Section Asymmetry Research Articles

Study of the e+e− → μ+μ−γ reaction at center-of-mass energies between 54 and 64 GeV

Abstract The cross section and forward-backward muon charge asymmetry for the e+e−→μ+μ−γ reaction were measured to be σ=2.82±0.35 pb and A=−0.34±0.10 with the VENUS detector at TRISTAN at 〈√s〉=59.2GeV for an integrated luminosity of 53.5 pb−1. The measured cross section agrees with the theoretical prediction. The asymmetry result is consistent with the electroweak prediction but not with the QED prediction at the level of 2σ.

A measurement of electroweak effects in the reactione + e ? ? ?+?? at 35.0 and 42.4 GeV

We report on total cross section and forward backward charge asymmetry measurements of the reactione + e − → τ+τ− at centre of mass energies of 35.0 GeV and 42.4 GeV using the TASSO detector. Including previous data an analysis in terms of electroweak parameters of the standard model is presented, and lower limits on mass scale parameters of residual contact interactions are given. A combined analysis of electroweak couplings using all our results on leptonic reactionse + e −→l + l − has been performed.

An analytical bound on the asymmetry of a section of a typical three‐dimensional brownian path

On caracterise l'asymetrie d'une section d'un chemin brownien typique a 3 dimensions en utilisant le moment du tenseur d'inertie par rapport au centre de masse. On presente une nouvelle methode pour determiner une borne superieure sur la moyenne d'ensemble de la plus petite valeur propre

Spin-orbit forces in knockout reactions

The spin-orbit final-state interaction for the one-nucleon knockout reaction is studied in perpendicular kinematics using an eikonal formalism to investigate experimentally observed cross- section asymmetries. Our results elucidate previous numerical calculations indicating sensitivity of these asymmetries (as a function of the nuclear recoil momentum) to the imaginary part of the spin-orbit potential.

Electrically weak asymmetry in the elastic scattering of electrons by nuclei with multipole moments

The differential elastic-scattering cross section of longitudinally polarized electrons by nuclei of arbitrary spin and isospin is calculated in the Born approximation, taking into account the interference of electromagnetic interaction and the interaction of weak neutral currents. For a nucleus of spin J ⩽ 3/2, explicit expressions are obtained for the interference terms in terms of the electromagnetic multipole form factors FC, fQ, fM1 and fM3. Using the example of the3He,11B,19F and40Ca nuclei, the behavior of electrically weak asymmetry of the cross section is investigated in detail in the framework of three gauge models. It is shown that the asymmetry of aRl is ∼10−5 for E ∼- 100 MeV, and is sensitive to the nuclear structure: By taking into account the contributions not only of the charge and magnetic-dipole scattering but also of the quadrupole and octupole scattering, one can obtain additional information on the structure of weak electron-nucleus interaction.

Polarized Lepton Scattering as a Probe of Gauge Models

Asymmetry of cross sections between high energy lepton beams of opposite helicities is shown to provide a useful probe of unified gauge models of weak and electromagnetic interac­ tions. Recently, absence of parity violation in heavy atoms 11 has cast a considerable doubt on ultimate validity of the W einberg-Salam model (W-S) / 1 and prompted many alternative models several of which are referred below. Further crucial search of neutral current phenomena, besides the well-established neutrino process, will be carried out in measurements of parity violation in lighter atoms 31 and forward-backward asymmetry in the reaction e+ e- -'>/.f.+ !J.- 41 at PEP and PETRA energies, both of which are discussed extensively in literatures. 31 ' 41 On the other hand, it was shown 51 that asymmetry of inclusive cross sections between opposite, longitudinally-polarized lepton beams ranges up to 3% for Q 2 = 100 Ge V 2 and the full strength GF of neutral current (V-A) coupling. The effect was further applied 61 to the W-S in which the asymmetry is found several times reduced due to an accidental value of the weak mixing angle Bw. The purpose of this paper is to further extend this result such that one can find expressions of the asymmetry

Corrections to the Impulse Approximation for High-Energy Neutron Scattering from Liquid Helium

Corrections to the impulse approximation for scattering from a many-body system are derived in the form of a series in inverse powers of the momentum transfer $k$. The coefficients in this series are written in terms of the two-body interaction potential and the particle-density matrices. Application is made to the case of high-energy neutron scattering from liquid helium. Evaluation of correction terms corresponding to a single helium-helium collision during the neutron-helium interaction time indicates (a) a shift in the peak of the incoherent-scattering cross section toward lower energy by a constant amount, and (b) an asymmetry of the cross section with respect to neutron energy loss about its peak value. Numerical estimates are given for these two effects for $k=14.3$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$. Evaluation of condensate broadening due to multiple He-He collisions shows that the condensate-scattering contribution has a width proportional to ${k}^{\frac{1}{2}}$, and is thus distinguishable from the main noncondensate peak whose width is proportional to $k$. Estimates are given for requirements on experimental-resolution functions necessary to preserve this evidence of a distinct condensate contribution.

A Regge Pole Model for Charged Pion Photoproduction

A fit to high energy charged pion photoproduction in the relatively forward direction is performed on the basis of a Regge pole model, where the existence of the pion conspirator is assumed to explain the sharp forward peak. New experimental data on the asymmetry in the cross sections between two states of the polarization of the initial proton normal to the plane of scattering are taken account of, in addition to the other available data up to the present. Good fits are obtained with the inclusion of the strong fixed pole effect for the p residue function at the wrong signature nonsense point a P (t) = 0. It also becomes clear that the p and A 2 trajectories play very important role in the region 0.3< v' -t<0.7. Furthermore the difficulty of pion conspiracy in connection with the reaction n+p~pOJ++ is discussed.

The reaction 2H(p, 2p)n studied with 10.5 MeV polarized protons

Abstract The asymmetry of the cross section in the complete 2 H(p, 2p)n experiment induced by 10.5 MeV polarized protons is measured at four sets of angles; one proton is detected at θ 1 = 30° and the other at θ 2 = −30°, −65°, −71° and -75°. For the set of angles θ 1 = 30°, θ 2 = −71° and −75°, the cross sections exhibit the characteristic peaks corresponding to a minimum correlation energy between a neutron and a proton in the singlet 1 S 0 state. The asymmetry is significantly different from zero and reaches 0.054±0.018 at the n-p pole. At ( θ 1 = 30°, θ 2 = −65°) the cross section appears to be double-peaked, which seems to indicate an interference effect. For the measurement at ( θ 1 = 30°, θ 2 = −30°) the cross section exhibits a smooth maximum corresponding to a minimum energy of the spectator neutron. The Kuckes-Wilson-Cooper theory gives a peak broader than the experimental one, with an absolute value too high by a factor of approximately two. The corresponding asymmetry is zero within the limits of statistical error.

Asymmetry of (d, p) Cross Section for a PolarizedHe3Target

Asymmetry of (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>d</mml:mi><mml:mo>,</mml:mo><mml:mi> </mml:mi><mml:mi>p</mml:mi></mml:math>) Cross Section for a Polarized<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Target

Scattering ofμMesons from the Nuclei of Bromine and Silver

The mu -meson elastic scattering cross section and polarization asymmetry factor are calculated for bromine for positive and negative muons, and for silver for negative muons, for the values of nu /c = 0.4, 0.6, and 0.7. These results, when combined with the ones available for cadmium, permit the comparison of theory with measurement of the scattering of muons in emulsions. The nuclei are taken to be extended, with a charge distribution as derived from electron scattering, the Dirac equation is assumed valid, and the calculation is done with the aid of an IBM650 computer utilizing the same program as used previously for the calculations on cadmiurn and mercury. (auth)

Cross Section and Decay Asymmetries of Neutral V Particles Produced in Copper byπ−Mesons

Cross Section and Decay Asymmetries of Neutral V Particles Produced in Copper by<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>Mesons