A search for signals of new physics has been carried out in the channel p pbar -> gamma gamma + ETmiss. This signature is expected in various recently proposed supersymmetric (SUSY) models. We observe 842 events with two photons having transverse momentum ET(g) > 12 GeV and pseudorapidity |eta(g)| < 1.1. Of these, none have missing transverse energy (ETmiss) in excess of 25 GeV. The distribution of ETmiss is consistent with that of the expected background. We therefore set limits on production cross sections for selectron, sneutrino and neutralino pairs, decaying into photons. The limits range from about 400 fb to 1 pb depending on the sparticle masses. A general limit of 185 fb (95% C.L.) is set on sigma.B(pbar p -> gamma gamma ETmiss + X) where ET(g) > 12 GeV, |eta(g)| < 1.1, and ETmiss > 25 GeV.
$INVISIBLE means ET(missing).
We present the results of a search for third generation leptoquark (LQ) pairs in 110±8pb−1of p¯p collisions at s=1.8TeV recorded by the Collider Detector at Fermilab. We assume third generation leptoquarks decay to a τ lepton and a b quark with branching ratio β. We observe one candidate event, consistent with standard model background expectations. We place upper limits on σ(p¯p→LQLQ¯)̇β2 as a function of the leptoquark mass MLQ. We exclude at 95% confidence level scalar leptoquarks with MLQ<99GeV/c2, gauge vector leptoquarks with MLQ<225GeV/c2, and nongauge vector leptoquarks with MLQ<170GeV/c2 for β=1.
The cross sections times branching ratio. KAPPA is an 'anomalous magnetic moment' (theoretical parameter). See text for details.
The hadronic fragmentation functions of the various quark flavours and of gluons are measured in a study of the inclusive hadron production from Z 0 decays with the DELPHI detector and are compared with the fragmentation functions measured elsewhere at energies between 14 GeV and 91 GeV. A large scaling violation is observed, which is used to extract the strong coupling constant from a fit using a numerical integration of the second order DGLAP evolution equations. The result is α s ( M Z ) = 0.124 −0.007 +0.006 (exp) ± 0.009(theory) where the first error represents the experimental uncertainty and the second error is due to the factorization and renormalization scale dependence.
SIG(Q=BQ, Q=CQ, Q=UDS) corresponds to BQ, CQ, and U,D,S quarks fragmentation into charged hadron.
alpha_s was evaluated from the scaling violation of the fragmentation func tions. The data from other experiments are used for the fitting procedure.
A sample of about 1.4 million hadronic Z decays, selected among the data recorded by the DELPHI detector at LEP during 1994, was used to measure for the first time the momentum spectra of K + , K 0 , p , Λ and their antiparticles in gluon and quark jets. As observed for inclusive charged particles, the production spectra of identified particles were found to be softer in gluon jets than in quark jets, with a higher total multiplicity.
Y events.
Mercedes events.
In a sample of 3.02 million hadronic Z 0 decays collected by the DELPHI detector, 270 J ψ → ℓ + ℓ − candidates have been selected. A search for fully reconstructed B c ± mesons has yielded one B c ± → J ψ π ± candidate, no B c ± → J ψ ℓ ± ν ℓ candidates, and one B c ± → J ψ , π + π − π ± candidate, consistent with expected background in each channel. The following 90% confidence level upper limits are determined: Br(Z 0 → B c ± X) × Br(B c ± → J ψ π ± ) < (1.05 to 0.84) × 10 −4 and Br(Z 0 → B c ± X) × Br(B c ± → J ψ ℓ ± ν ℓ ) < (5.8 to 5.0) × 10 −5 , where the ranges quoted correspond to the range of predicted B c ± lifetimes from 0.4 to 1.4 ps, and Br(Z 0 → B c ± X) × Br(B c ± → J ψ π + π − π ± ) < 1.75 × 10 −4 , constant over the range of predicted B c ± lifetimes.
B/C life-time equals (0.4 to 1.4) ps.
The WA94 experiment uses the production of strange particles and antiparticles to investigate the properties of hot hadronic matter created in heavy-ion interactions. Λ, Λ , Ξ − and Ξ + particle yields and transverse mass spectra are presented for pS interactions. These results are compared with those from SS interactions. Our results are also compared with those from pW and SW interactions of the WA85 experiment.
The fit with formula (1/MT**1.5)*D(SIG)/D(MT) = CONST*EXP(MT/SLOPE).
No description provided.
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Results are presented for F2d/F2p and Rd-Rp from simultaneous measurements of deep inelastic muon scattering on hydrogen and deuterium targets, at 90, 120, 200 and 280 GeV. The difference Rd-Rp, determined in the range 0.002<x<0.4 at an average Q^2 of 5 GeV^2, is compatible with zero. The x and Q^2 dependence of F2d/F2p was measured in the kinematic range 0.001<x<0.8 and 0.1<Q^2<145 GeV^2 with small statistical and systematic errors. For x>0.1 the ratio decreases with Q^2.
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Limits on $\nu_\mu (\overline{\nu}_\mu) \to \nu_e (\overline{\nu}_e)$ oscillations based on a statistical separation of $\nu_e N$ charged current interactions in the CCFR detector at Fermilab are presented. $\nu_e$ interactions are identified by the difference in the longitudinal shower energy deposition pattern of $\nu_e N \rightarrow eX$ versus $\nu_\mu N \to \nu_\mu X$ interactions. Neutrino energies range from 30 to 600 GeV with a mean of 140 GeV, and $\nu_\mu$ flight lengths vary from 0.9 km to 1.4 km. The lowest 90% confidence upper limit in $sin^2 2\alpha$ of $1.1 \times 10^{-3}$ is obtained at $\Delta m^2 \sim 300 eV^2$. For $sin^2 2\alpha = 1$, $\Delta m^2 > 1.6 eV^2$ is excluded, and for $\Delta m^2 \gg 1000 eV^2$, $sin^2 2\alpha > 1.8 \times 10^{-3}$ is excluded. This result is the most stringent limit to date for $\Delta m^2 > 25 eV^2$ and it excludes the high $\Delta m^2$ oscillation region favoured by the LSND experiment. The $\nu_\mu$-to-$\nu_e$ cross-section ratio was measured as a test of $\nu_\mu (\bar\nu_\mu) \leftrightarrow \nu_e (\bar\nu_e)$ universality to be $1.026 \pm 0.055$.
ALPHA is the neutrino mixing angle. The result for SIN(ALPHA)**2 from the fit at each Delta(M)**2 for NUMU -->NUE oscillations. The 90% CL upper limit is equal to the best fit SIN(ALPHA)**2 + 1.2*SIGMA.
No description provided.
We present a new measurement of the left-right cross section asymmetry (ALR) for Z boson production by e+e- collisions. The measurement was performed at a center-of-mass energy of 91.28 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (77.23+-0.52)%. Using a sample of 93,644 Z decays, we measure the pole-value of the asymmetry, ALR0, to be 0.1512+-0.0042(stat.)+-0.0011(syst.) which is equivalent to an effective weak mixing angle of sin**2(theta_eff)=0.23100+-0.00054(stat.)+-0.00014(syst.).
No description provided.
The left-right asymmetry and effective weak mixing angle corrected to the pole energy value, taking into account photon exclusive and electroweak interference effects of total-state radiation.
Deep inelastic electron-photon scattering is studied in the Q2 ranges from 6 to 30 GeV2 and from 60 to 400 GeV2 using the full sample of LEP data taken with the OPAL detector at centre-of-mass energies close to the Z0 mass, with an integrated luminosity of 156.4 pb−1. Energy flow distributions and other properties of the measured hadronic final state are compared with the predictions of Monte Carlo models, including HERWIG and PYTHIA. Sizeable differences are found between the data and the models, especially at low values of the scaling variable x. New measurements are presented of the photon structure function $F_2^{αmma }(x,Q^2)$, allowing for the first time for uncertainties in the description of the final state by different Monte Carlo models. The differences between the data and the models contribute significantly to the systematic errors on $F_2^{αmma }$. The slope ${⤪ d}(F_2^{αmma }/←pha )/{⤪ d ln} Q^2$ is measured to be $0.13_{-0.04}^{+0.06}$.
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