The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay
μ
+
→
e
+
γ
from data taken in the first physics run in 2021. No excess of ...events over the expected background is observed, yielding an upper limit on the branching ratio of
B
(
μ
+
→
e
+
γ
)
<
7.5
×
10
-
13
(90% CL). The combination of this result and the limit obtained by MEG gives
B
(
μ
+
→
e
+
γ
)
<
3.1
×
10
-
13
(90% CL), which is the most stringent limit to date. A ten-fold larger sample of data is being collected during the years 2022–2023, and data-taking will continue in the coming years.
This paper discusses the effects of radiation damage to SiPMs on the performances of plastic scintillator counters with series-connected SiPM readout, focusing on timing measurements. The ...performances of a counter composed of a 120×40×5mm3 scintillator tile read out by two sets of six SiPMs from AdvanSiD connected in series attached on the short sides are presented, for different combinations of SiPMs at various levels of irradiation. Firstly, six SiPMs were equally irradiated with electrons from 90Sr sources up to a fluence of Φe−≈3×1012cm−2. The timing resolution of the counter gradually deteriorated by the increase in dark current. The dark current and the deterioration were reduced when the counter was cooled from 30 °C to 10 °C. Secondly, 33 SiPMs were irradiated with reactor neutrons. The fluence levels ranged from Φeq≈8.7×108cm−2 to Φeq≈5.5×1013cm−2. The characteristics of counters read out by series-connected SiPMs with non-uniform damage levels were investigated. The signal pulse height, the time response, and the timing resolution depend on the hit position in the counter when SiPMs’ irradiation is not uniform.
Operation and performance of the MEG II detector Afanaciev, K.; Baldini, A. M.; Ban, S. ...
The European physical journal. C, Particles and fields,
02/2024, Letnik:
84, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The MEG II experiment, located at the Paul Scherrer Institut (PSI) in Switzerland, is the successor to the MEG experiment, which completed data taking in 2013. MEG II started fully operational data ...taking in 2021, with the goal of improving the sensitivity of the
μ
+
→
e
+
γ
decay down to
∼
6
×
10
-
14
almost an order of magnitude better than the current limit. In this paper, we describe the operation and performance of the experiment and give a new estimate of its sensitivity versus data acquisition time.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have developed a new laser-based time calibration system for highly segmented scintillator counters like the MEG II pixelated Timing Counter (pTC), consisting of 512 centimetre-scale scintillator ...counters read out by silicon photomultipliers (SiPMs). It is difficult to apply previous laser-based calibration methods for conventional metre-scale Time-Of-Flight detectors to the MEG II pTC from the implementation and the accuracy points of view. This paper presents a new laser-based time calibration system which can overcome such difficulties. A laser pulse is split into each scintillator counter via several optical components so that we can directly measure the time offset of each counter relative to the laser-emitted time. We carefully tested all the components and procedures prior to the actual operation. The laser system was installed into the pTC and thoroughly tested under the real experimental condition. The system showed good stability and being sensitive to any change of timing larger than ∼10ps. Moreover, it showed an uncertainty of 48ps in the determination of the time offsets, which meets our requirements. The new method provides an example of the implementation of a precise timing alignment for the new type of detectors enabled by the advance of SiPM technology.
CX3CR1, a G protein-coupled receptor solely expressed by microglia in the brain, has been repeatedly reported to be associated with neurodevelopmental disorders including schizophrenia (SCZ) and ...autism spectrum disorders (ASD) in transcriptomic and animal studies but not in genetic studies. To address the impacts of variants in CX3CR1 on neurodevelopmental disorders, we conducted coding exon-targeted resequencing of CX3CR1 in 370 Japanese SCZ and 192 ASD patients using next-generation sequencing technology, followed by a genetic association study in a sample comprising 7054 unrelated individuals (2653 SCZ, 574 ASD and 3827 controls). We then performed in silico three-dimensional (3D) structural modeling and in vivo disruption of Akt phosphorylation to determine the impact of the detected variant on CX3CR1-dependent signal transduction. We detected a statistically significant association between the variant Ala55Thr in CX3CR1 with SCZ and ASD phenotypes (odds ratio=8.3, P=0.020). A 3D structural model indicated that Ala55Thr could destabilize the conformation of the CX3CR1 helix 8 and affect its interaction with a heterotrimeric G protein. In vitro functional analysis showed that the CX3CR1-Ala55Thr mutation inhibited cell signaling induced by fractalkine, the ligand for CX3CR1. The combined data suggested that the variant Ala55Thr in CX3CR1 might result in the disruption of CX3CR1 signaling. Our results strengthen the association between microglia-specific genes and neurodevelopmental disorders.
To evaluate the factors causing glucose intolerance in type 2 diabetes in Japan, insulin secretion and insulin sensitivity were compared across the range of glucose tolerance. Subjects were divided ...into 3 groups: normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes (DM) according to the criteria of the World Health Organization (WHO). We examined insulin secretion and insulin sensitivity using fasting blood glucose and insulin levels and 75 g oral glucose tolerance test (OGTT). We used homeostasis model assessment (HOMA) β-cell and insulinogenic index (30 minutes) to estimate insulin secretion and HOMA-insulin resistance (IR) and insulin sensitivity index (ISI) composite for insulin sensitivity. Although insulin resistance plays an important role in the development of diabetes in many ethnic populations, the differences in insulin sensitivity between NGT and IGT and between IGT and DM are small in Japanese patients. On the other hand, as glucose intolerance increases, insulin secretion decreases most remarkably both between NGT and IGT and between IGT and DM in Japanese patients. Decreasing insulin secretion and decreasing insulin sensitivity both occur in developing type 2 diabetes in Japanese patients, but decreased basal and early-phase insulin secretion had more pronounced contribution to glucose tolerance than the indices of insulin sensitivity. Japanese type 2 diabetic patients are characterized by a larger decrease in insulin secretion and show less attribution of insulin resistance.
Summary
Postoperative pulmonary complications (PPCs) after esophagectomy have been reported to occur in 15.9–30% of patients and lead to increased postoperative morbidity and mortality, prolonged ...duration of hospital stay, and additional medical costs. The purpose of this retrospective cohort study was to investigate the possible prevention of PPCs by intensive preoperative respiratory rehabilitation in esophageal cancer patients who underwent esophagectomy. The subjects included 100 patients (87 males and 13 females with mean age 66.5 ± 8.6 years) who underwent esophagectomy. They were divided into two groups: 63 patients (53 males and 10 females with mean age 67.4 ± 9.0 years) in the preoperative rehabilitation (PR) group and 37 patients (34 males and 3 females with mean age 65.0 ± 7.8 years) in the non‐PR (NPR) group. The PR group received sufficient preoperative respiratory rehabilitation for >7 days, and the NPR group insufficiently received preoperative respiratory rehabilitation or none at all. The results of the logistic regression analysis and multivariate analysis to correct for all considerable confounding factors revealed the rates of PPCs of 6.4% and 24.3% in the PR group and NPR group, respectively. The PR group demonstrated a significantly less incidence rate of PPCs than the NPR group (odds ratio: 0.14, 95% confidential interval: 0.02 ∼ 0.64). Correction added after online publication 25 June 2012: confidence interval has been changed from −1.86 ∼ −0.22 This study showed that the intensive preoperative respiratory rehabilitation reduced PPCs in esophageal cancer patients who underwent esophagectomy.
The MEG II experiment (Baldini et al., 2018) 1 is designed to improve the sensitivity to the μ+→e+γ decay. A crucial component is the Pixelated Timing Counter (pTC), dedicated to the measurement of ...the positron time to reduce the combinatorial background (Cattaneo et al., 2014; Nishimura et al., 2016) 3,4. The detector consists of 512 scintillation counters, each performing a precise measurement of the positron crossing time. This approach requires that the time offsets of the counters are calibrated and regularly monitored over the lifetime of the experiment. The pTC time calibration and monitor system will use a laser diode to deliver pulses to each pixel. The system components have been tested in laboratory, the results demonstrate that a calibration and monitoring resolution satisfying the requirements is within reach.
The MEG II experiment is designed to improve by an order of magnitude the sensitivity of 4.2×10−13 reached by MEG on the search for μ+→e+γ decay. A pixelated Timing Counter (pTC) has been developed ...to improve the time resolution by measuring the positron time information independently with several counters. We constructed and installed the pTC and performed commissioning runs at the πE5 beam line at PSI. A resolution of 38.5 ps is obtained with commissioning run data.
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