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.
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.
While the performance of biological sensors in real time monitoring networks is limited to bulk values like chlorophyll fluorescence, in practice the implementation of automated phytoplankton ...taxonomy remains a remote option. Aiming to reduce this gap we developed a flow cytometer called CytoBuoy for autonomous in situ operation, for instance in a moored buoy with wireless data transfer. Although not comparable to microscopy, flow cytometers detect and count particles allowing a limited level of particle characterization based on the light scatter and fluorescence properties of the individual particles. CytoBuoy analyses a large size range of particles, typical for marine coastal zones and fresh waters. The `field' design implies a tradeoff between the accuracy and versatility of laboratory flow cytometers and the qualities needed for trouble free autonomous operation in situ. The optics and electronics however were designed for maximal reflection of the particle morphology in the measured signals. Whereas standard cytometers reduce these to single peak or area `listmode' numbers, the signal courses are preserved fully by CytoBuoy and transferred to the computer as raw data, which allows more extended morphological analysis. Extended field tests will have to show how the system holds in various environments and weather conditions.
The Mu3e scintillating fiber detector R&D Papa, A.; Rutar, G.; Barchetti, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
20/May , Letnik:
1050
Journal Article
Recenzirano
The Mu3e experiment searches for a rare lepton flavor violating μ+→e+e+e− decay and it aims at reaching an ultimate sensitivity of 10−16 on the branching fraction of the μ+→e+e+e− decay, four orders ...of magnitude better than the current limit B(μ+→e+e+e−)<10−12. The experiment will be hosted at the Paul Scherrer Institute (Villigen, Switzerland) which delivers the most intense low momentum continuous muon beam in the world (up to few ×108μ/s).
In order to achieve this unprecedent sensitivity new detector R&D have been performed. We will report about the Scintillating Fiber (SciFi) detector R&D aiming at a detector able to measure minimum ionizing particles with a highest as possible detection efficiency (>95%), timing resolutions well below 1 ns and spatial resolution of ≈100μm. The main challenge to address such a requirements is to keep the detector as thin as possible, to minimize the multiple scattering. Then the thickness of the detector must be below 0.4% of radiation length X0. It implies that the requirements listed above will be extracted measuring just a relative low number of photoelectrons. The results of several beam tests are given, proving that the requirements for the experiment has been addressed. These studies have been supported with detailed Monte Carlo simulations from the fiber through the photosensors up to the electronics and the data acquisition.
The Mu3e scintillating fiber timing detector Bravar, A.; Briggl, K.; Corrodi, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
Recenzirano
A new experiment, Mu3e, to search for charged Lepton Flavor Violation in the rare neutrinoless μ+→e+e+e− decay is in preparation at the Paul Scherrer Institute using the most intense continuous ...surface muon beam in the world. The Mu3e detector is based on thin monolithic active silicon pixel sensors (HV-MAPS) for very precise tracking in conjunction with scintillating fibers and scintillating tiles coupled to silicon photomultipliers (SiPMs) for accurate timing measurements and is designed to operate at very high intensities.
In order to reach a sensitivity of 10−16, all backgrounds must be rejected below this level. To suppress all forms of combinatorial background, a very thin (thickness ∼0.2% of a radiation length X0) Scintillating Fiber detector with few 100 ps time resolution, efficiency in excess of 96%, and spatial resolution of ∼100μm has been developed. In this paper we report on the development and performance of the fiber detector, from the scintillating fiber ribbons through the SiPM array photo-sensors up to the front end electronics.
Abstract The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay $$\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma $$ 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 $${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 7.5 \times 10^{-13}$$ B ( μ + → e + γ ) < 7.5 × 10 - 13 (90% CL). The combination of this result and the limit obtained by MEG gives $${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 3.1 \times 10^{-13}$$ 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.
Women with a deleterious germline mutation in BRCA1 or BRCA2 are candidates for bilateral salpingo-oophorectomy (BSO). To address the need for adjustment of the current BSO procedure, we investigated ...the length and the nature of the fallopian tube epithelium that is not removed by BSO. Fourteen consecutive hysterectomy specimens were collected. Complete cross-sections with a 3-mm interval were made of the tubal lumen from the outside of the uterus at the cutoff point of the current BSO procedure to the uterine cavity and examined for the presence or absence of tubal type (ciliated) epithelium and subepithelial endometrial stroma. The fallopian tube remnant had a median length of 12 mm (range 6-15 mm). Tubal type (ciliated) epithelium was shown to be present in all uteri in the first cross-section containing 100% endometrial stroma, as well as in the uterine cavity of all but two of the hysterectomy specimens. A substantial part of the fallopian tube remains in situ after prophylactic BSO and is covered with tubal type ciliated epithelium. More research is necessary to investigate the role of this remnant part of the tube for BRCA carriers.
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