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
Recenzirano
Odprti dostop
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
Recenzirano
Odprti dostop
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
Recenzirano
Odprti dostop
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.
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.
A search for chargino–neutralino pair production in three-lepton final states with missing transverse momentum is presented. The study is based on a dataset of
s
=
13
TeV
pp
collisions recorded with ...the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139
fb
-
1
. No significant excess relative to the Standard Model predictions is found in data. The results are interpreted in simplified models of supersymmetry, and statistically combined with results from a previous ATLAS search for compressed spectra in two-lepton final states. Various scenarios for the production and decay of charginos (
χ
~
1
±
) and neutralinos (
χ
~
2
0
) are considered. For pure higgsino
χ
~
1
±
χ
~
2
0
pair-production scenarios, exclusion limits at 95% confidence level are set on
χ
~
2
0
masses up to 210 GeV. Limits are also set for pure wino
χ
~
1
±
χ
~
2
0
pair production, on
χ
~
2
0
masses up to 640 GeV for decays via on-shell
W
and
Z
bosons, up to 300 GeV for decays via off-shell
W
and
Z
bosons, and up to 190 GeV for decays via
W
and Standard Model Higgs bosons.
Electroweak measurements performed with data taken at the electron–positron collider LEP at CERN from 1995 to 2000 are reported. The combined data set considered in this report corresponds to a total ...luminosity of about 3 fb−1 collected by the four LEP experiments ALEPH, DELPHI, L3 and OPAL, at centre-of-mass energies ranging from 130 GeV to 209 GeV.
Combining the published results of the four LEP experiments, the measurements include total and differential cross-sections in photon-pair, fermion-pair and four-fermion production, the latter resulting from both double-resonant WW and ZZ production as well as singly resonant production. Total and differential cross-sections are measured precisely, providing a stringent test of the Standard Model at centre-of-mass energies never explored before in electron–positron collisions. Final-state interaction effects in four-fermion production, such as those arising from colour reconnection and Bose–Einstein correlations between the two W decay systems arising in WW production, are searched for and upper limits on the strength of possible effects are obtained. The data are used to determine fundamental properties of the W boson and the electroweak theory. Among others, the mass and width of the W boson, mW and ΓW, the branching fraction of W decays to hadrons, B(W→had), and the trilinear gauge-boson self-couplings g1Z, κγ and λγ are determined to be: mW=80.376±0.033GeVΓW=2.195±0.083GeVB(W→had)=67.41±0.27%g1Z=0.984−0.020+0.018κγ=0.982±0.042λγ=−0.022±0.019.
A search is presented for four-top-quark production using an integrated luminosity of 139 fb
-
1
of proton–proton collision data at a centre-of-mass energy of
13
TeV
collected by the ATLAS detector ...at the LHC. Events are selected if they contain a same-sign lepton pair or at least three leptons (electrons or muons). Jet multiplicity, jet flavour and event kinematics are used to separate signal from the background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The four-top-quark production cross section is measured to be
24
-
6
+
7
fb. This corresponds to an observed (expected) significance with respect to the background-only hypothesis of 4.3 (2.4) standard deviations and provides evidence for this process.
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