Publications (163)13.47 Total impact
 Zeitschrift für Physik C 12/1995;
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ABSTRACT: A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z 0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D 0,D + andD *+ are reconstructed in the modesK – G(Z0 ® D \mathord/ \vphantom D [`(D)] [`(D)]X) \mathord \vphantom (Z0 ® D \mathord/ \vphantom D [`(D)] [`(D)]X) Gh Gh \Gamma {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern\nulldelimiterspace} {\Gamma _h }} are determined, and first results are presented for the production ofD mesons from c[`(c)]c\bar c and b[`(b)]b\bar b events separately. The average energy fraction ofD * in charm quark fragmentation is found to be [`(B)]s\bar B_s orbbaryons is inferred to be 0.2680.094 (stat)0.100 (sys) from the measured probability that it fragments into a [`(B)]0\bar B^0 orB –.Zeitschrift für Physik C 11/1993; 59(4):533545.  [Show abstract] [Hide abstract]
ABSTRACT: From the combined data of 1990 and 1991 of the DELPHI experiment at LEP, 13057 4jet events are obtained and used for determining the contribution of the triplegluon vertex. The relevant variables are the generalized Nachtmann Reiter angle CA /CF = 2.12 ±0.35 and NC /NA = 0.46 ±0.19,C_A /C_F = 2.12 \pm 0.35 and N_C /N_A = 0.46 \pm 0.19, whereC A/C F is the ratio of the coupling strength of the triplegluon vertex to that of gluon bremsstrahlung from quarks, andN C/N A, the ratio of the number of quark colours to the number of gluons.This constitutes a convincing modelindependent proof of the existence of the triplegluon vertex, since its contribution is directly proportional toC A/C F. The results are in agreement with the values expected from QCD:C A/C F=2.25, andN C/N A=3/8.Zeitschrift für Physik C 08/1993; 59(3):357368.  [Show abstract] [Hide abstract]
ABSTRACT: Based on a sample equivalent to 365 000 hadronic Z0 decays, the search in DELPHI data for pairs of leptons accompanied by a pair of charged particles is described. A total of 11 events were found in the electron channel, 9 in the muon channel and 7 in the tau channel. Results on lepton pairs with a radiated photon are also presented. The data from all channels are compatible with the expectations from standard processes. However, one event was found in the tau channel with an unusually high mass of the charged particle pair.Nuclear Physics B 07/1993; 403:324. · 4.33 Impact Factor 
Article: A Measurement of the tau lifetime
Physics Letters B 03/1993; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A study ofB meson decays intoDl X final states is presented. In these events, neutral and chargedD mesons originate predominantly fromB + andB 0 decays, respectively. The dilution of this correlation due toD ** production has been taken into account. From 263 700 hadronicZ 0 decays collected in 1991 with the DELPHI detector at the LEP collider, 92D 0[`(B)]0\bar B^0 ) meson is found to be 0.44 0.080.09, corresponding to a total (B s+ XE (B) = 0.695 ±0.015(stat.) ±0.029(syst.)\left\langle {X_E (B)} \right\rangle = 0.695 \pm 0.015(stat.) \pm 0.029(syst.) ReconstructingDlepton vertices, the followingB lifetimes are measured: t(B) = 1.27  0.18 + 0.22 (stat.) ±0.15(syst.)ps, where[`(B)] ® D0 l X, t(B) = 1.18  0.27 + 0.39 (stat.) ±0.15(syst.)ps, where[`(B)] ® D+ l X, t(B) = 1.19  0.19 + 0.25 (stat.) ±0.15(syst.)ps where[`(B)] ® D* + l X, \begin{gathered} \tau (B) = 1.27_{  0.18}^{ + 0.22} (stat.) \pm 0.15(syst.)ps, \hfill \\ where\bar B \to D^0 \ell ^  X, \hfill \\ \tau (B) = 1.18_{  0.27}^{ + 0.39} (stat.) \pm 0.15(syst.)ps, \hfill \\ where\bar B \to D^ + \ell ^  X, \hfill \\ \tau (B) = 1.19_{  0.19}^{ + 0.25} (stat.) \pm 0.15(syst.)ps \hfill \\ where\bar B \to D^{* + } \ell ^  X, \hfill \\ \end{gathered} and an average D**l [`(v)]D**\ell ^  \bar v , theB + andB 0 lifetimes are: t(B+ ) = 1.30  0.29 + 0.33 (stat.) ±0.15(syst.exp.) ±0.05(syst.D**)ps, t(B0 ) = 1.17  0.23 + 0.29 (stat.) ±0.51(syst.exp.) ±0.05(syst.D**)ps, t(B+ )/t(B0 ) = 1.11  0.39 + 0.51 (stat.) ±0.05(syst.exp.) ±0.10(syst.D**)ps. \begin{gathered} \tau (B^ + ) = 1.30_{  0.29}^{ + 0.33} (stat.) \pm 0.15(syst.\exp .) \hfill \\ \pm 0.05(syst.D**)ps, \hfill \\ \tau (B^0 ) = 1.17_{  0.23}^{ + 0.29} (stat.) \pm 0.51(syst.\exp .) \hfill \\ \pm 0.05(syst.D**)ps, \hfill \\ \tau (B^ + )/\tau (B^0 ) = 1.11_{  0.39}^{ + 0.51} (stat.) \pm 0.05(syst.\exp .) \hfill \\ \pm 0.10(syst.D**)ps. \hfill \\ \end{gathered}Zeitschrift für Physik C 01/1993; 57(2):181195.  [Show abstract] [Hide abstract]
ABSTRACT: A new measurement of as (MZ2 ) = 0.123 ±0.006.\alpha _s (M_Z^2 ) = 0.123 \pm 0.006.Zeitschrift für Physik C 01/1993; 59(1):2133.  [Show abstract] [Hide abstract]
ABSTRACT: The decays of Bhadrons have been reconstructed using the charged particles recorded in the DELPHI silicon microstrip detector. The sum of the charges of the secondaries determines the charge of the Bhadron parent. Some 232 114 multihadronic Z0 decays recorded during the 1991 run of LEP at centreofmass energies between 88.2 GeV and 94.2 GeV yield 253 Bhadron candidates with wellmeasured charge. From these the mean lifetimes of neutral and charged Bhadrons are found to be 1.44+/0.21 (stat.)+/0.14(syst.) ps and 1.56+/0.19(stat.)+/0.13(syst.) ps respectively. The ratio of their lifetimes is 1.090.23+0.28 (stat.) +/ 0.11(syst.). Under some assumptions on the abundance and lifetime of the Lambdab0 and Bs0 states, the B0 and B+ lifetimes are inferred.01/1993;  [Show abstract] [Hide abstract]
ABSTRACT: A study of B meson decays into Dl X final states is presented. In these events, neutral and charged D mesons originate predominantly from B + and B 0 decays, respectively. The dilution of this correlation due to D ** production has been taken into account. From 263 700 hadronic Z 0 decays collected in 1991 with the DELPHI detector at the LEP collider, 92 D 0> K pi+, 35 D +> K pi+pi+ and 61 D *0> D 0pi+ followed by D 0> K pi+ or D 0> K pi+pi+pi, are found with an associated lepton of the same charge as the kaon. From the D 0 l  and D *+ l , the probability f d that a b quark hadronizes into a B  (orbar B^0 ) meson is found to be 0.44 ±0.08±0.09, corresponding to a total ( B s+ Lambda b ) hadronization fraction of 0.12{0.12/+0.24}. By reconstructing the energy of each B meson, the b quark fragmentation is directly measured for the first time. The mean value of the B meson energy fraction is: 10052_2005_Article_BF01565048_TeX2GIFE1.gif left< {X_E (B)} rightrangle = 0.695 ± 0.015(stat.) ± 0.029(syst.) Reconstructing Dlepton vertices, the following B lifetimes are measured: 10052_2005_Article_BF01565048_TeX2GIFE2.gif begin{gathered} tau (B) = 1.27_{  0.18}^{ + 0.22} (stat.) ± 0.15(syst.)ps, \ wherebar B to D^0 ell ^  X, \ tau (B) = 1.18_{  0.27}^{ + 0.39} (stat.) ± 0.15(syst.)ps, \ wherebar B to D^ + ell ^  X, \ tau (B) = 1.19_{  0.19}^{ + 0.25} (stat.) ± 0.15(syst.)ps \ wherebar B to D^{* + } ell ^  X, \ and an average tau( B)=1.23{0.13/+0.14}(stat.)±0.15(syst.) ps is found. Allowing for decays intoD**ell ^  bar v, the B + and B 0 lifetimes are: 10052_2005_Article_BF01565048_TeX2GIFE3.gif begin{gathered} tau (B^ + ) = 1.30_{  0.29}^{ + 0.33} (stat.) ± 0.15(syst.exp .) \ ± 0.05(syst.D**)ps, \ tau (B^0 ) = 1.17_{  0.23}^{ + 0.29} (stat.) ± 0.51(syst.exp .) \ ± 0.05(syst.D**)ps, \ tau (B^ + )/tau (B^0 ) = 1.11_{  0.39}^{ + 0.51} (stat.) ± 0.05(syst.exp .) \ ± 0.10(syst.D**)ps. \01/1993;  [Show abstract] [Hide abstract]
ABSTRACT: A new measurement of alphas is obtained from the distributions in thrust, heavy jet mass, energyenergy correlation and two recently introduced jet broadening variables following a method proposed by Catani, Trentadue, Turnock and Webber. This method includes the full calculation of O({s/2}) terms and leading and nexttoleading logarithms resummed to all orders of alphas. The analysis is based on data taken with the DELPHI detector at LEP during 1991. I its found that the inclusion of the resummed leading and nexttoleading logarithms reduces the scale dependence of alphas and allows an extension of the fit range towards the infrared limit of the kinematical range. The combined value for alphas obtained at the scale mu2= M {/Z 2} is: 10052_2005_Article_BF01555835_TeX2GIFE1.gif alpha _s (M_Z^2 ) = 0.123 ± 0.006.01/1993;  01/1993;
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ABSTRACT: The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reactione + e – v1 \mathord/ \vphantom 1 3 32 + a1 \mathord/ \vphantom 1 3 32 = 1.13 ±0.29 and v2 \mathord/ \vphantom 2 3 32 + a2 \mathord/ \vphantom 2 3 32 = 1.65 ±043.v_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern\nulldelimiterspace} 3}}^2 + a_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern\nulldelimiterspace} 3}}^2 = 1.13 \pm 0.29 and v_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern\nulldelimiterspace} 3}}^2 + a_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern\nulldelimiterspace} 3}}^2 = 1.65 \pm 043. No evidence is seen for additional photon production from anomalous decays of theZ 0 or from decays of new particles. This measurement leads to upper limits on the production cross section times branching fraction of (a) the Higgs boson in the reactione + e –Z 0H +,Hhadrons, (b) an excited quark,q *q+, and (c) the contribution of an anomalous decay of theZ 0 into a photon and hadrons. These limits, all at the 95% confidence level, vary from 3 to 10pb as the mass of the intermediate state (H,q * orZ *) varies from 10 GeV/c2 to 80 GeV/c2.Zeitschrift für Physik C 11/1992; 53(4):555565.  [Show abstract] [Hide abstract]
ABSTRACT: 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 t ® e [`(v)]e vt ,t ® m [`(v)]m vt ,t ® p (K )vt ,t ® r vt\tau ^  \to e^  \bar v_e v_\tau ,\tau ^  \to \mu ^  \bar v_\mu v_\tau ,\tau ^  \to \pi ^  (K^  )v_\tau ,\tau ^  \to \rho {}^  v_\tau and their charge conjugates have been studied. The following branching ratios have been measured; BR(t ® e [`(v)]e vt ) = 18.6 ±0.8(stat.) ±0.6(sys.)% ,BR(\tau ^  \to e^  \bar v_e v_\tau ) = 18.6 \pm 0.8(stat.) \pm 0.6(sys.)\% , , BR( t ® m [`(v)]m vt ) = 17.4 ±0.7 ±0.6% ,BR\left( {\tau ^  \to \mu ^  \bar v_\mu v_\tau } \right) = 17.4 \pm 0.7 \pm 0.6\% , , Br(– – (K–)v)=11.90.70.7%, BR (– – v)= 22.40.81.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, s (m) = 0.26 –0.12 +0.09 . Extrapolating the s value fromm tom Z yields s (mZ) = 0.109 –0.028 +0.012 .The average polarizationP of taus produced in Z s s decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes isP =–0.240.07. This value ofP gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of /a = 0.12 0.04, and hence a value of the effective electroweak mixing parameter sin2 W(m Z 2 ).Zeitschrift für Physik C 11/1992; 55(4):555567.  [Show abstract] [Hide abstract]
ABSTRACT: 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 3jet 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.Zeitschrift für Physik C 02/1992; 56(1):6375.  [Show abstract] [Hide abstract]
ABSTRACT: Using a data sample of 115000 hadronicZ 0 decays, a search was performed for the production of excited charged leptons decaying into an ordinary lepton and one photon. Pair production of excited leptons of mass below 45 GeV/c2 is excluded. From an analysis of the leptonphoton mass spectra this experiment is also able to exclude single production of these particles for masses that reach up to 85 GeV/c2, if the compositeness scale is below 1 TeV.Zeitschrift für Physik C 02/1992; 53(1):4149.  Physics Letters B 02/1992; · 4.57 Impact Factor
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ABSTRACT: The average lifetime ofB hadrons produced in hadronicZ 0 decays has been measured with the DELPHI detector at LEP. The measurement is based on the analysis of the impact parameter distributions of highp t muons and hadrons. The resulting meanB lifetimes are Gb[`(b)] \mathord/ \vphantom Gb[`(b)] Gh Gh {{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _h }}} \right. \kern\nulldelimiterspace} {\Gamma _h }} and gave a value of 0.222 –0.031 +0.033 0.017.Zeitschrift für Physik C 01/1992; 53(4):567580. 
Article: Measurement of the partial width of theZ0 intob final states using their semileptonic decays
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ABSTRACT: The spectra of prompt electrons and muons from the semileptonic decays of heavy hadrons produced inZ 0 decays have been used to measure the coupling of theZ 0 tob quarks weighted by theB hadrons mean semileptonic branching fraction, giving a value: BRslb *Gb[`(b)] \mathord/ \vphantom Gb[`(b)] GH GH = 0.0221 ±0.0015BR_{sl}^b *{{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _H }}} \right. \kern\nulldelimiterspace} {\Gamma _H }} = 0.0221 \pm 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: e(b) = ( 8*20c + 5  3 ±2 )10  3 \varepsilon (b) = \left( {8\begin{array}{*{20}c} { + 5} \\ {  3} \\ \end{array} \pm 2} \right)10^{  3} . The corresponding value of the mean fraction of the beam energy taken by aB hadron in the fragmentation of ab quark is: [`(XEb )] = 0.69*20c + 0.02  0.03 ±0.01\overline {X_E^b } = 0.69\begin{array}{*{20}c} { + 0.02} \\ {  0.03} \\ \end{array} \pm 0.01 . If the values of Gb[`(b)]\Gamma _{b\bar b} and Gb[`(b)] \mathord/ \vphantom Gb[`(b)] GH GH {{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _{\rm H} }}} \right. \kern\nulldelimiterspace} {\Gamma _{\rm H} }} from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BR sl b =(10.11.3)% is obtained.Zeitschrift für Physik C 01/1992; 56(1):4761.  [Show abstract] [Hide abstract]
ABSTRACT: The study of the orientation of threejet events from e+e > Z0 > multihadrons is presented, in particular the polar angle distributions of the thrust axis and of the normal to the threejet plane, and the azimuthal correlations between the hadron plane and the one defined by the beam and thrust axes. The data are compared with results at lower energy and with QCD predictions. Good agreement with QCD predictions is observed. The scalar gluon theory is excluded by the data.01/1992;  [Show abstract] [Hide abstract]
ABSTRACT: The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reactione+e?Z0?hadrons+?, as measured in the DELPHI detector at the CERN LEP collider. When combined with the measurement of the total hadronic width of theZ0, the observed rate determines the electroweak coupling constants of up and down type quarks, i.e., $$v_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern\nulldelimiterspace} 3}}^2 + a_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern\nulldelimiterspace} 3}}^2 = 1.13 \pm 0.29 and v_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern\nulldelimiterspace} 3}}^2 + a_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern\nulldelimiterspace} 3}}^2 = 1.65 \pm 043.$$ No evidence is seen for additional photon production from anomalous decays of theZ0 or from decays of new particles. This measurement leads to upper limits on the production cross section times branching fraction of (a) the Higgs boson in the reactione+e?Z0?H +?,H?hadrons, (b) an excited quark,q*?q+?, and (c) the contribution of an anomalous decay of theZ0 into a photon and hadrons. These limits, all at the 95% confidence level, vary from 3 to 10pb as the mass of the intermediate state (H,q* orZ*) varies from 10 GeV/c2 to 80 GeV/c2.01/1992;
Publication Stats
177  Citations  
13.47  Total Impact Points  
Top Journals
 Zeitschrift für Physik C (14)
 Physics Letters B (2)
 Nuclear Physics B (1)
Institutions

1993

Collège de France
Lutetia Parisorum, ÎledeFrance, France


1991–1993

University of Udine
Udine, Friuli Venezia Giulia, Italy
