Cross sections for pi+-p elastic scattering have been measured to high precision, for beam momenta between 800 and 1240 MeV/c, by the EPECUR Collaboration, using the ITEP proton synchrotron. The data precision allows comparisons of the existing partial-wave analyses (PWA) on a level not possible previously. These comparisons imply that updated PWA are required.
Differential cross section of elastic $\pi^+$p-scattering at P= 800.25 MeV/c. Errors shown are statistical only.
Differential cross section of elastic $\pi^+$p-scattering at P= 803.75 MeV/c. Errors shown are statistical only.
Differential cross section of elastic $\pi^+$p-scattering at P= 807.25 MeV/c. Errors shown are statistical only.
The total and differential cross sections of the process e+e- -> n gamma with n >= 2 are measured using data collected by the L3 experiment at centre-of-mass energies of \sqrt{s}=183 and 189 GeV. The results are in agreement with the Standard Model expectations. Limits are set on deviations from QED, contact interaction cut-off parameters and masses of excited electrons.
Measured cross section.
Measured differential cross sections corrected for efficiency and additional photons as a function of cos(theta) where theta is the polar angle of the event defined as. cos(theta)=ABS((sin(theta1-theta2)/2)/(sin(theta1+theta2)/2)).
Analysing powers and differential cross sections for p p → π − π + and p p → K − K + have been measured over the full angular range using a polarised target at LEAR at 20 beam momenta from 360 to 1550 MeV/ c . Discrepancies in the normalisation of earlier d σ/ d Ω data at low momenta are clarified. Above 1000 MeV/ c , A 0N results confirm values close to +1 over most of the angular range for both reactions, in excellent agreement with earlier data of lower statistics. Below 1000 MeV/ c , where the analysing power is measured for the first time, large variations of A 0N with energy and angle are present.
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Measurements have been made of the differential cross section and asymmetry A on for p p elastic scattering at 15 incident momenta between 497 MeV/ c and 1550 MeV/ c . The angular range where both particles have enough energy to traverse target and setup has been covered. The results are compared with predictions of various N N potential models. None of these models fully explains the present results, although the general trend of the data is predicted correctly.
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An analysis of the three leptonic reactionse+e−→e+e−,μ+μ− andτ+τ− over a wide range of energy,\(12< \sqrt s< 46.78 GeV\) is presented. The data were obtained with the JADE detector at thee+e− storage ring PETRA. They are compared to predictions of electroweak theories, in particular the standard model. For the total cross-sections of all three reactions and for the differential cross-section of Bhabha scattering no deviation from QED is found over the entire energy range. The differential cross-sections of μ and τ pairs at high energies show the angular asymmetry predicted by electroweak interference. The axial-vector and vector weak coupling constant, sin2θW andMZ are determined and compared to other measurements. Finally, limits on deviations from the standard model are given.
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The production and decay of τ-pairs was studied with the JADE detector at PETRA at center-of-mass energies of 30 ⩽√ s ⩽ 46.78 GeV. The total production cross section for τ-pairs agreed with QED predictions to order α 3 . Lower limits on QED cut-off parameters of Λ + > 285 GeV and Λ − > 210 GeV at 95% confidence level were ontained. The decay branching fractions into one and three charged particles were determined to be (86.1 ± 0.5 ± 0.9)% and (13.6±0.5 ±0.80)%. In the angular distributions a forward-backward asymmetry was observed, from which the axial-vector weak charge to the τ was determined to be a τ = −0.74 ± 0.22 in agreement with the standard model. An analysis of the process e + e − → τ + τ − γ showed agreement with QED calculations to O(α 3 ).
Includes data from earlier analysis at lower energy - M. Nozaki - Tokyo - UTLICEPP-82-02.
Angular distributions - data requested from authors.
Forward-backward asymmetry determined from fit to angular distribution of form N*(1 + cos(theta)**2 + (3/8)*A*cos(theta)).
The production of collinear muon pairs has been studied using the JADE detector at thee+e− storage ring at PETRA. Results for the total cross section and the angular distribution were obtained at centre of mass (cm) energies ranging from 12 to 46 GeV. The data correspond to an integrated luminosity offLdt>90 pb−1, of which 71.2 pb−1 were taken at\(\left\langle {\sqrt s } \right\rangle \)=34.4 GeV and 17 pb−1 at\(\left\langle {\sqrt s } \right\rangle \)=42.4 GeV. The results are compared to electroweak theories, in particular the “Standard Model”.
QED comparison is to point like cross section.
Angular distributions - data requested from authors.
Forward-backward asymmetry calculated from a fit to the angular distribution of the form 1: + cos(theta)**2 + Bcos(theta).. Asymmetries quoted here are extrapolated to full solid angle. The asymmetry at sqrt(s) = 34.4 is -11.10 +- 1.75 +- 1.0 pct if the end-cap points are included.
Cross sections for the reactionse+e−→e+e− (Bhabha scattering) ande+e−→γγ are measured for center-of-mass (c.m.) energies\(\sqrt s \) between 12.0 and 34.6 GeV. The results agree with the predictions of Quantum Electrodynamics (QED) and the cut-off parameters are determined. From Bhabha scattering at the highest energy,\(\left\langle {\sqrt s } \right\rangle= 34.6 GeV\), the 1 δ limits 0.12<sin2 ϑw<0.38 are obtained for the weak mixing angle. The higher order (α3) QED processese+e−→e+e−γ ande+e−→γγγ are also studied and are found to agree with the α3 QED predictions. A search for excited electrons is carried out by investigating the (e±γ) invariant mass distribution in the reactione+e−→e+e−γ.
Total cross sections.
Angular distribution.
Angular distribution.
The angular distribution and the s dependence of the total cross section for the process e + e − → μ + μ − have been measured using the JADE detector at PETRA. After radiative corrections, a forward-backward asymmetry of −(11.8±3.8) % was observed at an average centre of mass energy of 33.5 GeV. For comparison, an asymmetry of −7.8 % is expected on the basis of the standard Glashow-Salam-Weinberg model.
Best fit to total cross section in energy range.
ANGULAR DISTRIBUTION.
Forward-backward asymmetry within the acceptnce region.
The processes e + e − → e + e − and μ + μ − have been studied at PETRA using the JADE detector. The data, which were collected at s -values of up to 1300 GeV 2 have been analysed in terms of an electro-weak extension of QED to obtain values for the weak vector and axial vector couplings in the lepton sector. The values obtained agree with the predictions of the standard Salam-Weinberg model and the data are further analysed in terms of this model to obtain the limits 0.10 < sin 2 ϑ w < 0.40 (68% CL). The mass of the neutral weak gauge boson is deduced to be greater than 51 GeV/ c 2 .
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