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

Determination of Absolute Strengths of N2 Quadrupole Lines From High-Resolution Ground-based IR Solar Observations

High-resolution, high signal-to-noise ratio, solar absorption spectra recorded with a Fourier transform spectrometer at the International Scientific Station of the Jungfraujoch, Switzerland, have been analyzed to determine the strengths of several lines belonging to the S branch of the N2 (1-0) electric quadrupole vibration-rotation band centered at 2329.9168 cm-1. The method which was applied here was based on equivalent width measurements of lines observed over a broad range of air masses; extrapolation of these measurements to zero air mass gave the line strengths for the transitions S7 to S10, independent of half widths, an ambiguity unavoidable with the use of curve-fitting techniques. The resulting absolute accuracies of the line strengths derived here, estimated to be better than +-2.5% for S8, +-2.6% for S10, +-3.4% for S9, and +-5.1% for S7, are due largely to the high quality and quantity of the spectra retained in this analysis and the accuracy with which the observation conditions are known. An important application of the improved values for these N2 transitions, which have low initial ground state energies, is the direct determination of the line-of-sight atmospheric air masses associated with remotely sensed infrared spectroscopic observations. Positions of the N2 transitions studied here have further been redetermined with an absolute accuracy better than 0.0002 cm-1

Remote sensing of the atmosphere by high resolution infrared absorption spectroscopy

peer reviewe

Map of the city of Detroit in the State of Michigan /

Scale ca. 1:2,400; 200 ft. to an in."Entered according to Act of Congress ... by John Farmer, AD 1835."Cadastral map.Cited in Alberta G. Koerner's Detroit and vicinity before 1900, no. 53.Includes index and inset

Identification of solar vibration-rotation lines of NH and the solar nitrogen abundance

High resolution solar spectra obtained from the ATMOS Fourier Transform Spectrometer (Spacelab 3 flight on April 29 - May 6, 1985) made it possible to detect for the first time vibration-rotation lines of NH from the X3 Sigma(-) state near 3 microns. Using recent theoretical results for the transition probabilities of 23 selected measured lines of the 1-0 and 2-1 bands, a solar abundance of nitrogen of 8.06 + or - 0.07 is derived. This value is compared with the result derived from N I lines and agrees with the abundance obtained from the 3s-3p, 3p-3d and 3s-prime - 3p-prime transitions, A(N) = 8.00 + or - 0.09. The final recommended solar abundance of nitrogen is A(N) = 8.00 + or - 0.05

Identification of solar vibration-rotation lines of NH and the solar nitrogen abundance

High resolution solar spectra obtained from the ATMOS Fourier Transform Spectrometer (Spacelab 3 flight on April 29 - May 6, 1985) made it possible to detect for the first time vibration-rotation lines of NH from the X3 Sigma(-) state near 3 microns. Using recent theoretical results for the transition probabilities of 23 selected measured lines of the 1-0 and 2-1 bands, a solar abundance of nitrogen of 8.06 + or - 0.07 is derived. This value is compared with the result derived from N I lines and agrees with the abundance obtained from the 3s-3p, 3p-3d and 3s-prime - 3p-prime transitions, A(N) = 8.00 + or - 0.09. The final recommended solar abundance of nitrogen is A(N) = 8.00 + or - 0.05