Publications (47)0 Total impact
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Article: Production of strange B-baryons decaying into Ξ∓−ℓ∓ pairs at LEP
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ABSTRACT: An excess of events containing, in a jet, a samesign t(B - baryon ® X- l- X) = 1.5 - 0.4 + 0.7 ±0.3ps.\tau (B - baryon \to \Xi ^ - \ell ^ - X) = 1.5_{ - 0.4}^{ + 0.7} \pm 0.3ps.Zeitschrift für Physik C 11/1995; 68(4):541-553. -
Article: Measurement of the forward-backward asymmetry ofe+e−→Z→ using prompt leptons and a lifetime tag
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ABSTRACT: The forward-backward asymmetry of the processe + e –b[`(b)]b\bar b has been measured using events collected by the DELPHI experiment during the 1991 and 1992 LEP runs. This data sample corresponded to 884 000 hadronicZ decays at a centre-of-mass energy Ös ~ MZ\sqrt s \sim M_Z . The tagging of b-quark events was performed using two approaches; the first was based on the semileptonic decay channelsbAFBb[`(b)] = 0.107 ±0.011(stat. + syst. + mixing).A_{FB}^{b\bar b} = 0.107 \pm 0.011(stat. + syst. + mixing). With the semileptonic sample, the forward-backward asymmetry of the processe + e –c[`(c)]c\bar c was also measured to be AFBc[`(c)] = 0.083 ±0.022(stat.) ±0.016(syst.).A_{FB}^{c\bar c} = 0.083 \pm 0.022(stat.) \pm 0.016(syst.). The effective value of the Weinberg mixing angle derived from these measurements was sin2 qefflep = 0.2294 ±0.0021.sin^2 \theta _{eff}^{lep} = 0.2294 \pm 0.0021.Zeitschrift für Physik C 11/1995; 65(4):569-585. -
Article: A study of radiative muon-pair events at Z0 energies and limits on an additional Z′ gauge beson
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ABSTRACT: An analysis is reported on the channele + e – - 0.0070 \leqslant qZ¢ \leqslant 0.0078,E6 (c) mod el, - 0.0075 \leqslant qZ¢ \leqslant 0.0095,E6 (y) mod el, - 0.029 \leqslant qZ¢ \leqslant 0.029,E6 (h) mod el, - 0.0068 \leqslant qZ¢ \leqslant 0.0082,L - R(1.) mod el, - 0.0057 \leqslant qZ¢ \leqslant 0.0077,L - R(Ö2 ) mod el. \begin{gathered} - 0.0070 \leqslant \theta _{Z'} \leqslant 0.0078,E_6 (\chi )\bmod el, \hfill \\ - 0.0075 \leqslant \theta _{Z'} \leqslant 0.0095,E_6 (\psi )\bmod el, \hfill \\ - 0.029 \leqslant \theta _{Z'} \leqslant 0.029,E_6 (\eta )\bmod el, \hfill \\ - 0.0068 \leqslant \theta _{Z'} \leqslant 0.0082,L - R(1.)\bmod el, \hfill \\ - 0.0057 \leqslant \theta _{Z'} \leqslant 0.0077,L - R(\sqrt 2 )\bmod el. \hfill \\ \end{gathered}Zeitschrift für Physik C 11/1995; 65(4):603-618. -
Article: Production characteristics of K0 and light meson resonances in hadronic decays of theZ0
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ABSTRACT: An analysis of inclusive production of K0 and the meson resonances K*(892), 0(770),f 0(975) andf 2(1270) in hadronic decays of the Z0 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 1.9620.060 K0 mesons, 0.7120.067 K*(892) and 1.210.150(770) per hadronic Z0 decay. The average multiplicities off 0(975) for scaled momentum,x p , in the range 0.05x p 0.6 and off 2(1270) for 0.05x p 1.0 are 0.0980.016 and 0.1700.043 respectively. Thef 0(975) and 0(770)x p -spectra have similar shapes. Thef 2(1270)/0(770) ratio increases withx p . 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 K0 momentum spectrum at low momentum, describes the K*(892) and 0(770)x p -spectrum shapes, but significantly overestimates their production rates.Zeitschrift für Physik C 11/1995; 65(4):587-602. -
Article: Measurement of theΓ _{bbar b} /Γ _{had} branching ratio of the z by double hemisphere tagging
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ABSTRACT: Two measurements ofΓ _{bbar b} /Γ _{had} are presented. Both measurements use 250000 Z decays taken with the DELPHI detector in 1991 and rely mainly on the precision of the microvertex detector. One tagging method is as simple as possible so that background rates can be reliably predicted by simulation. The other one uses a more involved tagging technique and reduces the dependence on simulation as much as possible. Combining both results,Γ _{bbar b} /Γ _{had} is found to be 0.2209±0.0041( stat.)±0.0042( syst.)±0.0018Γ _{cbar c}.Zeitschrift für Physik C 11/1995; 65:555-568. -
Article: Measurement of using impact parameter measurements and lepton identification
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ABSTRACT: The partial decay width of theZ to b[`(b)]b\bar b quark pairs has been measured by the DELPHI detector at LEP.b-hadrons, containingb-quarks, were tagged by leptons with high transverse momentum relative to the hadron or by tracks with large impact parameters to the primary vertex.The ratio of the numbers of events with a single such tag to those with two tags was used to estimate the efficiency of the method and to reduce the systematic uncertainty. Combining all methods, the value: \fracGb[`(b)] Ghad = 0.2210 ±0.0033 ±0.0003(model) ±0.0014(Gc[`(c)] ) \begin{gathered} \frac{{\Gamma _{b\bar b} }}{{\Gamma _{had} }} = 0.2210 \pm 0.0033 \pm 0.0003(model) \hfill \\ \pm 0.0014(\Gamma _{c\bar c} ) \hfill \\ \end{gathered} was found, where the third error corresponds to a8% uncertainty on the c[`(c)]c\bar c production width. A maximum likelihood in to the single and di-lepton distributions gave the branching fraction of the decays ofb-quarks to leptons as: BR(b ® l) = (11.06 ±0.39 ±0.19(model) ±0.12(Gc[`(c)] ))% . \begin{gathered} BR(b \to l) = (11.06 \pm 0.39 \pm 0.19(model) \hfill \\ \pm 0.12(\Gamma _{c\bar c} ))\% . \hfill \\ \end{gathered}Zeitschrift für Physik C 08/1995; 66(3):323-339. -
Article: Measurement of the forward-backward asymmetry of charm and bottom quarks at theZ pole usingD*± mesons
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ABSTRACT: The forward-backward asymmetries for the processes e+ e- ® c[`(c)]e^ + e^ - \to c\bar c and e+ e- ® b[`(b)]e^ + e^ - \to b\bar b at theZ resonance are measured using identifiedD * mesons. In 905,000 selected hadronic events, taken in 1991 and 1992 with the DEL-PHI detector at LEP, 4757D *+ AFBc[`(c)] = 0.077 ±0.029(stat) ±0.012(sys), AFBb[`(b)] = 0.059 ±0.062(stat) ±0.024(sys). \begin{gathered} A_{FB}^{c\bar c} = 0.077 \pm 0.029(stat) \pm 0.012(sys), \hfill \\ A_{FB}^{b\bar b} = 0.059 \pm 0.062(stat) \pm 0.024(sys). \hfill \\ \end{gathered} Constraining theb asymmetry to the value measured by DELPHI using independent analyses, the charm asymmetry is determined to be: AFBc,const = 0.068 ±0.027(stat) ±0.011(sys).A_{FB}^{c,const} = 0.068 \pm 0.027(stat) \pm 0.011(sys). . This result corresponds to an effective electroweak mixing angle measured using charm quark events of: sin2 qefflept = 0.2307 ±0.0062(stat) ±0.0026(sys).\sin ^2 \theta _{eff}^{lept} = 0.2307 \pm 0.0062(stat) \pm 0.0026(sys).Zeitschrift für Physik C 08/1995; 66(3):341-354. -
Article: Measurements of the τ polarisation in Z0 decays
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ABSTRACT: A sample of Z0ev[`(v)]ev\bar v , mv[`(v)]\mu v\bar v , [`(v)]t /[`(a)]t = 0.074 ±0.011\bar v_\tau /\bar a_\tau = 0.074 \pm 0.011 , and for electrons [`(v)]e /[`(a)]e = 0.068 ±0.014\bar v_e /\bar a_e = 0.068 \pm 0.014 , compatible with e-[`(v)]l /[`(a)]l = 0.072 ±0.008\bar v_l /\bar a_l = 0.072 \pm 0.008 is obtained, implying a value of the effective weak mixing angle sin2 eff lept =0.23200.0021.Zeitschrift für Physik C 05/1995; 67(2):183-201. -
Article: First measurement of the strange quark asymmetry at the Z0 peak
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ABSTRACT: A measurement of the strange quark forward-backward asymmetry at the Z0 peak was performed using 718,000 multihadronic Z0 decays collected by the DELPHI detector at LEP in 1992. Thes-quark was tagged by the presence of high momentum charged kaons identified by the Ring Imaging Cherenkov detector and by 0;s decaying intop–. Thes-quark purity obtained was estimated for the two hadrons to be 43%. The averages-quark asymmetry was found to be 0.1310.035 (stat.) 0.013 (syst.). The forward-backward asymmetry was measured for unresolvedd-ands-quarks, tagged by the detection of a high energy neutron or neutral kaon in the Hadron Calorimeter. The combinedd-ands-quark purity was 69% and their asymmetry was found to be 0.1120.031 (stat.) 0.054 (syst.).Zeitschrift für Physik C 02/1995; 67(1):1-13. -
Article: Search for heavy neutral Higgs bosons in two-doublet models
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ABSTRACT: A search for pair production of neutral heavy Higgs bosons decaying into b[`(b)]b\bar b has been carried out in a study of hadronic decays of the Z boson into four jet final states using data taken by DELPHI in 1991 and 1992. The two production mechanisms present in the two Higgs doublets scheme, bremsstrahlung production of hZ* and associated production of hA, may lead to four beauty jets well recognizable using the precise microvertex detector measurements. No evidence for a signal was found, leading to limits on BR(ZhA4b) from 3.5 to 5.510–4 at 95% contidence level, depending on the mass of the ligthest Higgs. When combined with the results of the recent DELPHI standard Higgs search, this result allows the kinematical limit to be reached for the masses of h and A in the minimal supersymmetric extension of the Standard Model (MSSM) scheme. It also allows the tan1 domain to be explored, and a region above the kinematic limit for direct hA production is constrained by considering virtual hA production. Results are also given in the general two-doublet scheme.Zeitschrift für Physik C 02/1995; 67(1):69-79. -
Article: Measurement of the branching ratio of thez by double hemisphere tagging
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ABSTRACT: Two measurements of Gb[`(b)] /Ghad\Gamma _{b\bar b} /\Gamma _{had} are presented. Both measurements use 250000Z decays taken with the DELPHI detector in 1991 and rely mainly on the precision of the microvertex detector. One tagging method is as simple as possible so that background rates can be reliably predicted by simulation. The other one uses a more involved tagging technique and reduces the dependence on simulation as much as possible. Combining both results, Gb[`(b)] /Ghad\Gamma _{b\bar b} /\Gamma _{had} is found to be 0.22090.0041(stat.)0.0042(syst.)0.0018 Gc[`(c)]\Gamma _{c\bar c} .Zeitschrift für Physik C 01/1995; 65(4):555-568. -
Article: Search for pair-produced heavy scalars in Z0 decays
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ABSTRACT: A search for charged Higgs bosons decaying into quarks is described, based on statistics of around 1.7 million hadronic Zo decays detected in DELPHI. Despite the very high background from standard hadronic decays of the Zo, masses in the range up to 43.5 GeV/c 2 are excluded at the 95% confidence level. After combination with a search for leptonic decays, this mass limit is extended to cover all branching ratios. A similar analysis sets new limits on the possible production of any pair-produced heavy scalar decaying into a pair of jets, such as neutral Higgs bosons in a two doublet scheme and diquarks.Zeitschrift für Physik C 05/1994; 64(2):183-193. -
Article: First evidence of hard scattering processes in single tagged $\gamma\gamma$ collisions
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Article: Production of strange B-baryons decaying into $\Xi^{\mp}$ - l$^{\mp}$ pairs at LEP
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Article: A study of radiative muon-pair events at Z$^{0}$ energies and limits on an additionnal Z' gauge boson
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Article: Search for pair-produced heavy scalars in Z$^0$ decays
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Article: A Study of radiative muon pair events at Z0 energies and limits on an additional Z-prime gauge boson
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Article: Measurement of the forward - backward asymmetry of e+ e- ---> Z ---> b anti-b using prompt leptons and a lifetime tag
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Article: Measurement of the Gamma (b anti-b) / Gamma (hadron) branching ratio of the Z by double hemisphere tagging
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Article: Improved measurements of cross-sections and asymmetries at the Z0 resonance
Top co-authors
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Institutions
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1995
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Università degli studi di Udine
Udine, Friuli Venezia Giulia, Italy
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1994–1995
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Universidade Federal do Rio de Janeiro
Rio de Janeiro, Rio de Janeiro, Brazil
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