121152679
Development of a 10-inch HPD with integrated readout electronics
Abstract A round 10-in. diameter Hybrid Photodiode (HPD) with spherical entrance window is under development for Cherenkov imaging applications in cosmic ray astronomy. The HPD adopts the fountain focusing electron optics, which, as already demonstrated in the 5 inch Pad HPD, allows for a linear demagnification of the image over practically the full tube diameter. Self-triggering front-end electronics providing also sparse readout capability, has been tested. High-efficiency Rb 2 Te cathodes have been produced on a UV extended borosilicate glass windows with very thin conductive underlayers of Indium Tin Oxide. We report on the design of the 10-in. HPD, the fabrication procedure and first tests of a 5-in. HPD with Rb 2 Te photocathode and 2048 channels.
55671747
Improved determination of the sample composition of dimuon events produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV
We use a new method to estimate with 5% accuracy the contribution of pion and kaon in-flight-decays to the dimuon data set acquired with the CDF detector. Based on this improved estimate, we show that the total number and the properties of the collected dimuon events are not yet accounted for by ordinary sources of dimuons which also include the contributions, as measured in the data, of heavy flavor, ϒ, and Drell–Yan production in addition to muons mimicked by hadronic punchthrough. The number of unaccounted events corresponds to (12.8±3.2)% of the $b\bar{b}$ production. We find that (23±6)% of the unaccounted events contain additional muon candidates. For comparison, this fraction is (6.9±0.4)% for events due to $b\bar{b}$ production.
17003556
Observation of exclusive electron-positron production in hadron-hadron collisions.
We present the first observation of exclusive e(+)e(-) production in hadron-hadron collisions, using pp[over] collision data at (square root) s = 1.96 TeV taken by the run II Collider Detector at Fermilab, and corresponding to an integrated luminosity of 532 pb(-1). We require the absence of any particle signatures in the detector except for an electron and a positron candidate, each with transverse energy E(T) > 5 GeV and pseudorapidity |eta| < 2. With these criteria, 16 events are observed compared to a background expectation of 1.9+/-0.3 events. These events are consistent in cross section and properties with the QED process pp[over] --> p + e(+)e(-) + p[over] through two-photon exchange. The measured cross section is 1.6(-0.3)(+0.5)(stat) +/- 0.3(syst) pb. This agrees with the theoretical prediction of 1.71+/-0.01 pb.
209832886
Model-independent and quasi-model-independent search for new physics at CDF
Data collected in run II of the Fermilab Tevatron are searched for indications of new electroweak scale physics. Rather than focusing on particular new physics scenarios, CDF data are analyzed for discrepancies with respect to the standard model prediction. A model-independent approach (Vista) considers the gross features of the data and is sensitive to new large cross section physics. A quasi-model-independent approach (Sleuth) searches for a significant excess of events with large summed transverse momentum and is particularly sensitive to new electroweak scale physics that appears predominantly in one final state. This global search for new physics in over 300 exclusive final states in 927pb-1 of pp collisions at s=1.96TeV reveals no such significant indication of physics beyond the standard model. © 2008 The American Physical Society.
18811077
Measurement of the single-top-quark production cross section at CDF.
We report a measurement of the single-top-quark production cross section in 2.2 fb;{-1} of pp collision data collected by the Collider Detector at Fermilab at sqrt[s]=1.96 TeV. Candidate events are classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of 2.2(-0.6)(+0.7)(stat+syst) pb, extract the Cabibbo-Kobayashi-Maskawa matrix-element value |V(tb)|=0.88(-0.12)(+0.13)(stat+syst)+/-0.07(theory), and set the limit |V(tb)|>0.66 at the 95% C.L.
60626146
ILC Reference Design Report: ILC Global Design Effort and World Wide Study
122823000
Study of Bose-Einstein correlations in e+ e- --> W+ W- events at LEP
Bose-Einstein correlations between like-sign charged-particle pairs in e(+)e(-) --> W+ W- events recorded with the OPAL detector at LEP at centre-of-mass energies between 183 GeV and 209 GeV are studied. Recently proposed methods which allow direct searches for correlations in the data via distributions of test variables are used to investigate the presence of correlations between hadrons originating from different W bosons in W+W- --> q (q) over barq (q) over bar events. Within the statistics of the data sample no evidence for inter - WW Bose-Einstein correlations is obtained. The data are also compared with predictions of a recent implementation of Bose-Einstein correlation effects in the Monte Carlo model PYTHIA.