The Cosmic Ray Observatory Project: A Statewide Outreach and Education Experiment in Nebraska

The Cosmic Ray Observatory Project (CROP) is a statewide education and research experiment involving Nebraska high school students, teachers and university undergraduates in the study of extensive cosmic-ray air showers. A network of high school teams construct, install, and operate school-based detectors in coordination with University of Nebraska physics professors and graduate students. The detector system at each school is an array of scintillation counters recycled from the Chicago Air Shower Array in weather-proof enclosures on the school roof, with a GPS receiver providing a time stamp for cosmic-ray events. The detectors are connected to triggering electronics and a data-acquisition PC inside the building. Students share data via the Internet to search for time coincidences with other sites. Funded by the National Science Foundation, CROP has enlisted 29 schools with the aim of expanding to the 314 high schools in the state over several years. This report highlights both the scientific and professional development achievements of the project to date.Comment: 4 pages, 4 figures, submitted to the 2007 International Cosmic Ray Conference (ICRC2007), Merida, Mexico, July 200

Search for Large Extra Dimensions in Dielectron and Diphoton Production

We report a search for effects of large extra spatial dimensions in pp̅ collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions

Search for Large Extra Dimensions in Dielectron and Diphoton Production

We report a search for effects of large extra spatial dimensions in pp̅ collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions

Search for New Physics Using QUAERO: A General Interface to D0 Event Data

We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ , and tt̅ production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W′→ WZ. Through this interface, we make three data sets collected by the D0 experiment at √s =1.8 TeV publicly available

Multiple jet production at low transverse energies in \u3ci\u3epp̅\u3c/i\u3e collisions at √\u3ci\u3es\u3c/i\u3e = 1.8 TeV

We present data on multiple production of jets with transverse energies near 20 GeV in pp̅ collisions at √s =1.8 TeV. QCD calculations in the parton-shower approximation of PYTHIA and HERWIG and the next-to-leading order approximation of JETRAD are compared to the data for one, two, three, and four jet inclusive production. Transverse energy spectra and multiple jet angular and summed transverse-energy distributions are adequately described by the shower approximation while next-to-leading order calculations describe the data poorly

Search for first-generation scalar leptoquarks in (\u3ci\u3epp̅\u3c/i\u3e collisions at√\u3ci\u3es\u3c/i\u3e = 1.96 TeV

We report on a search for pair production of first-generation scalar leptoquarks (LQ) in pp̅ collisions at √s = 1.96 TeV using an integrated luminosity of 252 pb-1 collected at the Fermilab Tevatron collider by the D0 detector. We observe no evidence for LQ production in the topologies arising from LQL̅Q̅ → ℯqℯq and LQL̅Q̅ → ℯqνq, and derive 95% C.L. lower limits on the LQ mass as a function of β, where β is the branching fraction for LQ → ℯq. The limits are 241 and 218 GeV/c2 for β = 1 and 0.5, respectively. These results are combined with those obtained by √s = 1.8 TeV, which increases these LQ mass limits to 256 and 234 GeV/c2

Measurement of the \u3ci\u3eWW\u3c/i\u3e Production Cross Section in \u3ci\u3epp̅\u3c/i\u3e Collisions at √\u3ci\u3es\u3c/i\u3e = 1.96 TeV

We present a measurement of the W boson pair-production cross section in pp̅ collisions at a center-of- mass energy of √s = 1.96 TeV. The data, collected with the Run II D0 detector at Fermilab, correspond to an integrated luminosity of 224–252 pb-1 depending on the final state (ℯℯ, ℯμ, or μμ). We observe 25 candidates with a background expectation of 8.1 ± 0.6(stat) ± 0.6(syst) ± 0.5(lum) events. The probability for an upward fluctuation of the background to produce the observed signal is 2.3 x 10-7, equivalent to 5.2 standard deviations. The measurement yields a cross section of 13.8-3.8+4.3 (stat)-0.9+1.2 (syst) ± 0.9(lum) pb, in agreement with predictions from the standard model

Search for Anomalous Heavy-Flavor Quark Production in Association with \u3ci\u3eW\u3c/i\u3e Bosons

We search for anomalous production of heavy-flavor quark jets in association with W bosons at the Fermilab Tevatron pp̅ Collider in final states in which the heavy-flavor quark content is enhanced by requiring at least one tagged jet in an event. Jets are tagged using one algorithm based on semileptonic decays of b/c hadrons, and another on their lifetimes. We compare ℯ+ jets (164 pb-1) and μ+ jets (145 pb-1) channels collected with the D0 detector at √s = 1.96 TeV to expectations from the standard model and set upper limits on anomalous production of such events

Search for Pair Production of Light Scalar Top Quarks in \u3ci\u3epp̅\u3c/i\u3e Collisions at √\u3ci\u3es\u3c/i\u3e = 1.8 TeV

Using 85.2 ± 3.6 pb1 of pp̅ collisions collected at √s = 1.8 TeV with the D0 detector at Fermilab’s Tevatron Collider, we present the results of a search for direct pair production of scalar top quarks (t̃), the supersymmetric partners of the top quark. We examined events containing two or more jets and missing transverse energy, the signature of light scalar top quark decays to charm quarks and neutralinos. After selections, we observe 27 events while expecting 31.1 ± 6.4 events from known standard model processes. Comparing these results to next-to-leading-order production cross sections, we exclude a significant region of t̃ and neutralino phase space. In particular, we exclude the t̃ mass mt̃ \u3c 122 GeV/c2 for a neutralino mass of 45 GeV/c2