Speaker
Danilo Domenici
(INFN - LNF)
Description
The Positron Annihilation into Dark Matter Experiment (PADME) aims to
search for the production of a dark photon in the process e + e → A 0 γ. It exploits
the 550 MeV positron beam provided by the DAΦNE LINAC impinging on a
thin target.
The primary beam crosses a diamond target and if it does not interact it
is bent by a magnet in between the end of the spectrometer and the calorime-
ter, thus leaving the experiment undetected. If any kind of interaction causes
the positron to lose more than 50 MeV of energy, the magnet bends it into the
spectrometer acceptance, providing a veto signals against bremsstrahlung back-
ground. In case of annihilation, the accompanying ordinary photon is detected
by the electromagnetic calorimeter regardless of the A 0 decay products. A single
kinematic variable characterizing the process, the missing mass, is computed
using the formula: M2 miss = (P beam + P e − − P γ ) 2
Its distribution should peak at M A 2 0 for A 0 decays, at zero for the concurrent
e + e → γγ process, and should be smooth for the remaining background.
To measure such a reaction, the PADME apparatus has been built at the Frascati
National Laboratory of INFN. It consists of a small scale detector composed of
the following parts:
• a diamond active target, to measure the position and the intensity of the
beam in each single bunch;
• a beam monitor system consisting of two different silicon-pixel detectors.
The first one, located at the beam entrance, can be inserted in place of
the target to tune beam parameters; the second, located on the beam exit
trajectory, monitors the beam spot during the data taking;
• a spectrometer, to measure the charged particles momenta in the range
50-400 MeV;
• a dipole magnet, to deflect the primary positron beam out of the spec-
trometer and the calorimeter and to allow momentum analysis;
• a vacuum chamber, to minimize the unwanted interactions of primary and
secondary particles;
• a finely segmented, high resolution electromagnetic calorimeter, to measure
4-momenta and veto final state photons.
Each element has specific requirements that are stringent and sometimes at the
limit of present technology.
A commissioning run has been performed between 2008 and 2019, and in Febru-
ary 2020 the experiment is expected to take data for two months.
The talk will give an overview of each detector component and a description
of the chosen technical solutions implemented to accomplish the experiment
needs. An insight of possible future upgrades will be given as well.
Primary author
Danilo Domenici
(INFN - LNF)
