11,208 research outputs found
Disentangling the EMC Effect
The deep inelastic scattering cross section for scattering from bound
nucleons differs from that of free nucleons.This phenomena, first discovered 30
years ago, is known as the EMC effect and is still not fully understood. Recent
analysis of world data showed that the strength of the EMC effect is linearly
correlated with the relative amount of Two-Nucleon Short Range Correlated pairs
(2N-SRC) in nuclei. The latter are pairs of nucleons whose wave functions
overlap, giving them large relative momentum and low center of mass momentum,
where high and low is relative to the Fermi momentum of the nucleus. The
observed correlation indicates that the EMC effect, like 2N-SRC pairs, is
related to high momentum nucleons in the nucleus. This paper reviews previous
studies of the EMC-SRC correlation and studies its robustness. It also presents
a planned experiment aimed at studying the origin of this EMC-SRC correlation.Comment: 8 pages, 3 figures. Proceedings of plenary talk at CIPANP 201
Hammer events, neutrino energies, and nucleon-nucleon correlations
Neutrino oscillation measurements depend on a difference between the rate of
neutrino-nucleus interactions at different neutrino energies or different
distances from the source. Knowledge of the neutrino energy spectrum and
neutrino-detector interactions are crucial for these experiments. Short range
nucleon-nucleon correlations in nuclei (SRC) affect properties of nuclei. The
ArgoNeut liquid Argon Time Projection Chamber (lArTPC) observed neutrino-argon
scattering events with two protons back-to-back in the final state ("hammer"
events) which they associated with SRC pairs. The MicroBoone lArTPC will
measure far more of these events.
We simulate hammer events using two simple models. We use the well-known
electron-nucleon cross section to calculate e-argon interactions where the e-
scatters from a proton, ejecting a pi+, and the pi+ is then absorbed on a
moving deuteron-like pair. We also use a model where the electron excites
a nucleon to a Delta, which then deexcites by interacting with a second
nucleon.
The pion production model results in two protons very similar to those of the
hammer events. These distributions are insensitive to the momentum of the
pair that absorbed the . The incident neutrino energy can be reconstructed
from just the outgoing lepton. The Delta process results in two protons that
are less similar to the observed events.
ArgoNeut hammer events can be described by a simple pion production and
reabsorption model. These hammer events in MicroBooNE can be used to determine
the incident neutrino energy but not to learn about SRC. We suggest that this
reaction channel could be used for neutrino oscillation experiments to
complement other channels with higher statistics but different systematic
uncertainties.Comment: Text improved in response to PRC referee comment
Equilibrium Configuration of Black Holes and the Inverse Scattering Method
The inverse scattering method is applied to the investigation of the
equilibrium configuration of black holes. A study of the boundary problem
corresponding to this configuration shows that any axially symmetric,
stationary solution of the Einstein equations with disconnected event horizon
must belong to the class of Belinskii-Zakharov solutions. Relationships between
the angular momenta and angular velocities of black holes are derived.Comment: LaTeX, 14 pages, no figure
Extracting the Mass Dependence and Quantum Numbers of Short-Range Correlated Pairs from A(e,e'p) and A(e,e'pp) Scattering
The nuclear mass dependence of the number of short-range correlated (SRC)
proton-proton (pp) and proton-neutron (pn) pairs in nuclei is a sensitive probe
of the dynamics of short-range pairs in the ground state of atomic nuclei. This
work presents an analysis of electroinduced single-proton and two-proton
knockout measurements off 12C, 27Al, 56Fe, and 208Pb in kinematics dominated by
scattering off SRC pairs. The nuclear mass dependence of the observed
A(e,e'pp)/12C(e,e'pp) cross-section ratios and the extracted number of pp- and
pn-SRC pairs are much softer than the mass dependence of the total number of
possible pairs. This is in agreement with a physical picture of SRC affecting
predominantly nucleon-nucleon pairs in a nodeless relative-S state of the
mean-field basis.Comment: 6 pages, 3 figure
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