Recent Spin Results from STAR

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Recent Spin Results from STAR
OGAWA, Akio
From Collaboration
Working Group Meeting on Future pp and Spin
Physics at RHIC 7 Oct 2005, BNL
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The Relativistic Heavy Ion Collider at
Brookhaven National Laboratory
R-HI New state of matter QGP De-confinement po
larized proton Nucleon Spin Structure Spin
Fragmentation pQCD RHIC is a QCD lab
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Polarized Proton Operation at RHIC
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The Collaboration
Solenoid Tracker At RHIC
615 collaborators 52 institutions 12 countries
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Nucleon Spin
Spin Sum Rule
1/2 1/2 DS DG LL
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STAR detector

• Solenoidal Magnet
• B 0.5 T

• Tracking Detectors
• Time Projection Chamber hlt1.6
• Forward TPC 2.5lthlt4.0
• Silicon Vertex Tracker hlt1

CTB
ZDC
ZDC

• Trigger Detectors
• Beam-Beam Counters 3.4lthlt5
• Zero-Degree Calorimeter h6

(BBC)
Blue(proton) beam
Yellow(proton) beam

• E-M Calorimeters - installation in stages
• to be completed before 2006
• Barrel EMC hlt1
• Endcap EMC 1.0lt h lt2.0
• Forward Pion Detector 3.3lthlt4.1

Cutway side view of the detector
where pseudorapidity h-ln tanq/2
STAR Upgrade Plans Time of Flight, Forward
Meson Spectrometer, Forward Tracker, Micro-Vertex
Detector
STAR is adding lots of EM calorimetry to detect
high-energy ?, e?, ?0
TPCEMC for jet reconstruction


BBC scaler board system for
relative luminosity and polarization monitoring
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Jet reconstruction at STAR
- via TPC pT for charged hadronsEMC ET for e-m
showers
1) Jets reconstruction - midpoint cone algorithm
(Tevatron II) seed energy 0.5 GeV, cone angle R
0.4 in h-f splitting/merging fraction f0.5

• 2) Trigger used in this analysis - High Tower
• ET gt 2.4 GeV deposited in one tower (Dh x Df )
  (0.05 x 0.05)
• additional requirement of BBC coincidence.

• 3) Cuts on
• charged tracks h lt 1.6 and pT gt0.1 GeV/c
  
• jets pT jet gt 5 GeV/c , 0.2lt jet h (det) lt0.8
• background Ejet(neutral)/Ejet(total)lt 0.9
  (2004) and lt 0.8 (2003)
• z-vertex lt 75cm (2003) and lt 60cm (2004)
• tower ETgt3.5 GeV software threshold (only 2004
  cross section)

EMC on-line event displaydi-jet event
4) Data set 0.4 pb-1 (2003 and 2004) recorded
luminosity ltPbgt 0.3 (2003) and
ltPbgt 0.4 (2004)

• 5) Final statistics (after cuts) for
• cross section 42k jets (2004)
• ALL asymmetry 125k (2003) and 162k (2004)
  jets

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Uncorrected per-event yield
Allows data/MC comparison before luminosity For
HT, include trigger pre-scale

• Reasonable agreement between data/MC
• 10 weighted pythia samples
• Slope difference
• Short term incorporated into sys. uncertainty
• Long term iterative re-weighting of MC sample

DNP2005 M.Miller,MIT
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Data vs. MC
Red ? pythia gstar Black ? data All error bars
statistical
High tower trigger pt (jet) gt10 GeV/c
R
EM energy
charged energy
f
DNP2005 M.Miller,MIT
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Cross section for inclusive jet production
25 5 From simulations. Consistent result
obtained from di-jet evts

• Bins of width 1-sigma (resolution) ? purity
  of 35 over range on the diagonal.
• Motivates application of bin-by-bin correction
  factors

(MC)
DNP2005 M.Miller,MIT
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Bin-by-bin correction factors
measured
Simulation
true
ejet decreases c(pT) resolution increases
c(pT) eTrig 1 e-2 at pT-jet 5 GeV
1 at pT-jet 50 GeV

• MB data statistics limited
• More advanced unfolding techniques currently
  under study

DNP2005 M.Miller,MIT
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Preliminary results for the cross section in
inclusive jet production in pp at sqrt(s)200
GeV vs NLO Calculation

• MB and HT data agree in overlap region
• NLO QCD - Fortran code from
  hep-ph/0404057 (Jager et al.)
• Rcone0.4, CTEQ 6.1 mF mR pT

• 50 systematic uncertainty from energy-scale
  (dominant) shown.
• Other sources of systematic uncertainties
  (smaller, not shown) normalization, BBC trigger
  efficiency, background contribution,
• Agreement (within systematics) over 7 orders of
  magnitude

DNP2005 M.Miller,MIT
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Double Longitudinal Spin Asymmetry Measurements
Statistical significance

• Require concurrent measurements
• magnitude of beam polarization, P1(2)
  RHIC
  polarimeter(s)
• direction of polarization vector at
  interaction point
• relative luminosity of bunch crossings with
  different
• spin directions
  STAR
• 
  
• spin dependent yields of process of interest
  Ni and Nij

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Double spin asymmetry ALL(preliminary) results in
inclusive jet production in pp collisions at
sqrt(s)200GeV

• Consistent results from 2003 and 2004 analyses
• Results limited by statistical precision
• Total systematic uncertainty 0.01 (STAR) beam
  polarization (RHIC)

Sources of systematic uncertainties background
contribution, trigger bias, relative luminosity,
residual (non-longitudinal) asymmetries, bunch to
bunch systematic variations (random pattern
analysis) beam polarization
DNP2005 J. Kiryluk,MIT
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Double spin asymmetry ALL(preliminary) results in
inclusive jet production in pp collisions at
sqrt(s)200GeV
jet cone0.4, 0.2lthjetlt0.8
)
) Predictions B.Jager et.al,
Phys.Rev.D70(2004) 034010
Results limited by statistical precision Total
systematic uncertainty 0.01 (STAR) beam pol.
(RHIC)
DNP2005 J. Kiryluk,MIT
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Cross checks - e.g. (2004) parity violating
asymmetries
Consistent with zero - as expected All other
xcheck asymmetries were found consistent with zero
DNP2005 J. Kiryluk,MIT
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Run5 data under analysis right now and Run6 STAR
projection
2005
2006
Start collecting di-jet sample developing
necessary ? - ?0 discrimination algorithms for
future direct photon and ?jet measurements.
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Lambda polarization in longitudinally polarized
pp collisions at STAR

• Theoretical predictions (e.g. Xu, Liu, Liang,
  PRD65, 2002) for Lambda polarization (at
  high pT gt13GeV/c and at sqrt(s)500 GeV ) - very
  small but sensitive - in a model dependent way -
  to polarized parton distributions (Ds)
• L reconstruction at STAR via decay channel
  Lgp?(Br64)
• - combining TPC tracks with opposite charges
• cuts for tracks and decay vertex topology
• ltxFgt0.008 ltpTgt 1.5 GeV/c
• Data sample (after all cuts) 20032004
• 30k Lambda and 30k anti-Lambda

See talk by Q. Xu, LBNL Shandong Univ.
(tomorrow!)
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STAR Detector
TPC -1.0 lt ? lt 1.0 Forward-TPC 2.8 lt ??? lt
3.8 BBC 2.2 lt ??? lt 5.0 FPD ? 4.1 and
3.6

• Upgraded Forward ?? Detector (FPD)
• Pb-glass EM calorimeter
• (from IHEP Protovino, used in E704)
• Shower-Maximum Detector (SMD)
• Preshower

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Mass resolution 20MeV We understand gain 2
level Efficiencies is almost purely geometrically
determined
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Forward p0 production in hadron collider
p0
Ep
p d
qq
EN
qp
p Au
xgp
xqp
qg
EN
(collinear approx.)

• Large rapidity p production (hp4) probes
  asymmetric partonic collisions
• Mostly high-x valence quark low-x gluon
• 0.3 lt xqlt 0.7
• 0.001lt xg lt 0.1
• ltzgt nearly constant and high 0.7 0.8
• Large-x quark polarization is known to be large
  from DIS
• Directly couple to gluons A probe of low x
  gluons

NLO pQCD Jaeger,Stratmann,Vogels
ang,Kretzer
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pp?p0X cross sections at 200 GeV
pQCD applicability / factorization / scale
dependence?

• The error bars are point-to-point systematic and
  statistical errors added in quadrature
• The inclusive differential cross section for p0
  production is consistent with NLO pQCD
  calculations at 3.3 lt ? lt 4.0
• The data at low pT are more consistent with the
  Kretzer set of fragmentation functions, similar
  to what was observed by PHENIX for p0 production
  at midrapidity.

NLO pQCD calculations by Vogelsang, et al.
D. Morozov (IHEP), XXXXth Rencontres de Moriond
- QCD, March 12 - 19, 2005
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pQCD scaling of cross section
pT, xF and ?s dependences of cross section and
pQCD scaling Similar to ISR analysis J.
Singh, et al Nucl. Phys. B140 (1978) 189.
Run5 online p0 reconstruction on ?s 410GeV data
STAR published and preliminary p0 cross sections
in forward rapidity at ?s200GeV
pQCD scaling gives B4 (FF modification of Pt
will increase B)
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Large Analyzing Powers at RHIC

• First measurement of AN for forward p0 production
  at ?s200GeV

• Similar to FNAL E704 result at ?s 20 GeV
• In agreement with several models including
  different dynamics

STAR collaboration, hep-ex/0310058, Phys. Rev.
Lett. 92 (2004) 171801

• Sivers spin and k? correlation in initial state
  (related to orbital angular momentum?)
• Collins Transversity distribution function
  spin-dependent fragmentation function
• ? suppressed? (hep-ph/0408356)
• Qiu and Sterman (initial-state) / Koike
  (final-state) twist-3 pQCD calculations

First shown at spin2002

• pT dependence?
• xFlt0?
• AN with mid-rapidity correlation?

• Spin dependence in jet?
• Heavy flavors??
• Related to gluon saturation???

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Measurement of AN for mid-rapidity leading
charged particle production at ?s200GeV

• Statistical error based on 6.1M events
• primary track multiplicity gt3
• average polarization P - 8 , Q - 14

Not sensitive to L monitor
PRELIMINARY
Spin2002 J. Balewski(IUCF)
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Transverse Single Spin Asymmetries BBC
(Preliminary) Results


AN BBC ltcos fgt p1 ANCNI p0
e(BBC) (x10-3)
e(BBC) (x10-3)
AN BBC 0.67(8)x AN CNI 1 3.9 lt h
lt 5.0
AN BBC 0 3.4 lt h lt 3.9
e(CNI) (x10-3)
e(CNI) (x10-3)

• Unexpected AN of unknown origin measured with
  the BBC
• Strong pseudorapidity dependence of AN for
  xFgt0 and AN 0 for xFlt0
• de(syst) lt de(stat)

Spin2004 J. Kiryluk (UCLA/MIT)
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AN(xF) in run5 at vs200 GeV
Spin2005 D. Morozov(IHEP)

• Run5 data
• PBeam45(online), L0.4 pb-1
• Using online Polarization
• AN consistent with run3 data
• Nonzero effect at xFgt0.4
• Zero for negative xF

• Analysis includes
• Clustering analysis
• Fit to parameterized shower shape
• Applying cuts
• Etot gt 20 GeV
• N? 2
• Z?? E1-E2/(E1E2) lt 0.7
• Fiducial volume gt 1/2 cell from edge
• 0.07 lt m?? lt 0.3 GeV/c2
• Gains are determined from p0 peak position for
  each tower
• Energy dependent gain correction
• Run/Luminosity dependent gain correction
• MC to data comparison

• To do
• Study of systematic errors
• Include single arm data for consistency

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AN(pT) in run3run5 at vs200 GeV
Online calibration of CNI polarimeter

• Combined statistics from run3 and run5 allowed to
  distinguish nonzero effect in AN(pT) plot
• There is an evidence on C/pT dependence at xFgt0.4
• Fit C 0.07 0.01
• Theoretical predictions needed to compare
  constrain on Sivers function?
• To do systematics study

Spin2005 D. Morozov(IHEP)
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Separating xF and pT dependence

• 10 week of transverse polarization running at
  STAR in run6 expect to yield ?L dt ? 10pb-1 with
  ?50 beam polarization ? reduce statistical
  errors dAN by gt4 compared to run-3 data
• enables measurement of AN(pT) at fixed xF with
  FPD
• Calculations of fixed-xF AN(pT) by U.dAlesio and
  F. Murgia (private communication) based on work
  described in PRD 70 (2004) 074009

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Semi-inclusive pp
Inclusive hadron production Collins Sivers
Mixed Sivers DF measurements Di-jet far
side di-hadron kT balance Jet AN (one
40GeV p0 .vs. two 20GeV p0) Photon AN Heavy
meson AN Transversity measurements Near
side di-hadron correlation (with Collins FF from
Belle) Jet/hadron ATT DY
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Gluon Sivers function from di-jet kT balance
Directly measuring initial state kT by
looking at 2 jets leads to
1/pT none-suppressed signal for Sivers function
Jet 1
10/pb, P50 (run6)
AN? ST ? k?
Jet 2
D. Boer and W. Vogelsang, Phys.Rev. D 69 (2004)
094025 T. Henry, J. Phys. G30, S1287 (2004).
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What can a larger calorimeter do?
With FPD module size and electronic dynamic
range, have gt95 probability of detecting second
photon from p0 decay. --gt Capabilities for Direct
photon particle correlation / jet heavier
mesons measurements
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Forward Meson Spectorometer (FMS) Physics
GoalsThese we know we can do from FPD analysis
of p0

• 1. Measure gluon distributions xg(x) in protons
  and gold nuclei from 0.001ltxblt0.1
• Check universality of xg(x) in region of overlap
  with DIS (0.02ltxblt0.1)
• 2. Characterize correlated pion distributions as
  a function of Q2 to search for onset of
  saturation effects
• Is Au a Color Glass Condensate (CGC)?
• 3. Resolve the origin of large transverse spin
  asymmetries in p?p -gt ?0x for forward ?0
  production

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Probing the low-x gluon density in the Au nucleus
G. Rakness, for STAR hep-ex/0507093
Showed suppression of forward p0 in dAu
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STAR forward upgrade plan
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New FMS Calorimeter Lead Glass From FNAL E831 804
cells of 5.8cm?5.8cm?60cm Schott F2 lead glass
Loaded On a Rental Truck for Trip To BNL
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Conclusions

• First preliminary results for jet cross section
  and jet ALL
• Preliminary Lambda polarization study at mid
  rapidity is shown
• More results from forward p0 production
• Expect more physics with upcoming runs with
  improved luminosity polarization, together with
  upgrades of detectors
• Full BEMC ready for run6, together with trigger
  upgrades
• FPD in run6, FMS run7 at forward rapidity
• RUN6 STAR request
• 10/pb transverse spin
• 20/pb longitudinal spin
• Some AuAu if pp goal is archived early
• DAQ upgrade (run8) Tracking upgrades (run9/10)