Confronting the vector leptoquark hypothesis with new low- and high-energy data.

In light of new data we present an updated phenomenological analysis of the simplified U 1 -leptoquark model addressing charged-current B-meson anomalies. The analysis shows a good compatibility of low-energy data (dominated by the lepton flavor universality ratios R D and R D ∗ ) with the high-energy constraints posed by p p → τ τ ¯ Drell-Yan data. We also show that present data are well compatible with a framework where the leptoquark couples with similar strength to both left- and right-handed third-generation fermions, a scenario that is well-motivated from a model building perspective. We find that the high-energy implications of this setup will be probed at the 95% confidence level in the high-luminosity phase of the LHC.

The LFU ratio R π in the Standard Model and beyond.

We discuss the possibility of performing precise tests of µ / e universality in B → π ℓ + ℓ - decays. We show that in wide regions of the dilepton invariant mass spectrum the ratio between muonic and electronic decay widths can be predicted with high accuracy, both within and beyond the Standard Model. We present numerical expressions which can be used to extract precise information on short-distance dynamics if a deviation from universality is observed in the data.

Optimized lepton universality tests in B → V ℓ ν ¯ decays.

We propose improved lepton flavor universality (LFU) ratios in semileptonic P → V ℓ ν ¯ decays, when comparing µ and τ modes, that minimize the theoretical form-factor uncertainties. These optimized ratios are obtained with simple cuts or reweighting of the dilepton mass distributions, which imply a minimum loss of signal on the rare tauonic modes while maximizing the cancellation of theoretical uncertainties among the two modes. We illustrate the usefulness of these observables in B c → J / ψ , B c → ψ ( 2 S ) , B → D ∗ and B s → D s ∗ transitions, showing that in all cases we can reach O ( 1 % ) uncertainties on the SM predictions of the improved LFU ratios employing conservative form-factor uncertainties.

Exploring the flavour structure of the high-scale MSSM.

We analyse the sensitivity of quark flavour-changing observables to the MSSM, in a regime of heavy superpartners. We analyse four distinct and motivated frameworks characterising the structure of the soft-breaking terms by means of approximate flavour symmetries. We show that a set of six low-energy observables with realistic chances of improvement in the near future, namely Δ M s , d , ϵ K , ϵ K ' / ϵ K , B ( K → π ν ν ¯ ) , and the phase of D- D ¯ mixing, could play a very important role in characterising these frameworks for superpartner masses up to O ( 100 )  TeV. We show that these observables remain very interesting even in a long-term perspective, i.e. even taking into account the direct mass reach of the most ambitious future high-energy colliders.

Probing the Charm Quark Yukawa Coupling in Higgs+Charm Production.

We propose a new method for determining the coupling of the Higgs boson to charm quarks, via Higgs production in association with a charm-tagged jet: pp→hc. As a first estimate, we find that at the LHC with 3000 fb^{-1}, it should be possible to derive a constraint of order one, relative to the standard model (SM) value of the charm Yukawa coupling. As a by-product of this analysis, we present an estimate of the exclusive pp→hD^{(*)} electroweak cross section. Within the SM, the latter turns out to be not accessible at the LHC even in the high-luminosity phase.

Top B physics at the LHC.

In top-pair events where at least one of the tops decays semileptonically, the identification of the lepton charge allows us to tag not only the top quark charge but also that of the subsequent b quark. In cases where the b also decays semileptonically, the charge of the two leptons can be used to probe CP violation in heavy flavor mixing and decays. This strategy to measure CP violation is independent of those adopted so far in experiments, and can already constrain non standard model sources of CP violation with current and near future LHC data. To demonstrate the potential of this method we construct two CP asymmetries based on same-sign and opposite-sign leptons and estimate their sensitivities. This proposal opens a new window for doing precision measurements of CP violation in b and c quark physics via high p(T) processes at ATLAS and CMS.

Shedding light on CP violation in the charm system via D→Vγ decays.

Recent evidence for direct CP violation in nonleptonic charm decays cannot be easily accommodated within the standard model. On the other hand, it fits well in new physics models generating CP violating ΔC=1 chromomagnetic dipole operators. We show that in these frameworks sizable direct CP asymmetries in radiative D→P(+)P(-)γ decays (P=π, K), with M(PP) close to the ρ or the φ peak, can be expected. Enhanced matrix elements of the electromagnetic dipole operators can partly compensate the long distance dominance in these decays, leading to CP asymmetries of the order of several percent. If observed at this level, these would provide a clean signal of physics beyond the standard model and of new dynamics associated with dipole operators. We briefly comment on related CP violating observables accessible via time dependent D(D)→P(+)P(-)γ studies and angular decay product distributions in rare semileptonic D decays.