Dihadron correlations at high pT

Jet quenching in the matter created in high energy nucleus-nucleus collisions provides a tomographic tool to probe the medium properties. Recent experimental results from the Relativistic Heavy-Ion Collider (RHIC) on characterization of jet production via dihadron correlations at high transverse momentum are reviewed. Expectations from the dihadron measurements for the lower energy \sqrtsNN=62.4 GeV RHIC run are discussed.Comment: Talk given at Hot Quarks 2004: Workshop for Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions (HQ'04), Taos Valley, New Mexico, 18-24 Jul 200

Low-Mass Lepton Pair Production in Pb-Au Collisions at 40 AGeV

The CERES/NA45 experiment at the CERN SPS has previously measured $e^{+}e^{-}$ pair production in 160 AGeV Pb-Au collisions. In the mass region m>0.2 GeV/c$^{2}$, an enhancement of $2.7\pm0.4(statist.)\pm0.5(syst.)$ compared to the expectation from known hadronic decay sources was observed. In the 40 AGeV data taken in 1999, an enhancement is again found; a preliminary analysis gives the even larger value of $4.5\pm1.2(statist.)$. The results are compared to theoretical model calculations based on $\pi^{+}\pi^{-}$ annihilation with a modified $\rho$-propagator.Comment: To appear in the proceedings of International Europhysics Conference on High-Energy Physics (HEP 2001), Budapest, Hungary, 12-18 Jul 200

Jets as a Probe of Dense Matter at RHIC

Jet quenching in the matter created in high energy nucleus-nucleus collisions provides a tomographic tool to probe the medium properties. Recent experimental results on jet production at the Relativistic Heavy-Ion Collider (RHIC) are reviewed. Jet properties in p+p and d+Au collisions have been measured, establishing the baseline for studying jet modification in heavy-ion collisions. Current progress on detailed studies of high transverse momentum production in Au+Au collisions is discussed, with an emphasis on dihadron correlation measurements.Comment: 8 pages, 9 figures. Plenary talk given at 17th International Conference on Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California, 11-17 Jan 2004. Submitted to J.Phys.

SigmaFlow as a Tool for Studying Wind Comfort in Urban Environment

Интенсивный рост современных городов приводит к строительству жилых микрорайонов с плотным расположением зданий различной высотности. Подобные архитектурные решения способствуют непредсказуемому изменению аэрационного режима территории, который может вызывать ухудшение экологической обстановки города, а также формирование дискомфортных условий в зоне пребывания человека. Для изучения механизмов формирования данных условий и прогнозирования ветрового режима используется микромасштабная модель атмосферы города, реализованная в программе «SigmaFlow». В работе представлены результаты верификации численной модели с экспериментальными данными на двух тестовых задачах обтекания модельных элементов городской застройки. Полученные результаты расчетов демонстрируют достаточно хорошее совпадение с экспериментальными данными. Кроме этого, был выполнен анализ формирования ветровых условий в реальном жилом микрорайоне. Получены характерные структуры течения при обтекании зданий, а также выявлены места формирования дискомфортных и опасных зон для пребывания человекаThe intensive growth of modern cities leads to the construction of residential microdistricts with a dense arrangement of buildings of various heights. Such architectural solutions contribute to an unpredictable change in the aeration regime of the territory, which can lead to a deterioration in the ecological situation of the city, as well as to the formation of uncomfortable conditions in the area of human presence. To study the mechanisms of formation of these conditions and forecasting of the wind regime, a microscale model of the atmosphere of the city, implemented in the SigmaFlow program, is used. The paper presents the results of verification of a numerical model with experimental data on two test problems of flow around model elements of urban development. The obtained calculation results demonstrate a fairly good agreement with the experimental data. In addition, an analysis was made of the formation of wind conditions in a real residential area. Characteristic flow structures were obtained when flowing around buildings, and places of formation of uncomfortable and dangerous zones for human stay were identifie

Non-standard neutrino interactions in IceCube

Non-standard neutrino interactions (NSI) may arise in various types of new physics. Their existence would change the potential that atmospheric neutrinos encounter when traversing Earth matter and hence alter their oscillation behavior. This imprint on coherent neutrino forward scattering can be probed using high-statistics neutrino experiments such as IceCube and its low-energy extension, DeepCore. Both provide extensive data samples that include all neutrino flavors, with oscillation baselines between tens of kilometers and the diameter of the Earth. DeepCore event energies reach from a few GeV up to the order of 100 GeV - which marks the lower threshold for higher energy IceCube atmospheric samples, ranging up to 10 TeV. In DeepCore data, the large sample size and energy range allow us to consider not only flavor-violating and flavor-nonuniversal NSI in the μ−τ sector, but also those involving electron flavor. The effective parameterization used in our analyses is independent of the underlying model and the new physics mass scale. In this way, competitive limits on several NSI parameters have been set in the past. The 8 years of data available now result in significantly improved sensitivities. This improvement stems not only from the increase in statistics but also from substantial improvement in the treatment of systematic uncertainties, background rejection and event reconstruction

IceCube Search for Earth-traversing ultra-high energy Neutrinos

The search for ultra-high energy neutrinos is more than half a century old. While the hunt for these neutrinos has led to major leaps in neutrino physics, including the detection of astrophysical neutrinos, neutrinos at the EeV energy scale remain undetected. Proposed strategies for the future have mostly been focused on direct detection of the first neutrino interaction, or the decay shower of the resulting charged particle. Here we present an analysis that uses, for the first time, an indirect detection strategy for EeV neutrinos. We focus on tau neutrinos that have traversed Earth, and show that they reach the IceCube detector, unabsorbed, at energies greater than 100 TeV for most trajectories. This opens up the search for ultra-high energy neutrinos to the entire sky. We use ten years of IceCube data to perform an analysis that looks for secondary neutrinos in the northern sky, and highlight the promise such a strategy can have in the next generation of experiments when combined with direct detection techniques