46 research outputs found
Events With Large Missing Transverse Energy At the Cern Collider .2. Search For the Decays of W+/-into Heavy-leptons and of Z0 Into Noninteracting Particles
No full textWe report on further analysis of events with large missing transverse energy from 715 nb-1 of data from the UA1 experiment at the CERN proton-antiproton collider. Measured W and Z0 rates and heavy flavour cross sections are used to predict rates of missing transverse energy event from all known standard model process. Limits are derived on two possible new sources, namely: (1) semi-hadronic decays of a fourth sequential charged heavy lepton coupling to the W boson, (2) Z0 decays into additional pairs of non-interacting particles. After taking into additional pairs of non-interacting particles. After taking into account all known sources of missing transverse energy events, we find a mass limit on a fourth-generation charged lepton of mL>41 GeV/c2 (90% CL) and a limit on the number of additional neutrino species of n≤7 (90% CL). © 1987
SEARCH FOR NEW HEAVY QUARKS IN PROTON - ANTI-PROTON COLLISIONS AT s**(1/2) = 0.63-TeV
No full textWe report on a search for new heavy quarks using data collected by the UA1 experiment during 1983, 1984 and 1985 at the CERN proton-antiproton collider, corresponding to an integrated luminosity of approximately 700 nb-1. Studying events with a muon or an isolated electron, accompanied by one or more jets, we find good agreement between our data and Monte Carlo predictions for the production of charm and beauty, without the need for a new quark. A top quark model, involving the decay W→t {Mathematical expression} and direct t {Mathematical expression} production via the strong interaction, is used to determine our detection efficiency for top. This allows us to place an upper limit on the cross section for producing top quarks as a function of the top quark mass. Our analysis is not sensitive to the W→t {Mathematical expression} process alone. By comparing our limit with a calculation of the t {Mathematical expression} cross section, added to the W→t {Mathematical expression} cross section derived from our own measurements of W →lv, we are able to place a lower limit on the mass of the top quark. From the lowest order (αs 2) calculation, using the choice of structure functions and Q2 scale that give the lowest cross section, we find: {Mathematical expression} Including an estimate of the next higher order (αs 2) and calculating the cross section with the EUROJET QCD Monte Carlo program using a less extreme choice for the structure functions and Q2 scale gives: {Mathematical expression} A search has also been made for a fourth generation, charge 1/3 quark (b'). Assuming that the b' mass is smaller than that of the top quark and that it can-not be produced in W decays, the mass limits, using the above procedures, are respectively mb'>32 GeV/c2 and mb'>44 GeV/c2, both at 95% confidence level. © 1988 Springer-Verlag
EXPERIMENTAL LIMIT ON THE DECAY W+- ---> pi+- gamma AT THE CERN PROTON - ANTI-PROTON COLLIDER
No full textA STUDY OF THE GENERAL CHARACTERISTICS OF PROTON - ANTI-PROTON COLLISIONS AT S**(1/2) = 0.2-TeV TO 0.9-TeV
No full textThe general characteristics of inelastic proton-antiproton collisions at the CERN SPS Collider are studied with the UA1 detector using magnetic and calorimetric analysis. Results are presented on charged particle multiplicities and transverse and longitudinal momenta, and on total transverse energy distributions at centre of mass energies ranging from 0.2 to 0.9 TeV
Diffraction dissociation in photoproduction at HERA
No full textA study is presented of the process γp → XY, where there is a large rapidity gap between the systems X and Y. Measurements are made of the differential cross section as a function of the invariant mass Mx of the system produced at the photon vertex. Results are presented at centre of mass energies of (W) = 187 GeV and 〈W〉 = 231 GeV, both where the proton dominantly remains intact and, for the first time, where it dissociates. Both the centre of mass energy and the Mx 2 dependence of HERA data and those from a fixed target experiment may simultaneously be described in a triple-Regge model. The low mass photon dissociation process is found to be dominated by diffraction, though a sizable subleading contribution is present at larger masses. The pomeron intercept is extracted and found to be αP(0) = 1.068 ± 0.016 (stat.) ± 0.022 (syst.) ± 0.041 (model), in good agreement with values obtained from total and elastic hadronic and photoproduction cross sections. The diffractive contribution to the process γp → Xp with Mx 2/W2 < 0.05 is measured to be 22.2 ± 0.6 (stat.) ± 2.6 (syst.) ± 1.7 (model) % of the total γp cross section at 〈W〉 = 187 GeV. © Springer-Verlag 1997
A measurement of the kaon charge radius
No full textThe negative kaon electromagnetic form factor has been measured in the space-like q2 range 0.015-0.10 (GeV/c)2 by the direct scattering of 250 GeV kaons from electrons at the CERN SPS. It is found that the kaon mean square charge radius = 0.34 +/- 0.05 fm2. From data collected simultaneously for πe scattering, the difference between the charged pion and kaon mean square radii (which is less sensitive to systematic errors) is found to be - <r2K = 0.1 0 +/- 0.045 fm2
