A search for the Standard Model Higgs boson in LEP2 data recorded with the ALEPH detector is discussed using the topology of events containing a pair of leptons. Combined with other topologies, limits are given for the mass of the Standard Model Higgs boson.
[N10.02] Search for the SM Higgs boson in e^+e^- collisions at \sqrts=170-172 GeV
Isamu Nakamura (Kobe University, Kobe 657, Japan)
The OPAL searches for the Standard Model Higgs boson are updated including, besides the data collected at LEP I energies and at 161 GeV, the most recent data collected in 1996 at centre-of-mass energies of 170 and 172 GeV.
[N10.03] Neural Network b-Tagging for LEP200 Higgs Searches at ALEPH
YiBin Pan (University of Wisconsin-Madison, for the ALEPH Collaboration)
A high-purity method of identifying b-quark jets based on neural network techniques for use in LEP200 Higgs searches at ALEPH is presented. This neural network b-tag combines lifetime-based variables with jet-shape variables and lepton information. The method is described and its performance is discussed in the context of hA and HZ searches in e^+e^- collisions at \sqrts=161 GeV and 172 GeV.
[N10.04] Search for the Standard Model Higgs Boson in e^+e^- Interactions at 160 \leq \sqrts \leq 172 \hbox\rm\ Ge\kern -0.1em V.
L3 Collaboration
We report on the search for the production of the Minimal Standard Model Higgs boson in e^+e^- collisions. The search has been performed with the data collected by the L3 detector at LEP at center of mass energies of 160 - 172 \hbox\rm\ Ge\kern -0.1em V.
[N10.05] A Search for the Standard Model Higgs Boson in the Z\rightarrow \nuøverline\nu Channel at LEP2
Xidong Wu (University of Wisconsin-Madison, for the ALEPH Collaboration)
A search for the Standard Model Higgs boson is performed in \mathrm e^+e^- collisions at \sqrts= 161 and 172 GeV recorded with the ALEPH detector. Evidence of the Standard Model higgsstrahlung process is searched for in the channel Z\rightarrow\nu øverline\nu. The analysis methods are presented and the results are summarized.
[N10.06] Search for neutral Higgs boson production in the channel \bfe^+e^- \rightarrow H\nu\bar\nu with the DELPHI detector at LEP.
Antonio Passeri (Istituto Superiore di Sanita and INFN,Rome,Italy)
A search for the reaction e^+e^- \rightarrow H\nu\bar\nu was performed in the data collected by the DELPHI experiment at centre of mass energies of 161 and 172 GeV. The typical signature of such events consisted in only 2 acoplanar hadronic jets and a large missing energy. Furthermore, the two jets were expected to be originated mostly by a b-\bar\mathrmb quark pair. A good control of the total energy flowing in the detector and a b-tagging algorithm were developed and tested on control data samples. Two approaches were then used to reveal the searched reaction: a sequence of cuts on kinematical and event-shape variables, and a multivariate probabilistic analysis. In both cases a b-tag was applied at the end of the selection. Both approaches were studied on signal events and on several sources of background using Monte Carlo simulations, obtaining compatible results. The signal selection efficiency ranged from 30% to 40% depending on the Higgs boson mass. The amount of remaining background was carefully evaluated and a limit on the Higgs boson mass was extracted.
[N10.07] Search for Standard Model Higgs in Four-Jet Topologies at LEP2
Stephen R. Armstrong (University of Wisconsin - Madison, for the ALEPH Collaboration)
A search for the Standard Model Higgs boson using four-jet event topologies in e^+e^- collisions at \sqrts=161 GeV and 172 GeV recorded with the ALEPH detector is discussed. The analysis methods are reviewed and resulting Higgs mass limits are presented.
[N10.08] Search for production of hA and hZ in 4-jet final states.
Celso Martinez-Rivero (Instituto de Fisica de Cantabria (CSIC-UC),Santander,Spain)
Data collected with the DELPHI detector at 130, 161 and 172 GeV at LEP have been used to search for a signal of neutral Higgs bosons in events with 4 jets in the final state. Since the higgs boson is expected to decay mainly into b \bar b pairs, b tagging techniques have been applied to improve the background rejection. Results and mass limits are presented for both MSSM Higgs bosons production (e^+e^- \rightarrow hA) and standard Higgs produced in association with a Z (e^+e^- \rightarrow hZ).
[N10.09] A Search for Supersymmetric hA at LEP2
Peter A. McNamara (University of Wisconsin-Madison)
A search for the supersymmetric Higgs boson pair, hA, is performed in e^+e^- collisions recorded with the ALEPH detector. The analysis methods and results are presented for data collected at LEP2 energies in 1995 and 1996.
[N10.10] Search for Neutral Higgs Bosons in the General Two Doublet Model and MSSM in e^+e^- Interactions at 160 \leq \sqrts \leq 172 \hbox\rm\ Ge\kern -0.1em V.
L3 Collaboration
We report on the search for the production of neutral Higgs bosons in the frameworks of both a general two doublet model and the MSSM. The search has been performed with the data collected by the L3 detector at LEP at center of mass energies of 160 - 172 \hbox\rm\ Ge\kern -0.1em V in e^+e^- collisions.
This abstract was not submitted electronically.
[N10.12] Single Photon Production at LEP at \bf\sqrts=130--172 GeV
L3 Collaboration
We have searched for single photon events collected with the L3 detector at centre of mass energies from 130 GeV to 172 GeV. >From over 100 candidates, we have calculated the cross sections for the process e^+e^- \rightarrow \nu \bar\nu(\gamma) for various values of the centre of mass energy. >From this data sample we also obtain limits on \chi^0_1 \chi^0_2 production within the framework of the Minimum Supersymmetric Model.
[N10.13] Search for a New Charged Heavy Vector Boson in \bar p p Collisions at \sqrts=1.8~TeV
CDF Collaboration, Hyunsoo Kim (University of Toronto)
We report preliminary results on the search for a new charged heavy vector boson, W^\prime, that decays into a \mu\nu pair. We place mass limits on the W^\prime boson assuming Standard Model couplings.
[N10.14] Search for a Neutral Heavy Scalar in Multijet p\barp Collisions at \sqrts=1.8 TeV with the CDF Detector.
CDF Collaboration, Juan A. Valls, Rocio Vilar (Fermilab)
In this paper we describe a search for neutral heavy scalar particles produced in association with a vector boson using the CDF multijet trigger data sample. The vector boson is required to decay hadronically and two other b-tagged jets are required in a subsample of 4-jet events. No significant deviation from QCD is observed when comparing the invariant mass distributions of tagged dijet systems. The structure of the distributions in data are well understood in terms of QCD background and geometry arguments. The complete CDF multijet data sample corresponding to \sim 110 \,pb^-1 is analyzed. 95% confidence level upper limits on the production cross section of a heavy neutral scalar particle produced in association with a vector boson are set as a function of the new particle mass.
[N10.15] The Dijet Invariant Mass Spectrum in p\barp Collisions at \sqrts = 1.8\,TeV
Björn Hinrichsen (The CDF Collaboration)
The differential dijet invariant mass cross section in p\barp collisions is a steeply falling spectrum. Due to the finite detector resolution, the measured jet energies are different from their true values, i.e. the jet energies are smeared. The data can be described by a convolution of the true spectrum and the detector response. We correct the measured dijet invariant mass spectrum for these effects. The fully corrected data are then directly compared with the parton level predictions of quantum chromodynamics.
[N10.16] Four--Jet Final State Production in e^+e^- Collisions at ALEPH
Shan Jin (University of Wisconsin-Madison, for the ALEPH Collaboration)
Four-jet events recorded with the ALEPH detector in the Fall of 1995 show evidence of an excess over Standard Model expectations. Results of this analysis applied to new data collected in 1996 at \sqrts=161 and 172 GeV are presented.