Mass-degenerate Higgs bosons at 125 GeV in the Two-Higgs-Doublet Model

Abstract

The analysis of the Higgs boson data by the ATLAS and CMS Collaborations appears to exhibit an excess of h --> gammaγevents above the Standard Model (SM) expectations; whereas no significant excess is observed in h --> ZZ* --> {four lepton} events, albeit with large statistical uncertainty due to the small data sample. These results (assuming they persist with further data) could be explained by a pair of nearly mass-degenerate scalars, one of which is a SM-like Higgs boson and the other is a scalar with suppressed couplings to W+W- and ZZ. In the two Higgs doublet model, the observed γγand ZZ* --> {four lepton} data can be reproduced by an approximately degenerate CP-even (h) and CP-odd (A) Higgs boson for values of \sin(β-α) near unity and 0.7 < \tanβ< 1. An enhanced γγsignal can also arise in cases where m_h ~ m_H, m_H ~ m_A, or m_h ~ m_H ~ m_A. Since the ZZ* --> {four lepton} signal derives primarily from a SM-like Higgs boson whereas the γγsignal receives contributions from two (or more) nearly mass-degenerate states, one would expect a slightly different invariant mass peak in the ZZ* --> {four lepton} and γγchannels. The phenomenological consequences of such models can be tested with additional Higgs data that will be collected at the LHC in the near future.

18 pages, 19 pdf figures, v2: references added, v3&v4: added refs and explanations

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• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
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