The PADME experiment will search for the <inline-formula> <tex-math notation="LaTeX">e^{+} e^{-} \rightarrow \gamma A^{\prime } </tex-math></inline-formula> process in a positron-on-target ...experiment, assuming a decay of the <inline-formula> <tex-math notation="LaTeX">A^{\prime } </tex-math></inline-formula> into invisible particles of the hidden sector. The 550-MeV positron beam of the DA<inline-formula> <tex-math notation="LaTeX">\Phi </tex-math></inline-formula>NE beam-test facility (BTF), at Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, will be used. The suppression of the background, due to bremsstrahlung emission from the beam positrons, requires highly efficient charged-particle detectors with optimized geometry. A fine-grained plastic scintillator veto composed of three stations operating in vacuum is proposed. Two stations, placed inside a dipole magnet with 0.6-T magnetic field, will also provide momentum measurement at the percent level. Different prototypes for the design of the detector elements, the photosensor, and the front-end electronics were studied with single electron beam at the DA<inline-formula> <tex-math notation="LaTeX">\Phi </tex-math></inline-formula>NE BTF to choose the optimal technologies and construction solutions. PADME is currently under construction, and it is planned to begin data collection in 2018. The design of the charged-particle vetoes and the test beam performance of the prototypes are reviewed.
Abstract
The PADME experiment is designed to search for a
hypothetical dark photon
A
'
produced in positron-electron
annihilation using a bunched positron beam at the Beam Test Facility
of the INFN ...Laboratori Nazionali di Frascati. The expected
sensitivity to the
A
'
-photon mixing parameter
ϵ
is 10
-3
, for
A
'
mass ≤ 23.5 MeV/
c
2
after
collecting ∼ 10
13
positrons-on-target.
This paper presents the PADME detector status after commissioning in
July 2019. In addition, the software algorithms employed to
reconstruct physics objects, such as photons and charged particles,
and the calibration procedures adopted are illustrated in detail.
The results show that the experimental apparatus reaches the design
performance, and is able to identify and measure standard
electromagnetic processes, such as positron bremsstrahlung and
electron-positron annihilation into two photons.
The PADME experiment at the LNF Beam Test Facility searches for dark photons produced in the annihilation of positrons with the electrons of a fixed target. The strategy is to look for the reaction ...e++e−→γ+A′, where A′ is the dark photon, which cannot be observed directly or via its decay products. The electromagnetic calorimeter plays a key role in the experiment by measuring the energy and position of the final-state γ. The missing four-momentum carried away by the A′ can be evaluated from this information and the particle mass inferred. This paper presents the design, construction, and calibration of the PADME's electromagnetic calorimeter. The results achieved in terms of equalisation, detection efficiency and energy resolution during the first phase of the experiment demonstrate the effectiveness of the various tools used to improve the calorimeter performance with respect to earlier prototypes.
We developed a new technique for registration of the far solar corona from ground-based observations at distances comparable to those obtained from space coronagraphs. It makes possible visualization ...of fine details of studied objects invisible by naked eye. Here we demonstrate that streamers of the electron corona sometimes punch the dust corona and that the shape of the dust corona may vary with time.
We obtained several experimental evidences that the far coronal streamers (observed directly only from the space or stratosphere) emit only in discrete regions of the visible spectrum like resonance fluorescence of molecules and ions in comets. We found that interaction of the coronal streamers with the dust corona can produce molecules and radicals, which are known to cause the resonance fluorescence in comets.
Thermodynamic measurements on irradiated Na
2Fe(CN)
5NO
⋅
2H
2O reveal the existence of four light-induced long-lived metastable states, which decay exponentially in time. The activation energies and ...frequency factors of the four independent states are determined from isothermal calorimetric and differential scanning calorimetric measurements.
We have confirmed the solar origin of insolation cycles of 11,500, 4400, 3950, 2770, 2500, 2090, 1960, 1670, 1460, 1280, 1195, 1145, 1034, 935, 835, 750 and 610
yrs found in speleothem luminescence ...by their presence in other indices of the solar wind. The 11,500-yr solar cycle can produce climatic variations similar to those caused by the orbital variations.
We discovered a sub-annual cycle of 27 days in one very high-resolution speleothem proxy paleoclimatic record, attributed to solar rotation, which causes the periodic appearance of active zones on the visible solar surface, which are the major emitters of solar wind. Solar wind modulates cosmic ray flux at the Earth, while cosmic rays influence the atmospheric transparency, thus producing a multiplication of solar variations in insolation. Small variations of the solar activity can produce a measurable influence on insolation.
Performance of the PADME Calorimeter prototype at the DAΦNE BTF Raggi, M.; Kozhuharov, V.; Valente, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2017, Letnik:
862
Journal Article
Recenzirano
The PADME experiment at the DAΦNE Beam-Test Facility (BTF) aims at searching for invisible decays of the dark photon by measuring the final state missing mass in the process e+e−→γ+A′, with A′ ...undetected. The measurement requires the determination of the 4-momentum of the recoil photon, performed using a homogeneous, highly segmented BGO crystals calorimeter. We report the results of the test of a 5×5 crystals prototype performed with an electron beam at the BTF in July 2016.
In this communication we describe an approach for visualization and automatic counting of chemically etched tracks by means of a high-resolution computer scanner. The results from pilot experiments ...are presented, demonstrating that reliable automatic counting is possible, and the application of this approach for detectors like Kodak-Pathe LR-115/II and Makrofol is feasible.
The purity and the concentrations of the constituents Sr, Ba, Nb and Cr were determined in single crystals of chromium-doped Sr0.61Ba0.39Nb2O6 (SBN) by instrumental neutron activation analysis (INAA) ...and X-ray fluorescence analysis (XRF). Experiments with different Cr concentrations CCr reveal constant Sr and Ba concentrations as well as a decreasing Nb concentration with an increasing CCr. Therefore, Cr is incorporated at Nb lattice sites. The distribution coefficient of Cr is 1.2 between 100 and about 7000 ppm Cr and 1 above. From measurements of the holographic two-beam coupling gain *G for different CCr, we deduced response times for the buildup of holographic gratings. The saturation value of *G depends in a nonlinear manner on CCr and reaches its maximum at about 6000 ppm Cr. The inverse photorefractive response time of the grating erasure depends linearly on the erasure intensity for all doping concentrations. Thus a one-center model can be assumed for the charge transport in SBN:Cr.
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