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    29 research outputs found

    A study of bb production in e+e− collisions at s=130 –207 GeV

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    Measurements are presented of R b, the ratio of the bb cross-section to the qq cross-section in e+e− collisions, and the forward-backward asymmetry A FBb at twelve energy points in the range s=130 –207 GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions. Deceased
    Archivio istituzionale della ricerca - Politecnico di Milano
    Archivio istituzionale della ricerca - Università degli Studi di Udine
    Repositorio Institucional de la Universidad de Oviedo
    Warwick Research Archives Portal Repository
    Archivio istituzionale della ricerca - Università di Genova
    Archivio istituzionale della ricerca - Università di Padova
    Archivio istituzionale della ricerca - Università di Trieste
    AIR Universita degli studi di Milano
    Oxford University Research Archive
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    HAL
    Revistas Científicas de Filo (Facultad de Filosofía y Letras, UBA - Universidad de Buenos Aires)
    Hal - Université Grenoble Alpes
    Università degli Studi di Napoli Federico Il Open Archive
    The Egyptian Cardiothoracic Surgeon (ECTS - E-Journal)
    DI-fusion
    The University of Manchester - Institutional Repository
    HAL-CEA
    Hal-Diderot
    Lund University Publications
    Archivio della ricerca - Università degli studi di Napoli Federico II
    HAL-IN2P3
    Crossref
    Springer - Publisher Connector
    DSpace@NTUA (National Technical Univ. of Athens)
    HAL-OBSPM
    CERN Document Server
    HAL Portal UDL Université de Lyon
    Swepub

    Lifetime and production rate of beauty baryons from Z decays

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    The production and decay of beauty baryons (b-baryons) have been studied using 1.7 \times 10^6 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a \Lambda and a lepton to tag the b-baryon decay. The second method associated fully reconstructed \Lambda_c baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured: \begin{eqnarray*} f(\qb \ra \Bb) \times \BR(\Bb \ra \mLs \ell\bar{\nu}_{\ell}\X) & = & (0.30 \pm 0.06 \pm0.04)\% , \\ f(\qb \ra \Bb) \times \BR(\Bb \ra \mLc \ell\bar{\nu}_{\ell}\X) & = & (1.18 \pm 0.26^{+0.31}_{-0.21})\% , \\ f(\qb \ra \Bb) \times \BR(\Bb \ra \prot\mu\bar{\nu}_{\mu}\X) & = & (0.49\pm0.11\pm^{+0.15}_{ -0.11})\% . \end{eqnarray*} The average b-baryon lifetime was determined to be:\par \vspace{0.4cm} \centerline {\tau = 1.21 ^{+.21}_{-.18}(stat.)\pm0.04(exp.syst.) ^{+.02}_{-.07}(th.syst.) ps.
    Hal - Université Grenoble Alpes
    HAL AMU
    Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura
    The University of Manchester - Institutional Repository
    Archivio istituzionale della ricerca - Università di Genova
    Hal-Diderot
    Archivio istituzionale della ricerca - Università di Padova
    Archivio istituzionale della ricerca - Università di Trieste
    HAL-IN2P3
    Crossref
    Portail HAL du Collège de France
    Oxford University Research Archive
    DSpace@NTUA (National Technical Univ. of Athens)
    DIAL UCLouvain
    CERN Document Server
    HAL
    HAL Portal UDL Université de Lyon

    A precise measurement of the partial decay width ratio R-b(0) = Gamma(b(b)over-bar)/Gamma(had)

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    The partial decay width of the Z to \bb quark pairs has beenmeasured by the DELPHI detector at LEP using data taken in the years1992 to 1995.Decays of b-hadrons were tagged by several methods usingtracks with large impact parameters and/or reconstructed secondary vertices, complemented by event shape variables.Combining these methods in a multivariate analysis the value\frac{\Gamma({\mathrm Z \rightarrow \bb}) }{ \Gamma({\mathrm {Z \rightarrow had}}) } = 0.21634 \pm 0.00067({\mathrm {stat}}) \pm 0.00060 ({\mathrm {syst}})was obtained, where the ccˉ{\mathrm c} \bar {\mathrm c} production fractionwas fixed to its Standard Model value
    Hal - Université Grenoble Alpes
    HAL AMU
    Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura
    Archivio istituzionale della ricerca - Università di Genova
    Hal-Diderot
    International Migration, Integration and Social Cohesion online publications
    Archivio istituzionale della ricerca - Università di Padova
    HAL-IN2P3
    Portail HAL du Collège de France
    DSpace@NTUA (National Technical Univ. of Athens)
    HAL
    HAL Portal UDL Université de Lyon

    Measurement of A(FB)(b anti-b) in hadronic Z decays using a jet charge technique

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    The \BB forward-backward asymmetry %, \AFBbb, has been determined from the average charge flow %, ⟨QFB⟩\langle Q_{FB}\rangle, measured in a sample of 3,500,000 hadronic Z decays collected with the DELPHI detector in 1992 - 1995. The measurement is performed in an enriched \BB sample selected using an impact parameter tag and results in the following values for the \BB forward-backward asymmetry: \begin {center} \begin{tabular}{ccl} \AFBbb (89.55 GeV) & = & 0.068\,\ \pm0.018\,\ (\mbox{stat.})\pm0.0013 (\mbox{syst.}) \\ \AFBbb (91.26 GeV) & = & 0.0982\pm0.0047(\mbox{stat.})\pm0.0016(\mbox{syst.}) \\ \AFBbb (92.94 GeV) & = & 0.123\,\ \pm0.016\,\ (\mbox{stat.})\pm0.0027(\mbox{ syst.}) \\ \end{tabular} \end{center} %at an average center of mass energy of 91.251\, GeV . % The \BB charge separation %, \db, required for this analysis is directly measured in the b tagged sample, while the other charge separations %, \ddusc, are obtained from a fragmentation model precisely calibrated to data. % The effective weak mixing angle %, \sweff, is deduced from the measurement to be: \begin {center} \begin{tabular}{ccl} \sweff & =& 0.23186±0.00083 0.23186\pm0.00083 \end{tabular} \end{center
    Hal - Université Grenoble Alpes
    HAL AMU
    Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura
    ePubs: the open archive for STFC research publications
    The University of Manchester - Institutional Repository
    Archivio istituzionale della ricerca - Università di Genova
    Hal-Diderot
    Archivio istituzionale della ricerca - Università di Padova
    HAL-IN2P3
    Portail HAL du Collège de France
    DSpace@NTUA (National Technical Univ. of Athens)
    CERN Document Server
    HAL
    HAL Portal UDL Université de Lyon

    Measurement of the rate of b anti-b b anti-b events in hadronic Z decays and the extraction of the gluon splitting into b anti-b

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    The rate Z→bb‾bb‾Z \rightarrow b\overline{b}b\overline{b} was measured using about 2x1062 x 10^6 hadronic decays collected by the DELPHI experiment in 1994 and 1995. Events were forced into 3-jets with ymin>0.06y_{min} > 0.06 and a b-tag was required for every jet. The rate was measured to be: R4b=BR(Z→bb‾bb‾)/BR(Z→hadrons)=(6.0+−1.9(stat)+−1.4(syst.))x10−4R_{4b} = BR(Z \to b\overline{b}b\overline{b}) / BR(Z \to hadrons) = (6.0 +- 1.9(stat) +- 1.4(syst.)) x 10^{-4} where the invariant mass of every bb‾b\overline{b} system is above twice the b quark mass. Using the value of R4bR_{4b} the probability of secondary production of a bb‾b\overline{b} pair from a gluon per hadronic ZZ decay, gbbg_{bb}, was extracted and found to be: gbb=(3.3+−1.0(stat.)+−0.8(syst.))x10−3g_{bb} = (3.3+-1.0(stat.) +- 0.8(syst.)) x 10^{-3}
    Archivio istituzionale della ricerca - Università degli Studi di Udine
    Hal - Université Grenoble Alpes
    HAL AMU
    Archivio istituzionale della ricerca - Università dell'Insubria
    ePubs: the open archive for STFC research publications
    The University of Manchester - Institutional Repository
    Archivio istituzionale della ricerca - Università di Genova
    Hal-Diderot
    International Migration, Integration and Social Cohesion online publications
    Archivio istituzionale della ricerca - Università di Padova
    Archivio istituzionale della ricerca - Università di Trieste
    Archivio della ricerca - Università degli studi di Napoli Federico II
    HAL-IN2P3
    Crossref
    Copenhagen University Research Information System
    Portail HAL du Collège de France
    Oxford University Research Archive
    DSpace@NTUA (National Technical Univ. of Athens)
    DIAL UCLouvain
    CERN Document Server
    HAL

    Measurement of inclusive π0 production in hadronic Z0 decays

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    An analysis is presented of inclusive π0 production in Z0 decays measured with the DELPHI detector. At low energies, π0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to {Mathematical expression}) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy for qq and bb events. The number of π0's per hadronic Z0 event is N(π0)/Zhad0 =9.2±0.2(stat)±1.0(syst) and for bb events the number of π0's is N(π0)/bb=10.1±0.4(stat)±1.1(syst). The ratio of the number of π0's in bb events to hadronic Z0 events is less affected by the systematic errors and is found to be 1.09±0.05±0.01. The measured π0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in the ξp=ln(1/xp) distribution is ξ*p =3.90-0.14+0.24 . The average number of π0's from the decay of primary B hadrons is found to be N(B→π0 X)/B hadron=2.78±0.15(stat)±0.60(syst). © 1996 Springer-Verlag
    Pergamos : Unified Institutional Repository / Digital Library Platform of the National and Kapodistrian University of Athens

    Measurement of inclusive π 0 production in hadronic Z 0 decays

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    An analysis is presented of inclusive π 0 production in Z 0 decays measured with the DELPHI detector. At low energies, π 0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to {Mathematical expression}) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy for qq and bb events. The number of π 0's per hadronic Z 0 event is N(π 0)/Z had 0 =9.2±0.2(stat)±1.0(syst) and for bb events the number of π 0's is N(π 0)/bb=10.1±0.4(stat)±1.1(syst). The ratio of the number of π 0's in bb events to hadronic Z 0 events is less affected by the systematic errors and is found to be 1.09±0.05±0.01. The measured π 0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in the ξ p=ln(1/xp) distribution is ξ* p =3.90 -0.14 +0.24 . The average number of π 0's from the decay of primary B hadrons is found to be N(B→π 0 X)/B hadron=2.78±0.15(stat)±0.60(syst). © 1996 Springer-Verlag
    Crossref
    DSpace@NTUA (National Technical Univ. of Athens)

    A precise measurement of the partial decay width ratio Rb0=Γbb‾/ΓhadR_{b}^{0} = \Gamma_{b\overline{b}}/\Gamma_{had}

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    The partial decay width of the Z to \bb quark pairs has beenmeasured by the DELPHI detector at LEP using data taken in the years1992 to 1995.Decays of b-hadrons were tagged by several methods usingtracks with large impact parameters and/or reconstructed secondary vertices, complemented by event shape variables.Combining these methods in a multivariate analysis the value\frac{\Gamma({\mathrm Z \rightarrow \bb}) }{ \Gamma({\mathrm {Z \rightarrow had}}) } = 0.21634 \pm 0.00067({\mathrm {stat}}) \pm 0.00060 ({\mathrm {syst}})was obtained, where the ccˉ{\mathrm c} \bar {\mathrm c} production fractionwas fixed to its Standard Model value
    CERN Document Server

    Measurement of the rate of b(b)over-bar-b(b)over-bar events in hadronic Z decays and the extraction of the gluon splitting into b(b)over-bar

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    The rate Z –> b (b) over bar b (b) over bar was measured using about 2 x 10(6) hadronic decays collected by the DELPHI experiment in 1994 and 1995. Events were forced into 3-jets with y(min) > 0.06 and a b-tag was required for every jet. The rate was measured to be: R-4b = BR(Z –> b (b) over bar b (b) over bar/BR(Z –> hadrons), = (6.0 +/- 1.9(stat.) +/- 1.4(syst.)) x 10(-4) where the invariant mass of every b (b) over bar system is above twice the b quark mass. Using the value of R-4b the probability of secondary production of a b (b) over bar pair from a gluon per hadronic Z decay, g(bb), was extracted and found to be: g(bb) = (3.3 +/- 1.0(stat.) +/- 0.8(syst.)) x 10(-3). (C) 1999 Published by Elsevier Science B.V. All rights reserved
    Pergamos : Unified Institutional Repository / Digital Library Platform of the National and Kapodistrian University of Athens

    IceCube search for dark matter annihilation in nearby galaxies and galaxy clusters

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    We present the results of a first search for self-annihilating dark matter in nearby galaxies and galaxy clusters using a sample of high-energy neutrinos acquired in 339.8 days of live time during 2009/10 with the IceCube neutrino observatory in its 59-string configuration. The targets of interest include the Virgo and Coma galaxy clusters, the Andromeda galaxy, and several dwarf galaxies. We obtain upper limits on the cross section as a function of the weakly interacting massive particle mass between 300 GeV and 100 TeV for the annihilation into bb¯, W+W−, τ+τ−, μ+μ−, and νν¯. A limit derived for the Virgo cluster, when assuming a large effect from subhalos, challenges the weakly interacting massive particle interpretation of a recently observed GeV positron excess in cosmic rays
    Publikationsserver der RWTH Aachen University
    DI-fusion
    espace@Curtin
    Archivio istituzionale della ricerca - Università di Padova
    Archive ouverte UNIGE
    Infoscience - École polytechnique fédérale de Lausanne
    DESY Publication Database
    Crossref
    Adelaide Research & Scholarship
    Ghent University Academic Bibliography
    Oxford University Research Archive
    Acropolis Educational Resources Repository
    Swepub
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