Two Higgs Doublets, a 4th Generation and a 125 GeV Higgs: A Review

Table 2

List of points (models) in parameter space for the 4G2HDM’s of type I with 𝑚_ℎ=125 GeV, tan𝛽=1, and 𝜖_𝑡=𝑚_𝑡/𝑚_𝑡′, allowed at 95% CL by EWPD and B-physics flavor data. Points 1-2 have 𝑚_𝑡′−𝑚_𝑏′>150 GeV, while points 3–5 have a large inverted splitting 𝑚_𝑏′−𝑚_𝑡′>150 GeV. Points 6 and 7 have nearly degenerate 4th generation quark and lepton doublets. Points 8–11 give BR(𝑡^′→𝑡ℎ)∼𝒪(1) (see Figure 16 in Section 5), while points 12 and 13 give BR(𝑏^′→𝑡𝐻⁺)∼𝒪(1) (see Figure 17 in Section 5). Point 4 has a light 180 GeV pseudoscalar Higgs (𝐴) and points 12 and 13 have a light 300 GeV charged Higgs. Points 1, 8, and 9 have a small 𝑡^′−𝑏/𝑡−𝑏^′ mixing angle (𝜃₃₄≤0.05), while points 4 and 10–13 have a Cabibbo size 𝑡^′−𝑏/𝑡−𝑏^′ mixing angle (𝜃₃₄∼0.2).

	4G2HDMI: 𝑚ℎ=125 GeV, tan𝛽=1, 𝜖𝑡=𝑚𝑡/𝑚𝑡′
Point no.	𝑚𝑡′	𝑚𝑏′	𝑚𝜈′	𝑚𝜏′	𝑚𝐴	𝑚𝐻	𝑚𝐻^+	sin𝜃34	𝛼	|𝜆^𝑡′𝑠𝑏|
1	570	403	118	184	319	993	806	0.02	0.46𝜋	<0.002
2	596	435	124	277	840	172	595	0.09	0.32𝜋	<0.0005
3	425	591	1151	1085	817	203	646	0.08	0.46𝜋	<0.001
4	441	595	385	556	180	998	661	0.21	0.69𝜋	<0.001
5	429	580	587	759	978	304	454	0.13	0.95𝜋	<0.0005
6	555	564	1185	1180	501	674	661	0.06	0.62𝜋	<0.0007
7	409	401	424	429	509	837	472	0.1	0.68𝜋	<0.0006
8	500	450	1079	1005	745	439	750	0.05	𝜋/2	<0.0006
9	500	450	160	176	733	414	750	0.05	𝜋/2	<0.0006
10	500	450	786	652	833	308	750	0.2	𝜋/2	<0.0006
11	500	450	211	268	798	289	750	0.2	𝜋/2	<0.0006
12	450	500	711	618	500	215	300	0.2	𝜋/2	<0.004
13^a	450	500	108	253	872	295	300	0.2	𝜋/2	<0.004

aPoints 12 and 13 require 𝜖_𝑏≲𝑚_𝑏/𝑚_𝑏′ in order to have BR(𝑏^′→𝑡𝐻⁺)∼𝒪(1) (see Figure 17).