121171727
Electromagnetic structure of the helium isotopes
The elastic-electron scattering cross sections from $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ have been measured at incident electron energies between 170 and 750 MeV. Cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. Values of the $^{3}\mathrm{He}$ charge form factor have been extracted to ${q}^{2}=20$ ${\mathrm{fm}}^{\ensuremath{-}2}$ and for the $^{3}\mathrm{He}$ magnetic form factor to ${q}^{2}=16$ ${\mathrm{fm}}^{\ensuremath{-}2}$. The $^{4}\mathrm{He}$ form factor has been determined up to 6.2 ${\mathrm{fm}}^{\ensuremath{-}2}$. Densities for the charge and magnetization have been deduced from phenomenological models used in a phase-shift solution of the Dirac equation. A model-independent determination of the nuclear densities has been performed in order to obtain realistic errors on the extracted distributions. After unfolding the nucleon size from the distributions the point density is shown to have a significant central depression for a radius 0.8 fm for both $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$. Comparison of the form factors is made with Faddeev and variational three-body calculations that use realistic two-body $\mathrm{NN}$ interactions. The influence of off-shell effects, three-body forces, meson-exchange corrections, and short-range correlations are discussed. At present no theoretical calculation that uses input derived entirely from nucleon-nucleon scattering is able to reproduce the experimental data.
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.
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.
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.
121665406
Quark-parton models and the neutron charge radius
121309706
Measurements of magnet quench levels induced by proton beam spray
A superconducting dipole magnet was installed in the Fermilab primary beam line. Targets were inserted in the proton beam upstream of the magnet and measurements made of the energy deposition within the magnet sufficient to cause quenching. The quench levels were 25 mW/g for 1 sec beam spill and 1 mJ/g for a spill of 1 msec or less. In comparison, the energy deposition at the extraction septum was 0.6 mJ/g.
119113679
Search for CP violation in the decay $D^+ \to \pi^-\pi^+\pi^+$
A search for CP violation in the phase space of the decay $D^+\to\pi^-\pi^+\pi^+$ is reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The Dalitz plot distributions for $3.1\times 10^6$ $D^+$ and $D^-$ candidates are compared with binned and unbinned model-independent techniques. No evidence for CP violation is found.
17306575
First measurement of the charge asymmetry in beauty-quark pair production.
The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in bb pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0 fb(-1) collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the bb system. The results obtained are A(C)(bb))(40 105 GeV/c(2)) = 1.6 ± 1.7 ± 0.6%, where A(C)(bb)) is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark, where in each case the first uncertainty is statistical and the second systematic. The beauty jets are required to satisfy 2 < η < 4, E(T) >20 GeV, and have an opening angle in the transverse plane Δ ϕ > 2.6 rad. These measurements are consistent with the predictions of the standard model.
123047078
Anomalies in covariant W gravity
Abstract We consider free scalar matter covariantly coupled to background W-gravity. Expanding to second order in the W-gravity fields, we study the appropriate anomalous Ward-Takahashi identities and find the counterterms which maintain diffeomorphism invariance and its W-analogue. We see that a redefinition of the vielbein transformation rule under W-diffeomorphism is required in order to cancel nonlocal contributions to the anomaly. Moreover, we explicitly write all gauge invariances at this order. Some consequences of these results for the chiral gauge quantization are discussed.
11644763
Mechanical and Electrical Design of the Fermilab Lithium Lens and Transformer System
A lithium lens focusing device will be used for the collection of 8 GeV antiprotons in the Fermilab Tevatron I Project. The details of the mechanical and electrical design of the Fermilab lens and its associated toroidal transformer are discussed. The lens, with a radius of 1 cm and length 15 cm, is expected to achieve gradients of 1000 T/m for a focal distance of 0.225 m. The gradient requires a current on the order of 5x105A, resulting in large electromagnetic and thermal stresses. The power supply discharge current and the effect of the inductance of the power leads and connections are minimized by the use of a toroidal matching transformer surrounding the lens itself.