652 research outputs found
Study and optimization of the spatial resolution for detectors with binary readout
Using simulations and analytical approaches, we have studied single hit
resolutions obtained with a binary readout, which is often proposed for high
granularity detectors to reduce the generated data volume. Our simulations
considering several parameters (e.g. strip pitch) show that the detector
geometry and an electronics parameter of the binary readout chips could be
optimized for binary readout to offer an equivalent spatial resolution to the
one with an analogue readout. To understand the behavior as a function of
simulation parameters, we developed analytical models that reproduce simulation
results with a few parameters. The models can be used to optimize detector
designs and operation conditions with regard to the spatial resolution.Comment: 21 pages, 20 figure
A novel technique for the measurement of the avalanche fluctuation of gaseous detectors
We have developed a novel technique for the measurement of the avalanche
fluctuation of gaseous detectors using a UV laser. The technique is simple and
requires a short data-taking time of about ten minutes. Furthermore, it is
applicable for relatively low gas gains. Our experimental setup as well as the
measurement principle, and the results obtained with a stack of Gas Electron
Multipliers (GEMs) operated in several gas mixtures are presented.Comment: 7 pages, 7 figures. For the proceedings of VCI2016, to be published
in Nucl. Instrum. Methods Phys. Res.
Measuring the top Yukawa coupling at the ILC at sqrt(s) = 500 GeV
We report on the feasibility of the direct measurement of the top Yukawa
coupling g_t at the International Linear Collider (ILC) during its first phase
of operation with a center-of-mass energy of 500 GeV. The signal and background
models incorporate the non-relativistic QCD corrections which enhance the
production cross section near the t-tbar threshold. The e+e- -> t tbar H signal
is reconstructed in the 6-jet + lepton and the 8-jet modes. The results from
the two channels are combined. The background processes considered are e+e- ->
t bbar W- / tbar b W+ (which includes e+e- -> t tbar), e+e- -> t tbar Z, and
e+e- -> t tbar g* -> t tbar b bar. We use a realistic fast Monte-Carlo detector
simulation. Signal events are selected using event shape variables, through jet
clustering, and by identifying heavy flavor jets. Assuming a Higgs mass of 120
GeV, polarized electron and positron beams with (Pe-,Pe+) = (-0.8,+0.3), and an
integrated luminosity of 1 ab-1, we estimate that the e+e- -> t tbar H events
can be seen with a statistical significance of 5.2 sigma, corresponding to the
relative top Yukawa coupling measurement accuracy of |Delta g_t / g_t| = 10%.Comment: 9 pages, 6 figures, to be submitted to Phys. Rev.
A Time Projection Chamber with GEM-Based Readout
For the International Large Detector concept at the planned International
Linear Collider, the use of time projection chambers (TPC) with micro-pattern
gas detector readout as the main tracking detector is investigated. In this
paper, results from a prototype TPC, placed in a 1 T solenoidal field and read
out with three independent GEM-based readout modules, are reported. The TPC was
exposed to a 6 GeV electron beam at the DESY II synchrotron. The efficiency for
reconstructing hits, the measurement of the drift velocity, the space point
resolution and the control of field inhomogeneities are presented.Comment: 22 pages, 19 figure
Measurement of differential cross sections for top quark pair production using the lepton plus jets final state in proton-proton collisions at 13 TeV
National Science Foundation (U.S.
Particle-flow reconstruction and global event description with the CMS detector
The CMS apparatus was identified, a few years before the start of the LHC operation at CERN, to feature properties well suited to particle-flow (PF) reconstruction: a highly-segmented tracker, a fine-grained electromagnetic calorimeter, a hermetic hadron calorimeter, a strong magnetic field, and an excellent muon spectrometer. A fully-fledged PF reconstruction algorithm tuned to the CMS detector was therefore developed and has been consistently used in physics analyses for the first time at a hadron collider. For each collision, the comprehensive list of final-state particles identified and reconstructed by the algorithm provides a global event description that leads to unprecedented CMS performance for jet and hadronic tau decay reconstruction, missing transverse momentum determination, and electron and muon identification. This approach also allows particles from pileup interactions to be identified and enables efficient pileup mitigation methods. The data collected by CMS at a centre-of-mass energy of 8 TeV show excellent agreement with the simulation and confirm the superior PF performance at least up to an average of 20 pileup interactions
Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV
Many measurements and searches for physics beyond the standard model at the LHC rely on the efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this paper, the discriminating variables and the algorithms used for heavy-flavour jet identification during the first years of operation of the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, are presented. Heavy-flavour jet identification algorithms have been improved compared to those used previously at centre-of-mass energies of 7 and 8 TeV. For jets with transverse momenta in the range expected in simulated events, these new developments result in an efficiency of 68% for the correct identification of a b jet for a probability of 1% of misidentifying a light-flavour jet. The improvement in relative efficiency at this misidentification probability is about 15%, compared to previous CMS algorithms. In addition, for the first time algorithms have been developed to identify jets containing two b hadrons in Lorentz-boosted event topologies, as well as to tag c jets. The large data sample recorded in 2016 at a centre-of-mass energy of 13 TeV has also allowed the development of new methods to measure the efficiency and misidentification probability of heavy-flavour jet identification algorithms. The heavy-flavour jet identification efficiency is measured with a precision of a few per cent at moderate jet transverse momenta (between 30 and 300 GeV) and about 5% at the highest jet transverse momenta (between 500 and 1000 GeV)
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