M. Diemoz

A search for axion-like particles was performed at the 400 GeV proton beam-dump experiment at CERN. Exploring an empty decay region of 35 m length and 9 m2 cross section, we searched for decays of neutral and penetrating scalar particles into a pair of photons, electrons or muons. No evidence for the existence for such particles was found in this experiment. Limits are quoted as a function of the mass and of the model independent decay constant of axions.

We report the results of first physics runs of the L3 detector at LEP. Based on 2538 hadron events, we determined the mass mz0 and the width Γz0 of the intermediate vector boson Z0 to be mz0=91.132±0.057 GeV (not including the 46 MeV LEP machine energy uncertainty) and Γz0=2.588±0.137 GeV. We also determined Γinvisible=0.567±0.080 GeV, corresponding to 3.42±0.48 number of neutrino flavors. We also measured the muon pair cross section and determined the branching ratio Γμμ=Γh=0.056±0.006. The partial width of Z0→e+e− is Γee=88±9±7 MeV.

The total cross sections for top, bottom and charm production in hadronic collisions at energies of practical interest are studied using a recent complete calculation of the next-to-leading QCD corrections. A set of proton structure functions with QCD evolution at next-to-leading accuracy, with variable Λ and including updated experimental information, is used. A careful discussion of theoretical errors due to scale dependence and ignorance of Λ, input gluon density and so on is given. It is found that particularly reliable predictions can be given for top or b′ production at SppS and Tevatron energies. By comparison with the UA1 experimental bounds, we find the limits mt > 41 GeV and mb′ > 34 GeV. The cross sections for heavy quark production at supercolliders (LHC, SSC) are estimated. Bottom and charm production in fixed target, ISR and collider experiments are considered. It is found that the corrective terms tend to improve the agreement with the data. In particular, the computed amount of b-production agrees with the measurements by UA1 in pp collisions at S = 0.63 TeV and by NA10 and WA78 in π−N at S = 23–24.5 GeV. The charm production data in pN collisions at fixed target energies are in general agreement with the corrected QCD prediction with mc ≅ 1.5 GeV, i.e. without need of assuming a small effective charm mass.

We give several sets of parton densities derived from recent measurements of structure functions in deep inelastic scattering. The difference among these densities reflects the uncertainties from deep inelastic data of different experiments, allowing an estimate of the error band for the predictions one may obtain for any given hadronic process at higher energy. The densities are available at any scaleQ 2≦5.109 GeV2 andx≧5.10−5 and include next-to-leading corrections as well as threshold effects due to heavy flavours. A comparison with a large set of data in a wide range of scales (Drell-Yan,W andZ production, etc.) is also presented.

A search for decays of heavy neutrinos was conducted by the CHARM Collaboration in a prompt neutrino beam produced by dumping 400 GeV protons in a Cu target, and in the CERN wide-band neutrino beam produced by 400 GeV primary protons. No candidate event was found. In the beam-dump experiment heavy neutrinos have been assumed to be produced by mixing in charmed D meson decays. Neutrinos decaying into e+e−ve, μ+e−vμ, and μ+μ−vμ were searched for. Limits of |Uei|2, |Uμi|2 < 10−7 were obtained for neutrino masses around 1.5 GeV. In the wide-band experiment heavy neutrinos were assumed to be produced by neutral-current neutrino interactions in the CHARM calorimeter. Here a search was made for neutrinos decaying into a μ and hadrons. This experiment is sensitive to decays of neutrinos with mass in the range 0.5–2.8 GeV with limits of |Uμi|2 < 3 × 10−4 for masses around 2.5 GeV. These measurements extend our previous results in the mass range 10–400 MeV.

SABRE aims to directly measure the annual modulation of the dark matter interaction rate with NaI(Tl) crystals. A modulation compatible with the standard hypothesis, in which our Galaxy is immersed in a dark matter halo, has been measured by the DAMA experiment in the same target material. Other direct detection experiments, using different target materials, seem to exclude the interpretation of such modulation in the simplest scenario of WIMP-nucleon elastic scattering. The SABRE experiment aims to carry out an independent search with sufficient sensitivity to confirm or refute the DAMA claim. The goal of the SABRE experiment is to achieve the lowest background rate for a NaI(Tl) experiment (order of 0.1 cpd/kg/keVee in the energy region of interest for dark matter). This challenging goal could be achievable by operating high-purity crystals inside a liquid scintillator veto for active background rejection. In addition, twin detectors will be located in the northern and southern hemispheres to identify possible contributions to the modulation from seasonal or site-related effects. The SABRE project includes an initial Proof-of-Principle phase at LNGS (Italy), to assess the radio-purity of the crystals and the efficiency of the liquid scintillator veto. This paper describes the general concept of SABRE and the expected sensitivity to WIMP annual modulation.

The changes in the absorption spectra induced by Co60 irradiation and high temperature annealing was studied for selected PbWO4 crystals. Based on radiation and annealings induced absorption spectra, four color centers are proposed, which could be responsible for shaping the absorption spectrum of PbWO4 crystals below 3.6 eV, namely Pb3+, O−, F, and F+ centers. Thermoluminescence (TSL) glow curves above room temperature were also studied on these samples to determine further the trap levels resulting from irradiation. Correlation between the results obtained by TSL and Co60 irradiation induced absorption changes is discussed.

A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed with the L3 detector at LEP. Sequential, vector and mirror natures of heavy leptons are considered. No evidence for their existence is found and lower limits on their masses are set.

Single- and multi-photon events with missing energy are selected in 619 pb−1 of data collected by the L3 detector at LEP at centre-of-mass energies between 189 and 209 GeV. The cross sections of the process e+e−→νν̄γ(γ) are found to be in agreement with the Standard Model expectations, and the number of light neutrino species is determined, including lower energy data, to be Nν=2.98±0.05±0.04. Selection results are given in the form of tables which can be used to test future models involving single- and multi-photon signatures at LEP. These final states are also predicted by models with large extra dimensions and by several supersymmetric models. No evidence for such models is found. Among others, lower limits between 1.5 and 0.65 TeV are set, at 95% confidence level, on the new scale of gravity for the number of extra dimensions between 2 and 6.

The cross section ratio of neutral-current and charged-current semi-leptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result: Rv=0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio, the electroweak mixing angle is determined to be sin2θw=0.236+0.012(mc−1.5)±0.005 (exp.)±0.003 (theor.), where mc is the charm-quark mass in GeV/c2.

A search for heavy neutrinos was conducted in the neutrino beam produced by the 400 GeV proton beam-dump and in the 400 GeV wide-band neutrino beam at CERN. A heavy neutrino associated with the τ lepton was searched for in the beam-dump experiment. No assumption on the nature of heavy neutrinos was made in the wide-band beam experiment. A search was made for neutrinos decaying into two electrons and a light neutrino. Since no events were observed, an upper limit on the neutrino mixing angles as a function of the neutrino mass is derived. The beam-dump experiment is sensitive to a neutrino mass range of 10–250 MeV and an upper limit at 90% confidende level on the square of the neutrino mixing angle of θ10−10 was obtained for neutrino masses greater than 180 MeV. The wide-band neutrino experiment is sensitive to neutrinos with a mass in a larger range (10–490 MeV), and for masses greater than 250 MeV yields an upper limit on the square of the neutrino mixing angle of θ10−6.

The cross-section ratio of neutral-current and charged-current semileptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result:R v =0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio we determined the electroweak mixing angle sin2 θ W , wherem c is the charm-quark mass in GeV/c2. Comparison with direct measurements ofm w andm z determines the radiative shift of the intermediate boson mass Δr=0.077±0.025(exp.)±0.038(syst.), in agreement with the prediction. Assuming the validity of the electroweak standard theory we determined ϱ=0.990−0.013(m c −1.5)±0.009(exp.)±0.003(theor.).

In this Report, QCD results obtained from a study of hadronic event structure in high energy e+e- interactions with the L3 detector are presented. The operation of the LEP collider at many different collision energies from 91 to 209 GeV offers a unique opportunity to test QCD by measuring the energy dependence of different observables. The main results concern the measurement of the strong coupling constant, αs, from hadronic event shapes and the study of effects of soft gluon coherence in charged particle multiplicity and momentum distributions.

The absolute muon flux between 20 GeV and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0 degree to 58 degree. Due to the large exposure of about 150 m2 sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3 % at 150 GeV in the vertical direction is achieved. The ratio of positive to negative muons is studied between 20 GeV and 500 GeV, and the average vertical muon charge ratio is found to be 1.285 +- 0.003 (stat.) +- 0.019 (syst.).

Scalar partners of quarks and leptons, predicted in supersymmetric models, are searched for in e^+e^- collisions at centre-of-mass energies between 192GeV and 209GeV at LEP. No evidence for any such particle is found in a data sample of 450 pb^-1. Upper limits on their production cross sections are set and lower limits on their masses are derived in the framework of the Minimal Supersymmetric Standard Model.

We report on the construction and test of a lead-scintillating fiber (spaghetti) calorimeter built to fill the gap between endcaps and barrel in the L3 BGO detector. Results from test-beam, as well as MC simulations for the prototypes and for the full detector, are presented.

Correlated measurements of emission spectra, photoluminescence and scintillation decays, thermoluminescence, and light yield were performed on a selected set of undoped and La-doped PbWO4 single crystals. The samples were grown from 5N purity raw powders and show the blue emission component only. Distinct influence of La doping was found in the decays, thermoluminescence and light yield characteristics. It is discussed in the light of the direct influence of La doping on suppressing the creation of point defect centers in the PbWO4 lattice, which are involved in the energy transfer and storage processes in this material.

Inclusive neutrino and antineutrino charged current interactions were studied in the CHARM detector exposed to neutrino and antineutrino Wide Band Beams of the CERN 400 GeV SPS. The x and Q2 dependence of the structure functions F2 and xF3 and of the antiquark momentum distribution q were determined. The data have been interpreted in terms of QCD theory using the Furmanski-Petronzio method. In this way we have determined ΛLO = [190−40+70 (stat) ± 70 (syst.)] MeV and the structure functions of quarks and gluons without specific assumptions on their analytic dependence. The results agree with previous experiments which relied on model assumptions in the analysis. We conclude that the model independent simultaneous analysis of the xF3, F2, q structure functions gives a more reliable determination of the gluon distribution in the nucleon.

We present a study of jet multiplicities based on 37 000 hadronic Z0 boson decays. From this data we determine the strong coupling constant αs=0.115±0.005 (exp.)−0.010+0.012 (theor.) to second order QCD at √s=91.22GeV.

physica status solidi (a)Volume 160, Issue 2 p. R5-R6 Research Letter Influence of La3+-Doping on Radiation Hardness and Thermoluminescence Characteristics of PbWO4 S. Baccaro, S. Baccaro ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorP. Bohacek, P. Bohacek Institute of Physics, Cukrovarnicka 10, 16200 Prague, Czech RepublicSearch for more papers by this authorB. Borgia, B. Borgia INFN, Dept. of Physics, University of Roma 1, P. le A. Moro 2, Roma, ItalySearch for more papers by this authorA. Cecilia, A. Cecilia ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorI. Dafinei, I. Dafinei INFN, Dept. of Physics, University of Roma 1, P. le A. Moro 2, Roma, ItalySearch for more papers by this authorM. Diemoz, M. Diemoz INFN, Dept. of Physics, University of Roma 1, P. le A. Moro 2, Roma, ItalySearch for more papers by this authorM. Ishii, M. Ishii SIT, Shonan Institute of Technology, Fujisawa 251, JapanSearch for more papers by this authorO. Jarolimek, O. Jarolimek CRYTUR Preciosa a.s., Palackeho 175, 51119 Turnov, Czech RepublicSearch for more papers by this authorM. Kobayashi, M. Kobayashi KEK, National Laboratory for High Energy Physics, Tsukuba 305, JapanSearch for more papers by this authorM. Martini, M. Martini INFM and Dept. of Physics, University of Milano, Via Celoria 16, 20133 Milano, ItalySearch for more papers by this authorM. Montecchi, M. Montecchi ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorM. Nikl, M. Nikl Institute of Physics, Cukrovarnicka 10, 16200 Prague, Czech RepublicSearch for more papers by this authorK. Nitsch, K. Nitsch Institute of Physics, Cukrovarnicka 10, 16200 Prague, Czech RepublicSearch for more papers by this authorY. Usuki, Y. Usuki Furukawa Co., Yoshima, Iwaki 970-11, JapanSearch for more papers by this authorA. Vedda, A. Vedda INFM and Dept. of Physics, University of Milano, Via Celoria 16, 20133 Milano, ItalySearch for more papers by this author S. Baccaro, S. Baccaro ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorP. Bohacek, P. Bohacek Institute of Physics, Cukrovarnicka 10, 16200 Prague, Czech RepublicSearch for more papers by this authorB. Borgia, B. Borgia INFN, Dept. of Physics, University of Roma 1, P. le A. Moro 2, Roma, ItalySearch for more papers by this authorA. Cecilia, A. Cecilia ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorI. Dafinei, I. Dafinei INFN, Dept. of Physics, University of Roma 1, P. le A. Moro 2, Roma, ItalySearch for more papers by this authorM. Diemoz, M. Diemoz INFN, Dept. of Physics, University of Roma 1, P. le A. Moro 2, Roma, ItalySearch for more papers by this authorM. Ishii, M. Ishii SIT, Shonan Institute of Technology, Fujisawa 251, JapanSearch for more papers by this authorO. Jarolimek, O. Jarolimek CRYTUR Preciosa a.s., Palackeho 175, 51119 Turnov, Czech RepublicSearch for more papers by this authorM. Kobayashi, M. Kobayashi KEK, National Laboratory for High Energy Physics, Tsukuba 305, JapanSearch for more papers by this authorM. Martini, M. Martini INFM and Dept. of Physics, University of Milano, Via Celoria 16, 20133 Milano, ItalySearch for more papers by this authorM. Montecchi, M. Montecchi ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorM. Nikl, M. Nikl Institute of Physics, Cukrovarnicka 10, 16200 Prague, Czech RepublicSearch for more papers by this authorK. Nitsch, K. Nitsch Institute of Physics, Cukrovarnicka 10, 16200 Prague, Czech RepublicSearch for more papers by this authorY. Usuki, Y. Usuki Furukawa Co., Yoshima, Iwaki 970-11, JapanSearch for more papers by this authorA. Vedda, A. Vedda INFM and Dept. of Physics, University of Milano, Via Celoria 16, 20133 Milano, ItalySearch for more papers by this author First published: 16 November 2001 https://doi.org/10.1002/1521-396X(199704)160:2<R5::AID-PSSA99995>3.0.CO;2-LCitations: 67AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume160, Issue2April 1997Pages R5-R6 RelatedInformation

Doping by different trivalent ions (La3+, Lu3+, Gd3+, Y3+, Sc3+) was systematically studied in PbWO4 crystals in the same way, using raw material from the same source. The result was compared with an undoped sample (actually a Pb-rich one) and samples doped with divalent (Cd2+) and pentavalent (Nb5+) ions. All the trivalent ions but Sc3+ gave a significant improvement in transmittance in the short wavelength region (330–450 nm) and in radiation hardness. Among all the tested dopants, Y3+ and Gd3+ showed the best result; these dopants may be worth further studies, since they have another advantage of the segregation coefficient close to unity.

We have made a precise measurement of the cross section for e+e−→Z0→hadrons with the L3 detector at LEP, covering the s range from 88.28 to 95.04 GeV. From a fit to the Z0 mass, total width, and the hadronic cross section to be MZ0=91.160 ± 0.024 (experiment) ±0.030(LEP) GeV, ΓZ0=2.539±0.054 GeV, and σh(MZ0)=29.5±0.7 nb. We also used the fit to the Z0 peak cross section and the width todetermine Γinvisible=0.548±0.029 GeV, which corresponds to 3.29±0.17 species of light neutrinos. The possibility of four or more neutrino flavors is thus ruled out at the 4σ confidence level.

We have searched for scalar muons μ, scalar electrons ẽ, and winos W̃ from the reactions e+e− →ẽ+ẽ−, μ+μ−, W̃+W̃− at √s ∼ 91 GeV with an integrated luminosity of 157 nb −1. We have searched for μ+μ−, e+e−, or e−μ final states with missing transverse momentum PT > 6 GeV. These final states are signatures for the production of ẽ, μ, and W̃. We found no events. Our results are Mμ > 41 GeV, Mẽ > 41 GeV, and MW̃ > 44 GeV at the 95% confidence level.

Single top production in e+e- annihilations is searched for in data collected by the L3 detector at centre-of-mass energies from 189 to 209 GeV, corresponding to a total integrated luminosity of 634 pb-1. Investigating hadronic and semileptonic top decays, no evidence of single top production at LEP is obtained and upper limits on the single top cross section as a function of the centre-of-mass energy are derived. Limits on possible anomalous couplings, as well as on the scale of contact interactions responsible for single top production are determined.

The ratio of the coupling strengths of electron- and muon-neutrinos to the neutral weak current, derived from measurements of total semileptonic neutrino cross sections on an isoscalar target, is reported on. Using an enriched electron-neutrino beam with equal fluxes of νe and νe produced by dumping the 400 GeV on beam of the CERN-SPS into thick copper targets (beam-dump), σ(NC((−)νe))/σ(CC((−)νe)) = 0.406−0.135+0.145 is measured. Combining this value with the re we obtained in an exposure to a narrow band neutrino beam, the ratio of the coupling constants gνeνe/gνμv̄μ = =1.05−0.18+0.15 is derived, in good agreement with universal coupling strength of the electron- and muon-neutrino to the neutral weak current.

Ultra-pure NaI(Tl) crystals are the key element for a model-independent verification of the long standing DAMA result and a powerful means to search for the annual modulation signature of dark matter interactions. The SABRE collaboration has been developing cutting-edge techniques for the reduction of intrinsic backgrounds over several years. In this paper we report the first characterization of a 3.4 kg crystal, named NaI-33, performed in an underground passive shielding setup at LNGS. NaI-33 has a record low $^{39}$K contamination of 4.3$\pm$0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1$\pm$0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of $^{226}$Ra and $^{228}$Th inside the crystal to be $5.9\pm0.6 \mu$Bq/kg and $1.6\pm0.3 \mu$Bq/kg, respectively, which would indicate a contamination from $^{238}$U and $^{232}$Th at part-per-trillion level. We measured an activity of 0.51$\pm$0.02 mBq/kg due to $^{210}$Pb out of equilibrium and a $\alpha$ quenching factor of 0.63$\pm$0.01 at 5304 keV. We illustrate the analyses techniques developed to reject electronic noise in the lower part of the energy spectrum. A cut-based strategy and a multivariate approach indicated a rate, attributed to the intrinsic radioactivity of the crystal, of $\sim$1 count/day/kg/keV in the [5-20] keV region.

A very good radiation resistance of lead tungstate crystals is mandatory for their use in the high-precision electromagnetic calorimeter of the CMS experiment at LHC. Since the beginning of 1996 we have organised systematic investigations of the parameters influencing the radiation hardness of this crystal. Two classes of parameters have been particularly studied, the first one related to the control of the stoichiometry and structure-associated defects, the second one connected with the suppression and the charge compensation of existing defects with different kinds of doping ions. This paper reports about the second part of this study and complements a first paper where the role of the stoichiometry was already discussed. Results of tests are given on a significant statistical sample of full size crystals (23 cm) which show a considerable improvement in the optical properties and the radiation resistance of appropriately doped crystals.

We report on a search for the first generation heavy neutrino that is an isosinglet under the standard SU(2)_L gauge group. The data collected with the L3 detector at center-of-mass energies between 130 GeV and 208 GeV are used.The decay channel N_e --> eW is investigated and no evidence is found for a heavy neutrino, N_e, in a mass range between 80 GeV and 205 GeV. Upper limits on the mixing parameter between the heavy and light neutrino are derived.

La-doping significantly improves the radiation hardness of PbWO4 against γ-ray irradiation. The induced absorption coefficient of La-doped samples is as small as 2 m−1 at 420 nm even at 108 rad (106 Gy). The radiation-induced phosphorescence is more than three orders of magnitude less in La-doped PbWO4 crystals than in undoped ones.

Doubly-charged Higgs bosons are searched for in e^+e^- collision data collected with the L3 detector at LEP at centre-of-mass energies up to 209 GeV. Final states with four leptons are analysed to tag the pair-production of doubly charged Higgs bosons. No significant excess is found and lower limits at 95% confidence level on the doubly-charged Higgs boson mass are derived. They vary from 95.5 GeV to 100.2 GeV, depending on the decay mode. Doubly-charged Higgs bosons which couple to electrons would modify the cross section and forward-backward asymmetry of the e^+e^- -> e^+e^- process. The measurements of these quantities do not deviate from the Standard Model expectations and doubly-charged Higgs bosons with masses up to the order of a TeV are excluded.

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 f1(1285) meson is observed and the Q2 dependence of its production is compared to different form factor models. The γγ-coupling parameter Γγγ is found to be 3.5±0.6(stat.)±0.5(sys.) keV. The branching fraction Γ(f1(1285)→a0π)/Γ(f1(1285)→ηππ) is also measured.

A method to calibrate the L3 electromagnetic calorimeter with cosmic muons has been tested on a matrix of 100 tapered BGO crystals. Calibration constants in the energy range of 20–30 MeV were measured at the 2% level collecting about 200 muons per crystal. The results are in agreement with the calibration constant determined using a 10 GeV electron beam.

A low-energy muon neutrino beam was used to illuminate two similar fine-grained neutrino detectors placed at 123 m and 903 m from the beginning of the neutrino source. The fiducial masses of the “close” and the “far” detector were about 36 tons and 120 tons respectively. The average energy of the selected neutrino events was 1.5 GeV. Data were recorded for an integrated flux of about 1019 protons. Quasielastic charged current events initiated by νe's have been searched for and an upper limit of 2.7%, at 90% confidence level, is obtained for the fraction of νμ's transformed into νe's. For complete mixing this correspnds to a limit Δm2 ⩽ 0.20 eV2 for the transition νμ → νe and to a minimum value of the mixing parameter sin22θ = 0.04. In the same data sample we compared the rates in the two detectors of νμ-initiated charged current events, mainly of quasielastic type: we conclude that oscillations of νμ's to ντ's, and possibly heavier neutrinos, do not appear. For complete mixing the limit in this case is Δm2 ⩽ 0.29 eV2.

We present a study of 4200 4-jet events from Z0 boson decays. The measured angular correlations between jets are reproduced well by QCD. An alternative abelian model fails to describe the data.

We have measured the properties of Z0 → bb decays using a sample of 944 inclusive muon events, corresponding to 18 000 hadron events obtained with the L3 detector at LEP. We measured the partial decay width of the Z0 into bb, Γbb=353±48 MeV, and we determined the vector coupling of the Z0 to the b quark; grmv2(b)=0.095±0.047. We measured the forward-backward charge asymmetry in e+e− → bb events at √s≈Mv, and obtained Abb=13.3±9.9%.

We present the results from a search for the light neutral scalar Higgs boson h° and the pseudoscalar Higgs boson A° of the minimal super-symmetric standard model. The analysis is based on a data sample corresponding to 71 000 hadronic Z° decays recorded with the L3 detector at LEP. No evidence for the existence of the neutral Higgs bosons h° and A° has been found. The region of h° and A° masses up to 41.5 GeV is excluded at 95% confidence level.

A new experimental determination of the electro-weak mixing angle θW is reported based on a second exposure of the CHARM calorimeter to the CERN-SPS wide-band beam. The ratio R of muon-neutrino- and muon-antineutrino-electron scattering cross section has been determined from a sample of 37 ± 10 and 35 ± 10 events. The experimental result is R = 1.26−0.45+0.72, corresponding to a value of sin2θW = 0.216 ± 0.055. The total sample of events collected in the CHARM calorimeter during the two exposures is (83 ± 16)νμe events and (112 ± 21)νμe events, leadint to the final result sin2θW = 0.215 ± 0.032. The systematic error is estimated to be ± 0.012.

SABRE (Sodium-iodide with Active Background REjection) is a direct dark matter search experiment based on an array of radio-pure NaI(Tl) crystals surrounded by a liquid scintillator veto. Twin SABRE experiments in the Northern and Southern Hemispheres will differentiate a dark matter signal from seasonal and local effects. The experiment is currently in a Proof-of-Principle (PoP) phase, whose goal is to demonstrate that the background rate is low enough to carry out an independent search for a dark matter signal, with sufficient sensitivity to confirm or refute the DAMA result during the following full-scale experimental phase. The impact of background radiation from the detector materials and the experimental site needs to be carefully investigated, including both intrinsic and cosmogenically activated radioactivity. Based on the best knowledge of the most relevant sources of background, we have performed a detailed Monte Carlo study evaluating the expected background in the dark matter search spectral region. The simulation model described in this paper guides the design of the full-scale experiment and will be fundamental for the interpretation of the measured background and hence for the extraction of a possible dark matter signal.

The ordinary and the extraordinary complex refractive index of PbWO4 together with the crystal optical axis orientation are determined on the basis of transmittance and reflectance measurements at normal incidence with polarised light and the measurement of the separation angle between the ordinary and the extraordinary ray at various laser wavelengths. The real part of the extraordinary complex refractive index is lower than the ordinary one (i.e. PbWO4 is a negative uniaxial crystal) and they seem not to be affected by a 30 ppm Nb5+ doping.

The amplitude of the signal collected from the PbWO4 crystals of the CMS electromagnetic calorimeter is reconstructed by a digital filtering technique. The amplitude reconstruction has been studied with test beam data recorded from a fully equipped barrel supermodule. Issues specific to data taken in the test beam are investigated, and the implementation of the method for CMS data taking is discussed.

Measurements of coherent π0 production by muon-neutrinos and antineutrinos on nuclei in marble have been carried out using the CHARM neutrino detector in the CERN-SPS neutrino wide-band beam. We determined the cross sections σν = (96±42)×10−40cm2 and σν = (79±26)×10−40 cm2 per average marble nucleus. Comparing these experimental results to theoretical predictions we evaluated the isovector axial vector neutral-current coupling constant ∣β∣ = 1.08±0.24, averaged over the neutrino and the antineutrino results, and found agreement with the prediction of the standard model, β = 1.0. From the ratio of coherent π0 production by neutral-current interactions observed in this experiment and of coherent π− production by charged-current interactions of antineutrinos measured in BEBC a value of ∣β∣ = 1.10±0.23 is derived.

We present new results on the radiopurity of a 3.4-kg NaI(Tl) crystal scintillator operated in the SABRE proof-of-principle detector setup. The amount of potassium contamination, determined by the direct counting of radioactive $^{40}\mathrm{K}$, is found to be $2.2\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{ }\mathrm{ppb}$, lowest ever achieved for NaI(Tl) crystals. With the active veto, the average background rate in the crystal in the 1--6 keV energy region of interest (ROI) is $1.20\ifmmode\pm\else\textpm\fi{}0.05\text{ }\text{ }\mathrm{counts}/\mathrm{day}/\mathrm{kg}/\mathrm{keV}$, which is a breakthrough since the DAMA/LIBRA experiment. Our background model indicates that the rate is dominated by $^{210}\mathrm{Pb}$ and that about half of this contamination is located in the polytetrafluoroethylene reflector. We discuss ongoing developments of the crystal manufacture aimed at the further reduction of the background, including data from purification by zone refining. A projected background rate lower than $\ensuremath{\sim}0.2\text{ }\text{ }\mathrm{counts}/\mathrm{day}/\mathrm{kg}/\mathrm{keV}$ in the ROI is within reach. These results represent a benchmark for the development of next-generation NaI(Tl) detector arrays for the direct detection of dark matter particles.

Final results of the search for the Standard Model Higgs boson are presented for the data collected by the L3 detector at LEP at centre-of-mass energies up to about 209 GeV. These data are compared with the expectations of Standard Model processes for Higgs boson masses up to 120 GeV. A lower limit on the mass of the Standard Model Higgs boson of 112.0 GeV is set at the 95 % confidence level. The most significant high mass candidate is a Hnunu event. It has a reconstructed Higgs mass of 115 GeV and it was recorded at root(s)=206.4 GeV.

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at centre-of-mass energies between 189 and 209GeV, corresponding to an integrated luminosity of 629.4/pb. Decays into a charm and a strange quark or into a tau lepton and its neutrino are considered. No significant excess is observed and lower limits on the mass of the charged Higgs boson are derived at the 95% confidence level. They vary from 76.5 to 82.7GeV, as a function of the H->tv branching ratio.

We have searched for the neutral Higgs boson produced in the decays of the Z0 through the processes Z0→H0μ+μ−, Z0→H0e+e− and Z0→H0νν. The data sample analysed corresponds to about 50 200 Z0→hadrons. Combining the results of all three processes we exclude a minimal standard model Higgs boson in the mass range 2<MH0<32 GeV at the 95% confidence level.

We have measured the partial widths of the Z0 into lepton pairs, and the forward-backward charge asymmetry for the process e+e−→μ+μ− using the L3 detector at LEP. We obtain an average Γℓℓ of 83.0±2.1±1.1 MeV.From this result and the asymmetry measurement, we extract the values of the vector and axial vector couplings of the Z0 to leptons: grmv=−0.066−0.027+0.046 and grmA= −0.495−0.007+0.007.

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 L\'evy stable distribution in conjunction with a model where a particle's momentum is correlated with its space-time point of production, the \taumodel. 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 \taumodel, and this is investigated using an \adhoc/ modification.

The cross section of W-boson pair-production is measured with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 629.4 pb−1, collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834 four-fermion events with W bosons decaying into hadrons or leptons are selected. The total cross section is measured with a precision of 1.4% and agrees with the Standard Model expectation. Assuming charged-lepton universality, the branching fraction for hadronic W-boson decays is measured to be: Br(W→hadrons)=67.50±0.42(stat.)±0.30(syst.)%, in agreement with the Standard Model. Differential cross sections as a function of the W− production angle are also measured for the semi-leptonic channels qqeν and qqμν.

A search, in e^+e^- collisions, for chargino, neutralino, scalar lepton and scalar quark pair-production is performed, without assuming R-parity conservation in decays, in the case that only one of the coupling constants lambda_ijk or lambda''_ijk is non-negligible. No signal is found in data up to a centre-of-mass energy of 208GeV. Limits on the production cross sections and on the masses of supersymmetric particles are derived.

We search, in the context of extra-dimension scenarios, for the possible existence of brane fluctuations, called branons. Events with a single photon or a single Z-boson and missing energy and momentum collected with the L3 detector in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are analysed. No excess over the Standard Model expectations is found and a lower limit at 95% confidence level of 103 GeV is derived for the mass of branons, for a scenario with small brane tensions. Alternatively, under the assumption of a light branon, brane tensions below 180 GeV are excluded.

The process e+e−→W+W−γ is studied using the data collected by the L3 detector at LEP. New results, corresponding to an integrated luminosity of 427.4 pb−1 at centre-of-mass energies from 192 to 207 GeV, are presented. The W+W−γ cross sections are measured to be in agreement with Standard Model expectations. No hints of anomalous quartic gauge boson couplings are observed. Limits at 95% confidence level are derived using also the process e+e−→νν̄γγ.

A review of experimental results on structure functions extracted from high energy neutrino interactions is presented. The interpretation of these results in the framework of Quantum Chromodynamics is also discussed, together with their extrapolation to the collider energy domain and beyond.

The evolution of the electromagnetic coupling, alpha, in the momentum-transfer range 1800GeV^2 < -Q^2 < 21600GeV^2 is studied with about 40000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies 189-209GeV. The running of alpha is parametrised as: alpha(Q^2) = alpha_0/(1-C Delta alpha(Q^2)), 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 |cos theta|<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.

We present a parametrization of the parton densities as derived from the data collected by the CHARM Collaboration in the wide band beam neutrino and antineutrino weak charged-current interactions. They are rescaled to the proton and calculated at a reference Q2 value of 10 GeV2 including the next-to-leading order corrections and imposing the Gross-Llewellyn Smith and the momentum sum rules.

We have measured the cross section for e+e−→hadrons over the center of mass energy range of the Z0 peak, from 88.22 to 95.03 GeV. We determine the Z0 mass Mz=91.164±0.013 (experiment) ±0.030 (LEP) GeV. Within the framework of the standard model we determine the invisible width, Γinvisible=0.502±0.018 GeV, and the number of light neutrino species, Nν=3.01±0.11. We exclude the existence of a supersymmetric scalar neutrino having a mass less than 31.4 GeV, at the 95% confidence level. We performed a model independent combined fit to the e+e−→hadrons and e+e−→μ+μ− data to determine total width, leptonic width and hadronic width of the Z0.

We have measured both the rates and the forward-backward asymmetry of ℓ+ℓ− from Z0→ℓ+ℓ− (where ℓ=μ, τ) with the L3 detector. We obtained Γℓℓ=88±4±3 MeV and the vector neutral current coupling constant, gv=0.00±0.07 and the axial vector neutral current coupling constant, gA=−0.515±0.015.

Performance tests of some aspects of the CMS ECAL were carried out on modules of the "barrel" sub-system in 2002 and 2003. A brief test with high energy electron beams was made in late 2003 to validate prototypes of the new Very Front End electronics. The final versions of the monitoring and cooling systems, and of the high and low voltage regulation were used in these tests. The results are consistent with the performance targets including those for noise and overall energy resolution, required to fulfil the physics programme of CMS at the LHC.

Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated.

physica status solidi (a)Volume 164, Issue 2 p. R9-R10 Research Letter Radiation Damage and Thermoluminescence of Gd-Doped PbWO4 S. Baccaro, S. Baccaro ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorP. Bohacek, P. Bohacek Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague, Czech RepublicSearch for more papers by this authorB. Borgia, B. Borgia INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma “La Sapienza”, 00185 Roma, ItalySearch for more papers by this authorA. Cecilia, A. Cecilia ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorS. Croci, S. Croci INFM, DIP. di Scienza dei Materiali, Universita di Milano, 20126 Milano, ItalySearch for more papers by this authorI. Dafinei, I. Dafinei INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma “La Sapienza”, 00185 Roma, ItalySearch for more papers by this authorM. Diemoz, M. Diemoz INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma “La Sapienza”, 00185 Roma, ItalySearch for more papers by this authorP. Fabeni, P. Fabeni IROE del CNR, Via Panciatichi 64, 50127 Firenze, ItalySearch for more papers by this authorM. Ishii, M. Ishii SIT, Shonan Institute of Technology, Fujisawa 251, JapanSearch for more papers by this authorM. Kobayashi, M. Kobayashi KEK, National Laboratory for High Energy Physics, Tsukuba 305, JapanSearch for more papers by this authorM. Martini, M. Martini INFM, DIP. di Scienza dei Materiali, Universita di Milano, 20126 Milano, ItalySearch for more papers by this authorM. Montecchi, M. Montecchi ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorM. Nikl, M. Nikl Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague, Czech RepublicSearch for more papers by this authorK. Nitsch, K. Nitsch Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague, Czech RepublicSearch for more papers by this authorG. Organtini, G. Organtini INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma III., 00146 Roma, ItalySearch for more papers by this authorG. P. Pazzi, G. P. Pazzi IROE del CNR, Via Panciatichi 64, 50127 Firenze, ItalySearch for more papers by this authorY. Usuki, Y. Usuki Furukawa Co., Yoshima, Iwaki 970-11, JapanSearch for more papers by this authorA. Vedda, A. Vedda INFM, DIP. di Scienza dei Materiali, Universita di Milano, 20126 Milano, ItalySearch for more papers by this author S. Baccaro, S. Baccaro ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorP. Bohacek, P. Bohacek Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague, Czech RepublicSearch for more papers by this authorB. Borgia, B. Borgia INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma “La Sapienza”, 00185 Roma, ItalySearch for more papers by this authorA. Cecilia, A. Cecilia ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorS. Croci, S. Croci INFM, DIP. di Scienza dei Materiali, Universita di Milano, 20126 Milano, ItalySearch for more papers by this authorI. Dafinei, I. Dafinei INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma “La Sapienza”, 00185 Roma, ItalySearch for more papers by this authorM. Diemoz, M. Diemoz INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma “La Sapienza”, 00185 Roma, ItalySearch for more papers by this authorP. Fabeni, P. Fabeni IROE del CNR, Via Panciatichi 64, 50127 Firenze, ItalySearch for more papers by this authorM. Ishii, M. Ishii SIT, Shonan Institute of Technology, Fujisawa 251, JapanSearch for more papers by this authorM. Kobayashi, M. Kobayashi KEK, National Laboratory for High Energy Physics, Tsukuba 305, JapanSearch for more papers by this authorM. Martini, M. Martini INFM, DIP. di Scienza dei Materiali, Universita di Milano, 20126 Milano, ItalySearch for more papers by this authorM. Montecchi, M. Montecchi ENEA-INN/TEC, Via Anguillarese 301, S.Maria di Galeria, 00060 Roma, ItalySearch for more papers by this authorM. Nikl, M. Nikl Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague, Czech RepublicSearch for more papers by this authorK. Nitsch, K. Nitsch Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague, Czech RepublicSearch for more papers by this authorG. Organtini, G. Organtini INFN, Sez. di Roma, Dipt. di Fisica, Universita di Roma III., 00146 Roma, ItalySearch for more papers by this authorG. P. Pazzi, G. P. Pazzi IROE del CNR, Via Panciatichi 64, 50127 Firenze, ItalySearch for more papers by this authorY. Usuki, Y. Usuki Furukawa Co., Yoshima, Iwaki 970-11, JapanSearch for more papers by this authorA. Vedda, A. Vedda INFM, DIP. di Scienza dei Materiali, Universita di Milano, 20126 Milano, ItalySearch for more papers by this author First published: 16 November 2001 https://doi.org/10.1002/1521-396X(199712)164:2<R9::AID-PSSA99999>3.0.CO;2-ZCitations: 35AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume164, Issue2December 1997Pages R9-R10 RelatedInformation

Results are presented from a study of the structure of high energy hadronic events recorded by the L3 detector at sqrt(s)>192 GeV. The distributions of several event shape variables are compared to resummed O(alphaS^2) QCD calculations. We determine the strong coupling constant at three average centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements, combined with previous L3 measurements at lower energies, demonstrate the running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +- 0.0058, where the first uncertainty is experimental and the second is theoretical.

The K0SK±π∓ 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 η(1475) and f1(1420) mesons are observed and their contribution is separated by measuring the formation rates as a function of the photon virtuality Q2. The η(1475) is found to be dominant for Q2 ⩽ 0.01GeV2 and its two-photon width is measured to be 0.23±0.05 (stat.) ±0.05 (sys.) keV. At higher Q2, the f1(1420) is formed and decays to K*(892)K. The γγ coupling and form factor parameters of this state are measured to be Γγγ = 3.2±0.6 (stat.) ±0.7 (sys.) keV and Λ1 = 926±72 (stat.) ±32 (sys.) MeV, respectively.

Avalanche photodiodes have been chosen as photon sensors for the electromagnetic calorimeter of the CMS experiment at the LHC. These sensors should operate in the 4 T magnetic field of the experiment. Because of the high neutron radiation in the detector extensive studies have been done by the CMS collaboration on the APD neutron radiation damage. The characteristics of these devices after irradiation have been analyzed, with particular attention to the quantum efficiency and the dark current. The recovery of the radiation-induced dark current has been studied carefully at room temperature and at slightly lower and higher temperatures. The temperature dependence of the annealing has been evaluated.

The x dependence of the longitudinal structure function FL was determined with the CHARM neutrino detector exposed to neutrino and antineutrino wide-band beams of the CERN 400 GeV SPS. The results show a clear deviation from the Callan-Gross relation. The amount and the x dependence of this deviation are in agreement with the contribution coming from a finite transverse momentum of the partons in the nucleon if both the intrinsc and perturbative QCD terms are taken into account.

A search for a Higgs boson produced in e^+e^- collisions in association with a Z boson and decaying into invisible particles is performed. Data collected at LEP with the L3 detector at centre-of-mass energies from 189 GeV to 209 GeV are used, corresponding to an integrated luminosity of 0.63/fb. Events with hadrons, electrons or muons with visible masses compatible with a Z boson and missing energy and momentum are selected. They are consistent with the Standard Model expectations. A lower limit of 112.3 GeV is set at 95% confidence level on the mass of the invisibly-decaying Higgs boson in the hypothesis that its production cross section equals that of the Standard Model Higgs boson. Relaxing this hypothesis, upper limits on the production cross section are derived.

Ensuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.

Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce)is one of the most widely used Cerium-doped Lutetium based scintillation crystals. Initially developed for medical detectors it rapidly became attractive for High Energy Particle Physics (HEP) applications, especially in the frame of high luminosity particle colliders. In this paper, a comprehensive and systematic study of LYSO:Ce ($[Lu_{(1-x)}Y_x]_2SiO_5$:$Ce$) crystals is presented. It involves for the first time a large number of crystal samples (180) of the same size from a dozen of producers.The study consists of a comparative characterization of LYSO:Ce crystal products available on the market by mechanical, optical and scintillation measurements and aims specifically, to investigate key parameters of timing applications for HEP.

A Higgs particle produced in association with a Z boson and decaying into two photons is searched for in the data collected by the L3 experiment at LEP. All possible decay modes of the Z boson are investigated. No signal is observed in 447.5 pb^-1 of data recorded at centre-of-mass energies up to 209 GeV. Limits on the branching fraction of the Higgs boson decay into two photons as a function of the Higgs mass are derived. A lower limit on the mass of a fermiophobic Higgs boson is set at 105.4 GeV at 95% confidence level.

In our previous papers we reported that La3+, Gd3+, Y3+, and Lu3+ dopings significantly improve the optical and scintillation characteristics, including radiation hardness, of PbWO4 single crystals. The hypothesis of Pb2+ deficiency in the grown crystals and its charge compensation by the mentioned trivalent ions occupying the Pb2+ sites has been proposed to explain the observed improvement. Under such assumption, tetravalent-ion doping may be as efficient as or even more efficient than trivalent-ion doping in improving PbWO4 scintillator. Recently we extended the dopant ions to stable tetravalent ions (Th4+, Zr4+) and some other ions (Ce3+,4+, Sb3+,5+, Mn2+). We have found that the tetravalent-ion (Th4+) doping gives similar improvement compared with the trivalent-ion doping in consistency with the expectation mentioned above. The ions with two different possible charge states (Ce3+,4+, Sb3+,5+) gave finite but much less improvement than the trivalent and tetravalent ions. Ce3+,4+ doping reduced the light yield significantly. Annealing of undoped PWO in PbO vapour was also studied to examine the possibility of reducing the Pb2+ deficiency

We have measured the cross-section of the reaction e+e− → γγ at center of mass energies around the Z0 mass. The results are in good agreement with QED predictions. For the QED cutoff parameters the limit of Λ+ > 103 GeV and Λ− 118 GeV are found. For the decays Z0→γ,Z0→π0γ, Z0→γγγ we find upper limits of 2.9 × 10−4,2.9×10−4 ,4.1×10−4 and 1.2×10−4, respectively. All limits are at 95% CL.

We have searched for charged and neutral leptons. We exclude stable Dirac neutrinos below 42.8 GeV and stable Majorana neutrinos below 34.8 GeV. From a search for unstable neutrinos we exclude masses below 46.4 GeV (Dirac) and below 45.1 GeV (Majorana). We exclude all masses of sequential charged and neutral leptons, except if both masses are larger than 42.8 GeV (for stable Dirac neutrinos). All mass limits correspond to 95% CL.

New measurements of the total crosssections of charged-current interactions of muonneutrinos and antineutrinos on isoscalar nuclei have been performed. Data were recorded in an exposure of the CHARM detector in an 160 GeV narrow-band beam. The antineutrino flux was determined from the measurements of the pion and kaon flux, and independently from the muon flux measured in the shield; the two methods are found to agree. The neutrino flux was determined from the muon flux ratio forv μ and $$\bar v_\mu $$ runs which was normalized to the antineutrino flux. The cross-section slopes thus determined are $$\begin{gathered} \sigma _T^{\bar v} /E = (0.335 \pm 0.004(stat) \hfill \\ \pm 0.010(syst)).10^{ - 38} cm^2 /(GeV \cdot nucleon) \hfill \\ \sigma _T^v /E = (0.686 \pm 0.002(stat) \hfill \\ \pm 0.020(syst)).10^{ - 38} cm^2 /(GeV \cdot nucleon) \hfill \\ \end{gathered} $$ The momentum sum of the quarks in the nucleon and the ratio of sea quark to total quark momentum are derived from the measurements.

Bose-Einstein correlations in W-pair production at LEP are investigated in a data sample of 629 pb^-1 collected by the L3 detector at centre-of-mass energies of 189-209 GeV. Bose-Einstein correlations between pions within a W decay are observed and found to be in good agreement with those in light-quark Z decay. No evidence is found for Bose-Einstein correlations between hadrons coming from different W's in the same event.

We searched for excited electrons and muons from Z0 decay in the channels ee→eeγ, ee→eeγγ, ee→(e)eγ, ee→μμγ, ee→μμγγ. using the L3 detector at LEP. The lower mass limit for e∗ is 45.0 GeV and for μ∗ 45.3 GeV. The upper limits of ℓℓ∗Z0 and ℓℓ∗γ couplings at 95% CL have been determined up to mℓ∗ close to the Z0 mass.

We have measured the partial width and forward-backward charge asymmetry for the reaction e+e-→Z0→μ+μ-(γ). We obtain a partial width Γμμ of 83.3±1.3(stat)±0.9(sys) MeV and the following values for the vector and axial vector couplings: gv=−0.062−0.015+0.020 and gA=−0.497−0.005+0.005. From our measurement of the partial width and the mass of the Z0 boson we determine the effective electroweak mixing angle, sin2θw=0.232±0.005, and the neutral current coupling strength parameter, ϱ=0.998±0.016.

A method to determine the photopeak position of the γ absorption spectrum of radioactive sources in low light yield scintillators as lead tungstate is discussed. The method is based on the parametrization of both the Compton and photoelectric contributions to the spectrum and it is proven to be reliable and to give stable and precise results.

Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should thus be regarded as complementary. Parameters are given of 4 TeV and 0.5 TeV high luminosity \mumu colliders, and of a 0.5 TeV lower luminosity demonstration machine. We discuss the various systems in such muon colliders, starting from the proton accelerator needed to generate the muons and proceeding through muon cooling, acceleration and storage in a collider ring. Problems of detector background are also discussed.

Avalanche Photodiodes (APD) with improved characteristics were developed by Hamamatsu Photonics for the Electromagnetic Calorimeter of the CMS experiment. This report presents measurements of the latest generation of APDs, which are capable to operate at high gains (∼2000).

Further tests of lead tungstate crystal matrices made in high-energy electron beams in 1996, using new crystals, new APDs and an improved test setup confirm that an energy resolution of better than 0.6% at 100 GeV can be obtained when the longitudinal uniformity of the struck crystal is adequate. Light loss measurements under low dose irradiation are reported. It is shown that there is no loss of energy resolution after irradiation and it is demonstrated that the calibration change due to light loss can be tracked with a precision monitoring system. Successful tests with a preshower device, equipped with a silicon strip detector readout, are also described.

We have measured the partial widths for the three reactions e+e− → Z0 → e+e−, μ+μ−, τ+τ−. The results are Γee = 84.3±1.3 MeV, √ΓeeΓμμ=83.9±1.4 MeV, and √ΓeeΓττ=83.9±1.4 MeV, where the errors are statistical. The systematic errors are estimated to be 1.0 MeV, 0.9 MeV, and 1.4 MeV, respectively. We perform a simultaneous fit to the cross sections for the e+e−→e+e−, μ+μ−, and τ+τ− data, the differential cross section as a function of polar angle for the electron data, and the forward- backward asymmetry for the muon data. We obtain the leptonic partial with Γℓℓ=84.0±0.9 (stat.) MeV. The systematic error is estimated to be 0.8 MeV. Also, we obtain the axial-vector and vector weak coupling constants of charged leptons, gA=−0.500±0.003 and gν=−0.064−0.013+0.017.

From the nucleon structure functions measured by the CHARM Collaboration in inclusive neutrino and antineutrino CC interactions we determined the QCD parameters ΛMS = 310 ± 140 (stat.) ± 70(syst.) MeV using the Furmanski- Petronzio method. With the same method we extrapolated the behaviour of the quark (q + q) and the gluon x-distributions up to Q2 = 10 000 GeV2 using perturbative QCD. The extrapolated structure functions are compared with recent results coming from the two-jet differential cross section in proton-antiproton interactions at √s = 540 GeV and Q2 = 2000 GeV2.

Double-tag events in two-photon collisions are studied using the L3 detector at LEP centre-of-mass energies from s=189 GeV to 209 GeV. The cross sections of the e+e−→e+e−hadrons and γ∗γ∗→hadrons processes are measured as a function of the product of the photon virtualities, Q2=Q21Q22, of the two-photon mass, Wγγ, and of the variable Y=ln(W2γγ/Q2). The average photon virtuality is 〈Q21〉=〈Q22〉=16 GeV2. The results are in agreement with next-to-leading order calculations for the process γ∗γ∗→qq̄ in the interval 2⩽Y⩽5. An excess is observed in the interval 5<Y⩽7, corresponding to Wγγ greater than 40 GeV. This may be interpreted as a contribution of resolved photon QCD processes or the onset of BFKL phenomena.

A search for colour reconnection effects in hadronic decays of W pairs is performed with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The analysis is based on the study of the particle flow between jets associated to the same W boson and between two different W bosons in qq̄qq̄ events. The ratio of particle yields in the different interjet regions is found to be sensitive to colour reconnection effects implemented in some hadronization models. The data are compared to different models with and without such effects. An extreme scenario of colour reconnection is ruled out.

The performance of electromagnetic calorimeter modules made of proton-irradiated PbWO4 crystals has been studied in beam tests. The modules, similar to those used in the Endcaps of the CMS electromagnetic calorimeter (ECAL), were formed from 5×5 matrices of PbWO4 crystals, which had previously been exposed to 24 GeV protons up to integrated fluences between 2.1× 1013 and 1.3× 1014 cm−2. These correspond to the predicted charged-hadron fluences in the ECAL Endcaps at pseudorapidity η = 2.6 after about 500 fb−1 and 3000 fb−1 respectively, corresponding to the end of the LHC and High Luminosity LHC operation periods. The irradiated crystals have a lower light transmission for wavelengths corresponding to the scintillation light, and a correspondingly reduced light output. A comparison with four crystals irradiated in situ in CMS showed no significant rate dependence of hadron-induced damage. A degradation of the energy resolution and a non-linear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The latter is interpreted, through comparison with simulation, as a side-effect of the degradation in light transmission. The experimental results obtained can be used to estimate the long term performance of the CMS ECAL.

We report on measurements of mass and total decay width of the W boson and of triple-gauge-boson couplings, γWW and ZWW, with the L3 detector at LEP. W-pair events produced in e+e− interactions between 161 GeV and 172GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of 21.2 pb−1. The mass and total decay width of the W boson are determined to be MW = 80.75−0.27+0.26(exp.) ± 0.03 (LEP) GeV and ΓW = 1.74−0.78+0.88(stat.) ± 0.25(syst.)GeV, respectively. Limits on anomalous triple-gauge-boson couplings, γWW and ZWW, are determined, in particular −1.5 < δZ < 1.9 (95% CL), excluding vanishing ZWW coupling at more than 95% confidence level.

In 1999, the construction of the electromagnetic calorimeter of the Compact Muon Solenoid (CMS) experiment started. Half of the barrel calorimeter made of 61200 lead tungstate (PWO) crystals will be assembled and tested in the Regional Centre of INFN-ENEA in Rome, Italy. Before assembling, all 30600 PWO crystals will be qualified for scintillation and radiation hardness characteristics by a specially built Automatic Crystal Control System. The measuring techniques for crystal qualification and performances of the automatic system will be discussed in this work.

Bose-Einstein correlations of both neutral and like-sign charged pion pairs are measured in a sample of 2 million hadronic Z decays collected with the L3 detector at LEP. The analysis is performed in the four-momentum difference range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be smaller than that of charged pions. This result is in qualitative agreement with the string fragmentation model.

The cross section of the process e^+ e^- -> Z \gamma\gamma -> qq \gamma \gamma is measured with 215 pb^-1 of data collected with the L3 detector during the final LEP run at centre-of-mass energies around 205 GeV and 207 GeV. No deviation from the Standard Model expectation is observed. The full data sample of 713 pb^-1, collected above the Z resonance, is used to constrain the coefficients of anomalous quartic gauge boson couplings to: -0.02 GeV^-2 < a_0/\Lambda^2 < 0.03 GeV^-2 and -0.07 GeV^-2 < a_c/\Lambda^2 < 0.05 GeV^-2, at 95% confidence level.

Events stemming from the pair-production of Z bosons in e^+e^- collisions are studied using 217.4 pb^-1 of data collected with the L3 detector at centre-of-mass energies from 200 GeV up to 209 GeV. The special case of events with b quarks is also investigated. Combining these events with those collected at lower centre-of-mass energies, the Standard Model predictions for the production mechanism are verified. In addition, limits are set on anomalous couplings of neutral gauge bosons and on effects of extra space dimensions.

We have searched for excited taus from Z0 decay in the channels e+e− → τ∗+τ∗− → τ+τ−γ γ and e+e− → ττ∗ → τ+τ−γ, using the L3 detector at LEP. Using the τ∗ pair production channel, we can exclude a τ∗ up to a mass of 45.5 geV at 95% confidence level. We have also determined upper limits on the ττ∗Z0 and ττ∗γ couplings as a function of mτ∗ up to 89.3 GeV.

A flavour independent search for the CP-even and CP-odd neutral Higgs bosons h and A is performed in 624/pb of data collected with the L3 detector at LEP at centre-of-mass energies between 189 and 209GeV. Higgs boson production through the e^+e^- -> Z h and the e^+e^- ->h A processes is considered and decays of the Higgs bosons into hadrons are studied. No significant signal is observed and 95% confidence level limits on the hZZ and hAZ couplings are derived as a function of the Higgs boson masses. Assuming the Standard Model cross section for the Higgs-strahlung process and a 100% branching fraction into hadrons, a 95% confidence level lower limit on the mass of the Higgs boson is set at 110.3GeV.

A Higgs particle produced in association with a Z boson and decaying into weak boson pairs is searched for in 336.4 1/pb of data collected by the L3 experiment at LEP at centre-of-mass energies from 200 to 209 GeV. Limits on the branching fraction of the Higgs boson decay into two weak bosons as a function of the Higgs mass are derived. These results are combined with the L3 search for a Higgs boson decaying to photon pairs. A Higgs produced with a Standard Model e+e- --> Zh cross section and decaying only into electroweak boson pairs is excluded at 95% CL for a mass below 107 GeV.

Hadron production and lepton-pair production in e+e- collisions are studied with data collected with the L3 detector at LEP at centre-of-mass energies sqrt{s}=192-208GeV. Using a total integrated luminosity of 453/pb, 36057 hadronic events and 12863 lepton-pair events are selected. The cross sections for hadron production and lepton-pair production are measured for the full sample and for events where no high-energy initial-state-radiation photon is emitted prior to the collisions. Lepton-pair events are further investigated and forward-backward asymmetries are measured. Finally, the differential cross sections for electron-positron pair-production is determined as a function of the scattering angle. An overall good agreement is found with Standard Model predictions.

The influence of Gd3+ doping on the optical properties of PbWO4 has been investigated by radio- and thermoluminescence, photoluminescence time decay, optical absorption and light yield measurements. The samples were grown by the Czochralski method and the concentration of Gd in the melt was in the range 0 to 135 mol. ppm. The results demonstrate that a dopant concentration of around 100 ppm in the crystal appears as the best one in order to optimise the scintillation performance of the material.

Single W boson production in electron–positron collisions is studied with the L3 detector at centre-of-mass energies between 192 GeV and 209 GeV. Events with two acoplanar hadronic jets or a single energetic lepton are selected, and the single W cross section is measured. Combining the results with measurements at lower centre-of-mass energies, the ratio of the measured cross section to the Standard Model expectation is found to be 1.12+0.11−0.10±0.03. From all single W data, the WWγ gauge coupling parameter κγ is measured to be 1.116+0.082−0.086±0.068.

Calorimeters have been used extensively for the study of neutrino interactions in the last decade. This paper describes the need for calibration of such calorimeters and how this was realized for the case of the CHARM fine-grained calorimeter. The energy and spatial response of the calorimeter to both hadronic and electromagnetic showers was measured in π and electron beams from 5 to 140 GeV. The results and resolutions are presented.

A calibration study was performed on a prototype of the L3 BGO electromagnetic calorimeter. The accuracy and stability reached is a small fraction of the typical detector resolution.

Inclusive charged hadron production, e+e- -> e+e- h+- X, is studied using 414 pb-1 of data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Single particle inclusive differential cross sections are measured as a function of the particle transverse momentum, pt, and pseudo-rapidity, eta. For p_t < 1.5 GeV, the data are well described by an exponential, typical of soft hadronic processes. For higher pt, the onset of perturbative QCD processes is observed. The pi+- production cross section for pt > 5 GeV is much higher than the NLO QCD predictions.

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.