LEP Higgs Search Results. Chris Tully Weak Interactions and Neutrinos Workshop January 21-26, 2002

Transcription

1 LEP Higgs Sarch Rsults Chris Tully Wak Intractions and Nutrinos Workshop January 1-6, 00

2 Viw of LEP Exprimnts

3 Spontanous Symmtry Braking Higgs Fild 1-complx doublt Hyprcharg(Y) U(1) Y Symmtry Lft-Handd Isospin(T) SU() L Symmtry 0 0 C - 0 W W W B µ Two Primordial Gaug Intractions: i igt i W B Y g i µ µ µ µ 0 0 = = Y T 0 1 = = Y T 1 1 = = Y T T Y

4 Proprtis of th Physical Vacuum Slf-Intracting Effctiv Potntial: T Y 3 ( Q = = 1 T = 3 V () 1 Y ) = 0 V Elctric Charg(Q) U(1) EM Symmtry Q = 0 A µ 4 ( ) = µ λ Λ λ( Λ) (tr-lvl) ngativ t (top-loop) ±, Im{ } W, 0 ± L Z L R{ 0 } H missing link

5 T = T = 1 1 Is th Z just a massiv W 0? If isospin (T) wr an unbrokn symmtry, L R allowd T = 1 W 0 T T = = 0 0 R L not allowd T = 1 W 0 Th masurmnt of R L Z givs us sin θw

6 LEP Luminosity Higgs Sarch LEP Luminosity Expctd # s of Higgs Evnts Physics Days/Yars

7 Pushing LEP to its Limit

8 Standard Modl Higgs Production Higgsstrahlung Diagram GV GV Fusion Diagrams

9 Physical Sarch Channls Production Frmions Z Z qq Z WW Z ZZ vv τ, v τ Higgs Dcay m H =115 GV v b b (74%) gg (7%) cc(3%) H or µ µ H, 4-Jt 54% E-Missing 3% Lptons (µ) 5% Taus(ττH) 3% τ τ (7%) Taus(qqττ) 5% 10% missing

10 Standard Modl Procsss at LEP - qq Two-Photon Intraction - - qq( γ) - qq Full Enrgy s / s > 0.85 ( ) W W q qq q - ZZ qqqq - HZ mh = 114 bb qq GV

11 Combining Sarch Data Rbinning Procdur 4 Exprimnts 4 Channls 15 Bam Enrgis =40 Analyss Equal S/B Ratio Equal Snsitivity LEP tratd as a singl sarch analysis

12 Sarch Channl Missing Enrgy Lptons (µ) Sarch Channl Analyss Avrag Signal/Background at m H =115.6 GV 4-Jt Exp. Alph Dlphi L3 Opal Alph Dlphi L3 Opal Alph Dlphi L3 Opal Expctd Numbr of Evnts Notabl Analysis Variation

13 LEP Higgs Data at m H =115.6 GV Slction Data Background Signal Background All Evnts s/b> s/b> s/b>

14 Candidat Evolutions in Log(s/b) 3 ALEPH 4-Jt Evnts OPAL 4-Jt Evnt 1 L3 Missing Enrgy ALEPH Lpton() Evnt Paks occur at Rconstructd masss Widths com from Mass rsolutions

15 ALEPH 4-Jt Channl

16 Background from Doubl Gluon Radiation To mimic Z qq dcay, gluons must b: a) back-to-back b) sparatd from th quark jts, and ach hav c) 45 GV of nrgy Cross sction is rasonably wll known in prturbativ QCD (known to 0%)

17 Sid Viw of Hνν Candidat m H = 115 GV s = 06.4 GV

18 Composition of Background Estimat for Hνν Candidat 0% 80% - ZZ νν bb Dijt Mass 91 GV but masurd to b 115 GV (Masurmnt Tails) Two b-jts - bb( γγ) Fraction of Full Enrgy Evnts Extrmly Small (Dijt Mass 06 GV but masurd to b 115 GV) Dominantly Doubl Radiativ Rturn Rar Procss that Mimics th Signal (Production Tails)

19 Background from Doubl Radiativ Rturn To mimic Z νν dcay, photons must b: a) back-to-back b) undtctd (down bam pip), and ach with c) 45 GV of nrgy Additional photon lins imply small cross sctions (known to 15%)

20 Jt Masurmnts Z Pak Calibration Data in Yar 000 Jt Rsolution 13% at θ=45º Jt Enrgy Sum = 91 GV No Evidnc for Larg Enrgy Loss

21 Visualizing Sarch Snsitivity Trat ach bin i as a Poisson Counting Exprimnt bi si Expctd Background Expctd Signal ni Obsrvd Numbr of Evnts Q xponntially incrasing n dcrasing i = s i b (SignalBackground) i s = i ln(q) si ni ln 1 i bi n = i b i } wight (Background Only)

22 Scanning for a Higgs Boson Mass Masur mdian sparation of hypothss 68% 95% Compar with widths of distributions Scan vrsus Mass

23 Combind Standard Modl Rsults m H =115.6 GV Data Excss Compatibl with: m H = GV Prliminary Data final combination xpctd in Fbruary

24 Is it Background Only? by Exprimnt by Channl

25 Is it Signal Background? by Exprimnt by Channl

26 Mass Rsolution by Channl

27 Mass Rsolution in H WW * Higgsstrahlung ZH ZWW * Dcay Mods Z qq * WW 4 Jt * WW qq lν Z νν WW * 4 Jt

28 m H =115 GV Slf-Coupling λ λ is ngativ for m t =175 GV at 1000 TV What can b don? λ( Λ) positiv Isidori, Ridolfi, Strumia hp-ph/ Massiv scalar or vctor particls

29 Frmion Masss in a 1-doublt Modl = = 0 0 c C 1-doublt Modl: ( ) R L d d d d u G = L Down-typ mass ( ) R c L u u u d u G = L Up-typ mass = 0 1 v c G v m u u = = v 0 1 v G m d d = Sam v

30 Frmion Masss in a -doublt Modl Down-typ mass m d = G dv 1 v v = v 1 tan β = v v 1 Up-typ mass m u = Guv 8 dgrs of frdom 3 longitudinal polarizations (W L±,Z L ) Elctrowak Enrgy Scal m top /m bottom? lavs 5 Higgs bosons: h, H, A, H ±

31 Production of Higgs Bosons in th Minimal Supr Symmtric Modl

32 Scanning for th MSSM (m h,tan β) Exclusion plan (m h -max) } Excludd past ZZ for qual mass ha production Lightst h xcss at GV Excludd rgion of tan β Small rgion of allowd low tan β valus

33 Higgs Qust Frmilab (Chicago, USA) LEP (Gnva, Switzrland) LEP Dismantling Novmbr yars Tvatron Run II In progrss Startup of LHC 006 or latr

34 Indirct Higgs Sarch Hinmyr and Wiglin hp-ph/7307 Standard Modl Prcision Elctrowak Data } Shrink th uncrtaintis on M W and M top } Low mass prfrnc for th Higgs boson