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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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.
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By combining results from the MARK-J at PETRA on Bhabha scattering, μ + μ - and τ + τ - production with recent world data from neutrino-electron scattering experiments, we determine unique values for the leptonic weak neutral current coupling constants g V and g A in the framework of electroweak models containing a single Z 0 . In contrast to previous analyses, we only use data from purely leptonic interactions, and therefore avoid the inherent uncertainties resulting from the use of hadronic targets. From the MARK-J data alone in the context of the standard SU(2) ⊗ U (1) model of Glashow, Weinberg and Salam, we find sin 2 θ W =0.24±0.11.
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The np elastic differential cross section has been measured for incident neutron momenta 100–400 GeV/ c in the | t | range 6 · 10 −6 − 5 · 10 −1 (GeV/ c ) 2 . The np data of this experiment provide a first direct measurement of the hadronic amplitude for | t | < 10 −2 (GeV/ c ) 2 , which is consistent with the extrapolations from higher | t | values. Our data for | t | < 10 −4 (GeV/ c ) 2 are consistent with a rise which can be attributed to Schwinger scattering, caused by the interaction of the neutron magnetic moment with the proton.
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We report on high statistics Bhabha scattering data taken with the TASSO experiment at PETRA at center of mass energies from 12 GeV to 46.8 GeV. We present an analysis in terms of electroweak parameters of the standard model, give limits on QED cut-off parameters and look for possible signs of compositeness.
Axis error includes +- 1/1 contribution (The overall uncertainty in the bin-to-bin polar acceptance due to shower corrections, trigger and reconstruction efficiencies was estimated to be less than 1% and was added in quadrature to the statistical errorsData have been corrected for qed radiative effects up to order alpha**3 (F.A.Berends, R.Kleiss, Nucl.Phys.B206(1983)61)//Weak radiative corrections have not yet been provided in a form of a Monte Carlo generator program, but are estimated to be negligible at PETRA energies (M.Bohm, A.Denner, W.Hollik, DESY-86-165)).
Axis error includes +- 1/1 contribution (The overall uncertainty in the bin-to-bin polar acceptance due to shower corrections, trigger and reconstruction efficiencies was estimated to be less than 1% and was added in quadrature to the statistical errorsData have been corrected for qed radiative effects up to order alpha**3 (F.A.Berends, R.Kleiss, Nucl.Phys.B206(1983)61)//Weak radiative corrections have not yet been provided in a form of a Monte Carlo generator program, but are estimated to be negligible at PETRA energies (M.Bohm, A.Denner, W.Hollik, DESY-86-165)).
A study of 205-GeV/c π−p interactions has been made with a 48 800-picture exposure in the bare Fermilab 30-inch hydrogen bubble chamber. The average number of charged particles produced per inelastic interaction is 7.99±0.06. The elastic cross section is 3.18±0.13 mb and the total cross section is 24.19±0.44 mb. The inclusive cross sections for neutral-particle production are: σ(γ)=171.3±15.3 mb, σ(KS0)=3.64±0.61 mb (x<0.3), σ(Λ)=1.71±0.34 mb (x<0.3), and σ(Λ¯)=0.59±0.23 mb (x<0.1). The average number of π0's produced per inelastic collision is consistent with a linear rise with the number of charged particles, and about equal to the number of produced π− or π+. The average number of K0's, Λ's, and Λ¯'s is consistent with very little dependence on the number of charged particles. General characteristics of neutral-particle production are presented and compared with other experiments. For each topology the produced neutral energy is ∼13 of the incident energy.
THE ERRORS INCLUDE THOSE DUE TO VARIOUS CORRECTIONS.
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We have studied the reactionspp→ppπ+π-,K+p→K+pπ+π−π, π+p→ π+,pπ+π− and π−p →π+π− at 147 GeV/c using the 30-inch Fermilab hybrid system. All four reactions were detected with the same apparatus and analyzed in the same way. The energy dependence of the channel cross section was found to beAp−0.6+B for thepp reaction andAp−1+B for the other three. About 90% of the cross section at 147 GeV/c can be accounted for by either beam or target diffraction. Some of the remaining cross section may come from double Pomeron exchange reactions which we tried to isolate. We have tested the hypothesis of a factorizable Pomeron and our data indicates a violation of this hypothesis. We show that the 3π mass enhancement in the mass region 1.2–1.4 GeV is diffractively produced in the π± beam reactions. Fourprong, four-constraint and six-prong, four-constraint cross sections are reported.
CROSS SECTIONS FOR DIFFRACTION DISSOCIATION OF BEAM. FEYNMAN X OF OUTGOING PROTON <-0.96.
CROSS SECTIONS FOR DIFFRACTION DISSOCIATION OF THE TARGET. FEYNMAN X OF THE FASTEST OUTGOING PARTICLE >0.96.
We have measured the total inelastic cross section (σinel) and charged-particle multiplicities obtained in pp collisions at 405 GeV/c. The data are from a preliminary 12 000-picture bubble-chamber exposure. We find σinel=32.8±1.0 mb; the low moments of the multiplicity distribution for negative particles are 〈n−〉=3.50±0.07, D−=2.37±0.05, f2−=2.1±0.2, and f3−=0.1±0.9. We also present updated results at 102 GeV/c.
SUPERCEDES PRELIMINARY RESULTS IN J. W. CHAPMAN ET AL., PRL 29, 1686 (1972).
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FIT TO ELASTIC DIFFERENTIAL CROSS SECTION FOR 0.05 < -T < 0.7 GEV**2.
The Fermilab hybrid 30-in. bubble-chamber spectrometer was exposed to a tagged 147-GeV/c positive beam containing π+, K+, and p. A sample of 3003 K+p, 19410 pp, and 20745 π+p interactions is used to derive σn, 〈n〉, f2cc, and 〈nc〉D for each beam particle. These values are compared to values obtained at other, mostly lower, beam momenta. The overall dependence of 〈n〉 on Ea, the available center-of-mass energy, for these three reactions as well as π−p and pp interactions has been determined.
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