A. Buijs | McMaster University (original) (raw)
Papers by A. Buijs
Nuclear Physics B - Proceedings Supplements, 2000
This presentation reviews the progress made since the Photon '97 conference on the measurements o... more This presentation reviews the progress made since the Photon '97 conference on the measurements of charmonium states in photon-photon collisions at LEP. New measurements on Xc2-formation are reported by the OPAL and L3 collaborations. New results on T/c formation, in particular a first measurement of the form factor are presented by L3. The DELPHI and L3 experiments give new limits on ~/' ¢ formation. 0920-5632/00/$ -see front matter © 2000 Elsevier Science B.X( PII S0920-5632(00)00168-7
Physics Letters B, 1997
The mean transverse momentum of photons has been determined on an event by event basis in S + Au ... more The mean transverse momentum of photons has been determined on an event by event basis in S + Au collisions at 200 A.GeV from the ratio of the measured electromagnetic transverse energy (/~m) to the photon multiplicity (N~). The average value obtained is similar to that determined for the same system using spectroscopic techniques. The centrality dependence of the measured values are in agreement with the predictions of the VENUS event generator. @ 1997 Published by Elsevier Science B.V.
Physics Letters B, 2000
The D qq -resonance production in central 158 A GeV 208 Pb q 208 Pb collisions at the CERN SPS ha... more The D qq -resonance production in central 158 A GeV 208 Pb q 208 Pb collisions at the CERN SPS has been studied. The D qq production was estimated from the invariant mass spectrum of pp q -pairs by subtracting a mixed event background. The measured D qq abundance is compared with the results from other experiments at lower energies, and with a model calculation assuming thermal and chemical equilibrium. q
Nuclear Physics A, 1999
192c 1:. Peitzmann et aL /Nuclear Physics A661 (1999) 191c-197c Recent results of the WA98 experi... more 192c 1:. Peitzmann et aL /Nuclear Physics A661 (1999) 191c-197c Recent results of the WA98 experiment with Pb induced reactions at 158.A GeV are presented. The scaling properties of the transverse energy and the charged particle multiplicity at midrapidity with the number of participants is studied. Neutral pion spectra are compared to hydrodynamical parameterizations. The analysis of collective flow at target rapidity and at midrapidity is presented. The status of the study of direct photons and the search for isospin fluctuations is discussed.
Computer Physics Communications, 1992
Computer Physics Communications, 1994
TWOGEN samples the transverse-transverse luminosity function for real and virtual photons, then w... more TWOGEN samples the transverse-transverse luminosity function for real and virtual photons, then weights events with any user-supplied cross section TT (!X) i n a \hit or miss" sampling, using a simple method to avoid the singularity at the minimum electron angle # min = 0 . E v ents within dened kinematic limits are accepted and the corresponding cross section is estimated, together with the eective luminosity of the run. Functions implemented for TT include the production cross sections for lepton pairs, for the formation of narrow resonances and for hadron production in tagged, deep inelastic scattering. A comparison is made with an existing Monte Carlo Generator and a simple analytic approximation.
Arxiv preprint hep-ph/ …, 1996
This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the follow... more This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the following topics: structure functions, equivalent photon approximation, tagging conditions etc, soft and semihard physics, large-$p_t$ processes, heavy-quark physics, and exclusive channels.
Physics Letters B, 2000
We present results obtained from a study of the structure of hadronic events recorded by the L3 d... more We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at various centre-of-mass energies. The distributions of event shape variables and the energy dependence of their mean values are measured from 30 GeV to 189 GeV and compared with various QCD models. The energy dependence of the moments of event shape variables is used to test a power law ansatz for the non-perturbative component. We obtain a universal value of the nonperturbative parameter α 0 = 0.537 ± 0.073. From a comparison with resummed O(α 2 s ) QCD calculations, we determine the strong coupling constant at each of the selected energies. The measurements demonstrate the running of α s as expected in QCD with a value of α s (m Z ) = 0.1215 ± 0.0012 (exp) ± 0.0061 (th).
Physics Letters B, 1999
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in ... more The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e + e − collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 −0.14 (stat.) ±0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 −0.07 (stat.) ±0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.
Physics Letters B, 1998
Using the data collected by the L3 experiment at LEP from 1991 to 1995 at energies around the Z m... more Using the data collected by the L3 experiment at LEP from 1991 to 1995 at energies around the Z mass, a measurement of the weak anomalous magnetic dipole moment, a w , and of the weak electric dipole moment, d w , of the lepton is performed.
Physics Letters B, 2000
In a search for the Standard Model Higgs boson, carried out on 212.5 pb −1 of data collected by t... more In a search for the Standard Model Higgs boson, carried out on 212.5 pb −1 of data collected by the L3 detector at the highest LEP centre-of-mass energies, including 116.5 pb −1 above √ s = 206 GeV, an excess of candidates for the process e + e − → Z * → HZ is found for Higgs masses near 114.5 GeV. We present an analysis of our data and the characteristics of our strongest candidates.
Physics Letters B, 1987
We compare the PT dependence of pion, kaon and proton production cross sections in the central ra... more We compare the PT dependence of pion, kaon and proton production cross sections in the central rapidity region in e+eannihilation events and in proton-proton collisions at ISR energies. We find similarities both in the Pr dependence of cross sections and in the particle composition as a function ofpr, in agreement with the hypothesis ofa universaI mechanism of particle production.
Physics Letters B, 2000
An S-Matrix ansatz is used to determine the mass and width of the Z boson, as well as the contrib... more An S-Matrix ansatz is used to determine the mass and width of the Z boson, as well as the contributions of γ/Z interference and Z boson exchange to fermionpair production. For this purpose we use hadron and lepton-pair production cross sections and lepton forward-backward asymmetries that have been measured with the L3 detector at centre-of-mass energies between 87 GeV and 189 GeV.
Physics Letters B, 2004
Anomalous couplings of the Higgs boson are searched for through the processes e + e − → Hγ, e + e... more Anomalous couplings of the Higgs boson are searched for through the processes e + e − → Hγ, e + e − → e + e − H and e + e − → HZ. The mass range 70 GeV < m H < 190 GeV is explored using 602 pb −1 of integrated luminosity collected with the L3 detector at LEP at centre-of-mass energies √ s = 189 − 209 GeV. The Higgs decay channels H → ff, H → γγ, H → Zγ and H → WW ( * ) are considered and no evidence is found for anomalous Higgs production or decay. Limits on the anomalous couplings d, d B , ∆g Z 1 , ∆κ γ and ξ 2 are derived as well as limits on the H → γγ and H → Zγ decay rates.
Physics Letters B, 1998
Local multiplicity uctuations in angular phase space intervals are studied using factorial moment... more Local multiplicity uctuations in angular phase space intervals are studied using factorial moments measured in hadronic events at p s ' 91:2 G e V, which were collected by the l3 detector at lep. Parton shower Monte Carlo programs agree well with the data. On the other hand, rst-order QCD calculations in the Double Leading Log Approximation and the Modied Leading Log Approximation are found to deviate signicantly from the data.
Physics Letters B, 1999
Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to b... more Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between gravitons and Standard Model particles is then predicted. Effects of these new interactions in boson and fermion pair production are searched for in the data sample collected at centre-of-mass energies above the Z pole by the L3 detector at LEP. In addition, the direct production of a graviton associated with a Z boson is investigated. No statistically significant hints for the existence of these effects are found and lower limits in excess of 1 TeV are derived on the scale of this new theory of gravity.
The European Physical Journal C, 2001
ABSTRACT A search for chargino, neutralino and scalar lepton pair-production in e+e- collisions a... more ABSTRACT A search for chargino, neutralino and scalar lepton pair-production in e+e- collisions at the centre-of-mass energy of 189 GeV is performed under the assumptions that R-parity is not conserved in decays and only one of the coupling constants lambda_ijk, lambda'_ijk or lambda''_ijk is non-negligible. No signal is found in a data sample corresponding to an integrated luminosity of 176.4 pb-1. Limits on the production cross sections, on the Minimal Supersymmetric Standard Model parameters and on the masses of the supersymmetric particles are derived.
Nuclear Physics B - Proceedings Supplements, 2000
This presentation reviews the progress made since the Photon '97 conference on the measurements o... more This presentation reviews the progress made since the Photon '97 conference on the measurements of charmonium states in photon-photon collisions at LEP. New measurements on Xc2-formation are reported by the OPAL and L3 collaborations. New results on T/c formation, in particular a first measurement of the form factor are presented by L3. The DELPHI and L3 experiments give new limits on ~/' ¢ formation. 0920-5632/00/$ -see front matter © 2000 Elsevier Science B.X( PII S0920-5632(00)00168-7
Physics Letters B, 1997
The mean transverse momentum of photons has been determined on an event by event basis in S + Au ... more The mean transverse momentum of photons has been determined on an event by event basis in S + Au collisions at 200 A.GeV from the ratio of the measured electromagnetic transverse energy (/~m) to the photon multiplicity (N~). The average value obtained is similar to that determined for the same system using spectroscopic techniques. The centrality dependence of the measured values are in agreement with the predictions of the VENUS event generator. @ 1997 Published by Elsevier Science B.V.
Physics Letters B, 2000
The D qq -resonance production in central 158 A GeV 208 Pb q 208 Pb collisions at the CERN SPS ha... more The D qq -resonance production in central 158 A GeV 208 Pb q 208 Pb collisions at the CERN SPS has been studied. The D qq production was estimated from the invariant mass spectrum of pp q -pairs by subtracting a mixed event background. The measured D qq abundance is compared with the results from other experiments at lower energies, and with a model calculation assuming thermal and chemical equilibrium. q
Nuclear Physics A, 1999
192c 1:. Peitzmann et aL /Nuclear Physics A661 (1999) 191c-197c Recent results of the WA98 experi... more 192c 1:. Peitzmann et aL /Nuclear Physics A661 (1999) 191c-197c Recent results of the WA98 experiment with Pb induced reactions at 158.A GeV are presented. The scaling properties of the transverse energy and the charged particle multiplicity at midrapidity with the number of participants is studied. Neutral pion spectra are compared to hydrodynamical parameterizations. The analysis of collective flow at target rapidity and at midrapidity is presented. The status of the study of direct photons and the search for isospin fluctuations is discussed.
Computer Physics Communications, 1992
Computer Physics Communications, 1994
TWOGEN samples the transverse-transverse luminosity function for real and virtual photons, then w... more TWOGEN samples the transverse-transverse luminosity function for real and virtual photons, then weights events with any user-supplied cross section TT (!X) i n a \hit or miss" sampling, using a simple method to avoid the singularity at the minimum electron angle # min = 0 . E v ents within dened kinematic limits are accepted and the corresponding cross section is estimated, together with the eective luminosity of the run. Functions implemented for TT include the production cross sections for lepton pairs, for the formation of narrow resonances and for hadron production in tagged, deep inelastic scattering. A comparison is made with an existing Monte Carlo Generator and a simple analytic approximation.
Arxiv preprint hep-ph/ …, 1996
This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the follow... more This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the following topics: structure functions, equivalent photon approximation, tagging conditions etc, soft and semihard physics, large-$p_t$ processes, heavy-quark physics, and exclusive channels.
Physics Letters B, 2000
We present results obtained from a study of the structure of hadronic events recorded by the L3 d... more We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at various centre-of-mass energies. The distributions of event shape variables and the energy dependence of their mean values are measured from 30 GeV to 189 GeV and compared with various QCD models. The energy dependence of the moments of event shape variables is used to test a power law ansatz for the non-perturbative component. We obtain a universal value of the nonperturbative parameter α 0 = 0.537 ± 0.073. From a comparison with resummed O(α 2 s ) QCD calculations, we determine the strong coupling constant at each of the selected energies. The measurements demonstrate the running of α s as expected in QCD with a value of α s (m Z ) = 0.1215 ± 0.0012 (exp) ± 0.0061 (th).
Physics Letters B, 1999
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in ... more The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e + e − collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 −0.14 (stat.) ±0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 −0.07 (stat.) ±0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.
Physics Letters B, 1998
Using the data collected by the L3 experiment at LEP from 1991 to 1995 at energies around the Z m... more Using the data collected by the L3 experiment at LEP from 1991 to 1995 at energies around the Z mass, a measurement of the weak anomalous magnetic dipole moment, a w , and of the weak electric dipole moment, d w , of the lepton is performed.
Physics Letters B, 2000
In a search for the Standard Model Higgs boson, carried out on 212.5 pb −1 of data collected by t... more In a search for the Standard Model Higgs boson, carried out on 212.5 pb −1 of data collected by the L3 detector at the highest LEP centre-of-mass energies, including 116.5 pb −1 above √ s = 206 GeV, an excess of candidates for the process e + e − → Z * → HZ is found for Higgs masses near 114.5 GeV. We present an analysis of our data and the characteristics of our strongest candidates.
Physics Letters B, 1987
We compare the PT dependence of pion, kaon and proton production cross sections in the central ra... more We compare the PT dependence of pion, kaon and proton production cross sections in the central rapidity region in e+eannihilation events and in proton-proton collisions at ISR energies. We find similarities both in the Pr dependence of cross sections and in the particle composition as a function ofpr, in agreement with the hypothesis ofa universaI mechanism of particle production.
Physics Letters B, 2000
An S-Matrix ansatz is used to determine the mass and width of the Z boson, as well as the contrib... more An S-Matrix ansatz is used to determine the mass and width of the Z boson, as well as the contributions of γ/Z interference and Z boson exchange to fermionpair production. For this purpose we use hadron and lepton-pair production cross sections and lepton forward-backward asymmetries that have been measured with the L3 detector at centre-of-mass energies between 87 GeV and 189 GeV.
Physics Letters B, 2004
Anomalous couplings of the Higgs boson are searched for through the processes e + e − → Hγ, e + e... more Anomalous couplings of the Higgs boson are searched for through the processes e + e − → Hγ, e + e − → e + e − H and e + e − → HZ. The mass range 70 GeV < m H < 190 GeV is explored using 602 pb −1 of integrated luminosity collected with the L3 detector at LEP at centre-of-mass energies √ s = 189 − 209 GeV. The Higgs decay channels H → ff, H → γγ, H → Zγ and H → WW ( * ) are considered and no evidence is found for anomalous Higgs production or decay. Limits on the anomalous couplings d, d B , ∆g Z 1 , ∆κ γ and ξ 2 are derived as well as limits on the H → γγ and H → Zγ decay rates.
Physics Letters B, 1998
Local multiplicity uctuations in angular phase space intervals are studied using factorial moment... more Local multiplicity uctuations in angular phase space intervals are studied using factorial moments measured in hadronic events at p s ' 91:2 G e V, which were collected by the l3 detector at lep. Parton shower Monte Carlo programs agree well with the data. On the other hand, rst-order QCD calculations in the Double Leading Log Approximation and the Modied Leading Log Approximation are found to deviate signicantly from the data.
Physics Letters B, 1999
Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to b... more Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between gravitons and Standard Model particles is then predicted. Effects of these new interactions in boson and fermion pair production are searched for in the data sample collected at centre-of-mass energies above the Z pole by the L3 detector at LEP. In addition, the direct production of a graviton associated with a Z boson is investigated. No statistically significant hints for the existence of these effects are found and lower limits in excess of 1 TeV are derived on the scale of this new theory of gravity.
The European Physical Journal C, 2001
ABSTRACT A search for chargino, neutralino and scalar lepton pair-production in e+e- collisions a... more ABSTRACT A search for chargino, neutralino and scalar lepton pair-production in e+e- collisions at the centre-of-mass energy of 189 GeV is performed under the assumptions that R-parity is not conserved in decays and only one of the coupling constants lambda_ijk, lambda'_ijk or lambda''_ijk is non-negligible. No signal is found in a data sample corresponding to an integrated luminosity of 176.4 pb-1. Limits on the production cross sections, on the Minimal Supersymmetric Standard Model parameters and on the masses of the supersymmetric particles are derived.