Seminars in Particle Physics Phenomenology at the Physics Department of Torino

I will discuss the decay B to l+ l- l’ ν in QCD, taking into account the 1/m_b and leading q2 corrections as well as the corrections due to the soft and resonant contributions calculated using dispersion relations. I present how one can extend the existing results for the radiative decay B to gamma l nu to the case of non-zero (but small) q2, the invariant mass squared of the dilepton pair. This restricts us to the case l!=l' as otherwise the same sign leptons cannot be distinguished. Finally I will present the sensitivity of the results to the leading moment of the B-meson distribution amplitude and discuss the potential to extract this quantity at LHCb and the Belle II experiment.

POSTPONED

We present Qibo, a new open-source software for fast evaluation of quantum circuits and adiabatic evolution which takes full advantage of hardware accelerators. The growing interest in quantum computing and the recent developments of quantum hardware devices motivates the development of new advanced computational tools focused on performance and usage simplicity. In this work we introduce a new quantum simulation framework that enables developers to delegate all complicated aspects of hardware or platform implementation to the library so they can focus on the problem and quantum algorithms at hand. As example for HEP applications, we show how to use Qibo for the determination of parton distribution functions (PDFs) using DIS, fixed-target DY and LHC data. We conclude by providing an overview of the variational quantum circuit models included in Qibo.

Wednesday, 1oth March 2021, ore 14:30 — Zoom seminar

A major recent breakthrough in global fits of the structure of the proton has been the inclusion of a significant amount of precise LHC measurements. While this data provides important constraints, especially on the poorly-know gluon and anti-quark PDFs, it is crucial to avoid any contamination from potential beyond the Standard Model (BSM) effects that could be present in the high energy or transverse momentum tails of the fitted experimental distributions. This problem is particularly acute for LHC data from Runs II and III, as well as for the future High-Luminosity Run, where many PDF-sensitive observables will reach the few TeV region. In this talk, I present a first quantitative study aiming to study whether or not New Physics effects can be reabsorbed into the fitted PDFs, as well as the possibility of setting up a global QCD fit to simultaneously constrain the proton structure and New Physics dynamics.

Wednesday, 3rd March 2021, ore 14:30 — Zoom seminar

I present recent results for LHC cross sections computed to third order in the strong coupling constant. These first examples allow us to study the impact of such high order corrections and demonstrate their need for ultimate LHC precision phenomenology. I then discuss recent advances of how such calculations can become more tractable by performing kinematic expansions of LHC cross sections.

Wednesday, 27 January 2021, ore 11:00 — Zoom seminar

We derive the first renormalized factorization theorem for a process described at subleading power in soft-collinear effective theory. Endpoint divergences in convolution integrals, which arise generically beyond leading power, are regularized and removed by systematically rearranging the factorization formula. We study in detail the example of the $b$-quark induced $h\to\gamma\gamma$ decay of the Higgs boson, for which we derive the evolution equations for all quantities in the factorization theorem and resum large logarithms of the ratio $M_h/m_b$ at next-to-leading logarithmic order.

Wednesday, 2nd February 2021, ore 14:30 — Zoom seminar

Non-leptonic B decays are important probes in the search for new physics and specifically new sources of CP violation. These decays are, however, also challenging to calculate due to their fully hadronic initial and final states. Using the heavy-quark limit, decays of heavy B mesons can be factorized into perturbatively calculable hard-scattering kernels and non-perturbative universal hadronic quantities. This framework of QCD Factorization allows the prediction of decays rates and CP asymmetries of non-leptonic decays! In this seminar, I will discuss how to extend this framework to include QED effects. This extension leads to interesting and qualitatively new features, and in this case QED turns out to be more complicated than QCD as the final states are always color neutral but electrically charged. Finally, I will discuss the phenomenological consequences of the QED corrections, which are in general small but enhanced in specific theoretically clean ratios and isospin sumrules.

Wednesday, 27 January 2021, ore 14:30 — Zoom seminar

Over the last few years, the LHCb collaboration has been finding tensions between measurements and Standard Model predictions for several observables related to B-meson decays mediated by an underlying b→sℓ+ℓ− transition. Other experiments (Belle, ATLAS, CMS) have found consistent results, albeit with large error bars. These tensions have been identified as potential signs of New Physics and one approach to assess their significance is to perform global fits to all available b→sℓ+ℓ− data. In this seminar, I will discuss the techniques used for the computation of the relevant observables in our fits, paying special attention to the treatment of hadronic uncertainties, and present the latest results of our global analyses and some of their implications.

Wednesday 20th January 2021, ore 14:30 — Zoom seminar