3,307 research outputs found
Measuring Propagation Speed of Coulomb Fields
The problem of gravity propagation has been subject of discussion for quite a
long time: Newton, Laplace and, in relatively more modern times, Eddington
pointed out that, if gravity propagated with finite velocity, planets motion
around the sun would become unstable due to a torque originating from time lag
of the gravitational interactions.
Such an odd behavior can be found also in electromagnetism, when one computes
the propagation of the electric fields generated by a set of uniformly moving
charges. As a matter of fact the Li\'enard-Weichert retarded potential leads to
a formula indistinguishable from the one obtained assuming that the electric
field propagates with infinite velocity. Feyman explanation for this apparent
paradox was based on the fact that uniform motions last indefinitely.
To verify such an explanation, we performed an experiment to measure the
time/space evolution of the electric field generated by an uniformely moving
electron beam. The results we obtain on such a finite lifetime kinematical
state seem compatible with an electric field rigidly carried by the beam
itself.Comment: 23 pages, 15 figure
Beam test of scintillation tiles with MPPC readout
This paper describes measurements made using counters composed of a small (3 by 3 by 0.5 cm3) scintillation tile coupled to a Multi-Photon Pixel Counter (MPPC) produced by Hamamatsu and exposed to an electron beam at the Beam Test Facility in Frascati. We show our first results for charge spectra and efficiency, and a very preliminary measurement of device linearity
A new concept for streamer quenching in resistive plate chambers
In this paper we propose a new concept for streamer quenching in Resistive Plate Chambers (RPCs). In our approach, the multiplication process is quenched by the appropriate design of a mechanical structure inserted between the two resistive electrodes. We show that stable performance is achieved with binary gas mixtures based on argon and a small fraction of isobutane. Fluorocarbons, deemed responsible for the degradation of the electrode inner surface of RPC detectors, are thus fully eliminated from the gas mixture. This design {also resulted} in a simplified assembly procedure. Preliminary results obtained with a few prototypes of ``Mechanically Quenched RPCs'' and some prospects for future developments are discussed
A model to explain angular distributions of and decays into and
BESIII data show a particular angular distribution for the decay of the
and mesons into the hyperons
and . More in details the angular distribution of
the decay exhibits an opposite trend
with respect to that of the other three channels: , and
. We define a model to explain the
origin of this phenomenon.Comment: 6 pages, 7 figures, to be published in Chinese Physics
A Cylindrical GEM Inner Tracker for the BESIII experiment at IHEP
The Beijing Electron Spectrometer III (BESIII) is a multipurpose detector
that collects data provided by the collision in the Beijing Electron Positron
Collider II (BEPCII), hosted at the Institute of High Energy Physics of
Beijing. Since the beginning of its operation, BESIII has collected the world
largest sample of J/{\psi} and {\psi}(2s). Due to the increase of the
luminosity up to its nominal value of 10^33 cm-2 s-1 and aging effect, the MDC
decreases its efficiency in the first layers up to 35% with respect to the
value in 2014. Since BESIII has to take data up to 2022 with the chance to
continue up to 2027, the Italian collaboration proposed to replace the inner
part of the MDC with three independent layers of Cylindrical triple-GEM (CGEM).
The CGEM-IT project will deploy several new features and innovation with
respect the other current GEM based detector: the {\mu}TPC and analog readout,
with time and charge measurements will allow to reach the 130 {\mu}m spatial
resolution in 1 T magnetic field requested by the BESIII collaboration. In this
proceeding, an update of the status of the project will be presented, with a
particular focus on the results with planar and cylindrical prototypes with
test beams data. These results are beyond the state of the art for GEM
technology in magnetic field
A robust and powerful green light photoemission source: The ferroelectric ceramics
The photoemission characteristics of ceramic disks of lead zirconate titanate lanthanum doped (PLZT), have been investigated. We observe 1 nC of extracted charge under an accelerating field of 20 kV/cm in poor vacuum conditions. The emission is clearly limited by space charge effects. The extrapolated quantum efficiency results in ≈10−6. The yield of a PLZT ceramic in the ferroelectric state and its slope versus light intensity have turned out higher than those of antiferroelectric ceramic. Samples in different experimental configurations have shown different nonlinear yields
Test of large area glass RPCs at the DA Phi NE Test Beam Facility (BTF)
Abstract The CaPiRe program has been started to develop a new detector design, in order to produce large areas of glass Resistive Plate Chambers (RPC) detectors, overcoming the previous limitations. As a first step we produced our glass RPC detectors ( 1 m 2 ) at General Tecnica exploiting their standard procedures, materials and production techniques simply using 2 mm glass electrodes instead of the bakelite ones. A set of RPC was produced by using pre-coated (silk screen printed) electrodes, while others were produced with the standard graphite coating. All the detectors, together with four old Glass RPC acting as reference, were tested at the DA Φ NE Test Beam Facility with 500 MeV electrons in order to study the efficiency in different positions inside the detectors (i.e. near spacers and edges) and to study the detector behavior as a function of the local particle rate
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