Higgs searches and Top properties at CDF Takasumi

Higgs searches and Top properties at CDF Takasumi Maruyama (Univ. of Tsukuba) for CDF collaboration n Contents ¨ Direct n n Higgs searches Direct SM Higgs searches Direct Higgs searches for MSSM ¨ Recent n results of Top physics (except mass) ttbar resonance search, cross section, lifetime, etc ¨ Summary

Integrated luminosity (/fb) Standard Model Higgs Search • Electro-weak precision data prefer light SM Higgs (as shown in previous talk, blue-band plot shown above) (* SUSY requires light Higgs. ) • Te. V studies in 1999 and 2003 predicted: • 2 fb-1: 95%CL exclusion at m. H=115 Ge. V/c 2 • 5 fb-1: 3 evidence at m. H=115 Ge. V/c 2 • If Higgs mass is small, Te. V could compete to LHC.

SM Higgs Boson Production and Decay @ Te. V Decay Branching Ratios Production Cross-Sections bb H 0 bb Z u d u Z* e H 0 bb e u d u W+ WW e+ e W+ d u u

Direct SM Higgs Search Associate production (search for Mbb peak) CDF (and D 0) have started the hunt (WW* result updated from LP 05) Direct production (phi of dilepton)

SM Higgs Searches at the Tevatron: WH l bb (Y. Ishizawa (Univ. of Tsukuba) Ph. D thesis (2005)) Select events with • Identified electron or muon ET>20 Ge. V, isolated • Missing ET > 20 Ge. V • Two jets with | | < 2. 0, ET>15 Ge. V. • Veto extra jets, Z 0, cosmics, conversions, extra isolated tracks • At least one b-tag control signal region control region All requirements except # jets. 1, 3 & 4 -jet bins are control samples for normalizing backgrounds.

WH l bb Channel: Before and After the B-tag Before b-jet identification; there are different background composition fraction, but gives higher statistics test !!

WH l bb Channel: Observed and Expected Limits

The gg H W+W- Channel Signal Process: Dominant background: qq W+W- • Interesting Angular Correlation due to Scalar nature of Higgs Boson • Different from SM W+W- bg decay angular correlation! W+ W- e+ e-

gg H W+W- Channel Discriminant Variable • • • Two leptons, Each with ET>20 Ge. V Jet Veto to remove t-tbar Missing ET>25 Ge. V Z veto mll<m. H/2 -- note: background depends on test mass Acceptance is ~0. 4% [including Br 2(W l )] for m. H>160 Ge. V assuming 160 Ge. V/c 2

Summary plot for direct SM Higgs searches K. Kobayashi (Univ. of Tsukuba) Ph. D (2005) Same colors correspond to same decay mode !! (We have 3 lines, for CDF, D 0 and theory)

Ratio of Limits to SM Note; all are normalized to theoretical cross section

So How Do We Get There? ? Luminosity Equivalent (s/ b)2 Improvement Start with existing channels, add in ideas with latest knowledge of how well they work (under studying) WH l bb ZH llbb Mass resolution 1. 7 Continuous b-tag (NN) 1. 5 Forward b-tag 1. 1 Forward leptons 1. 3 1. 0 1. 6 Track-only leptons 1. 4 1. 0 1. 6 1. 75 1. 0 WH signal in ZH 1. 0 2. 7 1. 0 Product of above 8. 9 13. 3 7. 2 CDF+DØ combination 2. 0 17. 8 26. 6 14. 4 NN Selection All combined Expect a factor of ~10 luminosity improvement per channel, and a factor of 2 from CDF+DØ Combination

Expected Signal Significance CDF+DØ vs Luminosity It’s possible to be lucky or unlucky! per experiment m. H=115 Ge. V assumed per experiment

Non-SM Higgs: A bb and A n Supersymmetry (MSSM): ¨ n 2 Higgs doublets => 5 Higgs bosons: h, H, A, H± High tan : A degenerate in mass with h or H ¨ Cross sections enhanced with tan 2 due to enhanced coupling to down-type quarks ¨ Decay into either or bb: ¨ n n n BR(A ) ≈ 10%, BR(A bb) ≈ 90% Exact values depend on SUSY parameter space Experimentally: • C. Balazs, J. L. Diaz-Cruz, H. J. He, T. Tait and C. P. Yuan, PRD 59, 055016 (1999) ¨ • M. Carena, pp Ab+X and bbb+X (D 0 has result)(1999) S. Mrenna C. Wagner, PRD 60, 075010 S. Mrenna and+X C. Wagner, PRD 62, 055008 (2000) ¨ • M. Carena, pp A+X (CDF has result)

CDF search for A->tt using Mvis Invariant mass of visible + - decay products plus Missing ET

Limits on Cross-Section * Branching Ratio = h 0, A 0 or H 0 or a sum of states with similar masses

Interpretations in MSSM Benchmarks | | = 200 Ge. V M 2 = 200 Ge. V Mgluino = 0. 8 MSUSY = 1 Te. V, Xt = √ 6 MSUSY (mhmax) MSUSY = 2 Te. V, Xt = 0 (no-mixing) D 0 searched A->bb. X mode. CDF new result A->bb. X coming soon LEP Limits – mtop=174. 3 Ge. V for historical reasons.

Tau Channel Prospects for the Future

Top Quark Properties W helicity Top Mass • • • Understanding on top quark properties has been largely improved by much higher statistics than Run 1 (~7 times at this winter conferences) Any significant deviation from standard model prediction could indicate new physics. Recent hot topics (pink boxes) are shown at this talk l+ Top Width Production cross-section Resonance production Top lifetime W+ CP violation Top Charge p t Production kinematics ttbar Spin correlation Anomalous Couplings b X _ p _ t _ b q Rare/non SM Decays W- Branching Ratios |Vtb| _ q’

Top Production & decay Cacciari et al JHEP 0404: 068 (2004) Kidonakis et al PRD 68 114014 (2003) Top pairs via strong interaction 85% qq 15% gg Top decays to W+b by ~100% in SM mt (Ge. V) Te. Vatron √s=1. 96 Te. V -PDF NLOσ(pb) +PDF 170 6. 8 7. 8 8. 7 175 5. 8 6. 7 7. 4 180 5. 7 6. 3

Top Pair Production Cross Sections • Cross section is sensitive to both the production and decay anomaly. • The difference of the xs with different decay mode is sensitive to the new physics such as charged Higgs. Cross section is old but also fresh topic. • CDF measure this with various decay mode and techniques (consistent with SM)

Does something new produce ttbar? n n This is more direct exotic search on ttbar production. Search for new massive resonance decaying to top pairs such as top-color Z’ Using lepton+>=4 jets (nobtag) sample. Likelihood incorporating LO matrix element was used to reconstruct Mttbar. ¨ Constraint top mass = 175 Ge. V/c 2 ¨ n Fix most of SM backgrounds to expected rate ¨ Use theory prediction of 6. 7 pb for SM top pair production Interesting fluctuation, ~500 Ge. V @ 319 pb-1 (2005 summer)

New results for Mttbar (with 680 pb-1) • Using the 682 pb-1, same analysis was done !! (same selection, same mass fitting). Note; previous 318 pb-1 data is the sub-sample of the full dataset. • No excess was observed at this time. (left figure) • limit on a narrow leptophobic Z’ ( Z’=1. 2%MZ’): MZ’>725 Ge. V at 95%CL

kinematics for ttbar events • So far, Leading-Order MC (such as PYTHIA, HERWIG) describes kinematics of the ttbar rich data sample well. • For example, plots below show PT(ttbar), and PT(top/anti-top) using ttbar kinematic fitter. (same one as the mass analysis) • This is the start point of the precision measurement for top quark

Top Lifetime (1) n n SM top has ~10 -24 s Measuring lifetime ¨ ¨ n Helps in confirming SM top Sensitive to production mechanism from long lived particles CDF uses Lepton+Jets channel with b jet tagged ¨ Measure lepton impact parameter (d 0) Signal template n Backgrounds: ¨ ¨ n Prompt: W+jets, Drell-Yan, Diboson Displaced lepton: W(Z) decaying to t, Semileptonic b, c decays, photon conversion (failing filter) Calibration: use DY near Z resonance to get d 0 resolution

Top Lifetime (2) n n Observed data prefer 0 m lifetime (left figure) Interpretation to 95% CL. ¨ Using ¨ c top Feldman-Cousin limit (right plot) < 52. 5 m ( <1. 75 x 10 -13 s) at 95% C. L.

Summary (1) • We have preliminary searches in a great variety of channels, most with ~300 pb-1 of data analyzed for 2005. (expect ~1000 pb-1 results in this summer) SM Higgs Searches MSSM Higgs Search • The sensitivity is currently insufficient to test for presence or absence of a SM Higgs boson but we will get more data and improve our channels with wellunderstood techniques. • We have tools to estimate the sensitivity, also to combine them • MSSM Higgs searches are getting exciting.

Summary (2) n n Top physics are now in the precision measurement phase. (more than ~7 times statistics of CDF run I in this winter. ) In this summer, we will have ~1000 pb-1 results Trying to check many of top properties. So far we have no obvious anomalies against SM in ttbar rich sample. If we have physics beyond Standard Model related to top physics, it could be possible to observe it before LHC.

Backup slides

SECVTX B-tag efficiency • s/b tradeoff: Leptons & Missing ET are distinctive; real backgrounds have two b quarks. Single-tag is enough. Future: Combine single and double-tag analyses, do a tight-loose tag. • Jet-probability tags are available but not yet used in Higgs analyses -- more complication for estimating mistags Mistag rates typically ~0. 5% for displaced vertex tags

NN Extension of SECVTX B-tag non-top backgrounds (single-top) Neural Network after Sec. Vtx ¼ 50% Signal: single-top, Approach: Background: • require Sec. Vtx • improve purity by including: • long lifetime (also by Sec. Vtx) • decay length of Sec. Vtx • D 0 of tracks • large mass • mass at Sec. Vtx • p. T of tracks w. r. t jet axis • decay multiplicity • # of tracks • decay probability into leptons • # of leptons , Mistags (mixed acc. to background estimation)

Dijet Mass Resolution Improvements • Larger jet cones • track-cluster association • b-specific corrections • Advanced techniques (NN, “hyperball”) Target: 10% resolution for two central jets

Forward Electrons Currently plug electrons only used as a Z 0 veto in the lvbb channel. Wbb Phoenix electrons give 25% extra signal 40% extra background WH (s/b)forw = 0. 6(s/b)central Not optimal to add -- treat as separate channel!

Improvement example: Lepton Selection n Forward leptons: factor 1. 3 ¨ n Current analyses use only up to | |<1. 1 Electrons: ¨ CDF: n n n Forward electrons used already by other analyses, e. g. W charge asymmetry Up to | |<2. 8 Central electrons: recently improved efficiency from 80% to 90% Factor 1. 34 in acceptance W electron charge asymmetry PRD 71, 051104 (2005) Muons: 　 CDF: 　　uses only up to | |<1. 0 can be extended since we have detector. ¨ ~75% efficiency 35 < ETelectron < 45 Ge. V

EJet Scale & Resolution: Status / Improvements Jet energy scale uncertainty: • precision measurements (Mtop), searches • now ~2. 5% uncertainty for jets in top decays • further improvements: • generators, higher order QCD • better scale for ET > 100 Ge. V region • complete by end of this year 0. 2 • currently 17%, goal 10 -11% • further improvements: • combine track, calorimeter Info: 2% • expand cone size: 2% • b-jet specific corrections: 1 -2% • sophisticated algorithms: 1 -2% • complete by spring 2006 Raw 1. 0 0 Jet energy resolution: Mhiggs = 120 Ge. V 0 0. 2 50 100 150 200 250 Scale Corrections Resolution Improvements 1. 0 0 0 50 100 150 200 H --> bb mass (Ge. V) 250

The Higgs Bosons of the MSSM • Two Complex Higgs Doublets! Needed to avoid anomalies. • Five Degrees of Freedom plus W+, -, Z 0 longitudinal polarization states • Five scalars predicted: h, H, A, H+, H • CP-conserving models: h, H are CP-even, A is CP-odd • Independent Parameters: • m. A • tan = ratio of VEV’s • • MSUSY (parameterizes squark, gaugino masses) • mgluino (comes in via loops) • Trilinear couplings A (mostly through stop mixing) • Map out Higgs sector phenomenology – variations of all other parameters correspond to a point in this space • And a real prediction: mh <~ 135 Ge. V Let’s test it!

Couplings of MSSM Higgs Bosons Relative to SM W and Z couplings to H, h are suppressed relative to SM (but the sum of squares of h 0, H 0 couplings are the SM coupling). Yukawa couplings (scalar-fermion) can be enhanced

Higgs Boson Production Mechanisms + 0 t 0 b Amplitude 1/tan suppressed! b 0 Amplitude tan enhanced! And many other diagrams At high tan , (h, A+X) tan 2 b Amplitude tan (low tan and SM case: cross-sections too small to test with current data. ) enhanced!

Higgs Boson Production and Decay at High tan • Interesting feature of many MSSM scenarios (but not all!): [mh , m. H] m. A at high tan (most benchmark scenarios. . ) • At leading order, (A 0 bb) and (A 0 + -) are both proportional to tan 2. • Decays to W, Z are not enhanced and so Br. falls with increasing tan (even at high m. A) • Br(A 0 bb) ~ 90% and Br(A 0 + -) ~ 10% almost independent of tan (some gg too).

MSSM Higgs Searches Accepted by PRL, hep-ex/0508051 | | = 200 Ge. V M 2 = 200 Ge. V Mgluino = 0. 8 MSUSY = 1 Te. V, Xt = √ 6 MSUSY (mhmax) MSUSY = 2 Te. V, Xt = 0 (no-mixing) CDF Preliminary 310 pb-1

Update plan in near future n All updates aim to have 700~1000 pb-1 ¨ WH n Aiming to have results until this May ¨ ZH n ¨H n -> nu+nu+bbbar; Aiming to have results around summer ¨ ZH n -> l+nu+bbbar; -> ll+bbbar; They aim to have result in Spring/summer 2006 -> WW*; Spring/Summer 2006 CDF is very active to get new result !!