We present a study of the inclusive ω and η′ production based on 3.1 million hadronic Z decays recorded with the L3 detector at LEP during 1991–1994. The production rates per hadronic Z decay have been measured to be 1.17±0.17 ω mesons and 0.25±0.04 η′ mesons. The production rates and the differential cross sections have been compared with predictions of the JETSET and the HERWIG Monte Carlo models. We have observed that the differential cross sections can be described by an analytical quantum chromodynamics calculation.
Final production rates per hadronic Z0 decay.
Corrected production rates from the omega --> pi+ pi- p0 decay mode. Extrapolation to full x range.
Corrected production rates from the etaprime --> pi+ pi- eta decay mode. Extrapolation to full x range.
Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, we have determined the ratio of branching fractions: $R_{\gamma} \equiv \Gamma(\Upsilon(1S) \rightarrow \gamma gg)/\Gamma(\Upsilon(1S) \rightarrow ggg) = (2.75 \pm 0.04(stat.) \pm 0.15(syst.))%$. From this ratio, we have determined the QCD scale parameter $\Lambda_{\overline{MS}}$ (defined in the modified minimal subtraction scheme) to be $\Lambda_{\overline{MS}}= 233 \pm 11 \pm 59$ MeV, from which we determine a value for the strong coupling constant $\alpha_{s}(M_{\Upsilon(1S)}) = 0.163 \pm 0.002 \pm 0.014$, or $\alpha_{s}(M_{Z}) = 0.110 \pm 0.001 \pm 0.007$.
The ALPHAS at MZ is extrapolation from M(UPSI).
We have searched for excited states of charged and neutral leptons, e ∗ , μ ∗ , τ ∗ and ν ∗ , in e + e − collisions at s =161 GeV using the OPAL detector at LEP. No evidence for their existence was found. With the most common coupling assumptions, the topologies from excited lepton pair production include ℓ + ℓ − γγ and ℓ + ℓ − W + W − , with the subsequent decay of the virtual W bosons. From the analysis of these topologies, 95% confidence level lower mass limits of 79.9 GeV for e ∗ , 80.0 GeV for μ ∗ , 79.1 GeV for τ ∗ , 78.3 GeV for ν e ∗ , 78.9 GeV for ν μ ∗ and 76.2 GeV for ν τ ∗ are inferred. From the analysis of W + W − and γγ topologies with missing energy and using alternative coupling assingments which favour charged ℓ ∗± and photonic ν ∗ decays, 95% confidence level lower mass limits of 77.1 GeV for each ℓ ∗± flavour and 77.8 GeV for each ν ∗ flavour are inferred. From the analysis of the ℓ + ℓ − γ , ℓ ± W ∓ and single γ final states expected from excited lepton single production, upper limits on the ratio of the coupling to the compositeness scale, f Λ , are determined for excited lepton masses up to the kinematic limit.
95 pct upper limits for pair production of the excited leptons.
The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energy W is studied using low Q~2 < 0.01 GeV~2 e~+p interactions collected by the H1 experiment at HERA. The value of the largest transverse momentum of a charged particle in the photon fragmentation region is used to define the hard scale. The slope of the $W$ dependence of the cross section is observed to increase steeply with increasing transverse momentum. The result is compared to measurements of the Q~2 evolution of the W dependence of the virtual photon-proton cross section. Interpretations in terms of QCD and in terms of Regge phenomenology are discussed.
The gamma p cross section is parameterized as CONST*(W**2)**POWER.
Transverse momentum spectra of charged particles produced in deep inelastic scattering are measured as a function of the kinematic variables x_B and Q2 using the H1 detector at the ep collider HERA. The data are compared to different parton emission models, either with or without ordering of the emissions in transverse momentum. The data provide evidence for a relatively large amount of parton radiation between the current and the remnant systems.
Charged particle PT distribution in the pseudorapidity interval 1.5 to 2.5.
Charged particle PT distribution in the pseudorapidity interval 1.5 to 2.5.
Charged particle PT distribution in the pseudorapidity interval 1.5 to 2.5.
We have studied azimuthal correlations in singly-tagged e+e− → e+e−μ+μ− events at an average Q2 of 5.2 GeV2. The data were taken with the OPAL detector at LEP at e+e− centre-of-mass energies close to the Z0 mass, with an integrated luminosity of approximately 100 pb−1. The azimuthal correlations are used to extract the ratio $F_{B}^{αmma}/F_{2}^{αmma}$ of the QED structure functions $F_{B}^{αmma}(x,Q^{2})$ and $F_{2}^{αmma}(x,Q^{2})$ of the photon. In leading order and neglecting the muon mass $F_{B}^{αmma}$ is expected to be identical to the longitudinal structure function $F_{L}^{αmma}$. The measurement of $F_{B}^{αmma}/F_{2}^{αmma}$ is found to be significantly different from zero and to be consistent with the QED prediction.
No description provided.
This letter describes the first observation of W boson pair production at a centre-of-mass energy s =161 GeV in the OPAL detector at LEP. The analysis is sensitive to all expected W + W − decay channels. A total of 28 events have been selected for an integrated luminosity of 9.89±0.06 pb −1 . This is consistent with the Standard Model expectation, including signal and background contributions. The W pair production cross-section is measured to be σ WW = 3.62 −0.82 +0.93 ±0.16 pb. An analysis of the predicted M W dependence of the accepted cross-section, taking into account interference in the four-fermion production processes, yields M W = 80.40 −0.41−0.10 +0.44+0.09 ±0.10 GeV, where the first and second uncertainties are statistical and systematic, respectively, and the third arises form the beam energy uncertainty.
No description provided.
Using data recorded by the CLEO-II detector at CESR, we report evidence of a pair of excited charmed baryons, one decaying into Λc+π+ and the other into Λc+π−. The doubly charged state has a measured mass difference M(Λc+π+)−M(Λc+) of 234.5±1.1±0.8 MeV/c2 and a width of 17.9−3.2+3.8±4.0MeV/c2, and the neutral state has a measured mass difference M(Λc+π−)−M(Λc+) of 232.6±1.0±0.8 MeV/c2 and a width of 13.0−3.0+3.7±4.0MeV/c2. We interpret these data as evidence of the Σc*++ and Σc*0, the spin 32+ excitations of the Σc baryons.
CONST(NAME=EPS) is the parameter of the Peterson fragmentation function (C.Peterson et al., PR D27, 105 (1983)) D(N)/D(Z) = FD(Z) = const * (1/Z)*1/(1- (1/Z)-CONST(NAME=EPS)/(1-Z))**2.
The inclusive one- and two-jet production cross-sections are measured in collisions of quasi-real photons radiated from the LEP beams at e+e− centre-of-mass energies \(\sqrt{s}_{\rm ee}=130\) and 136 GeV using the OPAL detector at LEP. Hard jets are reconstructed using a cone jet finding algorithm. The differential jet cross-sections \({\rm d}\sigma /{\rm d}E_{T}^{\rm jet}\) are compared to next-to-leading order perturbative QCD calculations. Transverse energy flows in jets are studied separately for direct and resolved two-photon events.
Inclusive one-jet cross section.
One-jet rapidity distribution.
Inclusive two-jet cross section.
The differential cross section $d\sigma/dt$ for elastic $\rho~0$ photoproduction, $\gamma p \rightarrow \rho~0 p (\rho~0 \rightarrow \pi~+ \pi~-)$, has been measured in $ep$ interactions at HERA. The squared four-momentum exchanged at the proton vertex, $t$, has been determined directly by measuring the momentum of the scattered proton using the ZEUS Leading Proton Spectrometer (LPS), a large scale system of silicon micro-strip detectors operating close to the HERA proton beam. The LPS allows the measurement of the momentum of high energy protons scattered at small angles with accuracies of 0.4% for the longitudinal momentum and 5 MeV for the transverse momentum. Photoproduction of $\rho~0$ mesons has been investigated in the interval $0.073< |t| <0.40 GeV~2$, for photon virtualities $Q~2<1 GeV~2$ and photon-proton centre-of-mass energies $W$ between 50 and 100 GeV. In the measured range, the $t$ distribution exhibits an exponential shape with a slope parameter $b = 9.8 \pm 0.8 (stat.) \pm 1.1 (syst.) GeV~{-2}$. The use of the LPS eliminates the contamination from events with diffractive dissociation of the proton into low mass states.
SLOPE OF THE DSIG/DT distribution.
Total cross section integrated over t region.
Additional cross section, SIG, not given in the paper.
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