The $\tau$ Magnetic Dipole Moment at Future Lepton Colliders

Jessica Howard,Arvind Rajaraman,Tim Tait,Rebecca Riley

doi:10.31526/lhep.2.2019.113

Jessica Howard, Arvind Rajaraman + Show 2 more

Open Access

https://doi.org/10.31526/lhep.2.2019.113

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Abstract

Author(s): Howard, Jessica N; Rajaraman, Arvind; Riley, Rebecca; Tait, Tim MP | Abstract: The magnetic moment of the $\tau$ lepton is an interesting quantity that is potentially sensitive to physics beyond the Standard Model. Electroweak gauge invariance implies that a heavy new physics contribution to it takes the form of an operator which involves the Higgs boson, implying that rare Higgs decays are able to probe the same physics as $a_\tau$. We examine the prospects for rare Higgs decays at future high energy lepton (electron or muon) colliders, and find that such a project collecting a few ab$^{-1}$ would be able to advance our understanding of this physics by roughly a factor of 10 compared to the expected reach of the high luminosity LHC.

Highlights

Anomalous magnetic moments of charged fermions occupy a special role in our understanding of the Standard Model (SM)of particle physics
Guided by the expectation that new physics may be more evident for the tau, we focus on the operator described in Equation (3)
And 5, we show the results for e+e− and μ+μ− colliders, respectively. These results indicate that an O(10 TeV) lepton collider would provide a very effective probe of new physics relevant for the tau magnetic dipole moment

Summary

INTRODUCTION

Anomalous magnetic moments of charged fermions occupy a special role in our understanding of the Standard Model (SM). Promoting the tau magnetic moment operator into an SU(2) × U(1) invariant form leads to a pair of dimension six terms, c1 τRσμν Bμν H† L3 + c2 τRσμν H†Wμν L3 + h.c. where L3 is the left-handed SU(2) lepton doublet containing τL, H is the Higgs doublet, Bμν and Wμν are the field strengths for the hypercharge and SU(2) gauge bosons, and c1 and c2 are (generically complex) coefficients with units of (energy)−2 which encapsulate the residual effects of heavy physics at low. Replacing the Higgs with its VEV generates the magnetic dipole moment (and generically modify Z boson couplings and, if c1 and c2 are complex, contributes to the electric dipole) Such interactions necessarily imply a modification of the coupling of the Higgs to τ+τ−γ as well,.

FUTURE LEPTON COLLIDERS

Analysis

TeV 5 TeV 10 TeV

CONCLUSIONS AND OUTLOOK