13-16 August 2019
Kane Hall 225
US/Pacific timezone

[YSF] Constraints on $U(1)_{l_\mu-l_\tau}$ from LHC Data

15 Aug 2019, 09:25
Walker-Ames (Kane Hall 225)


Kane Hall 225

Young Scientist Forum From Models to Signatures


Mr Zhongyi Zhang (Bonn University)


In this study, we apply LHC data to constrain the extension of the Standard Model by an anomaly-free $U(1)_{l_\mu-l_\tau}$ gauge group; this model contains a new gauge boson ($Z′$) and a scalar dark matter particle ($\phi_{DM}$). We recast a large number of LHC analyses from ATLAS and CMS of multi-lepton final states. We find that for 10 GeV < $m_{Z′}$ < 60 GeV the strongest constraint comes from a dedicated $Z′$ search in the $4\mu$ final state by the CMS collaboration; for larger $Z′$ masses, searches for final states with three leptons plus missing $E_T$ are more sensitive. Searches for final states with two leptons and missing $E_T$, which are sensitive to $Z′$ decays into dark matter particles, can only probe regions of parameter space that are excluded by searches in the 3 and 4 lepton channels. The combination of LHC data excludes values of $Z′$ mass and coupling constant that can explain the deficit in $g_\mu−2$ for 4 GeV < $m_{Z′}$ < 500 GeV. However, for much of this range the LHC bound is weaker than the bound that can be derived from searches for trident events in neutrino-nucleus scattering. Therefore, we are trying some optimizations for the event selection based on Machine Learning algorithms, especially XGBoost.

Primary author

Mr Zhongyi Zhang (Bonn University)

Presentation Materials