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)

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)

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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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.

Searches for pair production of gauginos and squarks in e(+)e(-) collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 pb(-1) collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of R-parity through a single dominant (U) over bar(D) over bar(D) over bar coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95% CL were obtained from these searches: neutralino mass: m(<()over tilde>1)(0) greater than or equal to 32 GeV; chargino mass: m(<()over tilde>1)(+) greater than or equal to 94 GeV; stop and sboctom mass (indirect decay) with DeltaM > 5 GeV: m((t) over tilde1) greater than or equal to 74 GeV for Phi (mix) = 0 rad, m((t) over tilde1) greater than or equal to 59 GeV for Phi (mix) = 0.98 rad, m((b) over tilde1) greater than or equal to 72 GeV for Phi (mix) = 0 rad. The angle phi (mix) is the mixing angle between left and right handed quarks. (C) 2001 Elsevier Science B.V. All rights reserved.

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 bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(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.

A test of the QED process e(+)e(-) --> gamma gamma>(*) over bar *(gamma) is reported. The data analysed were collected with the DELPHI detector in 1998 and 1999 at the highest energies achieved at LEP, reaching 202 GeV in the centre-of-mass. The total integrated luminosity amounts to 375.7 pb(-1). The differential and total cross-sections for the process e(+)e(-) --> gamma gamma were measured, and found to be in agreement with the QED prediction. 95% confidence level (C.L.) lower limits on the QED cut-off parameters of Lambda (+) > 330 GeV and Lambda_ > 320 GeV were derived. A 95% C.L. lower bound on the mass of an excited electron of 311 GeV/c(2) (for lambda gamma = 1) was obtained, s-channel virtual graviton exchange was searched for, resulting in 95% C.L. lower limits on the string mass scale, M-S: M-S > 713 GeV/c(2) (lambda = 1) and M-S > 691 GeV/c(2) (lambda = -1). (C) 2000 Published by Elsevier Science B.V.

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 (µ,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 β ≥ 1.

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.

Searches for charginos, neutralinos and sleptons at LEP2 centre-of-mass energies from 130 GeV to 189 GeV have been used to set lower limits on the mass of the Lightest Supersymmetric Particle and other supersymmetric particles within the MSSM framework. R-parity conservation has been assumed. The lightest neutralino was found to be heavier than 32.3 GeV/c independent of the m0 value. The lightest chargino, the second-to-lightest neutralino, the next-toheaviest neutralino, the heaviest neutralino, the sneutrino and the right-handed selectron were found to be heavier than 62.4 GeV/c, 62.4 GeV/c, 99.9 GeV/c, 116.0 GeV/c, 61.0 GeV/c, and 87.0 GeV/c, respectively. These limits do not depend on m0 or M2 and are valid for 1 ≤ tanβ ≤ 40, in the μ region where the lightest neutralino is the LSP. If the sneutrino Is heavier than the chargino the lightest neutralino has to be heavier than 32.4 GeV/c. The effects of mixings in the third family of sfermions on these limits are discussed. The confidence level of all limits given is 95%. (Accepted by Physics Letters B)