Electroweak Data Fits & the Higgs Boson Mass. Robert Clare UC Riverside

Transcription

1 Electroweak Data Fits & the Higgs Boson Mass Robert Clare UC Riverside

2 Robert Clare UC Riverside LoopFest III Apr 1, Outline Electroweak corrections: definitions and strategies Experimental inputs Effective couplings as a test of the Standard Model The Electroweak global fit Higgs mass limits Non-SM? Future Prospects in precision EW measurements Conclusions

3 Robert Clare UC Riverside LoopFest III Apr 1, Electroweak Radiative Corrections Precision measurements: knowledge of Standard Model parameters through radiative corrections! = m 2 W m 2 Z cos2 " W = 1 =#! = 1 + $! m 2 W = sin 2 " W = 1 % m2 W m 2 Z =# sin 2 " eff = (1 + $&) sin 2 " W '( 2 sin 2 =# mw 2 " W G = '( F 2 sin 2 (1 + $r) " W G F ((0) =# ((mz 2 ) = ((0) 1 % $( with : $( = $( lept + $( top + $( (5) had!",!#,!r = f ( m 2 t, log(m H ),... ) t H H W b W Z/W Z/W Z/W Z/W

4 Robert Clare UC Riverside LoopFest III Apr 1, The LEP Heritage In total, for all 4 expts: about 16 M Z about W about 0 H

5 Effective Z couplings g V f = ( )! T (3) f " 2Q f sin 2 # eff g Af =! T (3) f A f = 2 g V f g Af g 2 V f + g2 Af A 0,f FB = A f A -0.5 ea f e c b Experimental Strategies FB asymmetries! A e A f " polarisation! A e and A " separately SLD (polarised beams)! A e (and A µ, A " ) sin 2! f eff Asymmetries! g V /g A Z partial decay widths! g 2 V + g2 A Robert Clare UC Riverside LoopFest III Apr 1,

6 Robert Clare UC Riverside LoopFest III Apr 1, Standard Model tests: leptonic couplings SM: m H = [114.1, 1000] GeV m t = ± 5.1 GeV m H Low m H favored g Vl m t lepton universality l + l! e + e! µ + µ! " + "! #$ 68% CL g Al

7 Robert Clare UC Riverside LoopFest III Apr 1, Effective couplings for quarks All heavy flavor results from LEP and SLD are averaged in a combined fit, taking into account interdependencies (like mixing) and correlated errors (like QCD)! 2 = 57.7/(105 " 14) ALEPH leptons DELPHI leptons L3 leptons OPAL leptons ALEPH inclusive DELPHI inclusive L3 jet-ch OPAL inclusive LEP Summer ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± _ 0,bb <A FB > = ± A 0,b FB = ± (tot sys ; common sys ) SM A 0,c FB = ± (tot sys ; common sys ) SM Some results are still preliminary _ 0,bb A FB

8 Robert Clare UC Riverside LoopFest III Apr 1, Quark couplings LEP + SLD, assuming lepton universality -0.3 Preliminary 0.22 Preliminary g Vb g Vc 0.2 SM SM % CL g Ab % CL g Ac

9 Quarks vs Leptons horizontal band: A b,a c (SLD); vertical band: A l (LEP+SLD); diagonal band : A 0,b FB, A0,c FB (LEP);!" m H # [114, 1000] 1 Preliminary 0.8 Preliminary 0.9 SM 0.7 SM A b A c A l A 0,b FB prefers high m H; A l prefers low m H Robert Clare UC Riverside LoopFest III Apr 1, A l

10 Robert Clare UC Riverside LoopFest III Apr 1, Standard model tests: sin 2! lept eff Final A 0,l fb ± A l (SLD) ± A l (P $ ) ± Q had fb ± Assuming lepton universality:! 2 /dof(lept.) = 1.6/2 (P = 44.0%)! 2 /dof(hadr.) = 0.06/2 (P = 96.8%)! 2 /dof(tot.) = 10.5/5 (P = 6.2%) Preliminary A 0,b fb ± A 0,c fb ± Average ± # 2 /d.o.f.: 10.5 / 5 hadrons vs leptons 3σ 2.9σ between 2 most precise quantities (A l and A 0,b FB ) m H %& (5) had = ± m Z = ± GeV m t = ± 5.1 GeV sin 2! lept eff = (1 " g Vl /g Al )/4

11 Top quark mass New DØ Run I top mass Use individual event probabilities instead of template Improves statistical error by factor 2.5 m t = ± 3.6 ± 3.9 GeV New CDF Run II top mass m t = !9.4 ± 7.1(l + jets) (Excluding New) m t = !16.9 ± 7.9(ll) M top!gev/c " 200. Not yet included... D! dilepton 168.4±12.8 Mass of the Top Quark D! lepton+jets OLD 173.3±7.8 Measurement M top!gev/c 2 " D! lepton+jets NEW 180.1±5.4 CDF di-l # 11.4 D! combined 172.1±7.1 (Excluding New) D! di-l # 12.8 CDF l+j # 7.3 CDF dilepton 167.4±11.4 D! l+j # 5.3 CDF lepton+jets 176.1±7.4 CDF all-j # 11.5 CDF All hadronic 186.0±11.5 CDF Combined 176.1±6.6 TEVATRON Run-I # 4.3 CDF/D! combined 174.3±5.1 NEW average: M top " 2 / dof = 2.6 / 4 m t = ± 4.3 GeV Robert Clare UC Riverside LoopFest III Apr 1,

12 Robert Clare UC Riverside LoopFest III Apr 1, W mass from Tevatron Run I results final CDF/DØ fit transverse mass (Jacobian) Systematics will come down with increased statistics: Energy scale controlled by Z events Hadronic recoil also constrained by Z events CDF expect with 250 pb ¹ with just channel m W = X ± 55 ± 80 MeV UA2 (1992) 80.36±0.37 CDF [Run-1] ±0.079 D! [Run-1] ±0.084 Hadron Colliders ± M W m W = ± GeV

13 Robert Clare UC Riverside LoopFest III Apr 1, W mass from LEP All results still preliminary! Still possible to improve; currently 4 quark final states have a low weight due to systematic errors from color reconnection and Bose-Einstein correlations. Studies on-going. Cross-check between qqqq and qqlν:!m W = +22 ± 43 MeV ALEPH ± DELPHI ± L ± OPAL ± M H!" (5) had = W # 2 / dof = 29.6 / 37 LEP ± ± linearly added to M W M t = 174.3±5.1 GeV m W = ± 0.029(stat) ± 0.031(sys) GeV

14 World average W mass and width W-Boson Mass W-Boson Width pp " -colliders ± LEP ± Average ± m W! 2 /DoF: 0.3 / 1 NuTeV ± LEP1/SLD ± LEP1/SLD/m t ± pp # -colliders ± LEP ± Average ± " 2 /DoF: 0.1 / 1 pp # indirect ± LEP1/SLD ± LEP1/SLD/m t ± ! W m W = ± GeV;! W = ± GeV Robert Clare UC Riverside LoopFest III Apr 1,

15 NuTeV results Paschos-Wolfenstein: CC and NC rates for! µ and! µ related to sin 2 " W ( ) R # = $! NC #$! NC $! CC #$ = % 2 1! 2 # sin2 " W CC NuTeV actually measures R! and R!. Discrepancy from R!. sin 2! W = ± (stat.) ± (sys.); " SM 3.0# No explanation forth-coming: Experimental effects such as PDFs, non-isoscalar contributions contamination Strange sea asymmetry (although the debate is ongoing...) Higher order EW corrections?! e ρ ,90,95,99% C.L. Contours SM Large m Higgs Discrepancy could be due to! " # / / / / CHARM II et al. LEP I Direct LEP I Lineshape NuTeV Large m top sin 2 θ W (on shell) Neutrino NC Rate/Prediction Robert Clare UC Riverside LoopFest III Apr 1,

16 Robert Clare UC Riverside LoopFest III Apr 1, Atomic parity violation Weak charge of the Cesium nucleus: Q W =!2 [C 1u (2Z + N) + ] C 1d (Z + 2N)] [ with C 1q = ] 2g Ae g V q, e.g. C 1u = " [! sin2 1 # W, C 1d = " 2! 2 3 sin2 # W Measure the amplitude of the parity-violating transition 6S-7S in Ce 133, possible due to the S-P mixing induced by neutral currents. Precise measurement performed by Wood, et al. (Science 275, 1759 (1997)). Transition amplitude + Cesium atomic structure QW(Cs), predicted by the SM At one time, difference between experiment and SM 2σ... an intriguing zigzag road of research... found many small corrections that cancel Updated estimate, included in global fit Kuchiev & Flambaum, hep-ph/ Q W (Cs) =!72.84 ± 0.29(exp) ± 0.36(th) Q W (Cs) SM =!72.90

17 Robert Clare UC Riverside LoopFest III Apr 1, Strategy of the global fit LEP: 0 0 m Z,',! h, R, Z l 0, l A FB G F P " Q FB m W, A l sin 2 # lept eff ' W SLD:A LEP+SLD: 0 l 0,b 0,c AFB R 0 b, R c, A FB,, A b, pp : m W, ' W, m t A c ZFITTER TOPAZ0 SM fit Output parameters: m %, m t,& s (m Z), sin 2 # W 2, mw... APV: QW (Cs) $ N (NuTeV) : ee 2 sin # W qq at low energy : (& (5) had New or updated in past year

18 The global electroweak fit Based on predictions from ZFITTER and TOPAZ0 Fit up to 20 parameters Output estimates for: m t, m H,! s (mz 2 ), "!(5) had, m Z Fit repeated with and without NuTeV, to evaluate its contribution... Z pole All but NuTeV All data m t ( GeV) ! ! !4.4 m H ( GeV) ! ! !38 " s (mz 2 ) ± ± ± m W ( GeV) ± ± ± sin 2 # lept eff ± ± ± sin 2 # W ± ± ± $ 2 /d.o.f. 14.7/ / /15 probab. (%) Slightly old numbers Robert Clare UC Riverside LoopFest III Apr 1,

19 Robert Clare UC Riverside LoopFest III Apr 1, The global electroweak fit Largest contributions to! 2 from A 0,b FB A l (from SLD) NuTeV A 0,b FB and A l pull in opposite directions (concerning effects on m H ) Measurement Fit O meas!o fit /" meas #$ (5) had (m Z ) ± m Z ± % Z ± " 0 had [nb] ± R l R l ± A fb A 0,l ± A l (P & ) ± R b R b ± R c R c ± A fb A 0,b ± A fb A 0,c ± A b A b ± A c A c ± A l (SLD) ± sin 2 ' lept eff (Q fb ) ± m W ± % W ± m t ± Slightly old numbers sin 2 ' W ((N) ± Q W (Cs) ±

20 Robert Clare UC Riverside LoopFest III Apr 1, The global fit: m W, m t, m H m W LEP1, SLD Data LEP2, pp # Data 68% CL!" m H Preliminary m t Good consistency between direct and indirect (Z pole) m W and m t values. Direct m W,m t prefer low Higgs mass (as does A l ) This should be moved over just a bit

21 Robert Clare UC Riverside LoopFest III Apr 1, The global fit: limits on the Higgs mass!" All data, with old world-average M top All data, with new world-average M top m H < 251 GeV Region excluded by direct searches Theory uncertainty Higgs Boson Mass [GeV/c 2 ] Blue band width is estimate of theoretical uncertainties coming from higher order effects Possibly overestimated as two-loop contributions to m W (Weiglein, et al.) might be partially canceled by similar contributions to Z partial widths and sin 2! lept eff (Finally an updated plot!)

22 Robert Clare UC Riverside LoopFest III Apr 1, Beyond the SM the MSSM In the SM, the Higgs mass is a free parameter, and m t and can be related to it. In the MSSM, the Higgs mass is no longer free. m H, m t, and m W depend on the SUSY parameters. Unfortunatly, they are free! m W m W LEP1, SLD Data LEP2, pp # Data 68% CL MSSM Light Susy!" Heavy Susy MSSM seems to be a bit more compatible with the data... MSSM: Heinemeyer, Weiglein, hep-ph/ m H Preliminary m t

23 Beyond the SM the MSSM SM: & 2 /d.o.f = 27.2/16 MSSM: & 2 /d.o.f = 16.4/12 CMSSM: & 2 /d.o.f = 23.2/ m t = GeV SM (m H = GeV) LEP: M Z! Z " had sin 2! eff experimental errors: LEP2/SLD/Tevatron LHC/LC GigaZ MSSM Heinemeyer, Weiglein M W SLC: R l l A FB R b R c b A FB c A FB M t sin 2 lept # eff M W (LEP) sin 2 # lept (A LR ) eff b $ X s % a µ SUSY de Boer & Sanders, hep-ph/ pulls=(data-theo)/error Robert Clare UC Riverside LoopFest III Apr 1,

24 Robert Clare UC Riverside LoopFest III Apr 1, Treading on thin ice... must m H be small? To accomodate a heavy Higgs, need a new theory which contributes either +ΔT or -ΔS (or both). Some Technicolor models contribute negative S (eg, Luty & Sundrum, hep-ph/ ) T 100 m h An appropriately chosen Z can move (S,T) in almost any direction, but must be light (< 2 TeV) m t topcolor seesaw (eg Dobrescu & Hill, PRL 81, 2634 (1998)) gives +ΔT S Peskin & Wells, PR D64 (2001) An additional generation of quarks and leptons (He, et al. PL B496, 195 (2000)) can generate +ΔT (also +ΔS, but that could currently be OK)...

25 Beyond the Current Experiments now Run IIA Run IIB Run IIB! LHC LC GigaZ " sin 2 # lept eff ($ 10 5 ) (6) 1.3 "m W [MeV] "m t "m H [MeV] O(2000) U.Baur, et al., Snowmass 2001, hep-ph/ Near future (Run II, LHC):!m W = 15 MeV!m t = 1.5 GeV!"# had = Far future (LC, GigaZ):!m W = 7 MeV!m t = 130 MeV!"# had = ! sin 2 $ lept eff = 1.3 % 10 &5 Robert Clare UC Riverside LoopFest III Apr 1,

26 Robert Clare UC Riverside LoopFest III Apr 1, Beyond the Current Experiments 6 4 Summer 2003 TEV-IIb LHC LC experimental errors 68% CL: LEP2/Tevatron (today) Tevatron/LHC LC+GigaZ MSSM light SUSY!" 2 2 M W M H = 113 GeV heavy SUSY Excluded Preliminary m H M H = 400 GeV SM Heinemeyer, Weiglein m t

27 Robert Clare UC Riverside LoopFest III Apr 1, Beyond the Current Experiments 6 Summer 2003 TEV-IIb 4!" 2 2 Excluded Preliminary m H

28 Robert Clare UC Riverside LoopFest III Apr 1, Beyond the Current Experiments 6 Summer 2003 LHC 4!" 2 2 Excluded Preliminary m H

29 Robert Clare UC Riverside LoopFest III Apr 1, Beyond the Current Experiments 6 Summer LC!" 2 2 Excluded Preliminary m H

30 Robert Clare UC Riverside LoopFest III Apr 1, Conclusions The Standard Model describes with unprecedented precision a huge amount of data The largest discrepancies are due to the NuTeV result and to FB ; interpreted as statistical fluctuations they are 3 σ Global fit: Future inputs: Final results from LEP-II: New measurements of m as well as sin 2! lept W,! W, m t eff from Tevatron Run II and LHC Far future Linear Collider and GigaZ? m H < 251 GeV m W,! W A 0,b What will we find?