We studied the radiative muon decay
μ
+
→
e
+
ν
ν
¯
γ
by using for the first time an almost fully polarized muon source. We identified a large sample (
∼
13,000) of these decays in a total sample of
...1.8
×
10
14
positive muon decays collected in the MEG experiment in the years 2009–2010 and measured the branching ratio
B
(
μ
→
e
ν
ν
¯
γ
)
=
(
6.03
±
0.14
(
stat
.
)
±
0.53
(
sys
.
)
)
×
10
-
8
for
E
e
>
45
MeV
and
E
γ
>
40
MeV
, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for
μ
+
→
e
+
γ
process.
The Timing Counter of the MEG (Mu to Electron Gamma) experiment is designed to deliver trigger information and to accurately measure the timing of the in searching for the decay . It is part of a ...magnetic spectrometer with the decay target in the center. It consists of two sectors upstream and downstream the target, each one with two layers: the inner one made with scintillating fibers read out by APDs for trigger and track reconstruction, the outer one consisting in scintillating bars read out by PMTs for trigger and time measurement. The design criteria, the obtained performances and the commissioning of the detector are presented herein.
The MEG timing counter calibration and performance De Gerone, M.; Dussoni, S.; Fratini, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Letnik:
638, Številka:
1
Journal Article
Recenzirano
The MEG experiment has been taking data at the Paul Scherrer Institute (Switzerland) since 2008 to search for the rare decay
μ
+
→
e
+
γ
. In order to reduce the huge accidental background, it is ...crucial to reach a high resolution on the
e
+ time measurement through a dedicated Timing Counter detector. We report the methods for calibrating and the performance achieved by the Timing Counter in the early phase of the experiment.
The MEG experiment at PSI searches for the decay
μ
→
e
γ
at a level of
≈
10
−
13
on the branching ratio
BR
(
μ
→
e
γ
/
μ
→
tot
), well beyond the present experimental limit (
BR
≤
1.2
×
10
−
11
) and ...is sensitive to the predictions of SUSY-GUT theories. To reach this goal the experiment uses one of the most intense continuous surface muon beams available (
≈
10
8
μ
/
s
) and relies on advanced technology (LXe calorimetry, a gradient-field superconducting spectrometer as well as flexible and powerful trigger and acquisition systems). In order to maintain the highest possible energy, time and spatial resolutions for such detector, frequent calibration and monitoring, using a Cockcroft–Walton proton accelerator, are required. The proton beam is brought to the centre of MEG by a special bellows insertion system and travels in a direction opposite to the one of the normal
μ
‐
beam
. Protons interact with a lithium tetraborate (Li
2B
4O
7) nuclear target and produce one
γ
(17.6
MeV) from the reaction
Li
(
p
,
γ
)
3
7
Be
4
8
or two coincident
γ
s
(11.67 and 4.4
MeV) from the reaction
B
(
p
,
γ
1
)
5
11
C
⁎
6
12
. The 17.6
MeV
γ
is used for calibrating and monitoring the LXe calorimeter (
σ
E
γ
/
E
γ
=
3.85
±
0.15
%
at 17.6
MeV) while the coincident 11.67 and 4.4
MeV
γ
s
are used to measure the relative timing of the calorimeter and the spectrometer timing counters (
σ
Δ
t
=
0.450
±
0.015
ns
).
►Experiments that search for rare phenomena need to be constantly monitor and calibrated. ►We show that proton induced nuclear reactions generate
γ
‐
rays
useful for calibrating and monitoring the MEG experiment. ►We describe the design, assembly and test of the calibration and monitoring accelerator for the MEG experiment.
Cerium-doped lanthanum bromide (LaBr3:Ce) is a scintillator that presents very good energy and timing resolutions and it is a perfect candidate for photon detector in future experiments to search for ...lepton flavor violation as in mu arrow right e gamma mu arrow right e gamma or mu arrow right e mu arrow right e conversion. While energy resolution was thoroughly investigated, timing resolution at several MeV presents some experimental challenge. We measured the timing resolution of a 3 in.3 in. cylindrical LaBr3(Ce) crystal versus few reference detectors by means of a nuclear reaction from a Cockcroft-Walton accelerator that produces coincident gamma gamma -rays in the 4.4-11.6 MeV range. Preliminary results allow us to extrapolate the properties of a segmented gamma gamma -ray detector in the 50-100 MeV range.
High-energy physics experiments at the high-intensity frontier place ever-greater demands on detectors, and in particular on tracking devices. In order to compare the performance of many possible ...small-size tracking prototypes, a high-resolution cosmic ray tracker may be used as an external track reference. We have constructed a telescope by assembling four spare ladders of the external layers of the Silicon Vertex Tracker of the BaBar experiment. This test facility, operating at INFN Sezione di Pisa, provides the detector under test with an external track with an intrinsic resolution of 15-30 μm. The DAQ originally used in the BaBar experiment was replaced by custom-designed boards coupled with an acquisition front-end personal computer through commercial field-programmable gate array evaluation boards. We show that the facility is operative, and we present the performance in terms of tracking resolution and efficiency. A first device has been characterized, and some plots from the analysis demonstrating the telescope performance are shown.
The Timing Counter of the MEG experiment: Design and commissioning Dussoni, S.; De Gerone, M.; Gatti, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
In the MEG experiment, the Timing Counter detector is designed to deliver trigger information and to accurately measure the time of flight of the e
+
for searching the exotic decay
μ
→
e
+
γ
. It ...consists of two sectors up and down stream the decay target. Each sector is made of two layers: scintillating fibers read by APD for trigger and track reconstruction in the inner side, scintillating bars with PMT readout for trigger and time measurement in the outer one. The design criteria and fabrication methods of the detector and electronics, the integration in the MEG apparatus and its performance in the qualification test are presented.
R&D on a Fast LXe TPC with real-time event reconstruction Dussoni, S.; Baldini, A.; Galli, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2013, Letnik:
732
Journal Article
Recenzirano
The FOXFIRE project (Feasibility Of a Xenon detector with Front-end for Ionization Real-time Extraction) aims at the realization of a Liquid Xenon TPC optimized for high rate particle physics ...experiments, in particular in the field of rare event searches, with particles in the 10–100MeV energy range. Liquid Xenon has several attractive properties to be exploited resulting in superior time and energy resolution, by using the scintillation light readout with suitable photo-detectors. A novel approach with a complementary TPC readout scheme can improve the space resolution to a level of a few hundred microns. We are studying both the feasibility of a light readout with higher granularity by means of Silicon PhotoMultipliers optimized for the Xenon emission spectrum as well as on an innovative micro-fabricated device capable of charge multiplication in liquid phase. The detector will be equipped with a readout electronics capable of online reconstruction of events, allowing the detector to sustain a high rate of interactions.
One of the main backgrounds in the search for 136Xe nutrino-less double-beta decay (0νββ) is the signal from Compton scattering of photons with energy around the decay endpoint at 2.458MeV. Electrons ...in liquid xenon emit scintillation light at 178nm. Liquid xenon being extremely transparent to ultra violet light it is in principle possible to discriminate one particle events (such as the Compton background) from two particle events (double-beta decay signals) by the amount of Cherenkov radiation emitted. The identification of the Cherenkov photons may be performed by looking at the different time structure of the signal with respect to the scintillation, by selecting photons with wavelengths larger than the typical Xenon scintillation light, and by the different emission topology. A proof-of-principle study of this approach is presented here together with preliminary studies on possible detectors for the two light components at different wavelengths.
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