University of Canterbury

About: University of Canterbury is a education organization based out in Christchurch, New Zealand. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 11100 authors who have published 29846 publications receiving 893232 citations. The organization is also known as: Te Whare Wānanga o Waitaha & Canterbury College.

A search for a doubly-charged Higgs boson in pp collisions at √s=7 TeV

Abstract: A search for a doubly-charged Higgs boson in pp collisions at root s = 7 TeV is presented. The data correspond to an integrated luminosity of 4.9 fb(-1), collected by the CMS experiment at the LHC. The search is performed using events with three or more isolated charged leptons of any flavor, giving sensitivity to the decays of pair-produced triplet components Phi(++)Phi(--), and Phi(++)Phi(-) from associated production. No excess is observed compared to the background prediction, and upper limits at the 95 % confidence level are set on the Phi(++) production cross section, under specific assumptions on its branching fractions. Lower bounds on the Phi(++) mass are reported, providing significantly more stringent constraints than previously published limits.

Identifying the rooted species tree from the distribution of unrooted gene trees under the coalescent

Abstract: Gene trees are evolutionary trees representing the ancestry of genes sampled from multiple populations. Species trees represent populations of individuals—each with many genes—splitting into new populations or species. The coalescent process, which models ancestry of gene copies within populations, is often used to model the probability distribution of gene trees given a fixed species tree. This multispecies coalescent model provides a framework for phylogeneticists to infer species trees from gene trees using maximum likelihood or Bayesian approaches. Because the coalescent models a branching process over time, all trees are typically assumed to be rooted in this setting. Often, however, gene trees inferred by traditional phylogenetic methods are unrooted. We investigate probabilities of unrooted gene trees under the multispecies coalescent model. We show that when there are four species with one gene sampled per species, the distribution of unrooted gene tree topologies identifies the unrooted species tree topology and some, but not all, information in the species tree edges (branch lengths). The location of the root on the species tree is not identifiable in this situation. However, for 5 or more species with one gene sampled per species, we show that the distribution of unrooted gene tree topologies identifies the rooted species tree topology and all its internal branch lengths. The length of any pendant branch leading to a leaf of the species tree is also identifiable for any species from which more than one gene is sampled.

The winners and losers of land use intensification: pollinator community disassembly is non‐random and alters functional diversity

Abstract: Aim: Pollination services are at risk from land use change and intensification, but responses of individual pollinator species are often variable, making it difficult to detect and understand community-level impacts on pollination. We investigated changes in community composition and functional diversity of insect pollinator communities under land use change in a highly modified landscape. Location: Canterbury region, South Island, New Zealand. Methods: We trapped insect pollinators every month for 1 year at 24 sites across four land use types of increasing intensity in New Zealand: gardens with native vegetation, blackcurrant orchards, dairy farms, and rotational cropping farms. We investigated changes in pollinator species and functional richness and differences in species and functional composition. Results: Under increasing land use intensity, both species and functional richness declined markedly. Changes in functional richness, however, were overall not significantly different than expected based on the observed declines in species richness. Nevertheless, there was a significant trend towards greater than expected functional richness within less-intensive land use types and lower than expected functional richness within intensive land use types. The order of species loss under increasing land use intensity was non-random, as pollinators with a narrow diet breadth, large body size, solitary behaviour and a preference for non-floral larval food resources were lost first. Main conclusions: Our study shows that pollinator species bearing particular trait attributes are susceptible to differences in land use. Our study suggests that pollination services may be more vulnerable to environmental changes and disturbances in more intensive land use types as a result of lower pollinator functional richness.

Measurement of jet fragmentation into charged particles in pp and PbPb collisions at √sNN=2.76 TeV

Abstract: Jet fragmentation in pp and PbPb collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair was studied using data collected with the CMS detector at the LHC. Fragmentation functions are constructed using charged-particle tracks with transverse momenta pt > 4 GeV for dijet events with a leading jet of pt > 100 GeV. The fragmentation functions in PbPb events are compared to those in pp data as a function of collision centrality, as well as dijet-pt imbalance. Special emphasis is placed on the most central PbPb events including dijets with unbalanced momentum, indicative of energy loss of the hard scattered parent partons. The fragmentation patterns for both the leading and subleading jets in PbPb collisions agree with those seen in pp data at 2.76 TeV. The results provide evidence that, despite the large parton energy loss observed in PbPb collisions, the high-pt component of the fragmentation function evaluated with respect to the reconstructed jet momentum is not strongly modified in comparison to jet fragmentation in vacuum.