608 research outputs found
molecule as an axial meson
We use QCD sum rules to study the possible existence of a molecule with the quantum number . We consider the
contributions of condensates up to dimension eight and work at leading order in
. We obtain m_{D_sD^*}=(3.96\pm0.10) \GeV around 100 MeV above the
mass of the meson X(3872). The proposed state is a natural generalized state to
the strangeness sector of the X(3872), which was also found to be consistent
with a multiquark state from a previous QCD sum rule analysis.Comment: 5 pages, 3 figure
A simulation study on spatial and time resolution for a cost-effective positron emission particle tracking system
This work is the second part of a simulation study investigating the
processing of densely packed and moving granular assemblies by positron
emission particle tracking (PEPT). Since medical PET scanners commonly used for
PEPT are very expensive, a PET-like detector system based on cost-effective
organic plastic scintillator bars is being developed and tested for its
capabilities. In this context, the spatial resolution of a resting positron
source, a source moving on a freely designed model path, and a particle motion
given by a DEM (Discrete Element Method) simulation is studied using Monte
Carlo simulations and the software toolkit Geant4. This not only extended the
simulation and reconstruction to a moving source but also significantly
improved the spatial resolution compared to previous work by adding
oversampling and iteration to the reconstruction algorithm. Furthermore, in the
case of a source following a trajectory developed from DEM simulations, a very
good resolution of about 1 mm in all three directions and an average
three-dimensional deviation between simulated and reconstructed events of 2.3
mm could be determined. Thus, the resolution for a realistic particle motion
within the generic grate system (which is the test rig for further experimental
studies) is well below the smallest particle size. The simulation of the
dependence of the reconstruction accuracy on tracer particle location revealed
a nearly constant efficiency within the entire detector system, which
demonstrates that boundary effects can be neglected.Comment: Published in Particuology 88 (2024) 312-322. This manuscript version
is made available under the CC-BY-NC-ND 4.0 licens
Development of the front-end electronics for a cost-effective PET-like detector system
Most detector systems used for positron emission particle tracking (PEPT) are
very expensive due to the use of inorganic plastic scintillators combined with
a high number of readout electronic channels. This work aims to reduce the
overall cost of a PEPT-capable detector system by using large and
cost-effective plastic scintillators and developing custom 2 x 2 silicon
photomultiplier (SiPM) arrays, preamplifiers, and discriminators. The use of
long (20 mm x 20 mm x 1000 mm) plastic scintillator bars read out with
photodetectors only at their respective ends allows an overall smaller number
of photodetectors and associated readout electronics, which in turn reduces the
overall cost of the system. In addition, the development of a custom SiPM array
and preamplifier allows a free selection of interconnection and readout, as
most commercial producers only offer specific types of interconnections and
therefore lack other connections such as serial or hybrid. Thus, several common
circuit types for SiPMs and preamplifiers were tested and compared in this
work, and it was found that a serial connection implemented in a hybrid
interconnection for the SiPMs and an inverting preamplifier based on a
high-frequency operational amplifier provided the best results for the proposed
detector system. Measured with a Na-22 source, the combination of SiPM array
and preamplifier led to a rise time of 3.7 ns and a signal amplitude of 175 mV.Comment: Published in Nuclear Instruments and Methods in Physics Research A
1057 (2023) 168767. This manuscript version is made available under the
CC-BY-NC-ND 4.0 licens
Glueballs, closed fluxtubes and eta(1440)
The component of the pseudoscalar has strong
affinity for glue. But its mass is incompatible with lattice simulations that
predict a much higher value for the glueball. As a consequence it has
been suggested that could signal physics beyond the Standard
Model. Here we argue that if glueballs are closed gluonic fluxtubes then
is a prime candidate for the glueball. Furthermore, in
the absence of parity violating terms its mass should be degenerate with that
of the glueball. We also suggest that the decay properties of such
glueballs could be employed as probes for extra dimensions.Comment: 11 page
Efficiency and timing performance of the MuPix7 high-voltage monolithic active pixel sensor
The MuPix7 is a prototype high voltage monolithic active pixel sensor with
103 times 80 um2 pixels thinned to 64 um and incorporating the complete
read-out circuitry including a 1.25 Gbit/s differential data link. Using data
taken at the DESY electron test beam, we demonstrate an efficiency of 99.3% and
a time resolution of 14 ns. The efficiency and time resolution are studied with
sub-pixel resolution and reproduced in simulations.Comment: 7 pages, 13 figures, submitted to Nucl.Instr.Meth.
Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0
We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data
samples at both resonances collected with the BES III detector in 2009. We
measure the corresponding branching fractions with unprecedented precision and
provide mass spectra and Dalitz plots. The branching fraction for J/psi ->
pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.)
+0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is
measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4.
The J/psi decay is found to be dominated by an intermediate rho(770) state,
whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2,
leading to strikingly different Dalitz distributions.Comment: 15 pages, 2 figure
The response of temperate aquatic ecosystems to global warming: novel insights from a multidisciplinary project
This article serves as an introduction to this special issue of Marine Biology, but also as a review of the key findings of the AQUASHIFT research program which is the source of the articles published in this issue. AQUASHIFT is an interdisciplinary research program targeted to analyze the response of temperate zone aquatic ecosystems (both marine and freshwater) to global warming. The main conclusions of AQUASHIFT relate to (a) shifts in geographic distribution, (b) shifts in seasonality, (c) temporal mismatch in food chains, (d) biomass responses to warming, (e) responses of body size, (f) harmful bloom intensity, (f), changes of biodiversity, and (g) the dependence of shifts to temperature changes during critical seasonal windows
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