Helium identification with LHCb

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at √(s) = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb-1. A total of around 105 helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(10^12). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei

Curvature-bias corrections using a pseudomass method

Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using Z→μ + μ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z→μ + μ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass

Antioxidant properties of extracts from a white mutant of the mushroom Hypsizigus marmoreus

A white mutant of Hypsizigus marmoreus (Peck) Bigelow (Tricholomataceae) is a new edible mushroom currently available in Taiwan. The ethanolic and hot water extracts were prepared from fruit bodies and mycelia and their antioxidant properties studied. In addition to EC50 values in scavenging abilities on hydroxyl radicals, almost EC50 values were less than 10 mg/mL indicating that these extracts were effective in antioxidant properties assayed. The major antioxidant components found in hot water extracts were total phenols (10.01-13.14mg/g) and those in ethanolic extracts were total tocopherols (33.33-10.92mg/g). Correlations of contents of total antioxidant components and total tocopherols (plus beta-carotene) with EC50 values of antioxidant activity, reducing power, scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals and chelating ability on ferrous ions were established (r = 0.445-0.940), whereas the correlation of total phenol content was established only with that of scavenging ability on hydroxyl radicals (r = 0.882). (C) 2007 Elsevier Inc. All rights reserved