEM-Jet<4.040GeV<EnergyEM-Jet<100GeV
LightCone2017,MumbaiUniversity,India 8
ANvs.EM-JetEnergy
20/09/2017
² Isolatedπ0’shavelargeasymmetriesconsistentwithpreviousobservaAon(CIPANP-2012StevenHeppelmann)
hbps://indico.triumf.ca/contribuAonDisplay.pycontribId=349&sessionId=44&confId=1383
² Asymmetriesforjetswithphotons>2eventsaremuchsmaller
EM-Jet Energy (GeV)40 50 60 70 80 90
NA
0
0.02
0.04
> 0)F
-Jets (x0/
<0)F
-Jets (x0/
> 0)F
EM-Jets (x
< 0)F
EM-Jets (x
> 0)F
>0.3 (xaa
2-photon-Jets-m
Graph
= 500GeVs @ Bp+p > 2.0 GeV/c
TEMJetp
< 4.0EMJetd2.8 <
STAR Preliminary π0-Jets–2γ-EM-Jetsmγγ<0.3Zγγ<0.82γ-EM-Jets(η+con9nuum)–mγγ>0.3EM-Jets–photons>2
LightCone2017,MumbaiUniversity,India 9
Isolatedπ0:I) reconstructedπ0for2-photonjetII) nophotonwithinphysicalcone(eg.
70mR)ofreconstructedπ0
ANfordifferent#photonsinEM-Jets
20/09/2017
NA
0
0.05
0
0.05
0
0.05
0
0.05
2 3 4 5 6
0
0.05 > 0Fx < 0Fx
STAR Preliminary
2 4 6 8
(GeV/c)TEMJet p
4 6 8
EM-Jet Energy = 40-60 GeV 60-80 GeV 80-100 GeV no. photons = 1 2 3 4 5
² 1-photonevents,whichincludealargeπ0contribuAoninthisanalysis,aresimilarto2-photonevents
² Three-photonjet-likeeventshaveaclearnon-zeroasymmetry,butsubstanAallysmallerthanthatforisolatedπ0’s
² ANdecreasesastheeventcomplexityincreases(moreparAclesinjets)
² ANfor#photons>5issimilartothat#photons=5
LightCone2017,MumbaiUniversity,India 10
ANforcorrelatedcentraljetsandnocentraljetcases
20/09/2017
NA
0
0.05
0.1
<4.0EMJet forwardd2.8 <
< 2.0EMJet centrald-1.0 < > 2.0 GeV/cEMJet central
Tp
0
0.05
0.1
no central EM-Jet central EM-Jet
/2)/<3q6/2)</(
3 4 5 60
0.05
0.1
STAR Preliminary
3 4 5 6 7
0.06
3 4 5 6 7
(GeV/c)EM-JetT
p
EM-Jet Energy = 40-60 60-80 80-100 GeV
3-photon >3-photon 0
/isolated-
² Asymmetriesfortheforwardisolatedπ0arelowwhenthereisacorrelatedaway-sidejet.
LightCone2017,MumbaiUniversity,India 11
JETsatcentralrapidity• EMJetsare
reconstructedinmidrapidityBEMC+EEMC,-1.0<ηEM-
Jet<2.0• BacktobackΔφ
relaAonsusedtofindifthereisanyassociatedjets
2à2partonscabering
ANforπ0andCollinsasymmetriesofπ0
20/09/2017 LightCone2017,MumbaiUniversity,India 12
January 30, 2015 22:33 WSPC/INSTRUCTION FILE S3˙Pan
TSSA of Forward π0 at STAR 3
/ GeVγγM0.05 0.1 0.15 0.2 0.25 0.30
5000
10000
15000
20000
25000datacombined fit
signal0πbackground
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
< 43.0 GeV, Fill15419γγ 38.0 GeV < EγγM
Fig. 1. Distribution of di-photon mass with 38 GeV < Eγγ < 43 GeV, 2.8 < η < 4.0 and energysharing Zγγ < 0.8 (Zγγ = |E1 − E2|/Eγγ). Grey area: signal region; Shaded area: sidebands.
by QCD theory in which π0 emerges as a result of 2 → 2 partonic hard-scattering73
there must be other potential sources that generate the observed isolated π0 with74
large asymmetries. But it should be pointed out that here the reconstructed jet75
is only the electromagnetic component of the full jet. In the future with forward76
detector upgrades at STAR a full jet reconstruction will be possible.77
Fx0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34
NA
-0.01
0
0.01
0.02
0.03
0.04
0.05
> 0F x0πinclusive
< 0F x0πinclusive
5.2% beam pol. scale uncertainty not shown
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
Fx0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34
NA
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06 > 0F x0πinclusive
> 0F x0πisolated < 0.9
EM in jet, Z0π
5.2% beam pol. scale uncertainty not shown
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
Fig. 2. Left: inclusive π0 transverse single spin asymmetries vs xF . Right: compare inclusive π0
AN vs isolated and non-isolated π0 AN .
The pT dependence of inclusive π0 AN can also be used to test theory predictions,78
e.g. from twist-3 expectations AN will always decrease with increasing pT due to79
the nature of higher twist terms. Figure 3 shows AN vs pT for inclusive and isolated80
π0 from two xF bins.81
January 30, 2015 22:33 WSPC/INSTRUCTION FILE S3˙Pan
4 Yuxi Pan, for the STAR Collaboration
/ GeVT
p2 3 4 5 6 7 8
NA
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
< 0.32F 0.24 < x0πinclusive
< 0.32F 0.24 < x0πisolated
5.2% beam pol. scale uncertainty not shown
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
/ GeVT
p3 4 5 6 7 8 9
NA
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
< 0.40F 0.32 < xNinclusive A
< 0.40F 0.32 < xNisolated A
5.2% beam pol. scale uncertainty not shown
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
Fig. 3. Inclusive π0 AN vs pT . Left: 0.24 < xF < 0.32, Right: 0.32 < xF < 0.40.
2.3. Sivers/Collins asymmetries of jet-like events and π0 in jets82
In the transverse momentum dependent framework the observed asymmetries are83
generated through the Sivers5 and Collins6 mechanism. These theories describe84
processes which involve two scales such as di-jet asymmetries7 and azimuthal asym-85
metries of hadrons within jet8. It has been shown that the Sivers function is related86
to twist-3 parton distribution function via an integral relation3, and there exists87
a similar relation between Collins function and twist-3 fragmentation functions2.88
With the same dataset STAR has measured asymmetries of forward EMjets and π089
azimuthal asymmetries within the EMjet.90
Fig. 4. AN of EMjets containing different number of photons.
Figure 4 shows AN of EMjet constructed by applying anti-kT algorithm with91
R = 0.7 on FMS photons. The asymmetries are plotted for jets having only two92
• π0isreconstructedfromFMS• Collinsasymmetriesofπ0relaAvetojetaxisisbeingmeasured
20/09/2017
January 30, 2015 22:33 WSPC/INSTRUCTION FILE S3˙Pan
TSSA of Forward π0 at STAR 3
/ GeVγγM0.05 0.1 0.15 0.2 0.25 0.30
5000
10000
15000
20000
25000datacombined fit
signal0πbackground
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
< 43.0 GeV, Fill15419γγ 38.0 GeV < EγγM
Fig. 1. Distribution of di-photon mass with 38 GeV < Eγγ < 43 GeV, 2.8 < η < 4.0 and energysharing Zγγ < 0.8 (Zγγ = |E1 − E2|/Eγγ). Grey area: signal region; Shaded area: sidebands.
by QCD theory in which π0 emerges as a result of 2 → 2 partonic hard-scattering73
there must be other potential sources that generate the observed isolated π0 with74
large asymmetries. But it should be pointed out that here the reconstructed jet75
is only the electromagnetic component of the full jet. In the future with forward76
detector upgrades at STAR a full jet reconstruction will be possible.77
Fx0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34
NA
-0.01
0
0.01
0.02
0.03
0.04
0.05
> 0F x0πinclusive
< 0F x0πinclusive
5.2% beam pol. scale uncertainty not shown
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
Fx0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34
NA
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06 > 0F x0πinclusive
> 0F x0πisolated < 0.9
EM in jet, Z0π
5.2% beam pol. scale uncertainty not shown
= 500 GeVs + X @ 0π + p -> ↑p
STAR Preliminary
Fig. 2. Left: inclusive π0 transverse single spin asymmetries vs xF . Right: compare inclusive π0
AN vs isolated and non-isolated π0 AN .
The pT dependence of inclusive π0 AN can also be used to test theory predictions,78
e.g. from twist-3 expectations AN will always decrease with increasing pT due to79
the nature of higher twist terms. Figure 3 shows AN vs pT for inclusive and isolated80
π0 from two xF bins.81
• Isolatedπ0 tendtohavesignificantly largerasymmetries thanπ0associatedwithjetacAviAesinthevicinity.
• Sivers (EM-Jets) and/or Collins (π0 relaAve to jet axis) asymmetries areinsufficienttoaccountfortheobservedinclusiveπ0singlespinasymmetries.
..........
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.....
.....
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.....
......
.....
.....
.....
......
.....
.....
.
Backup
.. Backup -Inclusive π0 AUT and background asymmetries
4 / 7
Fx0.15 0.2 0.25 0.3 0.35 0.4 0.45
)Hφ
- Sφsin
(U
TA
-0.01
0
0.01
0.02
0.03
0.04
0.05)
Hφ -
Sφsin(
UTA
background asymmetry
5.2% beam pol. scale uncertainty not shown
> 2 GeVjetT
p
< 4.0jetη2.8 <
< 0.9EM0 < Z
= 500 GeVs + X @ 0π + p -> jet + ↑p
anti-kT R = 0.7STAR Preliminary
EMZ0.3 0.4 0.5 0.6 0.7 0.8 0.9
)Hφ
- Sφsin
(U
TA
-0.01
0
0.01
0.02
0.03
0.04
0.05)
Hφ -
Sφsin(
UTA
background asymmetry
5.2% beam pol. scale uncertainty not shown
> 2 GeVjetT
p
< 4.0jetη2.8 <
= 500 GeVs + X @ 0π + p -> jet + ↑p
anti-kT R = 0.7STAR Preliminary
LightCone2017,MumbaiUniversity,India 13
ANforπ0andCollinsasymmetriesofπ0
SummaryandOutlook² Jetswithisolatedπ0havelargeasymmetry.² ANdecreasesastheeventcomplexityincreases.² Isolatedπ0asymmetriesaresmallerwhenthereisacorrelatedEM-jet
atmid-rapidity.Largeforwardπ0AN:Comesfrom2à2partonscaberingwithsomecontribu9onfromdiffrac9veevents?² Sivers(EM-Jets)and/orCollins(π0relaAvetojetaxis)asymmetriesare
insufficienttoaccountfortheobservedinclusiveπ0singlespinasymmetries.
20/09/2017 LightCone2017,MumbaiUniversity,India 14
q 2015:installaAonofFMS-PreshowerandRomanpots-p+p200GeVlongitudinal&transversep↑+Au/Al200GeVtransverse,Spineffectsindiffrac9on
q 2017:installaAonofFMS-Postshower-p+p510GeVtransverseANforDellYan,directphotons
² 2017:post-showerdetector
ForwardUpgrade(≧2021)Overview
15
Requirements:Ø wideacceptancemid-rapiditydetectorwithgoodPID(p,K,p)Ø forwardrapidi9es(1.0<η<4.5)Ecal+HCal+chargeiden9fica9on
ForwardrapidiAes
• 2.5<η<4.5PreshowerdetectorEMcalorimeter• PHENIXPbScHadroniccalorimeter• L=4λl4-6addiAonallayersofSiliconMicrostripand/orsmall-stripThinGapChamber
backup
20/09/2017 LightCone2017,MumbaiUniversity,India 16
FMS-Jets BEMC+EEMC-Jets
EM-Jet/offAxispT(GeV/c)EM-Jet/offAxispT(GeV/c)
FMS-Jets BEMC+EEMC-Jets
EM-Jet/offAxispT(GeV/c)EM-Jet/offAxispT(GeV/c)
Sun Jan 10 22:25:42 2016
Energy Jet0 50 1000
05
0.1
Pt Jet0 5 10 15 200
05
0.1
15
0.2
h12h12
Jetd2.5 3 3.5 4 4.50
05
0.1
h13h13
Jetq-2 0 2
0
05
0.1h14h14
x F Jet0 0.2 0.4 0.6 0.8 10
05
0.1
15
0.2h15h15
#photons Jet0 5 10 150
0.1
0.2
h16h16
JetaR0 0.5 1 1.5 20
0.2
0.4
0.6
h17h17
in JetaaSig0 5 10 150
0.1
0.2
0.3
0.4h18h18
m0 0.5 1 1.5 20
05
0.1
15
h19h19
z0 0.2 0.4 0.6 0.8 10
05
0.1
15
h110h110
E0 50 1000
0.1
0.2
0.3
pT0 5 10 15 200
0.2
0.4
h112h112
d2.5 3 3.5 4 4.50
0.1
0.2
0.3
h113h113
q-2 0 20
05
0.1h114h114
in JetaaBkd0 5 10 150
0.1
0.2
0.3
0.4h115h115
m0 0.5 1 1.5 20
05
0.1
15
h116h116
z0 0.2 0.4 0.6 0.8 10
05
0.1
15
0.2
h117h117
E0 50 1000
0.1
0.2
pT0 5 10 15 200
0.2
0.4
h119h119
d2.5 3 3.5 4 4.50
0.1
0.2
h120h120
q-2 0 20
05
0.1
15
0.2
h121h121
NLS}aaE L/E {0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
h122h122
}aaj T {0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
h123h123
H NLSq-2 0 2
05
0.1
15
h124h124
E0 50 1000
0.5
1
pT0 5 10 15 200
0.5
1
1.5
2
h126h126
d2.5 3 3.5 4 4.50
0.1
0.2
0.3
0.4
h127h127
q-2 0 2
0.1
0.2
h128h128
Data%
+%MC%
Main%purpose%of%simulaGons%%
JP2%
• Understanding%FMS%data%with%full%PYTHIA%simulaGons%with%standard%STAR%framework.%
• Construct%the%matrix%%-%#true%photon%vs.%#photons%detected%:%This%would%be%used%for%
correcGng%%AN,EM-Jets
%of%a%certain%n-photon-class%from%the%effect%of%probability%
misidenGfying%to%the%other%%%n-photon-clases%
#photons%in%Jets%in%MC%and%data%was%not%matching%:%%
%%%%%%1.%AVenuaGon%was%not%there%in%GEANT%energy%deposiGon%mode.%%GEANT%is%used%with%
an%aVenuaGon%factor.%%%%%
%%%%%%2.%PYTHIA6%is%not%tuned.%Specially,%there%is%no%scope%to%include%%hard%diffracGon.%
#photons%in%Jets%
1/26/16% 5%STAR%CollaboraGon%MeeGng,%BNL%2.PYTHIAtunedependenciesarechecked:HarddiffracAonnotincurrentscopeofPYTHIA6
DatapointcorrecAonsandbeberunderstandingDetectorwithGEANTsimulaAons
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The Relativistic Heavy Ion Collider
PHENIX STAR
Brhams pp2pp
Au+Au + Cu+Au
Polarized p+p, d+Au Polarized p + Au
RHIC is a QCD lab
20/09/2017
1)Heavy-ionProgram--StudymediumproperAes,EoS--pQCDinhotanddensemedium2) RHICbeamenergyscan--searchofcriAcalpoint--chiralsymmetryrestoraAon1) Longitudinalandtransversespinprograms--StudyprotonintrinsicproperAes2) Forwardprogram--spinstructureofproton--Studyoflowxproper/esandsearchforCGCTaggedforwardphysics--StudyelasAcandinelasAcprocesses--InvesAgategluonicexchangesandsearchforgluonicmaber
RHICPhysicsFocus
LightCone2017,MumbaiUniversity,India 18
TSSA–twotheoreAcalframework
20/09/2017
Sivers fct.
Spin-dependenttransversemomentumdependent(TMD)func9onST.(PxkTBrodsky,Hwang,Schmidt,02Collins,02,Ji,Belitsky,Yuan,02+Collinsfragmenta.onfunc.ons
Twist-3quark-gluoncorrela9onsEfremov&Teryaev:1982&1984Qiu&Sterman:1991&1999+Twistthreefragmenta.onfunc.ons
Efremov, Teryaev; Qiu, Sterman
Q ΛQCD QT/PT <<<<QT/PT
Transverse momentum dependent
Q>>QT>=ΛQCD Q>>pT
Collinear/ twist-3
Q,QT>>ΛQCD pT~Q
Efremov, Teryaev; Qiu, Sterman
Need 2 scales Q2 and pt
Remember pp: most observables one scale
Exception: DY, W/Z-production
Need only 1 scale Q2 or pt
But should be of reasonable size
should be applicable to most pp observables
AN(π0/γ/jet)
Efremov, Teryaev; Qiu, Sterman
LightCone2017,MumbaiUniversity,India 19
ANfromfits
day(run) : 90(43) to 90(61) / ndf 2r 8.257 / 10
Prob 0.6037p0 0.018384± -0.006277 p1 0.02641± 0.05524
q-3 -2 -1 0 1 2 3
? +
NB N
? -
NB N
-0.2
0
0.2
0.4day(run) : 90(43) to 90(61) / ndf 2r 8.257 / 10
Prob 0.6037p0 0.018384± -0.006277 p1 0.02641± 0.05524
day(run) : 90(43) to 90(61)EM-JetEnergy=55-57.5GeV
For2-photonisolatedπ0
hndf1Entries 134Mean 17.48RMS 1.848
0 5 10 15 20 25 30 35 40 45 500
10
20
30
40
50
hndf1Entries 134Mean 17.48RMS 1.848
hchi21Entries 134Mean 19.73RMS 6.42
0 5 10 15 20 25 30 35 40 45 500
2
4
6
8
10
12
hchi21Entries 134Mean 19.73RMS 6.42
Mean 1.058
RMS 0.3597
/NDF2r0 0.5 1 1.5 2 2.5
# se
ts0
10
20
30 Mean 1.058
RMS 0.3597 > 0Fx < 0Fx
Foreachsliceofdataaveragedover~18fills.Fitsarewellincontrol.
LightCone2017,MumbaiUniversity,India
² ANiscalculatedfromp0+P×ANcos(ϕ)fitsovereachfillonp0=relaAveluminosityAN=asymmetryP=polarizaAon---AN’sarecorrectedforpolarizaAonvaluesfromRHIC-fills---ANandχ2/NDFarecalculatedoverenArefills
)q(?)+Nq(BN)q(?)-Nq(BN) = q(NA
)qCos(NA× = p0 + P)q(?)+Nq(BN)q(?)-Nq(BN
20/09/2017 20
ANwithmid-rapidityacAviAes
• Case-I:havingnocentraljet• Case-II:havingacentraljet
20/09/2017
η=1.09,2.0η=2.6-4.2
BEMC EEMCFMS
η=-1.0,1.0
CentralEMJets forwardEMJets
towers(BEMC+EEMC):anA-kT,R=0.7,pTEM-Jet
>2.0GeV/c,-1.0<ηEM-Jet<2.0LeadingcentralEM-Jets:JetwithhighestpT
LightCone2017,MumbaiUniversity,India 21
ΔΦcorrelaAonsbetweenforwardandcentralEM-Jets
20/09/2017
² CorrelaAonisstrongerformoreN_photonJets² ForhigherEMJetsenergy,correlaAongrowsstronger
Entries 4163115Mean 2.16RMS 1.676
#Eve
nts
0
50
100Entries 4163115Mean 2.16RMS 1.676
E =40-60 GeV
Entries 2404875Mean 2.18RMS 1.665
0
20000
40000
60000Entries 2404875Mean 2.18RMS 1.665
E = 60-80 GeV
Entries 710428Mean 2.232RMS 1.639
(forward-central EMJets)q6-1 0 1 2 3 40
10000
20000
Entries 710428Mean 2.232RMS 1.639
E = 80-100 GeV
#photons <=2
Entries 7990953Mean 2.313RMS 1.594
#Eve
nts
0
100
200 Entries 7990953Mean 2.313RMS 1.594
E = 40-60 GeV
Entries 6632622Mean 2.384RMS 1.55
0
100
200 Entries 6632622Mean 2.384RMS 1.55
E = 60-80 GeV
Entries 2844054Mean 2.435RMS 1.515
(forward-central EMJets)q6-1 0 1 2 3 40
50
100Entries 2844054Mean 2.435RMS 1.515
E = 80-100 GeV
#photons >=3
NumberofphotonsforforwardEMJets:1,23andmore
EMJetsEnergy
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RHICColdQCDSchedule
STARfuturemeasurements
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