Search

The Positron Annihilation to Dark Matter Experiment (PADME) uses the positron beam of the DA$\Phi$NE Beam-Test Facility, at the Laboratori Nazionali di Frascati (LNF) to search for a Dark Photon $A'$. The search technique studies the missing mass spectrum of single-photon final states in $e^+e^-\rightarrow A'\gamma$ annihilation in a positron-on-thin-target experiment. This approach facilitates searches for new particles such as long lived Axion-Like-Particles, protophobic X bosons and Dark Higgs. This talk illustrated the scientific program of the experiment and its first physics results. In particular, the measurement of the cross-section of the SM process $e^+e^-\rightarrow \gamma\gamma$ at $\sqrt{s}$=21 MeV was shown., Comment: Fixed typos and updated gamma gamma results from preliminary ones to published ones. 6 pages, 6 figures, conference proceedings to be published in SciPost

To search for the production of a dark photon ($A^{\prime} $) in the process ${e}^{+}{e}^{-}\to A^{\prime} \gamma $, the PADME apparatus has been built athe INFN Laboratori Nazionali di Frascati. It is a small-scale detector consisting of an active target, a beam monitor system, a spectrometer to measure charged particle momenta in the range 50–400 MeV, a dipole magnet to deflect the primary positron beam out of the spectrometer and allow charged particle momentum analysis and an electromagnetic calorimetric system to detect signal and background photons produced in the annihilations with high accuracy. Each element has specific requirements that are stringent and sometimes at the limit of present technology. This proceeding will give an overview of each component and a description of the technical solutions implemented to accomplish the experiment needs. Results of the commissioning data taking, performed from October 2018 to February 2019, will be illustrated.

A large size, thin, high-quality polycrystalline diamond slab was used to build the full carbon active target of the PADME experiment. PADME is searching for a dark photon of mass up to 23.7 MeV, with a 550 MeV pulsed positron beam provided by the Beam Test Facility of the Laboratori Nazionali di Frascati. The target was built in the laboratories of INFN Lecce and University of Salento by realizing graphitic strips on both sides of a commercial CVD diamond sensor of 2 × 2 cm2 cross section and 100 microns thickness, by means of a UV excimer laser. The strips, with 1 mm pitch and oriented in orthogonal directions on the two surfaces, allow to reconstruct two views of the beam profile and to evaluate the particle multiplicity of each bunch. The detector was operated from September 2018 to end of February 2019. Here a review of the status, the operation experience, and the performance of the device in the PADME experiment is presented.

Among the theoretical models addressing the dark matter problem, the category based on a secluded sector is attracting increasing interest. The PADME experiment, at the Laboratori Nazionali di Frascati (LNF) of INFN, is designed to be sensitive to the production of a low mass gauge boson A of a new U(1) symmetry holding for dark particles. The “dark photon” is weakly coupled to the photon of the Standard Model, and it provides an experimental signature for one of the simplest implementation of the dark sector paradigm. The DAΦNE Beam-Test Facility of LNF will provide a high intensity, mono-energetic positron beam impacting on a low Z target. The PADME detector will measure with high precision the momentum of the photon, produced along with A boson in e+e − annihilation in the target, thus allowing to measure the A mass as the missing mass in the final state. This technique, particularly useful in case of invisible decays of the A boson, will be exploited for the first time in a fixed target experiment. Simulation studies predict a sensitivity on the interaction strength (2 parameter) down to 10 −6, in the mass region 1MeV< MA < 23.7MeV, for one year of data taking with a 550MeV beam. In 2018 the first run will take place, and early data will give the opportunity to compare the detector performance with the design requirements.