A search for pair–produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at a centre–of–mass energy of 188.6 GeV, corresponding to an integrated luminosity of 176.4 pb−1. Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. The observed events are consistent with the expectations from Standard Model background processes. A lower limit of 65.5 GeV on the charged Higgs mass is derived at 95% confidence level, independent of the decay branching ratio Br(H± → τν). Submitted to Phys. Lett. B

Inclusive production of D * ± mesons in two-photon collisions was measured by the L3 experiment at LEP. The data were collected at a centre-of-mass energy Js = 189 GeV with an integrated luminosity of 176.4 pb 1 2345678. Differential cross sections of the process ee ^ee l)‘ X are determined as functions of the transverse momentum and pseudorapidity of the D* ± mesons in the kinematic region 1 GeV < p'/ < 5GeV and |t|d | < 1.4. The cross section integrated over this phase space domain is measured to be 132 + 22(stat.) + 26(syst.)pb. The differential cross sections are compared with next-to-leading order perturbative QCD calculations. © 1999 Published by Elsevier Science B.V. All rights reserved. 1 Also supported by CONICET and Universidad Nacional de La Plata, CC 67, 1900 La Plata, Argentina. 2 Also supported by Panjab University, Chandigarh-160014, India. 3 Deceased. 4 Also supported by the Hungarian OTKA fund under contract numbers T22238 and T026178. 5 Supported by the German Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie. 6 Supported by the National Natural Science Foundation of China. 7 Supported by the Hungarian OTKA fund under contract num­ bers T019181, F023259 and T024011. 8 Supported also by the Comisión Interministerial de Ciencia y Tecnología.

The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper we present measurements of the isotopic ratios 2H/4He, 3He/4He, 6Li/7Li, 7Be/(9Be+10Be) and 10B/11B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.

Bose–Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Lévy stable distribution in conjunction with a model where a particle’s momentum is correlated with its space–time point of production, the τ-model. Using this description and the measured rapidity and transverse momentum distributions, the space–time evolution of particle emission in two-jet events is reconstructed. However, the elongation of the particle emission region previously observed is not accommodated in the τ-model, and this is investigated using an ad hoc modification.

Following the decision to maintain the International Space Station (ISS) on orbit until at least 2020 (possibly until 2028) the AMS collaboration decided to correspondingly extend the lifetime of the experiment. Since the limited amount of helium used to cool the superconducting magnet allowed for only a limited run time of the experiment, a change from the superconducting magnet to the permanent magnet used in AMS-01 became necessary. Due to the lower magnetic field, to maintain the resolution the silicon tracker also had to be reconfigured with the installation of a silicon plane on the top of the experiment and a new plane above the electromagnetic calorimeter.

We present results from a study of hadronic event structure in high energy e+e− interactions using the L3 detector at LEP. A new class of event shape distributions are measured at and above the Z boson pole for light quark (u, d, s, c) flavours. Energy flow correlations are studied for all hadronic events. Next-to-leading-log QCD calculations and QCD models with improved leading-log approximations are compared to data and good agreement is found at the Z-pole whereas some discrepancies are observed at higher centre-of-mass energies.

Measurement of the chemical and isotopic composition of cosmic rays is essential for the precise understanding of their propagation in the galaxy. While the model parameters are mainly determined using the B/C ratio, the study of extended sets of ratios can provide stronger constraints on the propagation models. In this paper, the relative abundances of light-nuclei lithium, beryllium, boron, and carbon are presented. The secondary-to-primary ratios Li/C, Be/C, and B/C have been measured in the kinetic energy range 0.35–45 GeV nucleon−1. The isotopic ratio 7Li/6Li is also determined in the magnetic rigidity interval 2.5–6.3 GV. The secondary-to-secondary ratios Li/Be, Li/B, and Be/B are also reported. These measurements are based on the data collected by the Alpha Magnetic Spectrometer AMS-01 during the STS-91 space shuttle flight in 1998 June. Our experimental results are in substantial agreement with other measurements, where they exist. We describe our light-nuclei data with a diffusive-reacceleration model. A 10%–15% overproduction of Be is found in the model predictions and can be attributed to uncertainties in the production cross-section data.

The (KSK +/-)-K-0 pi(-/+) final state in two-photon collisions is studied with the L3 detector at LEP at e(+)e(-) centre- of- mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb(-1). The eta (1475) and f(1)(1420) mesons are observed and their contribution is separated by measuring the formation rates as a function of the photon virtuality Q(2). The eta(1475) is found to be dominant for Q(2) <= 0.01 GeV2 and its two- photon width is measured to be 0.23 +/- 0.05 (stat.) +/- 0.05 (sys.) keV. At higher Q(2), the f(1)(1420) is formed and decays to K*(892) K. The coupling and form factor parameters of this state are measured to be Gamma(gamma gamma) = 3.2 +/- 0.6 (stat.) +/- 0.7 ( sys.) keV and Lambda(1) = 926 +/- 72 (stat.) +/- 32 (sys.) MeV, respectively.

M.Aguilar,aa J.Alcaraz,aa J.Allaby,s B.Alpat,ae G.Ambrosi,t,ae H.Anderhub,ai L.Ao,g A.Arefiev,ad P.Azzarello,t E.Babucci,ae L.Baldini,j,l M.Basile,j D.Barancourt,u F.Barao,y,x G.Barbier,u G.Barreira,y R.Battiston,ae R.Becker,lU.Becker,l L.Bellagamba,j P.Béné,t J.Berdugo,aa P.Berges,l B.Bertucci,ae A.Biland,ai S.Bizzaglia,ae S.Blasko,ae G.Boella,ab M.Boschini,ab M.Bourquin,t L.Brocco,j G.Bruni,j M.Buénerd,u J.D.Burger,l W.J.Burger,ae X.D.Cai,l C.Camps,b P.Cannarsa,ai M.Capell,l D.Casadei,j J.Casaus,aa G.Castellini,q,j C.Cecchi,ae Y.H.Chang,m H.F.Chen,v H.S.Chen,i Z.G.Chen,g N.A.Chernoplekov,ac T.H.Chiueh,m K.Cho,p M.J.Choi,aƒ Y.Y.Choi,aƒ Y.L.Chuang,ag F.Cindolo,j V.Commichau,b A.Contin,j E.Cortina-Gil,t M.Cristinziani,t J.P.da Cunha,n T.S.Dai,l C.Delgado,aa J.D.Deus,x N.Dinu,ae,1 L.Djambazov,ai I.D’Antone,j Z.R.Dong,h P.Emonet,t J.Engelberg,w F.J.Eppling,l T.Eronen,ah G.Esposito,ae P.Extermann,t J.Favier,c E.Fiandrini,ae P.H.Fisher,l G.Fluegge,b N.Fouque,c Yu.Galaktionov,ad,l M.Gervasi,ab P.Giusti,j D.Grandi,ab O.Grimm,ai W.Q.Gu,h K.Hangarter,b A.Hasan,ai V.Hermel,c H.Hofer,ai M.A.Huang,ag W.Hungerford,ai M.Ionica,ae,1 R.Ionica,ae,1 M.Jongmanns,ai K.Karlamaa,w W.Karpinski,a G.Kenney,ai J.Kenny,ae D.H.Kim,p G.N.Kim,p K.S.Kim,aƒ M.Y.Kim,aƒ A.Klimentov,l,ad R.Kossakowski,c V.Koutsenko,l,ad M.Kraeber,ai G.Laborie,u T.Laitinen,ah G.Lamanna,ae E.Lanciotti,aa G.Laurenti,j A.Lebedev,l C.Lechanoine-Leluc,t M.W.Lee,p S.C.Lee,ag G.Levi,j P.Levtchenko,ae,2 C.L.Liu,z H.T.Liu,i I.Lopes,n G.Lu,g Y.S.Lu,i K.Lübelsmeyer,a D.Luckey,l W.Lustermann,ai C.Maña,aa A.Margotti,j F.Mayet,u R.R.McNeil,e B.Meillon,u M.Menichelli,ae A.Mihul,k A.Mourao,x A.Mujunen,w F.Palmonari,j A.Papi,ae H.B.Park,p W.H.Park,p M.Pauluzzi,ae F.Pauss,ai E.Perrin,t A.Pesci,j A.Pevsner,d M.Pimenta,y,x V.Plyaskin,ad V.Pojidaev,ad M.Pohl,t V.Postolache,ae,1 N.Produit,t P.G.Rancoita,ab D.Rapin,t F.Raupach,a D.Ren,ai Z.Ren,ag M.Ribordy,t J.P.Richeux,t E.Riihonen,ah J.Ritakari,w S.Ro,p U.Roeser,ai C.Rossin,u R.Sagdeev,o D.Santos,u G.Sartorelli,j C.Sbarra,j S.Schael,a A.Schultz von Dratzig,a G.Schwering,a G.Scolieri,ae E.S.Seo,o J.W.Shin,p E.Shoumilov,ad V.Shoutko,l R.Siedling,a D.Son,p T.Song,h M.Steuer,l G.S.Sun,h H.Suter,ai X.W.Tang,i Samuel C.C.Ting,l S.M.Ting,l M.Tornikoski,w J.Torsti,ah J.Trümper,r J.Ulbricht,ai S.Urpo,w E.Valtonen,ah J.Vandenhirtz,a F.Velcea,ae,1 E.Velikhov,ac B.Verlaat,ai,3 I.Vetlitsky,ad F.Vezzu,u J.P.Vialle,c G.Viertel,ai D.Vité,t H.Von Gunten,ai S.Waldmeier Wicki,ai W.Wallraff,a B.C.Wang,z J.Z.Wang,g Y.H.Wang,ag K.Wiik,w C.Williams,j S.X.Wu,l,m P.C.Xia,h J.L.Yan,g L.G.Yan,h C.G.Yang,i J.Yang,aƒ M.Yang,i S.W.Ye,v,4 P.Yeh,ag Z.Z.Xu,v H.Y.Zhang,ƒ Z.P.Zhang,v D.X.Zhao,h G.Y.Zhu,i W.Z.Zhu,g H.L.Zhuang,i A.Zichichi,j B.Zimmermann,ai P.Zuccon.ae

Measurements of inclusive production of the Lambda, Xi- and Xi*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Lambda and Xi- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, eta. The mean number of Lambda, Xi- and Xi*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV < pt< 2.5 GeV, |eta| < 1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark theta+(1540) in two-photon collisions through the decay theta+ -> proton K0s is also presented. No evidence for production of this state is found.

A measurement of the cosmic ray positron fraction e+/(e++e−) in the energy range of 1–30 GeV is presented. The measurement is based on data taken by the AMS-01 experiment during its 10 day Space Shuttle flight in June 1998. A proton background suppression on the order of 106 is reached by identifying converted bremsstrahlung photons emitted from positrons.

An LHP-based thermal control system for cryocoolers on the Alpha Magnetic Spectrometer (AMS-02) has been designed, and analyzed by means of the system level model based on Sinda/Fluint. Integrated with the International Space Station (ISS) model by means of a time-varying sink temperature definition, the performance of LHP-based thermal control is investigated. A parametric analysis is carried out also to understand the influence of critical parameters on the operation of LHP.

The L3+C muon detector at the CERN electron-positron collider, LEP, is used for the detection of very-high-energy cosmic gamma-ray sources through the observation of muons of energies above 20, 30, 50 and 100 GeV. Daily or monthly excesses in the rate of single-muon events pointing to some particular direction in the sky are searched for. The periods from mid July to November 1999, and April to November 2000 are considered. Special attention is also given to a selection of known gamma-ray sources. No statistically significant excess is observed for any direction or any particular source. (c) 2006 Elsevier B.V. All rights reserved.

The cross section for open-beauty production in photon–photon collisions is measured using the whole high-energy and high-luminosity data sample collected by the L3 detector at LEP. This corresponds to 627 pb−1 of integrated luminosity for electron–positron centre-of-mass energies from 189 to 209 GeV. Events containing b quarks are identified through their semi-leptonic decay into electrons or muons. The e+e−→e+e−bb¯X cross section is measured within our fiducial volume and then extrapolated to the full phase space. These results are found to be in significant excess with respect to Monte Carlo predictions and next-to-leading order QCD calculations.

The shadowing of high-energy cosmic rays by the Moon has been observed with a significance of 9.4 standard deviations with the L3+C muon spectrometer at CERN. A significant effect of the Earth magnetic field is observed. Since no event deficit on the east side of the Moon has been observed, an upper limit at 90% confidence level on the antiproton to proton ratio of 0.11 is obtained for primary energies around 1TeV.

Exclusive rho+rho- production in two-photon collisions between a quasi-real photon, gamma, and a mid-virtuality photon, gamma*, is studied with data collected at LEP at centre-of-mass energies root(s)=183-209GeV with a total integrated luminosity of 684.8pb^-1. The cross section of the gamma gamma* -> rho+ rho- process is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 0.2GeV^2 < Q^2 <0.85GeV^2 and 1.1GeV < W_gg < 3GeV. These results, together with previous L3 measurements of rho0 rho0 and rho+ rho- production, allow a study of the gamma gamma* -> rho rho process over the Q^2-region 0.2GeV^2 < Q^2 < 30 GeV^2.

Neutral-current four-fermion production, e+e- -> ffff is studied in 0.7/fb of data collected with the L3 detector at LEP at centre-of-mass energies root(s)=183-209GeV. Four final states are considered: qqvv, qqll, llll and llvv, where l denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e+e- -> Zgamma* -> ffff process is studied and its total cross section at the average centre-of-mass energy 196.6GeV is found to be 0.29 +/- 0.05 +/- 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qqll final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found.

The evolution of the electromagnetic coupling, alpha, in the momentum-transfer range 1800 GeV2 < -Q(2) < 21600 GeV2 is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies root s = 189-209 GeV. The running of a is parametrised as:alpha(Q(2)) = (1-C Delta alpha(Q2))/(alpha 0)where alpha(0) = alpha(Q(2) = 0) is the fine-structure constant and C = 1 corresponds to the evolution expected in QED. A fit to the differential cross section of the e(+)e(-) -> e(+)e(-) process for scattering angles in the range vertical bar cos theta vertical bar < 0.9 excludes the hypothesis of a constant value of alpha, C = 0, and validates the QED prediction with the result:C = 1.05 +/- 0.07 +/- 0.14,where the first uncertainty is statistical and the second systematic. (c) 2005 Elsevier B.V. All rights reserved.