8 research outputs found
Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence
We measured the ratio of the transverse to longitudinal
components of polarization transferred from electrons to bound protons in
by the process at the
Mainz Microtron (MAMI). We observed consistent deviations from unity of this
ratio normalized to the free-proton ratio,
, for both -
and -shell knocked out protons, even though they are embedded in averaged
local densities that differ by about a factor of two. The dependence of the
double ratio on proton virtuality is similar to the one for knocked out protons
from and , suggesting a universal behavior.
It further implies no dependence on average local nuclear density
Laser Calibration System for Time of Flight Scintillator Arrays
A laser calibration system was developed for monitoring and calibrating time
of flight (TOF) scintillating detector arrays. The system includes setups for
both small- and large-scale scintillator arrays. Following test-bench
characterization, the laser system was recently commissioned in experimental
Hall B at the Thomas Jefferson National Accelerator Facility for use on the new
Backward Angle Neutron Detector (BAND) scintillator array. The system
successfully provided time walk corrections, absolute time calibration, and TOF
drift correction for the scintillators in BAND. This showcases the general
applicability of the system for use on high-precision TOF detectors.Comment: 11 pages, 11 figure
Comparison of recoil polarization in the process for protons extracted from and shell
We present first measurements of the double ratio of the polarization
transfer components for knock-out protons from and
shells in measured by the reaction in quasi-elastic kinematics. The data are
compared to theoretical predictions in relativistic distorted-wave impulse
approximation. Our results show that differences between - and -shell
protons, observed when compared at the same initial momentum (missing momentum)
largely disappear when the comparison is done at the same proton virtuality. We
observe no density-dependent medium modifications for protons from and
shells with the same virtuality in spite of the large differences in the
respective nuclear densities
The influence of Fermi motion on the comparison of the polarization transfer to a proton in elastic and quasi-elastic scattering
A comparison between polarization-transfer to a bound proton in quasi-free
kinematics by the A knockout reaction and that in elastic
scattering off a free proton can provide information on the characteristics of
the bound proton. In the past the reported measurements have been compared to
those of a free proton with zero initial momentum. We introduce, for the first
time, expressions for the polarization-transfer components when the proton is
initially in motion and compare them to the H data measured at the Mainz
Microtron (MAMI). We show the ratios of the transverse () and longitudinal
() components of the polarization transfer in , to those of elastic scattering off a "moving proton", assuming
the proton's initial (Fermi) momentum equals the negative missing momentum in
the measured reaction. We found that the correction due to the proton motion is
up to 20\% at high missing momentum.
However the effect on the double ratio
is largely canceled out, as
shown for both H and C data. This implies that the kinematics is not
the primary cause for the deviations between quasi-elastic and elastic
scattering reported previously
Polarization transfer to bound protons measured by quasielastic electron scattering on C 12
We report the measurements of the transverse (Px′) and longitudinal (Pz′) components of the polarization transfer to a bound proton in carbon via the quasifree C12(e - ,e′p - ) reaction, over a wide range of missing momenta. We determine these polarization transfers separately for protons knocked out from the s and p shells. The electron-beam polarization was measured to determine the individual components with systematic uncertainties which allow a detailed comparison with theoretical calculations
Comparison of recoil polarization in the C12(e→,e′p→) process for protons extracted from s and p shells
We present the first measurements of the double ratio of the polarization-transfer components (Px′/Pz′)p/(Px′/Pz′)s for knock-out protons from the s and p shells in C12 measured by the C12(e→,e′p→) reaction in quasi-elastic kinematics. The data are compared to theoretical predictions in the relativistic distorted-wave impulse approximation. Our results show that the differences between s- and p-shell protons, observed when compared at the same initial momentum (missing momentum), largely disappear when the comparison is done at the same proton virtuality. We observe no difference in medium modifications between protons from the s and p shells with the same virtuality in spite of the large differences in the respective nuclear densities
Measurements of the induced polarization in the quasi-elastic A(e,e′p→) process in non-coplanar kinematics
We report measurements of the induced polarization P→ of protons knocked out from 2H and 12C via the A(e,e′p→) reaction. We have studied the dependence of P→ on two kinematic variables: the missing momentum pmiss and the “off-coplanarity” angle ϕpq between the scattering and reaction planes. For the full 360° range in ϕpq, both the normal (Py) and, for the first time, the transverse (Px) components of the induced polarization were measured with respect to the coordinate system associated with the scattering plane. Px vanishes in coplanar kinematics, however in non-coplanar kinematics, it is on the same scale as Py. We find that the dependence on ϕpq is sine-like for Px and cosine-like for Py. For carbon, the magnitude of the induced polarization is especially large when protons are knocked out from the p3/2 shell at very small pmiss. For the deuteron, the induced polarization is near zero at small |pmiss|, and its magnitude increases with |pmiss|. For both nuclei such behavior is reproduced qualitatively by theoretical results, driven largely by the spin-orbit part of the final-state interactions. However, for both nuclei, sizeable discrepancies exist between experiment and theory