428 research outputs found
Conference summary
A perspective on the PAVI11 conference is given
Twist-four Corrections to Parity-Violating Electron-Deuteron Scattering
Parity violating electron-deuteron scattering can potentially provide a clean
access to electroweak couplings that are sensitive to physics beyond the
Standard Model. However hadronic effects can contaminate their extraction from
high-precision measurements. Power-suppressed contributions are one of the main
sources of uncertainties along with charge-symmetry violating effects in
leading-twist parton densities. In this work we calculate the twist-four
correlation functions contributing to the left-right polarization asymmetry
making use of nucleon multiparton light-cone wave functions.Comment: 12 pages, 3 figure
Study of the neutron skin thickness of Pb in mean field models
We study whether the neutron skin thickness of Pb
originates from the bulk or from the surface of the neutron and proton density
distributions in mean field models. We find that the size of the bulk
contribution to of Pb strongly depends on the slope
of the nuclear symmetry energy, while the surface contribution does not. We
note that most mean field models predict a neutron density for Pb
between the halo and skin type limits. We investigate the dependence of parity-
violating electron scattering at the kinematics of the PREX experiment on the
shape of the nucleon densities predicted by the mean field models for
Pb. We find an approximate formula for the parity-violating asymmetry
in terms of the central radius and the surface diffuseness of the nucleon
densities of Pb in these models.Comment: 5 pages, 2 figures, proceedings MBC 2011 - Many body correlations
from dilute to dense nuclear systems - IHP PARI
Do we understand the incompressibility of neutron-rich matter?
The ``breathing mode'' of neutron-rich nuclei is our window into the
incompressibility of neutron-rich matter. After much confusion on the
interpretation of the experimental data, consistency was finally reached
between different models that predicted both the distribution of isoscalar
monopole strength in finite nuclei and the compression modulus of infinite
matter. However, a very recent experiment on the Tin isotopes at the Research
Center for Nuclear Physics(RCNP) in Japan has again muddled the waters.
Self-consistent models that were successful in reproducing the energy of the
giant monopole resonance (GMR) in nuclei with various nucleon asymmetries (such
as 90Zr, 144Sm, and 208Pb) overestimate the GMR energies in the Tin isotopes.
As important, the discrepancy between theory and experiment appears to grow
with neutron excess. This is particularly problematic as models artificially
tuned to reproduce the rapid softening of the GMR in the Tin isotopes become
inconsistent with the behavior of dilute neutron matter. Thus, we regard the
question of ``why is Tin so soft?'' as an important open problem in nuclear
structure.Comment: 12 pages, 3 figures, and 1 table. Submitted to the "Focus issue on
Open Problems in Nuclear Structure", Journal of Physics
A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab
A high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave
green laser (532~nm) has been built and installed in Hall A of Jefferson Lab
for high precision Compton polarimetry. The infrared (1064~nm) beam from a
ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator
laser is frequency doubled in a single-pass periodically poled MgO:LiNbO
crystal. The maximum achieved green power at 5 W IR pump power is 1.74 W with a
total conversion efficiency of 34.8\%. The green beam is injected into the
optical resonant cavity and enhanced up to 3.7~kW with a corresponding
enhancement of 3800. The polarization transfer function has been measured in
order to determine the intra-cavity circular laser polarization within a
measurement uncertainty of 0.7\%. The PREx experiment at Jefferson Lab used
this system for the first time and achieved 1.0\% precision in polarization
measurements of an electron beam with energy and current of 1.0~GeV and
50~A.Comment: 20 pages, 22 figures, revised version of arXiv:1601.00251v1,
submitted to NIM
Unpolarized structure functions at Jefferson Lab
Over the past decade measurements of unpolarized structure functions at
Jefferson Lab with unprecedented precision have significantly advanced our
knowledge of nucleon structure. These have for the first time allowed
quantitative tests of the phenomenon of quark-hadron duality, and provided a
deeper understanding of the transition from hadron to quark degrees of freedom
in inclusive scattering. Dedicated Rosenbluth-separation experiments have
yielded high-precision transverse and longitudinal structure functions in
regions previously unexplored, and new techniques have enabled the first
glimpses of the structure of the free neutron, without contamination from
nuclear effects.Comment: 21 pages, 9 figures; typo in Eq. (3) corrected, references added; to
appear in J. Phys. Conf. Proc. "New Insights into the Structure of Matter:
The First Decade of Science at Jefferson Lab", eds. D. Higinbotham, W.
Melnitchouk, A. Thoma
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