Kaon identification and the search for heavy neutrinos at NA62

A search for heavy neutrinos in the decay K⁺→μ⁺$_h$ has been performed using the data collected by the NA62-R$_K$ experiment in 2007. The signal event selection is presented, along with an estimate of the expected background in the signal region, obtained by Monte Carlo simulation as well as data driven techniques. This estimate is supported by studies of the detector performance in muon identification efficiency and momentum resolution. Using a sample corresponding to 6x10$^7$ kaon decays in the fiducial volume, limits of order 10$^-$$^5$ have been set on the branching ratio, Br(K$^+$→μ$^+$ν$_h$ ), for neutrino masses in the range 275 MeV/c$^2$ – 375 MeV/c$^2$, under the assumption that the heavy neutrino does not decay into visible particles inside the detector. In the range 330 MeV/c$^2$ – 375 MeV/c$^2$, there are no previous limits from peak searches. Over the rest of the range, the new limits do not improve upon existing results. Improved limits might come from the NA62 experiment designed to measure the branching ratio of the ultra rare kaon decay K+→π$^+$νν, which began taking data in 2015. Kaon identification is performed by a differential Cherenkov detector. The timing resolution of the photo-detectors was measured in a pilot run in 2014 and used to improve the simulation of the detector. An algorithm was developed to align the detector during live data taking, and this was used at the start of the 2015 run

Prospects for K+→π+ννˉK^+ \to \pi^+ \nu \bar{ \nu } at CERN in NA62

The NA62 experiment will begin taking data in 2015. Its primary purpose is a 10% measurement of the branching ratio of the ultrarare kaon decay $K^+ \to \pi^+ \nu \bar{ \nu }$, using the decay in flight of kaons in an unseparated beam with momentum 75 GeV/c.The detector and analysis technique are described here.Comment: 8 pages for proceedings of 50 Years of CP

Northern Eurasia Future Initiative (NEFI): facing the challenges and pathways of global change in the 21st century

During the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been designed as an essential continuation of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), which was launched in 2004. NEESPI sought to elucidate all aspects of ongoing environmental change, to inform societies and, thus, to better prepare societies for future developments. A key principle of NEFI is that these developments must now be secured through science-based strategies co-designed with regional decision makers to lead their societies to prosperity in the face of environmental and institutional challenges. NEESPI scientific research, data, and models have created a solid knowledge base to support the NEFI program. This paper presents the NEFI research vision consensus based on that knowledge. It provides the reader with samples of recent accomplishments in regional studies and formulates new NEFI science questions. To address these questions, nine research foci are identified and their selections are briefly justified. These foci include: warming of the Arctic; changing frequency, pattern, and intensity of extreme and inclement environmental conditions; retreat of the cryosphere; changes in terrestrial water cycles; changes in the biosphere; pressures on land-use; changes in infrastructure; societal actions in response to environmental change; and quantification of Northern Eurasia's role in the global Earth system. Powerful feedbacks between the Earth and human systems in Northern Eurasia (e.g., mega-fires, droughts, depletion of the cryosphere essential for water supply, retreat of sea ice) result from past and current human activities (e.g., large scale water withdrawals, land use and governance change) and potentially restrict or provide new opportunities for future human activities. Therefore, we propose that Integrated Assessment Models are needed as the final stage of global change assessment. The overarching goal of this NEFI modeling effort will enable evaluation of economic decisions in response to changing environmental conditions and justification of mitigation and adaptation efforts

Search for heavy neutrinos in K+→μ+ν decays

The NA62 experiment recorded a large sample of K+→μ+νμ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2×10−6 to 10−5 have been set on the squared mixing matrix element |Uμ4|2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/c2. The result extends the range of masses for which upper limits have been set on the value of |Uμ4|2 in previous production search experiments