What if the Higgs Boson Weighs 115 GeV?

Abstract

If the Higgs boson indeed weighs about 114 to 115 GeV, there must be new physics beyond the Standard Model at some scale \la 10^6 GeV. The most plausible new physics is supersymmetry, which predicts a Higgs boson weighing \la 130 GeV. In the CMSSM with R and CP conservation, the existence, production and detection of a 114 or 115 GeV Higgs boson is possible if \tanβ\ga 3. However, for the radiatively-corrected Higgs mass to be this large, sparticles should be relatively heavy: m_{1/2} \ga 250 GeV, probably not detectable at the Tevatron collider and perhaps not at a low-energy e^+ e^- linear collider. In much of the remaining CMSSM parameter space, neutralino-stau coannihilation is important for calculating the relic neutralino density, and we explore implications for the elastic neutralino-nucleon scattering cross section.

Figures (5)

• Figure 1: The $m_{1/2}, m_0$ plane for the CMSSM with $\tan \beta = 10$, $A = - m_{1/2}$, and (a) $\mu > 0$, (b) $\mu < 0$, showing the region preferred by the cosmological relic density constraint $0.1 \le \Omega_\chi h^2 \le 0.3$ (medium, green shading), the excluded region where $m_{\tilde{\tau}} < m_\chi$ (dark, brown shading), and the region disallowed by our $b \rightarrow s \gamma$ analysis (light shading) EFGO. Also shown as a near-vertical line is the contour $m_h = 113$ GeV for $m_t = 175$ GeV. For comparison, we also exhibit the reaches of LEP 2 searches for charginos $\chi^\pm$ and selectrons $\tilde{e}$, as well as the estimated reach of the Fermilab Tevatron collider for sparticle production Barger.
• Figure 2: The sensitivity of $m_h$ to $m_{1/2}$ in the CMSSM for (a) $\mu > 0$ and (b) $\mu < 0$. The no-scale value $A = 0$ is assumed for definiteness. The dotted (green), solid (red) and dashed (blue) lines are for $\tan \beta = 3, 5$ and $20$, each for $m_t = 170, 175$ and $180$ GeV (from left to right). The lines are relatively unchanged as one varies $\tan \beta \mathrel{\hbox{$>$$\sim$}} 10$, where they are also insensitive to the sign of $\mu$. The shaded vertical strip corresponds to $113~{\rm GeV} \le m_h \le 116~{\rm GeV}$.
• Figure 3: The sensitivity of $m_h$ to $m_{1/2}$ in the CMSSM for (a) $\mu > 0$ and (b) $\mu < 0$, this time showing the sensitivity to $A$, varied between $- m_{1/2}, 0$ and $+ 2 m_{1/2}$ (from left to right). The dotted (green), solid (red) and dashed (blue) lines are again for $\tan \beta = 3, 5$ and $20$, for $m_t = 175$ GeV. The shaded vertical strip again corresponds to $113~{\rm GeV} \le m_h \le 116~{\rm GeV}$.
• Figure 4: (a) The lower limit on $m_{1/2}$ required to obtain $m_h \ge 113$ GeV for $\mu > 0$ (solid, red lines) and $\mu < 0$ (dashed, blue lines), and $m_t = 170, 175$ and $180$ GeV, and (b) the upper limit on $m_{1/2}$ required to obtain $m_h \le 116$ GeV for both signs of $\mu$ and $m_t = 175$ and $180$ GeV: if $m_t = 170$ GeV, $m_{1/2}$ may be as large as the cosmological upper limit $\sim 1400$ GeV. The corresponding values of the lightest neutralino mass $m_\chi \simeq 0.4 \times m_{1/2}$.
• Figure 5: Cross sections for sparticle pair production at a linear $e^+ e^-$ collider, for (a) $\tan \beta = 20, \mu > 0$, (b) $\tan \beta = 20, \mu < 0$, (c) $\tan \beta = 5, \mu > 0$ and (d) $\tan \beta = 5, \mu < 0$, as functions of the centre-of-mass energy $\sqrt{s}$, compared with a nominal discovery limit EGO. The dashed (red), solid (blue) and dot-dashed (pink) lines are for $m_t = 170, 175$ and $180$ GeV, respectively. The thicker (thinner) lines are for the minimum (maximum) values of $m_{1/2}$. The different lines in each style correspond to different choices of $m_0$: those leading to $\Omega_\chi h^2 = 0.3$ and $0.1$, and the lowest allowed value, disregarding the value of the relic density. In panels (c) and (d), the maximum $m_{1/2} \simeq 1400$ GeV is taken, for which there is only one allowed value of $m_0$.