We present a search for the pair production of scalar top quarks (t˜1), the lightest supersymmetric partners of the top quarks, in pp¯ collisions at a center-of-mass energy of 1.96 TeV, using data ...corresponding to an integrated luminosity of 7.3 fb−1 collected with the D0 experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a b quark, a charged lepton, and a scalar neutrino (ν˜). We investigate final states arising from t˜1t˜¯1→bb¯μτν˜ν˜ and t˜1t˜¯1→bb¯ττν˜ν˜. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (mt˜1,mν˜) plane.
► We introduce the concept of Laternal Trigger Probability functions for EAS. ► We apply this concept to the surface array of the Pierre Auger Observatory. ► Using simulations LTPs are derived for ...energies between 10
17 and 10
19
eV. ► The LTPs can also be obtained from data using hybrid events. ► We show how LTPs from data are in good agreement with simulations.
In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an Extensive Air Shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5
km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10
17 and 10
19
eV and zenith angles up to 65°. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data using events simultaneously observed by the fluorescence and the surface detector of the Pierre Auger Observatory (hybrid events). We validate the Monte Carlo results showing how LTP functions from data are in good agreement with simulations.
We report a search for effects of large extra spatial dimensions in pp 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.
We report a measurement of the flux of cosmic rays with unprecedented precision and statistics using the Pierre Auger Observatory. Based on fluorescence observations in coincidence with at least one ...surface detector we derive a spectrum for energies above 1018 eV. We also update the previously published energy spectrum obtained with the surface detector array. The two spectra are combined addressing the systematic uncertainties and, in particular, the influence of the energy resolution on the spectral shape. The spectrum can be described by a broken power law E−γ with index γ=3.3 below the ankle which is measured at log10(Eankle/eV)=18.6. Above the ankle the spectrum is described by a power law with index 2.6 followed by a flux suppression, above about log10(E/eV)=19.5, detected with high statistical significance.