Nuclear Physics Work Group Meeting Report (6/17/05) ● Nine presentations over 4.5 hours. ● Targets – Deuteron: 3 (Gilfoyle, Egiyan, Asryan). – 4 He: 1 (Strauch). – 3 He: 3 (Ilieva, Ireland (2)). – A>4: 2 (Wood, Egiyan, Manly). ● Beams – Electron: 7 (Ireland(2), Manly, Gilfoyle, Egiyan, Asryan, Wood) – Photon: 2 (Strauch, Ilieva)

A Very Preliminary Analysis of the Two- Deuteron Photodisintegration of 4 He Steffen Strauch ● 4 He(g,dd) reaction identified for E = MeV ● Differential cross section. – CLAS: minimum at Q cm =90 o where E2 transition dominates. – Differs from SAL, Bonn at 300 MeV.

● Total Cross Section – s tot = pb. – Agrees with Bonn data at lowest energy

Two-body Breakup of 3 He with Real Photons Yordanka Ilieva ● g 3 He -> pd is complimentary to g 3 He -> ppn with respect to studying three-body mechanisms. ● CLAS data at photon energies GeV and proton CM angles 40º -140º. ● The invariant cross sections fall off extremely fast with s: power of s ~ -22. ● The differential cross sections exhibit large forward- backward asymmetry: one order of magnitude. ● The slope of the dfferential cross sections is independent of Eg. ● The cross sections are sensitive to three-body mechanism contributions.

● A comparison with J.M. Laget's model shows that the relative contribution of the three-body mechanisms is larger at MeV than at higher photon energies. This has been also observed in the three-body breakup of 3 He.

Electroproduction of  s in 3 He ● Modification of  s in nuclear medium? ● Electroproduction of  0   - p ● Electroproduction of  +   0 p ● Comparison with  +   0 p from free proton (CLAS ANALYSIS , +papers) Joe Donnelly Dave Ireland University of Glasgow

Partial Wave Coefficients p(e,e’ 0 p) 3 He(e,e’ - p)

Extracted Multipole Distributions 3 He(e,e’ - p)

Three-body forces studied in 3 He(e,e’pp) reactions Dan Watts (University of Edinburgh) Dan Protopopescu Dave Ireland (University of Glasgow)

Spectator or Active Neutron? p m < 0.2 GeV/c (spectator) p m > 0.2 GeV/c (active)

Variation with  0 0 <  < <  < <  < <  < <  < <  < All   = 50, 150, 250, 350, 450 MeV Experimental Data

CLAS data and neutrinos – summary S. Manly, Univ. of Rochester Neutrinos have mass and oscillate; compelling us to perform high statistics experiments in the one-few GeV range with reduced systematic errors. 1)High statistics, fully active, highly segmented neutrino expt. (MINER A) approved at FNAL. 2)Should produce A scattering. 3)data complementary to JLab eA data. See MINER A proposal – hep-ex/ See MINER A proposal – hep-ex/ )New set of long baseline, expensive, neutrino expts to measure last angle of neutrino mass mixing matrix and possibly look for CP violation in the neutrino sector (MINOS, T2K, NO A) are being designed/built (MINOS already taking data. These experiments can benefit greatly from MC constraints from eA data.

JUPITER - Jlab Unified Program to Investigate nuclear Targets and Electroproduction of Resonances Study eA processes in the one-few GeV region that are complementary to and useful for understanding neutrino scattering in the same energy range. With the push in neutrinos, complementary expts (to eA) can be done that will help us understand the nucleon, resonance production, nuclear effects, etc. Also use this information to reduce systematic errors in the neutrino experiments, thus contributing to the fundamental exploration of the neutrino sector. JLab Hall C – E and E – Separated vector structure functions for different nuclear targets Neutrinos - MINER A, also feed info to other expts. Phenomenology – development of structure function parametrizations through resonance region (using duality)

People R. Bradford at Rochester (0.5 CLAS, 0.5 MINER A) Summer student working on CLAS analysis (David Sher) J. Steinman working on Hall C E04-001

Summary of Progress Report for Analysis of d(e,e’p)n for the E5 Run Period Jerry Gilfoyle, Robert Burrell, and Kristen Greenholt For E=2.6 GeV, normal torus polarity, the fifth structure function asymmetry A’ LT is sensitive to the electron fiducial cuts. This appears to reflect the underlying Q 2 distribution in the data. Other tests show no problems with the event reconstruction near the coils. We have generated fiducial cuts for the proton for d(e,e’p)n using a mixed sample of protons and positive pions. The proton fiducial cuts have little effect on A’ LT.

Study of Short Range Correlations in A(e,e’) Reaction at 1 <x B <3 K. Egiyan, N. Dashyan, M. Sargsian, M. Strikman, L. Weinstein

● Will use published CLAS and Brookhaven data to study isotopic composition of 2-nucleon SRC in 12C. ● Using the data from C(p,2p+n) measurements of EVA experiment at BNL for isotopic estimates. ● Collaborating with authors E.Piasetzky and J.Watson of the BNL experiment. ● Preparing a paper for Science.

d(e,e'p)n exclusive reaction analysis: extraction of cross section G.Asryan, K.Egiyan ● Fitted the missing mass spectra to extract the neutron yield and calculate the measured cross section. ● Consistent within ~15% with previous cross sections where neutron yields were determined from simple cuts on missing mass spectra.

Status of g7 experiment on search for medium modifications of vector mesons. Absorption of  and  mesons observed as target A increases. For 208 Pb, these VM almost disappear completely. Plan is to extract  N and  N cross sections from experimental normalized yields and realistic model of final state interactions. Exp data – NA50 collaboration, M. Gonin et al., NPA 610 (1996) 404c Theory – W. Cassing and E. L. Bratkovskaya, NPA 623 (1997) 570 Suppression of J/  Absorption of Vector Mesons in Nuclei –  N and  N Cross Sections Michael Wood, UMass