Antisymmetric rank--2 tensor unparticle physics

TL;DR

This paper explores the phenomenology of antisymmetric rank-2 tensor unparticles, analyzing their effects on Z boson decays, electroweak precision tests, and muon magnetic moments, revealing stringent constraints on model parameters.

Contribution

It introduces the phenomenological implications of antisymmetric rank-2 tensor unparticles and derives constraints from various experimental observables, highlighting the impact of scale invariance breaking.

Findings

Z boson invisible decay constrains the ratio mbda_U / M_U to be less than 0.1

S parameter and muon g-2 diverge for certain scaling dimensions when scale invariance is unbroken

Collider experiments impose more stringent constraints when scale invariance breaking parameter  is non-zero

Abstract

We present the phenomenology of antisymmetric rank-2 tensor unparticle operator ${\cal O}_{\cal U,A}^{\mu\nu}$ with scaling dimension $d_{\cal U}$. We consider the physical effects of operator $O_{\cal U,A}^{\mu\nu}$ in $Z^0$ boson invisible decays $Z^0 \to {\cal U}$, $Z^0 \to b \bar{b}$ channel, the electroweak precision observable $S$ parameter, and the muon anomalous magnetic dipole moment. The $Z^0$ boson invisible decay gives a very stringent constraint in the $(\Lambda_{\cal U}, M_{\cal U})$ plane, and only small $r \equiv \Lambda_{\cal U} / M_{\cal U} \lesssim 0.1$ is favored, when $\Lambda_{\cal U}$ is order of several 100 GeV. When the phenomenological parameter $\mu$, which parameterizes the scale invariance breaking, goes to 0, the $S$ parameter and the muon $(g-2)$ diverge for $1 < d_{\cal U} < 2$, while for non-zero $\mu$, there will be constraints on $(\Lambda_{\cal U}, M_{\cal U})$ which are more stringent than those obtained from collider experiments.