Global Analysis of Experimental Constraints on a Possible Higgs-Like Particle with Mass ~ 125 GeV

TL;DR

The paper constrains a Higgs-like state with mass $m_h \sim 125$ GeV by combining ATLAS, CMS, CDF and D0 data within a two-parameter framework of couplings to vector bosons and fermions, $a$ and $c$, plus potential loop modifications to $gg$ and $\gamma\gamma$ described by $b_s$ and $b_{em}$. It analyzes pseudo-dilaton scenarios, where tree-level couplings scale with a common factor $v/V$, and composite-Higgs models such as MCHM4 and MCHM5, mapping their predictions onto the $(a,c)$ plane and to the parameter $\xi$. Global fits show good agreement for SM-like couplings $(a,c)\approx(1,1)$ and for certain pseudo-Goldstone scenarios, while an opposite-sign coupling pattern ($a\approx -c$) can improve some channels; fermiophobic models are disfavoured. Allowing near-conformal sectors in QCD and/or QED shifts the preferred scale $V$ and can enhance the diphoton rate, illustrating how channel-specific information complements global fits and highlighting the need for more complete likelihoods from experiments to refine constraints.

Abstract

We perform a global analysis of the constraints on a possible Higgs-like particle with mass ~ 125 GeV that are provided by the ATLAS, CDF, CMS and D0 experiments. We combine the available constraints on possible deviations from the Standard Model Higgs couplings to massive vector bosons and to fermions, considering also the possibilities of non-standard loop-induced couplings to photon and gluon pairs. We analyze the combined constraints on pseudo-dilaton scenarios and on some other scenarios in which the possible new particle is identified as a pseudo-Nambu-Goldstone boson in a composite electroweak symmetry-breaking sector.

Figures (10)

• Figure 1: CMS constraints on the couplings $(a, c)$ of a possible Higgs-like particle $h$ with mass $\sim 125$ GeV arising from the (top left) ${\bar{b}} b$, (top right) $\tau^+ \tau^-$, (centre left) $Z Z^*$, (centre right) $W W^*$ and (bottom left) $\gamma \gamma$ final states. The bottom right panel displays the combination of these CMS constraints, together with lines representing the pseudo-dilaton, anti-dilaton, fermiophobic and MCHM5 scenarios. In these and subsequent analogous plots the most likely regions have the lightest shading, the dotted lines are 68% CL contours, the dashed lines are 95% CL contours, and the solid lines are 99% CL contours.
• Figure 2: Breakdown of the CMS constraints on the couplings $(a, c)$ of a possible Higgs-like $h \to WW^*$ signal with mass $\sim 125$ GeV arising from production via (left) $gg$ fusion and (right) vector-boson-fusion (VBF).
• Figure 3: Breakdown of the CMS constraints on the couplings $(a, c)$ of a possible Higgs-like $h \to \gamma \gamma$ signal with mass $\sim 125$ GeV arising from production via (left) $gg$ fusion and (right) vector-boson-fusion (VBF).
• Figure 4: The $p$-values of global fits to the CMS constraints along (upper left) the pseudo-dilaton line $a = c$, (upper right) the 'anti-dilaton' line $a = -c$, (lower left) the fermiophobic line $c = 0$, and (lower right) the MCHM5 line $a c = 1 - 2\sqrt{1 - a^2}$.
• Figure 5: ATLAS constraints on the couplings $(a, c)$ of a possible Higgs-like particle $h$ with mass $\sim 125$ GeV arising from the (top left) ${\bar{b}} b$, (top right) $\tau^+ \tau^-$, (centre left) $Z Z^*$, (centre right) $W W^*$ and (bottom left) $\gamma \gamma$ final states. The bottom right panel displays the combination of these ATLAS constraints.