Seminario di Fenomenologia –

General-purpose Monte Carlo event generators are omnipresent in collider physics. As an introduction, I will discuss the various building blocks entering such tools. The talk will focus on the core part, the so-called parton-shower algorithm. I will what it is meant to achieve, i.e. connections with all-order calculations in perturbative QCD, and how it does it in practice, i.e. (usually) as a dipole shower. The main part of the talk will, describe the effort of the PanScales collaboration in order to improve the current state-of-the-art.

Per connettersi a zoom:

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fenomenologia –

Although not being a dedicated heavy-flavour physics experiment at LHC, ATLAS experiment has a wide programme in that field and produces very competitive results. B-physics studies in ATLAS are mainly based on (multi-)muon signatures and benefit from large available statistics of pp collisions, perfect muon system and optimized triggers for B-physics.

An overview ATLAS B-physics opportunities is given, focusing on the triggers and updates made for LHC Run-3.

Selected recent results are discussed then, including onia production measurements and studies of B_c meson which aim at probing the QCD predictions, exotic hadron spectroscopy, and CP violation measurements in B decays, sensitive to possible BSM physics contributions.

Finally, future prospects are outlined for possible B-physics studies with Run-2 and Run-3 data.

Per connettersi a zoom:

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fenomenologia –

I shall review novel approaches that I have explored over the years to extract information optimally from varied observations across the electromagnetic spectrum. The aims are varied as well, and in particular I shall discuss: optimising parameter constraints for the concordance cosmological model; testing the inflationary principle through measuring its non-Gaussian imprint on the cosmic large-scale structure; confirming the validity of general relativity on the largest cosmic scales; probing the particle nature of dark matter; and learning about the origin and composition of ultra-high energy cosmic rays.

Per connettersi a zoom:

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fenomenologia –

The role of precise nuclear physics theories and models is increasing in neutrino physics. This has been recognized in low-energy neutrino experiments for many years, but recent progress of accelerator-based neutrino oscillation experiments emphasizes the importance of nuclear physics, or many-body nuclear problems. Modern neutrino oscillation experiments, such as T2K and NOvA, require us to simulate nucleon correlations, and this trend will continue with future experiments, including DUNE and Hyper-Kamiokande. Surprisingly, the need of such nuclear theory is everywhere in high-energy particle physics, and new calculations reveal previously ignored connections between nuclear physics and particle physics.

In this talk, I outline the status of neutrino interaction physics, focusing on the 1 to 10 GeV region which is critical to neutrino oscillation experiments. Special attention is paid to the recent developments in nuclear models which made contributions to neutrino physics.

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 will show that the main properties of the fracton quasiparticles can be derived from a generalized covariant Maxwell-like action. Starting from a rank-2 symmetric tensor field, a partially symmetric rank-3 tensor field strength can be built, which obeys a kind of Bianchi identity. The most general action invariant under the covariant “fracton” transformation consists of two independent terms: one describing Linearized Gravity (LG) and the other referable to fractons, a proof of the always suspected relation between fractons and gravitons. I will also discuss that, as claimed in the Literature, the fracton part can be reconduced to a generalized Maxwell theory. In particular, in the covariant generalization of the fracton theory, the equations describing the fracton limited mobility, i.e. the charge and dipole conservation, are not external constraints, but rather consequences of the field equations of motion, hence of the invariant action and, ultimately, of the fracton covariant symmetry.

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fenomenologia –

Improved understanding of quantum chromodynamics (QCD) is crucial for advanced precision in LHC data analysis: nearly all LHC collisions used in physics analysis contain jets of hadronic radiation produced by QCD. Jets are reconstructed using signals from the ATLAS inner tracking detector and calorimeters, and calibrated using in situ techniques. Differential cross-section measurements of jets and jet substructure are multi-faceted physics analyses that enable the testing of new theoretical predictions including resummed analytical predictions and higher-accuracy parton shower Monte Carlos. In this seminar, I will review the prospects for extractions of Standard Model parameters from jet substructure, and I will present new measurements of novel event shape observables performed by ATLAS that are constructed using interdisciplinary data-science techniques.

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fisica Teorica INFN/DIFI

We study holographic correlators in 2d with states whose dimensions scale with the central charge. In the 3d bulk, these heavy states create smooth horizonless solutions of supergravity that reduce to black holes in a certain limit. By solving for quadratic perturbations around these backgrounds we compute heavy-heavy-light-light four point functions at strong coupling, and study their behavior as the geometry approaches that of a black hole. We show that in this limit the spectrum of the theory becomes effectively continuous, and the correlator in momentum space develops a branch cut. The discontinuity along the cut has poles at the quasinormal frequencies of the black hole, similarly to what happens for resonances in quantum mechanics.

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fisica Teorica INFN/DIFI

There is an ongoing discussion regarding the presence of a parity-odd term in the trace anomaly of a quantum field theory consisting of a free Weyl fermion in curved spacetime. The term in question is proportional to the Pontryagin density, times an imaginary factor of dangerous astrophysical implications. In this talk, I will begin by recalling some generalities of (trace) anomalies. Afterwards, I will slowly get into the details, exposing the particularities that arise in the case of Weyl fermions. I will state the arguments provided by those who claim that the odd term does exist, as well as the replies by those of us who asseverate the opposite.

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271

Seminario di Fisica Teorica INFN/DIFI

I will discuss some of the recent progress made in the computation of holographic correlators describing the scattering of gluons in anti de Sitter space. I will focus in particular on a special AdS_5 model, arising from N D3 branes probing a D7 brane singularity, which is the holographic description of a certain 4d N=2 USp(2N) gauge theory with matter. The (mass-deformed) partition function of such gauge theory gives a non-perturbative integral constraint that the holographic correlators must satisfy, thus allowing to fix a number of coefficients that cannot be obtained from bootstrap considerations alone. Among our results: we obtain a finite coupling expression for the first higher-derivative corrections in terms of modular functions, we derive the first three orders in the small alpha’ expansion of the Veneziano amplitude in AdS_5xS^3 and we completely fix a one-loop ambiguity in the gluon amplitude without a reference to the effective action on the D7 branes, which is not known.

Seminario di Fenomenologia-

The Standard Model (SM) is an Effective Field Theory (EFT) with an electroweak hierarchy problem associated to an unnaturally light Higgs. After introducing the concept of the SM EFT and the naturalness problem, I will present the possibility that an unnatural hierarchy between certain higher-dimensional operator coefficients in a low-energy EFT would automatically imply that the Higgs’ vacuum expectation value is hierarchically smaller than the EFT cut-off, assuming the EFT emerged from a unitary, causal and local UV completion. Future colliders may have the sensitivity to infer such a pattern of coefficients for a little hierarchy with an EFT cut-off up to O(10) TeV.

Topic: Theory and Pheno seminars

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

Meeting ID: 857 318 5271