Technical design of the phase I Mu3e experiment Arndt, K.; Augustin, H.; Baesso, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2021, Letnik:
1014
Journal Article
Recenzirano
Odprti dostop
The Mu3e experiment aims to find or exclude the lepton flavour violating decay μ→eee at branching fractions above 10−16. A first phase of the experiment using an existing beamline at the Paul ...Scherrer Institute (PSI) is designed to reach a single event sensitivity of 2⋅10−15. We present an overview of all aspects of the technical design and expected performance of the phase I Mu3e detector. The high rate of up to 108 muon decays per second and the low momenta of the decay electrons and positrons pose a unique set of challenges, which we tackle using an ultra thin tracking detector based on high-voltage monolithic active pixel sensors combined with scintillating fibres and tiles for precise timing measurements.
We demonstrate efficient transverse compression of a 12.5 MeV/c muon beam stopped in a helium gas target featuring a vertical density gradient and crossed electric and magnetic fields. The muon stop ...distribution extending vertically over 14 mm was reduced to a 0.25 mm size (rms) within 3.5 μs. The simulation including cross sections for low-energy μ+-He elastic and charge exchange (μ+↔ muonium) collisions describes the measurements well. By combining the transverse compression stage with a previously demonstrated longitudinal compression stage, we can improve the phase space density of a μ+ beam by a factor of 1010 with 10−3 efficiency.
A novel device to compress the phase space of a muon beam by a factor of
10
10
with a
10
-
3
efficiency is under development. A surface muon beam is stopped in a helium gas target consisting of ...several compression stages, wherein strong electric and magnetic fields are applied. The spatial extent of the stopped muon swarm is decreased by means of these fields until muons with eV energy are extracted into vacuum through a small orifice. It was observed that a 20 cm long muon stop distribution can be compressed in the longitudinal direction to a sub-mm extent within
2
μ
s
. Additionally, a drift perpendicular to the magnetic field of the compressed low-energy muon swarm was successfully demonstrated, paving the way towards extraction from the gas and re-acceleration of the muons.
We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X,
μ
+
→
e
+
X
,
X
→
γ
γ
. This search uses a dataset resulting from
7.5
×
10
14
stopped ...muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c
2
for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c
2
, down to
O
(
10
-
11
)
at 90% confidence level.
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.
The time resolution of a fast scintillation counter, consisting of a plastic scintillator read out by a Geiger-mode Avalanche Photodiode, is studied over a wide range of the number of detected ...photons (primary photoelectrons) using the GEANT4 simulation toolkit. Different timing definitions such as first photon detection, leading edge and constant fraction discrimination are considered. In the latter case the predictions are compared with the existing experimental data. We also show that due to the finite scintillation rise time, finite scintillator dimensions and also due to the finite single photon time resolution in G-APD cells, the time resolution for the first detected photon in real detectors substantially deviates from the σ∼1/Nphe dependence, theoretically predicted for a scintillator with zero rise time.
This article deals with problems related with the role of the social coherence in the Social Worker-Client interaction. Special attention is drawn to the medico-biological principles of the social ...coherence as a process facilitating the interaction in this system. Modern concepts for an effective communication include not only the successful verbal transmission and reception of information, but also perception of the emotions by both parties, i.e. the person transmitting the information and the person receiving the information.
This article deals with the dynamics of personality changes in people serving a prison sentence whereas these changes are as result of the social work performed in prisons. Analyzed are some ...personality characteristics displayed in the context of emotional intelligence and social empathy in people with delinquent behavior of different age and of different social, educational, psychosomatic and family status.
We review a case of total penile skin replacement with split-thickness micromesh skin graft (micromesh STSG) due to paraffinoma.
•Split thickness skin graft is often used to restore penile ...skin.•Micromeshed split thickness skin graft has excellent cosmetic results for penile reconstruction.•Micromeshed split thickness skin graft has the advantages of meshed and unmeshed autograft.
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