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ABSTRACT: Beam test results of 6- and 10-gap Multi-gap Resistive Plate Chambers (MPRCs) are reported in detail. The corresponding experimental setup at CERN PS-T10 area is explained. The time resolution and detection efficiency of the 6-gap MRPC is around , which is good enough for the TOF detector of STAR experiment, while the 10-gap MRPC has a time resolution below .
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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ABSTRACT: A measurement method is described which allows to accurately track the scintillation light yield changes of lead tungstate crystals. The method has been used to study crystals to which post-growth high-temperature annealing treatments in various atmospheres were applied; it has allowed to select the most radiation resistant crystals and thus to optimize the annealing process. We describe the irradiation facility, irradiation procedure and results obtained. This work has led to the production of radiation resistant 50 mm long crystals and the process is now being extended to 230 mm long crystals.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
B Alpat,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson, [......],
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: A search for exclusive decays of Bd0 and Bs0 mesons has been performed in the channels Bd0 → Jη, Bs0 → Jη, Bd0 → Jπ0 and Bs0 → Jπ0. The data sample consisted of more than three and half million hadrozic 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 × 10−4 on Br(Bd0 → Jπ0) and the first experimental limits: Br(Bd0 → Jη) < 1.2 × 10−3, Br(Bs0 → Jη) < 3.8 × 10−3, Br(Bs0 → Jπ0) < 1.2 × 10−3.
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
Yu Zalite,
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: The reaction hadrons is analysed using data collected by the L3 detector during the LEP runs at and . The cross sections σ(e+e− → e+e− hadrons) and σ(γγ → hadrons) are measured in the interval 5 ≤ Wγγ ≤ 75 GeV. The energy dependence of the σ(γγ → hadrons) cross section is consistent with the universal Regge behaviour of total hadronic cross sections.
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
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ABSTRACT: A measurement of the Ks0 and Λ inclusive production rates and momentum spectra in two- and three-jet events is presented. On the basis of about 3.1 million Z decays collected with the L3 detector at LEP, we observe that the production of these particles is well modelled by string fragmentation.
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
Yu Zalite,
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: We report on a search for R-parity breaking effects due to supersymmetric tau-sneutrino exchange in the reactions e+e− → e+e− and e+e− → μ+μ− at centre-of-mass energies from 91 GeV to 172 GeV, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward-backward asymmetries for these reactions is found. Upper limits for the couplings λ131 and λ232 for sneutrino masses up to are determined from an analysis of the expected effects due to tau sneutrino exchange.
Physics Letters B.
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M Acciarri,
A Adam,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
B Alpat,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio, [......],
J.Y Zeng,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.J Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi
[show abstract]
[hide abstract]
ABSTRACT: A search for supersymmetric particles (charginos, neutralinos, sleptons and stop quarks) has been performed with data collected by the L3 detector during the November 1995 run of the LEP collider at centre of mass energies between 130 and 140 GeV with a total integrated luminosity of 5.1 pb−1. We observe no signal for supersymmetric particles and we set improved exclusion limits on their production cross sections and masses.
Physics Letters B.
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M Acciarri,
P Achard,
O Adriani,
M Aguilar-Benitez,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
M.G Alviggi,
G Ambrosi, [......],
An Zalite,
Yu Zalite,
P Zemp,
Z.P Zhang,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler,
G Zilizi,
M Zöller
[show abstract]
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ABSTRACT: Measurements of the two-photon interaction e+e− → e+e− + hadrons at and are presented. The double-tag events, collected with the L3 detector, correspond to interated luminosities of 140 pb−1 at 91 GeV and 52 pb−1 at 183 GeV. The cross-section of γ∗γ∗ collisions has been measured at 〈Q2〉 = 3.5 GeV2 and 〈Q2〉 = 14 GeV2. The data agree well with predictions based on perturbative QCD, while the Quark Parton Model alone is insufficient to describe the data.
Physics Letters B.
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BES Collaboration,
J.Z Bai,
Y Ban,
J.G Bian,
X Cai,
J.F Chang, H.F Chen,
H.S Chen,
H.X Chen,
Jie Chen, [......],
L Zhou,
N.F Zhou,
K.J Zhu,
Q.M Zhu,
Yingchun Zhu,
Y.C Zhu,
Y.S Zhu,
Z.A Zhu,
B.A Zhuang,
B.S Zou
[show abstract]
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ABSTRACT: In a sample of 58 million J/ψ events collected with the BES II detector, the process J/ψ→γηc is observed in five decay channels: ηc→K+K−π+π−, π+π−π+π−, K±K0Sπ∓ (with K0S→π+π−), φφ (with φ→K+K−) and . From these signals, we determine
Physics Letters B. 578:16-22.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
B Alpat,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson, [......],
Yu Zalite,
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi
[show abstract]
[hide abstract]
ABSTRACT: The results of the searches for neutral Higgs boson production in the process e+e− → Z∗ H0 are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z0 decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L.These results are also interpreted in the framework of the General Two Doublet Model and limits on the nonstandard Higgs boson production through the process e+e− → Z∗h0 are set. A lower limit of 66.7 GeV at 95% C.L. is obtained for the case where the Higgs decays into an invisible final state.
Physics Letters B.
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M Acciarri,
A Adam,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
B Alpat,
J Alcaraz,
J Allaby,
A Aloisio,
G Alverson, [......],
Z Zhang,
Z.P Zhang,
B Zhou,
G.J Zhou,
J.F Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
B.C.C van der Zwaan
[show abstract]
[hide abstract]
ABSTRACT: We have analyzed one-prong τ decays with neutral kaons using the information from a fine-grained hadron calorimeter. The data sample consists of 43 500 Z → τ+τ−(γ) events collected by the L3 detector at LEP in 1991, 1992 and 1993. The following branching fractions are measured: ; and .
Physics Letters B.
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M Acciarri,
A Adam,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
B Alpat,
J Alcaraz,
J Allaby,
A Aloisio,
G Alverson, [......],
Z Zhang,
Z.P Zhang,
B Zhou,
G.J Zhou,
J.F Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
B.C.C van der Zwaan
[show abstract]
[hide abstract]
ABSTRACT: A search for rare charmless decays of Bd0 and Bs0 mesons has been performed in the exclusive channels Bd(s)0 →ηη, Bd(s)0 →ηπ0 and Bd(s)0 →π0π0. The data sample consisted of three million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1994. No candidate event has been observed and the following upper limits at 90% confidence level on the branching ratios have been set: Br(B()d→ηη) <4.1 x 10−4, Br(B()s→ηη) < 1.5 x 10−3, Br(B()d→ηφ()) < 2.5 x 10−4, Br(B()s→ηphi;()) < 1.0 x 10−3, Br(B()d→phi;()phi;()) < 6.0 x 10−5, Br(B()s→phi;()phi;()) < 2.1 x 10−4.These are the first experimental limits on Bd0→ηη and on the Bs0 neutral charmless modes.
Physics Letters B.
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ABSTRACT: Two different kinds of neural networks, feed-forward multi-layer mode with Back-Propagation training algorithm (BP) and Kohonen's Learning Vector Quantization networks (LVQ), are adopted for the identification of e, μ, π particles in Beijing Spectrometer (BES) experiment. The data samples for training and test consist of μ from cosmic ray, e and π from experimental data by strict selection. Although their momentum spectra are non-uniform, the identification efficiencies given by BP are quite uniform versus momentum, and LVQ is little worse. At least in this application BP is shown to be more powerful in pattern recognition than LVQ.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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J.Z Bai,
Y Ban,
J.G Bian,
I Blum,
X Cai,
J.F Chang, H.F Chen,
H.S Chen,
J Chen,
Jie Chen, [......],
B.Q Zhou,
G.M Zhou,
L Zhou,
K.J Zhu,
Q.M Zhu,
Y.C Zhu,
Y.S Zhu,
Z.A Zhu,
B.A Zhuang,
B.S Zou
[show abstract]
[hide abstract]
ABSTRACT: Cross sections for e+e−→ hadrons, π+π−J/ψ, and μ+μ− have been measured in the vicinity of the ψ(2S) resonance using the BESII detector operated at the BEPC. The ψ(2S) total width; partial widths to hadrons, π+π−J/ψ, leptons; and corresponding branching fractions have been determined to be Γt=264±27 keV; Γh=258±26 keV, Γπ+π−J/ψ=85.4±8.7 keV, and Γl=2.44±0.21 keV; and Bh=(97.79±0.15)%, Bπ+π−J/ψ=(32.3±1.4)% , and Bl=(0.93±0.08)%, respectively.
Physics Letters B.
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M Acciarri,
A Adam,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
B Alpat,
J Alcaraz,
J Allaby,
A Aloisio,
G Alverson, [......],
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.J Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
B.C.C van der Zwaan
[show abstract]
[hide abstract]
ABSTRACT: We present a study of the structure of hadronic events recorded by the L3 detector at center-of-mass energies of 130 and 136 GeV. The data sample corresponds to an integrated luminosity of 5 pb−1 collected during the high energy run of 1995. The shapes of the event shape distributions and the energy dependence of their mean values are well reproduced by QCD models. From a comparison of the data with resummed (αs2) QCD calculations, we determine the strong coupling constant to be αs(133 GeV) = 0.107 ± 0.005(exp) ± 0.006(theor).
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
Y Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the average b-hadron lifetime τb at the collider LEP. Using hadronic Z decays collected in the period from 1991 to 1994, two independent analyses have been performed. In the first one, the b-decay position is reconstructed as a secondary vertex of hadronic b-decay particles. The second analysis is an updated measurement of τb using the impact parameter of leptons with high momentum and high transverse momentum. The combined result isIn addition, we measure the average charged b-decay multiplicity 〈nb〉 and the normalized average b-energy 〈xE〉b at LEP to be
Physics Letters B.
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M Acciarri,
P Achard,
O Adriani,
M Aguilar-Benitez,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
M.G Alviggi,
G Ambrosi, [......],
J.B Ye,
S.C Yeh,
An Zalite,
Yu Zalite,
Z.P Zhang,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
G Zilizi,
M Zöller
[show abstract]
[hide abstract]
ABSTRACT: The total and differential cross sections of the process e+e−→nγ with n≥2 are measured using data collected by the L3 experiment at centre-of-mass energies of and . The results are in agreement with the Standard Model expectations. Limits are set on deviations from QED, contact interaction cut-off parameters and masses of excited electrons.
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
Yu Zalite,
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: Events characterised by large hadronic energy and transverse momentum are selected from the data collected by the L3 detector at LEP at centre-of-mass energies between 161 and 172 GeV, corresponding to an integrated luminosity of 21 pb−1. The visible mass and the missing mass distributions of the selected events are consistent with those expected from Standard Model processes. This result is combined with that from data taken at the Z resonance to set an upper limit on the production rate and decay into invisible final states of a non-minimal Higgs boson, as a function of the Higgs mass. Assuming the non-minimal Higgs production cross section to be the same as for the Standard Model Higgs boson and the decay branching fraction into invisible final states to be 100%, a Higgs mass lower limit of 69.6 GeV is derived at 95% confidence level.
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
Yu Zalite,
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be 0.61−0.33+0.43 ± 0.05 pb at the centre of mass energy , consistent with the Standard Model expectation. From this measurement the following limits on the anomalo γWW gauge couplingsare derived at 95% CL: −3.6 < Δκγ < 1.5 and −3.6 < λγ < 3.6.
Physics Letters B.
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M Acciarri,
O Adriani,
M Aguilar-Benitez,
S Ahlen,
J Alcaraz,
G Alemanni,
J Allaby,
A Aloisio,
G Alverson,
M.G Alviggi, [......],
Yu Zalite,
P Zemp,
Y Zeng,
Z Zhang,
Z.P Zhang,
B Zhou,
G.Y Zhu,
R.Y Zhu,
A Zichichi,
F Ziegler
[show abstract]
[hide abstract]
ABSTRACT: We report on measurements of e+e− annihilation into hadrons and lepton pairs. The data have been taken with the L3 detector at LEP at center-of-mass energies between 161 GeV and 172 GeV. In a data sample corresponding to 21.2 pb−1 of integrated luminosity 2728 hadronic and 868 lepton-pair events are selected. The measured cross sections and leptonic forward-backward asymmetries agree well with the Standard Model predictions.
Physics Letters B.
