Search for BSM Higgs at the Tevatron Anton Anastassov (Northwestern University) For the CDF and D Ø Collaborations Aspen 2008 Winter Conference: "Revealing the Nature of Electroweak Symmetry Breaking" January 15, 2008

Search for BSM Higgs at the Tevatron - Anton Anastassov2 BSM Higgs Searches Look for particles consistent with the expected physical manifestation of extended Higgs models: –2HDM, Higgs triplets –Add SUSY  a range SUSY models –Little Higgs models –…anything that goes beyond the SM Higgs Production/final states may be: –Unique to the BSM models –Similar to SM, but with modified production rate/BR’s Many search possibilities, but… finite manpower  the CDF and D Ø programs concentrate on: Modes/models seen as most promising at the Tevatron Final states that can be efficiently triggered on

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov3 The Tevatron Collider and Detectors CDF and D0: General purpose detectors, axial and forward- backward symmetric Precision tracking (incl silicon detectors) Hadronic and EM calorimeters Muon chambers TOF systems Recorded more than 3 fb -1 / experiment of quality data (results in this presentation use up to 1.8 fb -1 )

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov4 The tools of the searches The searches described in the following rely on good particle identification: Electrons Muons B-jets Photons Taus (hadronic decays)  Very well understood Use characteristic energy in the EM and HAD calorimeters; hits in the muon chambers (  ) Easily accessible standard candles (Z, W) (see J. Zhu’s presentation on EW results at the Tevatron) Displaced secondary vtx associated with the jet Probability of tracks in the jet not originating from the IP Soft leptons (e,  ) in jets Wealth of information  apply multivariate techniques (see Weiming Yao’s talk for detailed discussion) Energy deposition in the EM calorimeter not associated with a track Shower shape to discriminate against  0 ’s

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov5 Tau Reconstruction (hadronic decays) Two-cone algorithm for tracks and  0 ’s : – Common axis: direction of a “seed” track  Signal cone  reconstruct  Isolation annulus  implement jet veto NN selection Variables: –Shower Profile –Calorimeter, track isolation –Charged fraction –Opening Angle –etc. Define 3 types: –  -like,  -like, multi-pion Spectrum of taus from Z  after background subtraction Spectrum of taus from a W  sample Similar reconstruction/misidentification rates at CDF and D Ø

Review of Direct BSM Higgs Searches at CDF and DØ –Doubly-charged Higgs –Fermiophobic Higgs (h f  ) –MSSM Higgs (CP-conserving) Charged Neutral

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov7 Searches for H ±± H ±± predicted Higgs triplet, L/R symmetric models H ++ can be light: ~100 GeV DY-like H ++ H -- pair production Decays to same/different-flavor leptons Detection modes: 4 identified leptons 3 ID’d leptons (+ 1 missed) Use of tight/loose ID Most resent Tevatron search: DØ: H ±±  (1.1 fb -1 ) –Exp (obs): 3.1 (3) events  m L(R) >150 (126.5) 95% CL Previous searches from CDF ( pb -1 ): ee, e , , e ,  m L >114, % CL All Tevatron searches are statistics limited Will benefit significantly from the full data samples After adding H ±±  the Tevatron will cover all decay modes

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov8 Search for Fermiophobic Higgs  Searches for h f  in Run II (1.1 fb -1 )  +X final state: pp  VV  h f  +X, pp  h f W(Z) m hf >90 95% CL (assuming SM couplings)  +X final state : pp  h f H ±  h f h f W ± (suppressed VVh f couplings) –possible in 2HDM for m hf 1 –Favorable conditions: BR(H ±  h f W ± ), BR(h f  )≈1 N bg =1.1 ± 0.2, N obs =0   x BR(H ±  h f W ± ) x BR(h f  ) 2 < % CL (mass limit depends on assumed model) Fermiophobic Higgs: –Suppressed couplings to fermions –Searches for h f  LEP II: m hf > % CL (assuming SM couplings) Tevatron Run I: qq’  V*  h f Z, m hf >78.5 (82) 95% CL D Ø (CDF)

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov9 Minimal Supersymmetric Standard Model (MSSM): SUSY extension of the SM with minimal particle content Requires two Higgs field doublets Five physical states: H, h, A; H ± Lightest Higgs (h) mass close to EW scale At tree level defined by m A and tan  = v u /v d A couplings to b,  enhanced by ~tan  But… complicated picture when radiative corrections are included, dependence on additional parameters:  consider “benchmark scenarios”: Searches for MSSM Higgs M SUSY  M2M2 X t OS m gluino m h max 1 TeV ± 200 GeV 200 GeV2 M SUSY 0.8 M SUSY no-mixing2 TeV ± 200 GeV 200 GeV00.8 M SUSY

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov10 Search for Charged MSSM Higgs H  modifies top BR’s (mostly at large and small tan  W ± and H ± decay modes differ: take advantage of different topologies in tt final states H  from t → bH + is the most accessible mechanism at the Tevatron (can probe m H < m t -m b ) Expected number of events in the SM and MSSM for four topological final states (L int = 192 pb -1 )

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov11 Search for Charged MSSM Higgs Final statebg eventsSM expdata 2ℓ + jets2.7± ℓ+ jets (1b)20.3± ℓ + jets (≥2b)0.94± ℓ +  had + jets 1.3±0.222 Exclusive H ±   search (L int =335 pb -1 ) Final state: e(  +  +b + X N bg =3.9 ± 0.5, N obs =6 Combined analysis of 4 final states Measurement of R  =  l+jets /  ll (1 fb -1 ) R  =1.21 ± 0.27  consistent with the SM H ± exclusion assuming BR(H ±  cs)=1 BR(t  bH ± 95% CL

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov12 Neutral MSSM Higgs production Higgs decays: – bb (~90%) –   (~9%)

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov13 Neutral MSSM Higgs For large tan  h or H are almost mass degenerate with A, similar couplings The other one is SM-like, low-mass (m<135 GeV) Production and decays are affected by radiative corrections * The bb channel is more sensitive to these corrections (and therefore to the SUSY specific scenarios), while the  channel is more robust * M. Carena, S. Heinemeyer, G. Weiglein, and C.E.M. Wagner, Eur.Phys.J. C45 (2006)  b is a function of SUSY parameters

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov14 Neutral MSSM Higgs Decaying to bb Look for associated production with b(b): suppress multi-jet backgrounds –Have to pay a price Require at least three b-tagged jets Look for signal evidence in the mass of the two highest-E T jets Biggest challenge: predict bg, shape Apply mistag rates to bbj events to determine shape Normalize (outside of signal region) to the observation Check the predicted shape using MC multijet events (flavor composition fixed to theoretical predictions) Use MC to get shapes and biases for different flavor composition Create 2D templates: di-jet mass vs m diff tag discriminating variable (m diff tag = m 1 tag +m 2 tag -m 3 tag ) 2D fit of m jj and m diff tag used to extract signal and determines bg flavor composition

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov15 Neutral MSSM Higgs Decaying to bb Di-jet mass distribution of the two highest-E T jets in the D Ø search (triple b-tagged events) The data are consistent with SM expectation. Extracted limits (L int =0.9 fb -1 )

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov16 Neutral MSSM Higgs Decaying to bb Extracted limits (L int =0.98 fb -1 ) 2D fit results, projections on the two variables. The data are consistent with SM expectation.

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov17 Neutral MSSM Higgs Decaying to   e,  ,  had are shorthand notations for  →e,  → , and  →hadrons, respectively. Final state signatures are determined by the tau decay modes Channels used in the presented searches: 6%  e   23%  e  had 3%     41%,  had 23%,    had 3%  e  e Advantages of the Higgs  mode: Lower bg’s compared to bb, probe all production modes Weaker dependence of sensitivity on SUSY parameters: more robust  e  had    had  e   (1.8 fb -1 )    had (1 fb -1 ) previous result also used  e  had  e     being updated Major backgrounds in Higgs  : – Z  (dominant) – Bg’s from jet  fakes: multi-jet, W+jet(s),  +jet(s) (  e  had only ) – Z  ee, Z , tt, other (small)

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov18 Neutral MSSM Higgs Decaying to  Not enough info for full m  reconstruction Approximation: project E T onto vis  decay products (discussed later) Higgs/Z separation: CDF: Use partial “mass”: D Ø : Form a NN using m vis and other event variables

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov19 Neutral MSSM Higgs Decaying to  m vis (GeV/c 2 )

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov20 Exclusion 95% CL Interpretation of the limits

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov21 Neutral MSSM Higgs: Near Future at CDF and DØ Utilize the full data samples Multivariate signal selection Separate treatment of events with associated b-quark (for  ) Use full mass reconstruction (when possible) Fully reconstructed m  at CDF Use collinear neutrino approximation Subset of selected events No special optimization for these plots Previous D Ø result from the exclusive search for

January 15, 2008Search for BSM Higgs at the Tevatron - Anton Anastassov22 Summary Contrary to some rumors… CDF and D0 have not observed a Higgs signal yet However, diverse (and demanding) research programs are being actively pursued –Future progress depends on both Efficient utilization of the larger available samples Improved analysis techniques Following the established pattern, expect updated results at the coming winter conferences