Exploring $Z^{\prime }$ and Right-Handed Neutrinos in the BLSM at the Large Hadron Collider

Abstract

We study the collider phenomenology of the $B$-$L$ extension of the Standard Model (BLSM), focusing on the production and decay of a heavy neutral gauge boson (\( Z' \)) at the Large Hadron Collider (LHC). In this framework, the \( Z' \) can decay into pairs of heavy right-handed neutrinos (\( \nu_R \)), which subsequently decay into charged leptons and \( W \) bosons. These processes give rise to three distinctive final states: (i) two leptons plus four jets (\( 2\ell + 4j \)), (ii) four leptons plus missing transverse energy (\( 4\ell + \text{MET} \)), and (iii) three leptons plus two jets and MET (\( 3\ell + 2j + \text{MET} \)). % To enhance signal sensitivity and suppress Standard Model backgrounds, we employ multivariate analysis techniques based on Boosted Decision Trees (BDTs), as well as selection optimizations using the \texttt{XGBOOST} framework. The classifiers are trained on kinematic observables sensitive to the masses of the \( Z' \) and \( \nu_R \). We demonstrate that all three final states offer significant discovery potential for both the \( Z' \) and heavy \( \nu_R \) at the High-Luminosity LHC. Our results highlight the testability of the BLSM at current and future collider experiments, and provide a promising avenue for probing the origin of neutrino masses and the baryon asymmetry of the Universe.

Comments: 23 pages, 17 figures, 6 tables. Extended use of Machine Learning (BDT + XGBOOST) methods in this revised version