Phenomenological New Physics searches in top and Z' sectors at the LHC

March 7, 2022
3:00pm to 4:00pm

IFT Seminar Room/Red Room

Theoretical Physics, general interest
Rosa María Sandá Seoane
Instituto de Física Teórica UAM-CSIC

IFT Seminar Room/Red Room


Over the last few years, the advances made in the experimental field of particle physics, associated with the achievements at the LHC, have allowed the Standard Model to be tested like never before. The predictions of this model have been measured and validated with unprecedented precision, and yet the number of unexplained phenomena and questions about its structure does not stop exhibiting it as an effective theory up to the energies explored. The search for New Physics is one of the key programs at the LHC, but in the face of results that do not give any clue about the way forward, the phenomenological proposals become more relevant. These proposals may prove fundamental in the upcoming years, not only for tracing new search paths and setting bounds to Beyond Standard Model theories through hypothetical direct particle detection experiments but also for proposing new observables for the indirect detection of New Physics that may have gone unnoticed to date.

This seminar presents a series of phenomenological studies that cover separately the two lines of detection of New Physics above-mentioned. In the framework of indirect detection, we present a study of four-top production at the LHC as possible evidence of light top-philic New Physics. Taking advantage of the opportunity given to the top quark in numerous extensions of the Standard Model as a possible mediator to unknown sectors of particles, as it is the heaviest particle ever found, we study through simplified models the impact on the production of four-tops of the presence of possible new particles of spin-0, 1 or 2, whose masses are below top-pair production threshold. We propose a series of new observables that identify and distinguish between these signatures, which should be taken into account in future strategies for measuring four-tops at the LHC. On the other hand, in the framework of direct detection experiments, we focused on Z' boson, a hypothetical mediator that appears in a large variety of New Physics models, and, taking into account the numerous Z' searches that have been carried out at the LHC, we present a software, Z'-explorer, to easily test Z' models against all the available visible data. By providing couplings and partial widths (or alternatively the production cross-section and branching ratios to each visible channel), Z'-explorer allows testing a given model, determining the most sensitive channel for the exclusion/detection of a given Z' within the New Physics parameter space, emerging as a phenomenological link between theory and experiments. Finally, and to include the phenomenology that provides the interaction with other hidden sectors, we also present a software update, Z'-explorer 2.0, which includes searches at the LHC of Z' coupling to fermionic Dark Matter. This proposal also exposes the main aspects of the phenomenology of new particles decaying into invisible species.