Measurement of nuclear transparency from A(e,e'[pi]⁺) reactions

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.In title on t.p., "[pi]" appears as the lower-case Greek letter.Includes bibliographical references (p. 161-165).The color transparency phenomenon refers to the suppression of final-state interactions of a hadron propagating through the nuclear medium at large momentum transfer when the hadron is produced with small transverse size. The pion electroproduction cross section from 1H, 2H,12C, 63Cu and 197Au targets from Q2 = 1.1 to 4.8 (GeV/c)2 was measured in Jefferson Laboratory Experiment E01-107. The nuclear transparency was formed by the ratio of ([sigma]A/[sigma]H) from the data and ([sigma]A/[sigma]H) from a model of electroproduction from nuclei that does not include [pi]-N final state interactions. A signature of color transparency is the enhancement of the nuclear transparency at large Q2 compared with predictions based on Glauber multiple scattering theory. This experiment represents the first nuclear transparency data from (e,e'[pi]+) reactions.by Benjamin Michael Patrick Clasie.Ph.D

Scaling of the F-2 [F subscript 2] Structure Function in Nuclei and Quark Distributions at x > 1

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x>1, which is sensitive to short-range contributions to the nuclear wave function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the “superfast” quarks probed at x>1. The falloff at x>1 is noticeably stronger in 2H ]superscript 2 H] and 3He [superscript 3 He], but nearly identical for all heavier nuclei.United States. Dept. of Energy (Contract No. DE-FG02-96ER40950)United States. Dept. of Energy (Contract no. DE-AC05-06OR23177)United States. Dept. of Energy (Contract no. DE-AC02-06CH11357)National Science Foundation (U.S.) (Grant No. NSF-0244899)National Research Foundation (South Africa

Search for sub-threshold photoproduction of J/ψ [J/psi] mesons

A search was made for sub-threshold J/ψ [J / psi] production from a carbon target by using a mixed real and quasireal Bremsstrahlung photon beam with an endpoint energy of 5.76 GeV. No events were observed, which is consistent with predictions under the assumption of quasifree production. The results place limits on exotic mechanisms that strongly enhance quasifree production.United States. Dept. of Energy (Contract No. DEAC05-84ER40150)United States. Dept. of EnergyNational Science Foundation (U.S.)National Research Foundation (South Africa

New Measurements of the European Muon Collaboration Effect in Very Light Nuclei

New Jefferson Lab data are presented on the nuclear dependence of the inclusive cross section from [superscript 2]H, [superscript 3]He, [superscript 4]He, [superscript 9]Be and [superscript 12]C for 0.3<x<0.9, Q[superscript 2]≈3–6  GeV[superscript 2]. These data represent the first measurement of the EMC effect for 3He at large x and a significant improvement for 4He. The data do not support previous A-dependent or density-dependent fits to the EMC effect and suggest that the nuclear dependence of the quark distributions may depend on the local nuclear environment.U.S. Department of Energy (Contract No. DE-AC02-06CH11357, Contract No. DE-AC05-06OR23177)National Science Foundatio