1. Phenomenology of Twin Higgs Model
Shufang Su • U. of Arizona
Hock-Seng Goh, Shufang Su
Work in progress

2. Outline Twin Higgs Model Collider phenomenology Twin Higgs mechanism-
Twin Higgs Model
Twin Higgs mechanism
Left-right Twin Higgs model
New particles and model parameters
Collider phenomenology
Heavy top quark
Heavy gauge bosons
Higgses
S. Su

3. Twin Higgs mechanism Mirror symmetry Left-right symmetry
Higgs as pseudo-Goldstone boson of a global symmetry
Its mass is protected against radiative corrections
Little Higgs mechanism: collective symmetry breaking
Twin Higgs mechanism: discrete symmetry
Mirror symmetry
Type IA TH: Chacko, Goh, Harnik, hep-ph/
Type IB TH: Chacko, Nomura, Papucci, Perez, hep-ph/
Left-right symmetry
Type II TH: Chacko, Goh, Harnik, hep-ph/
S. Su

4. SU(2)L  SU(2)R  U(1)B-L  SU(2)LU(1)Y
Left-right Twin Higgs model -
Global U(4) , with subgroup SU(2)L  SU(2)R  U(1)B-L gauged
Left-right symmetry: gL=gR (yL=yR)
A linear realization
SM Higgs doublet
EWSB
SM neutral Higgs: H
3 eaten by heavy gauge bosons
U(4)  U(3)
SU(2)L  SU(2)R  U(1)B-L  SU(2)LU(1)Y
7 GB
S. Su

5. Twin Higgs mechanism -
Quadratic divergence forbidden by left-right symmetry
gL=gR=g
U(4) invariant, does not contribute to the mass of GB
Non-linear
realization
Log contribution:
mH  g2f / (4 ), natural for f  TeV
S. Su

6. Left-right Twin Higgs model
Fermion sector:
Top quark mass:
Top quark mass eigenstates: SM top and tH
EW precision constraints on SU(2)R gauge boson mass  f  2 TeV
Introduce another Higgs field that only couples to gauge sector
Which has a larger VEV
S. Su

7. SU(2)L  SU(2)R  U(1)B-L  SU(2)LU(1)Y
Left-right Twin Higgs model
U(4)  U(4), with gauged SU(2)LSU(2)RU(1)B-L + LR symmetry -
Couple to gauge boson only
SM Higgs doublet
EWSB
SM neutral Higgs: H
SU(2)L Higgs doublet
H1, H20
3 eaten by heavy gauge bosons
Left 3 Higgses:
neutral Higgs 0, charged Higgs 
U(4)  U(3)
SU(2)L  SU(2)R  U(1)B-L  SU(2)LU(1)Y
 U(4)
 U(3)
7 GB
7 GB
f2  f1
S. Su

8. New particles Heavy gauge bosons: WH, ZH m2WH,ZH  g2(f12+f22)-
Heavy gauge bosons: WH, ZH m2WH,ZH  g2(f12+f22)
Heavy top: tH m2TH  M2+y2f12
Other SU(2)R Higgses:  m2  g4/(162)f22 log(/gf2)
0 m20  B (f2/f1)
B: small, ( GeV)2
Other SU(2)L Higgs H1 m2H1, H20  
H20 : soft symmetry breaking, O(f1)
S. Su

9. Model parameters Model parameters: f1, (f2, y), , M, B, -
Model parameters: f1, (f2, y), , M, B, 
Determine particle masses and interactions
fixed by Higgs VEV
= 4f1 or 2f1
M=150 GeV
B=50 GeV
 = f1/2
fixed by top quark mass
S. Su

10. Heavy top tH production-
single heavy top production
heavy top pair production
S. Su

11. Heavy top tH decay 3 b + 1 j + 1 lepton + missing ET j  l t tH W- j W tH  b t l 
3 b + 1 j + 1 lepton + missing ET j tH W b l 
1 b + 1 j + 1 lepton + missing ET
S. Su

12. Heavy gauge boson production-
Drell-Yan process
S. Su

13. ZH decay - ZH
2 b + 2 j + 1 lepton + missing ET t q b W l  ZH
S. Su

14. WH decay WH tH b: 4b + 1 lepton + missing ET- WH
tH b: 4b + 1 lepton + missing ET
tH bW : 2b + 1 lepton + missing ET
tH tZ: 2b + 3 lepton + missing ET
S. Su

15. Higgses SM Higgs mH  150-170 GeV, depending on f1,  and M
Higgs searches:
gg  H  ZZ*  llll
gg  H  WW*  ll
WBF  qqH  qqWW*  qqll
SU(2)R Higgs: 0, 
0  bb j
  tb
2b + 1 lepton + missing ET
S. Su

16. 0 Neutral Higgs 0 gg  0  bb, QCD background overwhelming-
Neutral Higgs 0
gg  0  bb, QCD background overwhelming
no W0, Z0 associated production (no such coupling)
bb0 , tb0, tt0 cross section small
Produced via the decay of heavy particles WH  b t W 0 l 
4 b + 1 lepton + missing ET
S. Su

17.  -
Neutral Higgs 
no W, Z associated production (no such coupling)
bb , tb, tt cross section small
Produced via the decay of heavy particles j W tH  b t l 
3 b + 1 j + 1 lepton + missing ET
S. Su

18. H1, H20 H20: good dark matter candidates-
Higgs that couple to gauge boson only: H1, H20
H1H20, H1H1, H20H20, associated production (small)
H20 stable : missing energy
H1  H20 + soft jets/leptons
if decay fast enough: appears as missing energy
if decay slow: track !
H20: good dark matter candidates
S. Su

19. M=0 case Top Yukawa: f1 v tH = (TL, tR), mtH = yf1-
Top Yukawa: f1 v
tH = (TL, tR), mtH = yf1
tSM = (tL, TR), mt = yv
Gauge coupling
Yukawa coupling
0  tH  tH
0  t  t
0  tH  t
H  t  t
H  tH  tH (small)
H  tH  t
W  t  b
W  tH  b
WH  t  b
WH  tH  b
Z  t  t
Z  tH  tH
Z  tH  t
ZH  t  t
ZH  tH  tH
ZH  tH  t
  tH  b
  t  b
  t + b (100%) X
S. Su

20.  decay No two body decay Leading decay: 3 body-
No two body decay
Leading decay: 3 body
off-shell
0  bb: bbqq final states
huge QCD bg
H  ZZ*, WW*
small signal
S. Su

21.  discovery -
Difficult
unless   Hqq
small signal
S. Su

22. 0 discovery -
difficult
small signal
absent
S. Su

23. Heavy top tH discovery single, pair production does not change much.-
single, pair production does not change much.
decay: only tH  b  (100%)
100%
either huge QCD bg
Or small signal
absent
S. Su

24. Heavy gauge boson discovery-
ZH, WH drell-yan cross section does not change
ZH: ZH  ll does not change much 
Br(ZH  t tH) =0
WH: difficult
For M=0
discovery of almost all the particle are difficult
except for ZH
either huge QCD bg
Or small signal
absent
S. Su

25. Conclusions -
Left-right twin Higgs model: Higgs as pseudo-goldstone boson
quadratic divergence forbidden by left-right symmetry
New particles
Heavy gauge boson: WH, ZH
Heavy top quark tH
New Higgses: 0, , H1, H20 (DM)
M0: rich collider phenomenology
M=0: difficult except for ZH
Future work
Pick certain channel for detailed study: background, cuts,…
Identify twin Higgs mechanism
Dark matter study
Comparison with other models, e.g., little higgs
S. Su