Search for supersymmetric particles in scenarios with a gravitino LSP and stau NLSP

Sleptons, neutralinos and charginos were searched for in the context of scenarios where the lightest supersymmetric particle is the gravitino. It was assumed that the stau is the next-to-lightest supersymmetric particle. Data collected with the DELPHI detector at a centre-of-mass energy near 189 GeV were analysed combining the methods developed in previous searches at lower energies. No evidence for the production of these supersymmetric particles was found. Hence, limits were derived at 95% confidence level.Comment: 31 pages, 14 figure

Measurement of Trilinear Gauge Couplings in e+e−e^+ e^- Collisions at 161 GeV and 172 GeV

Trilinear gauge boson couplings are measured using data taken by DELPHI at 161~GeV and 172~GeV. Values for $WWV$ couplings ($V=Z, \gamma$) are determined from a study of the reactions \eeWW\ and \eeWev, using differential distributions from the $WW$ final state in which one $W$ decays hadronically and the other leptonically, and total cross-section data from other channels. Limits are also derived on neutral $ZV\gamma$ couplings from an analysis of the reaction \eegi

Study of B0_s anti-B0_s oscillations and B0_s lifetimes using hadronic decays of B0_s mesons

Oscillations of B0s mesons have been studied in samples selected from about 3.5 million hadronic Z decays detected by DELPHI between 1992 and 1995. One analysis uses events in the exclusive decay channels: B0s -> Ds- pi+ or Ds- a1+ and B0s -> anti-D0 K- pi+ or anti-D0 K- a1+, where the D decays are completely reconstructed. In addition, B0s anti-B0s oscillations have been studied in events with an exclusively reconstructed Ds accompanied in the same hemisphere by a high momentum hadron of opposite charge. Combining the two analyses, a limit on the mass difference between the physical B0s states has been obtained: Delta(m_B0s) > 4.0 ps^{-1} at the 95% C.L. with a sensitivity of Delta(m_B0s) = 3.2 ps^{-1}. Using the latter sample of events, the B0s lifetime has been measured and an upper limit on the decay width difference between the two physical B0s states has been obtained: tau(B0s) = 1.53^{+0.16}_{-0.15}(stat.) +/- {0.07}(syst.) ps \Delta\Gamma(B0s)/\Gamma(B0s) < 0.69 at the 95% C.L. The combination of these results with those obtained using Ds+- lepton-+ sample gives: Delta(m_B0s) > 4.9 ps^{-1} at the 95% C.L. with a sensitivity of Delta(m_B0s) = 8.7 ps^{-1}. tau(B0s) = 1.46 +/- 0.11 ps and \Delta\Gamma(B0s)/\Gamma(B0s) < 0.45 at the 95% C.L.Comment: 42 pages, 13 figure

Kaon interference in the hadronic decays of the Z

Link to publication Citation for published version (APA): Abreu, P., Agasi, E. E., Boudinov, E., Hao, W., Holthuizen, D. J., Kluit, P. M., ... van Eldik, J. E. (1996). Kaon interference in the hadronic decays of the Z. Physics Letters B, 379, 330. https://doi.org/10.1016/0370-2693(96)00572-2 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. EB ELSEWJER PHYSICS LETTERS B Physics Letters B 379 (1996) [330][331][332][333][334][335][336][337][338][339][340] Kaon interference in the hadronic decays of the Z&quot; Abstract The first measurement of like-sign charged kaon correlations in hadronic decays of the p is presented, based on data collected by the DELPHI detector. The charged kaons are identified by means of ring imaging Cherenkov detectors. A significant enhancement at small values of the four:momentum difference is observed in the ratio of like-sign to unlikesign KK pairs and in the ratio of like-sign pairs to a simulated reference sample. An update of the measurement of KiK:!, interference is also presented. An enhancement is found in the production of pairs of Ki of similar momenta, as compared with a simulated reference sample. The measured Bose-Einstein correlation parameters A and r are similar for charged and neutral kaon pairs. The value of the Bose-Einstein correlation strength A is consistent with unity. &apos; On leave of absence from IHEP Serpukhov

MEASUREMENT OF THE PARTIAL WIDTH OF THE Z0 INTO B(B)OVER-BAR FINAL-STATES USING THEIR SEMILEPTONIC DECAYS

The spectra of prompt electrons and muons from the semi-leptonic decays of heavy hadrons produced in Z0 decays have been used to measure the coupling of the Z0 to b quarks weighted by the B hadrons mean semi-leptonic branching fraction, giving a value: BR(sl)b*GAMMA(bbBAR)/GAMMA(H)=0.0221+/-0.0015. The data has also been used to measure the value of the fragmentation parameter, defined in the context of the LUND PS Model, version 7.2, giving: epsilon(b)=(8(+5/-3)+/-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: X(E)bBAR=0.69(+0.02/-0.03)+/-0.01. If the values of GAMMA(bbBAR) and GAMMA(H) are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction of B hadrons: BR(sl)b=(10.1+/-0.7)%. Taking the value of GAMMA(bbBAR)/GAMMA(H) from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BR(sl)b=(10.1+/-1.3)% is obtained

Charged particle multiplicity distributions for fixed number of jets in Z0 hadronic decays

The multiplicity distributions of charged particles in full phase space and in restricted rapidity intervals for events with a fixed number of jets measured by the DELPHI detector are presented. The data are well reproduced by the Lund Parton Shower model and can also be well described by fitted negative binomial distributions. The properties of these distributions in terms of the clan model are discussed. In symmetric 3-jet events the candidate gluon jet is found not to be significantly different in average multiplicity than the mean of the other two jets, thus supporting previous results of the HRS and OPAL experiments. Similar results hold for events generated according to the LUND PS and to the HERWIG models, when the jets are defined by the JADE jet finding algorithm. The method seems to be insensitive for measuring the color charge ratio between gluons and quarks. © 1992 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

BOSE-EINSTEIN CORRELATIONS IN THE HADRONIC DECAYS OF THE Z(0)

Bose-Einstein correlations between pairs of like-sign charged particles produced in e+e- annihilations near the Z0 peak have been studied using data taken with the DELPHI detector at LEP. An enhancement is found in the production of pairs of identical pions of similar momenta, with respect to a reference sample. Under the hypothesis that the pions are emitted by a spherically symmetrical source with gaussian density, the data indicate a radius of the source of r = 0.62 +/- 0.04(stat.) +/- 0.20(syst.) fm. The large systematic uncertainty reflects the sensitivity of r to the choice of the reference sample

A Study of the decays of tau leptons produced on the Z resonance at LEP

From 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 88.2 GeV an 94.2 GeV, the tau decays tau- --&gt; e-nu(e)nu(tau)BAR, tau- --&gt; mu-nu(mu)nu(tau)BAR, tau- --&gt; pi-(K-)nu(tau), tau- --&gt; rho-nu(tau) and their charge conjugates have been studied. The following branching ratios have been measured; BR (tau- --&gt; e-nu(e)nu(tau)BAR) = 18.6+/-0.8 (stat.)+/-0.6 (sys.)%, BR (tau- --&gt; mu-nu(mu)nu(tau)BAR) = 17.4+/-0.7+/-0.6%, BR (tau- --&gt; pi-(K-)nu(tau)) = 11.9+/-0.7+/-0.7%, BR (tau- --&gt; rho-nu(tau)) = 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, alpha(s)(m(tau)) = 0.26 +0.09/-0.12. Extrapolating the alpha(s) value from m(tau) to m(Z) yields alpha(s)(m(Z)) = 0.109 +0.012/-0.028. The average polarization P(tau) of taus produced in Z --&gt; tau+tau- decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes is P(tau) = -0.24+/-0.07. This value of P(tau) gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of v(tau)/a(tau) = 0.12+/-0.04, and hence a value of the effective electroweak mixing parameter sin2-theta(w)(m(Z)2) = 0.220+/-0.009