44148782
Measurement of the deuteron polarization in a large target
Abstract The 10-probe NMR system for measuring the polarization in the deuterated butanol target of the Spin Muon Collaboration is presented. It is calibrated by determining the integrated spectrum in thermal equilibrium at 1 K. Thermal stabilization and control of electromagnetic interference were effective in reducing drift and electronic noise, so that high quality thermal equilibrium signals were obtained. The calibration constant was determined with a reproducibility of 2%. Systematic effects of circuit drift and of the magnetic field shift have been studied. The resulting 4.4% uncertainty of the calibration dominates the 5% overall error on the target polarization value which was typically 0.45.
120014689
Pion-helium scattering above the (3,3) resonance
Differential cross sections are reported for ..pi../sup +/+/sup 3,4/He elastic scattering at 260, 295, and 310 MeV and ..pi../sup -/+/sup 3,4/He at 295 MeV. The angular distributions )except for ..pi../sup -/+/sup 3/He) confirm the fixed angle (thetaapprox. =75/sup 0/) minimum seen at lower energies (caused by the (3,3) ..pi..+N resonance dominance) and show a deep minimum at thetaapprox. =110/sup 0/. Comparisons are made to ..pi..+d and the current discussion of pion excitation of intermediate dibaryon and ..delta..N states.
121139038
CEBAF — a high energy, high duty factor electron accelerator for nuclear physics☆
Abstract The Nuclear Science Advisory Committee has recommended the construction of the Continuous Electron Beam Accelerator Facility (CEBAF) as proposed by the Southeastern Universities Research Association (SURA), a consortium of more than thirty institutions in the southeastern United States. The accelerator will be capable of delivering intense (Iave > 100 μA), quasi-continuous (duty Factor > 90%) beams of electrons with energies up to 4.8 GeV. Short (1.2 μs), intense (Ipk = 200 mA) pulses of electrons will be accelerated by passing twice through a conventional pulsed linac. The pulses then will be injected into and stored in a pulse stretcher ring, the circumference of which is close to the length of the electron pulse. During the period between pulses (1ms) the stored electrons will be extracted to yield a high duty factor beam. Delivery of arbitrarily polarized beams will be possible. Experimental facilities will include three end stations. Two will be used for experiments utilizing the primary electron beam; the third will serve as a tagged photon facility.
32493630
Computer Modeling of Internal Targets in Electron Storage Rings
The effect of thin (1-50 ¿gm/cm2) internal targets on beam quality in electron storage rings is evaluated. The internal target is modeled assuming that scattering is the result of elastic collisions between the beam electrons and the target nuclei. A screened coulomb potential is used and single and plural scattering mechanisms are included. A storage ring particle tracking code, DIMAT, was modified to include the internal target model and used to obtain the results discussed. Beam particle loss distributions and beam envelope "growth times" are given and discussed in light of damping mechanisms inherent in electron storage ring designs.
121665406
Quark-parton models and the neutron charge radius
122290195
Off-shell effects in quasielastic electron nucleus scattering
Using the Ward-Takahashi identity, on-shell condition, bound Dirac equation and off-shell expansion, a reduced version of half off-shell virtual photon nucleon vertex has been suggested. The vertex are decomposed into several different order terms: the on-shell terms, first and second off-shell terms. The off-shell behaviour of the form factors is discussed in the one meson loop model. Using the reduced vertex and parametrized off-shell form factors the quasielastic response functions are calculated for several nuclei at ¦q¦–kf and for56Fe at large ¦q¦ up to 1.14 GeV/c and at −q2=0.9 (GeV/c)2. The Coulomb sums are evaluated and a comparison of the theoretical prediction with data is given. The off-shell electron nucleon cross section is calculated and compared with the “cc1” off-shell extrapolation.
120816642
A mechanism for fermion mass generation
Abstract We present a mechanism for fermion mass generation, and apply it to the lepton sector of the Weinberg-Salam model. Extra fields, necessary to produce the large mass splittings of the observed fermions, form bound states more massive than the electroweak scale.
18451170
Induced Chern-Simons terms
We examine the claim that the effective action of four-dimensional SU(2)_L gauge theory at high and low temperature contains a three-dimensional Chern-Simons term with coefficient being the chemical potential for baryon number. We perform calculations in a two-dimensional toy model and find that the existence of the term is rather subtle.
122010777
Spin and Statistics of Gravitational Anyons
We determine the spin and statistics of a particle in 2 + 1 dimensions coupled to linearized gravity with a Chern-Simons term. The model and the results are compared to those of the corresponding abelian vector theory. The statistics emerge from the effective particle-particle interaction, while the spin is computed using the symmetric stress tensor of the system. We find that the spin-statistics relation is satisfied. In the gravitational case we show that while stress tensors are never gauge invariant, the Poincare generators are; in particular, despite subtleties peculiar to two spatial dimensions, there are no “superpotential” ambiguities in these generators.
118576704
First measurement of the CP-violating phase in $B_s^0 \to \phi \phi$ decays
A first flavour-tagged measurement of the time-dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between $B_s^0$-$\bar{B}_s^0$ mixing and the $b \to s \bar{s} s $ gluonic penguin decay amplitude. Using a sample of $pp$ collision data corresponding to an integrated luminosity of $1.0\; fb^{-1}$ and collected at a centre-of-mass energy of $7 \rm TeV$ with the LHCb detector, $880\ \B_s^0 \to \phi\phi$ signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46, -0.76] \rm rad$ at 68% confidence level. The p-value of the Standard Model prediction is 16%.
21928269
Large Dynamic Range Beam Profile Measurement in a High Background Environment
Beam profile measurements using a scanning target and loss monitor in the Fermilab Main Ring extraction channel have long proved their usefulness as a diagnostic method in analyzing extraction problems. To extend these measurements to a sensitivity greater than in the present system a different technique has been employed. A simple three element particle telescope viewing the scanning target allows a sensitive measurement of the tail on the edges of the beam profiles as well as the relative particle densities of the extracted beam and the circulating beam in the Main Ring. Both these regions are of significant interest in understanding extraction losses. The details of the profile measurement technique, some results using the telescope and possible methods of improving the measurements are discussed.