Large-size Resistive Micromegas have been chosen for the upgrade of the forward muon spectrometer of the ATLAS experiment, the New Small Wheel project. These chambers, together with small-strip Thin ...Gap Chambers (sTGC), allow reconstruction of high-momentum muon tracks in a high-radiation environment and provide a robust low-threshold single-muon trigger. A collaboration of seven INFN units built 32 SM1 type chambers, corresponding to one fourth of the total number needed for this upgrade. Each SM1 chamber has a surface of approximately 2 m2 and four sensitive layers. The production was shared among five INFN construction sites and it was completed in fall 2020. The construction methods, as well as the results of the quality tests done on components of the detector and on the assembled chambers, are reported in the present paper.
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.
In a study of B+ --> J/psi gamma K+ decays, we find evidence for the radiative decay X(3872) --> J/psi gamma with a statistical significance of 3.4 sigma. We measure the product of branching ...fractions BF(B+ --> X(3872) K+).BF(X(3872) --> J/psi gamma) = (3.3 +/- 1.0 +/- 0.3) x 10^-6, where the uncertainties are statistical and systematic, respectively. We also measure the branching fraction BF(B+ --> chi_c1 K+) = (4.9 +/- 0.2 +/- 0.4) x 10^-4. These results are obtained from (287+/-3) million BBar decays collected at the Y(4S) resonance with the BaBar detector at the PEP-II B Factory at SLAC.
Abstract
PADME (Positron Annihilation into Dark Matter Experiment) is a fixed target experiment located at the Beam Test Facility (BTF) at the Laboratori Nazionali di Frascati (LNF) designed to ...search for a massive dark photon
A
′
in the process
e
+
e
−
→
γ
A
′
, using a positron beam of energy up to 550 MeV. The experiment exploits the missing mass technique which allows for a search of
A
′
in a model independent way. A sensitivity on the mixing constant
ϵ
> 10
−3
for a dark photon mass in the range
1
≤
m
A
′
≤
23.7
MeV
/c
2
can be achieved by collecting 4 × 10
13
positrons on target. Run 2 data taking finished in December 2020 and allowed to reach an integrated luminosity of 5 × 10
12
positrons on target.
Microfluidic channels obtained by SU-8 photolithography and filled with liquid scintillators were recently demonstrated to be an interesting technology for the implementation of novel particle ...detectors. The main advantages of this approach are the intrinsic radiation resistance resulting from the simple microfluidic circulation of the active medium and the possibility to manufacture devices with high spatial resolution and low material budget using microfabrication techniques. Here we explore a different technological implementation of this concept, reporting on scintillating detectors based on silicon microfluidic channels. A process for manufacturing microfluidic devices on silicon substrates, featuring microchannel arrays suitable for light guiding, was developed. Such process can be in principle combined with standard CMOS processing and lead to a tight integration with the readout photodetectors and electronics in the future. Several devices were manufactured, featuring microchannel geometries differing in depth, width and pitch. A preliminary characterization of the prototypes was performed by means of a photomultiplier tube coupled to the microchannel ends, in order to detect the scintillation light produced upon irradiation with beta particles from a super(90)Sr source. The photoelectron spectra thus obtained were fitted with the expected output function in order to extract the light yield.
The mass and total width of the eta_c meson have been measured in two-photon interactions at the SLAC asymmetric B-Factory with the BABAR detector. With a sample of approximately 2500 reconstructed ...eta_c -> Ks K pi decays in 88 fb-1 of data, the measured eta_c mass and width are respectively 2982.5 +- 1.1 (stat) +- 0.9 (syst) MeV/c2 and 34.3 +- 2.3 (stat) +- 0.9 (syst) MeV/c2. Using the same decay mode, a second resonance with 112 +- 24 events is observed with a mass of 3630.8 +- 3.4 (stat) +- 1.0 (syst) MeV/c2 and width of 17.0 +- 8.3 (stat) +- 2.5 (syst) MeV/c2. This observation is consistent with expectations for the eta_c(2S) state.
The charged particle veto system of the PADME experiment Oliva, F.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
Recenzirano
The PADME (Positron Annihilation into Dark Matter Experiment) will search for the production of a dark photon from positron–electron annihilation e+e−→γA′ using the positron beam of the Beam Test ...Facility (BTF) of the DAΦNE Linac at Laboratori Nazionali di Frascati (LNF). This paper presents the status of the charged particle veto system which is necessary to tag bremsstrahlung processes which are the main source of background events.
The calorimeters of the PADME experiment Gianotti, P.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
Recenzirano
The PADME experiment is under construction at the Frascati National Laboratories of INFN to explore the coupling between ordinary and dark matter. This will be done through the detection of Standard ...Model photons produced in the reaction e+e−→γA′. The measurement of the photons 4-momentum allows to reconstruct the missing mass spectrum of this process, where the A′ could appear as a peak. To this purpose, two independent electromagnetic calorimeters are used. The layout of the two detectors, and their expected performance measured during prototypes tests, are here presented.
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