125 GeV Higgs Boson and Gauge Higgs Unification · V=246 GeV Veff Our vacuum is NOT true vacuum!...
Transcript of 125 GeV Higgs Boson and Gauge Higgs Unification · V=246 GeV Veff Our vacuum is NOT true vacuum!...
Nobuchika Okada
The University of Alabama
Miami 2013 , Fort Lauderdale, Dec. 12‐18, 2013
125 GeV Higgs Boson and Gauge‐Higgs Unification
Discovery of Higgs boson at LHC !
Standard Model Higgs boson has been discovered at LHC through a variety of decay modes.
CMS
7/04/2012
Electroweak symmetry breaking
Higgs potential:
The vacuum expectation value breaks the electroweak gauge symmetry
Higgs mass is determined: 125‐126 GeV Higgs self coupling is determined
Higgs boson mass generation
Implications of the Higgs boson discovery
What happens for Higgs potential at high energies?
Assuming the SM is valid up to, say, Planck scale, Quantum Field Theory allows us to calculate the Higgs potential at very high energies.
Renormalization group improved effective potential
@ high energies
: Effective Higgs self‐coupling including quantum corrections, calculable in the SM
1‐loop renormalization group equation of the Higgs quartic coupling
@ EW scale:
RGE extrapolation of the Higgs quaric coupling
Higgs self‐coupling becomes negative around 10^10 GeV << M_Pl for mh=125 GeV
Implication?
V=246 GeV
Veff
Our vacuum is NOT true vacuum! Quantum tunneling is possible to the true minimum.
EW Vacuum stability problem if
New Physics which takes place at E < 10^10 GeV can solve this problem.
RGE running of Higgs self‐coupling is altered by new particle effects
SM RGE running
SM + new physics RGE running
Example: Seesaw extension of SM
Type II Seesaw: Gogoladze, NO &Shafi, PRD 78, (2008) 085005
Dev, Gosh, NO, Saha, JHEP 1303 (2013) 150
Type III Seesaw:Gogoladze, NO &Shafi, PLB 668 (2008) 121
He, NO, Shafi, PLB B716 (2012) 197
Another picture for the stability bound?
Effective Low Energy Theory = Standard Model
mh =125 GeV
?
BSM
Special meaning of ?
Gauge‐Higgs Unification (GHU) Scenario
5D Standard Model
5‐dim. theory compactified on orbifold
y
SM
All SM fields reside in the bulk
Higgs boson is unified into 5th component of gauge fields in higher dimension
Manton, NPB 158 (1979) 141 Fairlie, PLB 82 (1979) 97Hosotani, PLB 126 (1983) 309
PLB129 (183) 193
Basic structure 5 dim SU(3) gauge theory (toy model)
adj doub
let
doublet singlet
SU(3) gauge =
Impose non‐trivial boundary conditions (parity assignment)
are Z2 even fields, others odd fields
Zero modes for odd fields are project out,
So SU(3) is broken to SU(2) times U(1) by this parity assignment
5D SU(3) GHU Lagrangian5D SU(3) gauge kinetic term
SU(2) x U(1) EW gauge kinetic term Higgs doublet kinetic term
No Higgs potential @ tree level
Higgs potential is generated at quantum level with Kaluza‐Klein fields
Properties
(1) The SM Higgs doublet is identified as the 5th component of 5D bulk gauge field
(2) Mass term and Higgs self‐coupling are protected to be zero by the 5D gauge invariance
(3) 5D gauge invariance is broken by the boundary conditions and as a result, Higgs mass and self‐coupling are induced through quantum corrections at low energies
(4) However, there is no quadratic divergence in the theory
(5) Low energy effective theory of the model is equivalent to the SM with a certain boundary condition
Gauge‐Higgs condition: Haba, Matsumoto, N.O. & Yamashita, JHEP 02 (2006) 073
5D flat GHU at E < mKK = SM + GH condition for Higgs self‐coupling
1‐loop effective potential in 5D GHU
1‐loop effective potential in SM with a cutoff
RGE solution
UV completion of the Standard Model with GHU model
Effective Low Energy Theory = Standard Model 5D GHU
Compactification scale ~ 10^10 GeV
mh =125 GeV
Gogoladze, NO, Shafi, PLB 665 (2007) 257659 (2008) 319
Higgs mass as a function of the compactification scale
50
Compactification scale can be lower, say, 1 TeV?
Need extra fermions to reproduce mh=125‐126 GeV
Realistic SU(3) x U(1)’ GHU with bulk fermions Maru & N.O., PRD 87 (2013) 095019 Maru & N.O.,arXiv: 13103348
Bulk fermions with half‐periodic BC & bulk mass
Quantum numbers: n=0,1,2,3,….U(1) charge in the electroweak SU(3) alpha: coupling with Higgs boson
: determined once the SU(3) repr. is fixed
M: bulk mass term
Example: 10‐plet under the EW SU(3)
SU(2) representation
U(1) charge in SU(3) Free parameters: mKK & M, and Q’
Higgs mass with color triplet bulk fermions Maru & N.O., arXiv: 1310.3348
With color‐triplet 6‐plet/10‐plet/15‐plet
Higgs mass with color triplet bulk fermions Maru & N.O., arXiv: 1310.3348
With color‐triplet 6‐plet/10‐plet/15‐plet
SM RGE
GH condition
10‐plet15‐plet 6‐plet
Once the rep. and m_KK are fixed, bulk mass is determined so as to reproduce Higgs mass 125 GeV
Contributions to effective Higgs boson couplings
Kaluza‐Klein modes of the SM particle and new bulk fermions contribute Higgs‐to‐digluon, diphoton couplings
gluon
gluon
top quark loop
+ Kaluza‐Klein top + new colored fermion
W boson looptop quark loop
+ KK fermions + KK W boson
1. Main production mode: gluon fusion
gluon
gluon
top quark loop
+ Kaluza‐Klein top
Opposite signs!
Maru & Okada, PRD 77 (2008) 0550101
2. Primary discovery mode: Higgs decay to diphoton
W boson loop
top quark loop
+ KK fermions+ KK W‐bosons
+ New Fermions
SU(3) x U(1)’ GHU model
with 10‐plet bulk color triplet‐fermion realizing mh=125 GeV
The KK mode contribution to Higgs‐digluon coupling alters the Higgs boson production cross section at LHC
Maru & N.O., arXiv: 1310.3348
KK fermions can be tested at LHC Run II
The KK mode contribution to Higgs‐digphoton coupling alters the signal strength of Higgs‐to‐diphoton channel
Lightest KK QEM=‐1/3
Lightest KK QEM=+2/3
For Rgg > 0.9 (mKK > 2.5 TeV), the deviation is less than 10% .
KK fermion contributions to Higgs‐Z‐gamma?
ZKK fermion mass splitting:
Interaction vertices between mass eigenstates
No contribution to h‐Z‐gamma @1‐loop !
Maru & N.O., PRD 88 (2013) 037701
Interactions between KK modes & W, Z Example: 10‐plet:
4(+2, 0mw)
4(+1, ‐1 mw)
4(0, +2 mw)
3(1, +1 mw)
3(0, ‐2 mw)
3(‐1, ‐3 mw) 4(‐1, +3mw)
2(0, 0 mw)
2(‐1, +1 mw) 1(‐1, ‐1 mw)
Maru & N.O., arXiv: 1310.3348
4(+2, 0mw)
4(+1, ‐1 mw)
4(0, +2 mw)
3(1, +1 mw)
3(0, ‐2 mw)
3(‐1, ‐3 mw) 4(‐1, +3mw)
2(0, 0 mw)
2(‐1, +1 mw) 1(‐1, ‐1 mw)
Heavy fermion cascades @ LHC Run II Maru & N.O., arXiv: 1310.3348
Heavy top/bottom quarks with suitable Q’ charge assignments
Conclusions
The Higgs boson is finally discovered!
Higgs physics, one of the most important research area in particle physics, has just begun.
There are many things to do to test the SM Higgs sector.
Observed Higgs boson properties have lots of implications to new physics beyond the SM.
Gauge‐Higgs unification as UV completion of the Standard Model
Quadratic divergence free KK mode mass as an effective cutoff
Gauge‐Higgs condition new interpretation of a vanishing Higgs quartic coupling
Reproducing Higgs mass 125‐126 GeVwith half‐periodic fermions
GH condition at TeV
New contribution to Higgs‐diphoton coupling
No contribution (@1‐loop) to Higgs‐Z‐gamma
Hunting KKs @ LHC Run II