# Presentation: 125104

## Overview of Parton Distribution Functions(with a decided high-xBJ bias)

- Jorge G. Morfín
- Fermilab
- DNP04 - Chicago, IL

## Outline

- Quick review of everything but valence quarks
- The valence quarks
- Look at high-x:
-  Recent indications of more **and** less quarks at high-x?
-  d/u
- How to cleanly measure valence quarks at high-x (and individual sea-quark distributions at all x)

## PDFs from Global Fits

- _Formalism_
- LO, NLO, NNLO DGLAP
- MSbar factorization
- Q02
- functional form @ Q02
- sea quark (a)symmetry
- etc.

- _Data_
- DIS (SLAC, BCDMS, NMC, E665,
-  CCFR, H1, ZEUS, ... )
- Drell-Yan (E605, E772, E866, ...)
- High ET jets (CDF, D0)
- W rapidity asymmetry (CDF)
- N dimuon (CCFR, NuTeV)
- etc.

***f******i ******(x,Q******2******)*** ********* ********* ***f******i ******(x,Q******2******)***

- J. Stirling - Hix2004

## MRST Parton Distributions in the Proton

- Martin, Roberts, Stirling, Thorne

## Comparison of three modern PDF global fits

- Djouadi & Ferrag, hep-ph/0310209

**small ****MRST**** and ****CTEQ**** differences largely understood,** see hep-ph/0211080 - **J. Stirling; Hix2004**

## How has our picture of the PDF’s evolved over the years.With thanks to Wu-Ki Tung - MSU

**Gluon**

## Does the gluon go negative at small x and low Q?    (MRST)

**Gluon**

**Does the gluon go negative at small x and low Q? ****   ****(MRST****)**

## Uncertainty in the Gluon DistributionNormalized to CTEQ6M

- Dashed - CTEQ5HJ
- Dotted - MRST01
- Solid - CTEQ5M

## The non-strange sea quarks

- DY Asymmetry exerts its Influence - NA51 and E866

## Experimental input: (low statistics) data on Dimuon (charm) production in Neutrino-Nucleus scattering.

## A better determination of  should emerge from current full NLO analyses of the CCFR-NuTeV dimuon data.	

- A better determination of  should emerge from current full NLO analyses of the CCFR-NuTeV dimuon data.

- 

## Is the strangeness sector charge symmetric?

- Still no experimental data to decide, one way or the other.

## New CCFR-NuTeV dimuon data that can, in principle, determine s(x) and sbar(x) separately!

## The Valence u Quark:  progression of improvements

## NLO fits to more fixed-target DIS data sets

## HERA exerts its influence 

- HERA exerts its influence

## All in the details now, at least for lower x 

- All in the details now, at least for lower x

## It looks like we know the d and u quark fairly well...right?

## Indication that the valence quarks not quite right at high-x??E866 Preliminary Results (R. Towell - Hix2004)

**x****beam**** distribution measures *****4u + d***** as *****x--> 1.******	***
*	**	**	**	*
**Both MRST and CTEQ *****overestimate***** valence distributions as *****x ****-->**** 1***** by 15-20%.****	****	**
**Possibly related to *****d/u***** ratio as *****x --> 1*****, but requires full PDF-style fit.**
*Radiative corrections have recently been calculated. (Not yet fully applied)*

- xtarget

- xbeam

- OOPS!

## d/u

- Relative Concentration of Valence Quarks in the Nucleon
**d/u**

## Slide 21

## Latest look at d/u...     What’s going on at high-x?

## CTEQ uncertainties in u and d quark fitsTheory uncertainties NOT included

## CTEQ High-x Working Group

- With C. Keppel - Jefferson Lab

## Extraction of d/u using deuterium targets

- involves **nuclear D****2**** corrections**

## What happens when we include (preliminary) E866?

- PRELIMINARY

## Compare 6.1 with E866 to CTEQ5 with deuteron correction (F-S) - time to revisit deuteron corrections...

- PRELIMINARY

## Range of Deuteron Corrections in the Literature

- Wally Melnitchouk:

- This line is what CTEQ used for “Large-x paper”

- (a few somewhat dated)

## Implement full FS instead of approximate line

- and compare with MST correction

- PRELIMINARY

## PRELIMINARY

## E866 discrepancy can be reduced/removed with deuteron corrections, change in d/u ratio looks similar to CTEQ6.1 + E866 fit.

- Extracting d/u will continue to be a problem as long as we must invoke deuteron corrections
- Need final data with radiative corrections, but feeling a bit better about E866...

- Preliminary Impressions of CTEQ High-x Study

## NuTeV Compared to CCFR (currently in PDF fits)at High-x Indicates Effect Opposite to E866

- V. Radescu - DIS04

- nuclear effects?

- OOPS!

## How do we Resolve the High-x Quark Dilemma?

- The cleanest, most straightforward way to study
- high x quarks, including the d/u ratio is with
- /  - proton scattering

## Neutrino - Proton ScatteringNo messy nuclear corrections!

- At high x

*F**2****p** - xF**3****p** = 4xu *

*F**2****p** - xF**3****p** = 4xd** *

*F**2****p** + xF**3****p** = 4xu** *

## Similar Expressions for Neutrino-Nucleon Scattering - What Can We Learn With All Six Neutrino Structure Functions?

- Combining measured values in a given x-Q2 bin, for example

- Using Leading order expressions (for isoscalar target):

## How do we measure Neutrino-Proton Scattering? The MINERA Experiment in the NuMI Beam at FermilabApproved in April

- C, Fe and Pb
- Nuclear targets

**Main Physics Topics with Expected Produced Statistics**
**Quasi-elastic**** ****	****	****	****	****300 K events off 3 tons CH**
**Resonance Production**** ****	****	****	****600 K total, 450 K 1******
**Coherent Pion Production****	********25 K CC / 12.5 K NC**
**Nuclear Effects**** ****	****	****	****	****C:0.6M, Fe: 1M and Pb: 1 M**
**Pert/nonPert and Structure Functions**** ****	****2.8 M total /1.2 M DIS event**
**Strange and Charm Particle Production**** ****	****> 60 K fully reconstructed events**
**Generalized Parton Distributions**** ****	****	****(few K events?)****	****	**

## Both HEP and NP collaborators

- D.  Drakoulakos, P. Stamoulis,  G. Tzanakos, M. Zois
**University of Athens, Athens, Greece**
- D. Casper
**University of California, Irvine, California**
- E. Paschos
**University of Dortmund, Dortmund, Germany**
- D. Boehnlein, D. A. Harris,  M.  Kostin,
- J.G. Morfin, P. Shanahan, P. Spentzouris
**Fermi National Accelerator Laboratory, Batavia, Illinois**
- M.E. Christy, W.  Hinton, C.E .Keppel
**Hampton University, Hampton, Virginia**
- R. Burnstein, A. Chakravorty, O. Kamaev, N.  Solomey
**Illinois Institute of Technology, Chicago, Illinois**
- S.Kulagin
**Institute for Nuclear Research, Moscow, Russia**
- I. Niculescu. G. .Niculescu
**James Madison University, Harrisonburg, Virginia**

- G. Blazey, M.A.C. Cummings, V. Rykalin
**Northern Illinois University, DeKalb, Illinois**
- W.K.  Brooks, A. Bruell, R. Ent, D. Gaskell,,
- W. Melnitchouk,  S. Wood
**Jefferson Lab, Newport News, Virginia**
- S.  Boyd, D.  Naples, V.  Paolone
**University of Pittsburgh, Pittsburgh, Pennsylvania**
- A. Bodek, H.  Budd, J.  Chvojka,  P. de Babaro, S.  Manly,
- K.  McFarland, I.C.  Park, W.  Sakumoto, R. Teng
**University of Rochester, Rochester, New York**
- R. Gilman, C. Glasshausser, X. Jiang, G. Kumbartzki,
- K. McCormick, R. Ransome
**Rutgers University, New Brunswick, New Jersey**
- H. Gallagher, T.  Kafka, W.A. Mann, W. Oliver
**Tufts University, Medford, Massachusetts**
**J. Nelson**
**William and Mary College, Williamsburg, Virginia**

**Red = HEP,  ****Blue = NP,  ****Green = Theorist**

## After initial (parasitic to MINOS) run -would add a Liquid H2/D2(/O/Ar) TargetNOT YET APPROVED FOR THIS

- H_2/D_2

- MINOS Near

- Fid. vol:
- r = 80 cm. l = 150 cm.
- 350 K CC events in LH2
- 800 K CC events in LD2
- 2.5x1020 POT  he- beam.

- Technically **easy/inexpensive** to build and operate.
- Meeting **safety** specifications the **major **effort.

- Planes of C, Fe, Pb
- For part of run

- _≈__ __Statistical Errors  for .7 / 2 year of he-___
-     xBj 	   CH	LH2  	 LD2
**.6 - .65****	****0.6%****	****2.2%****	****1.5%**
**.65 - .7****	****0.7****	****2.6****	****1.7**
**.7 - .75****	****1.0****	****3.7****	****2.5**
**.75 - .8****	****1.3****	****5****	****3**
**.8 - .85****	****2****	****7****	****5**
**.85 - .9****	****3****	****11****	****7**
**.9 - 1.0****	****4****	****14****	****10**

## Summary

- Aside from low x gluon, PDFs fairly well established for x < 0.3-0.4.
- For x  > 0.3,  uncertainty of the gluon grows dramatically.
- (d - u) / (d+u) reasonably constrained by E866 out to x ≈ 0.4.
-  = (s + s) / (u + d) seems to be increasing with x (NuTeV input).
- (s - s) / (s + s) and heavy quarks need further clarification (NuTeV).
-  The valence u-quark is reasonable out to x = 0.5, while the d-quark uncertainty blows up around x = 0.3.  Whoops...E866 & NuTeV!!
- d/u at high-x still uncertain due to spread in deuteron correction.
- BoNuS experiment at Jlab, particularly with upgrade, will help
- THE CLEANEST WAY TO MEASURE d/u:  + p SCATTERING
- The MINERA Experiment at Fermilab, an NP + HEP collaboration, could make a high-statistics measurement of  + p scattering.