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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.
The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus all pion production channels were recorded with 1-4 overconstraints. The total and differential cross sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the $pp\pi^0$ channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular we observe very large anisotropies for the $\pi^0$ angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with $\pi^0$ $s$- and $d$-partial waves and emphasizing the important role of $\pi^0$ d-waves.
We present preliminary results from a sample of ∼ 1200 events obtained from an exposure of the 30-in. Argonne National Laboratory—National Accelerator Laboratory liquid-hydrogen bubble chamber to 102-GeVc protons. The elastic and total inelastic cross sections are respectively 6.9 ± 1.0 and 32.8 ± 1.1 mb. The parameters of the multiplicity distribution for negative tracks are 〈n−〉=2.17±0.07, D−2=〈n−2〉−〈n−〉2=2.56±0.12, and f2−=D−2−〈n−〉=0.39±0.10.
The differential cross sections for lepton pair production in e+e− annihilation at 29 GeV have been measured and found to be in good agreement with the standard model of the electroweak interaction. With the assumption of e−μ−τ universality, the weak neutral-current couplings are determined to be ga2=0.23±0.05 and gv2=0.03±0.04.
Hadron production and lepton-pair production in e+e- collisions are studied with data collected with the L3 detector at LEP at centre-of-mass energies sqrt{s}=192-208GeV. Using a total integrated luminosity of 453/pb, 36057 hadronic events and 12863 lepton-pair events are selected. The cross sections for hadron production and lepton-pair production are measured for the full sample and for events where no high-energy initial-state-radiation photon is emitted prior to the collisions. Lepton-pair events are further investigated and forward-backward asymmetries are measured. Finally, the differential cross sections for electron-positron pair-production is determined as a function of the scattering angle. An overall good agreement is found with Standard Model predictions.
In a special run of the LHC with $\beta^\star = 2.5~$km, proton-proton elastic-scattering events were recorded at $\sqrt{s} = 13~$TeV with an integrated luminosity of $340~\mu \textrm{b}^{-1}$ using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam $t$ variable in the range from $-t = 2.5 \cdot 10^{-4}~$GeV$^{2}$ to $-t = 0.46~$GeV$^{2}$ using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section $\sigma_{\textrm{tot}}$, parameters of the nuclear slope, and the $\rho$-parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit $t \rightarrow 0$. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the $t$-dependence. The results for $\sigma_{\textrm{tot}}$ and $\rho$ are \begin{equation*} \sigma_{\textrm{tot}}(pp\rightarrow X) = \mbox{104.7} \pm 1.1 \; \mbox{mb} , \; \; \; \rho = \mbox{0.098} \pm 0.011 . \end{equation*} The uncertainty in $\sigma_{\textrm{tot}}$ is dominated by the luminosity measurement, and in $\rho$ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.
We measured the differential cross section for p̄p and pp elastic scattering in the momentum-transfer range 0.01 <| t | < 1.0 GeV 2 at the CERN Intersecting Storage Rings with center-of-mass energy s = 52.8 GeV . Fitting the differential cross section with an exponential [ A exp ( bt )], we found b p p = 13.92 ± 0.59 GeV −2 for | t | < 0.05 GeV 2 , whilst for | t | > 0.09 GeV 2 , b p p = 10.68 ± 0.26 GeV −2 . Using the optical theorem, we obtained for the total cross section σ tot ( p p)= 44.86 ± 0.78 mb and, by integrating the differential cross section, we obtained for the total elastic cross section σ el ( p p) = 7.89 ± 0.28 mb . Calculations of σ tot combining elastic-rate and total-rate measurements are also given. All of these measurements were also performed for pp scattering at the same energy, and the results for both reactions are compared.
We measured the elastic scattering of αα at s = 126 GeV and of α p at s = 89 GeV . For αα , the differential cross section d σ /d t has a diffractive pattern minima at | t | = 0.10 and 0.38 GeV 2 . At small | t | = 0.05−0.07 GeV 2 , this cross section behaves like exp[(100 ± 10) t ]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section α tot ( αα ) = 250 ± 50 mb and an integrated elastic cross section σ e1 ( αα ) = 45 ± mb. Another method of estimating σ tot ( αα ), based on measuring the interaction rate, yielded 295 ± 40 mb. For α p, d σ /d t has aminimum at | t | = 0.20 GeV 2 , and for 0.05 < | t | < 0.18 GeV 2 behaves like exp[(41 ± 2) t ]. Extrapolating this slope to | t | = 0, we found σ tot ( α p) = 130 ± 20 and σ e1 ( α p) = 20 ± 4mb. Results on pp elastic scattering at s = 63 GeV agree with previous ISR experiments.
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