Antonio MarroneTheoretical Physics · Bari

Research

Neutrino phenomenology

Neutrino phenomenology · Particle physics beyond the Standard Model · Astroparticle physics · Cosmology

Publications Analysis results INSPIRE-HEP

Research statement

Overview

I have been a researcher in theoretical physics from 2005 to 2015 and associate professor until 2023. I am currently Full Professor of Theoretical Physics at the University of Bari "Aldo Moro".

My research lies at the interface between neutrino physics, particle phenomenology and cosmology. With the Bari group I have contributed to a long line of global analyses of neutrino oscillation data, combining solar, atmospheric, reactor and accelerator experiments to extract the fundamental parameters of leptonic mixing with state-of-the-art precision.

As measurements enter the subpercent regime, these results sharpen the picture of the neutrino mass ordering, of leptonic CP violation and of the absolute neutrino mass scale, while probing possible signatures of physics beyond the three-neutrino paradigm.

Research theme 01

Global analysis of neutrino oscillations

Three-flavour fits to the world neutrino data, with a self-consistent treatment of solar, atmospheric, reactor and long-baseline accelerator experiments.

The observables are the two mass-squared splittings $\Delta m^2_{21}$ and $|\Delta m^2_{3\ell}|$ and the three mixing angles $\theta_{12}$, $\theta_{13}$, $\theta_{23}$ of the PMNS matrix, together with the CP-violating phase $\delta_{\rm CP}$. In vacuum the survival probability of a flavour eigenstate takes the familiar form

$$ P(\nu_\alpha \to \nu_\alpha) = 1 - 4\sum_{i<j} |U_{\alpha i}|^2 |U_{\alpha j}|^2 \sin^2\!\left(\frac{\Delta m^2_{ij} L}{4E}\right), $$

but the precision now attainable requires the full matter-effect treatment and a careful statistical combination of datasets with very different systematics.

Solar mixing angle
0.303 3σ: 0.264 – 0.345
sin²θ₁₂ · 4.5 % precision (1σ)
Reactor mixing angle
0.0223 3σ: 0.0206 – 0.0238
sin²θ₁₃ · 2.4 % precision (1σ)
Atmospheric mixing angle
0.473 3σ: 0.437 – 0.581
sin²θ₂₃ · first octant at 1.1σ, ambiguity persists
Solar splitting
7.37 ×10⁻⁵ eV²
δm² · 2.3 % precision (1σ)
Atmospheric splitting
2.495 ×10⁻³ eV²
|Δm²| · 0.8 % — the first 3ν parameter below 1 %
Leptonic CP phase
1.20 3σ: 0.73 – 2.03
δ/π · CP violation favoured at 1.3σ, still open

Normal-ordering best fits from Capozzi, Giarè, Lisi, Marrone, Melchiorri and Palazzo, Phys. Rev. D 111, 093006 (2025), Table 1; δm² = m₂² − m₁², Δm² = m₃² − (m₁² + m₂²)/2. NO is favoured over IO at 2.2σ. The 1σ precision is one sixth of the 3σ range.

Research theme 02

Mass ordering and leptonic CP violation

Statistical extraction of the leptonic CP phase $\delta_{\rm CP}$ and of the sign of $\Delta m^2_{3\ell}$ from the interplay of T2K, NOvA, reactor and atmospheric data. The two datasets pull in partly different directions, and the resulting significance depends delicately on how their systematics are combined.

A related strand is forecasting the discovery reach of the next generation of experiments — JUNO, DUNE and Hyper-Kamiokande — and identifying which combinations of measurements would resolve the ordering and the $\theta_{23}$ octant with the least model dependence.

Diagram comparing the normal and inverted neutrino mass orderings, with the flavour composition of each mass eigenstate shown as coloured fractions.
The neutrino mass spectrum, with the flavour composition $|U_{\alpha i}|^2$ of each eigenstate coded by colour. Whether $\nu_3$ sits at the top (normal) or at the bottom (inverted) is one of the open questions our global fits aim to resolve.

Research theme 03

Absolute neutrino masses and cosmology

Oscillation experiments are sensitive only to mass-squared differences. The absolute scale is constrained instead by three complementary probes: the endpoint of the β-decay spectrum, which measures the effective mass $m_\beta$; searches for neutrinoless double-β decay, sensitive to the Majorana mass $\langle m_{\beta\beta} \rangle$; and cosmological observations of the CMB and of large-scale structure, which bound the sum $\Sigma = \sum_i m_i$.

Combining these with the oscillation results is a genuinely statistical problem, since the three observables depend on different combinations of the same underlying parameters and carry very different systematics. Our analyses map the allowed regions in the $(m_\beta,\ \langle m_{\beta\beta}\rangle,\ \Sigma)$ space, and quantify how the tension between cosmological bounds and laboratory limits evolves as data improve.

Direct kinematic mass
< 0.45 eV
mβ · KATRIN, 90 % C.L.
Majorana mass
≲ 28–122 meV
⟨mββ⟩ · KamLAND-Zen, ¹³⁶Xe
Cosmological sum
Σ mν
CMB, large-scale structure and DESI

Research theme 04

Beyond the three-neutrino paradigm

Tests of the standard 3ν framework against possible extensions.

The three-neutrino picture describes the data remarkably well, but it is not guaranteed to be complete. We test it against light sterile states, which would appear as additional mass-squared splittings and mixing angles; against non-standard neutrino interactions, which modify the matter potential and therefore the effective mixing in the Sun and in the Earth; and against tensions among datasets, which — if they persist as statistics grow — may be the first indication of new physics rather than of underestimated systematics.

Research theme 05

Modular invariance and the flavour puzzle

Following the proposal by F. Feruglio that the Yukawa couplings of leptons could be modular forms of a complex modulus $\tau$ living in the upper half-plane, modular invariance has emerged as a powerful candidate symmetry for the flavour structure of quarks and leptons.

With G.-J. Ding (USTC), E. Lisi (INFN Bari) and S. T. Petcov (SISSA/IPMU) we have carried out the first joint fit of quark and lepton observables — 22 quantities in total — within a modular flavour model based on the binary octahedral group $2O$, with just 14 real parameters. The fit reveals strong correlations among observables, notably between quark mass ratios and the leptonic CP phase $\delta_{\rm CP}$, that are invisible in separate analyses and that translate into sharp predictions for KATRIN, neutrinoless double-β decay, JUNO and DUNE.

In a complementary direction, with F. Feruglio (Padova), A. Strumia and A. Titov (Pisa), we have shown that modular invariance can also address the strong CP problem in string-inspired settings, where quarks have positive modular weights and gauge kinetic functions are non-trivial.

The upper half-plane with the shaded fundamental domain of the modular group SL(2,Z), bounded by the unit circle and the lines Re(tau) = ±1/2, with the fixed points i, omega and −omega-bar marked.
The complex modulus $\tau$ lives in the shaded fundamental domain $\mathcal{F}$ of $SL(2,\mathbb{Z})$. Special points $i$, $\omega$, $-\bar\omega$ and $i\infty$ are fixed by residual symmetries and play a distinguished role in flavour model building.

Selected recent publications

The complete list is maintained on INSPIRE-HEP.

Full publication list →
Conferences

NOW — Neutrino Oscillation Workshop

Otranto, biennial. One of the longest-running European workshops in neutrino physics, gathering theorists and experimentalists for in-depth discussions on the frontiers of the field. I am among the organizers.

Workshop series →
Opportunities

For prospective students and postdocs

I welcome motivated students and young researchers interested in neutrino phenomenology, statistical analysis of particle physics data, and the interplay between particle physics and cosmology.

Teaching and theses → Write to me →

A historical note

Pauli’s letter, 1930

The story of neutrinos began with one of the most famous letters in twentieth-century physics. On 4 December 1930 Wolfgang Pauli postulated a new neutral particle of tiny mass to rescue energy conservation in β-decay — a hypothesis he himself called “a desperate remedy”.

Dear Radioactive Ladies and Gentlemen, as the bearer of these lines will explain to you in more detail, because of the “wrong” statistics of the N and Li⁶ nuclei and the continuous beta spectrum, I have hit upon a desperate remedy to save the “exchange theorem” of statistics and the law of conservation of energy. Namely, the possibility that there could exist in the nuclei electrically neutral particles, that I wish to call neutrons, which have spin ½ and obey the exclusion principle and which further differ from light quanta in that they do not travel with the velocity of light. […]

But only the one who dare can win, and the difficult situation, due to the continuous structure of the beta spectrum, is lighted by a remark of my honoured predecessor, Mr Debye, who told me recently in Bruxelles: “Oh, it is best not to think about this at all, like new taxes”. […]

Unfortunately, I cannot appear in Tübingen personally since I am indispensable here in Zurich because of a ball on the night of 6/7 December. With my best regards to you, and also to Mr Back.

Your humble servant, W. Pauli.

Facsimile of the typewritten German original of Pauli's 1930 open letter to the Tübingen conference.
Facsimile of the German original, addressed to the group of radioactives at the Tübingen meeting.
Historical photograph of Wolfgang Pauli, Werner Heisenberg and Enrico Fermi together.
Pauli, Heisenberg and Fermi.