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

Overview Introduction Physics Background and Motivation Experimental Overview Preliminary Results

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

> 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

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

X,ξ-scaling , where In the limit of ν,Q2 ∞ , 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 

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

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

New Frontiers Existing data Existing He data

E02-019 Details E02-019 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

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

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

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

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

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?

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

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

Experimental Setup in Hall C HMS SOS Beam Line Scattering Chamber

High Momentum Spectrometer

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

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