-
D. Abbaneo,
G. Abbiendi,
M. Abbrescia,
S. Abdullin,
A. Abdulsalam,
B.S. Acharya,
D. Acosta,
J.G. Acosta,
A. Adair,
W. Adam, [......],
M.H. Zoeller,
O. Zorba,
P. Zotto,
W. Zou,
G. Zumerle,
M. Zupan,
A. Zuranski,
R. Zuyeuski,
M. Zvada,
P. Zych
[show abstract]
[hide abstract]
ABSTRACT: The Higgs boson was postulated nearly five decades ago within the framework of the standard model of particle physics and
has been the subject of numerous searches at accelerators around the world. Its discovery would verify the existence of a
complex scalar field thought to give mass to three of the carriers of the electroweak force—the W+, W–, and Z0 bosons—as well as to the fundamental quarks and leptons. The CMS Collaboration has observed, with a statistical significance
of five standard deviations, a new particle produced in proton-proton collisions at the Large Hadron Collider at CERN. The
evidence is strongest in the diphoton and four-lepton (electrons and/or muons) final states, which provide the best mass resolution
in the CMS detector. The probability of the observed signal being due to a random fluctuation of the background is about 1
in 3 × 106. The new particle is a boson with spin not equal to 1 and has a mass of about 1.25 giga–electron volts. Although its measured
properties are, within the uncertainties of the present data, consistent with those expected of the Higgs boson, more data
are needed to elucidate the precise nature of the new particle.
Science 12/2012; 338(6114):1569-1575. · 31.20 Impact Factor
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The CMS Collaboration,
S Chatrchyan,
G Hmayakyan,
V Khachatryan,
A M Sirunyan,
W Adam,
T Bauer,
T Bergauer,
H Bergauer,
M Dragicevic, [......],
G Abdullaeva,
A Avezov,
M I Fazylov,
E M Gasanov,
A Khugaev,
Y N Koblik,
M Nishonov,
K Olimov,
A Umaraliev,
B S Yuldashev
[show abstract]
[hide abstract]
ABSTRACT: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 1034 cm−2 s−1 (1027 cm−2 s−1). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (|η| ≤ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.
Journal of Instrumentation 08/2008; 3(08):S08004. · 1.87 Impact Factor
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D Acosta,
G Apollinari,
K Arisaka,
V. Barasko,
N. Bondar,
R. Breedon,
A. Bujak,
B Bylsma,
N. Chester,
D Chrisman, [......],
V. Souvorov,
V. Sytnik,
B Tannenbaum,
N Terentyev,
S.M. Tripathi,
S. Villa,
A Volkov,
A Vorobyov,
V. Yarba, G Zilizi
[show abstract]
[hide abstract]
ABSTRACT: Presented are the main design features and performance results of the cathode strip chambers (CSCs) for the CMS Endcap Muon System. The six-plane structure of these chambers yields a spatial resolution of about 80 μm, essentially uniform and independent of the strip width (up to 16 mm, which is unusually wide for the cathode-to-anode wire distance of 5 mm). In addition, the net spatial resolution of about one-tenth of the strip width at the hardware trigger level (300ns) is obtained using a simple network of comparators. The time resolution achieved at the trigger level is ∼4ns (RMS) that allows unambiguous tagging of bunch crossing occurring every 25 ns. Aging tests, including those obtained with a recirculating gas system, showed only minor aging effects. The aging studies were performed with large-scale chambers; 700 m of wire were irradiated for a dose up to 0.4 C/cm of the total accumulated charge.
Nuclear Science Symposium Conference Record, 2002 IEEE; 12/2002
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[show abstract]
[hide abstract]
ABSTRACT: The process e+ e- -> n gamma with n>=2 is studied at
centre-of-mass energies ranging from \root(s)=192 to 208 GeV. The data
sample corresponds to a total integrated luminosity of 427 1/pb. The
total and differential cross sections are found to be in agreement with
the QED expectations. Using all the data collected with the L3 detector
above the Z pole, limits on deviations from QED, excited electrons,
contact interactions, extra space dimensions and excited spin-3/2
leptons are set.
Physics Letters B 03/2002; 531:28-38. · 3.95 Impact Factor
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A. A. Vorobyov,
M. Wadhwa,
W. Wallraff,
X. L. Wang,
Z. M. Wang,
M. Weber,
P. Wienemann,
H. Wilkens,
S. Wynhoff,
L. Xia, [......],
Y. Zalite,
Z. P. Zhang,
J. Zhao,
G. Y. Zhu,
R. Y. Zhu,
H. L. Zhuang,
A. Zichichi, G. Zilizi,
B. Zimmermann,
M. Z. Zoller
[show abstract]
[hide abstract]
ABSTRACT: The process e+e- -> W+ W- gamma 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 GeV to 207
GeV, are presented. The W+W- gamma 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- --> nu nubar gamma
gamma.
Physics Letters B 01/2002; 527:29-38. · 3.95 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Open charm production in gamma-gamma collisions is studied with data
collected at e+e- centre-of-mass energies from 189 GeV to 202 GeV
corresponding to a total integrated luminosity of 410 pb-1. The charm
cross section sigma(gamma gamma ---> c c~ X) is measured for the
first time as a function of the two-photon centre-of-mass energy in the
interval from 5 GeV to 70 GeV and is compared to NLO QCD calculations.
Physics Letters B 07/2001; 514:19-28. · 3.95 Impact Factor
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Collaboration,
M. Acciarri,
P. Achard,
O. Adriani,
M. Aguilar-Benitez,
J. Alcaraz,
G. Alemanni,
J. Allaby,
A. Aloisio,
M. G. Alviggi, [......],
S. C. Yeh,
A. Zalite,
Y. Zalite,
Z. P. Zhang,
G. Y. Zhu,
R. Y. Zhu,
A. Zichichi, G. Zilizi,
B. Zimmermann,
M. Zöller
[show abstract]
[hide abstract]
ABSTRACT: The production of c and b quarks /γγ collisions is studied
with the L3 detector at LEP with 410 pb-1 of data, collected
at centre-of-mass energies from 189 GeV to 202 GeV. Hadronic final
states containing c and b quarks are identified by detecting electrons
or muons from their semileptonic decays. The cross sections
σ(e+e--->e+e-
cc¯X) and
σ(e+e--->e+e-
bb¯X) are measured and compared to next-to-leading order
perturbative QCD calculations. The cross section of b production is
measured in /γγ collisions for the first time. It is in
excess of the QCD prediction by a factor of three.
Physics Letters B 02/2001; 503:10-20. · 3.95 Impact Factor
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Collaboration,
M. Acciarri,
P. Achard,
O. Adriani,
M. Aguilar-Benitez,
J. Alcaraz,
G. Alemanni,
J. Allaby,
A. Aloisio,
M. G. Alviggi, [......],
S. C. Yeh,
An. Zalite,
Yu. Zalite,
Z. P. Zhang,
G. Y. Zhu,
R. Y. Zhu,
A. Zichichi, G. Zilizi,
B. Zimmermann,
M. Zöller
[show abstract]
[hide abstract]
ABSTRACT: The data collected by the L3 experiment at LEP at a centre-of-mass
energy of 188.6 GeV are used to measure the W-pair production cross
section and the W-boson decay branching fractions. These data correspond
to an integrated luminosity of 176.8 pb-1. The total cross
section for W-pair production, combining all final states, is measured
to be σWW=16.24+/-0.37 (stat.)+/-0.22 (syst.) pb.
Including our data collected at lower centre-of-mass energies, the
hadronic branching fraction of the W-boson is determined to be
/B(W-->qq)=[68.20+/-0.68 (stat.)+/-0.33 (syst.)]%. The results agree
with the Standard Model predictions.
Physics Letters B 11/2000; 496:19-33. · 3.95 Impact Factor
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H. J. Yang,
M. Yang,
J. B. Ye,
S. C. Yeh,
An. Zalite,
Yu. Zalite,
Z. P. Zhang,
G. Y. Zhu,
R. Y. Zhu,
A. Zichichi, G. Zilizi,
B. Zimmermann,
M. Zoller
[show abstract]
[hide abstract]
ABSTRACT: We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between
particles from a single W decay in good agreement with those from a
light-quark Z decay sample. We investigate their possible existence
between particles coming from different W's. No evidence for such
inter-W BEC is found.
Physics Letters B 10/2000; 493:233-248. · 3.95 Impact Factor
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M. Acciarri,
A. Adam,
O. Adriani,
S. Ahlen,
J. Alcaraz,
G. Ambrosi,
V. Andreev,
E. Babucci,
L. Baksay,
A. Baschirotto, [......],
G. Trowitzsch,
H. Tuchscherer,
M. Van Hoek,
G. Viertel,
H. Vogt,
R. Weill,
J. Xu,
S.C. Yeh,
B. Zhou, G. Zilizi
[show abstract]
[hide abstract]
ABSTRACT: The 1994 running experience with the L3 Silicon Microvertex Detector is described; in particular we report on the detector performances observed during the year (namely the DAQ and detection efficiency and the signal to noise ratio) and on the reduction of the noise affecting the detector.
Nuclear Physics B - Proceedings Supplements 44:296-302. · 0.88 Impact Factor
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P. Achard,
O Adriani,
M. Aguilar-Benitez,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
H Anderhub,
V P Andreev, [......],
Y. Zalite,
Z P Zhang,
J Zhao,
G Y Zhu,
R Y Zhu,
H L Zhuang,
A. Zichichi, G Zilizi,
B. Zimmermann,
M. Zoller
[show abstract]
[hide abstract]
ABSTRACT: The charged-particle multiplicity distribution is measured for all hadronic events as well as for light-quark and b-quark events produced in e(+)e(-) collisions at the Z pole. Moments of the charged-particle multiplicity distributions are calculated. The H-q moments of the multiplicity distributions are studied, and their quasi-oscillations as a function of the rank of the moment are investigated. (C) 2003 Published by Elsevier B.V.
Physics Research Publications.
-
G. L. Bayatian,
S. Chatrchyan,
G Hmayakyan,
A M Sirunyan,
W Adam,
T Bergauer,
M Dragicevic,
J. Ero,
M Friedl,
R. Fruehwirth, [......],
D Reeder,
W.H. Smith,
D. Wenman,
G. S. Atoyan,
S Dhawan,
V. Issakov,
H Neal,
A. Poblaguev,
M. E. Zeller,
B. S. Yuldashev
[show abstract]
[hide abstract]
ABSTRACT: CMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider ( LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007. The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking - through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start- up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb(-1) or less. The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, B-s production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb(-1) to 30 fb(-1). The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z(0) boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated. This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2-6 describe examples of full analyses, with photons, electrons, muons, jets, missing E-T, B-mesons and tau's, and for quarkonia in heavy ion collisions. Chapters 7-15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model.
Physics Research Publications.
-
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: A first measurement of the cross section of the process e+e−→Zγγ is reported using a total integrated luminosity of 231 pb−1 collected with the L3 detector at centre-of-mass energies of and . By selecting hadronic events with two isolated photons the e+e−→Zγγ cross section is measured to be at and at . The measurements are consistent with Standard Model expectations. Limits on Quartic Gauge Boson Couplings a0/Λ2 and ac/Λ2 of and are derived at 95% confidence level.
Physics Letters B.
-
D Acosta,
A Adam,
V Andreev,
G Apollinari,
Y. Baek,
K Banicz,
V. Barashko,
E Barberis,
P Bartalini,
I Bloch, [......],
A. Vorobyev,
D Wang,
G. L. Williams,
V. Yatsura,
A Zarubin,
W Zhao,
Y Zheng,
G. Zhmakin,
Z Zhu, G Zilizi
[show abstract]
[hide abstract]
ABSTRACT: In the Compact Muon Solenoid (CMS) experiment, muon detection in the forward direction is accomplished by cathode strip chambers (CSC). These detectors identify muons, provide a fast muon trigger, and give a precise measurement of the muon trajectory. There are 468 six-plane CSCs in the system. The efficiency of finding muon trigger primitives (muon track segments) was studied using 36 CMS CSCs and cosmic ray muons during the Magnet Test and Cosmic Challenge (MTCC) exercise conducted by the CNIS experiment in 2006. In contrast to earlier studies that used muon beams to illuminate a very small chamber area (<0.01 m(2))(,) results presented in this paper were obtained by many installed CSCs operating in situ over an area of approximate to 23 m(2) as a part of the CMS experiment. The efficiency of finding two-dimensional trigger primitives within six-layer chambers was found to be 99.93 +/- 0.03%. These segments, found by the CSC electronics within 800 ns after the passing of a muon through the chambers, are the input information for the Level-1 muon trigger and, also, are a necessary condition for chambers to be read out by the Data Acquisition System. (C) 2008 Elsevier B.V. All rights reserved.
Physics Research Publications.
-
M Acciarri,
P. Achard,
O Adriani,
M. Aguilar-Benitez,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
G Ambrosi, [......],
S C Yeh,
J M You,
A Zalite,
Yu Zalite,
Z P Zhang,
G Y Zhu,
R Y Zhu,
A. Zichichi, G Zilizi,
M. Zoller
[show abstract]
[hide abstract]
ABSTRACT: We report on measurements of hadronic and leptonic cross sections and leptonic forward-backward asymmetries performed with the L3 detector in the years $1993-95$.A total luminosity of 103 pb$^{-1}$ was collected at centre-of-mass energies $\sqrt{s} \approx m_\mathrm{Z}$ and $\sqrt{s} \approx m_\mathrm{Z} \pm 1.8$ GeVwhich corresponds to 2.5 million hadronic and 245 thousand leptonic events selected.These data lead to a significantly improved determination of Z parameters.From the total cross sections, combined with our measurements in $1990-92$,we obtain the final results:%%%\begin{eqnarr ay*} m_\mathrm{Z} = 91189.8 \pm 3.1\ \mathrm{MeV} \, , & & \Gamma_\mathrm{Z} = 2502.4 \pm 4.2\ \mathrm{MeV} \, , \\ \Gamma_\mathrm{had} = 1741.1 \pm 3.8\ \mathrm{MeV} \, , & & \Gamma_\ell = 84.14 \pm 0.17\ \mathrm{MeV} \,. \label{eq:Zpara_abstract}\end{eqnarray*}%%%An invisible width of $\Gamma_\mathrm{inv} = 499.1 \pm 2.9$ MeV is derived which in the Standard Model yields for the numberof light neutrino species $N_\nu = 2.978 \pm 0.014$.Adding our results on the leptonic forward-backward asymmetries and thetau polarisation, the effective vector and axial-vector coupling constants of the neutral weak current to charged leptons are determined to be $\bar{g}_{\mathrm{V}}^\ell = -0.0397\pm 0.0017$ and $\bar{g}_{\mathrm{A}}^\ell = -0.50153 \pm 0.00053$.Including our measurements of the Z $\rightarrow \mathrm{b}\bar{\mathrm{b}}$ forward-backward and quark charge asymmetries a value for the effective electroweakmixing angle of $\sin^2\!\overline{\theta}_{\mathrm{W}} = 0.23093 \pm 0.00066$ is derived. All these measurements are in good agreement with the Standard Modelof electroweak interactions.Using all our measurements of electroweak observables an upper limit on the mass of the Standard Model Higgs boson of $m_\mathrm{H} 133 $ GeV is set at 95\% confidence level.
-
M Acciarri,
P. Achard,
O Adriani,
M. Aguilar-Benitez,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
G Ambrosi, [......],
J M You,
A Zalite,
P Zemp,
Z P Zhang,
G Y Zhu,
R Y Zhu,
A. Zichichi,
F Ziegler, G Zilizi,
M. Zoeller
[show abstract]
[hide abstract]
ABSTRACT: Study of Neutral--Current Four--Fermion and ZZ \\ Production in $\rm e^+ e^-$ Collisions at $\rm \sqrt{s}=$ 183 GeV A study of neutral--current four--fermion processes is performed using a data sample corresponding to 55.3~pb$^{-1}$ of integrated luminosity collected by the L3 detector at LEP at an average centre--of--mass energy of $183~\GeV$. The neutral--current four--fermion cross sections for final states with a pair of charged leptons plus jets and with four charged leptons are measured to be consistent with the Standard Model predictions. Events with fermion pair masses close to the Z boson mass are selected in all observable final states and the ZZ production cross section is measured to be %\begin{center} $\rm \sigma_{ZZ} = 0.30 ^{+0.22\,\,+0.07}_{-0.16\,\,-0.03}\,\mathrm{pb},$ %\end{center} in agreement with the Standard Model expectation. No evidence for the existence of anomalous triple gauge boson ZZZ and ZZ$\gamma$ couplings is found and limits on these couplings are set.
-
M Acciarri,
P. Achard,
O Adriani,
M. Aguilar-Benitez,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
G Ambrosi, [......],
A Zalite,
Yu Zalite,
P Zemp,
Z P Zhang,
G Y Zhu,
R Y Zhu,
A. Zichichi,
F Ziegler, G Zilizi,
M. Zoeller
[show abstract]
[hide abstract]
ABSTRACT: Measurements of the two-photon interaction e+e- --> e+e- hadrons at sqrt(s) = 91 GeV and sqrt(s) = 183 GeV are presented. The double-tag events, collected with the L3 detector, correspond to integrated luminosities of 140 pb-1 at 91 GeV and 52 pb-1 at 183 GeV. The cross-section of gamma*gamma* collisions has been measured at Q^2 = 3.5 GeV^2 and Q^2 = 14 GeV^2. The data agree well with predictions based on perturbative QCD, while the Quark Parton Model alone is insufficient to describe the data.
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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, [......],
A Zalite,
Yu Zalite,
P Zemp,
Y Zeng,
Z P Zhang,
G Y Zhu,
R Y Zhu,
A. Zichichi,
F Ziegler, G Zilizi
[show abstract]
[hide abstract]
ABSTRACT: The time-integrated $\mathrm{B}^{0}\bar{\mathrm{B}}^{0}$ mixing parameter and the forward-backward charge asymmetry in the process $\mathrm{e}^{+}\mathrm{e}^{-} \rightarrow \mathrm{b}\bar{\mathrm{b}}$ are measured in hadronic \Z events containing prompt muons or electrons, collected by the L3 experiment in the years 1990 to 1995. The total sample of 3.3 million hadronic $\mathrm{Z}$ events with a mean centre-of-mass energy of 91.26 GeV yields: \begin{eqnarray*} \mbox{$A_{\mathrm{FB}}^{\mathrm{b} }$} & = & 0.0960 \pm 0.0066(stat.) \pm 0.0033(sys.) \,, \\ %corel-6 \mbox{$\chi_{\mathrm{b}}$} & = & 0.1192 \pm 0.0068(stat.) \pm 0.0051(sys.) \,. % \end{eqnarray*} %%% %%% %%% %%% This asymmetry measurement together with measurements at energies away from the $\mathrm{Z}$ pole energy yield a pole asymmetry and corresponding effective electroweak mixing angle of: \begin{eqnarray*} \mbox{$A_{\mathrm{FB}}^{0,\mathrm{b}}$} & = & 0.1015 \pm 0.0064(stat.) \pm 0.0035(sys.) \,, \\ %corel-6.nb \mbox{$\sin^{2}\bar{\theta}_{\mathrm{W}}$} & = & 0.2318 \pm 0.0013 \, .\\ %sin2tw-3.nb \end{eqnarray*}
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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, [......],
S C Yeh,
A Zalite,
Yu Zalite,
Z P Zhang,
G Y Zhu,
R Y Zhu,
A. Zichichi,
F Ziegler, G Zilizi,
M. Zoeller
[show abstract]
[hide abstract]
ABSTRACT: We report the result of a search for charginos and neutralinos, in $\rm e^+e^-$ collisions at 189 GeV centre-of-mass energy at LEP. No evidence for such particles is found in a data sample of 176 pb$^{-1}$. Improved upper limits for these particles are set on the production cross sections. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived, as well as new lower limits on the masses of these supersymmetric particles. Under the assumptions of common gaugino and scalar masses at the GUT scale, we set an absolute lower limit on the mass of the lightest neutralino of 32.5 GeV and on the mass of the lightest chargino of 67.7 GeV.
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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,
A Zalite,
Yu Zalite,
Z P Zhang,
G Y Zhu,
R Y Zhu,
A. Zichichi, G Zilizi,
M. Zoller
[show abstract]
[hide abstract]
ABSTRACT: A search for a Higgs boson decaying into invisible particles is performed using the datacollected at LEP by the L3 experiment at centre-of-mass energies of$183\gev{}$ and $189\gev{}$. The integrated luminosities are respectively 55.3~\pb{} and 176.4~\pb{}.The observed candidates are consistent with the expectations from StandardModel processes.In the hypothesis that the production cross section of this Higgs bosonequals the Standard Model one and the branching ratio into invisibleparticles is $100\%$, a lower masslimit of $89.2\gev{}$ is set at $95\%$ confidence level.
