Performance of a GridPix detector based on the Timepix3 chip Ligtenberg, C.; Heijhoff, K.; Bilevych, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2018, Letnik:
908
Journal Article
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A GridPix readout for a TPC based on the Timepix3 chip is developed for future applications at a linear collider. The GridPix detector consists of a gaseous drift volume read out by a single Timepix3 ...chip with an integrated amplification grid. Its performance is studied in a test beam with 2.5 GeV electrons. The GridPix detector detects single ionization electrons with high efficiency. The Timepix3 chip allowed for high sample rates and time walk corrections. Diffusion is found to be the dominating error on the track position measurement both in the pixel plane and in the drift direction, and systematic distortions in the pixel plane are below 10 μm. Using a truncated sum, an energy loss (dE/dx) resolution of 4.1% is found for an effective track length of 1 m.
On the properties of a negative-ion TPC prototype with GridPix readout Ligtenberg, C.; van Beuzekom, M.; Bilevych, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2021, Letnik:
1014
Journal Article
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The performance of a GridPix detector to read out a negative ion TPC was studied using a module with four GridPix chips that are based on the Timepix3 pixelated readout ASIC. The quad module ...dimensions are 39.6mm×28.38mm, and the maximum drift distance is 40mm. The TPC is operated using a 93.6/5.0/1.4 gas mixture (by volume) of Ar/iC4H10/CS2 with a small amount of oxygen and water vapour at a pressure of 1030mbar and a temperature of 297K. Tracks were produced by a pulsed N2 laser. The GridPix chips are sensitive to single drift ions, and allow for the determination of the drift distance using the velocities of the different ion species. The 1.56ns time resolution of the Timepix3 chips allows for a precise determination of the drift properties in the longitudinal direction. The measured mobility of majority ion charge carriers is (1.391±0003) cm2/V/s. Using the high granularity pixel readout, the transverse and longitudinal diffusion coefficients were measured to correspond to an effective thermal diffusion temperature of 314 K and 384 K respectively. For 429 detected ions, the precision on the absolute drift distance is expected to be 1.33mm for a mean drift distance of 20mm.
Performance of the GridPix detector quad Ligtenberg, C.; Bilevych, Y.; Desch, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Letnik:
956
Journal Article
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A gaseous pixel readout module with four GridPix chips, called the quad, has been developed as a building block for a large time projection chamber readout plane. The quad module has dimensions ...39.6mm×28.38mm and an active surface coverage of 68.9%. The GridPix chip consists of a Timepix3 chip with integrated amplification grid and have a high efficiency to detect single ionization electrons, which enable to make a precise track position measurement. A quad module was installed in a small time projection chamber and measurements of 2.5GeV electrons were performed at the ELSA accelerator in Bonn, where a silicon telescope was used to provide a reference track. The error on the track position measurement, both in the pixel plane and drift direction, is dominated by diffusion. The quad was designed to have minimum electrical field inhomogeneities and distortions, achieving systematics of better than 13µm in the pixel plane. The resolution of the setup is 41µm, where the total systematic error of the quad detector is 24µm.
The gaseous QUAD pixel detector Ligtenberg, C.; Bilevych, Y.; Desch, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
Recenzirano
A gaseous pixel detector has been developed based on four Timepix3 chips, called a quad, that can serve as a building block for e.g. a large Time Projection Chamber readout plane. The quad was ...designed to have minimum electrical field inhomogeneities and distortions, achieving a tracking precision in the pixel plane with systematics of better than 20 μm. Due to the high efficiency to detect the ionization electrons a precise measurement of the energy loss dE/dx can be performed. In this article we present details about the construction of the quad and the results from a recent test beam experiment performed at the ELSA electron beam in Bonn where a silicon telescope was used to provide accurate tracking to study the quad detector.
A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139 fb^{-1} of pp collision data at sqrts=13 TeV recorded with the ATLAS detector at the ...LHC. The combination includes searches performed in three decay channels: bbover ¯bbover ¯, bbover ¯τ^{+}τ^{-}, and bbover ¯γγ. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches.A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139 fb^{-1} of pp collision data at sqrts=13 TeV recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: bbover ¯bbover ¯, bbover ¯τ^{+}τ^{-}, and bbover ¯γγ. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches.
Higgsinos with masses near the electroweak scale can solve the hierarchy problem and provide a dark matter candidate, while detecting them at the LHC remains challenging if their mass splitting is ...O(1 GeV). This Letter presents a novel search for nearly mass-degenerate Higgsinos in events with an energetic jet, missing transverse momentum, and a low-momentum track with a significant transverse impact parameter using 140 fb^{-1} of proton-proton collision data at sqrts=13 TeV collected by the ATLAS experiment. For the first time since LEP, a range of mass splittings between the lightest charged and neutral Higgsinos from 0.3 to 0.9 GeV is excluded at 95% confidence level, with a maximum reach of approximately 170 GeV in the Higgsino mass.Higgsinos with masses near the electroweak scale can solve the hierarchy problem and provide a dark matter candidate, while detecting them at the LHC remains challenging if their mass splitting is O(1 GeV). This Letter presents a novel search for nearly mass-degenerate Higgsinos in events with an energetic jet, missing transverse momentum, and a low-momentum track with a significant transverse impact parameter using 140 fb^{-1} of proton-proton collision data at sqrts=13 TeV collected by the ATLAS experiment. For the first time since LEP, a range of mass splittings between the lightest charged and neutral Higgsinos from 0.3 to 0.9 GeV is excluded at 95% confidence level, with a maximum reach of approximately 170 GeV in the Higgsino mass.
This paper presents a direct measurement of the decay width of the top quark using
events in the lepton+jets final state. The data sample was collected by the ATLAS detector at the LHC in ...proton-proton collisions at a centre-of-mass energy of 8 TeV and corresponds to an integrated luminosity of 20.2 fb
. The decay width of the top quark is measured using a template fit to distributions of kinematic observables associated with the hadronically and semileptonically decaying top quarks. The result,
for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.
Searches for new resonances are performed using an unsupervised anomaly-detection technique. Events with at least one electron or muon are selected from 140 fb^{-1} of pp collisions at sqrts=13 TeV ...recorded by ATLAS at the Large Hadron Collider. The approach involves training an autoencoder on data, and subsequently defining anomalous regions based on the reconstruction loss of the decoder. Studies focus on nine invariant mass spectra that contain pairs of objects consisting of one light jet or b jet and either one lepton (e,μ), photon, or second light jet or b jet in the anomalous regions. No significant deviations from the background hypotheses are observed. Limits on contributions from generic Gaussian signals with various widths of the resonance mass are obtained for nine invariant masses in the anomalous regions.
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