386 research outputs found
Longitudinal-Transverse Separations of Structure Functions at Low for Hydrogen and Deuterium
We report on a study of the longitudinal to transverse cross section ratio,
, at low values of and , as determined from
inclusive inelastic electron-hydrogen and electron-deuterium scattering data
from Jefferson Lab Hall C spanning the four-momentum transfer range 0.06 GeV. Even at the lowest values of , remains
nearly constant and does not disappear with decreasing , as expected. We
find a nearly identical behaviour for hydrogen and deuterium.Comment: 4 pages, 2 gigure
Cross Section Measurement of Charged Pion Photoproduction from Hydrogen and Deuterium
We have measured the differential cross section for the gamma n --> pi- p and
gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon
energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon
energies greater than 3.3 GeV exhibit a global scaling behavior for both pi-
and pi+ photoproduction, consistent with the constituent counting rule and the
existing pi+ photoproduction data. Possible oscillations around the scaling
value are suggested by these new data The data show enhancement in the scaled
cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio
of exclusive pi- to pi+ photoproduction at high energy is consistent with the
prediction based on one-hard-gluon-exchange diagrams
JLab Measurement of the He Charge Form Factor at Large Momentum Transfers
The charge form factor of ^4He has been extracted in the range 29 fm
fm from elastic electron scattering, detecting He
nuclei and electrons in coincidence with the High Resolution Spectrometers of
the Hall A Facility of Jefferson Lab. The results are in qualitative agreement
with realistic meson-nucleon theoretical calculations. The data have uncovered
a second diffraction minimum, which was predicted in the range of this
experiment, and rule out conclusively long-standing predictions of dimensional
scaling of high-energy amplitudes using quark counting.Comment: 4 pages, 2 figure
Measurement of the 12C(e,e'p)11B Two-Body Breakup Reaction at High Missing Momentum Values
The five-fold differential cross section for the 12C(e,e'p)11B reaction was
determined over a missing momentum range of 200-400 MeV/c, in a kinematics
regime with Bjorken x > 1 and Q2 = 2.0 (GeV/c)2. A comparison of the results
and theoretical models and previous lower missing momentum data is shown. The
theoretical calculations agree well with the data up to a missing momentum
value of 325 MeV/c and then diverge for larger missing momenta. The extracted
distorted momentum distribution is shown to be consistent with previous data
and extends the range of available data up to 400 MeV/c.Comment: 12 pages, 1 table and 3 figures for submission to Journal Physics
Determination of the pion charge form factor for Q^2=0.60-1.60 GeV^2
The data analysis for the reaction H(e,e' pi^+)n, which was used to determine
values for the charged pion form factor Fpi for values of Q^2=0.6-1.6 GeV^2,
has been repeated with careful inspection of all steps and special attention to
systematic uncertainties. Also the method used to extract Fpi from the measured
longitudinal cross section was critically reconsidered. Final values for the
separated longitudinal and transverse cross sections and the extracted values
of Fpi are presented.Comment: 11 pages, 6 figure
Scaling of the F_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 , 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
`super-fast' quarks probed at x>1. The falloff at x>1 is noticeably stronger in
^2H and ^3He, but nearly identical for all heavier nuclei.Comment: 5 pages, 4 figures, to be submitted to physical revie
Measurements of electron-proton elastic cross sections for
We report on precision measurements of the elastic cross section for
electron-proton scattering performed in Hall C at Jefferson Lab. The
measurements were made at 28 unique kinematic settings covering a range in
momentum transfer of 0.4 5.5 . These measurements
represent a significant contribution to the world's cross section data set in
the range where a large discrepancy currently exists between the ratio of
electric to magnetic proton form factors extracted from previous cross section
measurements and that recently measured via polarization transfer in Hall A at
Jefferson Lab.Comment: 17 pages, 18 figures; text added, some figures replace
Inclusive Electron-Nucleus Scattering at Large Momentum Transfer
Inclusive electron scattering is measured with 4.045 GeV incident beam energy
from C, Fe and Au targets. The measured energy transfers and angles correspond
to a kinematic range for Bjorken and momentum transfers from . When analyzed in terms of the y-scaling function the data show
for the first time an approach to scaling for values of the initial nucleon
momenta significantly greater than the nuclear matter Fermi-momentum (i.e. GeV/c).Comment: 5 pages TEX, 5 Postscript figures also available at
http://www.krl.caltech.edu/preprints/OAP.htm
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