Suggestions for Improved Benchmark Scenarios for Higgs-Boson Searches at LEP2

TL;DR

This paper addresses how to optimize LEP2 Higgs searches within the MSSM by proposing three improved benchmark scenarios that fix key SUSY parameters to maximize or illuminate the lightest Higgs mass $m_h$. It introduces the $m_h^{\rm max}$ scenario (maximizes $m_h$ for fixed $m_t$ and $M_{\mathrm{SUSY}}$ with enhanced chargino/neutralino effects), the no-mixing scenario (vanishing stop mixing to isolate its impact), and a large $|\mu|$ scenario (smaller $m_h$ but potential full $m_h$–$\tan\beta$ coverage; with possible suppression of $BR(h\to b\bar{\!b})$ in some regions). Using both RG-improved and full FD two-loop calculations, the work analyzes how these benchmarks affect Higgs masses, production channels ($e^+e^-\to hZ$, $hA$), and decays, guiding conservative LEP2 constraints or highlighting difficult parameter regions requiring non-$b\bar{b}$ channels and higher-order effects. The benchmarks provide a practical framework for interpreting LEP2 results in the MSSM parameter space and underscore the importance of considering decay and vertex-correction effects at large $\tan\beta$. Overall, the paper offers a structured set of scenarios to robustly probe MSSM Higgs phenomenology at LEP2.

Abstract

We suggest new benchmark scenarios for the Higgs-boson search at LEP2. Keeping m_t and M_SUSY fixed, we improve on the definition of the maximal mixing benchmark scenario defining precisely the values of all MSSM parameters such that the new m_h^max benchmark scenario yields the parameters which maximize the value of m_h for a given tan(beta). The corresponding scenario with vanishing mixing in the scalar top sector is also considered. We propose a further benchmark scenario with a relatively large value of |mu|, a moderate value of M_SUSY, and moderate mixing parameters in the scalar top sector. While the latter scenario yields m_h values that in principle allow to access the complete M_A-tan(beta)-plane at LEP2, on the other hand it contains parameter regions where the Higgs-boson detection can be difficult, because of a suppression of the branching ratio of its decay into bottom quarks.