1. Searches for MSSM Higgs at the Tevatron Anton Anastassov (Rutgers University and CDF) Anton Anastassov (Rutgers University and CDF) TeV4LHC Workshop Fermilab October 20-22, 2005

2. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron2 Why MSSM? The simplest realistic SUSY model Resolves the hierarchy problem Higgs sector in MSSM: –Two charged bosons: H ± –Two CP -even neutral bosons: h, H –One CP -odd neutral boson: A –At tree level described by m A, tanβ=v u /v d –One of the CP –even Higgses is SM-like, the other one similar to A Confirm Higgs mechanism and physics beyond the SM In case of signal

3. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron3 Charged MSSM Higgs at the Tevatron Production Decays Searches Prospects

4. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron4 Charged MSSM Higgs Production qq, gg → H - H + bb, gg → W - H + gb → tH + ; qq, gg → tbH + (m H > m t -m b ) Top decays: t → bH + (m H < m t -m b ) Small cross-sections: not realistic at the Tevatron

5. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron5 Charged MSSM Higgs Decay Modes Major decay modes: – H + →   – H + → cs – H + → t * b → W + bb – H + → W + h → W + bb BR’s depend on: – tan β – mass of H + Differ from W + BR’s Take advantage of differences in W ± and H ± decays.

6. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron6 H ± Search Strategy Look at four tt final states: –di-lepton + jets –lepton + jets ( 1 b-tag) –lepton + jets ( ≥ 2 b-tags) –lepton + tau + jets Check consistency of the final states with SM expectation Interpret for several MSSM scenarios, tan β, and m H L int = 192 pb -1

7. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron7 Search for H ± : Results No-mixing benchmark scenariom h max benchmark scenario Consistent with the SM Final statebg eventsSM expdata 2ℓ + jets2.7±0.71113 ℓ+ jets (1b)20.3±2.55449 ℓ + jets (≥2b)0.94±0.17108 ℓ +  h + jets 1.3±0.222 Will be nice to have benchmarks designed specifically for charged Higgs!

8. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron8 No sensitivity to scenarios with  =+500 at large tanβ Search for H ± : Results One can also define a “tauonic model”: BR(H +  )=1 This search will improve significantly with higher statistics Potential development: include kinematics

9. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron9 Search for H ± : What about LHC? Will add the m H >m t region into the mix For t → bH + searches the techniques tested at the Tevatron will be of help –Example: apply the discussed approach to ATLAS (200pb -1 !!!) R. Eusebi, PhD Thesis (2005)

10. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron10 The Neutral MSSM Higgs Sector at the Tevatron Production Decays Search Strategies Results Projections

11. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron11 MSSM Higgs Production and Decays Gluon fusion b-quark fusion Couplings of A (and h or H) to b,  ~tan β Higgs decays: – bb (~90%) –   (~5-13%) Plots and diagrams from A. Belyaev

12. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron12 Searches for neutral MSSM Higgs at DØ Search in the Higgs → bb channel –Look for associated production with b(b) (suppress multi-jet bg) Require at least three b-tagged jets (identified using secondary vertex) b-tagging eff ~55% in |  | 35 GeV Mistag rate ~1% At least 3 jets with E T > 35, 25, 15 GeV Signal extraction: –Form invariant mass of the two highest-E T jets –Perform binned fit of the di-jet mass spectrum DØ hep-ex/0504018

13. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron13 B-tagging, di-jet Mass Spectrum Di-jet mass cross check: fit of double b-tagged sample with – Mis-tag sample – Heavy flavor bbj(j) – Z  bb+jets, Zb, tt, bbbb Triple-tagged (signal) sample Acceptance ~0.3-1% (m A =90-150) Major sys uncertainties: – b-tagging (15%) – JES/resolution (9%), – signal simulation (5%) – trigger (9%) – luminosity (6.5%) – Bg estimation (3%) DØ

14. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron14 Limits on Neutral MSSM Higgs Production No evidence of signal found Interpretation of the results: m h max and no-mixing scenarios with μ<0 The search is sensitive down to tanβ~50-55 for m A ~90-120 GeV (with 260 pb -1 of data) DØ Benchmark: hep-ph/9912223, Carena, Heinemeyer, Weiglin, and Wagner

15. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron15 What can the Tevatron do? Explore the low m A region Understand the contribution of 4b QCD background –Methods of determining bbqq, bbbb fraction, effect of bbcc Check with b-energy with Z  bb

16. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron16 What can the Tevatron do Explore the low m A region Understand the contribution of 4b QCD background –Methods of determining bbqq, bbbb fraction, effect of bbcc Check with b-energy with Z  bb Improve jet pairing Improve jet energy resolution Multivariate analysis –Di-jet mass alone does not provide sufficient discrimination

17. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron17 Search for inclusive production and subsequent Higgs decay to ττ –Tau decays: ~37% leptonic, ~63% hadronic Notation used in the talk:  ℓ :  → ℓ  ℓ=e,  h :  →hadrons hep-ex/0508051 Search for Neutral MSSM Higgs at CDF Reconstruction of  h : Use two-cone algorithm (signal & iso) – Four-momentum from trks and  0 ’s – Isolation veto (trk,  0 ) Electron veto Hadronic system: – m had < 1.8 GeV – N trk = 1,3 ; charge = ±1 Efficiency: ~40-50%, governed mostly by the isolation requirements

18. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron18 Search for Neutral MSSM Higgs at CDF W  control sample: p T distribution of the hadronic decay products in  hadrons Do we understand  MC modelling? Event selection –Two tau candidates in the central detector (|  |<1.0) One tau decays leptonically, p T ℓ >10 GeV Second one hadronically, p T  >15 GeV –Opposite charge of  ℓ,  h –Multi-jet supression: |p T ℓ |+|p T  |+|E T | > 50 GeV –Z  ℓℓ suppression: |m Z -m ℓ trk |>10 GeV –Suppress W+jets

19. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron19 Backgrounds from jet   h mis-ID Backgrounds with jet  h mis-ID: – Multi-jet: mis-ID/non-isolated e,m + jet  h mis-ID – W+jet(s): W  e(  )  jet  h mis-ID –  + jet(s):  ee, jet  h mis-ID (affects only  e  h ) Estimated using “fake rate”: probability for jet →  mis-ID –Obtained from jets in data –Verified on control samples Fake rate ~1.5-0.1% (E T jet =20-100 GeV) All other backgrounds estimated from MC

20. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron20 Results Before N trk and opposite charge cuts source  e  h +    h Z →  404.5±5.3±23.2 Z → ℓℓ 14.3±0.9±0.8 tt, VV1.9±0.1±0.1 jet →  fakes 75.4±0.2±15.1 Predicted bg496.1±5.4±27.7 Observed Events487 Observed number of events consistent with bg expectation Need discrimination between sig/bg to sharpen sensitivity

21. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron21 Partial Mass Not enough info for full m  reconstruction Approximation: project E T onto vis  decay products –Significant loss of statistics (factor of ~6-8) –Mass resolution does not compensate Alternative: use partial “mass”: Weaker discriminator than full mass Non-linear relation with mass Still, there is substantial non- overlapping region Can be calculated for all events Look for Higgs by performing likelihood fits to m vis

22. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron22 Search for Neutral MSSM Higgs at CDF Dominant systematic uncertainties: –Particle ID:  h (3.5%), e (1.3%),  (4.5%) –Jet →  mis-ID estimate (20% conservative)  3% on total bg –PDF’s (5.7%) –Luminosity measurement (6%) Signal acceptance ~0.8-2% (m A =90-250 GeV) Example fit for m A =140 GeV

23. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron23 Search for Neutral MSSM Higgs at CDF Interpretation of the results in m h max and no-mix scenarios with  0 Account for radiative corrections following Carena, Heinemeyer, Wagner, and Weiglin – FERMILAB-Pub-05-370-T The bb and  Higgs decay channels show nice complementarity! Benchmarks: hep-ph/9912223 (  0), Carena, Heinemeyer, Weiglin, and Wagner

24. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron24 What can the Tevatron do? Probe the lower m A region Develop/test algorithms for  h reconstruction Understand tau mis-ID, develop techniques for background estimation Neutrinos in final state  need good MET resolution for mass reconstruction Projection assumptions: CDF and D Ø have similar sensitivity 30% improvement on acceptance (additional  channels) Improvements in sig/bg separation are not taken into account

25. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron25 What can the Tevatron do? Look exclusively at b(b)H  b(b) , one tagged b-jet: loss of signal, but Z is significantly supressed  Need to know  (Z+b) CDF CDF Run II (335 pb -1 ) D Ø Run II (185 pb -1 ) NLO  (Z+b) (pb) 0.96±0.32±0.14-0.49  (Z+b)/  (Z) (%) 0.38±0.12±0.05-0.19  (Z+b)/  (Z+jet) (%) 2.37±0.78±0.382.3±0.4±0.31.85 The DØ measurement uses fixed N c /N b from theory. No assumptions on N c /N b are made for the CDF measurement. Measurements of  (Z+b) with Z  ℓℓ (ℓ=e,  ) by CDF and DØ DØDØ

26. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron26 Other models When looking for Higgs BSM, no need to be restricted to the simplest scenario Look for MSSM scenarios with CP violation –Interest and support from theorists exist Look for Higgs decays with LFV –H  comes to mind Look for Higgs in NMSSM: –H  aa is real fun Look for H ++ H -- –Some result are already out, other on the way Little Higgs …

27. Oct. 20, 2005Anton Anastassov - Search for MSSM Higgs at the Tevatron27 Concluding remarks After a somewhat slow start the Tevatron is producing quality results on MSSM Higgs The next iteration of the searches is under way  the winter conferences will be interesting A lot in common between LHC and the Tevatron – techniques can be recycled and improved But… where is the MSSM Higgs? Some claim to have part of the answer: Likelihood map by Allanach & Lester (hep-ph/0507283)