A search for the decay
μ
+
→
e
+
γ
, performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of
BR
(
μ
+
→
e
...+
γ
)
⩽
2.8
×
10
−
11
(90% C.L.). This corresponds to the measurement of positrons and photons from
∼
10
14
stopped
μ
+
-decays by means of a superconducting positron spectrometer and a 900 litre liquid xenon photon detector.
Fabrication of field effect transistor based on carbon nanotubes Repetto, P; Dussoni, S; Gatti, F ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2004, Letnik:
520, Številka:
1-3
Journal Article
Recenzirano
In this work, we present the results in the production of single wall carbon nanotubes and their assembling in a prototype of field effect transistor. We have used techniques such as microlithography ...and thin films evaporation to prepare the circuit pattern, laser ablation to produce nanotubes, and a self-assembling method to obtain a good placement of nanotubes on the circuit. We have obtained a good connection between contacts by ropes of nanotubes, which enables us to measure the influence of gate electrical field on electrical transport in nanotubes. Using ropes of semiconductor nanotubes we obtain values of transconductance of about 10−4S. All measurements were taken at room temperature.
Ageing tests for the MEG II drift chamber Venturini, M.; Baldini, A.M.; Baracchini, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Letnik:
824
Journal Article
Recenzirano
Odprti dostop
The MEG II drift chamber will track positrons from μ+ decays in a very harsh environment. For testing the robustness of the chamber to ageing effects an irradiation facility was set up at INFN Pisa.
...•We built up an X-ray facility for ageing studies of particle detectors.•Stable irradiation conditions were obtained over one-month timescale.•A moderate gain loss is expected for the MEG II drift chamber.
The FOXFIRE liquid xenon detector research and development project Signorelli, G.; Dussoni, S.; Baldini, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
The FOXFIRE project (Feasibility Of a Xenon detector with Frontend for Ionization Real-time Extraction) aims at studying and developing new techniques for the detection of rare processes in ...elementary particle physics by means of condensed noble gases detectors. Particles in noble liquids release energy in both scintillation light and electron–ion pair formation. The combined usage of this information is being exploited by many research groups. We are studying the extension of these techniques towards high-rate, high-energy (tens of MeV) environments with particular emphasis on real-time event reconstruction.
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 small size ...tracking prototypes, a high resolution cosmic ray tracker has been assembled to provide an external track reference. It consists of four spare ladders of the external layers of the Silicon Vertex Tracker of the BaBar experiment. The test facility, operating at INFN Sezione di Pisa, provides the detector under test with an external track with an intrinsic resolution of 15–30μm. The MEG II tracker is conceived as a unique volume wire drift chamber filled with He–isobutane 85–15%. The ionization density in this gas mixture is about 13clusters/cm and this results in a non-negligible bias of the impact parameters for tracks crossing the cell close to the anode wire. We present the telescope performance in terms of tracking efficiency and resolution and the results of the characterization of a MEG II drift chamber prototype.
Timing resolution measurements of a 3in. lanthanum bromide detector Galli, L.; De Gerone, M.; Dussoni, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
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 μ→eγ or μ→e conversion. While energy resolution was thoroughly investigated, timing resolution at several MeV presents some experimental challenge. We measured the timing resolution of a 3in.×3in. cylindrical LaBr3(Ce) crystal versus few reference detectors by means of a nuclear reaction from a Cockcroft–Walton accelerator that produces coincident γ-rays in the 4.4–11.6MeV range. Preliminary results allow us to extrapolate the properties of a segmented γ-ray detector in the 50–100MeV range.
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 Formula omitted. 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 Formula omitted by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be Formula omitted 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 Formula omitted search induced by the muon radiative decay: Formula omitted.
A new cylindrical drift chamber for the MEG II experiment Baldini, A.M.; Baracchini, E.; Berretta, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Letnik:
824
Journal Article
Recenzirano
Odprti dostop
A new cylindrical drift chamber is currently under construction for the MEG II experiment. The chamber is meant to track low momentum positrons from μ+ decays to search for μ+→e+γ events. The ...detector is segmented in very small drift cells, placed in stereo configuration and operated in a helium–isobutane gas mixture. The use of thin aluminium wires and light gas mixture set the total radiation length of the chamber to only 1.6×10−3X0 per track turn allowing for a momentum resolution of ~120keV/c.
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.
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