## Contact Person(s)

David Curtin, Rouven Essig, Prerit Jaiswal, Yi-Ming Zhong More details on this mode may be found in Section 7 of*Survey of Exotic Higgs Decays*(

`arXiv:1312.4992`).

## Theoretical Motivation

Exotic Higgs decays to four jets generally proceed through a cascade decay :*h → a a*followed by

*a → j j*, where

*a*is a (pseudo-)scalar. A number of well-motivated theoretical models can lead to such Higgs decays and can be broadly classified into two categories :

*a*can mix with another heavier pseudo-scalar if a second Higgs doublet is present, for example in the NMSSM (or 2HDM + S models in general). This scenario allows for the decay of a to gluon jets, when a is light enough so that its decay to heavy SM fermions is kinematically forbidden. Further, in certain regions of the parameter space (see Section 2HDM + S for details), the couplings of*a*to the down type quarks and charged leptons can be very suppressed. In this case,*a*dominantly decays to light (mostly charm) jets. A similar situation also occurs in the "charming Higgs" scenario of the Little Higgs [1].- If there are new heavy BSM vector-like fermions that couple to
*a*, it can decay into gluons or photons through loop processes [2,3,4]. The scenario can be realized in Little Higgs models and extra dimensional models. For m_{a}above a few GeV up to half the Higgs mass,*h→ aa→ gggg*dominates over*h→ aa → γγgg*and*h → aa→ γγγγ*. In general the signal is hard to find against combinatorial background.

## Existing Experimental Constraints

None.## Estimates of Sensitivity

There are a few existing collider studies for the 14 TeV LHC run in the four-jet final state [5,6], which we briefly summarize here. There also exist collider studies which consider more exotic Higgs production modes [7], but we do not consider them here. In reference [5], Higgs production in association with leptonic W boson is considered as the production mode for m_{h}= 120 GeV followed by the Higgs decay,

*h → a a → j j j j*. Analysis is divided into categories depending on the mass of

*a*:

- m
_{a}= 4 GeV : In this case, the opening angle between the two gluons from an a decay are so small that a pair of gluons appears as a single jet, leading to Higgs final state signature of two jets, lepton and missing energy. Readers interested in the details of selection cuts are referred to reference [5]. The authors show that a discovery at 7σ significance is possible at the LHC14 with 30 fb^{−1}data assuming BR(*h→ aa → gggg*) ∼ 100 %. However, assuming a more realistic branching ratio of BR(*h → aa → gggg*) ∼ 10 % in the post Higgs discovery era, 2σ exclusion (3σ evidence) is possible with 300 fb^{−1}(500 fb^{−1}) of data at LHC14. - m
_{a}= 8 GeV : The opening angle between the two gluons from an*a*decay is larger than the previous case, so that simple jet substructure techniques can be used for discovery. Again, interested readers are referred to [5] for details of jet substructure cuts. The authors find that ∼ 3 σ statistical significance can be reached with 30 fb^{−1}data assuming BR(*h→ aa → gggg*) ∼ 100 %. With BR(*h→ aa → gggg*) ∼ 10 %, however, 2σ exclusion (3σ evidence) requires 1000 fb^{−1}(3000 fb^{−1}) of data at LHC14.

*h → aa → jjjj*is also presented in [6], with the consideration of the tth production channel besides the V h channel. The authors reach a similar conclusion for discovery prospects as described above. A more recent study [8] explores the m

_{a}> 15 GeV regime. It focuses on the substructure of fat-jets that contain an entire boosted Higgs decay, and that could be 2-, 3- or 4-pronged. Here as well, Higgs production in association with vector bosons is considered. The authors include two cases depending on the mass of the scalar, a: (i) light scalar (m

_{a}< 30 GeV) and (ii) heavy scalar (30 GeV < m

_{a}< m

_{h}/2). In the light scalar regime, the

*h→ aa → jjjj*signature can be observed at a significance of 3σ with 100 fb

^{−1}of 14 TeV LHC luminosity while for the heavy scalar case, the significance is too small to observe with the same amount of data. The above techniques can be adopted for

*h→ aa→ 4 b*searches by adding b-tags (see Section h → 4b).

## Related Decay Modes

In NMSSM and 2HDM + S models, if a is heavy enough such that decays to heavy fermions are kinematically allowed, then such decays are generally dominant for which we refer the reader to h → 4b , h → 4τ and h → 2b 2τ. For light*a*, the relevant decay modes are h → 4γ and h → 2γ 2j.

## Additional Remarks

An interesting scenario occurs when the effective*agg*vertex coupling is small enough that a decays through displaced vertices which can enhance the discovery potential of the channel [3].

## References

- [1]B. Bellazzini, C. Csaki, A. Falkowski, and A. Weiler,
*Charming Higgs*,*Phys.Rev.*D81 (2010) 075017, [`arXiv:0910.3210`]. - [2]B. A. Dobrescu, G. L. Landsberg, and K. T. Matchev,
*Higgs boson decays to CP odd scalars at the Tevatron and beyond*,*Phys.Rev.*D63 (2001) 075003, [`hep-ph/0005308`]. - [3]S. Chang, P. J. Fox, and N. Weiner,
*Visible Cascade Higgs Decays to Four Photons at Hadron Colliders*,*Phys.Rev.Lett.*98 (2007) 111802, [`hep-ph/0608310`]. - [4]S. Chang, P. J. Fox, and N. Weiner,
*Naturalness and Higgs Decays in the MSSM with a Singlet*,*JHEP*0608 (2006) 068, [`hep-ph/0511250`]. - [5]C.-R. Chen, M. M. Nojiri, and W. Sreethawong,
*Search for the Elusive Higgs Boson Using Jet Structure at LHC*,*JHEP*1011 (2010) 012, [`arXiv:1006.1151`]. - [6]A. Falkowski, D. Krohn, L.-T. Wang, J. Shelton, and A. Thalapillil,
*Unburied Higgs boson: Jet substructure techniques for searching for Higgs' decay into gluons*,*Phys.Rev.*D84 (2011) 074022, [`arXiv:1006.1650`]. - [7]B. Bellazzini, C. Csaki, J. Hubisz, and J. Shao,
*Discovering a Higgs boson decaying to four jets in supersymmetric cascade decays*,*Phys.Rev.*D83 (2011) 095018, [`arXiv:1012.1316`]. - [8]D. E. Kaplan and M. McEvoy,
*Associated Production of Non-Standard Higgs Bosons at the LHC*,*Phys.Rev.*D83 (2011) 115004, [`arXiv:1102.0704`].

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