E. Stephenson - Academia.edu (original) (raw)

Papers by E. Stephenson

During 1981, measurements have been completed Gaussians was chosen to match the deuteron of the t... more During 1981, measurements have been completed Gaussians was chosen to match the deuteron of the tensor analyzing powers Ayy and X2 = (2Axx wavelength, and their width was chosen to ruinimize + A ~ ~) / ~ T in the elastic scattering of 80 MeV oscillations in their sum. Only the strengths were deuterons from 58~i. All of the elastic scattering varied to improve agreement between the calculation measurements, including the cross section and and the data. The resulting calculation is a vector analyzing power Ay, are shown in Fig. 1. The new measurements of Ayy are large near 21°, compromise that favors good reproduction of the cross section and vector analyzing power (the solid showing an effect of interference that is also curve in Fig. 1). The cross section minima and prominent in Ay. The measurements of X2 were made large angle slope are well-reproduced, as is the on a special scattering table set at 54.7' to the patteru of the oscillations in Ay. The large Ayy horizontal plane (...

In November 1990, we measured the cross section, analyzing power Ay, induced polarization P, and ... more In November 1990, we measured the cross section, analyzing power Ay, induced polarization P, and polarization transfer coefficient DNNl for '' B(p,p') '' B inelastic scattering with a 200 MeV polarized proton beam. Scattered particles were momentum analyzed with the K600 magnetic spectrometer and polarizations measured with the focal plane polarimeter. Additional running in February 1991 completed the data acquisition for cross section and analyzing power at small angles. Cross section and analyzing power angular distributions for both elastic and inelastic scattering were measured between BLAB = 7.5" and 80" in 2.5" steps. Longer runs were made at five angles (20°, 30°, 40°, 50' and 60") to accumulate the statistics necessary for precise measurements of the induced polarization P and the polarization transfer coefficient DNN1. Figure 1 shows a sample focal plane spectrum taken at a laboratory angle of 30" with a 5 mg/cm2 target. All ...

The curse of nucleon-nucleus scattering has always components of the nuclear response.3 The forme... more The curse of nucleon-nucleus scattering has always components of the nuclear response.3 The former been the enormous complexity of the elementary quantity is uniquely accessible via nucleon scattering nucleon-nucleon interaction. Few if any other forces and plays a pivotal role in explanations of the EttC involve such a wide range of basic fields. Recently, effect based on "excess" nuclear pions. Surprisingly however, a revolution of experimental technique has these measurements cast serious doubt on the validity shown that this diversity may prove to be the ultimate of such explanations and also suggest that the momentum promise of medium-energy nucleons as probes of the dependence of the residual spin-isospin interaction is nuclear response. In just the past four years the still at best only poorly understood. development of high-efficiency, high-resolution In short, (p,pO) polarization transfer observables instruments for acquiring complete sets of have shown us a means...

Journal of Instrumentation, 2021

In order to provide proton beams polarized along any axis to any experimental area, IUCF has purc... more In order to provide proton beams polarized along any axis to any experimental area, IUCF has purchased and installed two superconducting solenoids for the high energy beam lines.' Each has the capability to precess 200 MeV protons through an angle of about 120°. The magnets are wound with about 20,000 turns of NbTi wire imbedded in a copper matrix, and have iron return yokes to minimize stray fields so that nearby magnetic elements along the beam line are not affected. The vacuum flanges are machined directly into each return yoke, and the bore through which the beam passes is at room temperature. The two magnets are located just upstream and downstream of the 45O energy analysis magnet in beam line 3. This arrangement is shown schematically in Fig. 1. With no solenoid field, the spin axis of the beam is nominally vertical through this system. To produce a sideways polarization in the beam line downstream of the analysis magnet,

arXiv: High Energy Physics - Experiment, 2019

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron,... more The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly helium-3) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY (Cooler Synchrotron, Forschungszentrum J\"ulich) activities that demonstrate technical feasibility. Achievements to date include reduced polarisation measurement errors, long horizontal-plane polarisation lifetimes, an...

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2021

Physical Review Accelerators and Beams, 2018

The European Physical Journal C, 2020

In this paper analytical expressions are derived to describe the spin motion of a particle in mag... more In this paper analytical expressions are derived to describe the spin motion of a particle in magnetic and electric fields in the presence of an axion field causing an oscillating electric dipole moment (EDM). These equations are used to estimate statistical sensitivities for axion searches at storage rings. The estimates obtained from the analytic expressions are compared to numerical estimates from simulations in Chang et al. (Phys Rev D 99(8):083002, 2019). A good agreement is found.