About the fine-tuning price of LEP

Abstract

Following Chankowski, Ellis and Pokorski we quantify the amount of fine-tuning of input parameters of the Minimal Supersymmetric Standard Model that is needed to respect the lower limits on sparticle and Higgs masses imposed by negative searches so far, direct or indirect. By including the one loop radiative corrections to the effective potential, the amount of fine-tuning is reduced with respect to the results of CEP by a factor of 2--5, strongly increasing as tanβapproaches 1. A further reduction factor may come from a more appropriate, less restrictive, definition of the fine-tuning parameter itself.

Figures (3)

• Figure 1: Scatter plot of the fine-tuning as function of $\tan\beta$. In the empty $\special{color cmyk 1. 1. 0 0}\circ\special{color cmyk 0 0 0 1.}$ (filled $\special{color cmyk 0 1. 1. 0.5}\bullet\special{color cmyk 0 0 0 1.}$) points the FT is computed as in CEP (as here). Small points have $m_h> 75 \,{\rm GeV}$, bigger points have $m_h>100\,{\rm GeV}$. The lower dotted line is explained in the text.
• Figure 2: Reduction in fine-tuning due to one-loop effects. The parameters of the tree level potential have been renormalized at $Q=175\,{\rm GeV}$.
• Figure 3: Scatter plot of the fine-tuning as function of $m_h$. In the empty $\special{color cmyk 1. 1. 0 0}\circ\special{color cmyk 0 0 0 1.}$ (filled $\special{color cmyk 0 1. 1. 0.5}\bullet\special{color cmyk 0 0 0 1.}$) points the FT is computed as in CEP (as here). Small points have $\tan\beta<4$, bigger points have $\tan\beta>4$.