Search for gluinos and squarks using like-sign dileptons in pp macro collisions at square root of s = 1.8 TeV.
Phys Rev Lett 87:25 (2001) 251803
Abstract:
We present results of the first search for like-sign dilepton ( e(+/-)e(+/-), e(+/-)mu(+/-), mu(+/-)mu(+/-)) events associated with multijets and large missing energy using 106 pb(-1) of data in pp macro collisions at square root of s = 1.8 TeV collected during 1992-1995 by the CDF experiment. Finding no events that pass our selection, we examine pair production of gluinos (tilde g) and squarks (tilde q) in a constrained framework of the minimal supersymmetric standard model. At tan beta = 2 and mu = -800 GeV/c(2), we set 95% confidence level limits of M(tilde g)>221 GeV/c(2) for M(tilde g) approximately M(tilde q), and M(tilde q)>168 GeV/c(2) for M(tilde q)>>M(tilde g), both with small variation as a function of mu.Observation of diffractive J/psi production at the Fermilab Tevatron.
Phys Rev Lett 87:24 (2001) 241802
Abstract:
We report the first observation of diffractive J/psi(--> mu+mu-) production in pp collisions at root square[s] = 1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum p(mu)T>2 GeV/c within the pseudorapidity region /eta/ < 1.0, the ratio of diffractive to total J/psi production rates is found to be R(J/psi) = [1.45 +/- 0.25]%. The ratio R(J/psi)(x) is presented as a function of x-Bjorken. By combining it with our previously measured corresponding ratio R(jj)(x) for diffractive dijet production, we extract a value of 0.59 +/- 0.15 for the gluon fraction of the diffractive structure function of the proton.Search for quark-lepton compositeness and a heavy W' Boson using the enu channel in p p macro collisions at square root of [s] = 1.8 TeV.
Phys Rev Lett 87:23 (2001) 231803
Abstract:
We present searches for quark-lepton compositeness and a heavy W' boson at high electron-neutrino transverse mass. We use approximately 110 pb(-1) of data collected in p p macro collisions at square root of [s] = 1.8 TeV by the CDF Collaboration during 1992-1995. The data are consistent with standard model expectations. Limits are set on the quark-lepton compositeness scale Lambda, the ratio of partial cross sections sigma(W'-->enu)/sigma(W-->enu), and the mass of a W' boson with standard model couplings. We exclude Lambda<2.81 TeV and a W' boson with mass below 754 GeV/c(2) at the 95% confidence level. Combining with our previously published limit obtained using the muon channel, we exclude a W' boson with mass below 786 GeV/c(2) at the 95% confidence level.A study of a combination of MICROMEGAS+ GEM chamber in Ar-CO2 gas
IEEE Nuclear Science Symposium and Medical Imaging Conference 1 (2001) 265-268
Abstract:
A MICROMEGAS is a micropatterned gaseous detector that has great potential in many applications including high energy physics and astronomy. The detector consists of a micromesh supported by thin pillars (50 μm) and the space between the micromesh and the anode plane defines an amplification gap. The detector has a high rate capability and good spatial resolution. The performance of the MICROMEGAS can be improved by a preamplification device like a GEM to factor the gas multiplication into two stages. With the added preamplication, it is possible to minimize spark rates in detecting heavily ionizing particles without sacrificing gas gain significantly. The additional gas gain provided by the GEM also allows the detector to operate in a clean gas mixture like Ar-CO2 The use of a clean gas mixture allows the device to be radiation hard.Evidence for the decay D0→K+π-π+π-
Physical Review D American Physical Society (APS) 64:11 (2001) 111101