Paper detail

Experimental signals for a second resonance of the Higgs field

In the region of invariant mass 620$÷$740 GeV, we have analyzed the ATLAS sample of 4-lepton events that could indicate a new scalar resonance produced mainly via gluon-gluon fusion. These data suggest the existence of a new heavy state $H$ whose mass $660÷680$ GeV would fit well with the theoretical range $M_H = 690 \pm 10 ~({\rm stat}) \pm 20 ~({\rm sys})~ {\rm GeV}$ for the hypothetical second resonance of the Higgs field that has been recently proposed and which would couple to longitudinal W's with the same typical strength of the low-mass state at $125$ GeV. Since the total width $Γ_H$ is very poorly determined, to sharpen the analysis of the precious ATLAS data, we have considered a particular correlation between resonating peak cross section $σ_R(pp\to H \to 4l)$ and the ratio $γ_H=Γ_H/M_H$. This correlation should be nearly insensitive to the precise value of $Γ_H$ and mainly determined by the lower mass $m_h=$ 125 GeV. Equivalently, if this correlation holds true, one could also fit $m_h$ from the 4-lepton data in the high-mass range 620$÷$740 GeV. The result $(m_h)^{\rm fit} \sim (125 \pm 13)$ GeV reproduces the direct measurement of the Higgs particle mass and thus supports the idea that $m_h$ and $M_H$ are the masses of two different excitations of the same field. Therefore, if we combine with the excess at 680 GeV in the ATLAS $γγ$ distribution, there are now two signals for a new resonance in the same mass region. Even though, quantitatively, the global statistical significance of each effect is modest, still the sharp correlation $γ_H-σ_R$ in the 4-lepton channel should induce to consider seriously these indications.