Particle theory

Abstract:

We discuss the generalisation of high-energy resummation to rapidity distributions to leading log- arithmic accuracy. We test our procedure applying it to Higgs production in gluon-gluon fusion both with finite top mass and in the infinite mass limit. We check that they reproduce the known results at fixed order and we estimate finite top mass corrections to the NLO distribution.

Abstract:

Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient α = 3.20 ± 0.57 km-1 between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for λ ≡ 1/α of ∼300 m with 20% uncertainty. No significant depth or frequency dependence has been found. © 2010 Elsevier B.V. All rights reserved.

Abstract:

We compare predictions for high energy neutrino and anti-neutrino deep inelastic scattering cross-sections within the conventional DGLAP formalism of next-to-leading order QCD, using the latest parton distribution functions such as CT10, HERAPDF1.5 and MSTW08 and taking account of PDF uncertainties. From this we derive a benchmark cross-section and uncertainty which is consistent with the results obtained earlier using the ZEUS-S PDFs. We advocate the use of this for analysing data from neutrino telescopes, in order to facilitate comparison between their results.

Abstract:

We present the results of searches for dipolar-type anisotropies in different energy ranges above 2.5 × 1017 eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% C.L. for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations. © 2011 Published by Elsevier B.V.

Abstract:

We report on the search for electromagnetic and hadronic showers ("cascades") produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were recorded during 1001 days of detector livetime in the years 2000-2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of νe:νμ: ντ = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Φ ∝ E-2 is less than 5.0 × 10-7 GeV s-1 sr-1 cm-2 at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production. © 2010 Elsevier B.V. All rights reserved.