Exploring new possibilities to discover a light pseudo-scalar at LHCb

We study the possibility of observing a light pseudo-scalar a at LHCb. We target the mass region $$2.5\,\mathrm{GeV}\lesssim m_a\lesssim 60\,\mathrm{GeV}$$ 2.5 GeV ≲ m a ≲ 60 GeV and various decay channels, some of which have never been considered before: muon pairs, tau pairs, D meson pairs, and di-photon. We interpret the results in the context of models of 4D Composite Higgs and Partial Compositeness in particular.

Unified framework for B-anomalies, muon g − 2 and neutrino masses

We present a model of radiative neutrino masses which also resolves anomalies reported in B-meson decays, $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ and $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ , as well as in muon g − 2 measurement, ∆aμ. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars R2 and S3. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ , $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ and ∆aμ within 1 σ. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the S3 LQ, which enhances its reach to 1.1 (6.2) TeV at $$ \sqrt{s} $$ s = 14 TeV high-luminosity LHC ($$ \sqrt{s} $$ s = 100 TeV FCC-hh). We also present flavor-dependent upper limits on the Yukawa couplings of the LQs to the first two family fermions, arising from non-resonant dilepton (pp → ℓ+ℓ−) processes mediated by t-channel LQ exchange, which for 1 TeV LQ mass, are found to be in the range (0.15 − 0.36). These limits preclude any explanation of $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ through LQ-mediated B-meson decays involving νe or νμ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to ∆aμ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2–6)% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.

Search for the Higgs Boson decaying into tau pairs

A search for the Standard Model Higgs Boson decaying into τ pairs is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. An excess of events is observed over a broad range of Higgs mass hypotheses, with a maximum local significance of 2.93 standard deviations at mH = 120 GeV. The excess is compatible with the presence of a standard-model Higgs boson of mass 125 GeV/c2.