The cross section for the reaction p¯N→μ+μ−X with muon pairs in the mass range 4<M<9 GeV/c2 and xF>0 was measured to be σ=0.104±0.005±0.008 nb/nucleon. The distributions dσdxF and M3dσdM were compared to the QCD-improved Drell-Yan model and to calculations including first-order QCD corrections, with use of deep-inelastic structure functions. Excellent agreement with the data was obtained if the calculations were multiplied by factors of 2.45 and 1.41, respectively.
No description provided.
The hadronic production of charmed states was studied in a two-arm spectrometer using a 205-GeV/c negative-pion beam incident upon a beryllium target. One arm, filled with dense absorber, triggered the detectors upon the passage of a muon with a moderate transverse momentum and a total momentum of at least 4 GeV/c. The other arm was an open-geometry magnetic spectrometer which had both neutral- and charged-particle identification capabilities. The apparatus, the data, and an invariant-mass-plot search for evidence of charmed-meson production through several charged-particle decay modes are described. The Kπ, Kππ, and Kπππ mass plots fail to reveal significant D-meson signals. Based upon the Kπ mass plots, the 95%-confidence upper limit on the DD¯ production cross section is found to be less than 51 μb per nucleon for the production models tested. A search for evidence of charged-D* production yields 30±16 combinations above background in association with the expected trigger muon charge. Interpreted as a D* signal, this excess corresponds to a model-dependent inclusive DD¯ production cross section of 34±18−9+14 μb per nucleon. Model-dependent upper limits on the ratio of the F to D cross sections are also presented.
Uncorrelated model for charmed mesons production.
'Correlated' model for pair of charmed mesons production.
Uncorrelated model for D/S+- mesons production.
The ratio R of the cross section for e+e− annihilation into hadronic final states to the QED cross section for muon-pair production is measured to be 4.34±0.45±0.30 and 4.23±0.20±0.21 at c.m. energies of 50 and 52 GeV, respectively. From these values of R and an analysis of the event shapes we deduce a 95%-confidence-level upper limit for the production rate of new heavy charge +23e or −13e quarks to be 0.19 units of R.
No description provided.
The production of the Jψ resonance in 125-GeV/c p¯ and φ− interactions with Be, Cu, and W targets has been measured. The cross section per nucleon for Jψ production is suppressed in W interactions relative to the lighter targets, especially at large values of Feynman x, which is opposite to the expectation from the various explanations of the European Muon Collaboration effect. Models incorporating modifications of the gluon structure functions in heavy targets show qualitative agreement with the data.
No description provided.
No description provided.
No description provided.
We have studied muon pairs with an invariant mass between 4 and 9 GeV/c2 produced in p¯N and π−N interactions at an incident momentum of 125 GeV/c. The experiment was performed at Fermilab using a tungsten target and a special beam enriched to contain 18% antiprotons. We compare differential distributions as functions of the dimuon invariant mass, Feynman x, transverse momentum, and decay angles of the dimuon to the predictions of the Drell-Yan model including QCD corrections. Quark structure functions for the p¯ and π− are extracted. Comparisons of the antiproton data to the Drell-Yan model are significant because the cross sections depend principally on the valence-quark structure functions which are accurately determined by deep-inelastic scattering measurements. The measured absolute cross section (integrated over positive Feynman x and all transverse momenta) is 0.106±0.005±0.008 nb/nucleon for the p¯N interaction and 0.107±0.003±0.009 nb/nucleon for the π−N interaction, where the quoted errors are statistical and systematic, respectively. Normalization (K) factors that are required to bring the naive Drell-Yan and first-order QCD predictions into agreement with the measurements are extracted, and the uncertainties involved in such comparisons are examined.
No description provided.
No description provided.
No description provided.
A search for pair production of fourth-generation sequential leptons in e+e− annihilation at a center-of-mass energy s=56 GeV is reported. Event topologies corresponding to the cases where one particle decays leptonically while the other decays hadronically as well as those where both particles decay hadronically were explored. We set a 95%-confidence-level lower limit of 27.6 GeV/c2 for the mass of a fourth-generation lepton.
No description provided.
Measurements of the differential cross sections for e + e − →μ + μ − and e + e − →τ + τ − at values of s from 52 to 57 GeV are reported. The forward-backward asymmetries and the total cross sections for these reactions are found to be in agreement with predictions of the standard model of the electro-weak interactions. These measurements are used to extract values of the weak coupling constant g v e g v l and g A e g A l , where l = μ or τ .
Axis error includes +- 5/5 contribution (Included in the quoted errors for the total cross sections. The main contribution to SYS-ERR are the systematic uncertainty in the luminosity measurement and the uncertainty in the computer modeling of the various efficiencies and backgrounds).
Axis error includes +- 5/5 contribution (Included in the quoted errors for the total cross sections. The main contribution to SYS-ERR are the systematic uncertainty in the luminosity measurement and the uncertainty in the computer modeling of the various efficiencies and backgrounds).
No description provided.
The total cross section for e + e − annihilation into hadrons has been measured for CM energies ranging from 50 to 57 GeV. We fit the predictions of the standard model to these measurements and those at lower energies. The mass of the Z 0 boson, M Z , and the QCD scale parameter, Λ MS , are derived from the fit. The results are M Z =88.6 −1.8 +2.0 GeV/ c 2 , and Λ MS =0.15 −0.11 +0.16 GeV .
No description provided.
The inclusive cross section for charged-D* production by 205-GeV/c π− mesons incident on a beryllium target was measured with a two-arm spectrometer triggered by prompt muons. Using the mass-difference technique often employed in D* studies, a signal of 31±11 charged D*’s was isolated; it includes contributions from both the D*+ and D*− charged modes in correlation with triggering muons of the proper charge. This corresponds to an inclusive charged-D* production cross section of 220±77−57+77 μb per Be nucleus or 24±9−6+9 μb per nucleon when the cross section is scaled linearly with atomic mass number. The first error is statistical and the second is systematic.
No description provided.
We present evidence for the non-Abelian nature of QCD from a study of multijet events produced in e+e− annihilations from √s =50 to 57 GeV in the AMY detector at the KEK storage ring TRISTAN. A comparison of the three-jet event fraction at TRISTAN to the fraction of the DESY storage ring PETRA shows that the QCD coupling strength αs decreases with increasing Q2. In addition, measurements of the angular distributions of four-jet events show evidence for the triple-gluon vertex.
No description provided.
No description provided.
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