News from the global electroweak fit

Transcription

1 News From The Global Electroweak Fit University of Hamburg for the Gfitter group Higgs Hunting LAL, August 1 st, 015 The Gfitter group: M. Baak (CERN), J. Cùth (Univ. of Mainz), J. Haller (Univ. Hamburg), A. Hoecker (CERN), R. K. (Univ. Hamburg), K. Mönig (DESY), T. Peiffer (Univ. Hamburg), M. Schott (Univ. of Mainz), J. Stelzer (Univ. of Michigan) 1

2 State of the Standard Model [GeV] M W % and 95% CL contours direct M W fit w/o M W fit w/o M W, sin fit w/o M W, sin and sin (θ f ) measurements eff, sin (θ f ) and Z widths measurements eff f (θ ) and M measurements eff H f (θ ), M and Z widths measurements eff H sin (θ f eff ) LEP+SLC ± 1σ M W world comb. ± 1σ G fitter SM Jul ' sin (θ l ) eff (see also talk by Tongguang Cheng)

3 Prediction of Top Quark Mass Top mass [GeV] Gfitter group, Nov 014 mt predictions from loop effects since 1990 official LEPEWWG fit since Measurements Tevatron Tevatron + LHC Results of the EW fit LEPEWWG Gfitter, incl. M H (searches or meas.) Year the fits have always been able to predict mt correctly! What precision is needed to see significant deviations between measurements and predictions? 3

4 Prediction of Higgs Mass Higgs mass [GeV] Measurements LHC Results of the EW fit Gfitter group, Nov % CL, PDG 68% CL, LEPEWWG 68% CL, Gfitter 68% CL, Gfitter (incl. direct searches) Year MH predictions from loop effects since the discovery of the top quark 1995 weaker constraints than for mt because of logarithmic dependence still, the fits have always predicted MH correctly! Again: what precision should we strive for? What are the major challenges? 4

5 Experimental Input M H [GeV] ( ) ± 0.4 LHC Fit is overconstrained all free parameters measured (αs(mz) unconstrained in fit) most input from e + e colliders - MZ : 10 5 but crucial input from hadron colliders: - mt : MH : MW : 10 4 remarkable precision (<1%) require precision calculations 5 M W [GeV] ± W [GeV].085 ± 0.04 M Z [GeV] ± Z [GeV].495 ± had [nb] ± R 0` ± 0.05 A 0,` FB ± A` (?) ± sin è (Q FB) 0.34 ± A c ± 0.07 A b 0.93 ± 0.00 A 0,c FB ± A 0,b FB ± Rc ± Rb ± ± m (5) c [GeV] had (M ± Z )( 4) 757 ± m b c [GeV] m b t [GeV] ± ± m t [GeV] ± ± Tev. LEP SLD SLD LEP low E Tev.+LHC

6 Calculations All observables calculated at -loop level MW : full EW one- and two-loop calculation of fermionic and bosonic contributions [M Awramik et al., PRD 69, (004), PRL 89, (00)] + 4-loop QCD correction [Chetyrkin et al., PRL 97, (006)] sin θ l eff : same order as MW, calculations for leptons and all quark flavours [M Awramik et al, PRL 93, (004), JHEP 11, 048 (006), Nucl. Phys. B813, 174 (009)] partial widths Γf : fermionic corrections in two-loop for all flavours (includes predictions for σ 0 had) [A. Freitas, JHEP04, 070 (014)] Radiator functions: QCD corrections at N 3 LO [Baikov et al., PRL 108, 003 (01)] fermionic ΓW : only one-loop EW corrections available, negligible impact on fit [Cho et al, JHEP 1111, 068 (011)] bosonic NEW all calculations: one- and two-loop QCD corrections and leading terms of higher order corrections 6

7 estimated using a geometric series (an = a r n ), example: similar results from scale variations reasonable estimates for all observables exception: mt! M exp = X i=1,...,n p i Theoretical Uncertainties 1 A [A. Hoang arxiv: , M. Mangano] q MC definition, relation to m pole unknown uncertainties from colour structure, hadronisation and m pole mt(mt) smaller 10 additional free parameters, Gaussian likelihood important missing higher order terms: _ q g q _ q t _ t b W B M exp = O(α α s )= O(α ) O(α) O(αα s) important 0.5 GeV new in fit O(α αs), O(ααs ), O(α bos) (in some cases), O(α 3 ), O(αs 5 ) (rad. functions) p1 pn 7

8 Theoretical uncertainty on mt [GeV] M W % CL contour for fit w/o m W, sin l (θeff δ m theo t δ theo m t δ theo m t δ theo m t ) and Z widths measurements = 1.5 GeV = 1.0 GeV = 0.5 GeV = 0.0 GeV default sin (θ l eff ) LEP+SLC ± 1σ m W world comb. ± 1σ G fitter SM impact of variation in δtheo mt between 0 and 1.5 GeV better assessment of uncertainty on mt important for the fit uncertainty of 0.5 GeV small impact on result sin Jul '14 l (θ ) eff 8

9 Future Improvements Parameter Present LHC ILC/GigaZ M H [GeV] 0. < 0.1 < 0.1 M W [MeV] M Z [MeV] m t [GeV] sin è [10 5 ] had 5 (M Z ) [10 5 ] Rl 0 [10 3 ] theoretical uncertainties reduced by a factor of 4 (esp. MW and sin θ l eff) implies three-loop calculations! exception: δtheo mt (LHC) = 0.5 GeV (factor ) central values of input measurements adjusted to MH = 15 GeV ± LHC = LHC with 300 fb 1 ILC/GigaZ = future e + e collider, option to run on Z-pole (w polarized beams) WW threshold tt threshold scan δa 0,f LR : low energy data, better αs high statistics on Z-pole apple V ( = 3TeV) direct measurement of BRs [Baak et al, arxiv: ] 9 Fits of EWPO in the SM

10 SM Fit Results black: direct measurement (data) orange: full fit light-blue: fit excluding input from row M H M W Γ W [Gfitter, arxiv: ] Global EW fit Indirect determination Measurement goodness of fit, p-value: χ min= 17.8 Prob(χ min, 14) = 1% Pseudo experiments: 1 ± (theo)% χ min(γi in 1-loop) = 18.0 χ min(no theory uncertainties) = 18. no individual value exceeds 3σ largest deviations in b-sector: A 0,b FB with.5σ largest contribution to χ small pulls for MH, MZ input accuracies exceed fit requirements A l (LEP) A l (SLD) lept sin Θ eff (Q ) FB α s (M (5) α had 0 σ had 0 Rlep 0,l A FB 0,c A FB 0,b A FB 0 Rc 0 Rb m t (M M Z Γ Z A c A b Z Z ) ) O) / (O indirect σ tot 10

11 Present Results: Higgs Determination of MH grey band: fit without MH measurement MH = GeV consistent with measurement at 1.3σ blue line: full SM fit Impact of most sensitive observables determination of MH, removing all sensitive observables except the given one known tension (3σ) between Al(SLD), A 0,b FB, and MW clearly visible A l (LEP) A l (SLD) 0,b A FB M W Fit w/o M H LHC average G fitter SM Jul ' M H [GeV] ± Fits of EWPO in the SM

12 Future: Higgs Mass MH meas = 15 GeV 15 GeV 94 GeV Logarithmic dependency on MH cannot compete with direct MH meas. no theory uncertainty: MH = 15 ± 7 GeV future theory uncertainty (Rfit): present day theory uncertainty: MH = GeV MH = GeV If EWPO central values unchanged (94 GeV), ~5σ discrepancy with measured Higgs mass Fits of EWPO in the SM

13 present theory uncertainty Future: Higgs Mass present theory uncertainty MH meas = 15 GeV 15 GeV 94 GeV Logarithmic dependency on MH cannot compete with direct MH meas. no theory uncertainty: MH = 15 ± 7 GeV future theory uncertainty (Rfit): present day theory uncertainty: MH = GeV MH = GeV If EWPO central values unchanged (94 GeV), ~5σ discrepancy with measured Higgs mass compromised by present theory uncertainty! Fits of EWPO in the SM

14 Indirect determination of W mass also shown: SM fit with minimal input: MZ, GF, Δαhad (5) (MZ), αs(mz), MH, and fermion masses good consistency MH measurement allows for precise constraint on MW agreement at 1.4σ fit result for indirect determination of MW (full fit w/o MW): M W = ± mt ± theo m t ± MZ ± had ± S ± MH ± theo M W GeV, = ± tot GeV. more precise than direct measurement (15 MeV) 13

15 Indirect determination of W mass also shown: SM fit with minimal input: MZ, GF, Δαhad (5) (MZ), αs(mz), MH, and fermion masses good consistency MH measurement allows for precise constraint on MW agreement at 1.4σ Δχ SM fit w/o M W measurement SM fit w/o M W and M H measurement SM fit with minimal input world average [arxiv: ] fit result for indirect determination of MW (full fit w/o MW): M W Rfit M W [GeV] 3σ σ 1σ M W = ± mt ± theo m t ± MZ ± had ± S ± MH ± theo M W GeV, = ± tot GeV. ( δmt (1 GeV): ±9 MeV, Rfit: ±13 MeV ) more precise than direct measurement (15 MeV) 13

16 Future: MW LHC-300 Scenario moderate improvement (~30%) of indirect constraint theoretical uncertainties already important ILC Scenario improvement of factor 3 possible, similar to direct measurement Fit Results: χ M W =1.7 MZ 0.1 mt 1. sin f eff Present SM fit Prospects for LHC Prospects for ILC/GigaZ Direct measurement (present/lhc/ilc) had 0.3 s MeV G fitter SM M W Jul 14 [GeV] 5σ 4σ 3σ σ 1σ M W =1.3 theo 1.9 exp MeV =.3 tot MeV Measurement uncertainty for ILC: 5 MeV 14 Fits of EWPO in the SM

17 Indirect determination of mt determination of mt from Z-pole data (fully obtained from rad. corrections ~mt ) alternative to direct measurements MH allows for significantly more precise determination of mt m t = ±.3 MW sin ± ± 0.6 f s ± ± 0.5 had ± 0.4 MZ GeV eff = ±.4 exp ± 0.5 theo GeV, similar precision as determination from σtt, good agreement dominated by experimental precision 15

18 Future: Top Quark Mass LHC-300 Scenario improvement due to improved precision on MW χ ILC Scenario Comparable precision due to MW and sin θ l eff measurements (MW : δmt = 1 GeV sin θ l eff : δmt = 0.9 GeV) Fit Results: m t =0.6 MW 0.5 MZ 0.3 sin f eff Present SM fit Prospect for LHC Prospect for ILC/GigaZ kin m t world average [arxiv: ] G fitter SM had 0. s GeV m t Jul '15 [GeV] 3σ σ 1σ m t =0. theo 0.7 exp GeV = 0.8 tot GeV similar precision as present world average of mt kin from hadron colliders still dominated by experimental precision 16 The global electroweak fit

19 Present: Effective Weak Mixing Angle all measurements directly sensitive to sin θ l eff removed from fit (asymmetries, partial widths) good agreement with minimal input MH measurement allows for precise constraint χ SM fit with M H measurement SM fit w/o M H measurement SM fit with minimal input fit result for indirect determination of sin θ l eff : LEP/SLD average [hep-ex/ ] G fitter SM Jul '14 sin (θ l ) eff 3σ σ 1σ sin è = ± mt ± theo m t ± MZ ± had ± S ± MH ± theo sin f, e = ± tot, more precise than determination from LEP/SLD ( ) 17 Fits of EWPO in the SM

20 Future: Effective Weak Mixing Angle LHC-300 Scenario large improvement of indirect constraint compromised by today s theoretical uncertainties ILC Scenario Indirect constraint and direct measurement comparable precision Fit Results: χ Present SM fit Prospects for LHC Prospects for ILC/GigaZ Direct measurement (present/lhc/ilc) G fitter SM 1σ Jul '14 sin (θ l ) eff 5σ 4σ 3σ σ sin f e =(1.7 M W 1. MZ 0.1 mt 1.5 had 0.1 s ) 10 5 sin f e =(1.0 theo.0 exp ) 10 5 =(.3 tot ) 10 5 Measurement uncertainty for ILC: Fits of EWPO in the SM

21 ll e theory boson and approach, all fermion wherecouplings higher-order are modified modifiersin tothe a phenomenologat F,respectively,whereapple tree-level tocoupling the SM Higgs V = apple F boson = same way, scaled by the constants apple V and Constraints 1 for couplings. the SM. InThis onebenchmark popular from model model EWPO uses the explicit assumpon that various benchmark no other new models physics [57 plings are modified in the sameisway, present, scalede.g., by there constants are no appleadditional V and loops in the production r modifiers decay of to a Higgs phenomenologuplings. apple F = 1 for the SM. This boson, benchmark and no invisible model uses Higgs thedecays explicitand assumpics is present, consider e.g., specific there are model Ref. no[65]. additional in κ parametrisation: loops in the production undetectable contributions to its κv κv ecay width. In one For popular details see model caled by the constants apple V and he and combined no invisible analysis Higgs of decays electroweak and undetectable precision data contributions and Higgs signal-strength to its odel uses scaling the explicit of Higgs-vector assumptional loops Higgs-fermion byin several the production groups couplings [5, 9, 66 71]. (κf), with The main no invisible/undetectable e ect of this model on thewidths electroweak preci- boson (κv) and measurements has Ref. een studied [65]. on detectable troweak observables precision contributions from datathe and tomodified Higgs its signal-strength Higgs couplingmeasurements to gauge bosons, hasand manifests itself through s op [5, diagrams 9, main 66 71]. effect involving The main on EWPD the e ect longitudinal ofdue this model to degrees modified on the ofelectroweak freedom Higgs coupling preciodified Higgs coupling gauge bosons, and manifests itself through parameters [66], these bosons. to gauge The bosons corrections (κv) to e Z and [Espinosa W boson et al. propagators arxiv: , can be Falkowski expressed et al. inarxiv: ], terms of the S, Tetc nal-strength measurements has longitudinal 80.5 κ private LHC average ± 1σ S = 1 degrees of freedom of these bosons. The corrections to model on the electroweak 95% CL contours V λ w/o M W and κ V measurement Λ = 1 (1 precis, and manifests itself through MH, =, (5) apple V )ln 3 ors can be expressed in terms of MH, the T = S, T parameters 16 cos (1[66], apple è V )ln 1-κ λ = 10 TeV q 1 apple ese V bosons. The corrections 3 to λ = 5 TeV S, T, parameters T = [66], λ = 1 TeV nd H U = 0. The 16 cut-o cos (1 apple è V )ln scale represents M, =, (5) H the mass q 1 scale apple of the new states that unitarise lonitudinal gauge-boson scattering, as required in this model. Note that the less apple V deviates from 80.4 V ne, e, the represents higher = the thescale mass, ofscale new (5) of physics. the newmost states BSMthat models with additional Higgs bosons giving M W unitarise loning, as required into V world comb. ± 1σ H ositive corrections q 1 apple this themodel. W mass Note predict that values the80.35 less ofappleapple VV deviates smaller than from 1. Here the nominator is aried ew physics. betweenmost 1 andbsm 10 TeV, models andwith is nominally additional fixed Higgs to bosons 3 TeV (4 v). giving new states that unitarise lonthat the less apple V deviates from for, together with the allowed 80.3 igure mass correlation 8 predict (top) shows values between the of predictions apple V smaller κv and for than S MW and 1. Here T, profiled the nominator 68% and over 95% CL applecontours V and is, direct M W and κ V measurements gions and is for nominally S and T fixed from to the 3 TeV current (4 v). electroweak fit. The length of the predicted linegcovers fitter SM additional slightly Higgssmaller bosons giving values of MW a ariation in apple V between [0, ], the width covers80.5 ictions an 1. Here for preferred Sthe andnominator T, profiled over is apple V and, together the 0.8 variation with 0.85 thein allowed ev). κ he current bottom electroweak panel of Fig. fit. 8 The shows length apple V V and of the apple F as predicted obtained line from covers a private a combination of ATLAS, the CMS width results covers using the variation publicly in available. nd, together with the allowed information 19 on the News measured from the global electroweak Higgs signal fit strength M W Jul '14

22 Higgs Coupling Results Higgs coupling measurements: κv = 0.99 ± 0.08 κf = 1.01 ± 0.17 κf κ F Higgs Measurements 68% and 95% CL fit contours Standard Model prediction EW-fit + Higgs Measurements 68% and 95% CL fit contours [λ = 3 TeV] Fit minimum Combined result: κv = 1.03 ± 0.0 (λ = 3 TeV) implies NP-scale of Λ 13 TeV preliminary B G fitter SM some dependency for κv in central value [ ] and error [ ] on cut-off scale λ [1-10 TeV] EW fit sofar more precise result for κv than current LHC experiments EW fit has positive deviation of κv from many BSM models: κv < 1 Mar '15 κv κ V 0 The global electroweak fit

23 Prospects of EW Fit M W % and 95% CL contours w/o M W and κ V measurement Present SM fit Prospect for LHC Prospect for ILC/GigaZ κ V private LHC average Λ = 4πv 1-κ V ± 1σ 80.4 Present measurement ILC precision LHC precision M W world comb. ± 1σ κ V competitive results between EW fit and Higgs coupling measurements! precision of about 1% ILC/GigaZ offers fantastic possibilities to test the SM and constrain NP 1 The global electroweak fit

24 Summary of Indirect Predictions Experimental input [±1 exp ] Indirect determination [±1 exp, ±1 theo ] Parameter Present LHC ILC/GigaZ Present LHC ILC/GigaZ M H [GeV] 0. < 0.1 < , , , M W [MeV] , , , 1.3 M Z [MeV] , 4 7.0, 1.4.5, 1.0 m t [GeV] , , , 0. sin è [10 5 ] , 4.9.8, 1.1.0, had (M Z ) [10 5 ] , 13 36, 6 5.6, 3.0 R 0 l [10 3 ] S (M Z ) [10 4 ] 40, 10 39, 7 6.4, 6.9 S U= , , , T U= , , , apple V ( = 3TeV) Fits of EWPO in the SM

25 Summary of Indirect Predictions Experimental input [±1 exp ] Indirect determination [±1 exp, ±1 theo ] Parameter Present LHC ILC/GigaZ Present LHC ILC/GigaZ M H [GeV] 0. < 0.1 < , , , M W [MeV] , , , 1.3 M Z [MeV] , 4 7.0, 1.4.5, 1.0 m t [GeV] , , , 0. sin è [10 5 ] , 4.9.8, 1.1.0, had (M Z ) [10 5 ] , 13 36, 6 5.6, 3.0 R 0 l [10 3 ] S (M Z ) [10 4 ] 40, 10 39, 7 6.4, 6.9 S U= , , , T U= , , , apple V ( = 3TeV) Theory uncertainty needs to be reduced if we want to achieve the ultimate precision with the LHC! Future e + e collider: fantastic possibilities for consistency tests of the SM on loop level and NP constraints Fits of EWPO in the SM

26 Summary Uncertainties on MW Today δmeas = 15 MeV δfit = 8 MeV δfit theo = 5 MeV LHC-300 δmeas = 8 MeV δfit = 6 MeV δfit theo = MeV ILC/GigaZ δmeas = 5 MeV δfit = MeV δfit theo = 1 MeV δmz δmtop δsin (θ l eff) δδαhad δαs 1,6,5 5,1,5,6 0,8 4,3 4,8,5 0,3 0,6 3,5 1, 0,1 1,7 Impact of individual uncertainties on δmw in fit (numbers in MeV) Improved theoretical precision needed already for the LHC-300! 3 The global electroweak fit

27 Additional Material 4

28 Two Higgs Doublet Models extend the scalar sector by another doublet studies of Z Type-1 and Type- HDMs difference in the coupling to down-type quarks Type- related to MSSM, but less constrained Preliminary (see talk by M. Beckingham) Higgs Type I and Type II C V h sin( ) H cos( ) A 0 constraints derived from EWPD using S,T,U formalism lightest scalar Mh = 15.1 GeV weak constraints on masses, since tanβ and cos(β-α) are unconstrained 5

29 HDM and H Coupling Measurements coupling measurements place important constraints on HDMs predictions of BRs using HDMC [D. Eriksson et al., CPC 181, 189 (010)] 7 additional, unconstraint parameters (4 masses, angles, soft breaking scale): importance sampling with MultiNest [F. Feroz et al., arxiv: ] tan β MH± = 50 GeV tan β MH± = 50 GeV Type-1 Type- Preliminary Preliminary cos(β α) cos(β α) additional constraints from flavour data B Xs γ: tanβ > 1 Bs µµ : constraints depending on MH and MH± 6

30 Global Fit to HDM of Type- Preliminary for given MH± tight constraints from H coupling measurements and EWPD expect improvement from direct searches at the LHC 7