Measurement of the bb dijet cross section in pp collisions at √s = 7 TeV with the ATLAS detector
European Physical Journal C Springer 76:12 (2016) 670
Abstract:
The dijet production cross section for jets containing a b-hadron (b-jets) has been measured in proton–proton collisions with a centre-of-mass energy of √s = 7 TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of 4.2 fb−1. The cross section is measured for events with two identified b-jets with a transverse momentum pT > 20GeV and a minimum separation in the η–φ plane of ΔR = 0.4. At least one of the jets in the event is required to have pT > 270GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the b-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization.Tagging $b$ quarks at extreme energies without tracks
Journal of Physics G: Nuclear and Particle Physics Institute of Physics 43:8 (2016) 085001
Abstract:
We describe a new hit-based b-tagging technique for high energy jets and study its performance with a Geant4-based simulation. The technique uses the fact that at sufficiently high energy a B meson or baryon can live long enough to traverse the inner layers of pixel detectors such as those in the ATLAS, ALICE, or CMS experiments prior to decay. By first defining a "jet" via the calorimeter, and then counting hits within that jet between pixel layers at increasing radii, we show it is possible to identify jets that contain b-quarks by detecting a jump in the number of hits without tracking requirements. We show that the technique maintains fiducial efficiency at TeV scale B hadron energies, far beyond the range of existing algorithms, and improves upon conventional b-taggers.Study of built-in amplifier performance on HV-CMOS sensor for the ATLAS phase-II strip tracker upgrade
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 831 (2016) 156-160
Charge collection studies in irradiated HV-CMOS particle detectors
Journal of Instrumentation IOP Publishing 11:4 (2016) P04007
Abstract:
Charge collection properties of particle detectors made in HV-CMOS technology were investigated before and after irradiation with reactor neutrons. Two different sensor types were designed and processed in 180 and 350 nm technology by AMS. Edge-TCT and charge collection measurements with electrons from 90Sr source were employed. Diffusion of generated carriers from undepleted substrate contributes significantly to the charge collection before irradiation, while after irradiation the drift contribution prevails as shown by charge measurements at different shaping times. The depleted region at a given bias voltage was found to grow with irradiation in the fluence range of interest for strip detectors at the HL-LHC. This leads to large gains in the measured charge with respect to the one before irradiation. The increase of the depleted region was attributed to removal of effective acceptors. The evolution of depleted region with fluence was investigated and modeled. Initial studies show a small effect of short term annealing on charge collection.Search for new phenomena in dijet mass and angular distributions from pp collisions at root s=13 TeV with the ATLAS detector
Physics Letters B Elsevier 754 (2016) 302-322