Using BEBC equipped with a hydrogen-filled neon-surrounded track-sensitive target, the charged current cross sections and structure functions of hydrogen and neon targets traversed by the same neutrinos and antineutrinos are compared directly. The measured total cross-section ratios between hydrogen and neon allow precise total cross-section values for hydrogen to be inferred. Using this normalization, the ν and ν hydrogen data are combined and the quark distributions in free nucleons, parametrised as functions of ξ, are extracted. This free-nucleon parametrisation is then compared directly with the neon data in order to measure nuclear effects such as those recently reported by the EMC collaboration. Only small effects are seen, in excellent agreement with recent SLAC data in a more similar A and q 2 range.
Measured charged current total cross section.
Measured charged current total cross section.
AVERAGE Q**2 IS 6.9GEV**2 FOR NU AND 4.3GEV**2 FOR ANU.
The strong coupling constant, αs, has been determined in hadronic decays of theZ0 resonance, using measurements of seven observables relating to global event shapes, energy correlatio
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
The value of the strong coupling constant,$$\alpha _s (M_{Z^0 } )$$, is determined from a study of 15 d
Differential jet mass distribution for the heavier jet using method T. The data are corrected for the finite acceptance and resolution of the detector and for initial state photon radiation.
Differential jet mass distribution for the jet mass difference using methodT. The data are corrected for the finite acceptance and resolution of the detec tor and for initial state photon radiation.
Differential jet mass distribution for the heavier jet using method M. The data are corrected for the finite acceptance and resolution of the detector and for initial state photon radiation.
A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D0,D+ andD*+ are reconstructed in the modesK−π+,K−π+K+ andD0π+ followed byD0→K−π+, respectively. The fractional decay widths\(\Gamma {{(Z^0\to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0\to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern-\nulldelimiterspace} {\Gamma _h }}\) are determined, and first results are presented for the production ofD mesons from\(c\bar c\) and\(b\bar b\) events separately. The average energy fraction ofD*± in charm quark fragmentation is found to be 〈XE(D*)〉c=0.487±0.015 (stat)±0.005 (sys.). Assuming that the fraction ofDs and charm-baryons produced at LEP is similar to that around 10 GeV, theZ0 partial width into charm quark pairs is determined to beΓc/Γh=0.187±0.031 (stat)±0.023 (sys). The probability for ab quark to fragment into\(\bar B_s \) orb-baryons is inferred to be 0.268±0.094 (stat)±0.100 (sys) from the measured probability that it fragments into a\(\bar B^0 \) orB−.
Using full data sample.
Using full data sample with proper time > 1 ps to enrich (b bbar) content.
Data with Delta(L) > 1.
We have measured the photon yield in lepton pair events recorded by the OPAL detector in a data sample corresponding to an integrated luminosity of 7.1 pb −1 at centre-of-mass energies between 88 GeV and 94 GeV. The results are compared to QED expectations for initial and final state photon radiation. No anomalous photon yield has been found, and stringent limits on the branching ratio for exotic radiative three body Z 0 decays into a photon and a pair of leptons are obtained. We also place limits on possible Z 0 decays into a photon and a resonance X with subsequent decays of X into a pair of leptons. Acollinear μ + μ − events with missing momentum along the beam direction are identified as events with hard initial state photon radiation and used to measure an average cross section of 15 ± 8 6 pb for e + e − annihilation into μ + μ − , in the so far untested range of centre-of-mass energies between 60 GeV and 84 GeV. This value is consistent with a cross section of 24 pb, expected from Z 0 and photon exchange.
No description provided.
No description provided.
Low x domain.
An improved measurement of the average b hadron lifetime is performed using a sample of 1.5 million hadronic Z decays, collected during the 1991–1993 runs of ALEPH, with the silicon vertex detector fully operational. This uses the three-dimensional impact parameter distribution of lepton tracks coming from semileptonic b decays and yields an average b hadron lifetime of 1.533 ± 0.013 ± 0.022 ps.
No description provided.
We have identified 262 doubly tagged two-photon events. A subset of the data shows an enhancement of 21 events in the inclusive two-photon mass squared distribution between 0.8 and 2.2 GeV 2 . If these events result from spin 2 resonance production then Γ γγ = 9.5 ± 3.9 ± 2.4 keV (statistical and systematic). From another subset of 58 events in which the final state could be classified we determine the two-photon hadron to muon cross section ratio R γγ = 1.1 ± 0.3 ± 0.3.
ELECTRON BEAM ENERGIES OF 3.0 AND 3.6 GEV.
This paper describes an analysis of sub-jet multiplicities, which are expected to be sensitive to the properties of soft gluon radiation, in hadronic decays of theZ0. Two- and three-jet event samples are selected using thek⊥ jet clustering algorithm at a jet resolution scaley1. The mean sub-jet multiplicity as a function of the sub-jet resolution,y0, is determined separately for both event samples by reapplying the same jet algorithm at resolution scalesy0<y1. These measurements are compared with recent perturbative QCD calculations based on the summation of leading and next-to-leading logarithms, and with QCD Monte Carlo models. The analytic calculations provide a good description of the sub-jet multiplicity seen in three- and two-jet mvents in the perturbative region (y0≈y1)), and the measured form of the data is in agreement with the expectation based on coherence of soft gluon radiation. The analysis provides good discrimination between Monte Carlo models, and those with a coherent parton shower are preferred by the data. The analysis suggests that coherence effects are present in the data.
Ratio of multiplicities of sub-jets from 3 and 2 jet samples. Data are corrected to the hadron level and have combined statistical and systematic errors.
Sub-jet multiplicity for 3 jet sample. Data corrected to the hadron level and have combined statistical and systematic errors.
Sub-jet multiplicity for 2 jet sample. Data corrected to the hadron level and have combined statistical and systematic errors.
We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.
No description provided.
No description provided.
No description provided.
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