Property of 125 GeV Higgs Boson from LHC Data

Seminar at Academia Sinica 07/04/2012Muneyuki Ishida 石田宗之

Higgs Boson• Particle producing fermion masses.• Electro-weak symmetry breaking. • The only particle not yet discovered in Standard

Model.• Interaction of the Higgs sector, not yet tested.• Discovering Higgs is the first priority at LHC.• 4PM Today(Taiwan time), Public announcement at CERN on the Latest data of Higgs!

• gg: gluon fusion : dominant top quark triangle + bottom quark triangle• VV: (qq-> qqh) Vector boson fusion : clear signal 　 tree-level coupling in SM• V->Vh(qq->V h) Higgs strahlung

Higgs Production Mechanism

The previous data

126 GeV by ATLAS125 GeV by CMSDiphoton enhancement

gg-fusion (γγ ｊｊ event) VV-fusion

Basic Formula of Collider Physics• Production and Decay Cross section of the process XX h AA • σXX h AA 　 = σXXh × BF(h AA)　 Prod.cross sect. from XX × Higgs BF to AA

　 BF(h AA) = σXX h ∝ 　 ΓhXX

• Two methods getting γγ enhancement:• Direct method : taking larger γγ coupling than hSM

• Indirect method : reducing Γ(h,tot) compared with hSM

At 125 GeV BF(hSM) is predicted as bb ττ WW* ZZ* gg cc γγ Zγ BF(%) 57.3 6.32 21.5 2.64 8.57 2.91 0.228 0.154 　　　 Direct method : changing the γγ 　 coupling : basically hSM : New particles contribute to the loop. Indirect method: reducing or Switching off bb and ττ 　 channel -> 3 times enhamcement compared with hSM hSM has tree-level coupling to bb producing mb . New Higgs is considered.

Ratios XA = m(hSM)=125GeV 　

R = 0.58γbb+0.06γττ+0.24γVV+0.09γgg+0.03 = Γhtot/ΓSM h

tot (ΓSM htot =4.07MeV)

Total Width of the 125 GeV Higgs

　 Γhtot = MeV : ΓSM h

tot=4.07 MeV と consistent Small : the only method to determine Γh

tot at LHC　　　　　　　 Cf. μ-Collider

Determation of total width of 125GeV Higgs

γγ 　 Enhancement 　• SUSY : MSSM (previous works) Stop loop : scalar Chargino loop: No color γγ 　 Ratio generally does not deviate much from unity. (NMSSM is different)• UED KK modes of W,q,l γγ 　 Ratio : 50% enhancement at most.Very difficult to obtain gγ > 2 (ATLAS 126GeV Higgs)

Direct method to get γγ Enhancement 　

• Production and decay mechanism of hSM

• gg-fusion

g

g

th h

W

t

t W

W

γ

γ

ht

t

t

γ

γ

Mechanism of Higgs Production/Decaygg-fusion γγ• No Tree-level couplings to Higgs• If Exotic heavy particles contribute to loop the effective couplings deviate from SM prediction.• If mass of the exotic is produced by Higgs mechanism,

its contrib. does not become small when the exotic is super heavy.　　　　　 4th generation search

VBF (VV-fusion) γγ• Big tree-level coupling : Effect from the exotics is small.

W,Z

W,Zh

2mW2/v

2mZ2/v

g, γ

g, γ

γ

γ

g, γ

g, γ

Exotics X = f, Sfermion or Scalar

Ratio of the couplingsIn the case that f,S masses are produced by Higgs rγγ = rgg =( )2

rVV = 1 　　 Qf,S : electric charge Cf,S = ½(3):Color 3(8) fS=1(1/2) complex （ real ）Exotics always reduce rγγ . getting γγ 　 Enhancement is very difficult　　　 4th generation: almost excluded. 　　　　　　　　　

The case that exotic masses are produced not from the Higgs

• λf = Yf v/mf λS=YS v/2mS2

-1< λf,S < 1 : We take this region as allowed. λf,S = 1 corresponds to Higgs mechanism.

Vγ （ =Ratio of σ(VVhγγ) to that of hSM ） >2 gγ （ =Ratio of σ(gghγγ) to that of hSM ） >1 gV （ =Ratio of σ(gghVV) to that of hSM ） <1Searching for the solution satisfying this cond.

• S8 : Exotic Scalar　　　 Color 8 Qs=1　 No Solution 　

• F8 : Exotic fermion　 Color 8 Qf=1　 There is a Solution ！　 Leptogluon (it can decay to lepton + gluon)

No Go Theorem• By using the direct method,

(where we keep tree-level hSM couplings,) it is very difficult to reproduce

Vγ>2, gγ>1

• The only solutions with Qf<1　 Ｆ８（ or Ｆ６）higher color representation: more steep.Scalar : length of lines becomes ¼ .X-axis scales with Q2 .

Indirect method • It is very difficult to obtain γγ enhancement by direct method where tree-level couplings are taken to be the same values as hSM. ghtt=ghSMtt, ghbb=ghSMbb, ghWW=ghSMWW No Go Theorem Tree-level couplings must be changed!

This line is studied in detail by a very recent work by J. Chang, K. Cheung, P.-Y.Tseng, T.C.Yuan arXiv:1206.5853[hep-ph]

2Higgs Doublet Model of type II or MSSM

• Hu= Hd= • Electroweak Symmetry breaking is broken by the VEV <Hu>= mt , <Hd>= mb through Yukawa coupling tanβ =

h,H,A and H+• = ++ two CP-even neutral Higgs : h and H with mixing angle α defined in (Hu

0,Hd0) basis.

a CP-odd neutral Higgs : A a charged Higgs : H+

NG-boson : Eaten ↓ by Z-boson

The ratios of the h couplings to hSM

• rVVh = sin(β-α), rtt

h = rcch =

rbbh = rττ

h = rμμh =

rggh=

rγγh=

W top bottom

top bottom : bottom contirib. is significant when tan β ~ 10

XC : Cross section Ratios to hSM

• XC = = Rh=0.58|rbb

h|2+ 0.06|rττh|2+ 0.24|rVV

h|2+ 0.09|rggh|2+ 0.03|rcc

h|2 ↙ Γ h,tot / Γ hSM, tot

Diphoton cross sections relative to hSM is sharply enhanced and reach maximum 3 at α = 0 .

bb, ττ strongly suppressed at α = 0 .

Γγγ 　 Enhamcement by Indirect mechanism ( reduction of total width) 　

ττ suppression

• | rττh | = | | << 1

• |α| << for moderate value of tanβ >5 　　• 　 α must be flavor-tuned to be close to zero in order to get γγ 　 enhancement. Flavor-Tuned (FT) Higgs boson. h = Hu

0

　 cf. Different from decoupling limit : α = β - π/2 . α= - 1/tanβ 　　→　 rττ

h = = 1 　

FT model with α ＝０ and 0.06

Γ h, tot = 1.5 MeV : FT model Higgs(α=0) Γ hSM, tot = 4.07 MeV Diphoton enhancement is explained by the reduction of total width.

Tevatron bb: less than 3 sigma significance

No hbb and No hττ at present• No Higgs in bb channel by ATLAS in Higgs strahlung : ZH -> ℓ+ℓ−b¯b, WH -> ℓνb¯b and ZH -> ν¯νb¯ b 110 < mH < 130 GeV 4.6 – 4.7 fb−1 at 7 TeV, 2011. No significant excess of events above the background.

ATLAS No hττ arXiv:1206.5971[hep-ex].CMS No hττ 　　　 arXiv:1202.4083[hep-ex].

Consistent with our picture.What today?

Flavor tuning of the mixing angle α in MSSM

• Squared mass matrix in the CP-even neutral Higgs in (Hu0, Hd0) basis .• MH

2= • Large tanβ 　 limit• - ε + Loop12

• Loop12 = ] Xt = At – μ cotβ ≈ At μ ： soft Higgs mass term

High Higgs mass 125 GeV requires nearly “maximal mixing” condition Xt = -

Reproducing Higgs mass • Radiative correction is proportional to mt4

• mainly comes from top and stop sector.• 2-loop Leading Log formula in Effective Field theory:mh2 =MZ

2c2β2+

t = ln mt1 mt2/mt2 , tmax.min=ln Mmax,min

2/mt2

Mmax,min 2= max,min{ ML2,MR2 }

X~t ≈ 2

mh2 takes Maximum at |Xt|= called maximal mixing condition

3-loop calculation by H3m package, implemented by the above formula.

• As varying MSUSY

Xt value giving mh peak is shifting as |Xt| = MSUSY

• Xt : negative is favored for the natural SUSY by RGE running from GUT scale.

MH122 = 0

• Requires a very severe constraint on pseudoscalar mass mA .

• mH2 = mA2 + MZ

2 s2β2

• mH+2 = mA2 + MW

2

• μ=MSUSY , Xt = -2MSUSY case• tan β mA mH mH+ 45 3MZ/2 164GeV 159GeV already excluded. 28 MZ 129GeV 122GeV 14 MZ/2 102GeV 92GeV

All these SUSY Higgs bosons should have masses comparable to mh.

LHC ggA bb,ττ Enhanced compared with Standard model in large tanβ LEPII pair production of H+ H-

• Very severe constraint already.• Will soon be probed by LHC.

Cross section Ratio XC of H, A

Vτ Vb gτ gγ gW gZ Vγ　 H 0.02 0.02 1.6 0.0 0.0 0.0 0.0 A 0.0 0.0 1.45 0.0 0.0 0.0 0.0

gτ 　 is sensitive to tanβ proportional to (tanβ)2

Discovery of H,A by this channel tanβ determined at the same time.

Decay Branching Fraction of H,A

• bb ττ gg γγ WW* ZZ*• H 91% 9 0.13 0.001 0.049 0.006• A 91 9 0.11 0.00 0 0• dominantly decays to bb.• H+ decays to τν 　 and 　 cs

tH+ b

• The light H+ can be probed by tH+ b• L = H- • BF(tHb) is constrained experimentally.

BF(tHb ) < 0.01 (0.05) for mH+=125(90) GeV

5 < tanβ < 11 (3 < tanβ < 21) Light H+ is still viable. (mH

+ >78.6 GeV at LEP).

Concluding Remarks• Enhancement of the diphoton cross section is explained by the flavor-tuned(FT) model, h = Hu0 Maximum : 3 in the case of no mixing α = 0 • Enhancement is explained by the reduction of the b¯b decay width compared to hSM. reduction of the h to τ τ signal.• The vanishing of the neutral Higgs mixing angle α requires that the masses of SUSY Higgs bosons MH, MA and MH+ are the electroweak scale. • Their production and decays are unambiguously predicted by the FT model. They can be probed by the LHC experiments. • In reality, the value of α should not be precisely zero. a cancellation of tree-level and radiative corrections in the MH12 . branching fractions could be shifted somewhat with non-zero but small α.• If one of the neutral SUSY Higgs bosons has a mass similar to that of the h-boson, there may be confusion in separating the signals. • The allowed “sweet-spot” for a A-boson of mass about mh is tanβ = 5-10.