One of the most urgent problems in the modern particle physics is unveiling the origin of masses of elementary particles, which according to the Standard Model (SM) is closely related to the Higgs boson. A lower limit on the Higgs boson mass of about 114 GeV was set more than ten years ago by the experiments on the Large Electron-Positron Collider (LEP) and more recently mass values around 160 GeV were excluded by the use of the Tevatron . Due to rarity of the process, discovering the Higgs boson production requires subtle experimental methods and precise theoretical predictions.
The Standard Model contains only one physical CP-even Higgs boson. However, many extensions of the SM, such as two-Higgs-doublet models or supersymmetric models predict also charged and CP-odd Higgs bosons. The production of a pseudo-scalar Higgs boson in the form of an external current with a generic Yukawa coupling requires the proportional coupling to the heavy quark mass, while the coefficient can be specified within any desired model.
See:
https://www.ttp.kit.edu/Preprints/ttp/ttp11/ttp11-21/ttp11-21.pdf
The Standard Model (SM) of particle physics has been very successful in explaining the properties of the fundamental particles and the interactions among them. After the dis- covery of the Higgs boson by the ATLAS and the CMS at the Large Hadron Collider (LHC), the SM has become the most accepted theory of particle physics. The measured properties of this new boson are in full agreement with the SM predictions so far.
However SM is not the compete theory of the nature as it can not describe many things including baryogenesis, neutrino masses, hierarchy problem to name a few. Many of these issues can be addressed by going beyond the SM often by invoking some extended sectors. A lot of the effort is recently being made towards the discovery of such new physics beyond the SM (BSM). A plethora of models exist in this context; a large class of which predicts an ex- tended scalar sector containing multiple scalar or pseudo-scalar Higgs particles. Extended models like the Minimal Supersymmetric Standard Model (MSSM) or Next-to-Minimal Supersymmetric Standard Model (NMSSM) etc., predict a larger variety of Higgs bosons which differ among each other for example by their mass, charge, CP-parity and cou- plings. A simple example contains an additional Higgs doublet along with the usual Higgs doublet of the SM. After the symmetry breaking this gives rise to two CP-even (scalar) Higgs bosons (h,H), one of which is identified with the SM Higgs boson (h), a CP-odd (pseudo-scalar) Higgs boson (A) as well as a pair of charged scalars (H±). This allows phenomenologically interesting scenarios particularly with pseudo-scalar resonances. One of the important goal at the LHC Run-II is to search for such resonances which requires a precise theoretical predictions for both inclusive as well as for exclusive observables.
See:
https://arxiv.org/pdf/1805.12553v1.pdf
The Higgs boson is the sole elementary particle with spin-0. However, an extended Higgs sector is a minimal extension of the Standard Model (SM) and is predicted by many theories, such as those included in supersymmetry. These extensions predict several neutral or charged spin-0 particles: one is the observed 125 GeV Higgs boson while the others would preferentially couple to heavier SM particles. Searches for heavier scalar or pseudo-scalar particles have been investigated in a variety of final states, but no evidence for such particles has been found.
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