BESIII data show a particular angular distribution for the decay of the
$J/\psi$ and $\psi(2S)$ mesons into the hyperons $\Lambda\overline{\Lambda}$
and $\Sigma^0\overline{\Sigma}^0$. More in details ...the angular distribution of
the decay $\psi(2S) \to \Sigma^0\overline{\Sigma}^0$ exhibits an opposite trend
with respect to that of the other three channels: $J/\psi \to
\Lambda\overline{\Lambda}$, $J/\psi \to \Sigma^0\overline{\Sigma}^0$ and
$\psi(2S) \to \Lambda\overline{\Lambda}$. We define a model to explain the
origin of this phenomenon.
The RD53A large scale pixel demonstrator chip has been developed in 65 nm CMOS technology by the RD53 collaboration, in order to face the unprecedented design requirements of the pixel 2 phase ...upgrades of the CMS and ATLAS experiments at CERN. This prototype chip is designed to demonstrate that a set of challenging specifications can be met, such as: high granularity (small pixels of 50×50 or 25× 100 µm 2 ) and large pixel chip size (~2x2 cm 2 ), high hit rate (3 GHz/cm 2 ), high readout speed, very high radiation levels (500 Mrad - 1 Grad) and operation with serial powering. Furthermore, coping with the long latency of the trigger signal (~12.5 µs), used to select only events of interest in order to achieve sustainable output data rates, requires increased buffering resources in the limited pixel area. The RD53A chip has been fabricated in an engineer run. It integrates a matrix of 400×192 pixels and features various design variations in the analog and digital pixel matrix for testing purposes. This paper presents an overview of the chip architecture and of the methodologies used for efficient design of large complex mixed signal chips for harsh radiation environments. Experimental results obtained from the characterization of the RD53A chip are reported to demonstrate that design objectives have been achieved. Moreover, design improvements and new features being developed in the RD53B framework for final ATLAS and CMS production chips are discussed.
A Monte Carlo triple-GEM simulation tuned with data Cossio, F.; Alexeev, M.; Amoroso, A. ...
2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC),
2018-Nov.
Conference Proceeding
Triple-GEM detectors are a well known technology used in high energy physics experiments. A reliable Monte Carlo simulation has to be developed to reproduce the performance which have been measured ...experimentally, for example in beam tests, and be able to infer the future behavior in real conditions. In detail, the software has to simulate the response of the detector to the passage of particles, from the primary ionization, to the amplification and diffusion of the electrons and eventually to the induction of the charge on the anode strips. In the case of gas detectors, existing softwares such as GARFIELD++ already perform a very detailed simulation of the physical processes but are CPU time consuming. In this presentation a description of a faster simulation is presented. It models the results about the electron production (primary ionization and avalanche) and diffusion in a triple-GEM obtained from GARFIELD++ and then it reconstructs the signal induced on each anode strip according to the Shockley-Ramo theorem. The simulation has been tuned on the data collected in several beam tests and it can reproduce the real values of time and charge measured by the strip. When the reconstruction algorithms used in the field of Micro Pattern Gas Detectors, such as the Charge Centroid or the micro-Time Projection Chamber readout, are applied on the simulated data, the model shows performance comparable to the experimental one. This provides a validation of this model and allows to extend its usage in different conditions, i.e. geometries, presence of magnetic field, high voltage settings, different direction of the incident particles, to evaluate the expected outcome of the triple-GEM in those cases.
Gas detectors are very light instruments used in high energy physics to measure the particle properties: position and momentum. Gas Electron Multiplier (GEM) technology has been invented by F. Sauli ...in 1997 and in the past tens of years the knowledge of this Micro Pattern Gas Detector (MPGD) increased. A design with a triple-GEM has been used in several experiments in high energy physics such as TOTEM and COMPASS. This technology allows to achieve good spatial resolution performances and can be used to create large area detector with a shapeable surface, e.g. the KLOE2 Inner Tracker or the upcoming upgrade of the BESIII Inner Tracker. A triple-GEM uses three stages of GEMs, with high electric field, to amplify the number of the electrons produced by the primary ionization of the charged particle passing in the gas, with a total gain of about 10 4 . The signal is then collected on a segmented anode and dedicated algorithms are used to reconstruct the charged particle position. The measurement of both the time and the charge information on the anode strip allows to use two algorithms: the Charge Centroid and the micro-Time Projection Chamber readout. The CC is strongly performing with orthogonal tracks while the µTPC gives its best results if magnetic field or if non-orthogonal tracks are present. These reconstruction methods are anti-correlated and the combination of the two is needed to keep the spatial resolution stable between the regions with different performances. A beam test with planar triple-GEM has been performed and in this presentation the merging algorithm of the CC and µTPC as a function of the charge and the multiplicity of the signal will be shown: a stable spatial resolution of about 130 µm has been achieved. In addition to this, the impact of the transversal and longitudinal diffusions on the reconstruction in µTPC mode will be shown, as well as the inter-strip capacitance effect.
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 γ/β 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.
BESIII data show a particular angular distribution for the decay of the \(J/\psi\) and \(\psi(2S)\) mesons into the hyperons \(\Lambda\overline{\Lambda}\) and \(\Sigma^0\overline{\Sigma}^0\). More in ...details the angular distribution of the decay \(\psi(2S) \to \Sigma^0\overline{\Sigma}^0\) exhibits an opposite trend with respect to that of the other three channels: \(J/\psi \to \Lambda\overline{\Lambda}\), \(J/\psi \to \Sigma^0\overline{\Sigma}^0\) and \(\psi(2S) \to \Lambda\overline{\Lambda}\). We define a model to explain the origin of this phenomenon.
Os autores apresentam análise retrospectiva de 44 pacientes com Polipose Múltipla Familiar tratados no Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto,Universidade de São Paulo, ...entre janeiro de 1991 a julho de 2005. Foram estudados aspectos epidemiológicos (idade, sexo), genéticos, principais sintomas, antecedentes pessoais e aspectos envolvendo tratamento cirúrgico e complicações pós-operatórias, comparando os achados com os da literatura correlata. Dos pacientes, 31 são do sexo masculino e 13 do feminino com idade média de 32 anos (14 - 60 anos). Os sintomas prevalentes foram: sangramento intestinal (62,5 %), alteração do hábito intestinal (60%), e com menor freqüência dor abdominal (45 %) e emagrecimento (30%). Relataram casos de polipose familiar 67,5% dos pacientes e 62,5% referiram parentes com antecedente de neoplasias (intestinal e extra-intestinal). Cerca de 32,5% dos pacientes já apresentavam neoplasia de cólon na época do diagnóstico da polipose,com idade média de 39 anos. O tratamento cirúrgico foi realizado em 95,4% dos pacientes: 35,7% foram submetidos à proctocolectomia total(9 casos com bolsa ileal em J e 6 casos com ileostomia definitiva) e 59,2% a colectomia total com ileorretoanastomose. Atualmente 57% dos pacientes avaliados ainda estão em seguimento com reavaliações periódicas, 7% faleceram e 27% abandonaram o tratamento.
The authors present a retrospective analysis of forty-four patients with familiar adenomatosis polyposis treated at the School of Medicine of Ribeirão Preto Hospital and Clinics - University of São Paulo, from January 1991 to July 2005. Epidemiologic (age and gender) and genetic aspects were investigated as well as main symptoms, personal history and surgical treatment outcome. Data obtained were compared to the available literature. Our results show that 31 patients were male and 13 female, with average age of 32 years-old (14 to 60 years-old). The main symptoms were intestinal bleeding (62.5 %) and intestinal habit alteration (60 %). Less frequently, patients showed abdominal pain (45 %) and loss of weight (30 %). Familiar adenomatosis polyposis was reported by 67.5 % of the patients and relatives with neoplasms (intestinal and extra-intestinal) were referred by 62.5 % of the patients. By the time of the polyposis diagnosis, 32.5 % of the patients have already been diagnosed for colon cancer, with average age of 39 years old. Surgical treatment was performed in 95.4 % of the patients, total proctocolectomy was performed in 35.7 % (9 cases with ileal J- pouch and 6 with permanent ileostomy) and total colectomy with ileo rectal anasthomosis in 59.2%. From all patients evaluated, 57 % are still under follow up, 7 % died and 27 % gave up treatment.
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