New Frontiers in Theoretical Physics - XXXVIII Convegno Nazionale di Fisica Teorica

20 May 2025, 11:10 → 23 May 2025, 15:00 Europe/Rome

Palazzone della Scuola Normale Superiore di Pisa, Cortona

We are happy to announce a new edition of the famous series of the Italian National Meetings on Theoretical Physics known as "Convegni di Fisica Teorica di Cortona”. Resting on a very long tradition, this bi-annual Conference has historically been a prestigious meeting point of the Italian community in theoretical physics. The aim of the Conference is to discuss some of the most recent and exciting advances in many areas of theoretical physics, in the pleasant Spring atmosphere of a pretty Tuscan hill. The informal environment and the intimate location will facilitate a fruitful exchange between senior and junior colleagues. Indeed, good participation of young researchers, including graduate students and postdoc fellows, alongside senior researchers, has always been the trading mark of this Conference. The program will feature plenary sessions with invited talks by Italian experts in the research areas of interest of INFN, and contributed talks by junior participants. The schedule includes free time for spontaneous discussions which the organizers strongly encourage to continue over a good Tuscan-style dinner in the beautiful center of Cortona.

Tuesday, 20 May

14:00 → 14:40 The Science of the Einstein Telescope

Speaker: Michele Maggiore (Geneva University)

14:40 → 15:05 Imperfect Axions

Speaker: Luca Di Luzio (Istituto Nazionale di Fisica Nucleare)

15:05 → 15:35 Astro/Cosmo

15:05 Nonlinearities in black hole ringdown

We study the quadratic quasi-normal modes of a Schwarzschild black hole, which are perturbations originating from the coupling of two linear quasi-normal modes. As recent studies suggest, nonlinear effects in black hole perturbation theory may be crucial for accurately describing a black hole ringdown. We present a new class of "quadratic" quasi-normal modes at second order in perturbation theory, where both the frequency and amplitude are entirely determined by the linear modes. Assuming the amplitude of the two linear modes is known, we compute the amplitude of the resulting quadratic mode across a wide range of possible angular momenta using Leaver's algorithm. Finally, we reconstruct the waveform in the radiation gauge. These quadratic modes could enhance black hole ringdown models by incorporating nonlinear features without adding extra free parameters for data analysis, or serve as a tool to test General Relativity in the nonlinear regime.

Speaker: Leonardo Juliano (Istituto Nazionale di Fisica Nucleare)

15:20 Direct current memory effects in effective-one-body waveform models

The direct current (DC) memory is a non-oscillatory, hereditary component of the gravitational wave (GW) signal that represents one of the most peculiar manifestations of the nonlinear nature of GW emission and propagation. In this work, by transforming the results provided in Ebersold et al.[Phys.Rev.D 100 (2019) 8, 084043] in harmonic coordinates and quasi-Keplerian parametrization, we provide the DC memory in terms of the effective-one-body (EOB) phase-space variables, with a relative accuracy of 2.5PN and in an expansion for small eccentricity up to order six. Our results are then implemented in TEOBResumS-Dalí, thus providing the first EOB model with DC memory contributions. This model is then used to assess the impact on the waveform and the main features of the DC memory, also addressing its dependence on the eccentricity of the binary system at its formation.

Speaker: Elisa Grilli (Istituto Nazionale di Fisica Nucleare)

15:50 → 16:20 Coffee break

16:20 → 18:05 Astro/Cosmo

16:20 A new modular mechanism for neutrino masses from low-scale seesaw

In the presence of a finite modular flavour symmetry, fermion mass hierarchies may be generated by a slight deviation of the modulus from a symmetric point. This small parameter governing charged-lepton mass hierarchies may also be responsible for the breaking of lepton number in a symmetry-protected low-scale seesaw. In this talk, I will illustrate the implementation and the phenomenological implications of this connection.

Speaker: Matteo Parriciatu (Istituto Nazionale di Fisica Nucleare)

16:35 Indirect detection probes of Minimal Dark Matter 5-plet

We critically reassess the Minimal Dark Matter model and propose new indirect detection signatures. Specifically, for the originally proposed accidentally stable SU(2) 5-plet, we compute the photon flux arising from Dark Matter Bound State Formation and Sommerfeld Enhancement, highlighting the appearance of several spectral lines. After analyzing the key features of this flux, we explore the constraints on the 5-plet imposed by FERMI-LAT observations of the galactic diffuse emission, as well as the projected sensitivity of the upcoming Cherenkov Telescope Array (CTA) in searches targeting Dwarf Spheroidal Galaxies.

Speaker: Giulio Marino (Università di Pisa)

16:50 Current constraints on cosmological scenarios with very low reheating temperatures

If reheating occurs at sufficiently low temperatures (below $20 \,\mathrm{MeV}$), neutrinos—assuming they are populated only through weak interactions—do not have enough time to reach thermal equilibrium before decoupling. We present an updated analysis of cosmological models with very low reheating scenarios, including a more precise computation of neutrino distribution functions, leveraging the latest datasets from cosmological surveys. At the $95\%$ confidence level, we establish a lower bound on the reheating temperature of $T_\mathrm{RH} > 5.96 \, \mathrm{MeV}$, representing the most stringent constraint to date.

Speaker: Nicola Barbieri (Istituto Nazionale di Fisica Nucleare)

17:05 Embedding interacting dark energy models in trace-free Einstein gravity

In trace-free Einstein gravity, the energy-momentum tensor of matter is not necessarily conserved and so the theory offers a natural framework for interacting dark energy models with a constant equation of state w=−1. From the point of view of quantum gravity phenomenology, it has been argued that such violations of energy-momentum conservation might originate from discreteness at the Planck scale. We show that within this framework it is possible to build models that are free from perturbative instabilities, which are otherwise known to affect a large class of interacting dark energy models.
We analyze in detail a simple such model where the energy-momentum transfer potential is proportional to the energy density of cold dark matter, which is also equivalent to a generalized dark matter model with a constant equation of state. Interestingly, requiring that there are no gradient instabilities implies that energy is transferred from dark matter to dark energy. We study the evolution of cosmological perturbations in this model and discuss observational constraints.

Speaker: Dr Marco De Cesare (Istituto Nazionale di Fisica Nucleare)

17:20 Strong CMB bounds on ALPS form strings

Axion-like particles (ALPS), radiated from a network of cosmic strings, may be a large part of Dark Matter (DM). In the era of precision Cosmology, it is possible to characterize the effect of such particles - which almost scale invariant distribution function spans many orders of magnitudes in momentum - on the observables. In this work, we employ the CLASS code and Planck 2018 data to place bounds on the abundance and on other distinctive parameters of ALPS from strings. We focus on the mass range 10^-20 - 10^-15 eV, and we find the strongest constraint on the ALP decay constant f_a if the ALP's mass is between (10^-20,10^-18) eV, where we are able to improve the bound on f_a from overabundance of DM by more than a factor of 3. As a result, the ALPS from strings we considered cannot make up for more than one tenth of DM at three sigma, if the ALP mass is between 10^-20-10^-18 eV.

Speaker: Riccardo Impavido (Istituto Nazionale di Fisica Nucleare)

17:35 Hunting axion dark matter with anti-ferromagnets: a case study with nickel oxide

We show that nickel oxide, which is already a very promising target to look for sub-MeV dark matter scattering, can be employed to hunt axion dark matter, with masses in the meV range and couplings to electrons allowing them to potentially be QCD axions. We describe the interactions between axions and the collective excitations of nickel oxide in terms of a universal effective field theory, built solely out of symmetry arguments. The processes of conversion into one or two excitations provide, respectively, a narrowband and a broadband channel for the axion search, and the possibility of varying an external magnetic field up to a phase transition point allows to cover a large portion of a yet unexplored parameter space, reaching axion masses down to few fractions of an meV. Our results underline nickel oxide as an ideal candidate for a multi-purpose target for light dark matter searches.

Speaker: Pier Giuseppe Catinari (Istituto Nazionale di Fisica Nucleare)

17:50 Constraining UV freeze-in of light relics with current and next-generation CMB observations

The Cosmic Microwave Background (CMB) provides a powerful tool for testing the existence of light particle species beyond the Standard Model (BSM). In particular, light relics produced via freeze-in are a common feature of models where new light degrees of freedom interact too weakly with the Standard Model (SM) plasma to achieve full thermalization in the early Universe. This talk focuses on ultraviolet (UV) freeze-in scenarios, where the new light species is produced through non-renormalizable interactions typical of BSM models. Several benchmark BSM models are explored, including axion-like particles from Primakoff production, massless dark photons, and light right-handed neutrinos. We discuss the impact on the effective number of neutrino species and demonstrate that next-generation CMB observations will be able to complement—and in some cases surpass—current astrophysical, laboratory, and collider constraints on the couplings of the SM to the light relic.

Speaker: Luca Caloni (University of Coimbra)

Wednesday, 21 May

09:00 → 09:40 TBD

Speaker: Alessandro Tomasiello (Istituto Nazionale di Fisica Nucleare)

09:40 → 10:55 Formal aspects

09:40 The moments of the spectral form factor in SYK

In chaotic quantum systems the spectral form factor exhibits a universal linear ramp and plateau structure with superimposed erratic oscillations. The mean signal and the statistics of the noise can be probed by the moments of the spectral form factor, also known as higher-point spectral form factors. We identify saddle points in the SYK model that describe the moments during the ramp region. Perturbative corrections around the saddle point indicate that SYK mimics random matrix statistics for the low order moments, while large deviations for the high order moments arise from fluctuations near the edge of the spectrum. The leading correction scales inversely with the number of random parameters in the SYK Hamiltonian and is amplified in a sparsified version of the SYK model, which we study numerically, even in regimes where a linear ramp persists. These findings reveal how deviations from random matrix universality arise in disordered systems and motivate their interpretation from a bulk gravitational perspective.

Speaker: Andrea Legramandi (Istituto Nazionale di Fisica Nucleare)

09:55 Foundational aspects of Supersymmetry via the Dressing Field Method

I will explore some foundational aspects of supersymmetric field theories under the perspective of the Dressing Field Method (DFM), a new systematic tool to exhibit the gauge-invariant content of general-relativistic gauge field theories.
First, I will show that the gauge-fixing conditions typically used to extract the degrees of freedom of the Rarita-Schwinger spinor-vector and gravitino fields are actually instances of the DFM. Since the latter has a natural relational interpretation, solving the dressing functional constraints actually realises the Rarita-Schwinger spinor-vector and gravitino fields as relational variables.
I will then discuss the unconventional supersymmetry proposal by Alvarez, Valenzuela, and Zanelli, aiming to use the framework of supersymmetric field theory to describe fermionic matter fields and bosonic gauge fields as parts of a single superconnection, showing that the so-called matter ansatz underlying the theory is a special case of the DFM.

Speaker: Lucrezia Ravera (Istituto Nazionale di Fisica Nucleare)

10:10 UV asymptotics of the generating functional of correlators of superfield twist-2 operators in $\mathcal{N}=1$ SYM theory

We provide a new construction of superfield collinear twist-$2$ operators as infinite-dimensional, irreducible representations of the collinear superconformal algebra in the zero-coupling limit of $\mathcal{N}=1$ supersymmetric Yang-Mills (SYM) theory in a manifestly gauge-invariant and supersymmetric-covariant fashion.This construction makes manifest their mixing and renormalization properties at one loop. We compute their asymptotic renormalization-group improved generating functional in Euclidean superspace and its planar and leading nonplanar large-$N$ expansion. We verify that the leading nonplanar asymptotic RG-improved generating functional matches the structure of logarithm of a functional superdeterminant of the corresponding nonperturbative object arising from the glueball/gluinoball effective action, which it should be asymptotic to at short distances because of the asymptotic freedom. Hence, our large-$N$ computation sets strong ultraviolet asymptotic constraints on the nonperturbative solution of large-$N$ $\mathcal{N} = 1$ SYM theory that may be a pivotal guide for the search of such a solution.

Speaker: Giacomo Santoni (Istituto Nazionale di Fisica Nucleare)

10:25 N=1 supergravity Lagrangian from the Double Copy

The Double Copy relations are a set of correspondences between (super) gravitational and (super) Yang-Mills theories which allow one to compute tree-level n-graviton scattering amplitudes from tree-level n-gluon ones. We try to extend this paradigm to the off-shell case by attempting the construction of the Lagrangian of N=1 Supergravity using an N=1 Yang-Mills theory and a non-supersymmetric Yang -Mills theory as building blocks. This is done by constructing Double Copy fields as suitable convolution products of the fields of the two Yang-Mills Theories. We also try to generalize the Double Copy to the case of higher-spin fields by means of the same construction.

Speaker: Valerio Descontus (Istituto Nazionale di Fisica Nucleare)

10:40 Light spin-3/2 particles need gravity (and broken SUSY)

We study the EFT of a Majorana massive spin-$\frac{3}{2}$ particle through consistency conditions derived from unitarity, causality and Lorentz invariance. We show that its mass cannot be parametrically lighter than the UV cutoff, unless all the interactions, both in the transverse and longitudinal sector, are tuned to gravity. Then we focus on the decoupling limit, which effectively projects out the longitudinal modes and gives a theory of goldstinos. We study the allowed parameter space, identifying relevant UV completions, with both finite and infinite towers of higher-spin states. The necessity of gravity for consistency and the tuning of the couplings point to theories with spontaneously broken supersymmetry as the only consistent UV completions for a parametrically light spin-$\frac{3}{2}$ particle.

Speaker: Marcello Romano (IPhT, Saclay)

10:55 → 11:25 Coffee Break

11:25 → 12:25 Formal aspects

11:25 Numerical Methods for Holography

In the last decades, the holographic principle has been a powerful ally in high-energy physics, both as a tool and as an insight.
I will present how holography can be used in the context of nonperturbative analysis of QCD-like theories, providing examples of confinement and phase structure. I will focus on instances that do not require strong analytical control and can thus be tackled numerically, showing how even for high-energy physics, numerical methods can yield fruitful results and illuminating visual insights, either via simulations or numerical solutions.

Speaker: Mauro Giliberti (Istituto Nazionale di Fisica Nucleare, Università degli Studi di Firenze)

11:40 Monopole-fermion scattering in a chiral gauge theory

The scattering of charged massless fermions on magnetic monopoles at low-energy in the s-wave presents a long-standing final state puzzle: it seems to be generally impossible to construct an outgoing state conserving all charges. Indeed, bosonizing the low-energy EFT, one is seemingly led to particles of fractional charge.

In this talk I describe this problem starting from a UV complete chiral gauge theory, and descending to the EFT. This step allows us to discuss and exclude some existing proposed solutions to the puzzle. I will argue that the correct solution is introducing a topological operator.

I will conclude by commenting on non-abelian charges and some open problems.

Speaker: Bruno Bucciotti (Scuola Normale Superiore di Pisa)

11:55 Weak rates in strongly coupled cold quark matter

The rates of flavor-changing weak processes are crucial in determining the conditions of beta equilibrium in neutron stars and mergers, influencing the damping of oscillations, the stability of rotating pulsars, and the emission of gravitational waves. We derive a formula for these rates at nonzero temperature, to leading order in the Fermi coupling and exact in the QCD coupling. Utilizing a simple phenomenological holographic model dual to QCD, we study massless unpaired quark matter at high densities. We numerically compute the rate for small deviations from beta equilibrium and derive an analytic approximation for small temperatures. Our findings reveal that, compared to the perturbative result, the rate is suppressed by logarithmic factors of the temperature.

Speaker: Andrea Olzi (Istituto Nazionale di Fisica Nucleare)

12:10 On relation perturbative QFT and the stochastic approach in cosmology

I would like to discuss recent results in well-known (and not so much) techniques to calculate correlation functions in de Sitter space and beyond. The main focus of my talk is the connection of the stochastic formalism to perturbative QFT's results in curved spacetime.

Based on arXiv: [2410.16226] and work in progress.

Speaker: Polina Petriakova (Istituto Nazionale di Fisica Nucleare)

12:25 → 12:50 TBD

Speaker: Marco Meineri (Istituto Nazionale di Fisica Nucleare)

12:50 → 14:35 Lunch

15:15 → 15:45 Applied theory

15:15 Subspace-enhanced Variational Quantum Eigensolvers via k-frame optimization

In this talk, we extend the Variational Quantum Eigensolver (VQE) approach to improve the estimate of the ground state of a quantum system by minimizing the expectation value of a target Hamiltonian on a k-frame—a set of k linearly independent orthonormal states—that define a k-dimensional subspace within the full Hilbert space. This search is then supplemented by an exact diagonalization in the optimal subspace. We find that this method significantly improves ground state estimation accuracy and optimization efficiency. We provide theoretical justification for these improvements by investigating the correlation between ground state infidelity and the loss function, as well as analyzing the expressivity of the k-frame formulation in comparison to the standard version of VQE.

Speaker: Marco Intini (Università di Pisa, INFN Pisa)

15:30 Dissipative electrically driven fluids

Hydrodynamics is the effective field theory description of many-body systems close to thermal equilibrium at large distances and late times. The dynamics of these systems are governed by the conservation of energy, momentum and charge. However, in certain cases, e.g., when spatial translation invariance is broken, these hydrodynamic currents decay slowly rather than remain conserved, necessitating a modification to the standard hydrodynamic framework, known as relaxed hydrodynamics.

In this talk, I will explore how to incorporate relaxations into the description of entropy generating flows for fluids that reach a steady state under an applied electric field. Specifically, we aimed to construct a hydrodynamic theory that aligns with Drude's model of electron transport. In the conventional hydrodynamic formulation of a charged fluid under an external electric field, the stationary state arises when the electric field is balanced by the gradient of the chemical potential. This approach treats the electric field and the fluid velocity as independent degrees of freedom, which contrasts with Drude's model.

To resolve this discrepancy, I discuss a boost-agnostic hydrodynamic model with modified hydrostatic constraints. After pointing out the relation between the energy and momentum relaxation in the presence of dissipation in our model, I will present the computed thermo-electric conductivities. We find that imposing Onsager reciprocity leads to a zero incoherent conductivity. Furthermore, the AC thermo-electric conductivities exhibit a Drude-like form. This model thus provides a refined hydrodynamic description that includes Drude’s theory within a hydrodynamic formalism.

Speaker: Mr Jonas Rongen (University of Genoa & Istituto Nazionale di Fisica Nucleare)

16:00 → 16:25 Dynamics across quantum phase transitions in Rydberg atom arrays

Speaker: Simone Notarnicola (Istituto Nazionale di Fisica Nucleare)

16:25 → 16:55 Coffee Break

17:10 → 17:55 Applied theory

17:10 Fractons from covariant higher-rank Chern-Simons and BF theories

Fracton phases of matter constitute an interesting point of contact between condensed matter and high-energy physics. The limited mobility of subdimensional quasiparticles finds applications in different areas of theoretical physics, including quantum information, quantum field theory, elasticity, hydrodynamics and gravity. In our works we adopt a field theoretical approach to investigate three dimensional (3D) actions involving a rank-2 symmetric tensor gauge field $a_{\mu\nu}(x)$ invariant under the covariant fracton symmetry. First of all we study the most general 3D action of $a_{\mu\nu}(x)$ with mass dimension one and the theory appears as a traceless non-topological higher-rank generalisation of the ordinary Chern-Simons model. Once matter is introduced, our model shows a Hall-like dipole current together with a vectorial “flux-attachment” relation for dipoles. Subsequently, we studied the 3D field theory of two tensor gauge fields with mass dimension one: $a_{\mu\nu}(x)$, transforming under the covariant fracton symmetry, and $B_{\mu\nu}(x)$, with no symmetry on its indices. The corresponding invariant action is a non-topological higher-rank BF-like model, first considered from a purely field theoretical point of view, and the propagators with their poles and the degrees of freedom are studied. Once matter is introduced, a subdimensional behaviour emerges, with both fractons and lineons. Moreover our theory can be mapped to the low-energy effective field theory describing the Rank-2 Toric Code. Finally we analyze the case in which $B_{\mu\nu}(x)$ is a symmetric tensor, where it turns out that the action can be cast into the sum of two rank-2 Chern-Simons actions, thus generalizing the ordinary abelian case.

Speaker: Daniel Sacco Shaikh (Università di Genova and INFN Genova)

17:25 Work Fluctuations for Active Particles: singularities, dynamical phase transitions and big jumps

Active Particles are physical entities able to transform energy from the environment or internal reservoirs into directed self-propelled motion. From a theoretical standpoint, in recent years this class of systems generated great interest in statistical mechanics due to the display of intriguing new properties as motility-induced phase separation [1], an inherent out of equilibrium character [2] and the occurrence of singularities in distributions of integrated observables. The latter are in turn are associated to Dynamical Phase Transitions (DPTs) [3], i.e changes in the dynamical behavior of the system in different fluctuation regimes separated by singularities. In this respect, Active Work, i.e. the work performed by the self-propulsion force, emerged as a key observable to monitor in active systems as at the same time it quantifies how efficiently energy is transformed into self propulsion [4], it is strictly related to entropy production [2] and its singular distribution signals DPTs [5].

In this talk we will present a summary of our results on this subject. After briefly reviewing the case of a single free Active Ornstein-Uhlenbeck Particle (AOUP) from [4], in which DPTs do not occur, we will consider the case of a single AOUP under the effect of a confining harmonic potential from [6]. The simple but non-trivial framework of a single particle allowed us to tackle the problem analytically for both stationary and generic uncorrelated initial states. In particular, we adopted the general Large Deviations approach we developed in [7] for quadratic functionals of Gauss-Markov chains. Our results showed that harmonic confinement can indeed induce singularities in the Active Work Rate Function, with linear tails at large positive and negative values appearing for sufficiently large self-propulsion force, harmonic confinement and/or initial values. In addition, by looking at the system trajectories, we discovered these singularities to be associated to DPTs, which in turn are originated by concentrated large values, or big jumps, in the displacement and the self-propulsion force at the initial or ending points of trajectories. In order to show that these big jumps represent a general mechanism for Brownian particles, we will show that analogous results are obtained also for the work injected by the random noise on a passive underdamped Brownian particle studied in [8]. Overall, our results provide a connection between DPTs and a condensation-like physical mechanism and clarify the relevance of boundary terms in the problem at hand.

[1] Motility-Induced Phase Separation, M. E. Cates and J. Tailleur, Annual Review of Condensed Matter Physics (6) 2015
[2] Irreversibility and Biased Ensembles in Active Matter: Insights from Stochastic Thermodynamics, E. Fodor, R. L. Jack, and M. E. Cates, Annual Review of Condensed Matter Physics (13) 2022
[3] A first-order dynamical transition in the displacement distribution of a driven run-and-tumble particle, G. Gradenigo and S. N. Majumdar, Journal of Statistical Mechanics: Theory and Experiment (5) 2019
[4] Work fluctuations in the active Ornstein–Uhlenbeck particle model, M. Semeraro, A. Suma, I. Petrelli, F. Cagnetta, and G. Gonnella, Journal of Statistical Mechanics: Theory and Experiment (12) 2021
[5] Large fluctuations and dynamic phase transition in a system of self-propelled particles, F. Cagnetta, F. Corberi, G. Gonnella, and A. Suma, Physical review letters (119) 2017
[6] Work Fluctuations for a Harmonically Confined Active Ornstein-Uhlenbeck Particle, M. Semeraro, G. Gonnella, A. Suma, and M. Zamparo, Physical Review Letters (131) 2023
[7] Large deviations for quadratic functionals of stable Gauss–Markov chains and entropy production, M. Zamparo and M. Semeraro, Journal of Mathematical Physics (64) 2023
[8] Work fluctuations for a confined Brownian particle: the role of initial conditions, G. B. Carollo, M. Semeraro, G. Gonnella and M. Zamparo, Journal of Physics A: Mathematical and Theoretical (43) 2023

Speaker: Dr Massimiliano Semeraro (Università di Bari and INFN Bari)

17:40 Topological phase transitions of Active Brownian Particles under shear

Active Brownian Particles (ABPs) are known to exhibit rich non-equilibrium behaviors.
The phase diagram shows two phase transitions: from a liquid state to a hexatic state, characterized by quasi-long-range orientational order and short-range translational order, and, at decreasing density, from a hexatic state to a solid state, where both orientational and translational order are quasi-long-range. These transitions are Kosterlitz-Thouless-like.
In this study, we want to study how this behaviour changes and whether the exponents of such transitions are still universal for a system of ABPs subjected to shear flow. By employing numerical simulations and theoretical analysis, we explore how anisotropic shear stress competes with active crystallisation, modifying the system's structural, dynamical and topological properties.
These results provide new insights into the properties of active crystalline phases, with potential implications in the design of new materials.

Speaker: Daniela Moretti (Istituto Nazionale di Fisica Nucleare)

17:55 → 18:20 Non-Conventional Computing for HEP

Speaker: Stefano Carrazza (Istituto Nazionale di Fisica Nucleare)

Thursday, 22 May

09:00 → 09:40 TBD

Speaker: Fabio Maltoni (Istituto Nazionale di Fisica Nucleare)

09:40 → 10:10 QCD/EW/BSM pheno

09:40 CALICO: parametric annihilators for loop integrals & special functions

We elaborate on the method of parametric annihilators for deriving relations among integrals. Annihilators are differential operators that annihilate multi-valued integration kernels appearing in suitable integral representations of special functions and Feynman integrals. We describe a method for computing parametric annihilators based on efficient linear solvers and show how to use them to derive relations between a wide class of special functions. These include hypergeometric functions, Feynman integrals relevant to high-energy physics and duals of Feynman integrals. We finally present the public Mathematica package CALICO for computing parametric annihilators and its usage in several examples.

Speaker: Gaia Fontana (University of Zürich)

09:55 Progress on two-loop integrals for top-pair production plus a W boson

The associated production of a top-antitop quark pair with a $W$ boson is one of the heaviest signatures probed at the LHC. The corresponding rates have been found to be consistently higher than the Standard Model predictions, calling for improved theoretical predictions.
In this talk I will discuss one of the main bottlenecks for the exact computation of the two-loop QCD amplitude, namely the Feynman integrals. I will discuss a method for evaluating the integrals by computing and solving the systems of differential equations they satisfy. I will present strategies to address the complexity of the computation, which involves complicated analytic structures, such as nested square roots and elliptic functions, and expressions with an high degree of algebraic complexity.

Speaker: Mattia Pozzoli (Università di Bologna & INFN Bologna)

10:55 → 11:25 Coffee Break

11:25 → 12:25 QCD/EW/BSM pheno

11:25 Merging NLO QED corrections at hadron colliders: Z and Z+photon production using the MiNLO′ method

In order to match the increasing precision of modern particle colliders, it is essential to have accurate theoretical predictions for the cross sections of physical processes and their associated distributions. These predictions are often obtained via Monte Carlo event generators which combine the fixed-order calculation, computed as a perturbative expansion in the coupling constants, with a parton shower and further hadronization. Using the Multi-Scale Improved NLO (MiNLO′) prescription, it is possible to resum to all orders the logarithms arising from kinematic configurations that involve different scales in such a way that the resulting distribution is NLO accurate both for fully inclusive and 1-jet predictions. The MiNLO′ method was introduced specifically for QCD radiation and it has already provided remarkable results. In this talk, I will present the abelianization of the MiNLO′ method in the context of QED radiation for the neutral current Drell-Yan. More specifically, I will discuss the behaviour of the Sudakov form factor when we switch from QCD to QED and the challenges that such Sudakov form factor poses in its actual computation.

Speaker: Filippo Belloni (Istituto Nazionale di Fisica Nucleare)

11:40 On the Atomki nuclear anomaly after the MEG-II result

Recent experimental results from the Atomki collaboration have reported the observation of anomalous effects in Beryllium, Helium and Carbon nuclear transitions that could hint at physics beyond the Standard Model. However, the MEG-II experiment has recently found no significant anomalous signal in the Beryllium transition $^8$Be$^⋆$ → $^8$Be + $e^+e^-$. In view of this result, we critically re-examine the possible theoretical interpretations of the anomalies observed by the Atomki experiment in terms of a new boson X with mass around 17 MeV. The present work aims to study the phenomenology of a spin-2 state and revisit the possibility of a pure CP-even scalar, which was initially dismissed due to its inability to explain the Beryllium anomalous signal. Our analysis shows that a spin-2 state is highly disfavoured by the SINDRUM constraint while a scalar boson could explain the Helium and Carbon anomalies while being compatible with other experimental constraints.

Speaker: Stefano Scacco (Istituto Nazionale di Fisica Nucleare)

11:55 Rescuing bileptons from Landau pole

It is well known that the Standard Model (SM) is not a complete theory, but rather an effective one, describing particle phenomenology in some energy range. Different ways of extending the SM have been formulated, among these there is the class of the so-called 331 extensions. These depend ona free parameter $\beta$.It is well known that 331 models with $\beta =\sqrt{3}$ predict the existence of exotic doubly-charged gauge bosons, the bileptons, currently searched for at LHC. These models exhibit a Landau pole at the TeV scale which makes the model non-perturbative at this energy scale and non-predictive above.
In this study, we analyze and discuss ways to overcome these limitations by shifting the Landau pole at higher energies modifying the matter content of the theory introducing extra families and extra Higgs fields.

Speaker: Giovanna Paola Perdonà (Sapienza Università di Roma)

12:10 Accidental Composite Dark Matter and Grand Unification

We consider models in which the Standard Model is extended with dark quarks that belong to fragments of vector-like representations of the grand-unifying group SU(5), and are charged under a new confining non-Abelian interaction. We consider both strongly-coupled and weakly-coupled régimes, corresponding to the dark quarks being lighter or heavier than the confinement scale, respectively. We discuss the difference in the ordering of the spectrum of the dark baryons, the lightest of which are dark matter candidates, being accidentally stable. We focus particularly on the classification of the models and their phenomenology in the presence of a scalar dark quark that is a total singlet under the Standard Model gauge group.

Speaker: Stefano Palmisano (Istituto Nazionale di Fisica Nucleare)

12:25 → 12:50 TBD

Speaker: Dario Buttazzo (INFN Pisa)

12:50 → 14:30 Lunch

14:30 → 15:10 A new route to QCD phenomenology: hadronic spectral densities from the lattice

Speaker: Nazario Tantalo (Istituto Nazionale di Fisica Nucleare)

15:10 → 16:10 Hadron/Flavor/Lattice

15:10 Isospin Strikes Back

The decay of a charmonium vector meson $c\bar c$ into the $\Lambda\bar\Sigma^0 + \mathrm{c.c.}$ state can be considered purely electromagnetic under the assumption of isospin conservation. The first-order interaction is therefore mediated by a virtual photon, similar to the non-resonant process $e^+e^- \to \Lambda\bar\Sigma^0 + \mathrm{c.c.}$ in the Born approximation. Given the nature of these two processes, any discrepancy between their measurements can be attributed to an isospin-violating contribution in the charmonium state decay.

Thanks to its high luminosity and the large amount of collected data, the BESIII collaboration has recently reported the measurement of the decay ratio $\text{BR}(\psi(2S) \to \Lambda\bar\Sigma^0 + \mathrm{c.c.})$, which represents the first-ever measurement of this process and is currently published in the Particle Data Group.

Using this data, along with the decay ratio for the $J/\psi$ state and the cross-section values for neutral baryon-antibaryon pair production, it is possible to extract the electromagnetic coupling value from both measurements independently. In this presentation, we will discuss the BESIII result and demonstrate the procedure for quantifying the extent of potential isospin violation. We will conclude that the experimental measurement obtained by the collaboration excludes the presence of significant isospin violation phenomena in the decay $\psi(2S) \to \Lambda\bar\Sigma^0 + \mathrm{c.c.}$

Speaker: Francesco Rosini (Istituto Nazionale di Fisica Nucleare)

15:25 RG running and mixing for $\Delta F = 2$ Four-Fermion Operators in $\chi SF$ schemes

We study the renormalization and mixing of the $\Delta F=2$ Four-Fermion Operators (FFO), starting from the problem of the computation of the perturbative running for $N_\mathrm{f}=3$ and showing how this problem is solved through the use of the Poincaré-Dulac theorem. We then illustrate the procedure to evaluate the non-perturbative running from the hadronic scale ($O(\Lambda_{QCD})$) to the electroweak scale ($O(M_W)$), where we hope to safely make contact with perturbation theory. This procedure goes through the computation of the Step-Scaling Functions (SSF) in the Schrödinger Functional (SF) setup. We finally present preliminary numerical results for the non-perturbative running.

Speaker: Riccardo Marinelli (Istituto Nazionale di Fisica Nucleare)

15:40 The Cabibbo Angle from Inclusive $\tau$ Decays

The inclusive hadronic decays of the $\tau$ lepton offer an alternative method for extracting the CKM matrix elements $V_{\mathrm{ud}}$ and $V_{\mathrm{us}}$. In this talk, I will discuss recent results from the ETM Collaboration on the inclusive hadronic decay rate of the $\tau$, obtained in $N_f=2+1+1$ QCD using the novel HLT method. This approach circumvents the well-known inverse Laplace transform problem that hinders this calculation, allowing us to obtain first-principles results without relying on the operator-product expansion or perturbative QCD. Apart from isospin-breaking (IB) effects, all systematic uncertainties are under control. In the $\bar{u}s$ channel we obtain $|V_{us}|_{\tau\mathrm{-latt-incl}} = 0.2189(7)_\mathrm{th}(18)_\mathrm{exp}$, which reveals a $3\sigma$ tension with purely hadronic determinations of $|V_{us}|$. Since this tension can no longer be attributed to the OPE approximation, it prompts a closer examination of experimental uncertainties and highlights the importance of determining IB corrections from first principles. I will briefly present an update on the ongoing status of our calculation of these corrections.

Speaker: Francesco Sanfilippo (Istituto Nazionale di Fisica Nucleare)

15:55 Determination of the $\Lambda$--parameter of $\mathrm{SU}(N)$ Yang--Mills theories in the Twisted Gradient Flow scheme on the lattice

We present our preliminary determinations of the $\Lambda$--parameter of $\mathrm{SU}(N=3,5,8)$ Yang--Mills theories and of its large--$N$ limit in the Twisted Gradient Flow renormalization scheme on the lattice. First, we determine $\Lambda$ in units of a low-energy renormalization scale $\mu_{\mathrm{had}}$ using the step-scaling method. Then, to express $\Lambda$ in units of the conventional reference scale $\sqrt{8t_0}$, we determine the non-dimensional conversion factor $\mu_{\mathrm{had}}\sqrt{8t_0}$. Lattice simulations are performed with the Parallel Tempering on Boundary Conditions algorithm to deal with the well-known problem of topological freezing.

Speaker: Andrea Giorgieri (Istituto Nazionale di Fisica Nucleare)

16:25 → 16:55 Coffee Break

16:55 → 17:25 Hadron/Flavor/Lattice

16:55 Study of the scalar and pseudoscalar meson mass spectrum of QCD above the chiral transition, using an effective Lagrangian approach

The fundamental theory of strong interactions, known as Quantum ChromoDynamics (QCD), exhibits rich symmetry properties that underlie the behavior of hadronic matter. In the limit of $N_f$ light quark masses, QCD possesses an approximate chiral symmetry $U(1)_V\otimes U(1)_A\otimes SU(N_f)_V\otimes SU(N_f)_A$. The special unitary part of this symmetry group is spontaneously broken to its vectorial subgroup $SU(N_f)_V$ at low temperatures, leading to the emergence of pseudo-Goldstone bosons. At temperatures above a critical value $T_c^{(N_f)}$, however, lattice simulations show that the chiral condensate $\langle\overline{\psi}\psi\rangle$, which is the order parameter of the breaking process, vanishes and the chiral symmetry $SU(N_f)_V\otimes SU(N_f)_A$ is approximately restored. Conversely, $U(1)_A$ symmetry remains broken at every temperature because of a quantum anomaly. Whether the $U(1)_A$ symmetry is effectively restored at temperatures higher than $T_c^{(N_f)}$, as the magnitude of the anomalous term decreases, remains a subject of active research.
In this work, expanding on previous analyses [1,2], we employ the extended linear sigma ($EL_{\sigma}$) model to investigate the mass spectrum of scalar and pseudoscalar mesons in a realistic $N_f=2+1$ flavor scenario (with degenerate up and down quarks and a heavier strange quark: $0

1. Enrico Meggiolaro and Alessandro Mordà. Remarks on the $U(1)$ axial symmetry and the chiral transition in QCD at finite temperature. $Phys. Rev. D$, 88(9):096010, 2013.
2. Enrico Meggiolaro. Study (using a chiral effective Lagrangian model) of the scalar and pseudoscalar meson mass spectrum of QCD at finite temperature, above ${T}_c$. arXiv:2310.10339 [hep-ph].
3. Alexei Bazavov et al. Meson screening masses in (2+1)-flavor QCD. $Phys. Rev. D$, 100(9):094510, 2019.

Speaker: Dr Giulio Cianti (Sapienza Università di Roma)

17:10 The $X(3872)$ Puzzle: Insights from Effective Field Theories

The (in)famous $X(3872)$ was the first exotic particle discovered in 2003, compatible with a tetraquark interpretation. More than twenty years have passed since then, yet its internal dynamic remain an open question. Currently, the most established models describe the $X(3872)$ either as a compact tetraquark, where quarks interact via color forces, or as a $\bar{D}^0D^{0}$ mesonic molecule, given that its mass is incredibly close to the di-meson threshold. The study of the internal dynamics of exotic particles provides a fundamental probe for understanding QCD in its confinement regime. In this talk, we will explore how the language of non-relativistic effective field theories can be applied to study the nature of the $X(3872)$, drawing inspiration from well-established approaches used to describe low-energy proton-neutron interactions. Finally, we will discuss our findings in light of the results produced by LHCb and in anticipation of upcoming analyses.

Speaker: Davide Germani (Sapienza Università di Roma e Istituto Nazionale di Fisica Nucleare)

Friday, 23 May

09:00 → 09:40 TBD

Speaker: Nicola Bartolo (Istituto Nazionale di Fisica Nucleare)

09:40 → 10:20 TBD

Speaker: Pierpaolo Mastrolia (Istituto Nazionale di Fisica Nucleare)

10:20 → 10:50 Coffee Break

10:50 → 11:30 Neutrinos and dark sectors: the quest for the origin of neutrino masses

Speaker: Silvia Pascoli (University of Bologna)

11:30 → 12:10 TBD

Speaker: Riccardo Barbieri