192 research outputs found
Measurements of the neutron electric to magnetic form factor ratio G_(En)/G_(Mn) via the ^2H(e, e'n)^1H reaction to Q^2 = 1.45 (GeV/c)^2
We report values for the neutron electric tomagnetic form factor ratio,G_(En)/G_(Mn), deduced frommeasurements
of the neutron’s recoil polarization in the quasielastic ^2H(e, e'n)^1H reaction, at three Q^2 values of 0.45, 1.13,
and 1.45 (GeV/c)^2. The data at Q^2 = 1.13 and 1.45 (GeV/c)^2 are the first direct experimental measurements of
G_(En) employing polarization degrees of freedom in the Q^2 > 1 (GeV/c)^2 region and stand as the most precise
determinations of G_(En) for all values of Q^2
The Super Bigbite Project: a Study of Nucleon Form Factors
A proposed set of instrumentation, collectively referred to as the Super
Bigbite project, is presented. Used in three different configurations it will
allow measurements of three nucleon electromagnetic form factors GEn, GEp, and
GMn with unprecedented precision to Q2-values up to three times higher than
existing data
Precision Measurement Of The Neutron's Beta Asymmetry Using Ultra-Cold Neutrons
A measurement of A_β, the correlation between the electron momentum and neutron (n) spin (the beta asymmetry) in n beta-decay, together with the n lifetime, provides a method for extracting fundamental parameters for the charged-current weak interaction of the nucleon. In particular when combined with decay measurements, one can extract the V_(ud) element of the CKM matrix, a critical element in CKM unitarity tests. By using a new SD_2 super-thermal source at LANSCE, large fluxes of UCN (ultra-cold neutrons) are expected for the UCNA project. These UCN will be 100% polarized using a 7 T magnetic field, and directed into the β spectrometer. This approach, together with an expected large reduction in backgrounds, will result in an order of magnitude reduction in the critical systematic corrections associated with current n β-asymmetry measurements. This paper will give an overview of the UCNA Aβ measurement as well as an update on the status of the experiment
Motional Spin Relaxation in Large Electric Fields
We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and
He atoms in uniform and static magnetic and electric fields and calculate
the spin relaxation effects from motional magnetic fields. Particle
motion in an electric field creates a motional magnetic field,
which when combined with collisions, produces variations of the total magnetic
field and results in spin relaxation of neutron and He samples. The spin
relaxation times (longitudinal) and (transverse) of
spin-polarized UCN and He atoms are important considerations in a new
search for the neutron Electric Dipole Moment at the SNS \emph{nEDM}
experiment. We use a Monte Carlo approach to simulate the relaxation of spins
due to the motional field for UCN and for He atoms at
temperatures below . We find the relaxation times for the
neutron due to the effect to be long compared to the neutron
lifetime, while the He relaxation times may be important for the
\emph{nEDM} experiment.Comment: 5 Pages, 4 Figures, 1 Table. Submitted to Phys. Rev.
Impact of motion along the field direction on geometric-phase-induced false electric dipole moment signals
Geometric-phase-induced false electric dipole moment (EDM) signals, resulting
from interference between magnetic field gradients and particle motion in
electric fields, have been studied extensively in the literature, especially
for neutron EDM experiments utilizing stored ultracold neutrons and
co-magnetometer atoms. Previous studies have considered particle motion in the
transverse plane perpendicular to the direction of the applied electric and
magnetic fields. We show, via Monte Carlo studies, that motion along the field
direction can impact the magnitude of this false EDM signal if the wall
surfaces are rough such that the wall collisions can be modeled as diffuse,
with the results dependent on the size of the storage cell's dimension along
the field direction.Comment: 7 pages, 3 figures, NIM A, in pres
Resultados finales para el parámetro de asimetrĂa ? de neutrones A 0 del experimento UCNA
The UCNA experiment was designed to measure the neutron ?-asymmetry parameter A0 using polarized ultracold neutrons (UCN). UCN produced via downscattering in solid deuterium were polarized via transport through a 7 T magnetic field, and then directed to a 1 T solenoidal electron spectrometer, where the decay electrons were detected in electron detector packages located on the two ends of the spectrometer. A value for A0 was then extracted from the asymmetry in the numbers of counts in the two detector packages. We summarize all of the results from the UCNA experiment, obtained during run periods in 2007, 2008–2009, 2010, and 2011–2013, which ultimately culminated in a 0.67% precision result for A0
- …