Today I’m starting a two-year postdoc at Università degli Studi di Padova, in northern Italy. I will be working on axions and ALPs, but also flavour stuff. I will try to keep the blog updated.
By the way, in my Fediscience account, I’m selecting some interesting arXiv preprints every day. Check it out!
Ciao da Padova!
Happy 2023!
Wow, quite a long time since the last time writing here. I guess one of my New Year resolutions will be being more active in the blog (and also on my Mastodon, check it out!). I could start with some Physics - 2022 ended with quite a bang - but as it is still holidays, today’s post will be about operating systems.
This week, from 11 July to 15 July 2022, I have been attending the WE-Heraeus Summer School SMEFT’22 in Universität Siegen (Germany).
Our article Using Machine Learning techniques in phenomenological studies in flavour physics, in collaboration with Jaume Guasch (U. Padova) and Siannah Peñaranda (U. Zaragoza) has been accepted at the Journal of High Energy Physics.
NEW! Published in JHEP on 2022-07-20.
Our article Leptonic meson decays into invisible ALP, in collaboration with Alfredo Guerrera (U. Padova), Siannah Peñaranda (U. Zaragoza) and Stefano Rigolin (U. Padova) has been published at Nuclear Physics B 979 (2022) 115791.
This month I have two scheduled talks,
In the recent years, a series of measurements in the observables \(R_{K^{(*)}}\) and \(R_{D^{(*)}}\) concerning the semileptonic decays of the (B) mesons have shown hints of violations of Lepton Flavour Universality (LFU). An updated model-independent analysis of New Physics violating LFU, by using the Standard Model Effective Field Theory (SMEFT) Lagrangian with semileptonic dimension six operators at \(\Lambda = 1\,\mathrm{TeV}\) is presented. We perform a global fit, in order to assess the impact of the New Physics in a broad range of observables including \(B\)-physics, electroweak precision test, Higgs physics and nuclear \(\beta\) decays. We discuss the relevance of the mixing in the first generation for the observables with heavier lepton flavours. We use for the first time in this context a Montecarlo analysis of the likelihood function to extract the confidence intervals and correlations between observables. Our results show that a suitable strategy is to use a Gradient Boosting predictor as a proxy of the real likelihood function, and to analyze the SHAP values as a measure of the impact of each parameter of SMEFT Lagrangian in the fit.
The slides will be available at my repo, in their corresponding branch.
I will defend my PhD Thesis
The slides will be available at my repo, in their corresponding branch.
G. Martinelli, M. Naviglio, S. Simula, L. Vittorio
Abstract: We examine the semileptonic \(B \to D^{(*)} \ell \nu_\ell\) and \(B \to \pi \ell \nu_\ell\) decays adopting the unitarity-based Dispersive Matrix (DM) method, which allows to determine the shape of the relevant hadronic form factors (FFs) in their whole kinematical range, using only lattice QCD results available at large values of the 4-momentum transfer without making any assumption on their momentum dependence. Moreover, the experimental data are not used to constrain the shape of the FFs, but only to obtain our final exclusive determination of \(\vert V_{cb} \vert\) and \(\vert V_{ub} \vert\), namely: \(\vert V_{cb} \vert \cdot 10^3 = 41.1 \pm 1.0\) and \(\vert V_{ub} \vert \cdot 10^3 = 3.88 \pm 0.32\), which are consistent with the latest inclusive determinations at the \(1 \sigma\) level or better. Our calculation of the FFs allows to obtain pure theoretical estimates of the \(\tau / \mu\) ratios of differential decay rates, \(R(D) = 0.296 \pm 0.008\) and \(R(D^*) = 0.275 \pm 0.008\), which turn out to be compatible with the experimental world averages within \(\simeq 1.4\) standard deviations.
J. M. Cabarcas, J. H. Muñoz, Néstor Quintero, Eduardo Rojas
Abstract: The triplet vector boson (TVB) is a simplified new physics model involving massive vector bosons transforming as a weak triplet vector, which it has been proposed as a combined explanation to the anomalous \(b \to s\mu^+\mu^-\) and \(b \to c \tau\bar{\nu}_\tau\) data (the so-called \(B\) meson anomalies). In this work, we carry out an updated view of the TVB model, including the Belle II perspectives. We perform a global fit to explore the allowed parameter space by the most current \(b \to s\mu^+\mu^-\) and \(b \to c \tau\bar{\nu}_\tau\) data, by considering all relevant low-energy flavor observables. Our results are confronted with the most recent LHC constraints. We also incorporate in our study the first measurement on the ratio \(R(\Lambda_c) = {\rm BR}(\Lambda_b \to \Lambda_c\tau\bar{\nu}_\tau)/{\rm BR}(\Lambda_b \to \Lambda_c\mu\bar{\nu}_\mu)\) very recently obtained by LHCb. In particular, we show that the TVB model can provide an explanation to the \(B\) meson anomalies; however, this framework is in strong tension with LHC bounds. In respect to future flavor measurements at Belle II, our results suggest that a small new physics window would be allow to solely explain the \(b \to c \tau \bar{\nu}_\tau\) data in agreement with LHC constraints. Furthermore, the implications of our phenomenological analysis of the TVB model to some known flavor parametrizations are also discussed.
Ashutosh Kumar Alok, Neetu Raj Singh Chundawat, Shireen Gangal, Dinesh Kumar
Abstract: We perform a model-independent global fit to all \(b \to s \ell \ell\) data in the light of recent measurements of the lepton flavour universality violating (LFUV) observables \(R_{K_S^0}\) and \(R_{K^{*+}}\) as well as the updated measurements of observables in \(B_s \to \phi \mu^+ \mu^-\) decay, by the LHCb collaboration. We obtain new physics (NP) solutions to the current anomalies in the data, assuming NP in the muon sector only. We find that the 1D NP scenarios \(C_9^{\rm NP} <0 \) and \(C_{9}^{\rm NP}=-C_{10}^{\rm NP}\) continue to be the most favoured ones. However, the significance of the then favoured scenario \(C_{9}^{\rm NP}=-C’_{9}\) has reduced and the updated data now marginally prefers \(C_{10}^{\rm NP}\) scenario over \(C_{9}^{\rm NP}=-C’_{9}\). The 2D scenarios \((C_9^{\rm NP}, C_{10}^{\prime} )\), \((C_9^{\rm NP}, C_{9}^{\prime} )\) and \((C_9^{\rm NP}, C_{10}^{\rm NP} )\), continue to be favoured by the data in the listed order. We also analyse generic TeV scale \(Z’\) models which can generate the favored 1D scenarios, \(C_9^{\rm NP} \) and \(C_9^{\rm NP} = -C_{10}^{\rm NP}\) along with the 2D NP scenarios \((C_9^{\rm NP}, C_{9}^{\prime} )\) and \((C_9^{\rm NP}, C_{10}^{\rm NP} )\). Using the additional constraints from \(B_s -\bar{B_s}\) mixing and neutrino trident data, we find that all four models provide an equally good fit to the data. Further, we consider a model with a 25 MeV \(Z’\) that couples to muons and has a \(q^2\) dependent \(b - s\) coupling. We also study the implications of the current data on the LFUV observable \(R_{\phi}\), \(Q_{4,5}\) along with \(R_{K^{(*)}}\) in the high \(q^2\). We find that a precise measurements of these observables can provide a good discrimination between a few favored model-independent solutions, and have a potential to disentangle different heavy and light \(Z’\) scenarios considered in this work.
