Abstract
There are discrepancies between the experimental results and the Standard Model predictions, in the lepton flavor universality of the semileptonic $B$ decays: $B \to D^{(*)} \ell \nu$. As the new physics interpretations, new charged vector and charged scalar fields, that dominantly couple to the second and third generations, have been widely discussed. In this paper, we study the signals of the new particles at the LHC, and test the interpretations via the direct search for the new resonances. In particular, we see that the $\tau \nu$ resonance search at the LHC has already covered most of the parameter regions favored by the Belle and BaBar experiments. We find that the bound is already stronger than the one from the $B_c$ decay depending on the mass of charged scalar.
Highlights
In 2012, the BABAR collaboration has reported that there are large discrepancies in the lepton flavor universalities (LFUs) of the semileptonic B decays: B → Dlν and B → DÃlν (l 1⁄4 e, μ, τ)
The Belle collaboration has reported the excesses in RðDðÃÞÞ [11,12,13], the discrepancies are milder than the BABAR results
We can discuss a gauged flavor symmetry or we can expect that some heavy fermions effectively induce the flavorful couplings according to the mass mixing with the Standard Model (SM) fermions. We focus on those two new physics interpretations and discuss the consistency with the direct
Summary
In 2012, the BABAR collaboration has reported that there are large discrepancies in the lepton flavor universalities (LFUs) of the semileptonic B decays: B → Dlν and B → DÃlν (l 1⁄4 e, μ, τ). The observables to measure the LFUs are defined as RðDðÃÞÞ 1⁄4 BrðB → DðÃÞτνÞ=BrðB → DðÃÞlνÞðl 1⁄4 e;μÞ; ð1Þ and the experimental results are RðDÞ 1⁄4 0.440 Æ 0.072 and RðDÃÞ 1⁄4 0.332 Æ 0.030 [1,2] They largely deviate from the Standard Model (SM) predictions: RðDÞSM 1⁄4 0.299 Æ 0.003 and RðDÃÞSM 1⁄4 0.258 Æ 0.005 [3].1. One simple way to violate the LFU in the B decay is to introduce a field that couples to a τ lepton. The exchange of a charged scalar at the tree level induces the violation of the LFU This simple scenario has been proposed just after the announcement of the BABAR result, and the way to prove the new physics directly/indirectly has been widely discussed.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
