1. Nadia Fomin University of Virginia
Inclusive Electron Scattering from Nuclei at x>1 and High Q2 with a 5.75 GeV Beam
Nadia Fomin
University of Virginia
DNP 2005, Hawaii

2. Overview Introduction Physics Background and Motivation
Experimental Overview
Preliminary Results

3. Introduction to Quasi-Elastic Scattering
Scattering from a nucleon
Have access to nucleon momentum distributions
(E, )
(ν, )
(E’, ) σ ν
Inclusive Reaction
Elastic
QES
DIS
Scattering from a single quark
Have access to quark momentum distributions
Scattering
from a nucleus

4. > 1 QES DIS * Intermediate Q2 values Higher Q2 values
Scattering from a nucleon
Scattering from quarks
Y-scaling
X and ξ-scaling
p+q, X2=mn2
X=unknown * A
A-1 A
A-1

5. Quasielastic scattering: an example (Deuterium)
At low ν (energy transfer), the cross-section is dominated by quasi-elastic scattering
As the energy transfer increases, the inelastic contribution begins to dominate

6. X,ξ-scaling
, where
In the limit of ν,Q ∞ , x is the fraction of the nucleon momentum carried by the struck quark, and the structure function in the scaling limit represents the momentum distribution of quarks inside the nucleon.
As Q2 ∞, ξ x, so the scaling of structure functions should also be seen in ξ, if we look in the deep inelastic region.
It’s been observed that in electron scattering from nuclei at SLAC and JLAB, the structure function νW2, scales at the largest measured values of Q2 for all values of ξ, including low ξ (DIS) and high ξ (QES).
As Q2 ∞, ξ 

7. y-scaling: From cross sections to momentum distributions
y-scaling: A more detailed example
(5)
y-scaling: From cross sections to momentum distributions
Scaling : the dependence of the reaction on a single new variable (y), rather than momentum transfer and energy
y is the momentum of the struck nucleon parallel to the momentum transfer
F(y) is defined as ratio of the measured cross-section to the off-shell electron- nucleon cross-section times a kinematic factor

8. Topics we can study at x>1
Momentum distributions of nucleons inside nuclei
Short range correlations (the NN force)
2-Nucleon and 3-Nucleon correlations
Comparison of heavy nuclei to 2H and 3He
Scaling (x, y) at large Q2
Structure Function Q2 dependence
Constraints on the high momentum tail of the nuclear wave function

9. New Frontiers
Existing data
Existing He data

10. E Details
E ran in Hall C at Jefferson Lab with a beam energy of 5.77 GeV and currents up to 80uA
Cryogenic Targets: H,2H, 3He, 4He
Solid Targets: Be, C, Cu, Au.
Spectrometers: HMS and SOS

11. Data Range and Quality
Data has had radiative, and bin-centering corrections applied and the charge-symmetric background has been subtracted
Coulomb corrections remain to be done
Preliminary
Preliminary
The quasi-elastic peak is easily seen at the lowest Q2, but gets suppressed by DIS contributions as Q2 is increased

12. Y-Scaling (Example: Deuterium)
Preliminary
Preliminary
2.5<Q2<7.4 (GeV2)

13. Y-Scaling (Example: Carbon)
Preliminary
Preliminary
2.5<Q2<7.4 (GeV2)

14. x,ξ-scaling Scaling is observed only at low values of x Preliminary
The structure function appears to approach a universal curve
Scaling is observed only at low values of x

15. x,ξ-scaling (continued)
Preliminary
Preliminary
Can better scaling be explained by the role of momentum distributions?
Scaling is observed in two kinds of variables: one that assumes scattering from a quark and the other, scattering from a nucleon. Is this accidental or evidence of duality?

16. Status All the data have been taken
This experiment provides data over an extended kinematic range and significantly improves the 3He and 4He data sets
The mechanism for extracting cross-sections and scaling functions is in place
We hope to have the final results ready by spring

17. E02-019 Collaboration B. Clasie, J. Seely
Massachusetts Institute of Technology, Cambridge, MA
J. Dunne
Mississippi State University, Jackson, MS
V. Punjabi
Norfolk State University, Norfolk, VA
A.K. Opper
Ohio University, Athens, OH
F. Benmokhtar
Rutgers University, Piscataway, NJ
H. Nomura
Tohoku University, Sendai, Japan
M. Bukhari, A. Daniel, N. Kalantarians, Y. Okayasu, V. Rodriguez
University of Houston, Houston, TX
T. Horn, Fatiha Benmokhtar
University of Maryland, College Park, MD
D. Day (spokesperson), N. Fomin, C. Hill, R. Lindgren, P. McKee, O. Rondon, K. Slifer, S. Tajima, F. Wesselmann, J. Wright
University of Virginia, Charlottesville, VA
R. Asaturyan, H. Mkrtchyan, T. Navasardyan, V. Tadevosyan
Yerevan Physics Institute, Armenia
S. Connell, M. Dalton, C. Gray
University of the Witwatersrand, Johannesburg, South Africa
J. Arrington (spokesperson), L. El Fassi, K. Hafidi, R. Holt, D.H. Potterveld, P.E. Reimer, E. Schulte, X. Zheng
Argonne National Laboratory, Argonne, IL
B. Boillat, J. Jourdan, M. Kotulla, T. Mertens, D. Rohe, G. Testa, R. Trojer
Basel University, Basel, Switzerland
B. Filippone (spokesperson)
California Institute of Technology, Pasadena, CA
C. Perdrisat
College of William and Mary, Williamsburg, VA
D. Dutta, H. Gao, X. Qian
Duke University, Durham, NC
W. Boeglin
Florida International University, Miami, FL
M.E. Christy, C.E. Keppel, S. Malace, E. Segbefia, L. Tang,
V. Tvaskis, L. Yuan
Hampton University, Hampton, VA
G. Niculescu, I. Niculescu
James Madison University, Harrisonburg, VA
P. Bosted, A. Bruell, V. Dharmawardane, R. Ent, H. Fenker, D. Gaskell, M.K. Jones, A.F. Lung (spokesperson), D.G. Meekins, J. Roche, G. Smith, W.F. Vulcan, S.A. Wood
Jefferson Laboratory, Newport News, VA

18. Experimental Setup in Hall C
HMS
SOS
Beam Line
Scattering Chamber

19. High Momentum Spectrometer

20. High Momentum Spectrometer
Superconducting magnets in a QQQD configuration
Maximum central momentum of 6.0 GeV/c with 0.1% resolution and a momentum bite of ±10%
Solid angle of 6.7 msr
Detectors
2 sets of Drift chambers
2 sets of x-y hodoscopes
Gas Čerenkov detector
Lead glass shower counter
Pion Rejection of ~75,000 using the Čerenkov and the Lead Glass Shower Counter

21. ξ-scaling : Competing Explanations
One explanation for ξ-scaling is that it’s a consequence of the Bloom-Gilman duality in e-p scattering
An alternative explanation proposed by Benhar and Liuti explains the observed scaling at high ξ-values in terms of y-scaling of the quasi-elastic cross-section.
A third explanation proposed by Sick and Day explains the apparent scaling by the approximate compensation between the contribution from the QE cross-section and the failure of the resonance and DIS contributions at large ξ and Q2.
Bloom and Gilman examined the structure function in the resonance region as a function of ω’=1/x+M2/Q2 and Q2
They observed that the resonance form factors have the same Q2 behavior as the structure functions
The scaling limit of the inelastic structure functions can be generated by averaging over the resonance peaks seen at low Q2
If the same is true of a nucleon inside a nucleus, then the momentum distribution of the nucleons may cause this averaging of the resonances and the elastic peak.
The idea is that the Q2-dependence arises from looking at ξ, rather than y, is cancelled by the Q2-dependence of the final state interactions
Proton Resonance structure functions vs. the deep inelastic limit. Data is from SLAC experiment E133 and the scaling limit is from L.W. Whitlow