Linear Collider Higgs Studies

Transcription

1 Linear Collider Higgs Studies Outline: Plans back in Berkeley What has changed Current state of art What needs doing, detector issues Talk to Linear Collider Detector (LCD) Working Group SLAC, Stanford, CA 14 November 2000 Rick Van Kooten Indiana University

2 Higgs Properties Mass ( ) l Pinning it down... LHC, only t, t? Yukawa couplings: (mass to fermions) g f f H µ m f? Br's, s Mass to vector bosons: More than one Higgs? hi Z fi Z g M V 2 v 2 VVH w i µ M 2 V? Br's, s w Fully generate mass of Z? S i V = Z,W 2 2 = v Decays to other bosons: g,g g,g Sensitive to new physics Total Width (direct) or Br's, s (indirect) or Spin, parity, CP nature Ang. dist., s g g Form of Higgs Potential, self-coupling, l HHH, HHHH s ZHH

3 Summary of Plans: Higgs WG (from Berkeley 2000) Older Snowmass studies, update: DG (tot)/g (tot) Ds (x)/s (x) D Br/Br D m /m h h vs m h, int. luminosity Compare LC/LHC (update numbers for LHC from D. Rainwater) Ensure that NLC 'S2'/'L2' detectors have similar Br precision performance as TESLA CDR/improved ( t +t ) cc / bb / gg fi someone from vertex detector group? (Brau et. al.) plus FNAL Light Higgs Group WW* fi energy flow important Important Br! For light higgs, fewer stats, used in total width determination More SUSY interpretation? (FNAL group?) Confirm l HHH precision/feasiblity and lumi. needed (also needs theory input)

4 Spin and CP - angular distributions - tth - experimental simulation - H Æ t H Æ t t t + Add Br(invisible!) Br( H Æ ZZ* ) s ( H ee ) precision estimates 0 0 ± Heavy/light A / H / H Masses and separation of degeneracy Br's and extraction of tan b g g Higgs studies J. Hill, g g group and D tan b W. Wester, Int. and Heavy Higgs FNAL WG

5 What has changed? Results from LEP2, possible evidence? Two scenarios: Either way (particularly second), substantial chunk of time where we won't know if it is there at 115 GeV or not fi slide Need to respond with LC strategy if Higgs indeed at 115 GeV Results from LCWS2000: New "State of the Art" slide CERN Council, scientific policy committee changes DG's decision to shutdown LEP2 LEP2 shutdown, Fermilab enters the fray Implications on properties if SUSY Higgs fi Optimum running strategy: lower center-of-mass, run lower energy beam line (detector "P") at s (HZ) peak? fi slide

6 From Nov. 3 LEPC, all experiments combined: 2 Events / 3 GeV/c s = GeV LEP S/B=1.0 background hz Signal (m h =115 GeV) 5 all cnd= 59 bgd= sgl= 4.66 > 109 GeV Events / 3 GeV/c s = GeV all cnd= 24 bgd= sgl= 2.74 LEP S/B=2.0 background hz Signal (m h =115 GeV) > 109 GeV Reconstructed Mass m H [GeV/c 2 ] 1-CL b LEP TOTAL Observed Expected s+b Expected b m H (GeV/c 2 ) H 2s 3s 4s 2.9 s Effect Mass "=" GeV

7 115 GeV Years, not months

8 Even if SUSY Higgs, already close to SM Higgs properties fi even more need for precision measurements of properties tanb Coupling sin ( b - a ) 2 M large, "decoupling" A Life is good, see all the neutral s = 500 GeV 0 h Standard Model-like in production and decay H 0, A 0, H ± begin to be mass degenerate m (GeV) A Need s > 500 GeV to see the Higgses heavier than h 0 Excluded by 95% C.L. Approaching decoupling!

9 Mass Recoil mass: m = s 2E s M 2 2 recoil Z Z Z 0 + m Z q Z 0 m Z _ q Include bremstrahlung and beamstrahlung effects H 0 H 0 Decays to X, including invisible More precision from Z Æ e e Z Æ m m + + decays + vertex constraint TESLA CDR Detector Garcia-Abia, Lohmann Number of Events / 0.5 GeV No beamstrahlung Beamstrahlung Number of Events / 0.5 GeV m H Data Z H Æ ee X = 120 GeV Recoil Mass [GeV] Recoil Mass [GeV] Includes lepton id, systematics in effic. and 1% on luminosity s = 350 GeV, 500 fb 1 D m H = 140 MeV D m H ~ 230 MeV 200 fb 1 D s ZH s ZH D g = 3.5% fi ZZH = 1.8% g ZZH

10 Update Data Z H µµ X Number of Events / 1.5 GeV m H = 150 GeV Recoil Mass [GeV] Mass Fit Cross Section (fb) Stat. Error(%) 1 1 (GeV) /500 fb /500 fb ± 0.13 (stat) ± 0.12 (syst) 2.4% ± 0.12 (stat) ± 0.10 (syst) 2.7% ± 0.11 (stat) ± 0.08 (syst) 3.0%

11 Mass Direct Reconstruction: dijet invariant mass ZH Æ qqh _ resolution s = 500 GeV, m h = 120 GeV 4 jets realistic simulation, "L" LC detector, r = 1.5 cm Take 2-jet combo b-tag and neural net event selection inv. mass closest to Z (LEP2 tools) Juste, ' Before kinematic fit (including beamstrahlung) Dijet Mass After kinematic fit D s ZH s ZH ~ 9.7% (stat.) fi D g ZZH g ZZH ~ 4.9% (stat.) 10 fb 1 D m H ~ 350 MeV (stat.) 10 fb 1 D m H ~ 80 MeV (stat.) 200 fb 1 D m H ~ 50 MeV (stat.) 500 fb 1 comparable to TESLA TDR How much gain from kinematic fit? What if channel prevents it?

12 Study of Energy Flow in Jet Reconstruction R. Frey & M. Iwasaki, Univ. of Oregon Good jet reconstruction essential to explore and make use of all decay modes multi-jet masses: e.g. Zh vs ZZ vs WW reconstruct parton angles to extract quantum numbers, anomalous moments, e.g. WW, t t, t! bqq 0 Use combination of tracker and calorimeter which provides best resolution: tracker for h, EM cal. for 0 (, HAD cal. for K 0 L, etc.) Requires excellent { h id. ) EM Cal. segmentation Realistic modelling requires more-than-primitive cal. clustering algorithm(s) This Study: Develop EFlow technique in LCD simulation Implications for detector design in terms of physics benchmarks Compare to other techniques for jet recon. Start with LCD Fast Simulation Move to Full Sim. (Gizmo/GEANT 4), clustering alg. (c.f. N. Graf talk)

13 Energy Flow - Detector S; d2d >0:5 cm,(de > 5 GeV), no R cut: JJ Mass 12 JJM Nent = 70 Mean = 97.5 RMS = Energy Flow - Detector L; d2d >1:5 cm, (de > 5 GeV), no R cut:: JJ Mass 14 JJM Nent = 64 Mean = RMS =

14 Another good detector requirement check: recoil mass against jets (in particular, can isolate WW fusion channel) number of events/500 fb Jet-Jet Missing Mass for e + e 0 H νν bb νν sqrt(s) = 350 GeV WW-Fusion mh = 120 GeV Higgsstrahlung Interference Background missing mass (GeV)

15 q Z 0 m Z _ q Recoil mass recoiling from any pair of jets with invariant mass within 10 GeV of M W H 0 W ( * ) n s = 350 GeV, m h = 120 GeV Z 500 fb 1 anti-tag against b jets Borisov, Richard Number of events / 5 GeV/c Recoil mass (GeV/c 2 ) D Br(h Æ WW*) Br(h Æ WW*) ~ 5.1%

16 Mass (and Spin) Scan threshold, lower energy beam line?? NLC only, special threshold runs, Competitive! fb 1 Barger, Berger, Gunion, Han 100 D m H [MeV] 60 s (pb) m H [GeV] m = 150 GeV H (b) ZH Map threshold s (GeV) H nn Hee LCWS 2000 fi general treatment of b dependence across threshold, gives spin info (e.g. spin-0 linear in b )

17 b quarks Battaglia c quarks s = 350 GeV, 500 fb 1 g realistic simulation, TESLA CDR detector, CCD at small radii advanced jet flavour tagging techiques (topological and kinematic [e.g. vertex mass]) allows separation of light quarks and c quarks separately from b quarks Entries/100 fb light Quark Tag c Quark Tag b Quark Tag Each candidate hadronic Higgs decay, compute light quark, cc, and bb di-jet flavour tagging probabilities Subtract background from Higgs peak sidebands Binned likelihood fit to the different flavour fractions

18 Higgs Branching Ratio 1 Battaglia % uncertainty bands on predictions m H (GeV/c 2 )

19 Event simulation Pandora-pythia and Pythia v5.7 beamstrahlung included and important Detector model : L2 e + e ZH H bb H ττ H cc H gg H WW e + e WW e + e ΖΖ e + e qq e + e tt s = 500 GeV M H = 140 GeV/c 2 L = 500 fb -1 Analysis with Z l + l evts, scaled to Z qq (OPAL, D. Strom) Very Preliminary Results Presented in this Talk Previous studies: Hildreth, Barklow, Burke, PRD49, 3441 (1994) M. Battaglia, HU-P-264 (1999) G. Borisov, F. Richard, LAL (1999) J. Brau, LCWS 2000, October 26, 2000

20 Efficiencies and Purities (M H = 140 GeV/c 2, s = 500 GeV, Model L2) Eff. Signal/Backg. H bb H ττ H cc H gg H WW * Preliminary (not optimized) (My add: they are including neural net selection, additional ZVTOP studies) J. Brau, LCWS 2000, October 26, 2000

21 Detector Parameter Dependence Branching Ratio Errors (M H = 140 GeV/c 2, s = 500 GeV, L = 500 fb -1 ) L2 2.4 cm L2 radius* H bb ±.014 ±.017 H ττ ±.005 ±.006 H cc ±.011(46%) ±.014 (60%) H gg ±.020(59%) ±.026 (78%) H WW * ±.031 ± µm res. *(optimistic-primary vtx) (My add: they are including neural net selection, additional ZVTOP studies) Preliminary (not optimized) J. Brau, LCWS 2000, October 26, 2000

22 S. Xella Running at different s? uds-tag efficiency Monojets at 45 and 100 GeV b-tag efficiency c-tag efficiency b-tag efficiency

23 Gunion, Brau, Pitts, Martin s Br(h Æ g g ) CMS detector EM resolution 2%/ E 0.5% Snowmass NLC detector EM resolutions 10%/ E 1.0% JLC detector EM resolution Brient, Reid, Schreiber 200 fb 1 fi s = 350 GeV, m = 120 GeV h 1000 fb 1 TESLA CDR detector, D E = 10% 0.6% E E D Br(h Æ gg ) ~ 14% Br(h Æ gg ) (stat.)

24 TESLA TDR Detector, Schreiber et al. 14% relative error on gg Br 1000 fb 1

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27 Total No. Recoil Number observed Higgs decays (why not direct, Z recoiling against "nothing"?) BR / BR d BR(H Æ invisible)

28 Total Width Determination (older slide) m H m H <~ ~ > Where g g Collider, LC, LHC 115 GeV (almost ruled out by LEP2!) 115 GeV G ( H Æ W W* ) G tot = from: G ( H Æ W W* ) Br( H Æ W W* ) LC s ( H nn ). Br( H Æ bb ) How firm is this boundary?? LC increasing assumptions s ( H Z ) s SM( H Z ) LC. G ( H Æ Z Z* ) SM (coupling universality) G ( H Æ W W* ) SM G tot 1 to ~10% with 200 fb and 120 GeV Higgs, to a few percent for less than 150 GeV How well can we do WW* Br at 115 GeV? How well can we do bb Br at m > 160 GeV? (Br just a few percent, "rare" decay, W. Wester, FNAL) m H ~ > 205 GeV, G tot SM ~ 2 GeV, directly resolvable Departures? fi New physics!

29 TESLA TDR: events/ cos(q z ) Sensitivity to A mixture: 0.13 (shape only) and 0.03 (shape plus s )

30 e + e Coupling to top, g tth Heavy Higgs But if light, radiation off top s µ ~ Z e + Z* H Z*/ g t * 2 g tth m H t = 120 GeV e H t t needs large s cross section decreases rapidly for heavier Higgs Hadronic fi 8 jets, 4 are b jets Semileptonic fi b b 6 jets, 4 are b jets, isolated lepton, missing E fi Juste, Merino s = 800 GeV = 120 GeV m H 1000 fb 1 D g tth g tth Neural net selection, some systematics ~ 6%

31 1.0 e + e - -> tth L=1000 fb -1, b =.6 g tth /g tth 0.5 s=1 TeV =500 GeV M h (GeV)

32 Experimental Issues fi systematics on precision measurements Luminosity Measurement (e.g. for s, s. Br ) Z g Wide-angle (endcap) bhabha (out of mask) Good to 1%? "Loopvergin" - Miller Luminosity Spectrum (after ISR, beamstrahlung) Frary, Miller Kurihara (e.g., for kinematic fits) extract from acollinearity angle distribution of bhabhas fi stable enough in time? e+ Event Overlap q e Look at ZZ events Train Many bunches per train msec spacing between trains nsec spacing between bunches high luminosity per bunch t

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35 Double Higgstrahlung WW Fusion _ Plus triple + n higgs e Z + e production Z * H H W * in SUSY H * H * W * e H H e e.g., Z plus 4 b-jets n s pol [fb] 0.6 SM Double Higgs-strahlung: e + e - Æ ZHH s pol [fb] GeV 1 TeV TeV M H [GeV] Djouadi, Kilian, Muhlleitner, Zerwas Miller, Moretti Bambade, Gay, Lutz High luminosity, 1000 fb 1 Acceptance and b tagging in forward region Polarization fi l to ~ 15 20% HHH Quartic couplings ~hopeless, s (ZHHH) < fb

36 Status/Plans Not a great deal of progress since Berkeley, but Vertexing/energy flow at Oregon FNAL Group: vertexing, spin, rare Br, intermediate mass (but Tevatron start-up, increasingly busy...) IU: finally approved for other 50% of NLC postdoc through university Please come help Meeting with Howie Haber, Andreas Kronfeld, Jack Gunion, RVK after LCWS2000: planning of Higgs organizational meeting, try before Christmas Need to take into account that we will probably need a strategy for what to do if a 115 GeV Higgs exists fi fi different s? Higgs physics with "P" detector at GeV? Threshold scans?

37 For Detector Studies Momentum resolution benchmark H Z Æ m Recoil mass resolution m Masses 115, 140, 160 GeV s = 500, 350, 250 GeV + Electromagnetic calorimetry benchmark H Z Æ Recoil mass resolution + e e Masses 115, 140, 160 GeV s = 500, 350, 250 GeV H Æ gg Masses 115, 130 s = 500, 350, 250 GeV

38 Jet energy & calorimetry benchmark H Z H Z Æ jets Direct reconstruction, 4 jets, plus kinematic fitting Masses 115, 140, 160 GeV s = 500, 350, 250 GeV Recoil mass against jets Masses 115, 140, 160 GeV s = 500, 350, 250 GeV H nn Æ bb Jet-Jet Missing Mass, distinguish fusion and Higgstrahlung Masses 115, 140, 160 GeV s = 500, 350, 250 GeV Vertexing: already working with samples, consider including Mass of 115 GeV s = 350, 250 GeV? "P" Detector?