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

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

OBSERVATION OF SHORT-RANGE 3-PARTICLE CORRELATIONS IN E(+)E(-) ANNIHILATIONS AT LEP ENERGIES

Measurements are presented of short range three-particle correlations in e(+)e(-) annihilations at LEP using data collected by the DELPHI detector. At small values of the four-momentum difference, strong three-particle correlations are observed for like-sign (+++ and —) and for unlike-sign (++- and +–) pion combinations which are not a consequence of two-particle correlations. A possible explanation of the observed effects in like-sign combinations is the existence of higher order Bose-Einstein interference, which significantly changes the particle distributions in jets

Rapidity-rank structure of p(p)over-bar pairs in hadronic Z(0) decays

The rapidity-rank structure of pa pairs is used to analyze the mechanism of baryon production in hadronic Z(0) decay. The relative occurrence of the rapidity-ordered configuration p M p, where M is a meson, and that of pp adjacent pairs is compared. The data are found to be consistent with predictions from a mechanism producing adjacent-rank pp pairs, without requiring ‘string-ordered’ p M p configurations. An upper limit of 15% at 90% confidence is determined for the p M p contribution. (C) 2000 Elsevier Science B.V. All rights reserved

Search for charginos in e(+)e(-) interactions at root s=189 GeV

An update of the searches for charginos and gravitinos is presented, based on a data sample corresponding to the 158 pb(-1) recorded by the DELPHI detector in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was found. The lower mass limits are 4-5 GeV/c(2) higher than those obtained at a centre-of-mass energy of 183 GeV. The (mu, M-2) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 31.0 GeV/c(2) for tan beta greater than or equal to 1. (C) 2000 Elsevier Science B.V. All rights reserved

Hadronization properties of b quarks compared to light quarks in e(+)e(-)-> q(q)over-bar from 183 to 200 GeV

The DELPHI detector at LEP has collected 54 pb(-1) of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb(-1) around 189 GeV during 1998, and 187 pb(-1) between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e(+)e(-)->b (b) over bar events: (n)(b (b) over bar), and the difference delta(hl) between (n)(b (b) over bar) and the multiplicity, (n)(l (l) over bar), in generic light quark (u,d,s) events: delta(hl)(183 GeV) = 4.55 +/- 1.31(stat) +/- 0.73(syst), delta(hl)(189 GeV) = 4.43 +/- 0.85(stat) +/- 0.61(syst), delta(hl)(200 GeV) = 3.39 +/- 0.89(stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the: mass of the quark itself. (C) 2000 Elsevier Science B.V. All rights reserved

A precise measurement of the tau lepton lifetime

The tau lepton lifetime has been measured using three different methods with the DELPHI detector. Two measurements of one-prong decays are combined, accounting for correlations, giving a result of tau(tau) = 291.8 +/- 3.3 (stat.) +/- 2.0(sys.) fs while the decay length distribution of three-prong decays gives the result tau(tau) = 286.7 +/- 4.9 (stat.) +/- 3.3 (sys.) fs. Combining the results presented here with previous DELPHI measurements, we get tau(tau) = 291.4 +/- 3.0 fs and find that the ratio of the coupling constant for tau decay relative to that for muon decay is 0.990 +/- 0.009, compatible with lepton universality

Measurement of the (B)over-bar -> D-(*)pi l(nu)over-bar(l) branching fraction

A study of b semileptonic decays into D, D pi(+/-) and D*pi(+/-) final states is presented. The D-0, D+ and D*(+) mesons are exclusively reconstructed in Z decay data recorded from 1992 to 1995 in the DELPHI experiment at LEP. The overall branching fractions are measured to be: BR(b –> D(0)l(-)<(upsilon)over bar>X-l) = (7.04 +/- 0.34(stat) +/- 0.36 (syst.exp) +/- 0.17(BRD))%, BR(b –> D(+)l(-)<(upsilon)over bar>X-l) = (2.72 +/- 0.19(stat) +/- 0.16(syst.exp) +/- 0.18(BRD))%, BR(b –> D*(+)l(-)<(upsilon)over bar>X-l) = (2.75 +/- 0.17(stat) +/- 0.13 (syst.exp) +/- 0.09 (BRD))%, where the D-0 and D+ results include also contributions from D*(0) and D*(+) decays. A fit to the distribution of the pi(+/-) impact parameter to the primary interaction vertex provides a measurement of the b semileptonic branching fractions into the D(0)pi(+/-)X, D(+)pi(+/-)X and D*(+)pi(+/-)X final states. Assuming that single pion decay modes of B mesons dominate, the partial rates for (B) over bar –> D pi l(-)<(upsilon)over bar>(l) and (B) over bar –> D*pi l(-)<(upsilon)over bar>(l) have been obtained, corresponding to a total branching fraction: BR((B) over bar –> D pi l(-)<(upsilon)over bar>(l)) + BR((B) over bar –> D*pi l(-)<(upsilon)over bar>(l)) = (3.40 +/- 0.52 (stat) +/- 0.32 (syst))%. This result agrees well with the observed difference between the total B semileptonic branching fraction and the sum of the (B) over bar –> Dl(-) upsilon(l) and D* l(-)<(upsilon)over bar>(l) branching fractions. (C) 2000 Elsevier Science B.V. All rights reserved