This paper presents, for the first time, measurements of neutron transparency ratios for nuclei relative to C measured using the (e,e′n) reaction, spanning measured neutron momenta of 1.4 to 2.4 ...GeV/c. The transparency ratios were extracted in two kinematical regions, corresponding to knockout of mean-field nucleons and to the breakup of Short-Range Correlated nucleon pairs. The extracted neutron transparency ratios are consistent with each other for the two measured kinematical regions and agree with the proton transparencies extracted from new and previous (e,e′p) measurements, including those from neutron-rich nuclei such as lead. The data also agree with and confirm the Glauber approximation that is commonly used to interpret experimental data. The nuclear-mass-dependence of the extracted transparencies scales as Aα with α=−0.289±0.007, which is consistent with nuclear-surface dominance of the reactions.
We review the recent measurements of the rare pion decays:
π
+
→
π
0
e
+
ν
(beta,
π
e
3
, or
π
β
decay), radiative decay
π
+
→
e
+
ν
γ
(
π
e
2
γ
or RPD), and
π
+
→
e
+
ν
(
π
e
2
), as well as the ...radiative muon decay,
μ
→
e
ν
ν
¯
γ
, their theoretical implications, and prospects for further improvement.
We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the ...Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=-3.0±1.4(stat)±0.2(syst)×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=2.6±1.2(stat)±0.2(syst)×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=-7.4±3.5(stat)±0.5(syst)×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.
Full text
Available for:
CMK, CTK, FMFMET, NUK, UL
The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Accelerator Facility at ...Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5<Q2<6.5GeV2 and Bjorken scaling 0.3<x<0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target whose magnetic field direction could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A1, A2, g1, g2 and moment d2 of the proton. This document summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.
The Nab experiment will measure the ratio of the weak axial-vector and vector coupling constants
λ
=
g
A
/
g
V
with precision
δ
λ
/
λ
∼ 3 × 10
− 4
and search for a Fierz term
b
F
at a level Δ
b
F
< ...10
− 3
. The Nab detection system uses thick, large area, segmented silicon detectors to very precisely determine the decay proton’s time of flight and the decay electron’s energy in coincidence and reconstruct the correlation between the antineutrino and electron momenta. Excellent understanding of systematic effects affecting timing and energy reconstruction using this detection system are required. To explore these effects, a series of ex situ studies have been undertaken, including a search for a Fierz term at a less sensitive level of Δ
b
F
< 10
− 2
in the beta decay of
45
Ca using the UCNA spectrometer.
We have measured the spin structure functions g2p and g2d and the virtual photon asymmetries A2p and A2d over the kinematic range 0.02⩽x⩽0.8 and 0.7⩽Q2⩽20GeV2 by scattering 29.1 and 32.3 GeV ...longitudinally polarized electrons from transversely polarized NH3 and 6LiD targets. Our measured g2 approximately follows the twist-2 Wandzura–Wilczek calculation. The twist-3 reduced matrix elements d2p and d2n are less than two standard deviations from zero. The data are inconsistent with the Burkhardt–Cottingham sum rule if there is no pathological behavior as x→0. The Efremov–Leader–Teryaev integral is consistent with zero within our measured kinematic range. The absolute value of A2 is significantly smaller than the A2<R(1+A1)/2 limit.
We describe a detection system designed for precise measurements of angular correlations in neutron β decay. The system is based on thick, large area, highly segmented silicon detectors developed in ...collaboration with Micron Semiconductor, Ltd. The prototype system meets specifications for β electron detection with energy thresholds below 10keV, energy resolution of ∼3keV FWHM, and rise time of ∼50ns with 19 of the 127 detector pixels instrumented. Using ultracold neutrons at the Los Alamos Neutron Science Center, we have demonstrated the coincident detection of β particles and recoil protons from neutron β decay. The fully instrumented detection system will be implemented in the UCNB and Nab experiments to determine the neutron β decay parameters B, a, and b.
The calorimeter system of the new muon g-2 experiment at Fermilab Alonzi, L.P.; Anastasi, A.; Bjorkquist, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Volume:
824, Issue:
C
Journal Article
Peer reviewed
Open access
The electromagnetic calorimeter for the new muon (g−2) experiment at Fermilab will consist of arrays of PbF2 Čerenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. We ...report here the requirements for this system, the achieved solution and the results obtained from a test beam using 2.0–4.5GeV electrons with a 28-element prototype array.
PDF
