Journal Club

Seminar Room

Tuesday 22nd of March, 2022

Hour: 10:00

Title: Search for pair-produced vector-like leptons in  3b + N τ final states

Presented by: Javier Fuentes Martín

Ref: https://cds.cern.ch/record/2803736

Abstract:

A search for vector-like leptons (VLLs) is presented in the context of the 4321 model, a UV-complete model with the potential to explain existing B-physics measurements that are in tension with standard model predictions. The analyzed data correspond to an integrated luminosity of 97 fb, and were recorded by the CMS detector at the LHC in proton-proton collisions at √s=13 TeV at the LHC. Final states with 3 b jets and two third-generation leptons (ττ,τντ, or ντντ) are targeted. Expected upper limits are derived on the VLL production cross section in the VLL mass range 500-1050 GeV, assuming only electroweak production. At the low end of this mass range, the expected limits are below the expected production cross section, whereas at the high end of the mass range the expected upper limits on the production cross section are several times higher than the expected cross section for electroweak production. A mild excess, consistent with a possible signal, is observed in the data, such that the observed upper limits are approximately double the expected limits. The maximum likelihood fit prefers the presence of signal at the level of 2.8σ, for a representative VLL mass point of 600 GeV

Hour: 10:00

Title: The hidden side of scalar-triplet models with spontaneous CP violation

Presented by: Mikael Chala

Ref: https://arxiv.org/abs/2109.13179v2

Abstract:

Scalar triplet extensions of the Standard Model provide an interesting playground for the explanation of neutrino mass suppression through the type-II seesaw mechanism. Propelled by the possible connections with leptonic CP violation, we explore under which conditions spontaneous CP violation can arise in models with extra scalar triplets. The minimal model satisfying such conditions requires adding two such triplets to the SM field content. For this model, the scalar mass spectrum in both the CP-conserving and spontaneous CP-violating scenarios is studied. In the former case, a decoupling limit for the new scalars can be achieved, while this is not the case when CP is spontaneously broken. In particular, we show that the existence of two light neutral scalars with masses below a few tenths of GeVs is unavoidable in the CP-violating case. Using matrix theory theorems, we derive upper bounds for the masses of those light scalars and briefly examine whether they can still be experimentally viable. Other interesting features of the scalar mass spectrum are discussed as, e.g., the existence of relations among the charged and neutral scalar masses.