frank ellinghaus university of colorado (for the phenix collaboration) dis 2008
DESCRIPTION
Recent PHENIX results on p + , p - and h production in polarized pp collisions at RHIC at s=200 GeV. Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008 April 7-11, London, UK. Spin Sum Rule: The latest…. DSSV, arXiv: 0804.0422 - PowerPoint PPT PresentationTRANSCRIPT
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Recent PHENIX results on and production in polarized pp collisions
at RHIC at s=200 GeV
Frank Ellinghaus
University of Colorado
(for the PHENIX Collaboration)
DIS 2008
April 7-11, London, UK
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Frank Ellinghaus, University of Colorado
Spin Sum Rule: The latest…
DSSV, arXiv: 0804.0422First “global” (DIS+SIDIS+pp) analysis!HERMES, arXiv: 0802.2499
Gluons carry half the momentum.Do they carry half the spin?
G small in measured range.Gluon orbital momentum? Contribution at small or large x?
PHENIX 0 (large gg contribution) does not constrain negative gluon scenariosvery well -> charged pions, direct photons
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Frank Ellinghaus, University of Colorado
: enhanced sensitivity to G and s?
• DIS -> s small and negative• SIDIS HERMES (PRL 92:012005,2004) -> s zero or small and positive for x>0.03• Latest HERMES result (arXiv:0803.2993) -> s zero or small and positive for x>0.03
• DSSV uses latest FFs from DSS, both fits include the HERMES SIDIS Data -> node at about 0.02• DNS also included (HERMES) SIDIS, but has less flexible func. form and uses (quite different) FFs from KKP and Kretzer
Size of s important for total quark spin contribution
( 2 )uu dd ss
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Frank Ellinghaus, University of Colorado
PHENIX Detector
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Frank Ellinghaus, University of Colorado
The PHENIX Detector for Spin Physics
Central Detector:• detection
– Electromagnetic Calorimeter: PbSc + PbGl, < |0.35|, = 2 x 90
•
– Drift Chamber– Ring Imaging Cherenkov Detector
Muon Arms:• J
– Muon ID/Muon Tracker ()•
– Electromagnetic Calorimeter (MPC)
Global Detectors:• Relative Luminosity
– Beam-Beam Counter (BBC) – Zero-Degree Calorimeter (ZDC)
• Local Polarimetry - ZDC
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Frank Ellinghaus, University of Colorado
PHENIX longitudinally polarized pp Runs
Year s [GeV] Recorded L Pol [%] FOM (P4L)
2003 (Run-3) 200 .35 pb-1 27 1.5 nb-1
2004 (Run-4) 200 .12 pb-1 40 3.3 nb-1
2005 (Run-5) 200 3.4 pb-1 49 200 nb-1
2006 (Run-6) 200 7.5 pb-1 55 690 nb-1
2006 (Run-6) 62.4 .10 pb-1 48 5.3 nb-1
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Frank Ellinghaus, University of Colorado
reconstruction via decay• Energy asymmetry cut: E1-E2 / E1+E2 < 0.7
• pT > 2 GeV
• |zvertex| < 30 cm
• Fit:Gauss+Pol3
2<pT<3 GeV
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Frank Ellinghaus, University of Colorado
Invariant cross section
yp
ypN
effefffBRLppd
dE
T
T
recTrigAccT
),(1111
2
13
3
L = integrated Luminosity, based on Vernier scan using the BBC
BR= Branching ratio: 2 photons = 0.3943 ± 0.0026
fAcc = acceptance function from MC (includes smearing)
effTrig (Minimum Bias data) = Trigger efficiency of MB trigger
effTrig (high pT triggered data) = (Trigger effi. MB) x (Trigger effi. high pT
trigger)
effrec = Correct for loss due to photon conversion (~6% in PBSC, ~8% in PbGl) x loss due to cut on shower shape (~4%)
N = number of reconstructed
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Frank Ellinghaus, University of Colorado
facc from Monte CarloAcceptance and smearing correction from MC(also accounts for dead regions in EmCal, minimum cuts on photon energies,…)
Up to 10% acceptance in PbSc for at high pT
dataMC
pT
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Frank Ellinghaus, University of Colorado
Photon/MB Trigger Efficiency
Photon trigger efficiency roughly stable from 4 GeV on (high pT photon trigger threshold is set to 1.4 GeV)
Minimum Bias (MB) trigger efficiency about 80 %
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Frank Ellinghaus, University of Colorado
cross section
• Run 6 cross section analysis in progress, goes up to 20 GeV!• No fragmentation functions (FFs) in the literature!• Enables extraction of FFs from e+e- data and this (large range in pT) pp result ( gluon FFs). • Extraction uses method/code from DSS (de Florian, Sassot, Stratmann, PRD75, 2007)
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Frank Ellinghaus, University of Colorado
FFs - DataExperiment System Energy (GeV) # Points
ALEPH ’92 e+e- 91.2 8
ALEPH ’00 e+e- 91.2 18
ALEPH ‘02 e+e- 91.2 5
L3 ‘92 e+e- 91.2 3
L3 ’94 e+e- 91.2 8
OPAL e+e- 91.2 9
ARGUS e+e- 10 6
CELLO e+e- 35 4
HRS e+e- 29 13
JADE ’85 e+e- 34.4 1
JADE ‘’90 e+e- 34.9 3
MARK II e+e- 29 7
PHENIX 2 p+p 200 12
PHENIX 3 p+p 200 6
PHENIX ’05 prelim. p+p 200 19
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Frank Ellinghaus, University of Colorado
FFs - ComparisonDescribes e+e- data very well over a large range in energies.
Will include low-energy high-precision(prelim.) BABAR data and PHENIX RUN 6 crosssection (25 data points out to 20 GeV) soon.Hope for HERMES SIDIS data……
preli
mina
ry
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Frank Ellinghaus, University of Colorado
Cross section @ 200 GeV
PHENIX Run-05 Preliminary
200 GeV
NLO pQCD calculation ( = pT) by M. Stratmann (uses this FF, so more a self-consistency check)
subprocess fraction needed forextraction of G
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Frank Ellinghaus, University of Colorado
/ 0
has (slightly) enhanced sensitivityto gg (when compared to 0) as expected
• Enhanced gg contribution leads to larger asymmetries than for 0
• sizeable differences in the asymmetry only for max/min scenarios• With G small in currently measured region the difference between and asymmetries is small compared to the current stat. error.
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Frank Ellinghaus, University of Colorado
Access to s?
gg
...su sd sg
...uu dd ud
ug ug dg dg
Up to 10% contribution from strange quarks….(Caution: Potentially large uncertainty on s-quark FF due to absence of SIDIS data!)
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Frank Ellinghaus, University of Colorado
Inclusive Asymmetries in pp X
NRN
NRN
PPA
YBLL
1
L
LR
Relative luminosity R using beam-beam counters
2 < pT < 3 GeV/c
M(MeV)
3 < pT < 4 GeV/c 4 < pT < 5 GeV/c 5 < pT < 6 GeV/c
M(MeV)M(MeV) M(MeV)
r
ArAA
BGLL
BGLL
LL
1
BG
BG
NN
Nr
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Frank Ellinghaus, University of Colorado
Access to G: Add the pieces…
2 2~LL gg qg qqA a a q G aG q
Access to polarized gluon distribution function via double helicity asymmetry in inclusive polarized pp scattering:
Measure from DISsubprocess asym+frac (FFs)
p p X
Max and min scenarios excluded by
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Frank Ellinghaus, University of Colorado
Cross section - pQCD applicability
RUN5 200 GeV -- 0
• Charged pion cross section so far only extracted from MB triggered data set; PID with TOF ->low pT only• Also charge separated cross sections extracted by PHENIX• “high” pT triggered (EmCal+RICH) data set; charged pions begin firing the RICH at pT~4.7 GeV, cross section extraction in progress …
PRD76:051106,2007
• 0: pQCD seems at work, with still sizeable scale uncertainties for pT<5 GeV
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Frank Ellinghaus, University of Colorado
+, –, 0 and the sign of G
0
0 LL LL LLG A A A
0
d d dD D D
0
0 LL LL LLG A A A
Especially in the region where qg scattering is dominant (pT > 5 GeV),the increasing contribution of d quarks (d<0) leads to:
“Model independent” conclusionpossible once enough data is available.
Fraction of pion production
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Frank Ellinghaus, University of Colorado
Comparison to model calculations
0 ,LL LLG A A
• Charge separated FFs (DSS, PRD75, 2007) available using SIDIS data (HERMES preliminary); Calculations by W. Vogelsang•
0 LL LLG A A
• New Run 6 (2006) result in agreement with Run 5 (2005)
• More data needed-> Projection for Run 9 (2009) w/o maybe additional higher pT point
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Frank Ellinghaus, University of Colorado
Direct Photons at s=200 GeV
Run-5
q
g q-> small unc. from FFs-> better access to sign of G (q times G)
Theoretically clean “Golden Channel” is luminosity hungry…
Dominated by qg Compton:
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Frank Ellinghaus, University of Colorado
Summary
• Charged pion and data are getting ready to be included in (the next round of) global QCD fits, thanks to new/improved FFs….some more data needed too.