An 800
l liquid xenon scintillation
γ
-ray detector is being developed for the MEG experiment which will search for
μ
+
→
e
+
γ
decay at the Paul Scherrer Institut. Absorption of scintillation light ...of xenon by impurities might possibly limit the performance of such a detector. We used a 100
l prototype with an active volume of
372
×
372
×
496
mm
3
to study the scintillation light absorption. We have developed a method to evaluate the light absorption, separately from elastic scattering of light, by measuring cosmic rays and
α
sources. By using a suitable purification technique, an absorption length longer than 100
cm has been achieved. The effects of the light absorption on the energy resolution are estimated by Monte Carlo simulation.
Our 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 7.5×1014 stopped muons on target are presented. Furthermore, there was not a significant excess of events 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.
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
.
We present the final results obtained by the MACRO experiment in the search for GUT magnetic monopoles in the penetrating cosmic radiation, for the range \(4\times 10^{-5}< \beta < 1\). Several ...searches with all the MACRO sub-detectors (i.e. scintillation counters, limited streamer tubes and nuclear track detectors) were performed, both in stand alone and combined ways. No candidates were detected and a 90% Confidence Level (C.L.) upper limit to the local magnetic monopole flux was set at the level of \(1.4\times 10^{-16}\) cm-2 s-1 sr-1. This result is the first experimental limit obtained in direct searches which is well below the Parker bound in the whole \(\beta\) range in which GUT magnetic monopoles are expected.
The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay mu super(+) arrow right e super(+) gamma by using one of ...the most intense continuous mu super(+) beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.
The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay μ.sup.+ → e.sup.+γ by using one of the most intense ...continuous μ.sup.+ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a super-conducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.
The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay mu ^sup +^arrow righte^sup +^ γ by using one of the most ...intense continuous mu ^sup +^ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.
The Chooz experiment has recently started data taking and will soon start measuring the neutrino flux from two nuclear power reactors at an average distance of 1 km, aiming at discovering possible ...neutrino oscillations. A hardware implementation of a neural network algorithm was studied and built in order to rapidly (≈ 200 μs) reconstruct the energy and the position of the events inside the detector. The performances of this system and preliminary results on the first experimental data are presented. The system can be used for a fast rejection of background events.
We built and operated a cryogenic facility for testing in liquid xenon the photomultipliers (PMTs) to be used in the electromagnetic calorimeter of the MEG experiment. In this paper we describe the ...working principle of the facility and we report on the characteristics measured for some PMTs.
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