Ultraviolet Absorption Properties of Diatomic Sulfur

Diatomic Sulfur, S2, is present in the atmospheres of Jupiter and its moon, Io. It is very difficult to obtain an S2 spectrum in the laboratory; when heated, elemental sulfur forms many different gaseous species including S2, S3, and S4. We use a two-temperature furnace and absorption cell to create conditions of high temperature and low pressure, which favor pure S2 formation. Using high resolution measurements from the National Institute of Standards and Technology in Gaithersburg, Maryland, we quantified oscillator strengths for atmospheric modeling purposes. This work is generously supported by the Jerome A. Schiff Fellowship

Photon-rejection Power of the Light Dark Matter eXperiment in an 8 GeV Beam

The Light Dark Matter eXperiment (LDMX) is an electron-beam fixed-target experiment designed to achieve comprehensive model independent sensitivity to dark matter particles in the sub-GeV mass region. An upgrade to the LCLS-II accelerator will increase the beam energy available to LDMX from 4 to 8 GeV. Using detailed GEANT4-based simulations, we investigate the effect of the increased beam energy on the capabilities to separate signal and background, and demonstrate that the veto methodology developed for 4 GeV successfully rejects photon-induced backgrounds for at least $2\times10^{14}$ electrons on target at 8 GeV.Comment: 28 pages, 20 figures; corrected author lis

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

Cross section and couplings measurements with the ATLAS detector for the 125 GeV Higgs Boson

Detailed measurements of the properties of the 125 GeV Higgs boson are fundamental for the understanding of the electroweak symmetry breaking mechanism. Measurements of the Higgs boson allow to study the gauge, loop induced and Yukawa couplings of the Higgs boson both in production and decay modes. This talk summarizes recent ATLAS measurements of the 125 GeV Higgs boson

Muon reconstruction performance in ATLAS at Run-II

The ATLAS muon reconstruction has been improved for the Run-II of the LHC. In this presentation, we will discuss its performance as measured during the early run of the LHC in 2015 at $\sqrt{s}$= 13 TeV using samples of $J/\psi \rightarrow \mu\mu$ and $Z \rightarrow \mu\mu$ decays. Reconstruction efficiency, transverse momentum resolution, and momentum scales are measured in the various regions of the detector and for muon momenta between 5 and hundreds of GeV. They are all found to be in good agreement with corrected Monte Carlo simulations