Bhabha scattering at a center-of-mass energy of 57.77 GeV has been measured using the VENUS detector at KEK TRISTAN. The precision is better than 1% in scattering angle regions of |cosθ|⩽0.743 and 0.822⩽cosθ⩽0.968. A model-independent scattering-angle distribution is extracted from the measurement. The distribution is in good agreement with the prediction of the standard electroweak theory. The sensitivity to underlying theories is examined, after unfolding the photon-radiation effect. The q2 dependence of the photon vacuum polarization, frequently interpreted as a running of the QED fine-structure constant, is directly observed with a significance of three standard deviations. The Z0 exchange effect is clearly seen when the distribution is compared with the prediction from QED (photon exchanges only). The agreement with the standard theory leads us to constraints on extensions of the standard theory. In all quantitative discussions, correlations in the systematic error between angular bins are taken into account by employing an error matrix technique.
Cross section is integrated over the cos(theta ) bin.
The differential cross-sections for e + e − → e + e − , e + e − → μ + μ − and e + e − → τ + τ − , and the total cross-section for e + e − → qq̄ at centre-of-mass energies of 130–140 GeV were studied using about 5 pb −1 of data collected with the OPAL detector at LEP in October and November 1995. The results are in agreement with the Standard Model predictions. Four-fermion contact interaction models were fitted to the data and lower limits were obtained on the energy scale Λ at the 95% confidence level.
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Hadronic and leptonic cross-sections and forward-backward asymmetries are measured using 5.7 pb −1 of data taken with the ALEPH detector at LEP at centre-of-mass energies of 130 and 136 GeV. The results agree with Standard Model expectations. The measurement of hadronic cross-sections far away from the Z resonance improves the determination of the interference between photon and Z exchange. Constraints on models with extra Z bosons are presented.
Data with loose SPRIME cut.
Data with tight SPRIME cut.
Data with loose SPRIME cut.
Differential cross sections for p p elastic scattering have been measured for very small momentum transfers at six different incident antiproton momenta in the range 3.7 to 6.2 GeV/c by the detection of recoil protons at scattering angles close to 90°. Forward scattering parameters σ T , b , and ϱ have been determined. For the ϱ-parameter, up to an order of magnitude higher level of precision has been achieved compared to that in earlier experiments. It is found that existing dispersion theory predictions are in disagreement with our results for the ϱ-parameter.
Results of the SIG(T)-free analysis. Errors include systematic uncertainties.
Results of the SIG(T)-fixed analysis. Errors include systematic uncertainties.
CT values of the total cross section from the SIG(T)-free analysis. Errors include systematic uncertainties.
The polarization transfer κ 0 and the tensor analyzing power T 20 for the 1 H d p)d reaction have been measured up to an internal momentum of k = 0.58 GeV/c. Comparison of the same observables obtained in recent studies for 1 H d p)d reaction, as a function of k , show different behavior. However the data from these two reactions are almost identical when compared in T 20 versus κ 0 correlation plots. We discuss similarities and differences observed in the two reactions.
The authors use the Infinite Momentum Frame variable K= M( proton) * sqrt(1/(4*a*(1-a)) - 1), where a = (E(proton)+P_long(proton))/(E(deut)+P(deut)).
The proton-antiproton total cross section was measured at the center-of-mass energy of s = 541 GeV at the S p pS at CERN using a luminosity dependent method. The result σ tot =63.0±2.1 mb is in agreement with the luminosity independent measurement performed earlier by the UA4 Collaboration.
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We report on the measurement of the leptonic and hadronic cross sections and leptonic forward-backward asymmetries at theZ peak with the L3 detector at LEP. The total luminosity of 40.8 pb−1 collected
Results from 1990 data. Additional systematic uncertainty of 0.3 pct.
Results from 1991 data. Additional systematic uncertainty of 0.15 pct.
Results from 1992 data. Additional systematic uncertainty of 0.15 pct.
We present data of several rescattering observables measured inn p elastic scattering between 0.80 and 1.10 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the Saclay polarized frozen-spin proton target. Three different configurations of beam and target polarization directions were used: the observablesDonon andKonno were measured with the normal-normal spin configuration at eight energies;Nonkk,Dos″ok andKos″ko were determined with the longitudinal-longitudinal configuration at six energies;Nonsk,Dos″ok andKos″so with the sideway-longitudinal configuration at six energies. Part of the data was obtained with an unpolarized CH2 target where only the two spin-index polarization transfer parametersKos″ko andKos″so were determined. Data are compared with phase shift analyses predictions and with the LAMPF results at 0.788 GeV. Present results are the first measurements of rescattering observables above 0.80 GeV. They provide an important contribution to any future theoretical or phenomenological analysis.
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The spin correlation parameter A00NN for 497.5 MeV proton + proton elastic scattering was determined over the center-of-momentum scattering angle region 23.1°–64.9 °. The new A00NN extend to more forward angles than existing A00NN and have significantly smaller statistical errors (±0.01–0.04). The A00NN are qualitatively described by recent phase shift analyses, but a quantitative shape and normalization discrepancy remains in the forward angle region. These new data provide important constraints for nucleon-nucleon spin-dependent amplitudes at forward angles which are used in theoretical models of nucleon-nucleus scattering.
Errors include statistical and systematic uncertainties.
We present a total of 191 and 203 data points of the elastic neutron-protonspin correlation parameters A ookk and A oosk , respectively. Both observables were measured in a large angular interval. The observable A ookk was measured from 0.312 to 1.10 GeV and A oosk from 0.80 to 1.10 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. The beam polarization was oriented either along the beam direction or sideways, the target polarization was oriented longitudinally. Data are compared with phase-shift analyses predictions and with the PSI, LAMPF and SATURNE II results. Present results provide an important contribution to any future theoretical or phenomenological analysis.
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