5,965 research outputs found
Readout system and testbeam results of the RD50-MPW2 HV-CMOS pixel chip
The RD50-CMOS group aims to design and study High Voltage CMOS (HVCMOS) chips
for use in a high radiation environment. Currently, measurements are performed
on RD50-MPW2 chip, the second prototype developed by this group. The active
matrix of the prototype consists of 8x8 pixels with analog front end. Details
of the analog front end and simulations have been already published earlier.
This contribution focuses on the Caribou based readout system of the active
matrix. Each pixel of the active matrix can be readout one after the other.
Relevant aspects of hardware, firmware and software are introduced. As a first
stage, firmware for a standalone setup is introduced and details on data flow
are given. Afterwards, a second stage of the firmware capable of synchronizing
with other detectors and accepting triggers is presented, focusing on operation
of the chip in combination with a tracking telescope to measure efficiency and
residuals.Comment: Published under licence in Journal of Physics: Conference Series by
IOP Publishing Ltd. CC-BY Content from this work may be used under the terms
of the Creative Commons Attribution 4.0 International licence. Any further
distribution of this work must maintain attribution to the author(s) and the
title of the work, journal citation and DO
SiC Based Beam Monitoring System for Particle Rates from kHz to GHz
The extremely low dark current of silicon carbide (SiC) detectors, even after
high-fluence irradiation, was utilized to develop a beam monitoring system for
a wide range of particle rates, i.e., from the kHz to the GHz regime. The
system is completely built from off-the-shelve components and is focused on
compactness and simple deployment. Beam tests using a 50 um thick SiC detector
reveal, that for low fluences, single particles can be detected and counted.
For higher fluences, beam properties were extracted from beam cross sections
using a silicon strip detector. Overall accurate results were achieved up to a
particle rate of 109 particles per second
A Proton Computed Tomography Demonstrator for Stopping Power Measurements
Particle therapy is an established method to treat deep-seated tumours using
accelerator-produced ion beams. For treatment planning, the precise knowledge
of the relative stopping power (RSP) within the patient is vital. Conversion
errors from x-ray computed tomography (CT) measurements to RSP introduce
uncertainties in the applied dose distribution. Using a proton computed
tomography (pCT) system to measure the SP directly could potentially increase
the accuracy of treatment planning. A pCT demonstrator, consisting of
double-sided silicon strip detectors (DSSD) as tracker and plastic scintillator
slabs coupled to silicon photomultipliers (SiPM) as a range telescope, was
developed. After a significant hardware upgrade of the range telescope, a 3D
tomogram of an aluminium stair phantom was recorded at the MedAustron facility
in Wiener Neustadt, Austria. In total, 80 projections with 6.5x10^5 primary
events were acquired and used for the reconstruction of the RSP distribution in
the phantom. After applying a straight-line approximation for the particle path
inside the phantom, the most probable value (MPV) of the RSP distribution could
be measured with an accuracy of 0.59%. The RSP resolution inside the phantom
was only 9.3% due to a limited amount of projections and measured events per
projection.Comment: Preprint submitted to the open-access Journal of Physics: Conference
Series. (TIPP2021 conference proceedings). IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from i
Erratum to: Search for dark matter and unparticles in events with a Z boson and missing transverse momentum in proton-proton collisions at √s=13 TeV (JHEP, (2017), 9, (106), 10.1007/JHEP09(2017)106)
In the original paper, figure 10 was incorrect. The correct figure is shown below. Additionally, the unparticle entries in table 3, as well as figure 4 and 5 were labelled with incorrect values of ΛU
Performance of neutron-irradiated 4H-Silicon Carbide diodes subjected to Alpha radiation
The unique electrical and material properties of 4H-silicon-carbide (4H-SiC)
make it a promising candidate material for high rate particle detectors. In
contrast to the ubiquitously used silicon (Si), 4H-SiC offers a higher carrier
saturation velocity and larger breakdown voltage, enabling a high intrinsic
time resolution and mitigating pile-up effects. Additionally, as radiation
hardness requirements grow more demanding, wide-bandgap materials such as
4H-SiC could offer better performance. In this work, the detector performance
of 50 micron thick 4H-SiC p-in-n planar pad sensors was investigated at room
temperature, using an 241Am alpha source at reverse biases of up to 1100 V.
Samples subjected to neutron irradiation with fluences of up to 1e16/cm^2 were
included in the study in order to quantify the radiation hardness properties of
4H-SiC. The obtained results are compared to previously performed UV-TCT
studies. Samples exhibit a drop in charge collection efficiency (CCE) with
increasing irradiation fluence, partially compensated at high reverse bias
voltages far above full depletion voltage. A plateau of the collected charges
is observed in accordance with the depletion of the volume the alpha particles
penetrate for an unirradiated reference detector. For the neutron-irradiated
samples, such a plateau only becomes apparent at higher reverse bias. For the
highest investigated fluence, CCE behaves almost linearly with increasing
reverse bias. Compared to UV-TCT measurements, the reverse bias required to
deplete a sensitive volume covering full energy deposition is lower, due to the
small penetration depth of the alpha particles. At the highest reverse bias,
the measured CCE values agree well with earlier UV-TCT studies, with
discrepancies between 1% and 5%.Comment: 10 pages (8 without references), 6 figures, 1 table, to be published
in the Proceedings Section of Journal of Instrumentation (JINST) as a
proceeding of iWoRiD202
Feasibility study of a proton CT system based on 4D-tracking and residual energy determination via time-of-flight
For dose calculations in ion beam therapy, it is vital to accurately
determine the relative stopping power (RSP) distribution within the treated
volume. Currently, RSP values are extrapolated from Hounsfield units (HU),
measured with x-ray computed tomography (CT), which entails RSP inaccuracies
due to conversion errors. A suitable method to improve the treatment plan
accuracy is proton computed tomography (pCT). A typical pCT system consists of
a tracking system and a separate residual energy (or range) detector to measure
the RSP distribution directly. This paper introduces a novel pCT system based
on a single detector technology, namely low gain avalanche detectors (LGADs).
LGADs are fast 4D-tracking detectors, which can be used to simultaneously
measure the particle position and time with precise timing and spatial
resolution. In contrast to standard pCT systems, the residual energy is
determined via a time-of-flight (TOF) measurement between different 4D-tracking
stations. The design parameters for a realistic proton computed tomography
system based on 4D-tracking detectors were studied and optimized using Monte
Carlo simulations. The RSP accuracy and RSP resolution were measured inside the
inserts of the CTP404 phantom to estimate the performance of the pCT system.
After introducing a dedicated calibration procedure for the TOF calorimeter,
RSP accuracies < 0.6 % could be achieved. Furthermore, the design parameters
with the strongest impact on the RSP resolution were identified and a strategy
to improve RSP resolution is proposed.Comment: Preprint submitted to Physics in Medicine and Biology. IOP Publishing
Ltd is not responsible for any errors or omissions in this version of the
manuscript or any version derived from i
RD50-MPW3: A fully monolithic digital CMOS sensor for future tracking detectors
The CERN-RD50 CMOS working group develops the RD50-MPWseries of monolithic
high-voltage CMOS pixel sensors for potential use in future high luminosity
experiments such as the HL-LHC and FCC-hh. In this contribution, the design of
the latest prototype in this series, RD50-MPW3, is presented. An overview of
its pixel matrix and digital readout periphery is given, with discussion of the
new structures implemented in the chip and the problems they aim to solve. The
main analog and digital features of the sensor are already tested and initial
laboratory characterisation of the chip is presented
Measurement of quark- and gluon-like jet fractions using jet charge in PbPb and pp collisions at 5.02 TeV
The momentum-weighted sum of the electric charges of particles inside a jet,
known as jet charge, is sensitive to the electric charge of the particle initiating the parton
shower. This paper presents jet charge distributions in √sNN = 5.02 TeV lead-lead (PbPb)
and proton-proton (pp) collisions recorded with the CMS detector at the LHC. These data
correspond to integrated luminosities of 404 µb
−1
and 27.4 pb−1
for PbPb and pp collisions,
respectively. Leveraging the sensitivity of the jet charge to fundamental differences in the
electric charges of quarks and gluons, the jet charge distributions from simulated events
are used as templates to extract the quark- and gluon-like jet fractions from data. The
modification of these jet fractions is examined by comparing pp and PbPb data as a
function of the overlap of the colliding Pb nuclei (centrality). This measurement tests
the color charge dependence of jet energy loss due to interactions with the quark-gluon
plasma. No significant modification between different centrality classes and with respect
to pp results is observed in the extracted quark- and gluon-like jet fractions
Measurement of differential cross sections and charge ratios for t-channel single top quark production in proton-proton collisions at mml:msqrts mml:msqrt=13 mml:mspace width="0.166667em"mml:mspaceTe mml:mspace width="0.333333em"mml:mspace
A measurement is presented of differential cross
sections for t-channel single top quark and antiquark production in proton–proton collisions at a centre-of-mass energy
of 13 TeV by the CMS experiment at the LHC. From a data
set corresponding to an integrated luminosity of 35.9 fb−1,
events containing one muon or electron and two or three jets
are analysed. The cross section is measured as a function of
the top quark transverse momentum (pT), rapidity, and polarisation angle, the charged lepton pT and rapidity, and the pT
of the W boson from the top quark decay. In addition, the
charge ratio is measured differentially as a function of the top
quark, charged lepton, and W boson kinematic observables.
The results are found to be in agreement with standard model
predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally,
the spin asymmetry, sensitive to the top quark polarisation, is
determined from the differential distribution of the polarisation angle at parton level to be 0.440 ± 0.070, in agreement
with the standard model prediction
Search for top quark decays via Higgs-boson-mediated flavor-changing neutral currents in pp collisions at √s=8 TeV
A search is performed for Higgs-boson-mediated flavor-changing neutral currents in the decays of top quarks. The search is based on proton-proton collision data
corresponding to an integrated luminosity of 19.7 fb−1 at a center-of-mass energy of 8 TeV
collected with the CMS detector at the LHC. Events in which a top quark pair is produced
with one top quark decaying into a charm or up quark and a Higgs boson (H), and the
other top quark decaying into a bottom quark and a W boson are selected. The Higgs
boson in these events is assumed to subsequently decay into either dibosons or difermions.
No significant excess is observed above the expected standard model background, and an
upper limit at the 95% confidence level is set on the branching fraction B (t → Hc) of 0.40%
and B (t → Hu) of 0.55%, where the expected upper limits are 0.43% and 0.40%, respectively. These results correspond to upper limits on the square of the flavor-changing Higgs
boson Yukawa couplings |λ
H
tc|
2 < 6.9 × 10−3 and |λ
H
tu|
2 < 9.8 × 10−
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