2,423 research outputs found
The High-Acceptance Dielectron Spectrometer HADES
HADES is a versatile magnetic spectrometer aimed at studying dielectron
production in pion, proton and heavy-ion induced collisions. Its main features
include a ring imaging gas Cherenkov detector for electron-hadron
discrimination, a tracking system consisting of a set of 6 superconducting
coils producing a toroidal field and drift chambers and a multiplicity and
electron trigger array for additional electron-hadron discrimination and event
characterization. A two-stage trigger system enhances events containing
electrons. The physics program is focused on the investigation of hadron
properties in nuclei and in the hot and dense hadronic matter. The detector
system is characterized by an 85% azimuthal coverage over a polar angle
interval from 18 to 85 degree, a single electron efficiency of 50% and a vector
meson mass resolution of 2.5%. Identification of pions, kaons and protons is
achieved combining time-of-flight and energy loss measurements over a large
momentum range. This paper describes the main features and the performance of
the detector system
The upgraded Pixel detector and the commissioning of the Inner Detector tracking of the ATLAS experiment for Run-2 at the Large Hadron Collider
Run-2 of the Large Hadron Collider (LHC) will provide new challenges to track
and vertex reconstruction with higher energies, denser jets and higher rates.
Therefore the ATLAS experiment has constructed the first 4-layer Pixel Detector
in HEP, installing a new pixel layer, also called Insertable B-Layer (IBL). The
IBL is a fourth layer of pixel detectors, and has been installed in May 2014 at
a radius of 3.3 cm between the existing Pixel Detector and a new smaller radius
beam-pipe. The new detector, built to cope with the high radiation and expected
occupancy, is the first large scale application of 3D sensors and CMOS 130~nm
readout electronics. In addition, the Pixel Detector was improved with a new
service quarter panel to recover about 3\% of defective modules lost during
Run-1 and a new optical readout system to readout the data at higher speed
while reducing the occupancy when running with increased luminosity.
Complementing detector improvements, many improvements to Inner Detector
track and vertex reconstruction were developed during the two-year shutdown of
the LHC. These include novel techniques developed to improve the performance in
the dense cores of jets, optimisation for the expected conditions, and a
software campaign which lead to a factor of three decrease in the CPU time
needed to process each recorded event.Comment: 15 pages, EPS-HEP 2015 Proceeding
Large atom number dual-species magneto-optical trap for fermionic 6Li and 40K atoms
We present the design, implementation and characterization of a dual-species
magneto-optical trap (MOT) for fermionic 6Li and 40K atoms with large atom
numbers. The MOT simultaneously contains 5.2x10^9 6Li-atoms and 8.0x10^9
40K-atoms, which are continuously loaded by a Zeeman slower for 6Li and a
2D-MOT for 40K. The atom sources induce capture rates of 1.2x10^9 6Li-atoms/s
and 1.4x10^9 40K-atoms/s. Trap losses due to light-induced interspecies
collisions of ~65% were observed and could be minimized to ~10% by using low
magnetic field gradients and low light powers in the repumping light of both
atomic species. The described system represents the starting point for the
production of a large-atom number quantum degenerate Fermi-Fermi mixture
Muon Spectrometer Phase-I Upgrade for the ATLAS Experiment: the New Small Wheel project
The instantaneous luminosity of the Large Hadron Collider at CERN will be
increased by up to a factor of five to seven with respect to the design value.
To maintain an excellent detection and background rejection capability in the
forward region of the ATLAS detector, part of the muon detection system will be
upgraded during LHC shutdown periods with the replacement of part of the
present first station in the forward regions with the so-called New Small
Wheels (NSWs). The NSWs will have a diameter of approximately 10 m and will be
made of two detector technologies: Micromegas and small-strip Thin Gap Chambers
(sTGC). The physics motivation for this significant upgrade to the ATLAS
detector will be presented. The design choices made to address the physics
needs will be discussed. Finally, the status of the production of the detector
modules will be presented.Comment: 10 pages, presented at CIPANP 201
Radiation effects studies for the high-resolution spectrograph
The generation and collection of charge carriers created during the passage of energetic protons through a silicon photodiode array are modeled. Pulse height distributions of noise charge collected during exposure of a digicon type diode array to 21 and 75 MeV protons were obtained. The magnitude of charge collected by a diode from each proton event is determined not only by diffusion, but by statistical considerations involving the ionization process itself. Utilizing analytical solutions to the diffusion equation for transport of minority carriers, together with the Vavilov theory of energy loss fluctuations in thin absorbers, simulations of the pulse height spectra which follow the experimental distributions fairly well are presented and an estimate for the minority carrier diffusion length L sub d is provided
Commissioning of the tracking system in the ATLAS detector
ATLAS is one of the four experiments that will analyze the p-p collisions at LHC. It consists of several subsystems: the Inner Detector is devoted to the measurement of the charged particle tracks in the interaction point region and the Pixel Detector is its innermost component. Both have been commissioned by using cosmic rays collected by the ATLAS detector in 2009. In the first part of the thesis, the spatial resolution of the Pixel Detector is studied and optimized. When a charged particle traverses the Pixel Detector, charges released in the sensors are collected by segmented electrodes, the pixels. The charge of each pixel is read out by the Time-over-Threshold technique and adjacent pixels are grouped into clusters. Cluster position can be computed by considering its geometrical center, but spatial resolution can be optimized if using charge information to improve position determination. In the second part of the thesis, the Inner Detector resolution in all track parameters has been studied by splitting each cosmic ray track into two halves. Since both halves stem from the same particle, they should be described by the same parameters. At the same time, the two tracks are fitted independently and can be compared to study the resolution of the tracking system. Resolution been studied as a function of track direction and distance from the beam axis. The multiple scattering contribution and several systematic effects due to residual misalignments have been evaluated
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