# Presentation: 202724

## Parton Distributions, Experiments

- Introduction

- Matthias Grosse Perdekamp, RBRC
- Lightcone 2002, Los Alamos

- Unpolarized Parton Distribution Functions (PDF)

-  Helicty difference PDFs

-  Helicty flip: Transversity

-  EIC

## Motivation 

- Explore fundamental structure of matter: Nucleon

- Nucleon as laboratory to study QCD

-  Input to the study of Fundamental Interactions
-  at Hadron (or HI) Colliders

- o  Sum rules
- o  Evolution
- o
- o  hard scattering

- o  Tevatron/LHC
- o  Interpretation of data requires errors...
-     (eg. high x,Q2 events at HERA, high pT jets at CDF)

## Example

- Range of available PDFs does not
- correctly estimate PDF uncertainties.

- CDF Inclusive Jet Cross Section vs ET

- F. Abe, et.al, Phys.Rev.Lett. 77(1996)438

## NLO QCD Fit with Error propagation

- M. Botje, DIS2000 using Zeus and H1 data.

## CTEQ6

- 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

- J. Pumplin et.al JEHP 0207:012 (2002)

## Channel Overview

## R.S. Towell et. Al, Phys.Rev. D64(2001)05002

## CTEQ6M

- J. Pumplin et.al JEHP 0207:012 (2002)

## CTEQ6M Uncertainties

- J. Pumplin et.al JEHP 0207:012 (2002)

- Zeus/H1

- D0-Jet

## CTEQ6M vs Experiment 

- CTEQ6M vs Experiment

- J. Pumplin et.al JEHP 0207:012 (2002)

- D0 Jet Cross Section

## CTEQ6M vs Experiment 

- CTEQ6M vs Experiment

- J. Pumplin et.al JEHP 0207:012 (2002)

- ZEUS F2

## Uncertainties at the Tevatron II/LHC

- PDF related uncertainties
-            W, Z      Higgs
-               4%       5%

## F2

*F**2*

*g**1*

***Q******2****** (GeV******2******)***

***Q******2****** (GeV******2******)***

- Compare Unpolarized and Polarized Data Sets

***10******5***

***10***

***10******2***

***1***

***10***

***10******3***

## Helicity Difference PDFs with Errors

- J. Blümlein, H. Böttcher, Nucl.Phys. B636(2002),225

**Gluon Spin Contribution**
**          ****is unknown!**

## Polarized PDFs from SMC QCD Analysis

## HERMES Results on high pT Hadron Pairs

- (theoretical errors unspecified)

## Scale Dependence of Cross Sections in Gluon Distribution Measurements

- HERMES
- (hadron pairs)

- COMPASS
- (hadron pairs)

- E708
- (direct photon)

- RHIC
- (direct photon)

- CDF
- (direct photon)

## Future          Measurements

- Future          Measurements

**Polarized pp**

**Polarized DIS**

**STAR, PHENIX**

**HERMES,  COMPASS,  E161,  EIC, TESLA-N**

**Hadron Production**

**Heavy Flavors**

**Direct Photon**

**Jet Photon**

**STAR**

**PHENIX**

**pQCD at low x**

**Photo production of charm  **
**and high p****T****  hadron pairs**

**Single and Di-Jets**

**EIC**

**HERMES**
**COMPSASS**
**E161**

- TESLA-N

## Sensitivity of future Gluon Polarization Measurements 

- Plot provided by E.C. Aschenauer

- Sensitivity of future Gluon Polarization Measurements

## Near Future: Inclusive Hadron Asymmetries

- HERMES
- (hadron pairs)

- COMPASS
- (hadron pairs)

- RHIC
- (direct photon)

- CDF
- (direct photon)

-      CDF
- direct photon

-      PHENIX
-  (direct photon)

*Statistical errors  only*

**Scale dependence of pQCD calculations in**
**channels relevant for        measurements:**
**PHENIX vs HERMES and COMPASS**

**Data vs  pQCD with different factorization scales**

-       PHENIX
- (inclusive hadrons)

-  NLO QCD applicable down to  pT=2GeV!

- 2μ (factorization
-        scale)

- μ

- μ/2

## Impact of RHIC ALL Measurement in Incl. Had. Production in 2003

- 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

## The first RHIC Polarized Proton Run

- New detector components
- Integrated Luminosity

## Projected Statistical Error for AN Measurement

- 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.

## Transversity Distributions 

- Transversity Distributions

- (helicity flip!)

**On Transversity:**

- does not mix with gluons under evolution

- 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

**Hard Scattering Amplitudes**

- Transversity distributions             remain
-     last unmeasured leading twist distributions

- Incoming
-   proton

-  probe

**Access to transversity distributions:**

## Avenues to Transversity 

**Polarized pp**

**Polarized DIS**

**RHIC/BNL**

**HERA/DESY, SPS/CERN****, EIC, TESLA-N**

**STAR**

**PHENIX**

- HERMES

- Avenues to Transversity

- COMPASS

**(Approved Transversity Programs)**

- TESLA-N

- EIC

## Drell Yan at RHIC

- Drell Yan at RHIC

- J.Ralston and D.E. Soper, Nucl. Phys. B152, 109(1979)

## CHF at HERMES 

## TESLA-N 

- 250 GeV electrons on polarized fixed targets, 100 fb-1

## TESLA-N:  Interference Fragmentation  

## Collins Effect at EIC

**Projected errors on A in 5 z- bins**

## EIC kinematic coverage

- For e-A Unpolarized “low x” means
- For

**X-Q2 **Coverage of the present DIS facilities shown in comparison to a    Electron Ion Collider (EIC):
-      Ep=50-250 GeV, Ee=5-10 GeV

- PHOTOPRODUCTION

- DIS

- For Polarized e-p “low x” means lower than SMC measured x:

- EIC LARGE LUMINOSITY

- HERA kinematic limit

- Fixed target muon DIS
- Fixed target electron DIS

## Nuclear effects in nucleon structureE665, NMC & SLAC Collaborations 

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

**Region of Shadowing and saturation hardly have data with Q2> 1 GeV2 **

**An e-A Collider will measure these regions!**

- F2D/F2A

- Low Q2!

## Statistical Precision possible with EICT. Sloan

- Statistical Precision Possible with EIC:
-  NMC data F2(Ca/D)
-  EIC data with L=1 inv.pb
-  Also extends the measurements in to the low x region keeping the Q2>1 GeV2!
-  Region of saturation?               color glass condensate?

**EIC 1 inv. pb**

**T. Sloan**

## Result of Di-Jet analysis at NLOG. Radel & A. De Roeck, A. Deshpande, V. Hughes, J. Lichtenstadt 

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

-   Statistical accuracy
-   shown for EIC (HE)
-   for 2 luminosities
-   Detector smearing effects
-   studied
-  NLO analysis for Di-Jet
-  Included

## 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

## Measurement Accuracy PV g5 with EICJ. 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.

## 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 .

## 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.

## Polarized Collider : RHIC

**AGS**

**LINAC**

**BOOSTER**

- Pol. Proton Source
- 500 A, 300 s

**Spin Rotators**

- Partial Siberian Snake

- Siberian Snakes

- 200 MeV Polarimeter

- AGS Internal Polarimeter

- Rf Dipoles

- RHIC pC Polarimeters

- Absolute Polarimeter
-              (H jet)

- 2  1011 Pol. Protons / Bunch
-  = 20  mm mrad

## Conclusions

**Conclusions**

-    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.

- Quality of PDFs permits quantitative predictions with solid errors
- of Tevatron II and LHC physics.