Universal Extra Dimensions and the Higgs Boson Mass

Abstract

We study the combined constraints on the compactification scale 1/R and the Higgs mass m_H in the standard model with one or two universal extra dimensions. Focusing on precision measurements and employing the Peskin-Takeuchi S and T parameters, we analyze the allowed region in the (m_H, 1/R) parameter space consistent with current experiments. For this purpose, we calculate complete one-loop KK mode contributions to S, T, and U, and also estimate the contributions from physics above the cutoff of the higher-dimensional standard model. A compactification scale 1/R as low as 250 GeV and significantly extended regions of m_H are found to be consistent with current precision data.

Figures (4)

• Figure 1: Contributions to $S$ and $T$ from the standard model(the zero modes) and $j$'th KK levels of one UED compactified on $S^1/Z_2$. Here, $1/R=400 \,{\rm GeV}\,,\,m_{H}^{\rm ref}=115\,{\rm GeV}$ and $m_t=174\,{\rm GeV}$.
• Figure 2: Some contours of total $S,T$ from the standard model and its higher KK modes in the 5D UED model on $S^1/Z_2$. Here $m_{H}^{\rm ref}=115\,{\rm GeV}\,,\,m_t=174\,{\rm GeV}$. Up to 11 KK levels are included. The vertical line is the direct search limit $m_H \ge 114\,{\rm GeV}$ (95%C.L.) Heister:2001kr.
• Figure 3: The 90% C.L. allowed region in the 5D UED model on $S^1/Z_2$. Up to 11 KK levels are included. Also shown is the direct search limit $m_H \ge 114\,{\rm GeV}$.
• Figure 4: The 90% C.L. allowed regions for several values of $c_1$ and $c_2$ in the 6D UED model on $T^2/Z_2$. Also shown is the direct search limit $m_H \ge 114\,{\rm GeV}$.