Higgs couplings at high scales

Abstract

We study the off-shell production of the Higgs boson at the LHC to probe Higgs physics at higher energy scales utilizing the process gg → h à → ZZ. We focus on the energy scale dependence of the off-shell Higgs propagation, and of the top quark Yukawa coupling, y t ðQ 2 Þ. Extending our recent study [D. Goncalves, T. Han, and S. Mukhopadhyay, Phys. Rev. Lett. 120, 111801 (2018).], we first discuss threshold effects in the Higgs propagator due to the existence of new states, such as a gauge singlet scalar portal, and a possible continuum of states in a conformal limit, both of which would be difficult to discover in other traditional searches. We then examine the modification of y t ðQ 2 Þ from its Standard Model (SM) prediction in terms of the renormalization group running of the top Yukawa, which could be significant in the presence of large flat extra dimensions. Finally, we explore possible strongly coupled new physics in the top-Higgs sector that can lead to the appearance of a nonlocal Q 2 -dependent form factor in the effective top-Higgs vertex. We find that considerable deviations compared to the SM prediction in the invariant mass distribution of the Z-boson pair can be conceivable, and may be probed at the 2σ level at the high-luminosity 14 TeV HL-LHC for a new physics scale up to Oð1 TeVÞ, and at the upgraded 27 TeV HE-LHC for a scale up to Oð3 TeVÞ. For a few favorable scenarios, 5σ level observation may be possible at the HE-LHC for a scale of about Oð1 TeVÞ.

Quantum Critical Higgs: from AdS5 to colliders

“…This is one of the main channels for studying the Higgs at the LHC and is sometimes called the Golden Channel since it provides such a clean signal. Studies in the off-shell region are an interesting way to search for new particles and for bounding the Higgs width [2,19,[52][53][54]. In the off-shell region with √ s > 2M Z , at the lowest order, we need to take into account two diagrams, gg → H → ZZ and gg → ZZ through a fermion box (i.e.…”

“…QCH models have some common features with the unparticles of Georgi [3][4][5][6][7][8][9][10][11][12][13]. The conformal sector can show up in experiments as "stuff" that is not like particles, but more like a continuum of particles [14][15][16][17][18][19][20][21][22]. Several processes were suggested in ref.…”

New phenomenological and theoretical perspective on anomalous ZZ and Zγ processes

“…Finally, it would be interesting to discuss nextto-leading-order effects and in particular their contribution to the 00 amplitude to understand whether this can be exploited to search for specific BSM scenarios, e.g., Refs. [44,45], in the gg → ZZ amplitude.…”

Probing Ztt¯ couplings using Z boson polarization in ZZ production at hadron

“…The Ztt coupling contributes to ZZ production through top-quark loop effects in the gluon fusion channel. The process, gg → ZZ, has been used to constrain the Higgs boson width through the interference of box and triangle diagrams and it has been shown to be sensitive to many NP effects [27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In particular, the polarization of the Z boson pair highly depends on the Ztt coupling.…”