685 research outputs found

### Comment on "Constraints on proton structure from precision atomic physics measurements"

We strongly disagree with the procedure used in a recent paper to extract the
Zemach moment for hydrogen.Comment: 1 page, 2 figures, revtex - submitted to Physical Review Letter

### RDWIA analysis of 12C(e,e'p) for Q^2 < 2 (GeV/c)^2

We analyze data for 12C(e,e'p) with Q^2 < 2 (GeV/c)^2 using the relativistic
distorted-wave impulse approximation (RDWIA) based upon Dirac-Hartree wave
functions. The 1p normalization extracted from data for Q^2 > 0.6 (GeV/c)^2 is
approximately 0.87, independent of Q^2, which is consistent with the predicted
depletion by short-range correlations. The total 1p and 1s strength for E_m <
80 MeV approaches 100% of IPSM, consistent with a continuum contribution for 30
< E_m < 80 MeV of about 12% of IPSM. Similarly, a scale factor of 1.12 brings
RDWIA calculations into good agreement with 12C(e,e'p) data for transparency.
We also analyzed low Q^2 data from which a recent NDWIA analysis suggested that
spectroscopic factors might depend strongly upon the resolution of the probe.
We find that momentum distributions for their empirical Woods-Saxon wave
functions fit to low Q^2 data for parallel kinematics are too narrow to
reproduce data for quasiperpendicular kinematics, especially for larger Q^2,
and are partly responsible for reducing fitted normalization factors.Comment: 19 pages, 14 figures, to be submitted to PR

### Coulomb Sum Rule for \u3csup\u3e4\u3c/sup\u3eHE

We determine the Coulomb sum for 4He using the world data on 4He(e,eâ€²) and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment when using free-nucleon form factors. The apparent reduction of the in-medium GEp implied by IA-interpretation of the L/T-ratios measured in 4He(e,eâ€²p) and 4He(eâ†’,eâ€²pâ†’) is not confirmed

### On the dependence of the wave function of a bound nucleon on its momentum and the EMC effect

It is widely discussed in the literature that the wave function of the
nucleon bound in a nucleus is modified due to the interaction with the
surrounding medium. We argue that the modification should strongly depend on
the momentum of the nucleon. We study such an effect in the case of the
point-like configuration component of the wave function of a nucleon bound in a
nucleus A, considering the case of arbitrary final state of the spectator A-1
system. We show that for non relativistic values of the nucleon momentum, the
momentum dependence of the nucleon deformation appears to follow from rather
general considerations and discuss the implications of our theoretical
observation for two different phenomena: i) the search for medium induced
modifications of the nucleon radius of a bound nucleon through the measurement
of the electromagnetic nucleon form factors via the A(e,e'p)X process, and ii)
the A-dependence of the EMC effect; in this latter case we also present a new
method of estimating the fraction of the nucleus light-cone momentum carried by
the photons and find that in a heavy nuclei protons loose about 2% of their
momentum.Comment: 38 pages, 1 figure; changed references and text in Section I
(Introduction

### Improved radiative corrections for (e, e'p) experiments: Beyond the peaking approximation and implications of the soft-photon approximation

Abstract.: Analyzing (e, e'p) experimental data involves corrections for radiative effects which change the interaction kinematics and which have to be carefully considered in order to obtain the desired accuracy. Missing momentum and energy due to bremsstrahlung have so far often been incorporated into the simulations and the experimental analyses using the peaking approximation. It assumes that all bremsstrahlung is emitted in the direction of the radiating particle. In this article we introduce a full angular Monte Carlo simulation method which overcomes this approximation. As a test, the angular distribution of the bremsstrahlung photons is reconstructed from H(e, e'p) data. Its width is found to be underestimated by the peaking approximation and described much better by the approach developed in this work. The impact of the soft-photon approximation on the photon angular distribution is found to be minor as compared to the impact of the peaking approximatio

### Effect of kinematics on final state interactions in (e,e'p) reactions

Recent data from experiment E97-006 at TJNAF using the 12C(e,e'p) reaction at
very large missing energies and momenta are compared to a calculation of
two-step rescattering.
A comparison between parallel and perpendicular kinematics suggests that the
effects of final state interactions can be strongly reduced in the former case.Comment: 10 pages, 3 figures, submitted to LP

### Using Electron Scattering Superscaling to predict Charge-changing Neutrino Cross Sections in Nuclei

Superscaling analyses of few-GeV inclusive electron scattering from nuclei
are extended to include not only quasielastic processes, but now also into the
region where $\Delta$-excitation dominates. It is shown that, with reasonable
assumptions about the basic nuclear scaling function extracted from data and
information from other studies of the relative roles played by correlation and
MEC effects, the residual strength in the resonance region can be accounted for
through an extended scaling analysis. One observes scaling upon assuming that
the elementary cross section by which one divides the residual to obtain a new
scaling function is dominated by the $N\to\Delta$ transition and employing a
new scaling variable which is suited to the resonance region. This yields a
good representation of the electromagnetic response in both the quasielastic
and $\Delta$ regions. The scaling approach is then inverted and predictions are
made for charge-changing neutrino reactions at energies of a few GeV, with
focus placed on nuclei which are relevant for neutrino oscillation
measurements. For this a relativistic treatment of the required weak
interaction vector and axial-vector currents for both quasielastic and
$\Delta$-excitation processes is presented.Comment: 42 pages, 9 figures, accepted for publication in Physical Review

### Many-body theory interpretation of deep inelastic scattering

We analyze data on deep inelastic scattering of electrons from the proton
using ideas from standard many-body theory involving {\em bound} constituents
subject to {\em interactions}. This leads us to expect, at large three-momentum
transfer ${\bf{q}}$, scaling in terms of the variable $\tilde{y}=\nu-{\bf
|q|}$. The response at constant ${\bf |q|}$ scales well in this variable.
Interaction effects are manifestly displayed in this approach. They are
illustrated in two examples.Comment: 10 pages, 4 figure

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