The presence of colored particles can affect both the single and the pair Higgs productions substantially. For scalar particles, this happens if their portal couplings to the Standard Model Higgs are large and their masses are not too high. In the pr
esent work these processes are studied in the case of several leptoquarks which may appear in many beyond Standard Model theories. It is found that the constraints on the portal couplings from the single Higgs production and the decays to various channels measured by the LHC experiments still allow increased Higgs pair production rate. For the masses in the range from 180 GeV to 300 GeV, depending on the strength of such portal couplings, the Higgs pair production may reach an order to several hundred in magnitude larger rate than the Standard Model case for the 8 TeV run. Therefore, combined with the on going searches for leptoquarks by both the CMS and ATLAS, this is one of the possible scenarios to be probed directly by the current data. The current study demonstrates that if colored scalars modify scalar potentials through portal couplings, which has been studied for variety of motivations such as playing a potentially important role in electroweak phase transition, composite models or radiative neutrino masses, this fact may appear as the modified Higgs pair production.
We present our study of bound states of the fourth generation quarks in the range of 500 to 700 GeV,where we expect binding energies are mainly of Yukawa origin, with QCD subdominant. Near degeneracy of their masses exhibits a new isospin. We find th
e most interesting is the production of a color octet, isosinglet vector meson via $qbar q to omega_8$. Its leading decay modes are $pi_8^pm W^mp$, $pi_8^0Z^0$, and constituent quark decay, with $qbar q$ and $tbar t$ and $bbar b$ subdominant. The color octet, isovector pseudoscalar $pi_8$ meson decays via constituent quark decay, or to $Wg$. This work calls for more detailed study of 4th generation phenomena at LHC.
