# Dark Matter @ LHC 2019 (DM@LHC)

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
10m
Walker-Ames (Kane Hall 225)

### Walker-Ames

#### Kane Hall 225

Young Scientist Forum

### Speaker

Mr Zhongyi Zhang (Bonn University)

### Description

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)