Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb^{-1} have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay ({\tilde \ell} -> \ell {\tilde \chi_1^0}), producing acoplanar lepton pairs plus missing energy, and the cascade decay ({\tilde \ell} -> \ell {\tilde \chi_2^0} > \ell \gamma {\tilde \chi_1^0}), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are m_{\tilde {e}} \leq 87 GeV/c^2, m_{\tilde {\mu}} \leq 80 GeV/c^2 and m_{\tilde {\tau}} \leq 75 GeV/c^2, respectively, for values of \mu=-200 GeV/c^2 and tan(beta)=1.5.
DELPHI results are presented on the inclusive production of the neutral mesons , f0(980), f2(1270), K 0 2 (1430) and f 0 2(1525) in hadronic Z 0 decays. They are based on about 2 million multihadronic events collected in 1994 and 1995, using the particle identi cation capabilities of the DELPHI Ring Imaging Cherenkov detectors and measured ionization losses in the Time Projection Chamber. The total production rates per hadronic Z decay have been determined to be: 1:19 0:10 for ; 0:164 0:021 for f0(980); 0:214 0:038 for f2(1270); 0:073 0:023 for K 0 2 (1430); and 0:012 0:006 for f 0 2(1525). The total production rates for all mesons and di erential cross-sections for the , f0(980) and f2(1270) are compared with the results of other LEP experiments and with models. (Accepted by Physics Letters B)
F rom the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb -1 taken during the 1990 run of LEP at centre of mass energies between 88.2GeV an 94.2GeV, the tau decays r ~ e g e v T , r -* ,u-~ .v~ , r ~ z c ( K ) v T , r r p v ~ and their charge conjugates have been studied. The following branching ratios have been measured; B R ( r ~ e aTeVT) = 18.6 + 0.8 (stat.) _ 0.6 (sys.)%, BR (z---+ /~17u vT) = 17.4 • 0.7 + 0.6%, B R ( r ~ z c ( K ) v T ) = 11.9_+0.7_ 0.7%, BR ( r > p vT) = 22.4 + 0.8 + 1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, es (mT) = 0.26 + 0.09 Extrapolating the c L value from -0 .12" m T to m z yields cL(mz)=0 .109 +0.012 0.028" The average polarization P~ of taus produced in Z---, r + r decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes is PT = 0.24 _+ 0.07. This value of PT gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of vT/aT=0.12+__O.04, and hence a value of the effective electroweak mixing parameter sin 2 0 w(m~) = 0.220 _ 0.009.
An analysis of the production of the baryon in the hadronic decays of the Z is presented based on about K multihadronic events collected by the DELPHI detector at LEP during and The di erential cross section of the and the correlations between and produced in the same event are compared to current models based both on string fragmentation and on cluster decay The predictions of the string fragmentation model are found to give satisfactory agreements with the data clearly better than those of the cluster model To be submitted to Physics Letters B
The hadronic part of the electron structure function F2e has been measured for the first time, using e+e− data collected by the DELPHI experiment at LEP, at centre-of-mass energies of s=91.2–209.5 GeV. The data analysis is simpler than that of the measurement of the photon structure function. The electron structure function F2e data are compared to predictions of phenomenological models based on the photon structure function. It is shown that the contribution of large target photon virtualities is significant. The data presented can serve as a cross-check of the photon structure function F2γ analyses and help in refining existing parameterisations.
Aad, G.; et al., [Unknown]; Aben, R.; Beemster, L.J.; Bentvelsen, S.; Berglund, E.; Bobbink, G.J.; Bos, K.; Boterenbrood, H.; Colijn, A.P.; de Jong, P.; de Nooij, L.; Deluca, C.; Deviveiros, P.O.; Doxiadis, A.D.; Ferrari, P.; Gadatsch, S.; Geerts, D.A.A.; Gosselink, M.; Hartjes, F.; Hessey, N.P.; Igonkina, O.; Klous, S.; Kluit, P.; Koffeman, E.; Lee, H.; Lenz, T.; Linde, F.; Luijckx, G.; Mahlstedt, J.; Massaro, G.; Mechnich, J.; Mussche, I.; Ottersbach, J.P.; Pani, P.; Ruckstuhl, N.; Ta, D.; Tsiakiris, M.; van der Deijl, P.C.; van der Geer, R.; van der Graaf, H.; van der Leeuw, R.; van der Poel, E.; van Vulpen, I.; Verkerke, W.; Vermeulen, J.C.; Vranjes Milosavljevic, M.; Vreeswijk, M.
: The distributions of event-by-event harmonic flow coefficients v n for n = 2– 4 are measured in √ s NN = 2 . 76 TeV Pb+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using charged particles with transverse momentum p T > 0 . 5 GeV and in the pseudorapidity range | η | < 2 . 5 in a dataset of approximately 7 µ b − 1 recorded in 2010. The shapes of the v n distributions suggest that the associated flow vectors are described by a two-dimensional Gaussian function in central collisions for v 2 and over most of the measured centrality range for v 3 and v 4 . Significant deviations from this function are observed for v 2 in mid-central and peripheral collisions, and a small deviation is observed for v 3 in mid-central collisions. In order to be sensitive to these deviations, it is shown that the commonly used multi-particle cumulants, involving four particles or more, need to be measured with a precision better than a few percent. The v n distributions are also measured independently for charged particles with 0 . 5 < p T < 1 GeV and p T > 1 GeV. When these distributions are rescaled to the same mean values, the adjusted shapes are found to be nearly the same for these two p T ranges. The v n distributions are compared with the eccentricity distributions from two models for the initial collision geometry: a Glauber model and a model that includes corrections to the initial geometry due to gluon saturation effects. Both models fail to describe the experimental data consistently over most of the measured centrality range.
A determ ination ofthesingleW Spin DensityM atrix(SDM )elem entsin thereaction e e ! W + W ! l q q(l= e= )isreported atcentre-of-m assenergies between 189 and 209 GeV.Thedata sam pleused correspondsto an integrated lum inosity of520 pb 1 taken by DELPHIbetween 1998 and 2000. ThesingleW SDM elem ents, W 0 ( ; = 1 or0),aredeterm ined asa function ofthe W production angle with respect to the e beam direction and are obtained from m easurem ents ofthe W decay productsby the application ofsuitableprojection operators, 0,which assum etheV-A coupling oftheW boson to ferm ions. The m easured SDM elem entsare used to obtain the fraction oflongitudinally polarised W s,with theresult: