The PTOLEMY programme

Wednesday 18 Jun 2025, 14:00 → 16:55 Europe/Rome

Aula B

This topical afternoon is dedicated to illustrating the PTOLEMY experimental project for the measurement of the relic neutrino cross section and the neutrino mass from Tritium decays. We will hear about the underlying theory aspects of condensed matter, about the experiment and the programme. We will also have 2 talks about the local activities at Roma Tre, including the project awarded in CSN5

• References:

1) M.G. Betti et al., "A Design for an Electromagnetic Filter for Precision Energy Measurements at the Tritium Endpoint”,
Progress in Particle and Nuclear Physics, 106, (2019) 120-131

2) M.G. Betti et al., "Neutrino physics with the PTOLEMY project”, Journal of Cosmology and Astroparticle Physics, 07, (2019) 047

1 Relic neutrinos detection and neutrino mass measurement in the PTOLEMY project

The Universe has expanded significantly since the early thermal epoch known as the neutrino decoupling era, one second after the start.
We have evidence of this expansion in many forms: the Hubble Expansion, the dim afterglow of the hot plasma epoch (Cosmic Microwave Background)
and the abundances of light elements (Big Bang Nucleosynthesis). The epoch of neutrino decoupling produced a fourth pillar of
confirmation – the Cosmic Neutrino Background (CNB). In our current understanding, the CNB was created in the first second after
elementary particles spontaneously filled the void of the early Universe. Recent experimental advances open up new opportunities to
directly detect the CNB through the process of neutrino capture on tritium, an achievement which would profoundly extend the sensitivity
of precision cosmology data. PTOLEMY, an experiment at the Gran Sasso National Laboratory in Italy, is a novel method of 2D target
surfaces, fabricated from graphene, that forms a basis for a large-scale relic neutrino detector. Recent PTOLEMY publications [1,2] describe
the underlying technique for achieving CNB sensitivity and redefines the future direction of neutrino mass measurements. The discussion
of PTOLEMY focusses on experimental challenges, recent developments and the path forward to discovery sensitivity.

Speaker: Marcello Messina (Istituto Nazionale di Fisica Nucleare)

R3_Seminar.pptx

2 The theory of PTOLEMY

In presence of a solid state substrate, the spectrum of the β-processes of tritium is qualitatively different from that expected in vacuum. I will review the conceptual and technical aspects of the inclusion of condensed matter effects on such a spectrum. For the case of β-decay, an accurate account of these effects is of utmost importance to successfully constrain the value of the neutrino mass. For the case of neutrino absorption, instead, these effects can raise some conceptual difficulties. I will discuss them and streamline the general direction one needs to follow to try to overcome them.

Speaker: Angelo Esposito (Istituto Nazionale di Fisica Nucleare)

Ptolemy Rome3.pdf

15:25 Coffee break

3 The LASEC contribution to the Ptolemy project

The LASEC lab has been active in the physics of surfaces and interfaces since the origins of ROMA TRE having gained, among other things, extensive experience in the study of carbon-based nanostructures and in electrons sources and detectors. From the beginning of 2020s, the lab activities have met with INFN interest, in relation to neutrino physics experiments and dark matter. In particular, the laboratory has been involved in the Ptolemy experiment to which it contributes on two fundamental aspects. The research and preparation of a carbon-based sample capable of hosting the highest hydrogen concentration (therefore of tritium with which it shares the same chemical properties) and on the other hand the detection of low-energy electrons. The first is a typical field of study in condensed matter physics in which fundamental properties of hydrogenated carbon-based materials, not yet fully understood, meet with the application of these materials to neutrino physics and beyond. The second arises from the specific expertise present within the LASEC lab in which the attention to the development of instrumentation has always been a distinctive feature.

Speaker: Alessandro Ruocco (Istituto Nazionale di Fisica Nucleare)

2025_Ptolemy_RomaTre.pdf

4 GRaphene to Electrons: Energy and Angular resolved Transmission

The scattering cross-section for the electron-graphene interaction is nowadays still an unknown quantity. Its measurement could pave the way in a variety of applications, from the upgrade of micro pattern gaseous detectors to the development of novel detectors for the neutrino physics (PTOLEMY experiment). The GREEAT project, an INFN - Università Roma Tre new collaboration, has the principal and extremely challenging aim to give the first measurement of the total and differential cross-section for the interaction of low-energy electrons with graphene.

Speaker: Alice Apponi (Istituto Nazionale di Fisica Nucleare)

GREEAT_AA_PTday.pdf