Abstract
Particle physics experiments often require the simultaneous
reconstruction of many interaction vertices. Usually, this problem
is solved by ad hoc heuristic algorithms. We propose a ...universal
approach to address the multiple vertex finding through a principled
formulation as a minimum-cost lifted multicut problem. The suggested
algorithm is tested in a typical LHC environment with multiple
proton-proton interaction vertices. Reconstruction errors caused by
the particle detectors complicate the solution and require the
introduction of special metrics to assess the vertex-finding
performance. We demonstrate that the minimum-cost lifted multicut
approach outperforms heuristic algorithms and works well up to the
highest vertex multiplicity expected at the LHC.
Diamond pixel modules Asner, D.; Barbero, M.; Bellini, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2011, Letnik:
636, Številka:
1
Journal Article
Recenzirano
With the commissioning of the LHC in 2010 and upgrades expected in 2015, ATLAS and CMS are planning to upgrade their innermost tracking layers with radiation hard technologies. Chemical Vapor ...Deposition diamond has been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle, CDF and all LHC experiments. This material is now being considered as a sensor material for use very close to the interaction region where the most extreme radiation conditions exist. Recently the RD42 collaboration constructed, irradiated and tested polycrystalline and single-crystal chemical vapor deposition diamond sensors to the highest fluences expected at the super-LHC. We present beam test results of chemical vapor deposition diamond up to fluences of 1.8×10
16
protons/cm
2 illustrating that both polycrystalline and single-crystal chemical vapor deposition diamonds follow a single damage curve. We also present beam test results of irradiated complete diamond pixel modules.
Three-dimensional (3-D) silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrate into the bulk material in contrast to standard Si detectors with ...planar electrodes on the top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as, for example, the radiation environment expected in an upgrade to the Large Hadron Collider at CERN. For the first time, several 3-D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here, we report results on unirradiated devices with three 3-D electrodes per 50times400 mum 2 pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9%plusmn0.1% for tracks incident parallel to the electrodes and of 99.9%plusmn0.1% for tracks incident at 15deg are measured. The homogeneity and charge sharing of the efficiency over the pixel area are measured.
Particle physics experiments often require the simultaneous reconstruction of many interaction vertices. Usually, this problem is solved by ad hoc heuristic algorithms. We propose a universal ...approach to address the multiple vertex finding through a principled formulation as a minimum-cost lifted multicut problem. The suggested algorithm is tested in a typical LHC environment with multiple proton-proton interaction vertices. Reconstruction errors caused by the particle detectors complicate the solution and require the introduction of special metrics to assess the vertex-finding performance. We demonstrate that the minimum-cost lifted multicut approach outperforms heuristic algorithms and works well up to the highest vertex multiplicity expected at the LHC.
Radiation hard diamond pixel detectors Velthuis, J.J.; Mathes, M.; Kagan, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2008, Letnik:
591, Številka:
1
Journal Article
Recenzirano
Even though the LHC has not yet begun, already a high luminosity upgrade of the LHC is being planned. The sensors at radii of about 3
cm will have to withstand an expected fluence exceeding 10
16
...particles/cm
2 in 5 years. At this fluence current silicon sensors cease to function. Due to its large bandgap and high displacement energy, diamond is an intrinsically very radiation hard material. Combined with its fast charge collection, its low dielectric constant and the absence of thermally generated leakage current, diamond is a very interesting detector material for the sensors close to the beam. A full size, 61×16.5
mm
2, ATLAS pixel module using chemical-vapor deposition (CVD) diamond was built and characterized in a beam test. The measured position resolution is consistent with the expected binary resolution. The efficiency was larger than 97%. Nowadays also large size single-crystal CVD diamonds are available. A single-crystal diamond was used to produce a 2880 channel pixel detector. This detector showed an 99.992±0.002% efficiency at an electric field as low as 0.25
V/μm.
During the 2010 pp run of the Large Hadron Collider at \surd s = 7 TeV, a substantial data sample of high pT triggers, 35/pb, has been collected by the ATLAS detector, corresponding to about 2,500 ...produced top-quark pair events containing at least one lepton (e or mu) in the final state. Measurements of the top-quark pair production cross-section, the top mass, the W helicity fractions in top-quark decays and studies of single-top quark production and top-quark pair production with anomalous missing transverse energy are presented.
Nucl.Instrum.Meth.A582:714-718,2007 After a ten years planning and construction phase, the ATLAS pixel detector
is nearing its completion and is scheduled to be integrated into the ATLAS
detector to ...take data with the first LHC collisions in 2007. An overview of the
construction is presented with particular emphasis on some of the major and
most recent problems encountered and solved.
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