Seminario Fisica Teorica

The holographic duality provides an explicit reduction of quantum field theory (QFT) calculations in the semiclassical large-N limit to sets of “gravitational” differential equations whose analysis can reveal all details of the spectra of thermal QFT correlators. In the first part of my talk, I will discuss the state of affairs in our understanding of thermal spectra from the point of view of hydrodynamics, kinetic theory as well as perturbative QFTs and, finally, holographic QFTs. Then, I will discuss how, in spectra with analytic properties that appear in holography, a complete reconstruction of the spectrum and of the corresponding correlator is possible from only the knowledge of an infinite, discrete set of pole-skipping points (a “0/0” in the associated correlation function) traversed by a single (hydrodynamic) mode. The main step that will enable a unique reconstruction will be a series expansion of the problem in an inverse number of spacetime dimensions, expanded around infinity. Conceptually, this reduces the computation of a QFT correlator spectrum to performing a set of purely algebraic manipulations.

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Semina di Fenomenologia delle Particelle Elementari

Over a decade after the Higgs discovery, the hunt for physics beyond the Standard Model is incorporating more and more searches for small, non-resonant traces of new physics, that can be described by an Effective Field Theory (EFT).

The so-called Standard Model EFT (SMEFT) is now the standard framework used for these searches. The Higgs EFT (HEFT) is an alternative extension of the SM, which differs from SMEFT in the representation chosen for the scalar fields, a feature that results in a higher complexity and that, so far, has made HEFT less attractive for phenomenological studies.

Nevertheless, it is well-established that HEFT is more general than SMEFT, implying the existence of BSM scenarios which would be captured by the former but not by the latter. HEFT could also represent a useful candle to test the validity of the dimension-6 SMEFT approximation, an issue that has been raising significant concerns for LHC measurements.

After an introduction to the two frameworks, the first half of the talk will give an overview of the phenomenological characterization of HEFT and SMEFT. The second part will explore more formal aspects of the HEFT-SMEFT interplay, that build on a geometric description of the scalar sector.

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Seminario di Fenomenologia delle Particelle Elementari

The production of a top quark pair in association with a heavy boson is a class of processes of high importance at LHC, both for precision Standard Model studies and new physics searches: top-pair production in association with a Higgs boson allows for a direct measurement of the top-quark Yukawa coupling, while the cross section of top-pair production in association with a W boson has been observed consistently higher than the Standard Model value by different experimental collaborations.

In this talk we present our recent computation of the NNLO QCD corrections to both these processes, with an emphasis on their phenomenological applications.

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Physics Colloquia

I will review constraints on dark matter nature like, i.e. the dark matter free streaming, in the context of structure formation by using hydrodynamical simulations and observational data sets. In particular, I will focus on ordinary matter that does not shine in between galaxies: the intergalactic medium.

I will show that the most competitive constraints on warm dark matter (with a non-negligible free streaming) can be obtained from the main manifestation of the intergalactic medium, the so-called Lyman-alpha forest produced by neutral hydrogen in the filamentary cosmic web.

Moreover, I will show quantitative constraints on neutrino masses, comment on other dark matter scenarios (scalar dark matter, dark matter interacting with baryons or radiation) and assess the prospects of 21cm intensity mapping in addressing dark matter nature.

Seminario Fenomenologia delle Particelle

Investigating neutrino physics through observations of the Universe is crucial for addressing open questions in both cosmology and particle physics.

After reviewing current cosmological constraints on neutrino properties, I will show the potential of forthcoming large-scale structure data from the ESA Euclid mission to detect the neutrino mass sum and provide insights into the existence of light particles beyond the Standard Model.

I will also discuss how non-standard neutrino interactions, which may help to resolve the Hubble constant tension, can be constrained with future cosmological data.

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Seminario di Fenomenologia delle particelle

Abstract:

Exotic hadron spectroscopy is a hot field since it has experienced a very productive period in the past 20 years, especially in the last years, in which new discoveries and/or new evidences of exotic states are published every three-four months. The outlook for the coming decades is that it will continuously grow thanks to the increasing interest from both the theoretical and the experimental sides of the scientific community, as witnessed by the large amount of literature on this field.

In the first part of the talk, some of the main experimental findings and theoretical predictions given before the experimental discoveries, regarding fully charm tetraquarks and pentaquarks, will be presented and discussed.

In the sector of fully charm pentaquark states, I will provide an outline of both the compact pentaquark description [1] and the description based on the coupling between the meson-baryon channels and the 5-quark core channels for the nonstrange [2,3] and the strange sector [4], and I will compare the predictions of these models with the experimental data.

In the sector of fully charm and fully bottom tetraquarks, I will present the calculation of $0^++$ and $2^++$ fully heavy tetraquark decay widths and branching ratios within the vector meson dominance model in the fully bottom [5] and fully charm sector [6] and compare the results with the recent experimental data.

In the second part of the talk, I will show a new method to compute the virtual contributions in KT-factorization [7,8]. As I will explain, this new formalism is a fundamental step to bridge the gap between the lowest order calculations and the NLO corrections in hybrid kT-factorization, thus being relevant for a more precise description of the experimental data in the rich field of forward physics.

[1] E. Santopinto and A. Giachino, Phys. Rev. D 96, 014014 (2017).

[2] Y. Yamaguchi, A. Giachino, A. Hosaka, E. Santopinto, S. Takeuchi and M. Takizawa, Phys. Rev. D 96, 114031 (2017)

[3] Y. Yamaguchi, H. Garcìa-Tecocoatzi, A. Giachino, A. Hosaka, E. Santopinto, S. Takeuchi and M. Takizawa, Phys. Rev. D 101, 091502 (2020).

[4] A. Giachino, A. Hosaka, E. Santopinto, S. Takeuchi, M. Takizawa, Y. Yamaguchi, Phys. Rev. D 108, 074012 (2023).

[5] C. Becchi, A. Giachino, L. Maiani and E. Santopinto, Phys. Lett. B 806, 135495 (2020)

[6] C. Becchi, J. Ferretti, A. Giachino, L. Maiani and E. Santopinto, Phys. Lett. B 811, 135952 (2020).

[7] E. Blanco, A. Giachino, A. van Hameren, P. Kotko, Nucl. Phys. B 995 (2023).

[8] A new subtraction scheme at NLO exploiting the privilege of kT-factorization, A. Giachino, A. van Hameren and G. Ziarko, e-Print: 2312.02808, submitted to JHEP.

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Physics Colloquia

Abstract:

Climate change is one of the most challenging global issues that humankind faces. The earth average surface temperature has risen more than 1 degree since the pre-industrial time and 2023 was the warmest year since 1880, year when modern measurement records began. The basic chemistry and physics of climate change have been understood for more than a century and effects already well documented. Science and research have significantly improved our understanding of the causes and our response options: human activities are estimated to have caused the temperature increase since pre-industrial time and global warming is projected to increase if substantial and sustained actions to reduce the human impact are not taken soon. Exploring the pivotal role of science in shaping international and European climate change policy, we delve into the dynamic interplay between scientific advancements and policy decisions as the scientific community’s influence is undeniable, driving evidence-based strategies that navigate the complex challenges of climate change.

Seminario Fisica Teorica

Despite General Relativity’s experimental success, theoretical motivations suggest it may not offer the ultimate description of black hole physics. The entropy puzzle and the black hole information paradox are two challenges that any proposed theory of quantum gravity must confront. In this talk, I will introduce the “fuzzball proposal”, a conjecture arising from string theory’s construction of black holes in terms of strings and branes. According to this conjecture, strong quantum gravity effects that occur already at the horizon scale hold promise for providing a consistent microscopic description of black hole physics. I will then discuss various tools and techniques (including holography, shockwave perturbations and computational methods) which can be used to examine and corroborate this conjecture.

Galaxy redshift surveys provide a large number of observables to constrain fundamental parameters of our universe. I will provide a general introduction to the concept of spectroscopic galaxy surveys as well as an overview of Baryon Acoustic Oscillations. I will then discuss the first results of the year 1 analysis of DESI together with an outlook for the upcoming year 3 and year 5 analysis.

Physics Colloquia

Abstract: The High Luminosity LHC (HL-LHC) project at CERN has offered the opportunity to promote and develop various types of enabling accelerator technologies, such as MgB2 superconducting links for cold powering and Nb3Sn accelerators magnets for the interaction regions. The superconducting link is in an advanced prototyping phase and is expected to be fully validated in the coming months. The Nb3Sn magnet development has encountered serious difficulties characterized by performance limitation or degradation which have now been overcome. We report on the status and challenges of HL-LHC magnets and devices at CERN, with a primary focus on the root cause analysis and recovery actions implemented for the final focusing Nb3Sn quadrupole magnets, and a comparison with similar issues encountered over a decade ago on the Nb3Sn Cable-in-Conduit conductors for ITER magnets. We also present two ongoing spin-off projects which benefit from HL-LHC technology developments: a strongly curved, Nb-Ti, canted cosine theta (CCT) magnet and an energy-efficient, MgB2, superferric dipole magnet.