Calendar

Ott
4
Lun
CDS @ on-line
Ott 4@2:00 pm–3:00 pm

Consiglio di Sezione – Bilancio

Ott
6
Mer
Conformal Colliders Meet the LHC @ on-line
Ott 6@2:00 pm–3:00 pm

Seminario DIFI/INFN di Fenomenologia delle Particelle Elementari – Prof. Ian Moult (Yale University)

Collimated sprays of hadrons, called jets, are an emergent phenomenon of Quantum Chromodynamics (QCD) at high energies. Understanding the detailed energy flow, or substructure, of jets has come to play a central role at the Large Hadron Collider (LHC), where it has enabled new ways to search for physics beyond the Standard Model, as well as new insights into the strong interactions.

In this talk I will present recent developments in improving our theoretical understanding of jet substructure using insights from conformal field theory. I will show that jet substructure can be formulated as the study of matrix elements of particular lightray operators enabling the use of powerful techniques such as the operator product expansion (OPE), and providing an alternative approach to thinking about jet substructure more closely related to scaling phenomena. I will then show that the remarkable data quality of the LHC allows the scaling behavior predicted by the OPE to be directly measured in data, illustrating an interesting interplay between recent developments in CFT and LHC phenomenology.

Per partecipare: collegarsi al meeting Zoom
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271

Ott
14
Gio
Black-Hole Scattering, Eikonal Exponentiation and Gravitational Waves @ Aula 603 e online
Ott 14@11:00 am–12:00 pm

Seminario di Fisica Teorica INFN/DIFI – Carlo Heissenberg (Nordita, Stockholm, Sweden)
The eikonal exponentiation of gravity amplitudes is a non-perturbative re- summation whereby certain high-energy divergent terms, which would naively violate unitarity bounds, combine into a harmless phase factor. Eikonal tech- niques also offer a natural strategy to calculate classical gravitational observables directly from the loop-expansion of scattering amplitudes. In this talk, I will discuss how the eikonal can be applied to obtain the deflection angle for the collision of two non-spinning black holes with generic center-of-mass energies, up to order O(G3). This calculation captures both conservative and dissipa- tive radiation-reaction effects, and yields a deflection angle with a smooth behavior at high energies, where it agrees with the universal massless result. Besides explicit two-loop calculations, I will also illustrate a shortcut to access radiation-reaction effects based on analyticity, unitarity and crossing symmetry. Finally, I will sketch how the classical limit of inelastic five-point amplitudes fits in the eikonal exponentiation of elastic four-point amplitudes and provides the leading-order waveforms for the emission of gravitational waves.

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Per partecipare in presenza, prenotarsi seguendo il link
https://docs.google.com/document/d/1uaw5DHG0VykTHraDiAqYjbLFXsrOIXaftj_n04sj4PE/edit?usp=sharing
oppure per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271
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Ott
21
Gio
Non-perturbative effects and resurgence in Jackiw–Teitelboim gravity at finite cutoff @ Aula 603 e online
Ott 21@11:00 am–12:00 pm

Seminario di Fisica Teorica INFN/DIFI – Prof. Domenico Seminara (Università di Firenze e INFN)

Recently Jackiw-Teitelboim gravity has provided a 2D laboratory where to explore and investigate some ideas about quantum gravity. After reviewing some of these aspects,
I will discuss the nonperturbative structure of Jackiw-Teitelboim gravity at finite cutoff, as given by its proposed formulation in terms of a deformed Schwarzian quantum mechanics.
When expressed as a perturbative expansion in the deformation parameter, the disk partition function gives rise to an asymptotic series that admits a precise completion as prescribed
by resurgence theory. This formalism can be extended to arbitrary topologies using the basic gluing rules of the undeformed case. I will present exact results for general topologies
and show that these are captured by a suitable deformation of the Eynard-Orantin topological recursion.

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Per partecipare in presenza, prenotarsi seguendo il link
https://docs.google.com/document/d/1uaw5DHG0VykTHraDiAqYjbLFXsrOIXaftj_n04sj4PE/edit?usp=sharing
oppure per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271
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Ott
28
Gio
Axion dark matter with low-scale inflation @ Aula 603 e online
Ott 28@11:00 am–12:00 pm

Seminario di Fenomenologia delle Particelle Elementari INFN/DIFI – Dr Lorenzo Ubaldi (SISSA)

After a brief introduction to the strong CP problem, I will introduce the axion as a solution and explain how it also provides a cold dark matter candidate. In the second part of my talk I will focus on cosmological scenarios with a low scale of inflation, and discuss a mechanism that can generate enough axion relics to match the observed dark matter abundance even in such scenarios.

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Per partecipare in presenza, prenotarsi seguendo il link
https://docs.google.com/document/d/1uaw5DHG0VykTHraDiAqYjbLFXsrOIXaftj_n04sj4PE/edit?usp=sharing
oppure per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271
—————————————————————————–

Nov
4
Gio
Exact solutions to Einstein’s field equation coupled to dust @ Aula 603 e online
Nov 4@11:00 am–12:00 pm

Seminario di Fisica Teorica INFN/DIFI – Davide Astesiano (Università dell’Insubria)

To analyze the dynamics of a single spiral galaxy, we will discuss the known class of exact stationary axially-symmetric solutions to Einstein gravity coupled with neutral dust. Differently from the Newtonian description of the same system where all the quantities are completely fixed once the velocity or the matter distribution are known, the class of the relativistic solutions provides additional degrees of freedom, making the applications of this system much more interesting and wide. Up to now, from the relativistic perspective the already proposed models for galaxies are the co-rotating and the differentially rotating model. While in the first case the velocity of the dust satisfies L_u(g) = 0, in the second case it differs from zero. What is interesting about these solutions is that the low energy limits are non equivalent to the Newtonian theory. In particular, the differentially rotating case generalize the known results of Balasin and Grumiller and further highlights the discrepancy between Newtonian theory of gravity and general relativity at low velocities and energy densities. Using these exact solutions, we push forward the idea that the inertia of the gravitational field can simulate dark matter effects. In fact, we show that non co-rotance further reduces the amount of energy density required to explain the rotation curves for spiral galaxies.

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Per partecipare in presenza, prenotarsi seguendo il link
https://docs.google.com/document/d/1uaw5DHG0VykTHraDiAqYjbLFXsrOIXaftj_n04sj4PE/edit?usp=sharing
oppure per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271
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Nov
11
Gio
Recent jet measurements on ALICE @ Aula 603 e online
Nov 11@11:00 am–12:00 pm

Seminario INFN/DIFI di fenomenologia delle particelle elementari – Dr. Ezra Lesser (UC Berkeley)

In recent years, jet and jet substructure observables have been used at the LHC as instruments to search for new physics as well as to test perturbative and probe non-perturbative processes in QCD. Some observables are infrared and collinear (IRC) safe and thus easily comparable to first-principles calculations, while others offer direct insight into specific physical phenomena such as the quark-gluon plasma (QGP) formed in heavy-ion collisions. The high-precision capability of the ALICE tracking system allows a unique opportunity at LHC energies to measure tracks with low $p_text{T}$, permitting both accessibility to the softer components inside jets as well as measurement of jets with altogether lower pT. This allows ALICE a rare view into QCD and QGP dynamics at pT < 100 GeV/c. We review several recent jet measurements in ALICE using both pp and Pb-Pb collisions at 5.02 TeV and discuss the results.

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Per partecipare in presenza, prenotarsi seguendo il link
https://docs.google.com/document/d/1uaw5DHG0VykTHraDiAqYjbLFXsrOIXaftj_n04sj4PE/edit?usp=sharing
oppure per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271
—————————————————————————–

Nov
17
Mer
A Finite S-matrix @ on-line
Nov 17@2:00 pm–3:00 pm

Seminario di Fisica Teorica INFN/DIFI – Dr. Holmfridur Hannesdottir (Institute for Advanced Studies – Princeton)

The S-matrix is a fundamental object in quantum field theory, relating theoretical predictions to data from collider experiments. However, in theories with massless particles when interactions between single-particle states prevail at asymptotic times, the S-matrix is infrared (IR) divergent in perturbation theory. In this talk, we explore three solutions to the IR divergence problem: i) summing over initial and final states to obtain a finite cross section, ii) modifying the S-operator, and iii) using coherent states as scattering states. In particular, we exploit the universality of asymptotic evolution to define a modified S-operator in theories with massless particles. The resulting S-matrix can be interpreted as Wilson coefficients in Soft-collinear effective theory, as remainder functions in N=4 super Yang-Mills theory, or as coherent states. Examining its analytic structure thus provides a new probe of familiar objects from scattering calculations.

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Per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271
—————————————————————————–

Nov
25
Gio
The X17 anomaly: status and prospects @ online
Nov 25@11:00 am–12:00 pm

Seminario di Fenomenologia delle Particelle Elementari INFN/DIFI – Dr. Enrico Nardi (INFN Laboratori Nazionali di Frascati)

Certain anomalies observed in the angular correlation spectra of
electron/positron pairs produced in nuclear transitions of 8Be, 4He
and 12C can be interpreted as the emission of a bosonic particle with
a mass of 17 MeV, that promptly decays into e+e−. I review the current
status of these anomalies, and some theoretical interpretation for the
hypothetical new particle. I will also describe the prospects for
validating or disproving the X17 hypothesis by means of a particle
physics experiment.

Per partecipare su Zoom, collegarsi al meeting
Topic: Theory and Pheno seminars
https://infn-it.zoom.us/j/8573185271
Meeting ID: 857 318 5271

Nov
29
Lun
CDS @ on-line
Nov 29@2:00 pm–3:00 pm

Consiglio di Sezione