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STAR. Spin Physics Results from RHIC. M. Grosse Perdekamp, UIUC. International Workshop on Hadron Structure and Spectroscopy CRNS, Paris April 4 th -6 th , 2011 . AnDY. pp2pp. Spin Physics Results from RHIC. Preliminaries: Facility Status QCD & PDFs vs Data - PowerPoint PPT Presentation
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M. Grosse Perdekamp, UIUC
Spin Physics Results from RHIC
International Workshop on Hadron Structure and Spectroscopy
CRNS, ParisApril 4th -6th , 2011
STARSTAR
pp2pp
AnDY
Preliminaries: Facility Status QCD & PDFs vs Data
Gluon spin distribution Inclusive hadron and jet results QCD analysis Low x & x-dependence with di-jets and rapidity separated di-hadrons
W-production in polarized p-p First results from pp W eν
Transverse Spin Inclusive AN
Channels isolating Collins or Sivers effects Drell Yan measurements in Akio Owaga’s talk
Spin Physics Results from RHIC
RHIC Status: Running Polarized p-p at √s= 500 GeV through 4-8/15
3
Lu
min
osit
y in
Rela
tive U
nit
es
Time in Store [days]
impact from3rd collisionpoint
4 RHIC fills, last week of March First full length 500 GeV run
P ~ 45 % (max above 50%)goal is P ~ 50%
L ~ 5 x 1031 cm-2s-1
goal is L ~ 10 x 1031 cm-2s-1
o AnDY commissioned successfullyo muon-W trigger in PHENIX in operation
o ∫Ldt ~ 40% of planned, due to major hardware failure in cryo-system (repaired).
4
NLO pQCD Cross Sections vs RHIC data for Different √s and Rapidity Intervals
√s = 200 GeV
∆ PHENIX π0, η = 0∙ Brahms π+ ,η = 2.95 ⌷ STAR π0 ,η =
3.7- - - - - NLO pQCD
√s = 62.4 GeV
See analysis in De Florian, Vogelsang, Wagner PRD 76,094021 (2007) and Bourrely and Soffer Eur.Phys.J.C36:371-374 (2004)
o PHENIX π0, η = 0-------- NLO pQCD
Good agreement between inclusivehadron cross sections from RHIC data and pQCD calculations !
pT [GeV]pT [GeV]
(I) Gluon Spin Distribution Inclusive hadron and jet results
QCD analysis
Low x & x-dependence with di-jets and rapidity separated di-hadrons
6
ALL for Inclusive Hadrons & Jets at mid-Rapidity η ~ 0 : constrain ΔG(x) at 0.05 < x < 0.2
ALL for neutral pions and jets vs DSSVde Florian, Sassot, Stratmann,Vogelsang PRD 80:034030,2009
x-range for ALLπ0 in 3 pT bins
Courtesy Swadhin Taneja, Stony Brook
other channels in STAR andPHENIX: eta, charged hadrons,ALL(“charm”) at mid-rapidityALL(J/ψ) for η~ 2.
7
ΔG(x) from DSSV Global QCD Analysis
RHIC
Range
0.05<x<0.2
Large-x
x≥0.2
Small-x
x≤0.05
ΔGtrunc[0.05,0.2] ≈ 0 since node at x≈0.1
Data constrains only truncated first moment of ΔG(x) in x-interval [0.05,0.2], but not functional form at low or high x
ΔGtrunc in large-x region constrained to be small by requirement that ΔG(x) ≤ G(x); at Q2=10 GeV2: ΔGtrunc[0.3,1.0] ≤ 0.03
At small x, ΔG(x) can differ from DSSV beyond errors without violating funda-mental constraints
ΔGtrunc[0.05,0.2] = ∫ ΔG(x) dx = 0.0050.2
0.05
+0.051
-0.058-0.058-0.058-0.058
x ΔG(x)
de Florian, Sassot, Stratmann,Vogelsang PRD 80:034030,2009
Next steps: ALL for di-jets in STAR resolve xq, xgprojections for 500 GeV and ∫Ldt = 300 pb-1 P=70%
o Information on x1 and x2, forward jets
give access to lower x !
o
De Florian, Frixione, Signer and VogelsangNPB 539 (1999) 455 and PC for present calc.
sMxx /21
Courtesy STAR
9
Extending ΔG(x) to Lowest x with Forward di-Jets or High pT di-
HadronsE.g. back-to-back neutral pion pairs in the PHENIX forward EMC
Associate particle, pT,2
Trigger particle, pT,1
dφ
back-to-back: selects di-jets
Back-to-back hadrons: trigger (pT,1) and associate (pT,2<pT,1) in separate jets: large forward boost
Central Arm
(|η|<0.35)
x1 >> x2
Jet -1 (π0, pT,1)
forward EMC (3.1<|η|<3.9)
Jet 2 (π0, pT,2)
500M PYTHIA events ≈ 0.014 pb-1 , only hard QCD processes, soft processes eliminated by
pT cuts (study by Cameron McKinney, UIUC)
enhances q-gfraction to ~ 60%
Selecting x2 with pT Cuts: x2 Decreases and q-g Fraction Increases with Magnitude of pT
cut
pT,1>1.0 GeV/c, pT,2>0.5 GeV/c<x2> ≈ 0.014
x2x1
pT,1>2.0 GeV/c, pT,2>1.0 GeV/c<x2> ≈ 7.2*10-3
pT,1>3.0 GeV/c, pT,2>1.5 GeV/c<x2> ≈ 4.8*10-3
log x
di-hadron pT cuts and resulting <x2>
11
pT,1>3 GeV, pT,2 > 1.5 GeV error bars are statistical only
Projected ALL(π0) in MPC for different ΔG(x) at low x
for ∫Ldt = 300 pb-1, √s = 500 GeV (RHIC W program, 2011 to 2015)
Increasing Δgtrunc [10-4,0.05]
ΔGtrunc= -.1 ΔGtrunc= -.2 ΔGtrunc= -.5
ΔGtrunc [10-4,0.05] = -0.1 will be observable
First Forward EMC ALL , Run 2009 at √s=200 GeV and Projections for Run 2011, √s=500
GeV
12
ALL forward EMC clusters run 2009
DSSV NLO
DSSV-MAX PYTHIA
GSC NLO
ALL forward clusters, projected 2011
First step towards acquisition of large integrated luminosity for ΔG(x) at small x !
(II) W-production in polarized p-p pp W eν first results
pp W μν look at ongoing run
Quark and Anti-Quark Helicity Distributions from Inclusive AL
e,μ in W-Production
• Large Q2, knowledge of FFs not needed
• pQCD analysis of inclusive lepton AL
• DSSV analyzed MC data of 200 pb-1 and 800 pb-1 from STAR and PHENIX
• Significant improvement of knowledge with 200 pb-
1
De Florian at Berkely RSC meeting Nov, 2009
First exploratory run at√s=500 GeV in 2009P ~ 35%∫Ldt ~ 9 pb-1
15
Jacobian Peak for e- and e+
STAR, run 2009, √s= 500 GeV: Parity Violating AL in p+p high pT e
AL for e- and e+
Not yet (!) sensitive to quark andanti-quark helicity distributions
Phys.Rev.Lett. 106 (2011) 062002
16
W-Cross Sections for p-p: PHENIX & ATLAS
Consistent with NNLO QCD
Phys.Rev.Lett. 106 (2011) 062001 arXiv:1012.5382 [hep-ex]
17
News from Present p-p Run at √s = 500 GeV
First full length 500 GeV run
P ~ 45 % (max above 50%)goal is P ~ 50%
L ~ 5 x 1031 cm-2s-1
goal is L ~ 10 x 1031 cm-2s-1
o AnDY commissioned succesfullyo muon/W trigger in PHENIX in operation
o ∫Ldt ~ 40% of planned, due to major hardware failure in cryo system (repaired).
PHENIX Muon Trigger Installed & Operating
RPCs in Urbana (NSF)
RPCs in PHENIX (NSF)
muTr trigger electronics(JSPS)
FPGA basedlevel-1 triggerprocessors
PHENIX Muon Trigger Performance
muTracker trigger efficiencies RPC-Inner Ring Efficiency
problems to be solved: RPC-gas -> mixture & pressure differentials timing -> RPC south is 1 beam clock late
Taking data with muTr part of trigger in run 2011, use RPCoffline for background rejection
First Look at Data from Fast Production (Ralf Seidl)
Arbitrary normalization
(III) Transverse Spin
Inclusive AN
Collins or Sivers effects
AN in Very Forward Neutron Productionusing the Zero Degree Calorimeter
neutron
Large negative SSA observed for xF>0
Diffractive physics Highly useful as local polarimeter for PHENIX
22
At Hard Scale: AN 0 , QCD Test !?
4q 10, 20,3m example, N
qN AGeVsMeV
s
mA
23
Experiment: Sizeable SSA Observed over Large Range of Scales !
Experiment: AN >> 10-4 for 4 GeV < √s < 200 GeV for charged pions !
from Christine Aidala, Spin 2008 andDon Crabb & Alan Krisch in then Spin 2008 Summary, CERN Courier, 6-2009
ZGS √s=4.7 GeV AGS √s=6.5 GeV FNAL √s = 20 GeV RHIC √s = 200 GeV
π+
π-
Soft effects due to QCD dynamics in hadronsremain relevant up to scales where pQCD canbe used to describe the scattering process!
24
AN vs xF almost unchanged for√s=19.4, 62.4 and 200 GeV
25
Origin of Large SSA for Hard Scattering --Two Solutions: Final State vs Initial State
(I) “Transversity” quark-distributions and Collins fragmentation
Correlation between proton- und quark-spin and spin dependent fragmentation
),()( 221
kzHxq
(II) Sivers quark-distribution+
Correlation between proton-spin and transverse quark momentum
)(),( 21 zDkxf h
qqT
Collins FFQuark transversespin distribution
Sivers distribution
(III) Initial or final state twist-3+
Qiu/Sterman and Koike
STAR, PRL-92:171801, 2004
+ unified picture: Ji, Qiu, Vogelsang and Yuan in PRL-97:082002, 2006
First measurement atRHIC √s = 200 GeV
26
BRAHMS: AN for Charged Pions vs pT and xF at √s=62.4 GeV and √s=200 GeV
200 GeV
√s=200 GeV
√s=62.4 GeV
0.4<pT<0.6 GeV/c 0.5 pT<0.6 GeV/c 0.6 pT<0.8 GeV/c 0.8 pT<1.0 GeV/c 1.0 pT<1.2 GeV/c
0.5<pT<0.75 GeV/c1.0<pT<1.25 GeV/c 1.25<pT<1.5 GeV/c 1.5<pT<2.0 GeV/c 2.0<pT<2.5 GeV/c
AN increases withxF (valence quarks)
AN increases with pT ? Limited pT range!
Decrease as ~1/pT expected is not observed.AN constant from pT>2.5 GeV. Need more statistics to extend measurement to pT > 4 GeV !
Positive xF Negative xF
Consistent with zero for all pT
STAR Run 2008: pT Dependence of AN at √s=200 GeV Ogawa at CIPANP 2009
Expectations for AN with PHENIX MPC and Transverse Spin Running in 2012 or
2013
28
Red: Zhong-Bo Kang possible pT dependence if all even orders of twist expansion contributeBlue: pT dependence if sub-leading twist dominates
K p
Large AN for K- significant Sivers asymmetries for sea quarks ?!
Large AN for anti-Proton unexplained.
BRAHMS: AN for Charged Pions ,Kaons and Protons at √s=200 GeV
Another Surprise: AN for Eta Mesons larger than for Pions !
STARSTAR0.361 0.064NA
0.078 0.018NA
GeV 200
s
Xpp
AN(η) > AN(π0) for 0.55 < xF < 0.75
Possibly large effectsin the fragmentation foreta-mesons?
STAR arXiv:0905.2840 (Heppelmann, DIS08)
31
Understanding of AN in terms of Collins and Sivers Effect:
Work in Progress! Future goal: Extract Sivers and transversity quark distributions from global anlaysis to all SIDIS, pp and e+e- data!
Present work: Extract Sivers + transversity from SIDIS and e+e- and predict AN in pp
Presently: Poor agreement with many problems to solve! Universality, evolution, pdf and fragmentation functions not sufficiently known.
For example, note the impact of un-polarized FFs thick line DSS thin line Kretzer
STAR π0
BRAHMS π+,-
Global analysis of SIDIS & e+e-
Anselmino, Boglione, D’Alesio,Kotzinian, Murgia, Prokudin, TurkPhys. Rev. D75:05032,2007
AN calculation from D’Alesio, 2008
Measurements to Isolate Different Mechanisms o Transversity & Collins o Sivers
33
Ideas for Measurements of Transversity Observables
at RHIC
][
][
Xpp
Xhjetpp
Xpp
Xllpp
hemisphere
hemisphere
Drell Yan:Required luminosity not available at RHIC.
Spin dependent Lambda-FF unknown.Measure Λ-FF in e+e- ?
Collins effect in jets; possible in STAR ? hadron ID at high p, z- and ϕ-resolution ?
Di-hadron intereference fragmentation function. IFF data available from e+e- Belle !
34
Interference Fragmentation –IFF- for Di-Hadrons at Mid-Rapidity in
PHENIX
AUT compatible ~0 withpresent statistics
Dilution from gg processes!
Future:
Update with more statistics from runs 2012 and 2013
extend measurements in the forward direction for smaller g-g process fraction and large x !
With 2012 & 2013 statistics
35
IFF Measurement in e+e- at BELLE
1 2( ) ( )jet jete e X
Artru and Collins,
Z. Phys. C69, 277 (1996)
Boer, Jakob, and Radici,
PRD67, 094003 (2003) q1
quark-1 spin
electron
positron
q2
quark-2 spinzpair-1
zpair-1
z1,2 relative pion-pair momenta
ϕpair-1ϕpair-21
1 2
2 θ
22 2
12 1 1 1 1 2 22
sin~ ( , ) ( , )
1 cos pair pair pair paira H z M H z M
PHENIX & STAR collaborators have joined Belle: BNL-Illinois-Indiana-RBRC-RIKEN
PreliminaryPreliminary
Preliminary
Preliminary
PreliminaryPreliminary
Preliminary
Preliminary
Preliminary
Belle IFF- Asymmetries vs Hadron Pair Momentum Fraction zi
9x9 z1 z2 binning
z1
a12
BNL-Illinois-Indiana-RBRC-RIKEN
to be publishedthis month …
37
Ideas for Measurements of Sivers Observables at RHIC
llpp
Xjetpp
Xpp
Xjetpp
Xflavorheavypp
Xjetjetpp
Xhpp
0
Precision measurement of AN at mid-rapidity.
Back-to-back correlations for jets.
AN for inclusive jets.
AN for heavy flavor.
AN for direct photons.
AN in jet-photon production.
AN in Drell Yan.
significant improve-ments from upgrades: forward calorimeters+ silicon vertex detectors
New Experiment: AnDY
38
AN from 0 and h+/- at Central Rapidity
PRL 95, 202001 (2005)
Anselmino et al, Phys. Rev. D 74 094011
Constrain gluon Sivers effect using PHENIX 2002 0 data !
Process Contribution to 0, η=0, s=200 GeV
39
AN from 0 Update
• pT range extended from 5 to 12 GeV/c
• Results consistent with previous PHENIX analysis• Statistical uncertainties reduced by more than
factor of 30
Impact of 2006 + 2008 Data Sets
u + d quarks Sivers w. no gluon or sea quark contribution.Low pT pi0 at mid-rapidity is not sensitive to valence quark Sivers function
Gluon Sivers parameterized to 1 sigma of data
Maximized Gluon Sivers functionViolates <kT> of partons = 0
Sea quark Sivers maximized + Gluon Sivers function
Naïve expected impact of new data.
0.02 < xSampled < 0.08
Theoretical analysis to be carried out.
41
AN in Di-Jet Production in STAR
zx
y
180º
proton spin
1S
Di-jet pT
Additional kT kick to jet axis from Sivers effect Boer & Vogelsang, PRD 69, 094025 (2004)
parton
kK
Gluon radiation
Di-jet pT
STAR: PRL-99:142003,2007
Di-jet AN consistent with 0
42
Summaryo Gluon Spin contribution constraint for 0.05 < x < 0.2 use di-jet and di-hadron measurements to probe x-dependence ΔG(x) and forward jet production to reach low x, x~0.001.
o W-program has started with electrons (STAR & PHENIX) and muons (PHENIX). Luminosity accumulation will take 3-4 runs.
o Precision data on AN are available. Exciting new Drell Yan experiment at IP2: AnDY (see Akio Ogawa’s talk). Initial measurements to isolate Collins -and Sivers- asymmetries. Much improvement from detector upgrades and increased statistics.
43
Backup
44
STAR Run 2006: pT Dependence of AN at √s=200 GeV PRL 101,222001
For given η strong correlation between xF and pT:
AN(pT)integratedover xF
AN(pT, xF)
AN increases with pT up topT ~ 3 GeV/c -- Models: AN ~ 1/pT
PHENIX: AN vs XF for 0’s at √s=62.4 GeV
AN = 0 for xF < 0 no sizeableasymmetries at small x!
Larger forward asymmetries at higher pseudo-rapidity, η ?
Limited by statistics and correlations between xF, pT and η !
Sivers Effect in Heavy Flavor Production
Heavy flavor production gives sensitivity to gluon Sivers effect . Significant improvement with vertex detector upgrades. Work needed to connect theory and experimental observable.
Anselmino et al, PRD 70, 074025 (2004)
Gluon Sivers=0
Gluon Sivers=Max
Calculations for D mesons
Measurement for -
47
A RHIC and US-Japan Contribution to Transverse SpinAnalysis: Measurement of the Collins Effect in e+e- Annihilation into Quarks at Belle BNL-Illinois-RBRC-RIKEN
q1
quark-1 spin
electron
positron
q2quark-2
spin
e++e- π+ + π- + X
~ Collins(z1) x Collins (z2)
Belle Collinsasymmetries & global fit
Collins FF extracted from Belle data.
Measurement of the Collinseffect in e+e- at Belle:
48
Collins Effect in Quark FragmentationJ.C. Collins, Nucl. Phys. B396, 161(1993)
q
momentum hadron relative : 2
z
momentum hadron e transvers:
momentum hadron :
spinquark :
momentumquark :
h
sE
EE
p
p
s
k
h
qh
h
h
q
qs
k
hph
,
Collins Effect:Fragmentation of a transversely polarizedquark q into spin-less hadron h carries anazimuthal dependence:
hp
sin
qh spk
49
General Form of Fragmentation Functions
h
qhh
hqhqh
h
q zM
spkpzHzDpzD
ˆ ),()(),( 2,
1,
1
Number density for finding hadron h from a transversely polarized quark, q:
unpolarized FF Collins FF
IFF- a12 vs Invariant Mass8x8 m1 m2 binning
50
PreliminaryPreliminary
Preliminary
Preliminary
Preliminary Preliminary
Preliminary
PreliminarySystematic errors shown.a12 increases with m1 and m2
reaches |a12 | ~ 0.1 at large mi.
m1 [GeV/c2]
a12
51
The Sivers Effect
proton
Sp
Sp
proton
Sivers function:D. Sivers 1990
Sivers:
Correlation between the transverse spin of theproton and the transverse momentum kT of quarks and gluons in the proton (link to orbitalangular momentum?)
M
SkPkxfxqA PTq
TN
)ˆ(
),()( 2211Observed asymmetry:
52
ANphoton+Jet : An Alternative Test of the
Process Dependence of the Sivers Effect at RHIC
Bachhetta, Bomhof, D’Alesio, Mulders, MurgiaPhys.Rev.Lett.99:212002,2007.
Weig
hte
d m
om
en
t of
AN
ph
oto
n+
Jet
no process dependence
Correct process dependence
Measurement: AN in jet-photon productionforward photon η > 2jet -1 < η < 0
Much less luminosity hungry …
NSAC milestone for transverse spin (HP-13, 2015) ! Reachable at STAR. Requires FOCAL upgrade in PHENIX.