Interpreting LHC Higgs Results from Natural New Physics Perspective

TL;DR

The paper analyzes 2011 LHC and Tevatron Higgs data through an effective Higgs framework to constrain natural new-physics scenarios addressing electroweak naturalness. By mapping simplified models with scalar or fermionic top partners, as well as multi-Higgs configurations, to a common set of couplings $c_V$, $c_b$, $c_\tau$, $c_g$, and $c_\gamma$, it derives bounds on partner masses and model parameters from combined Higgs-rate measurements in $h\to ZZ^*$, $h\to WW^*$, and $h\to \gamma\gamma$ channels. The results show that a single light top-like scalar or fermionic partner is disfavored below roughly 240 GeV and 220 GeV respectively for a 125 GeV Higgs, while more complex models with multiple partners or non-universal suppression can accommodate current data but typically require heavier states or small mixing. Overall, the work demonstrates that Higgs coupling measurements already impose meaningful constraints on naturalness-motivated new physics and illustrate how future data could either reveal deviations or further tighten these bounds.

Abstract

We analyze the 2011 LHC Higgs data in the context of simplified new physics models addressing the naturalness problem. These models are expected to contain new particles with sizable couplings to the Higgs boson, which can easily modify the Higgs production cross sections and branching fractions. We focus on searches in the Higgs to 4 leptons and Higgs to diphoton channels, in the latter case including the vector boson fusion production mode. Combining the available ATLAS and CMS data in these channels, we derive constraints on an effective low-energy theory of the Higgs boson. We then map several simplified scenarios to the effective theory, capturing numerous natural new physics models such as supersymmetry and Little Higgs, and extract the constraints on the corresponding parameter space. We show that simple models where one fermionic or one scalar partner is responsible for stabilizing the Higgs potential are already constrained in a non-trivial way by LHC Higgs data.

Figures (9)

• Figure 1: Best-fit values and $1\sigma$ bands for the rates $R_{\gamma \gamma}$, $R_{\gamma \gamma jj}$, $R_{WW}$, $R_{ZZ}$, and $R_{b \bar{b}}$ for a Higgs mass between 120 GeV and 130 GeV. We also show the combination of all the channels ( bottom-right). In all but the CMS dijet measurement, the results are computed using the reported results and assuming gaussian statistics. For the CMS dijet, the best fits are derived by repeating the analysis reported in Collaboration:2012tw, not taking systematic uncertainties into account. The results in the dijet mode are found to be conservative.
• Figure 2: The allowed parameter space of the effective theory given in Eq. \ref{['eq:1']}, derived from the LHC and Tevatron constraints for $m_h = 125$ GeV. We display the $1\sigma$ allowed regions for the rates in Eqs. \ref{['eq:4']}-\ref{['eq:6']}: $R_{\gamma \gamma}$ (purple), $R_{ZZ}$ (blue), $R_{WW}$ (light grey), $R_{\gamma \gamma jj}$ (beige), and $R_{b \bar{b}}$ (orange). The "Combined" region (green) shows the 95% CL allowed region arising from all channels. The crossing of the dashed lines is the SM point. The top left plot characterizes models in which loops containing beyond the SM fields contribute to the effective 5-dimensional $h \, G_{\mu \nu}^a G_{\mu \nu}^a$ and $h \, A_{\mu \nu} A_{\mu \nu}$ operators, while leaving the lower-dimension Higgs couplings in Eq. \ref{['eq:1']} unchanged relative to the SM prediction. The top right plot characterizes composite Higgs models and can be compared to Azatov:2012bz and Espinosa:2012ir. The lower plots characterize top partner models where only scalars and fermions with the same charge and color as the top quark contribute to the effective 5-dimensional operators, which implies the relation $\delta c_\gamma = (2/9) \delta c_g$. The results are shown for 2 different sets of assumptions about the lower-dimension Higgs couplings that can be realized in concrete models addressing the Higgs naturalness problem.
• Figure 3: Left: Favored region, 95% CL, in the $m_{\tilde{t}}-m_h$ plane, derived from the combination of all search channels, for the one-scalar model described in Sec. \ref{['sec:onscalar']}. Right: Constraints for $m_h=125$ GeV. The three bands show the $1\sigma$ allowed regions: $R_{\gamma \gamma}$ (purple), $R_{b \bar{b}}$ (orange), $R_{\gamma \gamma jj}$ (beige). The three curves show the theoretical predictions as a function of $m_{\tilde{t}}$: $R_{\gamma \gamma}$ (solid-purple), $R_{b \bar{b}}$ (dashed-orange), and $R_{\gamma \gamma jj}$ (dotted-beige). Only 3 channels are shown, but all channels are included. The region to the right of the green line at $m_{\tilde{t}}= 240$ GeV shows the 95% CL experimental allowed region.
• Figure 4: Left: The favored region at 95% CL for $m_h = 125$ GeV, derived from the combination of all search channels, in the two scalar model with $m_{{\tilde{t}_2}} \gg m_{{\tilde{t}_1}}$. Also shown are contours of constant $m_h = 125$ GeV assuming the 1-loop MSSM relation between Higgs and stop masses, for $m_{\tilde{t}_2}=1,2,$ and 10 TeV. Right: Same for $m_{{\tilde{t}_2}} = m_{{\tilde{t}_1}}$. Also shown is a band corresponding to 124 GeV $<m_h<$ 16 GeV assuming the 1-loop MSSM relation between Higgs and stop masses. Additional, model-dependent, bounds on stops from direct searches are not shown.
• Figure 5: Left: Favored region, 95% CL, in the $m_{T}-m_h$ plane, derived from the combination of all search channels, for the single-fermion, no-mixing model described in Sec. \ref{['sec:nomixing']}. Right: Constraints assuming $m_h=125$ GeV. The three bands show the $1\sigma$ allowed regions: $R_{\gamma \gamma}$ (purple), $R_{b \bar{b}}$ (orange), $R_{\gamma \gamma jj}$ (beige). The three curves show the theoretical predictions as a function of $m_T$: $R_{\gamma \gamma}$ (solid-purple), $R_{b \bar{b}}$ (dashed-orange) and $R_{\gamma \gamma jj}$ (dotted-beige). Only 3 channels are shown, but all channels are included. The region to the right of the green line at $m_T= 220$ GeV shows the 95% CL experimental (combined) allowed region.