Non-Standard Higgs Decays

Transcription

1 Non-Standard Higgs Decays David Kaplan Johns Hopkins University in collaboration with M McEvoy, K Rehermann, and M Schwartz

2 Standard Higgs Decays

3 Standard Higgs Decays 1 _ bb 140 GeV WW BR for SM Higgs ! +! " cc _ gg ZZ tt - ## Z# Higgs Mass (GeV)

4 Higgs mass fit GeV!" 2 < 144 GeV (95% C.L.) Theory uncertainty!# had =!# (5) ± ± incl. low Q 2 data m Limit = 144 GeV LEP II Bound: > GeV 0 Excluded m H [GeV] Preliminary

5 Higgs mass fit GeV!" 2 < 144 GeV (95% C.L.) Theory uncertainty!# had =!# (5) ± ± incl. low Q 2 data m Limit = 144 GeV LEP II Bound: > GeV 0 Excluded m H [GeV] Preliminary

6 Sensitivity to m h Discrepancy in observables sensitive to the Higgs mass Gambino, 04! Z " 0 had R 0 l A 0,l fb A l (P # ) R 0 b R 0 c A 0,b fb A 0,c fb A b A c A l (SLD) sin 2 $ lept eff (Q fb ) m W *! W * Q W (Cs) sin 2 $%%(e % e % MS ) sin 2 $ W (&N) g 2 L (&N) g 2 R (&N) *preliminary M H [GeV]

7 Higgs mass fit GeV!" 2 < 144 GeV (95% C.L.) Theory uncertainty!# had =!# (5) ± ± incl. low Q 2 data m Limit = 144 GeV LEP II Bound: > GeV 0 Excluded m H [GeV] Preliminary

8 Higgs mass fit GeV w/o A b FB (Thanks Tim Tait)!" 2 < 102 GeV (95% C.L.) Theory uncertainty!# had =!# (5) ± ± incl. low Q 2 data m Limit = 144 GeV LEP II Bound: > GeV Excluded Preliminary m H [GeV]

9 Higgs Mass Bound 95% CL limit on! (a) LEP "s = GeV Observed Expected for background m H (GeV/c 2 )

10 Higgs Mass Bound 95% CL limit on! (a) LEP "s = GeV Observed Expected for background New decays weaken the bound m H (GeV/c 2 ) Suppress SM BR s to 20%

11 The Higgs Width

12 The Higgs Width

13 The Higgs Width If there are new decay modes, this becomes a partial width...

14 Higgs Small Width h b b y b (m h ) 1 60 Γ h bb y 2 b

15 New Particle In Decay If then, perhaps h Z X X X X but Γ Z 1000 Γ h (m h = 115 GeV)

16 Precision Constraint Error bar is about 1 per mil Measurement Fit O meas!o fit /" meas #$ (5) had (m Z ) ± m Z [GeV] ± % Z [GeV] ± " 0 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] ±

17 Simple Addition to the SM Add h λh hss λv to the Lagrangian s s If the coupling is bigger than a few times 1/60, this decay dominates for a light Higgs.

18 Motivated Models Minimal Supersymmetric h χ 0 χ 0 Standard Model (msugra disfavored) invisible MSSM w/ R-parity violation h χ 0 χ 0 qqqqqq or or llqqqq llllνν

19 MSSM - Higgs Broad regions where this decay is important. If the neutralinos decay, the Higgs mass could be as low as 90 GeV tanβ X X X ruled out XXX M1 = 50 GeV M2 = 250 GeV Μ GeV 90%,85%,80%,75%,70% Carpenter, DEK, Rhee (2006)

20 RPV weakens bounds For B violation Sleptons (R) Sneutrinos Squarks (ul/r,dl/r) Stop Sbottom Gluino 94,85,70 GeV (A) 88,65,65 GeV (A) 87,80,86,56 GeV (L) 77 GeV (O,D,L) 7.5 (>55, <30) GeV (L)??? GeV? (???) Only Chargino bound roughly the same (102.5 GeV)

21 Motivated Models NMSSM (or MSSM with a singlet) New couplings and decays for the Higgs in SUSY can make it naturally heavier and make the LEP bounds weaker.

22 Motivated Models Models where the Higgs is a pseudo- Goldstone boson: Composite Higgs (revived as part of RS models) Little Higgs From the simplest little Higgs singlet field

23 Generic Signals Invisible 4+ jets (perhaps heavy flavors) 4+ leptons 2+ leptons and missing E 4 Zs or Ws or a combination combined signals

24 LEP Searches

25 Invisible Higgs 114 GeV LEP Combined - 01

26 110 GeV (but taus only > 86 GeV) Higgs to 4b

27 Model Independent Limit on k OPAL!s!" = 91, GeV Observed Expected (CL=95%) Thus the Higgs could be lighter (and EWP favors it) m S 0 (GeV)

28 Difficulty at hadron colliders h to jets hard - even standard decay to b s a challenge to recover at the LHC: σ(gg h b b) 20 pb σ(qcd b b) 1/2 mb h to multiple jets - soft jets difficult to reconstruct at the LHC

29 Strategies for searches Look at standard channels Look for new triggers Use non-standard experiments Use jet-shapes Come up with other ideas

30 Standard searches If the rate of Higgs boson decays to multiple jets is, for example, 4 times that into standard model modes, standard searches are dramatically weakened.

31 Higgs searches

32 Higgs searches 5 sigma here

33 Higgs searches 5 sigma here

34 We must study the new decay modes.

35 Typical decays A h C h a a X b _ b _ b b B h D h a a X g g g g q q q X X q q q

36 The Invisible Higgs C h X X

37 Two forward jets Eboli, Zeppenfeld (2000)

38 Two forward jets E T Eboli, Zeppenfeld (2000)

39 Hadronic decays Much harder. A h a b _ b Signal: σ 25pb events a PT cuts help! _ b b Background: σ 0.5µb 500, 000pb 10 9 events

40 Associated production q q W h a W a b _ b _ b b Signal: (with cuts) Background: σ 1pb 2,000 events σ 10pb 20,000 events

41 Tagging 4b s Softer b-jets make tagging and jet reconstruction difficult A vertex trigger should go in at Level 2 We have run higgs to 4b through CDF s b-physics triggers and found 30% efficiency! (Petar Maksimovic and Mark Mathis)

42 Decaying fermion D h X X q q q q q q 6 jets in principle has a smaller background, but these jets are of very low energy. would have to go to associated production in order to trigger at Level 1

43 Soft jets

44 Neutralino decay X ~ q q Like b hadrons, neutralinos may have a long decay length. ( 10 2 L 3µm λ q ) 2 ( q ) ( ) 4 5 m q 30 GeV 100 GeV m χ

45 Tevatron B-physics triggers CDF has roughly 1 fb -1 of B-physics data (not pre-scaled)

46 LHCb

47 LHCb 1 m 3 cm separation

48

49 Light Higgses are boosted ~30%

50 χ χ

51 Higgs/Neutralino search at LHCb Main worry: distinguish from b-quarks. M! 0 = 38 GeV N At least 5 charged tracks in acceptance M! 0 M! 0 = 98 GeV = 198 GeV Number and invariant mass of charged particles larger than for b s Invariant Mass (GeV) DEK, K. Rehermann (2007)

52 Higgs/Neutralino search at LHCb N At least 5 charged tracks in acceptance each 10 Single Events Double Events 1 year of running squark mass = 1 TeV coupling =.01 1 Aside: all susy (GeV) M! 0 DEK, K. Rehermann (2007)

53 LHCb simulated data after acceptance requirements and cuts: Could reconstruct the Higgs and measure its mass with ~10% accuracy. N. Gueissaz, (2007) CERN-THESIS

54 _ b b Even 4b at small m a a 40 a m a (GeV) b _ b DEK, M. McEvoy (2007) 10 M h = 115 GeV, M a = 15GeV M h = 145 GeV, M a = 15GeV M h = 115 GeV, M a = 35GeV M h = 145 GeV, M a = 35GeV Background m h (GeV)

55 _ b b Even 4b at small m a a a b _ b DEK, M. McEvoy (2007)

56 For all gluons B g h a g Background at least 1,000 times larger - no tricks yet... a g g

57 Other discriminants So heavy flavors and other macroscopic decays ( displaced vertices ) and perhaps special kinematics allow for distinguishing above background. We need more generic observables if possible...

58 Color flow g b _ b H b _ b

59 Showering differences The Chudakov Effect (QED)

60 Preliminary tests Here is a simulation of Higgs production and QCD production of two b-jets boosted w.r.t. the lab frame. N angfor1.5<rm< b _ b !

61 Preliminary tests Here is a simulation of Higgs production and QCD production of two b-jets boosted w.r.t. the lab frame. N angfor1.5<rm< b _ b !

62 Testing ground

63 Conclusion The Higgs search is at risk because the Higgs width is very sensitive to new light unseen physics. If so, new approaches may be needed to see the Higgs in a reasonable amount of time.

64 And we could get lucky Is that a Higgs in your data, or are you just happy to see me?