146 research outputs found
Longitudinal response function of 4He with a realistic force
The longitudinal response function of 4He is calculated with the Argonne V18
potential. The comparison with experiment suggests the need of a three-body
force. When adding the Urbana IX three-body potential in the calculation of the
lower longitudinal multipoles, the total strength is suppressed in the
quasi-elastic peak, towards the trend of the experimental data.Comment: 3 pages, 3 figures, proceedings of the 20th European Conference on
Few-Body Problems in Physics (EFB20
Direct Measurement of Nuclear Dependence of Charged Current Quasielastic-like Neutrino Interactions using MINERvA
Charged-current interactions on carbon, iron, and lead with a
final state hadronic system of one or more protons with zero mesons are used to
investigate the influence of the nuclear environment on quasielastic-like
interactions. The transfered four-momentum squared to the target nucleus,
, is reconstructed based on the kinematics of the leading proton, and
differential cross sections versus and the cross-section ratios of iron,
lead and carbon to scintillator are measured for the first time in a single
experiment. The measurements show a dependence on atomic number. While the
quasielastic-like scattering on carbon is compatible with predictions, the
trends exhibited by scattering on iron and lead favor a prediction with
intranuclear rescattering of hadrons accounted for by a conventional particle
cascade treatment. These measurements help discriminate between different
models of both initial state nucleons and final state interactions used in the
neutrino oscillation experiments
Measurement of Exclusive B Decays to Final States Containing a Charmed Baryon
Using data collected by the CLEO detector in the Upsilon(4S) region, we
report new measurements of the exclusive decays of B mesons into final states
of the type Lambda_c^+ p-bar n(pi), where n=0,1,2,3. We find signals in modes
with one, two and three pions and an upper limit for the two body decay
Lambda_c^+ pbar. We also make the first measurements of exclusive decays of B
mesons to Sigma_c p-bar n(pi), where n=0,1,2. We find signals in modes with one
and two pions and an upper limit for the two body decay Sigma_c p-bar.
Measurements of these modes shed light on the mechanisms involved in B decays
to baryons.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
Measurement of the Masses and Widths of the Sigma_c^++ and Sigma_c^0 Charmed Baryons
Using data recorded by the CLEO II and CLEO II.V detector configurations at
CESR, we report new measurements of the masses of the Sigma_c^{++} and
Sigma_c^0 charmed baryons, and the first measurements of their intrinsic
widths. We find M(Sigma_c^{++}) - M(Lambda_c^+) = 167.4 +- 0.1 +- 0.2 MeV,
Gamma(Sigma_c^{++}) = 2.3 +- 0.2 +- 0.3 MeV, and M(Sigma_c^0) - M(Lambda_c^+) =
167.2 +- 0.1 +- 0.2 MeV, Gamma(Sigma_c^0) = 2.5 +- 0.2 +- 0.3 MeV, where the
uncertainties are statistical and systematic, respectively.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PRD, Rapid
Communications. Reference [13] correcte
Photodisintegration of He into p+t
The two-body photodisintegration of He into a proton and a triton has
been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson
Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system
in the energy range from 0.35 to 1.55 GeV were incident on a liquid He
target. This is the first measurement of the photodisintegration of He
above 0.4 GeV. The differential cross sections for the He
reaction have been measured as a function of photon-beam energy and
proton-scattering angle, and are compared with the latest model calculations by
J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the
calculations that include three-body mechanisms, thus confirming their
importance. These results reinforce the conclusion of our previous study of the
three-body breakup of He that demonstrated the great importance of
three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22
postscrip figure
Measurement of the Polarized Structure Function for in the Resonance Region
The polarized longitudinal-transverse structure function
has been measured in the resonance region at and 0.65
GeV. Data for the reaction were taken at Jefferson Lab
with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally
polarized electrons at an energy of 1.515 GeV. For the first time a complete
angular distribution was measured, permitting the separation of different
non-resonant amplitudes using a partial wave analysis. Comparison with previous
beam asymmetry measurements at MAMI indicate a deviation from the predicted
dependence of using recent phenomenological
models.Comment: 5 pages, LaTex, 4 eps figures: to be published in PRC/Rapid
Communications. Version 2 has revised Q^2 analysi
Two-Nucleon Momentum Distributions Measured in 3He(e,e'pp)n
We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic
range. The kinetic energy distribution for `fast' nucleons (p > 250 MeV/c)
peaks where two nucleons each have 20% or less, and the third nucleon has most
of the transferred energy. These fast pp and pn pairs are back-to-back with
little momentum along the three-momentum transfer, indicating that they are
spectators. Experimental and theoretical evidence indicates that we have
measured distorted two-nucleon momentum distributions by striking the third
nucleon and detecting the spectator correlated pair.Comment: 6 pages, 5 figures, submitted to PR
Survey of A_LT' asymmetries in semi-exclusive electron scattering on He4 and C12
Single spin azimuthal asymmetries A_LT' were measured at Jefferson Lab using
2.2 and 4.4 GeV longitudinally polarized electrons incident on He4 and C12
targets in the CLAS detector. A_LT' is related to the imaginary part of the
longitudinal-transverse interference and in quasifree nucleon knockout it
provides an unambiguous signature for final state interactions (FSI).
Experimental values of A_LT' were found to be below 5%, typically |A_LT'| < 3%
for data with good statistical precision. Optical Model in Eikonal
Approximation (OMEA) and Relativistic Multiple-Scattering Glauber Approximation
(RMSGA) calculations are shown to be consistent with the measured asymmetries.Comment: 9 pages, 5 figure
Exclusive electroproduction on the proton at CLAS
The reaction has been measured, using the 5.754
GeV electron beam of Jefferson Lab and the CLAS detector. This represents the
largest ever set of data for this reaction in the valence region. Integrated
and differential cross sections are presented. The , and
dependences of the cross section are compared to theoretical calculations based
on -channel meson-exchange Regge theory on the one hand and on quark handbag
diagrams related to Generalized Parton Distributions (GPDs) on the other hand.
The Regge approach can describe at the 30% level most of the features
of the present data while the two GPD calculations that are presented in this
article which succesfully reproduce the high energy data strongly underestimate
the present data. The question is then raised whether this discrepancy
originates from an incomplete or inexact way of modelling the GPDs or the
associated hard scattering amplitude or whether the GPD formalism is simply
inapplicable in this region due to higher-twists contributions, incalculable at
present.Comment: 29 pages, 29 figure
Observation of Exclusive barB --> D(*) K*- Decays
We report the first observation of the exclusive decays \bar B\to
D^{(*)}K^{*-}, using 9.66 x 10^{6} B\bar{B} pairs collected at the \Upsilon(4S)
with the CLEO detector. We measure the following branching fractions: {\cal
B}(B^- -> D^0 K^{*-})=(6.1 +- 1.6 +-1.7)x10^{-4}, {\cal B}(\bar{B^0} ->
D^+K^{*-})=(3.7 +- 1.5 +- 1.0) x 10^{-4}, {\cal B}(\bar{B^0} ->
D^{*+}K^{*-})=(3.8 +- 1.3 +- 0.8) x 10^{-4} and {\cal B}(B^- --> D^{*0}
K^{*-})=(7.7 +- 2.2 +- 2.6) x 10^{-4}. The \bar B ->D^*K^{*-} branching ratios
are the averages of those corresponding to the 00 and 11 helicity states. The
errors shown are statistical and systematic, respectively.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, Published in
Phys.Rev.Lett.88:101803,200
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