Charm Physics

Charm

I have been actively involved in the study of mesons containing charm quarks since the beginning of my research career. My initial focus was on the search for CP violation, a fundamental asymmetry between matter and antimatter. Over time, I expanded my interests to include the quantum mechanical phenomenon of \(D^0-\bar{D}^0\) mixing and its interplay with CP violation, which together offer a unique window into potential contributions from physics beyond the Standard Model.

\(D^0\) Oscillations and CP violation with \(D^0 \to K^0_S h^+h^-\) decays

I am currently working on the measurement of mixing and CP violation parameters in the decay \(D^0 \to K^0_S h^+h^-\), where \(h\) denotes either a kaon or a pion. This decay channel is particularly compelling, as it enables the simultaneous study of both mixing and CP violation phenomena within a single mode.

I contributed to the development of the “bin-flip” analysis strategy [1], a novel method for extracting mixing and CP violation parameters through a time-dependent analysis of data binned in the Dalitz phase space. This approach has been applied to \(D^0 \to K^0_S \pi^+\pi^-\) decays collected by the LHCb experiment at CERN during Run 2 [2, 3], yielding competitive precision on the parameters of interest. We are currently extending this analysis to Run 3 data, which will allow for improved sensitivity due to the larger dataset and upgraded detector and trigger capabilities.

In parallel, I have been awarded a grant from the Italian Ministry of University and Research (MUR) under the PRIN2022 program to develop an alternative analysis strategy based on machine learning techniques and GPU-accelerated fitting. This unbinned approach aims to extract the mixing and CP violation parameters directly from the full phase-space and decay-time information, thereby avoiding the information loss inherent to binned methods. We expect this new strategy to significantly enhance the precision of the measurements and provide a flexible framework for future analyses.

In addition to the work on the decay \(D^0 \to K^0_S π^+π^-\), I am also involved in the analysis of the related channel \(D^0 \to K^0_S K^+K^-\). While structurally similar, this decay features a different final state and a distinct phase-space distribution. It is particularly compelling because it allows the study of mixing and CP violation parameters in a complementary kinematic region, notably around the \(\phi(1020) \to K^+K^-\) resonance. This region provides enhanced sensitivity to the mixing parameter \(y_{CP}\). The Run 2 analysis was paused due to challenges in modeling the detector acceptance and limitations in the available Monte Carlo simulation. However, with the introduction of the new software trigger in Run 3 at LHCb, a more accurate description of the acceptance becomes feasible. This renewed potential makes the analysis an attractive topic for Master’s and PhD thesis projects.

Search for CP violation in multibody \(D^0\) decays

Multibody hadronic decays of \(D^0\) mesons provide a promising environment for the search for CP violation, owing to their rich resonant structure and relatively high branching fractions. I have extensively studied and developed the use of triple product asymmetries as a tool to probe CP violation in such decays. In particular, my work on the decay \(D^0 \to K^+K^-\pi^+\pi^-\) has led to the most precise CP violation search in this channel to date [4].

I have also developed the most precise amplitude model of the \(D^0 \to K^+K^-\pi^+\pi^-\) decay to date [5], and carried out a detailed search for CP violation in the amplitude distributions.

Thanks to the significantly larger signal yields collected by the LHCb experiment during Run 2 and Run 3 compared to Run 1, these studies now benefit from enhanced sensitivity. Furthermore, the search for CP violation can be extended to the more abundant \(D^0 \to \pi^+\pi^-\pi^+\pi^-\) decay channel. The adoption of the new software trigger in Run 3 has also led to an improved acceptance profile, making this analysis particularly promising and well-suited for Master’s and PhD thesis projects.