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.

A new precise measurement of |Vcb| and of the branching ratio BR(B̄0 → Dlν̄l) has been performed using a sample of about 5000 semileptonic decays B̄0 → Dlν̄l, selected by the DELPHI detector at LEP I by tagging the soft pion from D → Dπ. The results are: Vcb = (39.0 ± 1.5 (stat.) +2.5 −2.6 (syst. exp.) ± 1.3 (syst. th.)) × 10 BR(B̄0 → Dlν̄l) = (4.70 ± 0.13 (stat.) +0.36 −0.31 (syst. exp.))% The analytic dependences of the differential cross-section and of the Isgur Wise form factor as functions of the variable w = vB0 · vD∗ have also been obtained by unfolding the experimental resolution. (Accepted by Phys.Lett.B)

Distributions of event shape variables obtained from 120600 hadronic Z decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant c~ s are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, c% (Mz) = 0.113 +_ 0.007, is based on second order perturbation theory and uses two hadronization corrections, one computed with a pat ton shower model and the other with a QCD matrix element model.

A measurement of the strange quark forwardbackward asymmetry at the Z ~ peak was performed using 718,000 multihadronic Z ~ decays collected by the DELPHI detector at LEP in 1992. The s q u a r k was tagged by the presence of high momentum charged kaons identified by the Ring Imaging Cherenkov detector and by A~ decaying into pro-. The s q u a r k purity obtained was estimated for the two hadrons to be 43%. The average s q u a r k asymmetry was found to be 0.131 4, 0.035 (star.) 4. 0.013 (s~ls~.). The forward-backward asymmetry was measured for unresolved d and s quarks, tagged by the detection of a high energy neutron or neutral kaon in the Hadron Calorimeter. The combined d and s q u a r k purity was 69% and their asymmetry was found to be 0.112 40.031 (star.) 40.054 (syst.).

An analysis of inclusive production of K ~ and the meson resonances K*+(892), p~ f0(975) and f2(1270) in hadronic decays of the Z ~ is presented, based on about 973,000 multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. Overall multiplicities have been determined as 1.962 -40.060 K ~ mesons, 0.712 • 0.067 K*• and 1.21 + 0.15 p~ per hadronic Z ~ decay. The average multiplicities of f0(975) for scaled momentum, xp = P/Pb~a,~, in the range 0.05 _< xp _<0.6 and of f2(1270) for 0.05 _< zp _<1.0 are 0.098 + 0.016 and 0.170 • 0.043 respectively. The fo(975) and p~ zp-spectra have similar shapes. The fz(1270)/p~ ratio increases with zp. The average multiplicities and the differential cross sections are compared with the JETSET Parton Shower model. The model with default parameters fails to reproduce the experimental K ~ momentum spectrum at low momentum, describes the K*• and p~ zp-spectrum shapes, but significantly overestimates their production rates.

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sion 7.2, giving: e (b) = (8 + ~ ___ 2)10 -3. The corresponding value of the mean fraction of the beam energy taken by a B hadron in the fragmentation of a b quark is: + 0 02 X~=0.69 0"03-t-0.01. If the values of F~ and F n are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction of B hadrons" BR~I=(10.1 +0.7)%. Taking the value of Fb~/F n from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BRs~ =(10.1 -+ 1.3)% is obtained. 1 I n t r o d u c t i o n In the Standard Model the Z ~ boson couples with different strengths to up and down type quarks. Experimentally jets produced by heavy quarks are the easiest to isolate because of the use of characteristic properties of heavy hadron production and decay. In the present paper, semi-leptonic decays of B hadrons are used to isolate the Z ~ decays into bb pairs. Studying the distributions of the lepton energy and transverse momentum relative to the jet axis allows one to select this channel. This measurement provides a value for the coupling of the Z ~ to b quarks weighted by the mean semi-leptonic branching fraction of B hadrons. DELPHI has measured previously the fraction of b quarks produced in hadronic events using the distribution of an event shape variable, the boosted sphericity product [1], and also by studying the impact parameter distribution of charged tracks at the level of the beam interaction point [2]. Combining these measurements allows one to give a value for the mean semi-leptonic branching fraction of B hadrons produced in Z ~ decays. The lepton energy distribution is sensitive to the energy distribution of heavy hadrons and a comparison between data and Monte Carlo simulations allows the fragmentation distributions of the b quark to be studied. Leptons coming from the decays of charm particles do not have such distinctive features as leptons from direct B decays and with the present statistics only very crude measurements could be extracted on c g production. For this reason, in the following analysis, it was assumed that the production of c quarks is given by the Standard Model. After a description of the event selection and of the aspects of the apparatus that are relevant for this analysis, measurements obtained with selected data samples enriched in muons and in electrons are presented separately and then combined to get the final results. 2 D a t a a n d d e t e c t o r 2.1 Event selection and apparatus For this analysis, the sample of 120 K hadronic events recorded in DELPHI in 1990, were required to fulfill the following selection criteria: at least 7 reconstructed charged particles with momentum greater than 100 MeV/c; a total charged energy greater than 14% of the centre of mass energy; the thrust axis of the event at more than 32 ~ from the beam axis; the muon chambers had to be operational for the muon analysis; the barrel electromagnetic calorimeter (the HPC) had to be operational for the electron analysis. The resulting samples of about 100 K events were analyzed for the presence of electron and muon candidates. To define the solid angle covered by the detectors the following conventions were used. The z axis was taken along the electron beam direction and the y axis was vertical. Polar coordinates of a point in the transverse (x, y) plane were labeled R and ~. The 0 angle was used to define a direction relative to the z axis. The muon identification relied mainly on the muon chambers, a set of drift chambers providing three dimensional information. In the barrel part of the detector (52~ 0 < 128 ~ there are 3 sets of chambers (see Fig. 1). One set of chambers is located just inside the hadron calorimeter and two sets are just beyond it, with 2 layers I X ' ~ DELPHI InteraCtive Analysis i

Large size small gap chambers (SGC) equipped with gas electron multiplier (GEM) were exposed to a low-energy hadron beam to characterize their hardness to highly ionizing radiations. During the test. rate and effect of discharges induced by highly ionizing particles were studied as a function of the cathode and GEM voltages. We propose an optimization of the voltages to safely operate the detectors at the largest signal-to-noise ratio. In a second test. the ageing properties of the chambers were measured up to a 5 mC/cm integrated charge, induced by an X-ray beam.We conclude from the two measurements on the good reliability and possible improvements of the SG plus GEM Chambers for long term use in a harsh radiation environment. (C) 2002 Elsevier Science B.V. All rights reserved.

Small Gap+GEM Chambers developed for the CMS experiment at the LHC were exposed to a pion beam of 350MeV at the Paul Scherrer Institut to establish their radiation hardness with respect to the operating gain. The long-term stability of the gain (ageing) was then measured using an X-ray beam.

Searches for spontaneous R-parity-violating signals at roots = 183 GeV and roots = 189 GeV have been performed using the 1997 and 1998 DELPHI data, under the assumption of R-parity breaking in the third lepton family. The expected topology for the decay of a pair of charginos into two acoplanar taus plus missing energy was investigated and no evidence for a signal was found. The results were used to derive a limit on the chargino mass and to constrain the allowed domains of the MSSM parameter space. (C) 2001 Elsevier Science B.V. All rights reserved.

Higgs bosons predicted by the fermiophobic scenario within Two Higgs Doublets Models were searched for in the data collected by the DELPHI detector at centre-of-mass energies between 189 GeV and 202 GeV, corresponding to a total integrated luminosity of 380 pb^-1. No signal was found and confidence limits were derived in the framework of possible extensions of the Standard Model Higgs sector.

Measurements of the trilinear gauge boson couplings WWgamma and WWZ are presented using the data taken by DELPHI in 1998 at a centre-of-mass energy of 189 GeV and combined with DELPHI data at 183 GeV. Values are determined for Delta(g_1^Z) and Delta(kappa_gamma), the differences of the WWZ charge coupling and of the WWgamma dipole coupling from their Standard Model values, and for lambda_gamma, the WWgamma quadrupole coupling. A measurement of the magnetic dipole and electric quadrupole moment of the W is extracted from the results for Delta(kappa_gamma) and lambda_gamma. The study uses data from the final states jjlv, jjjj, lX, jjX and gammaX, where j represents a quark jet, l an identified lepton and X missing four-momentum. The observations are consistent with the predictions of the Standard Model.

Searches for the Standard Model Higgs boson have been performed in the data collected by the. DELPHI experiment at LEP in the year 2000 at centre-of-mass energies between 200 and 209 GeV corresponding to a total integrated luminosity of 224 pb(-1). No evidence for a Higgs signal is observed in the kinematically accessible mass range, and a 95% CL lower mass limit of 114.3 GeV/c(2) is set, to be compared with an expected median limit of 113.5 GeV/c(2) for these data. (C) 2001 Elsevier Science B.V. All rights reserved.

The search for sleptons, neutralinos, charginos and sgoldstinos in the context of scenarios where the lightest supersymmetric particle is the gravitino, and the search for heavy stable charged particles in light gravitino scenarios and minimal supersymmetric standard models, is presented. Data collected during 2000 with the DELPHI detector at centre-of-mass energies from around 204 to 208 GeV were analysed and combined with all the data collected from 1995 to 1999 at lower energies. No evidence for the production of these particles was found, therefore preliminary new mass limits for the supersymmetric and the heavy stable charged particles searched for are set.

A new precise measurement of \V-cb\ and of the branching ratio BR(<(Bover bar>(0)--> D(+*)l(-)<()over bar>(l)) has been performed using a sample of about 5000 semileptonic decays (B) over bar (0) --> D(*+)l(-)<()over bar>(l), selected by the DELPHI detector at LEP 1 by tagging the soft pion from D*+ --> D(0)pi (+). The results are: V-cb = (39.0 +/- 1.5 (stat.)(-2.6)(+2.5) (syst. exp.) +/- 1.3(ayst. th.)) x 10(-3). BR((B) over bar0 --> D(*+)l(-)<()over bar>(l)) = (4.70 +/- 0.13(stat.)(-0.31)(+0.36) (syst. exp.))%. The analytic dependencies of the differential cross-section and of the Isgur-Wise form factor as functions of the variable w = v(B)0 . v(D)* have also been obtained by unfolding the experimental resolution. (C) 2001 Published by Elsevier Science B.V.

Measurements of on-shell ZZ production are described, using data collected by DELPHI in 1997 and 1998, at centre-of-mass energies roots = 182.6 GeV and 188.6 GeV, respectively. Results obtained in each of the final states q (q) over barq (q) over bar, mu (+)mu (-) q (q) over bar e(+)e(-)q (q) over bar, nu<()over bar>q (q) over bar, l(+)l(-)l(+)l(-), and nu<()over bar>l(+)l(-) are presented. The measured cross-sections for on-shell ZZ production via the tree-level doubly-resonant graphs (NC02) are: sigma (NC02) (182.6 GeV) = 0.38 +/- 0.18 (stat) +/- 0.04 (syst) pb, sigma (NC02) (188.6 GeV) = 0.60+/-0.13 (stat) +/- 0.07 (syst) pb. They are consistent with the Standard Model expectations of 0.25 and 0.65 pb at each energy. (C) 2001 Published by Elsevier Science B.V.

The cross sections for the production of single charged and neutral intermediate vector bosons were measured using integrated luminosities of 52 pb(-1) and 154 pb(-1) collected by the experiment at centre-of-mass energies of 182.6 GeV and 188.6 GeV, respectively. The cross sections for the reactions were determined in limited kinematic regions. The results found are in agreement with the Standard Model predictions for these channels. (C) 2001 Published by Elsevier Science B.V.

A new precise measurement of |Vcb| and of the branching ratio BR(B̄0→D∗+ℓ−ν̄ℓ) has been performed using a sample of about 5000 semileptonic decays B̄0→D∗+ℓ−ν̄ℓ, selected by the DELPHI detector at LEP I by tagging the soft pion from D∗+→D0π+. The results are: Vcb=(39.0±1.5(stat.)+2.5−2.6(syst. exp.)±1.3(syst. th.))×10−3, BR(B̄0→D∗+ℓ−ν̄ℓ)=(4.70±0.13(stat.)+0.36−0.31(syst. exp.))%. The analytic dependencies of the differential cross-section and of the Isgur–Wise form factor as functions of the variable w=vB0·vD∗ have also been obtained by unfolding the experimental resolution.