Search for e+e− → µ+µ− Z'(Z' → Invisible) in the first data of the Belle II experiment

Sumitted to PubDB: 2022-09-16

Category: Master Thesis, Visibility: Public

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Authors	Luigi Corona, Francesco Forti
Date	Jan. 1, 2018
Belle II Number	BELLE2-MTHESIS-2022-018
Abstract	The purpose of this thesis is to investigate the production of a light dark gauge boson Z' in association with a muon pair in electron-positron annihilation at the center of mass energy of 10.58 GeV. Through this analysis is possible to limit the Lµ-Lτ model, which introduces the boson Z' extending the symmetry group of the SM, U(1)Y x SU(2)L x SU(3)C, with the abelian group U(1) Lµ-Lτ. This new symmetry introduces an interaction term of the Z' boson with muons and tauons and it preserves the difference between the µ leptonic number and the τ leptonic number in the processes. The Lµ-Lτ model is very well motivated theoretically and it could explain some of the observed experimental effects. The process analyzed is e+e- → µ+µ- Z', Z' → Invisible, where the muon pair is produced at the Υ(4S) energy peak and the Z' boson is radiatively emitted by one of the two muons. The signature of the process consists of two muon tracks coming from the interaction point plus missing mass. The signal yield is extracted by fitting the distribution of the recoil mass against the muon pair with respect to the center of mass momentum, which is expected to peak at the Z' mass M(Z') for signal events.
Conference	Pisa