"Joint Rome Seminar"

Thursday 21 Dec 2017, 10:00 → 18:40 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

10:00 → 10:40 Bounding the space of S-matrices: rebooting the bootstrap

The bootstrap approach to conformal field theories (CFTs) has led to the most precision determination of the critical exponents falling in the universality class of the 3D Ising model. Furthermore this method has been successfully applied to bound the space of unitary CFTs with O(N) symmetry and superconformal and to investigate the irreversibility of RG-flows. In this talk I will review the intriguing attempt to export this success to the S-matrix bootstrap approach, abandoned after the discovery of QCD. With the help of numerical optimization techniques I will present some preliminary bounds on the space of non-perturbative S-matrices of flavored particles in 3+1 dimensions.

Speaker: Andrea Guerrieri

Slides JRS_AndreaGuerrieri.pdf

10:40 → 11:20 Vortex precession in trapped superfluids: an EFT approach

In this talk I will start by reviewing the effective string theory for vortices in superfluids. After that I will extend it and use it to explicitly compute the action for a vortex in a confined ultra cold gas, showing how the non relativistic result matches experimental observation. I will also comment on other possible applications.

Speaker: Angelo Esposito

Slides JRS_AngeloEsposito.pdf

11:20 → 11:35 Break

11:35 → 12:15 UV aspects of B-physics anomalies

In this talk I will review the status of the recent discrepancies in B-physics data, both in charged and neutral current semi-leptonic processes. After discussing what we can learn from the EFT approach, I will briefly present a UV complete and calculable gauge model able to account for them.

Speaker: Luca Di Luzio

Slides JRS_LucaDiLuzio.pdf

12:15 → 12:55 New searches beyond the Standard Model: light resonances at the LHC

Several motivated extensions of the Standard Model feature new scalar bosons below the Higgs mass. A primary example is constituted by pseudo-Goldstone bosons (often referred to as axion-like particles) from an approximate global symmetry. In this talk I will i) review the models that predict these particles to be within experimental reach, and ii) discuss some most promising ways to look for them at colliders. I will present recent advances both on i), discussing the supersymmetric R-axion, and on ii), presenting a new LHC bound on diphoton resonances down to 10 GeV of mass, and proposing new searches along these lines.

Speaker: Filippo Sala

Slides FSala_Roma3.pdf

12:55 → 14:25 Lunch

14:25 → 15:05 Unveiling strong dynamics beyond the Standard Model at future colliders

It is a very attracting possibility that the Higgs can be a composite state originating from a strong dynamics beyond the Standard Model, which triggers the electroweak symmetry breaking (EWSB). I will discuss the enlightening phenomenology connected to the topological sector of composite Higgs theories. In particular, new composite pseudoscalars can interact with the Higgs and with electroweak gauge bosons via anomalous interactions. A future 100 TeV pp collider (FCC-pp) will be able to test these anomalous interactions and thus shed light on the fundamental structure of the strong dynamics, which generates the Higgs and other composite resonances, and on the EWSB mechanism. I will discuss the topological interactions of a minimal composite Higgs model with fermionic ultraviolet completion, based on the coset SU(4)/Sp(4). I will indicate the strategy to test these interactions at the FCC-pp and the expected reach.

Speaker: Vignaroli Natascia

15:05 → 15:45 The quality of relaxation

There are two proposed mechanisms to realize the cosmological relaxation of the weak scale. In the first one, the relaxion rolls slowly down a slope until it stops on wiggles that grow proportionally to the Higgs vacuum expectation value (VEV). In the second one, the wiggles are of constant height, the relaxion rolls fast until it dissipates energy via efficient production of gauge bosons and gets stuck in the barriers to set the observed Higgs VEV. In this talk I define some criteria to assess the robustness of each mechanism.

Speaker: Ubaldi Lorenzo

15:45 → 16:00 Break

16:00 → 16:40 The Effective Field Theory approach to new physics: two explicit examples

In this talk I will briefly review the Effective Field Theory (EFT) approach to new physics and give a couple of illustrative examples. In the first part of the talk I will show how the Standard Model EFT can be extended to include new light degrees of freedom. Specifically, I will give the example of the EFT for a Two Higgs Doublet Model, with a second Higgs doublet added to the EFT as a dynamical degree of freedom. In the second part of the talk I will present an extension of the Standard Model with a doubly charged scalar motivated by neutrino physics and its corresponding low-energy EFT. As this particle allows for lepton flavour violation, the model is partially constrained by low energy flavour physics. I will review these current limits and present the discovery potential at future colliders.

Speaker: Margherita Ghezzi

Slides ghezzi_roma.pdf

16:40 → 17:20 Accidental Peccei-Quinn symmetry in a model of flavour

In Peccei-Quinn (PQ) solutions to the strong CP problem, a global U(1)_PQ symmetry is typically added by hand. However, U(1)_PQ need not be exact: it may arise from discrete symmetry, provided the PQ solution is protected to sufficient order. We present a rather complete model, based on Pati-Salam unification and A_4, wherein such discrete symmetries are the very same symmetries that govern quark and lepton flavour. The QCD axion itself resides within A_4 triplet flavons, which dictate fermion Yukawa structures; axion and flavour scales are firmly linked. Potentially viable avenues for testing the model include: (1) model fitting to quark and lepton mixing, (2) flavour-violating meson and lepton decays, (3) dark matter.

Speaker: Fred Bjorkeroth

Slides rjw_talk_fred_bjorkenroth.pdf

17:20 → 18:00 Standard Model Effective Field Theory and Charged Lepton Flavour Violation

This talk reviews recent theoretical developments in the study of charged LFV. In particular, it focuses on the progress in the effective-field theoretical interpretation of charged LFV observables. A systematic SMEFT approach is briefly presented and results relevant for upcoming experiments are reported.

Speaker: Giovanni Marco Pruna