26 research outputs found
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Search for Excited or Exotic Electron Production Using the Dielectron + Photon Signature at CDF in Run II
The author presents a search for excited or exotic electrons decaying to an electron and a photon with high transverse momentum. An oppositely charged electron is produced in association with the excited electron, yielding a final state dielectron + photon signature. The discovery of excited electrons would be a first indication of lepton compositeness. They use {approx} 202 pb{sup -1} of data collected in p{bar p} collisions at {radical}s = 1.96 TeV with the Collider Detector at Fermilab during March 2001 through September 2003. The data are consistent with standard model expectations. Upper limits are set on the experimental cross-section {sigma}({bar p}p {yields} ee* {yields} ee{gamma}) at the 95% confidence level in a contact-interaction model and a gauge-mediated interaction model. Limits are also presented as exclusion regions in the parameter space of the excited electron mass (M{sub e*}) and the compositeness energy scale ({Lambda}). In the contact-interaction model, for which there are no previously published limits, they find M{sub e*} < 906 GeV is excluded for M{sub e*} = {Lambda}. In the gauge-mediated model, the exclusion region in the M{sub e*} versus the phenomenological coupling f/{Lambda} parameter space is extended to M{sub e*} < 430 GeV for f/{Lambda} {approx} 10{sup -2} GeV{sup -1}. In comparison, other experiments have excluded M{sub e*} < 280 GeV for f/{Lambda} {approx} 10{sup -2} GeV{sup -1}
Measurement of the - Meson Production Cross Section at Low Transverse Momentum in Collisions at TeV
International audienceWe report on a measurement of the D+-meson production cross section as a function of transverse momentum (pT) in proton-antiproton (pp¯) collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10  fb-1 of integrated luminosity. We use D+→K-π+π+ decays fully reconstructed in the central rapidity region |y|<1 with transverse momentum down to 1.5  GeV/c, a range previously unexplored in pp¯ collisions. Inelastic pp¯-scattering events are selected online using minimally biasing requirements followed by an optimized offline selection. The K-π+π+ mass distribution is used to identify the D+ signal, and the D+ transverse impact-parameter distribution is used to separate prompt production, occurring directly in the hard-scattering process, from secondary production from b-hadron decays. We obtain a prompt D+ signal of 2950 candidates corresponding to a total cross section σ(D+,1.5<pT<14.5  GeV/c,|y|<1)=71.9±6.8(stat)±9.3(syst)  μb. While the measured cross sections are consistent with theoretical estimates in each pT bin, the shape of the observed pT spectrum is softer than the expectation from quantum chromodynamics. The results are unique in pp¯ collisions and can improve the shape and uncertainties of future predictions