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.
The measured total cross section. The systematic uncertainty includes experimental and theoretical uncerainties.
The measured total cross section. The systematic uncertainty includes experimental and theoretical uncerainties.
The rho-parameter, i.e. the ratio of the real to imaginary part of the elastic scattering amplitude extrapolated to t=0. The systematic uncertainty includes experimental and theoretical uncerainties.
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The cross section of the process e+e-\to\mu+\mu- was measured in the SND experiment at the VEPP-2M e+e- collider in the energy region \sqrt{s}=980, 1040 -- 1380 MeV. The event numbers of the process e+e-\to\mu+\mu- were normalized to the integrated luminosity measured using e+e-\to e+e- and e+e-\to\gamma\gamma processes. The ratio of the measured cross section to the theoretically predicted value is 1.006\pm 0.007 \pm 0.016 and 1.005 \pm 0.007 \pm 0.018 in the first and second case respectively. Using results of the measurements, the electromagnetic running coupling constant \alpha in the energy region \sqrt{s}=1040 -- 1380 MeV was obtained <1/\alpha> = 134.1\pm 0.5 \pm 1.2 and this is in agreement with theoretical expectation.
The E+ E- --> MU+ MU- cross section obtained using the (GAMMA GAMMA) luminosity measurement.
The measured E+ E- --> E+ E- cross section in the electron angle 30 to 150 degrees.
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.
Measured hadron cross section for the inclusive data sample.
Measured hadron cross section for the high-energy data sample.
Measured MU+ MU- cross section for the inclusive data sample.
Compton scattering of quasi-real virtual photons, gamma e+- -> gamma e+-, is studied with 0.6fb-1 of data collected by the L3 detector at the LEP e+e- collider at centre-of-mass energies root(s')=189-209GeV. About 4500 events produced by the interaction of virtual photons emitted by e+- of one beam with e-+ of the opposite beam are collected for effective centre-of-mass energies of the photon-electron and photon-positron systems in the range from root(s')= 35GeV up to root(s')=175GeV, the highest energy at which Compton scattering was ever probed. The cross sections of the gamma e+- -> gamma e+- process as a function of root(s') and of the rest-frame scattering angle are measured, combined with previous L3 measurements down to root(s')~20GeV, and found to agree with the QED expectations.
Measured Compton scattering cross section as a function of the effective centre of mass of the photon-electron system. THETA(RF=CM) is the electron rest frame scattering angle.
The measured angular distribution over the photon-electron centre of mass energy range 35 to 175 GeV.
The measured Compton scattering cross section using the full data sample including the lower energy data from Acciarri et al. PL B439(1998)183. Errors are combined statistics and systematics.
Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The measurements are used to determine the electromagnetic coupling constant alphaem at LEP2 energies. In addition, the results are used together with OPAL measurements at 91-183 GeV within the S-matrix formalism to determine the gamma-Z interference term and to make an almost model-independent measurement of the Z mass. Limits on extensions to the Standard Model described by effective four-fermion contact interactions or the addition of a heavy Z boson are also presented.
CM energy values.
Measured cross section for QUARK QUARKBAR (HADRON) production. The data are corrected to no interference between initial and final state radiation.
Measured cross section for MU+ MU- production. The data are corrected to no interference between initial and final state radiation.
This final analysis of hadronic and leptonic cross-sections and of leptonic forward-backward asymmetries in e+e- collisions with the OPAL detector makes use of the full LEP1 data sample comprising 161 pb^-1 of integrated luminosity and 4.5 x 10^6 selected Z decays. An interpretation of the data in terms of contributions from pure Z exchange and from Z-gamma interference allows the parameters of the Z resonance to be determined in a model-independent way. Our results are in good agreement with lepton universality and consistent with the vector and axial-vector couplings predicted in the Standard Model. A fit to the complete dataset yields the fundamental Z resonance parameters: mZ = 91.1852 +- 0.0030 GeV, GZ = 2.4948 +- 0.0041 GeV, s0h = 41.501 +- 0.055 nb, Rl = 20.823 +- 0.044, and Afb0l = 0.0145 +- 0.0017. Transforming these parameters gives a measurement of the ratio between the decay width into invisible particles and the width to a single species of charged lepton, Ginv/Gl = 5.942 +- 0.027. Attributing the entire invisible width to neutrino decays and assuming the Standard Model couplings for neutrinos, this translates into a measurement of the effective number of light neutrino species, N_nu = 2.984 +- 0.013. Interpreting the data within the context of the Standard Model allows the mass of the top quark, mt = 162 +29-16 GeV, to be determined through its influence on radiative corrections. Alternatively, utilising the direct external measurement of mt as an additional constraint leads to a measurement of the strong coupling constant and the mass of the Higgs boson: alfa_s(mZ) = 0.127 +- 0.005 and mH = 390 +750-280 GeV.
The cross section for hadron production corrected to the simple kinematic acceptance region defined by SPRIME/S > 0.01. Statistical errors only are shown. Also given is the cross section value corrected for the beam energy spread to correspond to the physical cross section at the central value of SQRT(S).
The cross section for E+ E- production corrected to the simple kinematic acceptance region defined by ABS(COS(THETA(C=E-))) < 0.7 and THETA(C=ACOL) < 10 degrees. Statistical errors only are shown. Also given is the cross section value corrected for the beam energy spread to correspond to the physical cross sectionat the central value of SQRT(S).
The cross section for mu+ mu- production corrected to the simple kinematic acceptance region defined by N = M(P=3_4)**2/S > 0.01. Statistical errors only are shown. Also given is the cross section value corrected for the beam energy spread to correspond to the physical cross section at the central value of SQRT(S).
We report on measurements of e+e- annihilation into hadrons and lepton pairs. The data have been collected with the L3 detector at LEP at centre-of-mass energies between 130 and 189 GeV. Using a total integrated luminosity of 243.7 pb^-1, 25864 hadronic and 8573 lepton-pair events are selected for the measurement of cross sections and leptonic forward-backward asymmetries. The results are in good agreement with Standard Model predictions.
Measured cross sections for the hadronic events.
Measured cross sections for the muon-pair events.
Measured cross sections for the tau-pair events.
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