95 research outputs found
A model to explain angular distributions of and decays into and
BESIII data show a particular angular distribution for the decay of the
and mesons into the hyperons
and . More in details the angular distribution of
the decay exhibits an opposite trend
with respect to that of the other three channels: , and
. We define a model to explain the
origin of this phenomenon.Comment: 6 pages, 7 figures, to be published in Chinese Physics
PARSIFAL: a toolkit for triple-GEM parametrized simulation
PARSIFAL (PARametrized SImulation) is a tool which reproduces a triple-GEM
detector full response to the passage of a charged particle, taking into
account most of the involved physical effects. A triple-GEM is a gaseous
detector that amplifies the primary ionization, generated by the incoming
radiation interacting with the gas, through three amplification stages,
providing position measurement with a resolution around 100 micron, energy
resolution better than 20% and time resolution below 10 ns. Despite well known
and robust software such as GARFIELD++ can simulate the electron propagation in
gas and the interaction with the electric field, considering the avalanche
formation and signal creation, they are CPU-time consuming. The necessity to
reduce the processing time while maintaining the precision of a full simulation
is the main driver of this work. PARSIFAL takes into account the main processes
involved in the signal formation, starting from ionization, spatial and
temporal diffusion, the effect of the magnetic field, if any, and GEM
amplification properties. The induction of the signal and the electronics
response are also present. PARSIFAL parameters are evaluated by means of
GARFIELD++ simulations; the results of the simulation are compared to
experimental data from testbeam and tuning factors are applied to improve the
matching.Comment: submitted to JINS
A new inner tracker based on GEM detectors for the BES III experiment
A new inner tracker based on a cylindrical gas electron-multiplier detector is under development to replace the current inner drift chamber of the BES III spectrometer. The BES III experiment is carried out at the BEPC II e[Formula: see text]e[Formula: see text] collider in Beijing at center-of-mass energies in the tau-charm region with a design luminosity of 1.0 [Formula: see text] 10[Formula: see text] cm[Formula: see text]s[Formula: see text]. The new inner tracker consists of three cylindrical layers of triple GEM surrounding the interaction point, covering 93% of solid angle. To fulfill physics requirements, a spatial resolution of 130 μm must be achieved. Both planar and cylindrical prototypes have been built and tested. A custom ASIC using UMC 110-nm technology has been designed to provide charge and time measurements—the first prototype is in testing. Notable and innovative aspects of the new inner tracker and the performance of the detector prototypes and readout ASIC are reported here
Track-based alignment for the BESIII CGEM detector in the cosmic-ray test
The Beijing Electron Spectrometer III (BESIII) is a multipurpose detector
operating on the Beijing Electron Positron Collider II (BEPCII). After more
than ten year's operation, the efficiency of the inner layers of the Main Drift
Chamber (MDC) decreased significantly. To solve this issue, the BESIII
collaboration is planning to replace the inner part of the MDC with three
layers of Cylindrical triple-Gas Electron Multipliers (CGEM).
The new features of the CGEM detector will improve the spatial resolution to
130 m. To meet this goal, a careful calibration of the detector is
necessary to fully exploit the potential of the CGEM detector. In all the
calibrations, the detector alignment plays an important role to improve the
detector precision. The track-based alignment for the CGEM detector with the
Millepede algorithm is implemented to reduce the uncertainties of the hit
position measurement. Using the cosmic-ray data taken in 2020 with the two
layers setup, the displacement of the outer layer with respect to the inner
layer is determined by a simultaneous fit applied to more than 160000 tracks. A
good alignment precision has been achieved that guarantees the design request
could be satisfied in the future. A further alignment will be performed using
the combined information of tracks from cosmic-ray and collisions after the
CGEM is installed into the BESIII detector
Study of cosmogenic activation above ground for the DarkSide-20k experiment
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating
/
background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods
Design of analog front-ends for the RD53 demonstrator chip
The RD53 collaboration is developing a large scale pixel front-end chip, which will be a tool to evaluate the performance of 65 nm CMOS technology in view of its application to the readout of the innermost detector layers of ATLAS and CMS at the HL-LHC. Experimental results of the characterization of small prototypes will be discussed in the frame of the design work that is currently leading to the development of the large scale demonstrator chip RD53A to be submitted in early 2017. The paper is focused on the analog processors developed in the framework of the RD53 collaboration, including three time over threshold front-ends, designed by INFN Torino and Pavia, University of Bergamo and LBNL and a zero dead time front-end based on flash ADC designed by a joint collaboration between the Fermilab and INFN. The paper will also discuss the radiation tolerance features of the front-end channels, which were exposed to up to 800 Mrad of total ionizing dose to reproduce the system operation in the actual experiment
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