Higgs and Precision Electroweak Data

Transcription

1 Higgs and Precision Electroweak Data Brian Batell University of Chicago work in progress with Stefania Gori and Lian-Tao Wang MCTP Spring Symposium on Higgs Boson Physics April 16-20, 2012

2 Higgs Signal strength ATLAS Preliminary Best fit -2 ln (µ) < 1 H -1 Ldt = 4.9 fb s = 7 TeV m H [GeV] m H = 125 GeV Combined (68%) Single channel CMS Preliminary s = 7 TeV -1 L = fb H bb H H H WW H ZZ Best fit / SM

3 Rates e.g. most recent phenomenological fit: Giardino, Kannike, Raidal, Strumia,1203:4254 Rate SM rate m h 125 GeV Atlas CMS CDF D0 CMS Atlas CMS CDF D0 Atlas CMS Atlas CMS CDF D0 bbv bbv bbv WWjj WW WW WW ZZ ZZ ΓΓ ΓΓ ΓΓ ΓΓ pt Atlas CMS Atlas CMS ΓΓ jj ΤΤ ΤΤ 1. SM gives a good fit to data 0 Global χ 2 =16 for 15 d.o.f. 1 6 : m h 125 GeV 2. Best fit obtained for free hgg and hγγ couplings ,95 CL Global χ for 17 d.o.f. BR h ΓΓ SM 3 2 SM top partner O(1) enhancement in γγ channel! 1 SM BR h gg SM

4 Precision Electroweak Data Measurement Fit O meas O fit / meas (5) had (m Z ) ± m Z [GeV] ± Z [GeV] ± had [nb] ± R l ± A 0,l fb ± A l (P ) ± R b ± R c ± A 0,b fb ± A 0,c fb ± A b ± A c ± A l (SLD) ± sin 2 lept eff (Q fb ) ± m W [GeV] ± W [GeV] ± m t [GeV] ± July

5 A b FB from PDG 2.6σ After all, and go all the time! But... if A b FB A b FB,exp = ± , A b FB,SM = ± σ m h = GeV A puzzle? deviation for deviation for 2 3σ m h free in fit discrepancies come attributed to experimental error, or statistical fluctuation, electroweak fit prefers a very light Higgs, in tension with LEP bound Chanowitz 01 sin A l (LEP) A l (SLD) 2 lept eff (Q ) FB 0,c A FB 0,b A FB A c (5) had 0 had 0 Rlep 0,l A FB 0 Rc 0 Rb (M M Z Z A b 2 Z ) M W W m c m b m t G fitter SM AUG 11 M H [GeV] from GFitter group

6 Can the A b FB anomaly and Higgs rates be due to same underlying new physics? I will tell you two stories: 1. New physics alters A b FB (measurement correct) 2. Throw out A b FB (experimental error or statistical fluctuation) Electroweak data suggest NP for 125 GeV Higgs

7 1. New physics alters A b FB

8 A b FB ingredients Consider the process Forward, backward cross sections: Polarized cross sections: Forward-backward asymmetry: e + e γ,z, b b σ F,B = ±1 0 dσ dcos θ dcos θ σ LL σ(e + L e L b L b L ), etc. A FB = σ F σ B σ F + σ B = 3 4 σ LL + σ RR σ LR σ RL σ LL + σ RR + σ LR + σ RL On Z-pole: σ LL g Leg Lb m Z Γ Z, etc. A FB = 3 4 g 2 Le g2 Re g 2 Le + g2 Re g 2 Lb g2 Rb g 2 Lb + g2 Rb

9 Modify Zb R br coupling Haber, Logan 99 Choudhury, Tait, Wagner 01 L = g c w bγ µ (g Lb P L + g Rb P R ) b g Lb = s2 w 0.43 g Rb = 1 3 s2 w Goal: shift A b FB without affecting R b A FB = 3 4 g 2 Le g2 Re g 2 Le + g2 Re g 2 Lb g2 Rb g 2 Lb + g2 Rb R b Γ(Z b b) Γ(Z hadrons) g2 Lb + g2 Rb q [g2 Lq + g2 Rq ] Z-pole data allows 4 solutions in (δg Lb, δg Rb ), off-peak data for A b FB eliminate 2 possible solutions Data prefers a bigger shift in δg Rb, smaller shift in δg Lb

10 Fit: 2 solutions Kumar, Shepherd, Tait, Vega-Morales 10 L δg L δg δg R δg R Large negative δg b R solution Small positive δg b R solution δg Lb δg Rb 0.17 δg Lb δg Rb 0.02

11 Beautiful Mirrors Choudhury, Tait, Wagner 01 Basic idea: Mix new vector-like quark with bottom quark L b L B L M 11 M 12 M 21 M 22 b R B R +h.c. Diagonalize mass matrix via rotations of Z boson interactions: Shifts in Z bb couplings: δg Lb = t 3L L g c w Z µ ij b i(l,r), with angles bi γ µ (L ij P L + R ij P R )b j s 2 L, δg Rb = t 3R s 2 R, θ L,R Singles out 3 vector-like representations: Ψ L,R (3, 2, 1/6), (3, 2, 5/6), (3, 3, 2/3)

12 B X Focus on Ψ (3, 2, 5/6) t B 3R = 1 2 δg Rb = 1 2 s2 R =0.02 sin θ R 0.2 Consider EFT with general Higgs couplings: L y 1 QHbR y 2 ΨL H b R M Ψ L Ψ R +h.c. a H 2 Λ Ψ L Ψ R b H 2 Λ 2 bl Y 1 + bv 3 BL 2 0 2Λ 2 Y 2 + cv3 2 M + av2 2Λ 2 2Λ QHb R c H 2 Λ 2 Ψ L H b R h Y1 v + 3bv Λ 2 Y 2 v + 3cv2 2 av 2Λ 2 Λ +h.c. br B R +h.c. Diagonalize mass matrix via rotations...

13 Higgs physics see also Wagner, Morrissey 03 for (3, 2, 1/6) L hqq ξ hbb m b v h bb ξ hbb m B v h BB ξ hxx m X v h XX ξ hbb c 2 R + bv3 2mb Λ cs Rv 3 2 2mB Λ 2 ξ hbb s 2 R + av2 m B Λ + cs Rv 3 2mB Λ 2 ξ hxx = av2 m X Λ To enhance γγ rate: Suppress h b b partial width: ξ hbb < 1 Heavy quarks interfere constructively with SM amplitude: h γγ ξ hbb, ξ hxx < 0

14 a = 1, b= 0.01, c=0,m B = 600 GeV γγ VV gg bb Br h SM Renormalizable model (a = b = c = 0) Enhancement in γγ 1000 Suppression in gluon fusion Acceptable suppression in b b

15 Direct constraints on mirror quarks see also Kumar, Shepherd, Tait, Vega-Morales 10 B bz B tw B bh ATLAS, CMS, 1204:1088 (3l or 2SSl+b-jet) _ 400 GeV 611 GeV _ X bw CMS, PAS-EXO (lepton + jets) 560 GeV Precise bounds depend on branching ratios (in progress)

16 2. Throw out A b FB (experimental error or statistical fluctuation)

17 0.4 without A b FB S T fit 0.2 without A b FB T 0.0 with A b FB A b FB (A b FB) SM S T 0.2 SM S 68, 95% C.L. Electroweak data (w/o A b FB ) indicate a positive T, negative S

18 Simplest example: a second scalar doublet S (1, 2, 1/2) = 1 S + 2 (S R 0 + is I 0) V m 2 S 2 + λ 1 S 2 H 2 + λ 2 (H S)(S H)+[λ 3 (H S)(H S)+h.c.]+... hs + S coupling contribution to h γγ Custodial breaking S λ 2v 2 24πm 2 T v 4 192πs 2 wm 2 W m2 [(λ 2) 2 4(λ 3 ) 2 ]

19 Br(h γγ)/sm Λ m + < 105 GeV m S GeV Require light charged scalars for big enhancement

20 e.g. λ 1 = 2, λ 3 =0 S T preferred regions m Br(h γγ)/sm m Requires mass splittings ~ GeV

21 Additional constraints Vacuum stability (since we need negative λ 1 ) Perturbativity Direct constraints - depend on couplings to SM matter Other models give required shift in S, T Need nontrivial SU(2) L e.g. color octet (8, 2, 1/2) could suppress gluon fusion... (...in progress)

22 Summary Hints for Higgs at 125 GeV, as suggested by Precision Electroweak Data A b FB 2 3 σ : discrepancy - Is it a puzzle? Two approaches New physics directly influences for A b FB A b FB a statistical fluctuation or measurement error... invoke NP to improve EW data for 125 GeV Higgs The same new physics can simultaneously modify Higgs rates