Study on the top quark pair production mechanism in 1.96 TeV proton-antiproton collisions

The study of the top quark pair production mechanism in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV is described. The main subjects are the measurements of the top quark pair production cross section, the top quark mass and a search for a new particle decaying to the top quark pair. The analyses are based on 1.9 fb{sup -1} of data collected by the Collider Detector at Fermilab (CDF) Run II experiment between March 2002 and May 2007, using the lepton+jets events. The measured top quark pair production cross section is 8.2 {+-} 0.5 (stat.) {+-} 0.8 (syst.) {+-} 0.5 (lum.) pb, which is slightly higher than the standard model prediction at the top mass of 175 GeV/c{sup 2}. The top quark mass is an important parameter in the standard model, and also in the experimental studies. The measured top quark mass if 171.6 {+-} 2.0 (stat.) {+-} 1.3(syst.) GeV/c{sup 2}. Finally, they report on a search for a new gauge boson decaying to t{bar t}, which interferes with the standard model gluon in the q{bar q} {yields} t{bar t} production process. They call such a hypothetical particle a 'Massive Gluon'. The observed t{bar t} invariant mass distribution is consistent with the standard model expectations, and also the measured massive gluon coupling strength with quarks is consistent within a statistical fluctuation of the standard model expectation in the wide range of the massive gluon masses and widths. They set the upper and lower limits on the coupling strength of the massive gluon

Status of the XENON Experiments

The XENON experiments search for weakly interacting massive particles (WIMPs) using dual-phase xenon time projection chambers. While the XENON100 experiment completed its science program, the next ton-scale experiment, XENON1T, is fully installed and moving towards science data-taking. The most recent results of the collaboration are presented: from XENON100 latest analysis on low mass WIMPs to XENON1T status and its projected sensitivity, that has been evaluated to reach a minimum cross section of $1.6\times10^{-47}$~cm$^2$ at a WIMP mass of 50~GeV$/c^2$ after 2~years exposure with 1~ton of fiducial volume

Measurement of the D+D^+- Meson Production Cross Section at Low Transverse Momentum in ppˉp\bar{p} Collisions at s=1.96\sqrt{s}=1.96 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