Parton Distributions, Experiments

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Parton Distributions, Experiments
Introduction
Unpolarized Parton Distribution Functions (PDF)
Helicty difference PDFs

Helicty flip Transversity
EIC

Matthias Grosse Perdekamp, RBRC Lightcone 2002,
Los Alamos
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Motivation
Explore fundamental structure of matter Nucleon
Nucleon as laboratory to study QCD
o Sum rules o Evolution o o hard scattering

Input to the study of Fundamental Interactions
at Hadron (or HI) Colliders
o Tevatron/LHC o Interpretation of data
requires errors (eg. high x,Q2 events at
HERA, high pT jets at CDF)

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Example
CDF Inclusive Jet Cross Section vs ET
F. Abe, et.al, Phys.Rev.Lett. 77(1996)438
Range of available PDFs does not correctly
estimate PDF uncertainties.
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NLO QCD Fit with Error propagation
M. Botje, DIS2000 using Zeus and H1 data.
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CTEQ6
J. Pumplin et.al JEHP 0207012 (2002)
New Data Sets Neutral Current H1, Zeus,
D0 inclusive jets
E866 Drell/Yan d/p
CCFR F2, re-analyzed Old Data Sets BCDMS,
NMC CCFR F3, E605
Drell/Yan CDF W-lepton
asymmetry CDF inclusive
jets
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Channel Overview
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R.S. Towell et. Al, Phys.Rev. D64(2001)05002
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CTEQ6M
J. Pumplin et.al JEHP 0207012 (2002)
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CTEQ6M Uncertainties
J. Pumplin et.al JEHP 0207012 (2002)
Zeus/H1
D0-Jet
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CTEQ6M vs Experiment
J. Pumplin et.al JEHP 0207012 (2002)
D0 Jet Cross Section
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CTEQ6M vs Experiment
J. Pumplin et.al JEHP 0207012 (2002)
ZEUS F2
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Uncertainties at the Tevatron II/LHC
PDF related uncertainties W, Z
Higgs 4 5
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Compare Unpolarized and Polarized Data Sets
g1
F2
105
10
10
103
1
102
Q2 (GeV2)
Q2 (GeV2)
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Helicity Difference PDFs with Errors
J. Blümlein, H. Böttcher, Nucl.Phys.
B636(2002),225
Gluon Spin Contribution is unknown!
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Polarized PDFs from SMC QCD Analysis
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HERMES Results on high pT Hadron Pairs
(theoretical errors unspecified)
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Scale Dependence of Cross Sections in Gluon
Distribution Measurements
HERMES (hadron pairs)
COMPASS (hadron pairs)
RHIC (direct photon)
E708 (direct photon)
CDF (direct photon)
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Future Measurements
Polarized pp
Polarized DIS
STAR, PHENIX
HERMES, COMPASS, E161, EIC, TESLA-N
TESLA-N
pQCD at low x
Hadron Production
PHENIX
Single and Di-Jets
EIC
Heavy Flavors
Photo production of charm and high pT hadron
pairs
HERMES COMPSASS E161
Direct Photon
STAR
Jet Photon
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Sensitivity of future Gluon Polarization
Measurements
Plot provided by E.C. Aschenauer
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Near Future Inclusive Hadron Asymmetries
NLO QCD applicable down to pT2GeV!
Data vs pQCD with different factorization scales
Scale dependence of pQCD calculations in channels
relevant for measurements PHENIX vs
HERMES and COMPASS
HERMES (hadron pairs)
2µ (factorization scale)
COMPASS (hadron pairs)
µ
µ/2
RHIC (direct photon)
PHENIX (direct photon)
PHENIX (inclusive hadrons)
Statistical errors only
CDF (direct photon)
CDF direct photon
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Impact of RHIC ALL Measurement in Incl. Had.
Production in 2003

• Comparison of projected PHENIX ALL measurements
  (200GeV, 3pb-1) with asymmetries obtained from
  the GRSV maximal and standard gluon polarization.

W. Vogelsang
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The first RHIC Polarized Proton Run

• New detector components
• Integrated Luminosity

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Projected Statistical Error for AN Measurement

• 10 x precision of previous best measurement
  (E704)
• High pT at midrapidity permits pQCD
  interpretation
• Bounds on the product of transversity quark
  distributions and the Collins Heppelman
  fragmentation function.

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Transversity Distributions
probe
Hard Scattering Amplitudes
On Transversity
Transversity distributions remain
last unmeasured leading twist distributions
does not mix with gluons under evolution
Incoming proton
First lattice QCD result
S. Aoki, M. Doui, T. Hatsuda and Y. Kuramashi
Phys.Rev. D56 (1997)433 More recently S.
Capitani et.al. Nucl. Phys. B (Proc. Suppl.) 79
(1999) 548
Access to transversity distributions
(helicity flip!)
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Avenues to Transversity
Polarized pp
Polarized DIS
RHIC/BNL
HERA/DESY, SPS/CERN, EIC, TESLA-N
(Approved Transversity Programs)
COMPASS
STAR
HERMES
EIC
TESLA-N
PHENIX
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Drell Yan at RHIC
J.Ralston and D.E. Soper, Nucl. Phys. B152,
109(1979)
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CHF at HERMES
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TESLA-N
250 GeV electrons on polarized fixed targets, 100
fb-1
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TESLA-N Interference Fragmentation
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Collins Effect at EIC
Projected errors on A in 5 z- bins
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EIC kinematic coverage
X-Q2 Coverage of the present DIS facilities shown
in comparison to a Electron Ion Collider
(EIC) Ep50-250 GeV, Ee5-10 GeV
Fixed target muon DIS Fixed target electron DIS
For e-A Unpolarized low x means For
For Polarized e-p low x means lower than SMC
measured x
HERA kinematic limit
DIS
EIC LARGE LUMINOSITY
PHOTOPRODUCTION
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Nuclear effects in nucleon structureE665, NMC
SLAC Collaborations
F2D/F2A

• Fermi motion
• EMC effect
• Enhancement
• Shadowing
• Saturation?

Region of Shadowing and saturation hardly have
data with Q2gt 1 GeV2
Low Q2!
An e-A Collider will measure these regions!
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Statistical Precision possible with EICT. Sloan
T. Sloan

• Statistical Precision Possible with EIC
• NMC data F2(Ca/D)
• EIC data with L1 inv.pb
• Also extends the measurements in to the low x
  region keeping the Q2gt1 GeV2!
• Region of saturation? color glass
  condensate?

EIC 1 inv. pb
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Result of Di-Jet analysis at NLOG. Radel A. De
Roeck, A. Deshpande, V. Hughes, J. Lichtenstadt
Statistical accuracy shown for EIC (HE)
for 2 luminosities Detector smearing effects
studied NLO analysis for Di-Jet Included

• Easy to differentiate between different scenarios
  of DG Improves DG by factor of 3
• Combined analysis Di-Jet pQCD analysis of g1
  DG constrained by these two together further
  improves the uncertainties by additonal factor of
  3
• Effectively factors of 10
  impovement in DG can be expected!

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Parity Violating Structure Functions g5

• Unique measurement with EIC (HE)
• Identified by missing neutrino momentum huge
  asymmetry in detector
• Complementary measurement to RHIC SPIN

In EIC (HE) kinematics
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Measurement Accuracy PV g5 with EICJ. Contreras
et al.
Assume 1) Input GRV Polarized PDFs 2) xF3 is
measured well by that time 3) 4fb-1
luminosity (1.5 months run) If e and e-
possible then one can have g5() as
well. Separate flavors Delta u, Delta d etc.
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A Case for EIC

• Explore an absolutely new regime of QCD An e-A
  collider will provide a unique opportunity to
  explore fundamental and universal aspects of QCD.
• Measurements would be essential to fully
  understand the QGP already being studied at RHIC
  now, also physics at LHC later.
• An e-A collider will also allow us to explore
  with great precision inclusive measurements that
  have not been pursued beyond the fixed target
  experimental era. It would also enable, for the
  first time, a wide range of semi-inclusive
  measurements in a nuclear environment .

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A Case for EIC (cont.)..

• A polarized e-p scattering facility with variable
  sqrt(s) will allow a) at high sqrt(s) a
  new region in the x-Q2 to be explored for the
  spin DIS. It will address issues that no other
  present or future approved facility will address.
  
• b) in the already measured x-Q2 range the
  high luminosity of EIC will allow us to settle
  lots of yet uncertain issues regarding the proton
  spin!
• Detector and its surrounding experimental area,
  details of
• the accelerator design To_Do!
• If the facility is built at BNL, RHIC will
  become a unique facility where particle nuclear
  physicists can do experiments of their choice
  e-A., e-p, polarized e-p, p-A, polarized p-p,
  A-A.

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Polarized Collider RHIC
RHIC pC Polarimeters
Absolute Polarimeter (H jet)
Siberian Snakes
Spin Rotators
2 ? 1011 Pol. Protons / Bunch e 20 p mm mrad
Partial Siberian Snake
LINAC
BOOSTER
Pol. Proton Source 500 mA, 300 ms
AGS
AGS Internal Polarimeter
200 MeV Polarimeter
Rf Dipoles
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Conclusions
Quality of PDFs permits quantitative predictions
with solid errors of Tevatron II and LHC physics.


Many open questions at hard scales
A-dependence, saturation, flavor
structure, spin structure, transversity,
semi-inclusive and exclusive processes.




New facilities HERMES, COMPASS, SLAC, Jefferson
Lab, RHIC spin with exciting possibilities in the
near future.