The ratio 𝑅(𝐸) of the cross-sections for 𝑒+𝑒−→ hadrons and 𝑒+𝑒−→𝜇+𝜇− is a valuable energy-dependent probe of the hadronic sector of the Standard Model. Moreover, the experimental measurements of 𝑅(𝐸) are the inputs of the dispersive calculations of the leading hadronic vacuum polarization contribution to the muon 𝑔−2 and these are in significant tension with direct lattice calculations and...
A search for the electroweak production of pairs of charged sleptons decaying into two-lepton final states with missing transverse momentum is presented. A simplified model of 𝑅-parity-conserving supersymmetry is considered: direct pair-production of sleptons (ℓ̃ℓ̃), with each decaying into a charged lepton and a 𝜒̃01 neutralino. The lightest neutralino (𝜒̃01) is assumed to be the lightest...
The error budget of the theory calculation of the muon 𝑔−2 is dominated by two hadronic contributions: the Hadronic Vacuum Polarization (HVP) and the Hadronic Light-by-Light (HLbL) scattering. Reducing the error on these contributions is essential to match the future experimental precision.
In this talk, we present a lattice calculation of the three light pseudoscalar meson ($\pi_0$, $\eta$...
By replacing continuous space–time with a Euclidean lattice, lattice gauge theories provide a way to capture the non-perturbative effects in the muon g-2. We present first results by the RC collaborations towards obtaining a precise estimate of these effects using a novel local description of lattice QCD and QED, based on C boundary conditions in space.
The Standard Model theoretical prediction of the muon anomalous magnetic moment, $𝑎_𝜇=(𝑔−2)_𝜇/2$, presents a discrepancy of $4.2~\sigma$ with respect to the combined Fermilab and BNL measurements.
The MUonE project is a recently proposed experiment at CERN that will help to shed light on this situation, by providing an independent determination of the leading order hadronic vacuum...
The Muon $g-2$ experiment measures the muon magnetic moment anomaly $a_\mu$ by relating the precession frequencies of muons inside a magnetic storage ring to the strength of the magnetic field that they experience. A series of NMR instruments map the primary magnetic field, but some short-lived transient magnetic fields require alternative approaches to measure with sufficient precision. The...
We show that the models that induce neutrino magnetic moments while maintaining their small masses naturally also predict observable shifts in the muon anomalous magnetic moment. This shift is of the right magnitude to be consistent with the Brookhaven measurement as well as the recent Fermilab measurement of the muon g−2. This points out the direct correlation between the magnetic moment of...
The LHCb collaboration has recently set a first limit on the radiative leptonic decay of the $B_s$-meson in the region of high momentum transfer, namely $\mathcal{B} (B_s^0 \to \mu^+ \mu^- \gamma) [q^2 > (4.9 \, \rm {GeV})^2] < 2.0 \times 10^{-9}$. From the theoretical point of view, several computations of the hadronic Form Factors (FFs) entering in this decay are available in the context of...
Several results in high energy physics experiments highlighted hints of new physics in semileptonic decays of B particles. Among the existing experiments, the LHCb detector plays a very important role in this sector. In fact, it is specifically designed for the study of particles containing b or c quarks. Some LHCb results suggested the violation of the lepton flavour universality stated in...
In this talk, we consider the rare decay channel $B_s\rightarrow\mu\mu\gamma$, the radiative counterpart of the very rare $B_s\rightarrow\mu\mu$ decay, from both theoretical and experimental perspectives. This decay is sensitive to possible new vector couplings in the $b\rightarrow s\mu\mu$ interaction vertex. Using different form factors parametrizations of the $B_s\rightarrow\gamma$...
Since the observation of neutrino oscillations, lepton number conservation is known to be a non-exact symmetry of the Standard Model lagrangian: yet there is still no evidence of lepton flavour violating processes involving charged leptons (cLFV), such as $𝜇→e𝛾$, $𝜇→eee$ or $𝜇𝑁→eN$: according to minimal extensions of the Standard Model including neutrino masses, these processes are too rare to...
The Large Hadron Collider at CERN is currently our only tool for direct exploration of physics at the electroweak scale and above and the high-luminosity phase is planned to last until the late 2030s. Rare flavour-changing neutral current transitions $𝑏→𝑠𝜇^+𝜇^−$ probe higher energy scales than what is directly accessible at the LHC and therefore the presence of new physics in such transitions,...
The decreasing uncertainties in theoretical predictions and experimental measurements of several hadronic observables related to weak processes, which in many cases are now smaller than O(1%), require theoretical calculations to include subleading corrections that were neglected so far. Precise determinations of leptonic and semi-leptonic decay rates, including $\text{QED}$ and strong...
We consider a model involving a “visible” QCD axion with mass in the MeV range with flavour non-universal couplings to the Standard Model (SM) first generation fermions. Such a heavy axion must evade a variety of stringent constraints which precisely fix the couplings to the SM fields: the requirement of “pion-phobia” determines the Peccei-Quinn (PQ) charges of the light quarks to be 2/3 and...
We propose a new search for Axion-Like Particles (ALPs), targeting Vector Boson Scattering (VBS) processes at the LHC. We consider nonresonant ALP-mediated VBS, where the ALP participates as an off-shell mediator. This process occurs whenever the ALP is too light to be produced resonantly, and it takes advantage of the derivative nature of ALP interactions with the electroweak Standard Model...
Axion-like particle (ALP) is one of the promising candidates of dark matter (DM). It can emerge from the dark sector with global U(1) symmetry. It is often (implicitly) assumed that the dark sector has a CP symmetry. However, since CP is violated within the SM, the dark sector with CP violation is also an interesting possibility. In this talk, we propose a new renormalizable model for ALP with...
