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Property of 125 GeV Higgs Boson from LHC Data

Property of 125 GeV Higgs Boson from LHC Data. Seminar at Academia Sinica 07/04/2012 Muneyuki Ishida 石田宗之. Higgs Boson. Particle producing fermion masses. Electro-weak symmetry breaking. The only particle not yet discovered in Standard Model.

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Property of 125 GeV Higgs Boson from LHC Data

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  1. Property of 125 GeV Higgs Boson from LHC Data Seminar at Academia Sinica 07/04/2012 Muneyuki Ishida 石田宗之

  2. 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!

  3. Higgs Production Mechanism • 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

  4. The previous data 126 GeV by ATLAS 125 GeV by CMS Diphoton enhancement gg-fusion (γγｊｊ event) VV-fusion

  5. Basic Formula of Collider Physics • Production and Decay Cross section of the process XX h  AA • σXX h  AA = σXXh ×BF(h  AA) Prod.crosssect. from XX × Higgs BF to AA BF(h  AA) = σXX  h ∝　ΓhXX • Two methods getting γγenhancement: • Direct method : takinglarger γγ coupling than hSM • Indirect method : reducing Γ(h,tot) compared with hSM

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

  7. Ratios XA = m(hSM)=125GeV • R = 0.58γbb+0.06γττ+0.24γVV+0.09γgg+0.03=Γhtot/ΓSM htot (ΓSM htot=4.07MeV) •  Total Width of the 125 GeV Higgs

  8. Determation of total width of 125GeV Higgs Γhtot = MeV :ΓSM h tot=4.07 MeVとconsistent Small : the only method to determine Γhtotat LHC Cf. μ-Collider

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

  10. Direct method to get γγEnhancement • Production and decay mechanism of hSM • gg-fusion γ γ g t W t h h h t t W t t W γ g γ

  11. Mechanism of HiggsProduction/Decay gg-fusion  γγ • No Tree-levelcouplings 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 2mW2/v 2mZ2/v h W,Z

  12. ExoticsX = f, S fermion or Scalar g, γ g, γ γ γ g, γ g, γ

  13. Ratio of the couplings In the case that f,S masses are produced by Higgs rγγ= rgg=( )2 rVV = 1Qf,S: electric charge Cf,S = ½(3):Color 3(8)fS=1(1/2) complex（real） Exotics always reduce rγγ.  getting γγEnhancementis very difficult 4th generation: almost excluded.

  14. The case that exotic masses are produced not from the Higgs • λf =Yf v/mfλS=YS v/2mS2 -1< λf,S < 1 : We take this region as allowed. λf,S= 1corresponds to Higgsmechanism. Vγ（=Ratio of σ(VVhγγ)to that of hSM）>2 gγ（=Ratio of σ(gghγγ)to that of hSM）>1 gV（=Ratio of σ(gghVV) to that ofhSM）<1 Searching for the solution satisfying this cond.

  15. 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)

  16. 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 .

  17. 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]

  18. 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 =

  19. h,H,A and H+ = ++ two CP-even neutral Higgs : h and H with mixing angle αdefined in (Hu0,Hd0) basis. a CP-odd neutral Higgs : A a charged Higgs : H+ NG-boson : Eaten ↓ by Z-boson

  20. The ratios of the h couplings to hSM • rVVh= sin(β-α), rtth=rcch= rbbh= rττh= rμμh= rggh= rγγh= top bottom : bottom contirib. is significant when tan β ~ 10 W top bottom

  21. XC : Cross section Ratios to hSM • XC = = Rh=0.58|rbbh|2+0.06|rττh|2+0.24|rVVh|2+0.09|rggh|2+0.03|rcch|2 ↙ Γ h,tot / ΓhSM, tot Diphoton cross sections relative to hSM is sharply enhanced and reach maximum 3 at α = 0 . • bb, ττstrongly suppressed at α= 0 . • ΓγγEnhamcement by Indirect • mechanism • ( reduction of total width)

  22. ττ suppression • | rττh|= | | << 1 •  |α|<< for moderate value of tanβ >5 • αmust be flavor-tuned to be close to zero in order to getγγenhancement. Flavor-Tuned (FT) Higgs boson. h = Hu0 cf. Different from decoupling limit : α = β - π/2 . α= - 1/tanβ　　→　rττh= = 1

  23. FT model with α＝０ and 0.06 Γh, tot = 1.5 MeV : FT model Higgs(α=0) ΓhSM, tot = 4.07 MeV  Diphoton enhancement is explained by the reduction of total width. Tevatron bb: less than 3 sigma significance

  24. No hbb and No hττ 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 GeV4.6 – 4.7 fb−1 at 7 TeV, 2011. No significant excess of events above the background. ATLAS No hττ arXiv:1206.5971[hep-ex]. CMS No hττarXiv:1202.4083[hep-ex]. Consistent with our picture. What today?

  25. Flavor tuning of the mixing angle α in MSSM • Squared mass matrix in the CP-even neutral Higgs in (Hu0, Hd0) basis . • MH2= • Large tanβlimit •  - ε + Loop12 • Loop12 = ] Xt = At – μ cotβ ≈ At μ ：soft Higgs mass term High Higgs mass 125 GeV requires nearly “maximal mixing” condition Xt = -

  26. 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 =MZ2c2β2+ t = ln mt1 mt2/mt2 , tmax.min=ln Mmax,min2/mt2 Mmax,min2= max,min{ ML2,MR2 } X~t ≈ 2 mh2 takes Maximum at |Xt|= called maximal mixing condition

  27. 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.

  28. MH122 = 0 • Requires a very severe constraint on pseudoscalar mass mA. • mH2 = mA2 + MZ2 s2β2 • mH+2 = mA2 + MW2 • μ=MSUSY , Xt = -2MSUSY case • tan βmA mHmH+ 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.

  29. LHC ggA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.

  30. Cross section Ratio XC of H, A VτVbgτgγgWgZVγ 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 gτis sensitive to tanβ proportional to (tanβ)2 Discovery of H,A by this channel  tanβ determined at the same time.

  31. Decay Branching Fraction of H,A • bb ττggγγ 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 τνandcs

  32. tH+ b • The light H+ can be probed by tH+ b • L = H- • BF(tHb) is constrained experimentally.

  33. BF(tHb ) < 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).

  34. 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 radiativecorrections 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.

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