An improved method for measuring muon energy using the truncated mean of dE/dx

The measurement of muon energy is critical for many analyses in large Cherenkov detectors, particularly those that involve separating extraterrestrial neutrinos from the atmospheric neutrino background. Muon energy has traditionally been determined by measuring the specific energy loss (dE/dx) along the muon's path and relating the dE/dx to the muon energy. Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in dE/dx values is quite large, leading to a typical energy resolution of 0.29 in log10(E_mu) for a muon observed over a 1 km path length in the IceCube detector. In this paper, we present an improved method that uses a truncated mean and other techniques to determine the muon energy. The muon track is divided into separate segments with individual dE/dx values. The elimination of segments with the highest dE/dx results in an overall dE/dx that is more closely correlated to the muon energy. This method results in an energy resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This technique is applicable to any large water or ice detector and potentially to large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure

All-particle cosmic ray energy spectrum measured with 26 IceTop stations

We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, the surface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysis were taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122 km^2. The analysis investigated the energy spectrum from 1 to 100 PeV measured for three different zenith angle ranges between 0{\deg} and 46{\deg}. Because of the isotropy of cosmic rays in this energy range the spectra from all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under different assumptions on the primary mass composition. Good agreement of spectra in the three zenith angle ranges was found for the assumption of pure proton and a simple two-component model. For zenith angles {\theta} < 30{\deg}, where the mass dependence is smallest, the knee in the cosmic ray energy spectrum was observed between 3.5 and 4.32 PeV, depending on composition assumption. Spectral indices above the knee range from -3.08 to -3.11 depending on primary mass composition assumption. Moreover, an indication of a flattening of the spectrum above 22 PeV were observed.Comment: 38 pages, 17 figure

Neutrino oscillation studies with IceCube-DeepCore

AbstractIceCube, a gigaton-scale neutrino detector located at the South Pole, was primarily designed to search for astrophysical neutrinos with energies of PeV and higher. This goal has been achieved with the detection of the highest energy neutrinos to date. At the other end of the energy spectrum, the DeepCore extension lowers the energy threshold of the detector to approximately 10 GeV and opens the door for oscillation studies using atmospheric neutrinos. An analysis of the disappearance of these neutrinos has been completed, with the results produced being complementary with dedicated oscillation experiments. Following a review of the detector principle and performance, the method used to make these calculations, as well as the results, is detailed. Finally, the future prospects of IceCube-DeepCore and the next generation of neutrino experiments at the South Pole (IceCube-Gen2, specifically the PINGU sub-detector) are briefly discussed

Reconceptualizing informal work practices: Some observations from an ethnic minority community in urban UK

Whilst paid informal work has been conceptualized as a form of paid employment imbued with solely economic motivations, this article critically argues that such a market‐­oriented reading fails to take into account alternative explanations for the existence of informal work practices. Using evidence from 50 interviews conducted within a Pakistani urban community in a northern UK city, this article, uses a mixed‐embeddedness perspective to highlight the importance of predominantly socially and culturally driven motives in the decision to engage in informal work. The findings highlight that participation in informal work, whilst a product of marginalization due to certain institutional and structural factors, is also driven by a range of non‐monetary motives—a result of certain socially embedded work relations between ethnic minority workers and their employers. It is this social embeddedness of the employer–employee relationship in the Pakistani ethnic minority community that explains the continuation of informal work practices in the face of prevailing laws and regulations. The findings add weight to the understanding of informal work as being about more than just economics and constraints, offering these ethnic minority workers opportunities, even status, and giving them agency in an otherwise disempowered situation

Adaptive plasticity of floral display size in animal-pollinated plants

Plants need not participate passively in their own mating, despite their immobility and reliance on pollen vectors. Instead, plants may respond to their recent pollination experience by adjusting the number of flowers that they display simultaneously. Such responsiveness could arise from the dependence of floral display size on the longevity of individual flowers, which varies with pollination rate in many plant species. By hand-pollinating some inflorescences, but not others, we demonstrate plasticity in display size of the orchid Satyrium longicauda. Pollination induced flower wilting, but did not affect the opening of new flowers, so that within a few days pollinated inflorescences displayed fewer flowers than unpollinated inflorescences. During subsequent exposure to intensive natural pollination, pollen removal and receipt increased proportionally with increasing display size, whereas pollen-removal failure and self-pollination accelerated. Such benefit–cost relations allow plants that adjust display size in response to the prevailing pollination rate to increase their attractiveness when pollinators are rare (large displays), or to limit mating costs when pollinators are abundant (small displays). Seen from this perspective, pollination-induced flower wilting serves the entire plant by allowing it to display the number of flowers that is appropriate for the current pollination environment

Spatial mating networks in insect-pollinated plants

Gene flow in plant populations is largely determined by landscape heterogeneity. Both the shape of the pollination kernel and the spatial distribution of trees affect the distribution of pollen grains and the genotypes they harbour, but little is known about the relative contribution of each of these two factors. Using genetic markers we build a spatial network of pollination events between any two trees in a population of Prunus mahaleb, an insect-pollinated plant. Then, we apply tools from the science of complex networks to characterize the structure of such a mating network. Although the distribution of the number of pollen donors per tree is quite homogeneous, the identity of donors is distributed heterogeneously across the population. This results in a population structured in well-defined modules or compartments, formed by a group of mother trees and their shared pollen donors. Long-distance pollination events decrease the modular structure by favouring mating among all available mates. This increases gene flow across the entire population, reducing its genetic structure, and potentially decreasing the role of genetic drift.Peer reviewe