LHC di-dijet excesses as signals of fourth-generation tetraquarks

Abstract

We postulate that the excesses of di-dijet events observed at the LHC are attributed to the production of four fourth-generation quarks

with a mass

$$m_{b'}\approx 2$$ m b ′ ≈ 2

 TeV at few-TeV scales. The di-dijet signals around the four-jet invariant mass

$$m_{4j}\approx 8$$ m 4 j ≈ 8

 TeV arise from a resonant

$$b'b'\bar{b}'\bar{b}'$$ b ′ b ′ b ¯ ′ b ¯ ′

tetraquark production, where the dijet resonances of masses about 2 TeV correspond to

$$b'\bar{b}'$$ b ′ b ¯ ′

first excited states (color-octet scalars with the principal quantum number

$$n=2$$ n = 2

) in a Yukawa potential created by Higgs boson exchanges. Those around

$$m_{4j}\approx 3.6$$ m 4 j ≈ 3.6

 TeV originate from a non-resonant

$$b'b'\bar{b}'\bar{b}'$$ b ′ b ′ b ¯ ′ b ¯ ′

production, where the dijet resonances of masses 0.95 TeV correspond to

$$b'\bar{b}'$$ b ′ b ¯ ′

ground states (color-octet vectors with

$$n=1$$ n = 1

). It is shown that a

$$b'\bar{b}'$$ b ′ b ¯ ′

system with

$$m_{b'}\approx 2$$ m b ′ ≈ 2

 TeV in the Yukawa potential does generate the aforementioned bound state spectrum. We then illustrate that the observed excesses can be accommodated in our setup by translating the fourth-generation model to the effective theories containing color-octet scalars and vectors available in the literature. Simply speaking, our scenario can be viewed as a TeV-scale analogue of the search for a fully charmed tetraquark via the four-muon channels

$$X(6900)\rightarrow (c\bar{c})(c\bar{c})\rightarrow 4\mu $$ X ( 6900 ) → ( c c ¯ ) ( c c ¯ ) → 4 μ

at a GeV scale.