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.
120271972
Negative pion capture on 4He with emission of neutron-proton, neutron-deuteron and neutron-triton pairs
Abstract The energies and opening angles for neutron-proton, and neutron-deuteron pairs emitted after π− capture in 4He have been measured. The data are compared to available theoretical calculations. Both energetic protons and deuterons are strongly correlated in direction with an energetic neutron, being emitted at approximately 180° to each other. A strong enhancement at the high-energy end of the deuteron spectrum is attributed to a strong final state interaction between the remaining two neutrons.
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.
121021036
G**p(E) / G**p(M) for bound protons: first results for O-16 with the recoil polarization technique
The first (e,e'p) polarization transfer measurements on a nucleus heavier than deuterium have been carried out at Jefferson Laboratory. Transverse and longitudinal components of the polarization of protons ejected in the reaction 16O(e,e'p) were measured in quasielastic perpendicular kinematics at a Q^2 of 0.8 (GeV/c)^2. The data are in good agreement with state of the art calculations, but do not exclude possible changes in the ratio of the electric to magnetic form factors of the nucleon in the nuclear medium at the level of recent theoretical predictions.
121665406
Quark-parton models and the neutron charge radius
8388828
Observation of photon polarization in the b→sγ transition.
This Letter presents a study of the flavor-changing neutral current radiative B±→K±π∓π±γ decays performed using data collected in proton-proton collisions with the LHCb detector at 7 and 8 TeV center-of-mass energies. In this sample, corresponding to an integrated luminosity of 3  fb-1, nearly 14 000 signal events are reconstructed and selected, containing all possible intermediate resonances with a K±π∓π± final state in the [1.1,1.9]  GeV/c2 mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in intervals of K±π∓π± mass and the asymmetry between the number of signal events found on each side of the plane is obtained. The first direct observation of the photon polarization in the b→sγ transition is reported with a significance of 5.2σ.
38254483
Very High Precision Current Regulated Power Supplies for the Fermilab Antiproton Source
These Power Supplies were designed to power the accumulator and debuncher storage rings at the Fermi National Accelerator Laboratory Antiproton Source. The accumulator and debuncher are both large acceptance 8 GeV storage rings. The accumulator ring has the most stringent requirements since it will be required to store beams for periods in excess of twenty four (24) hours. In order to ensure long term beam stability, resonances up to order eleven (11) must be avoided. Because of this stringent tuned stability requirement, the power supplies which power the three main quadrupole and the main dipole busses must be extremely stable. Thus the current regulation specification for these power supplies is 10 PPM (0.001%) including differential and common mode ripple, long term drift, and line and load regulation.
54960779
Measurement of the resonant and CP components in $\overline{B}^0\to J/\psi \pi^+\pi^-$ decays
The resonant structure of the reaction $\overline{B}^0\rightarrow J/\psi \pi^+\pi^-$ is studied using data from 3 fb$^{-1}$ of integrated luminosity collected by the LHCb experiment, one-third at 7 Tev center-of-mass energy and the remainder at 8 Tev. The invariant mass of the $\pi^+\pi^-$ pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. Six interfering $\pi^+\pi^-$ states: $\rho(770)$, $f_0(500)$, $f_2(1270)$, $\rho(1450)$, $\omega(782)$ and $\rho(1700)$ are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative CP fractions of each of the resonant final states are determined. The $f_0(980)$ meson is not seen and the upper limit on its presence, compared with the observed $f_0(500)$ rate, is inconsistent with a model of tetraquark substructure for these scalar mesons at the eight standard deviation level. In the $q\overline{q}$ model, the absolute value of the mixing angle between the $f_0(980)$ and the $f_0(500)$ scalar mesons is limited to be less than $17^{\circ}$ at 90% confidence level.
22966047
Measurement of the $\Lambda_b^0$, $\Xi_b^-$ and $\Omega_b^-$ baryon masses
Bottom baryons decaying to a J/\psi\ meson and a hyperon are reconstructed using 1.0 fb^{-1} of data collected in 2011 with the LHCb detector. Significant \Lambda_b^0 \rightarrow J/\psi \Lambda, \Xi_b^-\rightarrow J/\psi \Xi^- and \Omega_b^- \rightarrow J/\psi \Omega^- signals are observed and the corresponding masses are measured to be M(\Lambda_b^0) = 5619.53 \pm 0.13 (stat) \pm 0.45 (syst) MeV/c^2, M(\Xi_b^-) = 5795.8 \pm 0.9 (stat) \pm 0.4 (syst) MeV/c^2, M(\Omega_b^-) = 6046.0 \pm 2.2 (stat) \pm 0.5 (syst) MeV/c^2, while the differences with respect to the \Lambda_b^0 mass are M(\Xi_b^-)-M(\Lambda_b^0) = 176.2 \pm 0.9 (stat) \pm 0.1 (syst) MeV/c^2, M(\Omega_b^-)-M(\Lambda_b^0) = 426.4 \pm 2.2 (stat) \pm 0.4 (syst) MeV/c^2. These are the most precise mass measurements of the \Lambda_b^0, \Xi_b^- and \Omega_b^- baryons to date. Averaging the above \Lambda_b^0 mass measurement with that published by LHCb using 35 pb^{-1} of data collected in 2010 yields M(\Lambda_b^0) = 5619.44 \pm 0.13 (stat) \pm 0.38 (syst) MeV/c^2.
146045278
Test of lepton universality using $B^{+}\rightarrow K^{+}\ell^{+}\ell^{-}$ decays
A measurement of the ratio of the branching fractions of the $B^{+}\rightarrow K^{+}\mu^{+}\mu^{-}$ and $B^{+}\rightarrow K^{+}e^{+}e^{-}$ decays is presented using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded with the LHCb experiment at center-of-mass energies of 7 and 8 $\mathrm{\,Te\kern -0.1em V}$. The value of the ratio of branching fractions for the dilepton invariant mass squared range $1<q^{2}<6\mathrm{\,Ge\kern -0.1em V^2\!/}c^4$ is measured to be $0.745^{+0.090}_{-0.074}\mathrm{\,(stat)}\,\pm0.036\mathrm{\,(syst)}$. This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the SM prediction within $2.6$ standard deviations.