Tevatron Run II combination of the effective leptonic electroweak mixing angle

Drell-Yan lepton pairs produced in the process pp→â.,"+â.,"-+X through an intermediate γ∗/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin2θefflept using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb-1 of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin2θefflept=0.23148±0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin2θW, or equivalently the W-boson mass MW, using the zfitter software package yields sin2θW=0.22324±0.00033 or equivalently, MW=80.367±0.017 GeV/c2

INCLUSIVE MEASUREMENTS OF THE K+/- AND P/(P)OVER-BAR PRODUCTION IN HADRONIC Z(0) DECAYS

This analysis, based on a sample of 170000 hadronic Z(0) decays, provides a measurement of the K-+/- and p/($) over bar p differential cross sections which is compared to string- and cluster fragmentation models. The total multiplicities for K-+/- and pip per hadronic event were found to be: N-K = 2.26 +/- 0.18 and N-p = 1.07 +/- 0.14. The positions xi* of the maxima of the differential cross sections as a function of xi = In(1/x(p)) for K-+/- and p/($) over bar p were determined to be 2.63 +/- 0.07 and 2.96 +/- 0.16 respectively. A comparison of the xi* values for various identified particles measured at LEP with the prediction of the Modified Leading Logarithm Approximation with Local Parton Hadron Duality model has been performed. The measured xi* position as a function of the hadron mass, after corrections due to particle decays, is in agreement with the model calculation

A search for eta `(c) production in photon-photon fusion at LEP

A search for the production of the eta(c)’ meson, the first radial excitation of the ground state of charmonium eta(c)(2980), in the photon-photon fusion reaction at LEP has been performed using the data collected by the DELPHI detector during 1992-1996. No evidence of eta(c)’ production is found in the mass region 3520-3800 MeV/c(2). An upper limit for the ratio of the two-photon widths of the eta(c)’ and eta(c) is obtained. (C) 1998 Published by Elsevier Science B.V. All rights reserved

OBSERVATION OF ORBITALLY EXCITED B-MESONS

Experimental evidence for the existence of orbitally excited B meson states is presented in an analysis of the B pi and B*pi distribution of Q = m(B**) - m(B(*)) - m(pi) using Z(0) decay data taken with the DELPHI detector at LEP. The mean Q-value of the decays B** –> B(*)pi is measured to be 284 +/-5 (stat.) +/- 15 (syst.) MeV/c(2), and the Gaussian width of the signal is 79 +/- 5 (stat.) +/- 8 (syst) MeV/c(2). This signal can be described as a single resonance of mass m = 5732+/-5 (stat.) +/- 20(syst.) MeV/c(2) and full width Gamma = 145 +/- 28 MeV/c(2). The observed shape is also consistent with the production of several broad and narrow states as predicted by the quark model and partly observed in the D-meson sector. The production rate of B** per b-jet is found to be 0.27 +/- 0.02(stat.) +/- 0.06 (syst.)

Search for neutral Higgs bosons in e(+)e(-) collisions at root s=183 GeV

Neutral Higgs bosons were searched for in the data collected by DELPHI at a centre-of-mass energy of 183 GeV, corresponding to an integrated luminosity of 54 pb(-1). The production of the lightest neutral Higgs boson with either an on-shell Z boson or a neutral pseudo-scalar Higgs boson was analysed. Lower limits at the 95% confidence level were obtained on the Higgs boson masses. The limits are 85.7 GeV/c(2) for the Standard Model Higgs boson and 74.4 GeV/c(2) for the scalar and 75.3 GeV/c(2) for the pseudo-scalar Higgs bosons as predicted by the minimal super-symmetric extension of the Standard Model with commonly used assumptions on the model parameters, plus the assumption that the mass of the pseudo-scalar boson is greater than 20 GeV/c(2). These results significantly improve the limits reached with previous data

Lambda(b) polarization in Z(0) decays at LEP

The longitudinal polarization of the Lambda(b) baryon is measured at the LEP e(+)e(-) collider by DELPHI. It is determined from the charged lepton and neutrino energy spectra in 249 +/- 19 Lambda(b) semileptonic decays reconstructed in approximate to 3.5 million hadronic Z(0) decays using Lambda(0)-lepton correlations. The measured polarization is: P-Lambda b = -0.49(-0.30)(+0.32)(stat.) +/- 0.17(syst.). (C) Elsevier Science B.V. All rights reserved

Search for scalar fermions and long-lived scalar leptons at centre-of-mass energies of 130 GeV to 172 GeV

Data taken by DELPHI during the 1995 and 1996 LEP runs have been used to search for the supersymmetric partners of electron, muon and tau leptons and of top and bottom quarks. The observations are in agreement with standard model predictions. Limits are set on sfermion masses. Searches for long lived scalar leptons from low scale supersymmetry breaking models exclude stau masses below 55 GeV/c(2) at the 95% confidence level, irrespective of the gravitino mass

Two-particle angular correlations in e(+)e(-) interactions compared with QCD predictions

Two-particle angular correlations in jet cones have been measured in e(+)e(-) annihilation into hadrons at LEP energies (root s = 91 and 183 GeV) and are compared with QCD predictions using the LPHD hypothesis. Two different functions have been tested. While the differentially normalized correlation function shows substantial deviations from the predictions, a globally normalized correlation function agrees well. The size of alpha(s)(eff) land other QCD parameters) and its running with the relevant angular scale, the validity of LPHD, and problems due to non-perturbative effects are discussed critically. (C) 1998 Elsevier Science B.V. All rights reserved

Study of the four-jet anomaly observed at LEP centre-of-mass energies of 130 and 136 GeV

The four-jet events collected by DELPHI during the special LEP run at centre-of-mass energies of 130 and 136 GeV in 1997 with an integrated luminosity of 5.9 pb(-1) are analysed. Their rate and the distributions of their di-jet masses, their smallest jet charges, and their di-jet charge separations all agree well with Standard Model predictions. Thus the hypothesis of pair production of a new particle with a sum of di-jet masses around 105 GeV/c(2) is not supported. The combined result of the four LEP collaborations refuting this hypothesis at over 99% confidence level is also given. (C) 1999 Published by Elsevier Science B.V. All rights reserved

Measurements of the leptonic branching fractions of the tau

Data collected with the DELPHI detector from 1993 to 1995 combined with previous DELPHI results for data from 1991 and 1992 yield the branching fractions B(tau –> e nu<(nu)over bar>) = (17.877 +/- 0.109(stat) +/- 0.110(sys))% and B(tau –> mu nu<(nu)over bar>) = (17.325 +/- 0.095(stat) +/- 0.077(sys))%