James Colin Hill

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Approximately 438 pb −1 of e + e − data from the OPAL detector, taken with the LEP collider running at centre-of-mass energies of 192-209 GeV, are analyzed to search for evidence of chargino pair production, e + e − → ˜ χ + 1 ˜ χ − 1 , or neutralino associated production, e + e − → ˜ χ 0 2 ˜ χ 0 1. Limits are set at the 95% confidence level on the product(More)
Searches for the neutral Higgs bosons h 0 and A 0 are used to obtain limits on the Type II Two Higgs Doublet Model (2HDM(II)) with no CP–violation in the Higgs sector and no additional particles besides the five Higgs bosons. The analysis combines approximately 170 pb −1 of data collected with the OPAL detector at √ s ≈ 189 GeV with previous runs at √ s ≈ m(More)
  • G Abbiendi, K Ackerstaff, +141 authors Heisenberg Fellow
  • 1999
Cross-sections and angular distributions for hadronic and lepton pair final states in e + e − collisions at a centre-of-mass energy near 189 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The results are used to measure the energy dependence of the electromagnetic coupling constant α em ,(More)
Differential measurements of elliptic flow (v2) for Au+Au and Cu+Cu collisions at sqrt[sNN]=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v2 with eccentricity, system size, and transverse kinetic energy (KE T). For KE T identical with mT-m up to approximately 1 GeV the scaling is compatible with(More)
The measurement of small–angle Bhabha scattering is used to determine the luminosity at the OPAL interaction point for the LEP I data recorded between 1993 and 1995. The measurement is based on the OPAL Silicon-Tungsten Luminometer which is composed of two calorimeters encircling the LEP beam pipe, on opposite sides of the interaction point. The luminometer(More)
  • G Abbiendi, K Ackerstaff, +164 authors Heisenberg Fellow
  • 1997
A search for pair produced scalar fermions with couplings that violate R-parity has been performed using a data sample corresponding to an integrated luminosity of 56 pb −1 at a centre-of-mass energy of √ s = 183 GeV collected with the OPAL detector at LEP. An important consequence of R-parity breaking interactions is that the lightest supersymmet-ric(More)
We report on the beamtest measurements of prototype ATLAS Semiconductor Tracker (SCT) modules performed during June and August 2000 at the H8 beamline at the CERN SPS. In all, 13 fully populated modules constructed from pre−series silicon detectors and the ABCD2T readout chip were tested, including examples of both barrel and forward modules in several(More)
Production of events with hadronic and leptonic final states has been measured in e + e − collisions at centre-of-mass energies of 130–172 GeV, using the OPAL detector at LEP. Cross-sections and leptonic forward-backward asymmetries are presented, both including and excluding the dominant production of radiative Zγ events, and compared to Standard Model(More)
Gluon jets are identified in e + e − hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite hemisphere. Gluon jets defined in this manner have a close correspondence to gluon jets as they are defined for analytic calculations, and are almost(More)
Cross-sections and angular distributions for hadronic and lepton-pair final states in e + e − collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The measurements are used to determine the electromagnetic coupling constant α em at(More)