569 research outputs found

    f1_1(1285) Formation in Two-Photon Collisions at LEP

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    The ηπ+π\eta \pi^+ \pi^- final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209~GeV with an integrated luminosity of 664.6~pb1^{-1}. The f1_1(1285) meson is observed and the Q2Q^2 dependence of its production is compared to different form factor models. The γγ\gamma\gamma-coupling parameter Γ~γγ\tilde\Gamma_{\gamma\gamma} is found to be 3.5±0.6(stat.)±0.5(sys.)3.5 \pm 0.6\,(stat.) \pm 0.5\,(sys.)~keV. The branching fraction Γ(f1(1285)a0π)/Γ(f1(1285)ηππ)\Gamma\bigl({\rm f}_1(1285)\rightarrow{\rm a}_0\pi\bigr) / \Gamma\bigl({\rm f}_1(1285)\rightarrow\eta\pi\pi\bigr) is also measured.The ηπ + π − final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb −1 . The f 1 (1285) meson is observed and the Q 2 dependence of its production is compared to different form factor models. The γγ -coupling parameter Γ γγ is found to be 3.5±0.6(stat.)±0.5(sys.) keV. The branching fraction Γ (f 1 (1285)→a 0 π )/ Γ (f 1 (1285)→ ηππ ) is also measured.The eta pi^+ pi^- final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6/pb. The f_1(1285) meson is observed and the Q^2 dependence of its production is compared to different form factor models. The gamma-gamma coupling parameter is found to be 3.5 +/- 0.6(stat.) +/- 0.5(sys.) keV. The branching fraction (f_1(1285) -> a_0 pi) / (f_1(1285) -> eta pi pi) is also measured

    Study of the hadronic photon structure function F2γF^\gamma_2 at LEP

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    The hadronic photon structure function F2γF^\gamma_2 is studied in the reaction e+ee+ehadrons\mathrm{e^+e^-} \rightarrow \mathrm{e^+e^-hadrons} at LEP with the L3 detector. The data, collected from 1991 to 1995 at a centre-of-mass energy \sqrt{s} \simeq 91 \GeV, correspond to an integrated luminosity of 140~pb1^{-1}. The photon structure function F2γF^\gamma_2 is measured in the Q2Q^2 interval 1.2 \GeV^2 \leq Q^2 \leq 9.0 \GeV^2 and the xx interval 0.002<x<0.20.002 < x < 0.2. \FF shows a linear growth with lnQ2\ln Q^2. The value of the slope \alpha^{-1}\mathrm{d}\FF(Q^2)/\mathrm{d}\ln{Q^2} is measured to be 0.079±0.011±0.0090.079 \pm 0.011 \pm 0.009

    The Q(2) evolution of the hadronic photon structure function F-2(gamma) at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

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    New measurements at a centre-of-mass energy root s similar or equal to 183 GeV of the hadronic photon structure function F-2(gamma)(x) in the Q(2) interval, 9 GeV2 less than or equal to Q(2) less than or equal to 30 GeV2, are presented. The data, collected in 1997 with the L3 detector, correspond to an integrated luminosity of 51.9 pb(-1). Combining with the data taken at a centre-of-mass energy of 91 GeV, the evolution of F-2(gamma) With Q(2) is measured in the Q(2) range from 1.2 GeV2 to 30 GeV2. F-2(gamma) shows a linear growth with ln Q(2); the value of the slope alpha(-1)d F-2(gamma)(Q(2))/dlnQ(2) is measured in two x bins from 0.01 to 0.2 and is somewhat higher than predicted. (C) 1999 Published by Elsevier Science B.V. All rights reserved

    Measurement of the photon structure function F-2(gamma) with the L3 detector at LEP

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    The e(+)e(-) -\u3e e(+)e(-)hadrons reaction, where one of the two electrons is detected in a low polar-angle calorimeter, is analysed in order to measure the hadronic photon structure function F-2(gamma) The full high-energy and high-luminosity data set, collected with the U detector at centre-of-mass energies 189 GeV \u3c= root s \u3c= 209 GeV, corresponding to an integrated luminosity of 608 pbis used. The Q(2) range 11 GeV2 \u3c= Q(2) \u3c= 34 GeV2 and the x range 0.006 \u3c= x \u3c= 0.556 are considered. The data are compared with recent parton density functions. (c) 2005 Published by Elsevier B.V

    KS0KS0K^{0}_{S} K^{0}_{S} Final State in Two-Photon Collisions and Implications for Glueballs

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    The \mbox{K}^0_{\rm S}\mbox{K}^0_{\rm S} final state in two-photon collisions is studied with the L3 detector at LEP. The mass spectrum is dominated by the formation of the f2f'_{2}(1525) tensor meson in the helicity-two state with a two-photon width times the branching ratio into KKˉ\rm K\bar{K} of 76±6±11eV76 \pm\, 6 \pm\, 11\, {\rm eV}. A clear signal for the formation of the fJ_{\rm J}(1710) is observed and it is found to be dominated by the spin-two helicity-two state. No resonance is observed in the mass region around 2.2GeV2.2 \,{\rm GeV} and an upper limit of 1.4eV1.4 \,{\rm eV} at 95\% C.L. is derived for the two-photon width times the branching ratio into \mbox{K}^0_{\rm S}\mbox{K}^0_{\rm S} for the glueball candidate ξ(2230)\xi(2230).The K 0 S K 0 S final state in two-photon collisions is studied with the L3 detector at LEP. The mass spectrum is dominated by the formation of the f ′ 2 (1525) tensor meson in the helicity-two state with a two-photon width times the branching ratio into K K ̄ of 76±6±11 eV. A clear signal for the formation of the f J (1710) is observed and it is found to be dominated by the spin-two helicity-two state. No resonance is observed in the mass region around 2.2 GeV and an upper limit of 1.4 eV at 95% C.L. is derived for the two-photon width times the branching ratio into K 0 S K 0 S for the glueball candidate ξ (2230).The K0s K0s final state in two-photon collisions is studied with the L3 detector at LEP. The mass spectrum is dominated by the formation of the f_2'(1525) tensor meson in the helicity-two state with a two-photon width times the branching ratio into K Kbar of 76 +- 6 +- 11 eV. A clear signal for the formation of the f_J(1710) is observed and it is found to be dominated by the spin-two helicity-two state. No resonance is observed in the mass region around 2.2 GeV and an upper limit of 1.4 eV at 95% C.L. is derived for the two-photon width times the branching ratio into K0s K0s for the glueball candidate xi(2230)

    Inclusive J, ψ\psi' and χc\chi_c Production in Hadronic Z Decays

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    We report on measurements of the inclusive production of J, ψ\psi' and χc\mathrm{\chi_c} mesons in hadronic Z decays, based on 3.2 million hadronic events collected using the L3 detector at LEP. The J and ψ\psi' mesons are reconstructed through their decays into lepton pairs, while the χc\mathrm{\chi_c} mesons are reconstructed via the decay mode χcJ+γ \mathrm{\chi_c} \rightarrow \mathrm{J} + \gamma . The measured branching fractions are: \begin{eqnarray*} \mathrm{Br(Z \rightarrow J + X)} &amp;=&amp; (3.40 \pm 0.23\:(\mathrm {stat.}) \pm 0.27\:(\mathrm {sys.}))\,\times\,10^{-3} \\ \mathrm{Br(Z \rightarrow \psi' + X)} &amp;=&amp; (1.6 \pm 0.5\:(\mathrm {stat.}) \pm 0.3\:(\mathrm {sys.}))\,\times\,10^{-3} \\ \mathrm{Br(Z \rightarrow \chi_{c1} + X)} &amp;=&amp; (2.7 \pm 0.6\:(\mathrm {stat.})\pm 0.5\:(\mathrm {sys.}))\, \times\,10^{-3}. \\ \end{eqnarray*} In the absence of a clear χc2\mathrm{\chi_{c2}} signal, the upper limit at 90\% C.L. is set: \mathrm{ Br(Z \rightarrow \chi_{c2} + X) 3.2\,\times\,10^{-3}}. \end{document

    Heavy quarkonium production in Z decays

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    We report measurements of the inclusive production of heavy quarkonium states in Z\mathrm {Z} decays based on the analysis of 3.6 million hadronic events collected by the L3 detector at LEP. The measurement of inclusive J production and an improved 95%95\% confidence level upper limit on Υ\Upsilon production are presented. In addition, two independent measurements of the ratio, fpf_{\mathrm{p}}, of prompt J mesons to those from B decay are made using two different isolation cuts to separate prompt J mesons from J mesons produced in the decays of b hadrons. The results are: % \begin{eqnarray} \mathrm{Br}(\mathrm{Z} \rightarrow \mathrm{J} + \mathrm{X}) & = & (3.21 \pm 0.21 \; \mathrm{(stat.)} \; ^{+ 0.19}_{- 0.28} \; \mathrm{(sys.)} ) \times 10^{-3} \; , \nonumber \\ \mathrm{Br}(\mathrm {Z} \rightarrow \Upsilon(\mathrm{1S} + X) & & 4.4 \times 10^{-5} \; , \nonumber \\ %% f_{\mathrm{p}} & = & (7.1 \pm 2.1 \; \mathrm{(stat.)} \; \pm 1.2 \; \mathrm{(sys.)} \; ^{+1.5}_{-0.8} \;\mathrm{(theo.)} ) \times 10^{-2} \; . \nonumbe

    Photon structure functions and azimuthal correlations of lepton pairs in tagged γγ\gamma\gamma collisions

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    Measurements of the QED structure of the photon based on the reaction ee to ee gamma /sup (*)/(P/sup 2/) gamma *(Q/sup 2/) to ee mu mu are discussed. This review is an update of the discussion of the results on the QED structure of the photon and covers the published measurements of the photon structure functions F/sub 2//sup gamma /, F/sub A//sup gamma / and F/sub B//sup gamma / and of the differential cross-section d sigma /dx for the exchange of two virtual photons. (10 refs)

    Inclusive J-Production in Z(0) Decays

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    Contains fulltext : 26831___.PDF (Publisher’s version ) (Open Access

    Search for Exclusive B Decays to J and η\eta or π0\pi^{0} with the L3 Detector

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    A search for exclusive decays of \ensuremath{\mathrm{B_d^0}} and \ensuremath{\mathrm{B_s^0}} mesons has been performed in the channels \ensuremath{\mathrm{B_d^0}\rightarrow\mathrm{J}\eta},\,\, \ensuremath{\mathrm{B_s^0}\rightarrow\mathrm{J}\eta},\,\, \ensuremath{\mathrm{B_d^0}\rightarrow\mathrm{J}\pi^0} and \ensuremath{\mathrm{B_s^0}\rightarrow\mathrm{J}\pi^0}. The data sample consisted of more than three and half million hadronic \ensuremath{\mathrm {Z}} decays collected by the L3 experiment at LEP from 1991 through 1995. No candidate events have been observed for any of the modes thus determining upper limits at 90\% confidence level: 3.2×1043.2\times 10^{-4} on \mathrm{Br}(\ensuremath{\mathrm{B_d^0}\ rightarrow\mathrm{J}\pi^0)} and the first experimental limits: \begin{eqnarray*} \mathrm{Br}(\ensuremath{\mathrm{B_d^0}\rightarrow \mathrm{J}\eta}) & < & 1.2\times 10^{-3},\\ \mathrm{Br}(\ensuremath{\m athrm{B_s^0}\rightarrow\mathrm{J}\eta}) & < & 3.8\times 10^{-3},\\ \mathrm{Br}(\ensuremath{\mathrm{B_s^0}\rightarrow\mathrm {J}\pi^0}) & < & 1.2\times 10^{-3}.\\ \end{eqnarray*
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