projected expansion of the Imperial College at the behest of the Government. The opportunities th... more projected expansion of the Imperial College at the behest of the Government. The opportunities thus presented appealed to his imagination and he threw himself into planning and directing with that energy which he always gave so lavishly. It was a great joy to him when, in 1953, he was elected vice-chancellor of the University of London, a post which his father, Prof. M. J.M. Hill, had held many years earlier. Some of his friends feared that the responsibilities of this post added to those he already carried might prove too great a strain and, in fa.ct, his health obliged him to resign the vicechancellorship before the completion of his year of office. His career before he joined the Imperial College will be recorded elsewhere, and it is only possible to say here that the ability, enthusiasm, capacity for hard work, and keenness in everything he did, which produced an outstandingly distinguished R.A.F. officer, were all brought to the service of the College and the University. All these qualities and one other, which will be remembered most by all of us, that of charming friendliness, combined to give the College a rector who will always be remembered with deep affection.
This paper describes a search for the Standard Model Higgs boson using data from e + e collisions... more This paper describes a search for the Standard Model Higgs boson using data from e + e collisions collected at center-of-mass energies of 161, 170 and 172 GeV by the OPAL detector at LEP. The data collected at these energies correspond to integrated luminosities of 10.0, 1.0 and 9.4 pb 1 , respectively. The search is sensitive to the main nal states from the process in which the Higgs boson is produced in association with a fermion anti-fermion pair, namely four jets, two jets with missing energy, and two jets produced together with a pair of electron, muon or tau leptons. One candidate event is observed, in agreement with the Standard Model background expectation. In combination with previous OPAL searches at center-of-mass energies close to the Z 0 resonance and the revised previous OPAL searches at 161 GeV , we derive a l o w er limit of 69.4 GeV for the mass of the Standard Model Higgs boson at the 95% condence level.
We report on measurements of the mass and total decay width of the W boson with the L3 detector a... more We report on measurements of the mass and total decay width of the W boson with the L3 detector at LEP. W-pair events produced in e + e − interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of 76.7 pb −1. Combining all final states in W-pair production, the mass and total decay width of the W boson are determined to be M W = 80.61 ± 0.15 GeV and Γ W = 1.97 ± 0.38 GeV, respectively.
The Standard Model Higgs boson is searched for in 233.2 pb-1 of data collected by the L3 detector... more The Standard Model Higgs boson is searched for in 233.2 pb-1 of data collected by the L3 detector at centre of mass energies from 192 GeV to 202 GeV. These data are consistent with the expectations of Standard Model processes and no evidence of a Higgs signal is observed. A lower limit on the mass of the Standard Model Higgs boson of 107.0 GeV is set at the 95% confidence level.
Constraints are presented on the total width of the recently discovered Higgs boson, Γ H , using ... more Constraints are presented on the total width of the recently discovered Higgs boson, Γ H , using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb −1 at a centre-of-mass energy √ s = 7 TeV and 19.7 fb −1 at √ s = 8 TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of Γ H < 22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of m H = 125.6 GeV.
Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions ... more Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions at √ s = 7 TeV, undertaken with the CMS experiment at the LHC. The b quarks are assumed to decay exclusively to tW. The b b → tW − tW + process can be identified by its distinctive signatures of three leptons or two leptons of same charge, and at least one b-quark jet. Using a data sample corresponding to an integrated luminosity of 4.9 fb −1 , observed events are compared to the standard model background predictions, and the existence of b quarks having masses below 611 GeV/c 2 is excluded at 95% confidence level.
Doubly-charged Higgs bosons are searched for in e + e − collision data collected with the L3 dete... more 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.
A search for a heavy gauge boson W has been conducted by the CMS experiment at the LHC in the dec... more A search for a heavy gauge boson W has been conducted by the CMS experiment at the LHC in the decay channel with an electron and large transverse energy imbalance E miss T , using proton-proton collision data corresponding to an integrated luminosity of 36 pb −1. No excess above standard model expectations is seen in the transverse mass distribution of the electron-E miss T system. Assuming standard-model-like couplings and decay branching fractions, a W boson with a mass less than 1.36 TeV/c 2 is excluded at 95% confidence level.
A search for supersymmetry is presented using a sample of events with b jets and missing transver... more A search for supersymmetry is presented using a sample of events with b jets and missing transverse momentum. The search uses a data sample of proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 35 pb −1 , collected with the CMS detector. A total of 0.33 +0.43 −0.33 (stat.) ± 0.13 (syst.) events is predicted, using control samples in the data, to arise from standard model processes, and one event is observed in the data. Upper limits are set at the 95% confidence level on the cross sections of benchmark supersymmetric models.
A search for new physics is presented based on an event signature of at least three jets accompan... more A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 pb −1 collected in proton-proton collisions at √ s = 7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets.
A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heav... more 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.
Combined results are reported from searches for the standard model Higgs boson in proton-proton c... more Combined results are reported from searches for the standard model Higgs boson in proton-proton collisions at √ s = 7 TeV in five Higgs boson decay modes: γγ, bb, ττ, WW, and ZZ. The explored Higgs boson mass range is 110-600 GeV. The analysed data correspond to an integrated luminosity of 4.6-4.8 fb −1. The expected excluded mass range in the absence of the standard model Higgs boson is 118-543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127-600 GeV at 95% CL, and in the mass range 129-525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1σ, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance ≥3.1σ anywhere in the search range 110-600 (110-145) GeV is estimated to be 1.5σ (2.1σ). More data are required to ascertain the origin of this excess.
A search for a Higgs boson produced in e + e − collisions in association with a Z boson and decay... more 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 −1. 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.
Single top production in e + e − annihilations is searched for in data collected by the L3 detect... more 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.
Neutral-current four-fermion production, e + e − → fff ′f ′ , is studied in 0.7 fb −1 of data col... more Neutral-current four-fermion production, e + e − → fff ′f ′ , is studied in 0.7 fb −1 of data collected with the L3 detector at LEP at centre-of-mass energies √ s = 183 − 209 GeV. Four final states are considered: qqνν, qqℓ + ℓ − , ℓ + ℓ − ℓ ′+ ℓ ′− and ℓ + ℓ − νν, where ℓ denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e + e − → Zγ * → fff ′f ′ process is studied and its total cross section at the average centre-of-mass energy √ s = 196.6 GeV is found to be 0.29 ± 0.05 ± 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qqℓ + ℓ − final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found.
The double-radiative process e + e − → Zγγ → qqγγ where the two hard photons escape detection at ... more The double-radiative process e + e − → Zγγ → qqγγ where the two hard photons escape detection at low polar angles into opposite directions, is studied in 0.62 fb −1 of data collected with the L3 detector at LEP at centre-of-mass energies between 188.6 GeV and 209.2 GeV. The cross sections are measured and found to be consistent with the Standard Model expectations.
projected expansion of the Imperial College at the behest of the Government. The opportunities th... more projected expansion of the Imperial College at the behest of the Government. The opportunities thus presented appealed to his imagination and he threw himself into planning and directing with that energy which he always gave so lavishly. It was a great joy to him when, in 1953, he was elected vice-chancellor of the University of London, a post which his father, Prof. M. J.M. Hill, had held many years earlier. Some of his friends feared that the responsibilities of this post added to those he already carried might prove too great a strain and, in fa.ct, his health obliged him to resign the vicechancellorship before the completion of his year of office. His career before he joined the Imperial College will be recorded elsewhere, and it is only possible to say here that the ability, enthusiasm, capacity for hard work, and keenness in everything he did, which produced an outstandingly distinguished R.A.F. officer, were all brought to the service of the College and the University. All these qualities and one other, which will be remembered most by all of us, that of charming friendliness, combined to give the College a rector who will always be remembered with deep affection.
This paper describes a search for the Standard Model Higgs boson using data from e + e collisions... more This paper describes a search for the Standard Model Higgs boson using data from e + e collisions collected at center-of-mass energies of 161, 170 and 172 GeV by the OPAL detector at LEP. The data collected at these energies correspond to integrated luminosities of 10.0, 1.0 and 9.4 pb 1 , respectively. The search is sensitive to the main nal states from the process in which the Higgs boson is produced in association with a fermion anti-fermion pair, namely four jets, two jets with missing energy, and two jets produced together with a pair of electron, muon or tau leptons. One candidate event is observed, in agreement with the Standard Model background expectation. In combination with previous OPAL searches at center-of-mass energies close to the Z 0 resonance and the revised previous OPAL searches at 161 GeV , we derive a l o w er limit of 69.4 GeV for the mass of the Standard Model Higgs boson at the 95% condence level.
We report on measurements of the mass and total decay width of the W boson with the L3 detector a... more We report on measurements of the mass and total decay width of the W boson with the L3 detector at LEP. W-pair events produced in e + e − interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of 76.7 pb −1. Combining all final states in W-pair production, the mass and total decay width of the W boson are determined to be M W = 80.61 ± 0.15 GeV and Γ W = 1.97 ± 0.38 GeV, respectively.
The Standard Model Higgs boson is searched for in 233.2 pb-1 of data collected by the L3 detector... more The Standard Model Higgs boson is searched for in 233.2 pb-1 of data collected by the L3 detector at centre of mass energies from 192 GeV to 202 GeV. These data are consistent with the expectations of Standard Model processes and no evidence of a Higgs signal is observed. A lower limit on the mass of the Standard Model Higgs boson of 107.0 GeV is set at the 95% confidence level.
Constraints are presented on the total width of the recently discovered Higgs boson, Γ H , using ... more Constraints are presented on the total width of the recently discovered Higgs boson, Γ H , using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb −1 at a centre-of-mass energy √ s = 7 TeV and 19.7 fb −1 at √ s = 8 TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of Γ H < 22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of m H = 125.6 GeV.
Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions ... more Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions at √ s = 7 TeV, undertaken with the CMS experiment at the LHC. The b quarks are assumed to decay exclusively to tW. The b b → tW − tW + process can be identified by its distinctive signatures of three leptons or two leptons of same charge, and at least one b-quark jet. Using a data sample corresponding to an integrated luminosity of 4.9 fb −1 , observed events are compared to the standard model background predictions, and the existence of b quarks having masses below 611 GeV/c 2 is excluded at 95% confidence level.
Doubly-charged Higgs bosons are searched for in e + e − collision data collected with the L3 dete... more 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.
A search for a heavy gauge boson W has been conducted by the CMS experiment at the LHC in the dec... more A search for a heavy gauge boson W has been conducted by the CMS experiment at the LHC in the decay channel with an electron and large transverse energy imbalance E miss T , using proton-proton collision data corresponding to an integrated luminosity of 36 pb −1. No excess above standard model expectations is seen in the transverse mass distribution of the electron-E miss T system. Assuming standard-model-like couplings and decay branching fractions, a W boson with a mass less than 1.36 TeV/c 2 is excluded at 95% confidence level.
A search for supersymmetry is presented using a sample of events with b jets and missing transver... more A search for supersymmetry is presented using a sample of events with b jets and missing transverse momentum. The search uses a data sample of proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 35 pb −1 , collected with the CMS detector. A total of 0.33 +0.43 −0.33 (stat.) ± 0.13 (syst.) events is predicted, using control samples in the data, to arise from standard model processes, and one event is observed in the data. Upper limits are set at the 95% confidence level on the cross sections of benchmark supersymmetric models.
A search for new physics is presented based on an event signature of at least three jets accompan... more A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 pb −1 collected in proton-proton collisions at √ s = 7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets.
A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heav... more 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.
Combined results are reported from searches for the standard model Higgs boson in proton-proton c... more Combined results are reported from searches for the standard model Higgs boson in proton-proton collisions at √ s = 7 TeV in five Higgs boson decay modes: γγ, bb, ττ, WW, and ZZ. The explored Higgs boson mass range is 110-600 GeV. The analysed data correspond to an integrated luminosity of 4.6-4.8 fb −1. The expected excluded mass range in the absence of the standard model Higgs boson is 118-543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127-600 GeV at 95% CL, and in the mass range 129-525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1σ, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance ≥3.1σ anywhere in the search range 110-600 (110-145) GeV is estimated to be 1.5σ (2.1σ). More data are required to ascertain the origin of this excess.
A search for a Higgs boson produced in e + e − collisions in association with a Z boson and decay... more 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 −1. 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.
Single top production in e + e − annihilations is searched for in data collected by the L3 detect... more 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.
Neutral-current four-fermion production, e + e − → fff ′f ′ , is studied in 0.7 fb −1 of data col... more Neutral-current four-fermion production, e + e − → fff ′f ′ , is studied in 0.7 fb −1 of data collected with the L3 detector at LEP at centre-of-mass energies √ s = 183 − 209 GeV. Four final states are considered: qqνν, qqℓ + ℓ − , ℓ + ℓ − ℓ ′+ ℓ ′− and ℓ + ℓ − νν, where ℓ denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e + e − → Zγ * → fff ′f ′ process is studied and its total cross section at the average centre-of-mass energy √ s = 196.6 GeV is found to be 0.29 ± 0.05 ± 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qqℓ + ℓ − final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found.
The double-radiative process e + e − → Zγγ → qqγγ where the two hard photons escape detection at ... more The double-radiative process e + e − → Zγγ → qqγγ where the two hard photons escape detection at low polar angles into opposite directions, is studied in 0.62 fb −1 of data collected with the L3 detector at LEP at centre-of-mass energies between 188.6 GeV and 209.2 GeV. The cross sections are measured and found to be consistent with the Standard Model expectations.
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Papers by Atul Gurtu