164 research outputs found
Hard Photodisintegration of a Proton Pair
We present a study of high energy photodisintegration of proton-pairs through the Îł + 3He â p + p + n channel. Photon energies, EÎł , from 0.8 to 4.7 GeV were used in kinematics corresponding to a proton pair with high relative momentum and a neutron nearly at rest. The sâ11 scaling of the cross section, as predicted by the constituent counting rule for two nucleon photodisintegration, was observed for the first time. The onset of the scaling is at a higher energy and the cross section is significantly lower than for deuteron (pn pair) photodisintegration. For EÎł below the scaling region, the scaled cross section was found to present a strong energy-dependent structure not observed in deuteron photodisintegration
Hard Photodisintegration of a Proton Pair
We present a study of high energy photodisintegration of proton-pairs through
the gamma + 3He -> p+p+n channel. Photon energies from 0.8 to 4.7 GeV were used
in kinematics corresponding to a proton pair with high relative momentum and a
neutron nearly at rest. The s-11 scaling of the cross section, as predicted by
the constituent counting rule for two nucleon photodisintegration, was observed
for the first time. The onset of the scaling is at a higher energy and the
cross section is significantly lower than for deuteron (pn pair)
photodisintegration. For photon energies below the scaling region, the scaled
cross section was found to present a strong energy-dependent structure not
observed in deuteron photodisintegration.Comment: 7 pages, 3 figures, for submission to Phys. Lett.
Electroexcitation of the at low momentum transfer
We report on new p measurements at the
resonance at the low momentum transfer region. The mesonic
cloud dynamics is predicted to be dominant and rapidly changing in this
kinematic region offering a test bed for chiral effective field theory
calculations. The new data explore the low dependence of the resonant
quadrupole amplitudes while extending the measurements of the Coulomb
quadrupole amplitude to the lowest momentum transfer ever reached. The results
disagree with predictions of constituent quark models and are in reasonable
agreement with dynamical calculations that include pion cloud effects, chiral
effective field theory and lattice calculations. The reported measurements
suggest that improvement is required to the theoretical calculations and
provide valuable input that will allow their refinements
Single Spin Asymmetries of Inclusive Hadrons Produced in Electron Scattering from a Transversely Polarized He Target
We report the first measurement of target single-spin asymmetries (A) in
the inclusive hadron production reaction,
+, using a transversely polarized
He target. The experiment was conducted at Jefferson Lab in Hall A using a
5.9-GeV electron beam. Three types of hadrons (,
and proton) were detected in the transverse hadron momentum range 0.54
0.74 GeV/c. The range of for pions was -0.29 -0.23 and for kaons
-0.25 -0.18. The observed asymmetry strongly depends on the type of
hadron. A positive asymmetry is observed for and . A
negative asymmetry is observed for . The magnitudes of the asymmetries
follow . The K and proton
asymmetries are consistent with zero within the experimental uncertainties. The
and asymmetries measured for the He target and
extracted for neutrons are opposite in sign with a small increase observed as a
function of .Comment: Updated version, submitted to Phys. Rev.
Measurement of pretzelosity asymmetry of charged pion production in Semi-Inclusive Deep Inelastic Scattering on a polarized He target
An experiment to measure single-spin asymmetries in semi-inclusive production
of charged pions in deep-inelastic scattering on a transversely polarized
He target was performed at Jefferson Lab in the kinematic region of
and . The pretzelosity asymmetries on
He, which can be expressed as the convolution of the
transverse momentum dependent distribution functions and the Collins
fragmentation functions in the leading order, were measured for the first time.
Using the effective polarization approximation, we extracted the corresponding
neutron asymmetries from the measured He asymmetries and cross-section
ratios between the proton and He. Our results show that for both
on He and on the neutron the pretzelosity asymmetries are
consistent with zero within experimental uncertainties.Comment: 6 pages, 3 figures; enlarged the legends in Fig.3; added 3 citation
Double Spin Asymmetries of Inclusive Hadron Electroproductions from a Transversely Polarized Target
We report the measurement of beam-target double-spin asymmetries
() in the inclusive production of identified hadrons,
+, using a longitudinally
polarized 5.9 GeV electron beam and a transversely polarized
target. Hadrons (, and proton) were detected at
16 with an average momentum =2.35 GeV/c and a transverse
momentum () coverage from 0.60 to 0.68 GeV/c. Asymmetries from the
target were observed to be non-zero for production
when the target was polarized transversely in the horizontal plane. The
and asymmetries have opposite signs, analogous to the
behavior of in semi-inclusive deep-inelastic scattering.Comment: Published in PRC (92.015207), nuclear experiment, high-energy
experimen
Single Spin Asymmetries in Charged Kaon Production from Semi-Inclusive Deep Inelastic Scattering on a Transversely Polarized Target
We report the first measurement of target single spin asymmetries of charged
kaons produced in semi-inclusive deep inelastic scattering of electrons off a
transversely polarized target. Both the Collins and Sivers
moments, which are related to the nucleon transversity and Sivers
distributions, respectively, are extracted over the kinematic range of
0.10.4 for and production. While the Collins and
Sivers moments for are consistent with zero within the experimental
uncertainties, both moments for favor negative values. The Sivers
moments are compared to the theoretical prediction from a phenomenological fit
to the world data. While the Sivers moments are consistent with the
prediction, the results differ from the prediction at the 2-sigma
level.Comment: 6 pages, 3 figure
Methods for Optical Calibration of the BigBite Hadron Spectrometer
The techniques for optical calibration of Jefferson Lab's large-acceptance
magnetic hadron spectrometer, BigBite, have been examined. The most consistent
and stable results were obtained by using a method based on singular value
decomposition. In spite of the complexity of the optics, the particles'
positions and momenta at the target have been precisely reconstructed from the
coordinates measured in the detectors by means of a single back-tracing matrix.
The technique is applicable to any similar magnetic spectrometer and any
particle type. For 0.55 GeV/c protons, we have established the vertex
resolution of 1.2 cm, angular resolutions of 7 mrad and 16 mrad (in-plane and
out-of-plane, respectively), and a relative momentum resolution of 1.6%.Comment: 26 pages, 13 figure
Search for three-nucleon short-range correlations in light nuclei
We present new data probing short-range correlations (SRCs) in nuclei through the measurement of electron scattering off high-momentum nucleons in nuclei. The inclusive ^{4}He/^{3}He cross section ratio is observed to be both x and Q^{2} independent for 1.52, our data support the hypothesis that a previous claim of three-nucleon correlation dominance was an artifact caused by the limited resolution of the measurement. While 3N-SRCs appear to have an important contribution, our data show that isolating 3N-SRCs is significantly more complicated than for 2N-SRCs.United States. Department of Energy (Contract DE-AC05-06OR23177)United States. Department of Energy (Contract DE-AC02-06CH11357)United States. Department of Energy (Contract DE-FG02-96ER40950
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