Constraining cosmic antinuclei fluxes for indirect dark matter searches with precision measurements of rare antimatter cluster formation

Project Information

CosmicAntiNuclei

Grant agreement ID: 950692

DOI

10.3030/950692

EC signature date 5 February 2021

Start date 1 July 2021

End date 30 June 2027

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 468 625,00

EU contribution

€ 1 468 625,00

Coordinated by

ALMA MATER STUDIORUM - UNIVERSITA DI BOLOGNA
Italy

Periodic Reporting for period 3 - CosmicAntiNuclei (Constraining cosmic antinuclei fluxes for indirect dark matter searches with precision measurements of rare antimatter cluster formation)

Reporting period: 2024-07-01 to 2025-12-31

Summary of the context and overall objectives of the project

The CosmicAntiNuclei project aims at elucidating the production mechanisms of light antinuclei in high-energy interactions by leveraging precision measurements possible at the CERN’s Large Hadron Collider, with significant implications for cosmic ray studies and indirect dark matter searches. The project has strong experimental component involving measurements of antihelium in high-energy proton-proton and heavy-ion collisions and studies of the particle emitting source with the ALICE detector, as well as a modelling component for understanding the production and propagation mechanisms of light antinuclei in the Galaxy.
Dark matter, constituting 27% of the mass-energy content of the Universe, remains a central open question in modern science. If dark matter consists of weakly interacting massive particles (WIMPs), scientists aim to indirectly trace it by observing particles and antiparticles from the Standard Model produced through WIMP decay or annihilation. Light antinuclei such as antideuterons and antihelium nuclei in cosmic rays are considered promising signals for these searches due to the very low background expected from ordinary cosmic ray interactions with the interstellar matter. The absence of observed antideuteron or anti-helium in cosmic rays prompts searches with space-based experiments like AMS and GAPS, making calculations of the flux of antinuclei near Earth crucial for these endeavours.

Using precision measurements of rare antihelium production at the CERN LHC's ALICE detector, combined with information on the nucleon emitting source accessed by measuring particle final-state correlations in momentum, the project employs an innovative approach explore antinuclei formation through coalescence.
The objective is to inform models of antinuclei formation and propagation in the Galaxy, contributing to predictions for cosmic ray antideuteron and antihelium background rates. Ultimately, this research enhances knowledge of light nuclei and antinuclei production in high-energy interactions, extending the ALICE and LHC physics program into the astrophysical domain and pave the way for future low energy experiments. The project's outcomes are expected to have a significant impact on indirect dark matter searches and contribute to frontier research in this field.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project started in mid-2021, before the restart of the Large Hadron Collider (LHC) operations of Run 3 after a long technical shutdown during which the ALICE detector equipment was significantly upgraded. The team took part first in the recommissioning of the ALICE detector and, soon after, in operations with beams, actively participating in data acquisition and addressing various technical aspects, including detector calibration, data quality monitoring and analysis software development. The focus was on the calibration of the Time-Of-Flight system and optimisation of particle identification for light (anti)nuclei.
First, measurements of deuteron in proton-proton (pp) collisions at a centre-of-mass of √s = 5.02 TeV and 13 TeV with ALICE, based on the LHC Run 2 data, were released in two publications, adding to a comprehensive set of precision measurements of deuteron at high energy.
Secondly, the first pilot beam data from the LHC Run3 of pp collisions at 900 GeV were analysed for the measurement of (anti)proton and (anti)deuteron yields, and two-proton correlations to obtain the first ever measurement of the proton emitting source at this energy. Analysis of the very first data from the new detector was crucial for understanding detector effects and testing the calibration, the reconstruction as well as the analysis chain.
As soon as data in proton-proton collisions at √s = 13.6 TeV became available, we started a new analysis targeting helium-3 production: promising preliminary results were obtained in 2023 and the analysis is progressing integrating more data. In parallel, a new analysis has started to obtain a measurement of the proton source size in lead-lead (Pb-Pb) collisions, using the first sample of Run 3 data collected in 2023 and exploring nucleon-nucleon correlations, an aspect which is crucial for our studies of light nuclear cluster formation.
To model the formation of deuteron, helium, and their antimatter counterparts, the team investigates the coalescence production mechanism. This mechanism suggests nuclei form through final state interactions among nucleons emitted by the source. The team has developed a state-of-the-art coalescence model, implementing it in Monte Carlo event generators to simulate the event-by-event production of light nuclei, demonstrating the feasibility of the realistic approach employed. This was released in a publication in 2023. After this, development continues addressing the details of the coalescence approach and will be used to obtain predictions for light antinuclei production at energies beyond the LHC ones and in cosmic rays.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

In the first phase of the project, we successfully demonstrated that the production of antideuteron can be modelled if the particle emitting source is characterized realistically in terms of nucleon production and emission source size, which means also having control over correlations among nucleons within the source. Having confirmed the approach's effectiveness at high energy, our next step involves verifying its validity at other energies. Initially, we will combine ongoing deuteron and proton source measurements at √s = 900 GeV, the lowest energy at the LHC, which will serve also as a bridge to extend our model to lower energies.
Subsequently, we aim to conclude the ongoing measurements of helium-3 production at the highest LHC energy and delve into the study of the proton and deuteron-emitting source in heavy-ion collisions. With a comprehensive dataset on production yields of protons, deuterons, helium-3, two-particle correlations, and source radii across various collision systems and energies, our focus shifts to modeling the coalescence mechanism in these diverse scenarios. Simultaneously, we plan to further develop the model for predicting antinuclei production in cosmic ray and dark matter interactions.

Logo of the project