Target studies for surface muon production Berg, F.; Desorgher, L.; Fuchs, A. ...
Physical review. Accelerators and beams,
02/2016, Letnik:
19, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Meson factories are powerful drivers of diverse physics programs. With beam powers already in the MW-regime attention has to be turned to target and beam line design to further significantly increase ...surface muon rates available for experiments. For this reason we have explored the possibility of using a neutron spallation target as a source of surface muons by performing detailed Geant4 simulations with pion production cross sections based on a parametrization of existing data. While the spallation target outperforms standard targets in the backward direction by more than a factor 7 it is not more efficient than standard targets viewed under 90°. Not surprisingly, the geometry of the target plays a large role in the generation of surface muons. Through careful optimization, a gain in surface muon rate of between 30% and 60% over the standard “box-like” target used at the Paul Scherrer Institute could be achieved by employing a rotated slab target. An additional 10% gain could also be possible by utilizing novel target materials such as, e.g., boron carbide.
The MEG experiment has set the latest limit of 5.7×10−13(90% C.L.) on the branching ratio of the charged lepton flavor violating decay μ+→e+γ, making use of the most intense continuous surface muon ...beam in the world at the Paul Scherrer Institut (PSI), Villigen, Switzerland. High resolutions in terms of energy, timing and relative opening angle are needed in the detection of the e+ and gamma, requiring careful calibration and monitoring of the experimental apparatus. A dedicated calibration method involving Mott scattering of a monochromatic positron beam at energies close to the MEG signal energy is presented.
Mu3e is a dedicated experiment to search for the rare lepton flavour violating decay μ+→e+e−e+. Its ultimate goal is to find or exclude this process with a sensitivity of one in 1016 muon decays. ...This constitutes four orders of magnitude improvement with respect to the current state-of-the art. A thin multi-layer scintillating fibre detector consisting of 250μm fibres read out on both sides with silicon photomultiplier arrays provides an excellent time measurement with σ<500ps in order to reject combinatorial background at a muon stopping rate around 108 muon/s, concurrently minimizing the material budget to X/X0<0.3%. The design, performance and readout concept, including the dedicated readout chip MuTRiG, is presented.
The MEG experiment makes use of one of the world’s most intense low energy muon beams, in order to search for the lepton flavour violating process
μ
+
→
e
+
γ
. We determined the residual beam ...polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of energy. The initial muon beam polarization at the production is predicted to be
P
μ
=
-
1
by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be
P
μ
=
-
0.86
±
0.02
(
stat
)
-
0.06
+
0.05
(
syst
)
at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our
μ
+
→
e
+
γ
search induced by the muon radiative decay:
μ
+
→
e
+
ν
¯
μ
ν
e
γ
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The design of the MEG II experiment Baldini, A. M.; Baracchini, E.; Bemporad, C. ...
The European physical journal. C, Particles and fields,
05/2018, Letnik:
78, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The MEG experiment, designed to search for the
μ
+
→
e
+
γ
decay, completed data-taking in 2013 reaching a sensitivity level of
5.3
×
10
-
13
for the branching ratio. In order to increase the ...sensitivity reach of the experiment by an order of magnitude to the level of
6
×
10
-
14
, a total upgrade, involving substantial changes to the experiment, has been undertaken, known as MEG II. We present both the motivation for the upgrade and a detailed overview of the design of the experiment and of the expected detector performance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The final results of the search for the lepton flavour violating decay
μ
+
→
e
+
γ
based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and ...totalling
7.5
×
10
14
stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of
B
(
μ
+
→
e
+
γ
)
<
4.2
×
10
-
13
(90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The design of the MEG II experiment Baldini, A. M; Baracchini, E; Bemporad, C ...
European physical journal. C, Particles and fields,
05/2018, Letnik:
78, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The MEG experiment, designed to search for the Formula omitted decay, completed data-taking in 2013 reaching a sensitivity level of Formula omitted for the branching ratio. In order to increase the ...sensitivity reach of the experiment by an order of magnitude to the level of Formula omitted, a total upgrade, involving substantial changes to the experiment, has been undertaken, known as MEG II. We present both the motivation for the upgrade and a detailed overview of the design of the experiment and of the expected detector performance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
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.
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