In the Standard Model the three charged leptons are identical copies of each other, apart from mass differences, and the electroweak coupling of the gauge bosons to leptons is expected to be ...independent of the flavour. This prediction is called lepton flavour universality (LFU) and is well tested in tree-level decays; any violation of LFU would be a clear sign of physics beyond the Standard Model. Experimental tests of LFU in semileptonic decays of b hadrons and in rare b decays are highly sensitive to models of New Physics in which new, heavy particles couple preferentially to the 2nd and 3rd generations of leptons. Recent results from LHCb on LFU in semileptonic b→cℓv transitions and rare b→sℓℓ decays are discussed.
Direct Dark Matter searches are nowadays one of the most fervid research topics with many experimental efforts devoted to the search for nuclear recoils induced by the scattering of Weakly ...Interactive Massive Particles (WIMPs). Detectors able to reconstruct the direction of the nucleus recoiling against the scattering WIMP are opening a new frontier to possibly extend Dark Matter searches beyond the neutrino background. Exploiting directionality would also prove the galactic origin of Dark Matter with an unambiguous signal-to-background separation. Indeed, the angular distribution of recoiled nuclei is centered around the direction of the Cygnus constellation, while the background distribution is expected to be isotropic. Current directional experiments are based on gas TPC whose sensitivity is limited by the small achievable detector mass. In this paper we present the discovery potential of a directional experiment based on the use of a solid target made of newly developed nuclear emulsions and of optical read-out systems reaching unprecedented nanometric resolution.
Recent developments of the nuclear emulsion technology led to the production of films with nanometric silver halide grains suitable to track low energy nuclear recoils with submicrometric length. ...This improvement opens the way to a directional Dark Matter detection, thus providing an innovative and complementary approach to the on-going WIMP searches. An important background source for these searches is represented by neutron-induced nuclear recoils that can mimic the WIMP signal. In this paper we provide an estimation of the contribution to this background from the intrinsic radioactive contamination of nuclear emulsions. We also report the neutron-induced background as a function of the read-out threshold, by using a GEANT4 simulation of the nuclear emulsion, showing that it amounts to about 0.06 per year per kilogram, fully compatible with the design of a 10 kg × year exposure.
Improving the detection efficiency in nuclear emulsion trackers Alexandrov, A.; Bozza, C.; Buonaura, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2015, Letnik:
776
Journal Article
Recenzirano
Nuclear emulsion films are a tracking device with unique space resolution. Their use in nowadays large-scale experiments relies on the availability of automated microscope operating at very high ...speed. In this paper we describe the features and the latest improvements of the European Scanning System, a last-generation automated microscope for emulsion scanning. In particular, we present a new method for the recovery of tracking inefficiencies. Stacks of double coated emulsion films have been exposed to a 10GeV/c pion beam. Efficiencies as high as 98% have been achieved for minimum ionising particle tracks perpendicular to the emulsion films and of 93% for tracks with tan(θ)≃0.8.
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.
Direct Dark Matter searches are nowadays one of the most fervid research topics with many experimental efforts devoted to the search for nuclear recoils induced by the scattering of Weakly ...Interactive Massive Particles (WIMPs). Detectors able to reconstruct the direction of the nucleus recoiling against the scattering WIMP are opening a new frontier to possibly extend Dark Matter searches beyond the neutrino background. Exploiting directionality would also prove the galactic origin of Dark Matter with an unambiguous signal-to-background separation. Indeed, the angular distribution of recoiled nuclei is centered around the direction of the Cygnus constellation, while the background distribution is expected to be isotropic. Current directional experiments are based on gas TPC whose sensitivity is limited by the small achievable detector mass. In this paper we present the discovery potential of a directional experiment based on the use of a solid target made of newly developed nuclear emulsions and of optical read-out systems reaching unprecedented nanometric resolution.
PDF
