Discovering the twin Higgs boson with displaced decays

The twin Higgs mechanism keeps the scalar sector of the Standard Model (SM) natural while remaining consistent with the nonobservation of new colored particles at the Large Hadron Collider (LHC). In this construction the heavy twin Higgs boson provides a portal between the SM particles and the twin sector, but is quite challenging to discover at colliders. In the fraternal twin Higgs setup, where light twin quarks are absent, we study a novel discovery channel for the heavy twin Higgs boson by considering its decay to a pair of light Higgs bosons, one of which subsequently decays to glueball states in the twin sector, leading to displaced vertex signatures. We estimate the sensitivity of existing LHC searches in this channel, and assess the discovery potential of the high luminosity (HL) LHC. We show that the glueballs probed by these searches are outside the sensitivity of existing searches for exotic decays of the light Higgs boson. In addition, we demonstrate that the displaced signals we consider probe a region of heavy Higgs masses beyond the reach of prompt signals. We also comment on the possibility of probing the input parameters of the microscopic physics and providing a way to test the twin Higgs mechanism with this channel.

Figure 1

Reach of HL-LHC from heavy Higgs to $ZZ\to 4\ell$ shown as the red and green shaded regions. The blue contours indicate the ratio of $(\sigma \times \mathrm{BR})$ of the light Higgs to that of the SM Higgs. In the orange region, the fine-tuning is not significantly improved relative to the SM. The gray shaded region is theoretically inaccessible due to the lower bound on the mass of the heavy Higgs.

Figure 2

Contours of the ${\log }_{10}\frac{c\tau }{\text{meter}}$ as a function of the glueball mass $m_0$ and the twin top-quark mass $m_T$. The solid (dashed) contours take the mass of the heavy Higgs to be 1000 (500) GeV. Near the lower bound of the heavy Higgs mass the decay lengths become arbitrarily long.

Figure 3

Shaded regions denote the parameter space excluded by ATLAS exotic Higgs decay DV search [62] for glueball masses from 10 to 13 GeV on left and 14 to 16 GeV on the right.

Figure 4

Projected region of parameter space excluded by muon system DV searches [63] from Higgs decays to glueballs of mass 10 GeV as well as masses in the [20,25] GeV range. For the definition of the tuned and unphysical regions, see Sec. 2.

Figure 5

Diagram for the $H\to hh\to \mathrm{DV}+\mathrm{X}$ channel. One light Higgs decays visibly while the other decays to glueballs, leading to a DV, visible objects and $E_T^{\mathrm{mis}}$ for triggering in the event.

Figure 6

Contours of efficiency (red) for passing the DV preselection cuts summarized in Table 1 for a heavy twin Higgs produced through gluon fusion (VBF) on the left (right). For the blue contours, the $n_{\text{Tracks}}$ requirement is increased from 5 to 6.

Figure 7

Contours of the number of the signal event count after all acceptance and efficiency factors have been taken into account, with $3000{\mathrm{fb}}^{-1}$ of luminosity at the HL-LHC (14 TeV). In the left, middle, and right plots, the mass of the $G_0$ state is taken to be 20, 25, and 30 GeV respectively. In the orange shaded region, the tuning is not improved over the SM (see the discussion in Sec. 2), while the blue shaded region is in tension with Higgs coupling measurements.

Figure 8

Regions with more than ten signal events with $3000{\mathrm{fb}}^{-1}$ of luminosity at the HL-LHC (14 TeV) for a range of $E_T^{\mathrm{mis}}$ cut thresholds. In the left, middle, and right plots, the mass of the $G_0$ state is taken to be 20, 25, and 30 GeV respectively. In the orange shaded region, the tuning is not improved over the SM (see the discussion in Sec. 2).

Figure 9

Discovery prospects for the heavy Higgs in the FTH setup at HL-LHC with $3000{\mathrm{fb}}^{-1}$ of luminosity at the HL-LHC (14 TeV). The CMS reach is based on the prompt decay $H\to ZZ\to 4\ell$, while the ATLAS reach is based on the $H\to hh\to \mathrm{DV}+\mathrm{X}$ channel described in Sec. 4c. The dashed contour shows the increase in the parameter region where 10 signal events pass all cuts when the $E_T^{\mathrm{miss}}$ cut is reduced to 200 GeV. The blue contours indicate the ratio of $(\sigma \times \mathrm{BR})$ of the light Higgs to that of the SM Higgs. In the orange shaded region, the tuning is not improved over the SM (see the discussion in Sec. 2).