Probing Parton Distribution Functions with Neutrinos

1
Probing Parton Distribution Functions with
Neutrinos

• Jorge G. Morfín
• Fermilab
• PDFs in the 21st Century - Seattle, WA
• November, 2004

2
Outline

• Which PDFs need help and where in x?
• Quarks at high-x
• Recent indications of more and less quarks at
  high-x?
• d/u
• How can Neutrinos help?
• What can neutrinos tell us about nuclear PDFs?
• An experiment to address these questions.

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MRST Parton Distributions in the Proton
Martin, Roberts, Stirling, Thorne
4
More Detailed Look at Higher x
5
Comparison of three modern PDF global fits
Djouadi Ferrag, hep-ph/0310209
6
Uncertainty in the Gluon DistributionNormalized
to CTEQ6M
Dashed - CTEQ5HJ Dotted - MRST01 Solid - CTEQ5M
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CTEQ uncertainties in u and d quark fitsTheory
uncertainties NOT included
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d Quarks not bad agreement
Disregard the older results
thanks to Wu-Ki Tung - MSU
9
u Quarks even better agreement but this
doesnt mean we have it right!
thanks to Wu-Ki Tung - MSU
10
An indication that the valence quarks not quite
right at high-x!E866 Preliminary Results (R.
Towell - Hix2004)
xbeam
xtarget

• xbeam distribution measures 4u d as x--gt 1.
• Both MRST and CTEQ overestimate valence
  distributions as x --gt 1 by 15-20.
• Radiative corrections have recently been
  calculated. (Not yet fully applied)
• Possibly related to d/u ratio as x --gt 1.

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Latest look at d/u Whats going on at high-x?
use parametrization that assumes d/u ? 0.
CTEQ6 with E866
CTEQ5 with D2 (F-S) Nuclear correction
thanks to Wu-Ki Tung - MSU
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Latest look at d/u Whats going on at high-x?
thanks to Wu-Ki Tung - MSU
13
How do you measure d/u? Can be extracted from
electroproduction p and n structure functions
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How do you measure F2n?
Uncertainty from nuclear corrections to the
deuteron
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Just to increase our confusion. Latest NuTeV s
Compared to CCFR (currently in PDF fits)at
High-x Indicates Effect Opposite to E866-no help
for d/u
V. Radescu - DIS04
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How do we Resolve the High-x Quark Dilemma?
A clean and straightforward way to study high x
quarks, including the d/u ratio, is with n / n -
proton scattering
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We bring you the axial-vector current.
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Neutrino Structure Functionsn probe d, s, u, c
while n probe u, c, d, s
Reverse for n
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Ability to taste different quarks allows
isolation of flavorsNeutrino - Proton Scattering
At high x
No messy nuclear corrections!
F2np - xF3np 4xu
F2np xF3np 4xu
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Similar Expressions for Neutrino-Nucleus
Scattering What Can We Learn With All Six
Neutrino Structure Functions?
Using Leading order expressions (for isoscalar
target)
Combining measured values in a given x-Q2 bin,
for example
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Nuclear Effects - modified interaction
probabilities
S. Kumano
Fermi motion
valence-quark
original EMC finding
antiquark
shadowing
x
sea quark
valence quark
EXPECTED to be different for n!!
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Difference between n-A and m-A nuclear
effectsValence and Sea Quark nuclear
effectsSergey Kulagin
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How do we measure Neutrino-Nucleus/Proton
Scattering? The MINERnA Experiment in the NuMI
Beam at FermilabApproved by PAC 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 1p
• Coherent Pion Production 25 K CC / 12.5 K NC
• Nuclear Effects C0.6M, 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 gt 60 K
  fully reconstructed events
• Generalized Parton Distributions (few K
  events?)

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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

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
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After initial (parasitic to MINOS) run -would
add a Liquid H2/D2(/O/Ar) TargetNOT YET APPROVED
FOR THIS
Technically easy/inexpensive to build and
operate. Meeting safety specifications the major
effort.
Fid. vol r 80 cm. l 150 cm. 350 K CC
events in LH2 800 K CC events in LD2
2.5x1020 POT/yr he-n beam.
H_2/D_2
MINOS Near
Statistical Errors for .7 / 2 year of he-n /
n 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
Planes of C, Fe, Pb For part of run
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Measuring Six Structure Functions for Maximal
Information on PDFs
y2 FL
R Rwhitlow Neutrino 1 year he-beam Anti-Neutri
no 2 years he-beam
X 0.1 - 0.125 Q2 2 - 4 GeV2 Kinematic cuts in
(1-y) not shown
(1-y)2
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Summary

• Aside from low x gluon, PDFs fairly well
  established for x lt 0.3-0.4.
• For x gt 0.3, uncertainty of the gluon grows
  dramatically.
• The current fits for the valence u-quark is
  reasonable out to x 0.5, while the d-quark
  uncertainty blows up around x 0.3.
• Both E866 and the latest NuTeV s results indicate
  a possible surprise for high-x u d
  quarkshowever in opposing directions!
• d/u at high-x still uncertain due to spread in
  deuteron correction.
• A CLEAN WAY TO MEASURE d/u n/n p
  SCATTERING!
• The MINERnA Experiment at Fermilab, an NP HEP
  collaboration, could make a high-statistics
  measurement of n p scattering.
• MINERnA will also provide the first detailed
  study of nuclear effects with ns including quark
  flavor-dependent nuclear effects.