1,721,180 research outputs found
The cylindrical drift chamber for the meg II
Full text linkThe MEG experiment, at PSI in Switzerland, aims at searching the charged lepton flavor violating
decay m+ ! e+g. MEG has already determined the world best upper limit on the branching ratio: BR<4.2×10−13
@90\%CL with the full data set collected in the years 2009-2013. The new positron tracker is a high transparency single volume, full stereo cylindrical Drift Chamber (DC), immersed in a non uniform longitudinal B-field, co-axial to the muon beam line with length of 1:93 m, internal radius of 17 cm and external radius of 30 cm. It is composed of 10 concentric
layers, divided in 12 identical sector of 16 drift cells each. The single drift cell is approximately
square, with a 20 mm gold plated W sense wire surrounded by 40 mm silver plated Al field wires in a ratio of 5:1. For equalizing the gain of the innermost and outermost layers, two guard layers have been added at proper radii and at appropriate high voltages. The total number of wires amounts to 12288 for an equivalent radiation length per track turn of about 1.45x10-3 X0 when the chamber is filled with an ultra-low mass gas mixture of helium and iso-butane. Due to the high wire density (12wires=cm2), the use of the classical feed-through technique as wire anchoring system could hardly be implemented and therefore it was necessary to develop new wiring strategies. The number of wires and the stringent requirements on the precision of their position and on the uniformity of the wire mechanical tension impose the use of an automatic system (wiring robot) to operate the wiring procedures. Several tests have been performed in different prototypes of the drift chamber, exposed to cosmic rays, test beams and radioactive sources, to fulfill the requirement on the spatial resolution to be less than 110 mm. The drift chamber is currently under construction at INFN and should be completed by the end of 2017 to be then delivered to PSI
The full stereo drift chamber for the MEG II experiment
No full textThe MEG experiment, at the Paul Scherrer Institute (PSI) near Zurich in Switzerland, aims at searching for the charged-lepton-flavor-violating decay μ+ → e+γ, prohibited in the Standard Model but allowed, at a measurable level, in many of its extensions. MEG has already determined the world best upper limit on the branching ratio: BR(μ+ → e+γ) < 4.2 × 10-13 at 90% CL with the full data set collected in the years 2009-2013. A further improvement of the MEG single event sensitivity requires a substantial upgrade of the detector performances and, in particular, the complete replacement of the positron tracker. The MEG upgrade experiment (MEG II) is currently under construction and it is conceived in order to further improve the sensitivity by one order of magnitude in three years of data taking. The new positron tracker is a high transparency single volume, full stereo cylindrical Drift Chamber, immersed in a non uniform longitudinal B-field, co-axial to the muon beam line. Due to the high wire density (12 wires/cm2), the use of the traditional feed-through technique as wire anchoring system could hardly be implemented and therefore it was necessary to develop new wiring strategies. The number of wires and the stringent requirements on the precision of their position and on the uniformity of the wire mechanical tension impose the use of an automatic system to operate the wiring procedures. The drift chamber is currently under construction at INFN Lecce and Pisa, and should be completed by the summer 2017 to be then delivered to PSI for commissioning. The upgraded detector, the new drift chamber and its construction technique, will be described
Influence of electron quantum confinement on the electronic response of metal/metal interfaces
No full textInsight on Thermally Activated Hydrocarbon Dehydrogenation on the Pt3Ni(111) Surface: From Adsorbed Hydrocarbons up to Graphene Formation
No full textObservation of carboxylic groups in the lattice of sintered Ba2YCu3O7-y high-Tc superconductors
No full textBorderline mucinous endocervical tumor as a link between the endometriotic cyst and ovarian primary squamous cell carcinoma.
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Probing collective excitations in graphene/metal interfaces by high-resolution electron energy loss spectroscopy measurements
No full textMany of the peculiar properties of graphene are related to its collective excitations, even if their understanding is still lacking. Plasmons are collective longitudinal modes of charge fluctuation in metal samples excited by an external electric field. Plasmons find applications in magneto-optic data storage, optics, microscopy, and catalysis. Plasmons in graphene have unusual properties and offer promising prospects for plasmonic applications covering a wide frequency range, going from terahertz up to the visible. On the other hand, lattice dynamics play an important role in many chemical and physical processes. The investigation of phonons in materials provides information on numerous properties, such as sound velocity, thermal expansion, magnetic forces, heat capacity, and thermal conductivity. High-resolution electron energy loss spectroscopy is the main experimental technique for investigating collective excitations (both plasmons and phonons), with adequate resolution in both the energy and momentum domains to investigate surface electronic excitations. This chapter discusses the status and the prospect of research on collective excitations (plasmons and phonons) in graphene epitaxially grown on metals. © 2016 by Taylor and Francis Group, LLC
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