Seminario di Fisica Teorica – Prasanna Dhani (INFN Genova)

Singular factors originating from the QCD factorisation of scattering amplitudes in soft and collinear limits play a prominent role in both organising and computing high-order perturbative contributions to hard-scattering cross sections. In this talk, I will report on recent work done in collaboration with Stefano Catani. We start from the factorisation structure of scattering amplitudes in the collinear limit, and we introduce collinear functions that have a process-independent structure. These collinear functions, which are defined at the fully-differential level, can then be integrated over the appropriate observable-dependent phase space to compute logarithmically-enhanced contributions to the corresponding observable. For transverse-momentum dependent observables, we show how the collinear functions can be defined without introducing what is known as rapidity divergences in the literature. We present the results of explicit computations of the collinear functions up to next-to-next-to-leading order.

———————————————–

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

Seminario di Fenomenologia – Dr. Raoul Röntsch (Universitá di Milano)

Drell-Yan production is one of the keystone processes at hadron colliders, relevant for a multitude of analyses from precision measurements of the Standard Model parameters to searches for New Physics. As such, it is important to obtain highly precise theoretical predictions to compare with data. I will discuss the computation of mixed QCD-EW corrections to onshell vector boson production and highlight their impact on the measurement of the mass of the W boson, where the target precision is around 0.1 permille. I will then discuss the calculation of mixed QCD-EW corrections to massless dilepton production, and present results focusing on intermediate to high invariant mass regions.

———————————————–

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

Seminario di Fisica teorica INFN/DIFI – Vincenzo Vitagliano (Universitá di Genova)

Spontaneous symmetry breaking is a transversal concept in modern physics, being pivotal for our understanding of mass generation in particle physics, topological defects formation in cosmology, and the appearance of condensed phases of matter. I will discuss some recent results about the way symmetry breaking occurs for systems embedded in a curved background, when curvature acts as an effective mass that, depending on the sign, enhances or suppresses the mechanism responsible for phase transitions. I will then move to a general discussion about the ground state of nonlinear field theories, commenting on the substantial changes in the structure of the quantum vacuum occurring even for the simplest choice of boundary conditions. Not only this leads to nontrivial modulation of the Casimir force as a function of external conditions, but it also regulates the behaviour at small vs large scales.

———————————————–

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

(Seminario di Fisica Teorica)

In this talk I consider gravitational mulipoles in 4D theories beyond pure Einstein gravity. For the Kerr black hole, the mutlipole moments are uniquely determined by the first mass and current multipoles, but this is not necessarily true beyond classical gravity, in string theory for example. We will look at the effects of higher-derivative corrections to the Kerr mutlipoles from an EFT point of view and discuss their viability as probes of corrections to the Kerr black hole. We will also discuss whether the richer structure of multipole moments in string theory, as compared to that of the Kerr black hole, can be used to pose constraints on corrections to General Relativity coming from string theory.

Per connettersi a zoom

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271

Conformal field theories have two main characteristics. First, they are important in the study of critical phenomena. Second, their rigid structure makes them suitable to test theoretical challenges and obtain general results. In this talk, I will describe some of their general features and see how physical data can be extracted using powerful theoretical tools. Specifically, I will focus on the study of the O(n) CFT in less than four dimensions, trying to systematize the study of four-point correlators. I will explain how to use the Lorentzian inversion formula to extract physical data in perturbation theory and discuss some interesting features and technical details which arise in the process.

Per connettersi a zoom

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271

Seminario di Fenomenologia

Multi-parton distributions in a proton, the nonperturbative quantities needed to make predictions for multiple scattering rates, are poorly constrained from theory and data and must be modelled. All Monte Carlo event generators that simulate multiple parton interactions (e.g. Pythia) contain such a model of multi-parton PDFs. One important theoretical constraint for the case of double parton distributions is provided by the so-called number and momentum sum rules. In this talk I will give a brief overview of existing models of multi-parton PDFs and discuss to what extent the double parton distribution functions used in the Pythia event generator obey these sum rules. Additionally I will also consider the number and momentum sum rules for the triple parton distribution functions and discuss how one can use the Pythia code to construct triple parton distribution functions which approximately satisfy these sum rules.

Per connettersi a zoom

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271

Seminario di Fenomenologia

Understanding the laws governing the dark matter dynamics in the

Universe is undoubtedly one of the pressing questions in

astro-particle physics. While investigations of elementary particles

as potential dark matter candidates have been at the heart of

investigations, an equally interesting possibility arises if dark

matter is instead a composite particle. I will take an overview of

dark matter theories arising from extensions of Standard Model with

new non-Abelian sectors. Analysis of such dark sector dynamics

benefits from connections to lattice calculations. I will sketch the

avenues of progress and highlight some of the open questions in this

direction. I will also take two example realisations of such strongly

interacting dark matter theories and exemplify associated

phenomenology.

Per connettersi a zoom:

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271

Seminario di Fisica Teorica

It has became clear that the landscape of possible effective field theories arising from string compactifications is vast. On the other hand, in the last 20 years it has been shown that it represents only a small part of the possible QFTs coupled to gravity one may imagine. The reason is, as shown by the seminal work by Vafa and Ooguri, that most QFTs when coupled to gravity develop subtle inconsistencies and for that they can’t appear as effective field theories of a consistent theory of quantum gravity. The space of such theories as been called the “swampland”, in opposition to the landscape, and the conditions they fail to satisfy “swampland conjectures”. In this talk, I will give first a review of the swampland program and the main swampland conjectures, explaining the arguments that justify them, and then show recent results obtained with Martucci and Weigand about constraints on N=1 d=4 theories coming from the existence of peculiar extended objects in their spectrum we called “EFT strings”. In particular, we will be able to derive upper bounds on the possible rank of the gauge group of the 4 dimensional theory and check the validity of this claim in a large number of explicit string theory constructions.

Per connettersi a zoom

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271

Seminario di Fenomenologia

Recently, JPAC collaboration has developed and benchmarked a systematic approach to use Deep Neural Networks as a model-independent tool to analyze and interpret experimental data and to determine the nature of an exotic hadron. Specifically, we studied the line shape of the Pc(4312) signal reported by the LHCb collaboration. This novel method presents great potential and can be applied to other near-threshold resonance candidates.

Per connettersi a zoom

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271

Seminario di Fenomenologia

Particle Flow (PFlow), the task of reconstructing final state particles from the detector readout, is at the heart of Collider physics. The task is quite challenging due to the complex nature of the detector data, which is heterogeneous (tracks, cells, cluster of energies), sparse, and usually originates from a non-uniform detector geometry. The recent advancements in the felid of Machine learning (ML) have suggested new possibilities beyond the scope of traditional parametric approaches to solving this complex task. In the talk, I will show models that use a set of detector hits as inputs and predict a set of reconstructed particles. I will also discuss a few novel approaches with graph-based architectures, and understand how we can combine ML with physical motivations to obtain State-of-the-art performance. I will also discuss how these models are well-suited to tackle generative problems.

Per connettersi a zoom:

Topic: Theory and Pheno seminars

https://infn-it.zoom.us/j/8573185271

Meeting ID: 857 318 5271