Abstract
The Higgs boson pair production at a linear $e^+e^-$ collider is analyzed in the $4\tau$ final state in the context of lepton-specific or type IV 2HDMs. Both beams are assumed to be unpolarized. The Higgs boson pairs (HA) are produced through off-shell $Z^*$ production and decay to $\tau$-jets which is the main decay channel for neutral Higgs bosons in type IV. Using a simplified detector simulation based on SiD detector at ILC, the 4$\tau$ signal is studied through the $\tau$-jet pair invariant mass reconstruction. Several benchmark scenarios are considered for center of mass energies of 500 and 1000 GeV at integrated luminosity of 500$fb^{-1}$. Among Standard Model (SM) background processes, the main background is $e^+e^- \to ZZ$ followed by $Z \to \tau\tau$. This background is however, well under control. With the luminosity assumed in the analysis, striking signals are obtained beyond the reach of LHC. Such signals would allow for precise determination of masses and cross sections and alredy much lower luminosities are sufficient for discovery.
Highlights
After the discovery of the Higgs boson at the LHC [1,2], which was predicted through a theoretical framework known as the Higgs mechanism [3,4,5,6,7,8], attention has been paid to the question of whether the observed particle belongs to a single SU(2) doublet or is part of an extended structure such as a two Higgs doublet model (2HDM) [9,10,11]
Higgs bosons; in recent studies we have shown that the ability of linear colliders like the ILC is much beyond the LHC in observing their signals with a high statistical significance
One can solve the four simultaneous equations and find the four unknown factors as in Eq (4) (The unknown factors are z1, z2, z3, z4 and momentum/energy numerical indices denote the four τ jets τ1, τ2, τ3, τ4). This is based on the assumption that the τ-jet direction has correctly been measured and a common factor can be applied to all its four-momentum components. This assumption is based on collinear approximation, which implies that the visible τ jet and the associated neutrino are collinear in the high energy limit and the jet flight direction is approximately that of the τ lepton
Summary
After the discovery of the Higgs boson at the LHC [1,2], which was predicted through a theoretical framework known as the Higgs mechanism [3,4,5,6,7,8], attention has been paid to the question of whether the observed particle belongs to a single SU(2) doublet or is part of an extended structure such as a two Higgs doublet model (2HDM) [9,10,11]. A detailed study of different production processes and decay channels of the SM Higgs boson has been presented [30]. Since both neutral Higgs bosons (H and A) decay to τ lepton pairs, the signal process has a 4τ signature to be distinguished from SM background processes like eþe− → ZZ → 4τ. The signal process including Higgs boson decays is effectively independent of tan β This is a dramatic feature of the signal under study as it makes it independent of any parameter other than the center-of-mass energy of the collider and the Higgs boson masses. Before going into details of the analysis, a brief review of the theoretical framework is presented
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