Status Report on hbb Analysis Jyothsna Rani for the hbb group Andy, Avto, Marine, Tim, Boris All D0 Meeting 28 th January th January 2005

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR2 Outline  Introduction  Higgs production  Signal kinematics  Analysis overview  Limits and Exclusion plots  Summary & Outlook

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR3 Introduction MSSM has pairs of Higgs doublet fields – H u couples to up-type quarks and leptons and H d to down- type – The ratio of their VEV ’s is defined as: tan  = / – 5 Higgs particles after EWSB: h 0, H 0, A 0, H +, H - – h 0 is ‘guaranteed’ to be light: m h0 < ~ 130 GeV (MSSM) TOP  5FNS BOTTOM  4FNS h 0, H 0, A 0 production at Tevatron

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR4 bh vs bbh Cross-section (fb) Inclusion of closed top loop diagrams Solid  4FNS Dashed  5FNS

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR5 Higgs Production and Large tan   Large tan  → enhanced bbh/H/A  At tree level, cross section rises like tan 2   A and h/H are produced simultaneously. CP odd Higgs CP even Higgs h H A Total cross section

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR6 Neutral MSSM Higgs Branching Ratio CP odd Higgs CP even Higgs tan  = 5 tan  = 40

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR7 Masses and Widths Using M. Spira’s HDECAY 3.101, tan  = 30

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR8 QCD Calculations at NLO Significant progress has been recently made by theorists –Have d  /dpT, d  /d  at NLO –Uncertainties from renormalization/ factorization scales variation –PDF errors evaluated following CTEQ prescription For generator cuts: |  | 15 GeV

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR9 MSSM Framework SUSY  Only recently did thorough investigations.  Have tan  enhancement factors in 5 MSSM scenarios at one-loop level.  Significantly different from tree level assumption of tan 2   Along the lines of the Tevatron SHWG studies  More importantly, have  ×BR enhancement factors in terms of tan  effective vs. tan 

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR10 MSSM scenarios Function of various SM/SUSY parameters: X t =A t -  cot , , M g, M q, etc. Loop level corrections to cross section and BR with

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR11 Pre-selection and Luminosity  Pre-selection cuts:  “at least three offline jets with lead jet pt > 20 GeV and two jets with pT >15 GeV (uncorrected) and |  | < 2.6”  Data collected during Nov 2002 – June 2004 with v9 – v12 Trigger List versions.  87.5M events corresponding to Integrated Luminosity 260 pb -1  Exclude Jet/MET badLBNs for v9 – v12 Trigger List.

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR12 Event Selection - Triggering NewOldLevel 3 * 5GeV4 * 5GeV L1: tower E T 2 * 25GeV 1 * 15GeV 3 * 15GeVL3: jet E T 3 * 8GeV 50GeV L2: jet E T  (E T >5GeV)  Three levels of triggering (old and new trigger version).  Efficiencies relative to offline selection of 68-80%, depending on Higgs Mass.

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR13 Event Selection - Offline Loose initial analysis cuts Optimized analysis cuts for each signal mass

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR14 Jet pT and  distributions  distribution JES corrected pT In Data after the Kinematical cuts.

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR15 MC Samples (Signal and Background) Signal Samples: –h(  bb)b, 3b final state with parton pT > 15GeV mh=90, 100, 110,120, 130 and150 GeV each 100K events using PYTHIA generator. Background Samples: –Heavy Flavor Multijet process “bbjj” (ALPGEN). –QCD Irreducible process “bbbb” (ALPGEN). –Fake Jets, “jjjj” (obtained from DATA). –ttbar (PYTHIA). –Z(  bb)+X (PYTHIA). –Z(  bb)+b (PYTHIA).

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR16 Analysis Overview Signal hb(120)  Signal:  at least 3 b-tagged jets  Invariant mass of leading jets at mh  Backgrounds:  “QCD heavy flavor” : bbjj, ccjj, cccc, bbcc, bbbb  “QCD fakes” : jjjj  “Other” : Z(bb,cc), tt  Kinematic cuts  Cut on ET of leading jets  Optimize for each Higgs mass  Look at the di-jet invariant mass of the leading ET jet combination.  Search for an excess of events consistent with a Higgs signal shape. Fitted Background Data

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR17 Background Estimation Full multi-jet data sample Double b- tagged data sample Calculate TRF (E T & 3 Regions of  ) Apply TRF Triple b- tagged background shape Fit outside to real triple b-tagged distribution Tag Rate Function Probability to b-tag a jet Cross-check of background estimation methods

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR18 HF Correction to Tag Rate Function Full multi-jet data sample Double b- tagged data sample Calculate TRF (E T & 3 Regions of  ) Fit with sum of the backgrounds Assuming only light jets, no HF HF Normalizatio n Calculate HF corrected TRF (E T & 3 Regions of  ) After the HF correction. bbjj, bbbb, ttbar, zb, jjjj (fakes from DATA)

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR19 Efficiency and Tag Rate functions SVT Loose

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR20 Double b-tag  Cross-check performed on double b-tagged events  ALPGEN bbj+bbjj samples  Tests:  TRF parameterization and background estimation methods  Trigger modelling  b-tagging efficiency and kinematic bias  Jet reconstruction efficiency and kinematic bias Before HF correction After HF correction

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR21 Double b-tag Mbb and Triple b-tag The 3-b background is also estimated using the MC and compared as a cross-check. Requiring the two jets to be b-tagged (Mbb) in double b-tagged events.

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR22 Triple b-tag background fit At the 95 % exclusion For tan  = 100

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR23Systematics  Acceptance uncertainties:  Higgs pT spectra (theory)  Trigger efficiency  Di-jet mass resolution  Jet reco/ID efficiency  Jet energy scale uncertainty  b-tagging efficiency  Background uncertainties: (roughly independent of mass)  Quality of the Tag Rate Function parameterizations (χ2)  Statistics of the 3 b-tagged data outside the signal region Totals: Signal ~ 20% Background ~ 3% IN Parcentage %

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR24 Exclusion Plot with 260pb -1 data  Exclusion limits are calculated using ROOT’s TLimit CL S = CL S+B / CL B  Sweep through tan , given mA Measured rate Tree Level Assumption

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR25 Exclusion Plot Tree Level Assumption

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR26 Future Projections  Using the expected (m A, tan  ) limit, future projections with higher Int. Lumi are made.  Sensitivity to tan  down to ~40 for mA=100GeV with 4fb -1 data and with the current assumptions and performances. Int Lumi in pb -1

ADM, 28th Jan 2005K. Jyothsna Rani -- TIFR27 Summary and Outlook  Improvements since Moriond 2004 result:  Better theoretical understanding.  Twice the amount of data.  Better b-tagging.  We believe we have the (almost) state of the art phenomenological interpretation of our measurements.  Future:  b-tag combination  Neural Network