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DØ results on Higgs Search

DØ results on Higgs Search. Yuji Enari Brown University On behalf of DØ Collaboration Lake Louise Winter Institute 2007. SM Higgs boson. Gauge invariance: No mass term Mass of fundamental particles are given by Higgs boson From theory Missing part of SM SM higgs mass is light.

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DØ results on Higgs Search

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  1. DØ results on Higgs Search Yuji Enari Brown University On behalf of DØ Collaboration Lake Louise Winter Institute 2007

  2. SM Higgs boson • Gauge invariance: No mass term • Mass of fundamental particles are given by Higgs boson From theory • Missing part of SM • SM higgs mass is light From experiment: - MH > 114.4 GeV @95% CL search by LEP2 - MH < 166 (199) GeV @95% CL global EW fitting Higgs self-coupling diverges Center value = 85 + 39 – 28 GeV Allowed unstable vacuum Tevatron can explore the mass range of 115 < MH < 185 GeV Dzero results on Higgs Search Lake Louise Y.Enari

  3. SM Higgs search at Tevatron • Production 1. Gluon fusion (0.8 ~ 0.2 pb) 2. WH associated production (0.2~0.03pb) 3. ZH associated production (0.1~0.01pb) • Decay • mH < 135 GeV H  bb is dominant • mH > 135 GeV H WW Analysis Strategy mH < 135 GeV WH/ZH + H bb mH > 135 GeVGluon fusion + HWW Background top, Wbb, Zbb WW, DY, WZ Dzero results on Higgs Search Lake Louise Y.Enari

  4. Current Status of Higgs search at DØ SM MSSM Fermiophobic • Others • h++  tt, Htb, • tt(t H+b, H+cs) • H++  mm, ee Dzero results on Higgs Search Lake Louise Y.Enari

  5. DØ detector Tracker Solenoid Magnet protons 3 LayerMuon System Electronics Preshowers Multi purpose detector New silicon detector for improvement of b-jet ID Installed last spring Layer 0 Toroid & solenoid polarity flipped regularly ~equal exposure to 4 possible field configurations Dzero results on Higgs Search Lake Louise Y.Enari

  6. Improvement on b-tagging Lxy Secondary Vertex Primary Vertex d0 • Characteristic of b-quark • Lepton from semileptonic B decay (Br~10%) • Longer lifetime, t~1.6ps  Travel distance from PV ~ 1mm • Tagging Algorithms • Secondary vertex reconstruction • Impact Parameter based • NN tagger • Use these information as input of NN  33% gain with same fake rate of 0.5% Dzero results on Higgs Search Lake Louise Y.Enari

  7. Low mass SM Higgs: ZH  llbb e, m New result! fLdt = 920 / 840pb-1 Z q e, m • e : pt>15GeV, 2 loose electron • m : pt>15GeV, 2 loose muon Z Main BG: Z+jj, Z+bb b q H b Mass window e: -1.5s ~ 1.5s m: -1s ~ 2s After double NN b-tag Combine e and m, 1 tag + 2 tag Modified frequentist approach (CLs) from dijet mass distribution Dzero results on Higgs Search Lake Louise Y.Enari

  8. High mass SM Higgs: HWW e, m fLdt = 930-950 pb-1 g W t n H  Missing n g W Main BG: ggWW e, m • Two isolated high pT leptons + missing ET • ee, mm, em channel are considered. Can’t reconstruct H invariant mass  Use Angular correlation e+ W+ n No excess from BG exp in Df dist. n W- e- WW is daughter of scalar H. Leptons from W tend to have same direction Dzero results on Higgs Search Lake Louise Y.Enari

  9. Limits on SM Higgs production • Latest ZHllbb is not included in these limits. • New result of WHlnbb and ZHnnbb will be coming soon. Data/SM ~ 10 @ 115GeV Data/SM ~ 5 @ 160GeV Dzero results on Higgs Search Lake Louise Y.Enari

  10. MSSM Higgs t b f f • MSSM • Two Higgs doublets to avoid anomaly • 8 degrees of freedom – 3 (longitudinal pol. of W±,Z )  5 physical scalars (h, H, A, H±) • Search for f tt • Br(fbb) ~ 90%, Br(ftt)~10%  High QCD BG  l+had (17%x62%) Tau ID (hadronic t decay) • NN: 8 variables related to jet shape • Train NN each topology separately Performance: @ t’s pt=15GeV thn: 60% with 2% fake, • thp0n: 60% with 4% fake, • t3hn : 40% with 3% fake s ~ 1/tanb s ~ tanb f At high tanb(=Hu/Hd), s(h or H, A) is enhanced m+ n t+ f b n hadron MW < 20 GeV t - Dzero results on Higgs Search Lake Louise Y.Enari

  11. MSSM Higgs ftt New result! fLdt = 1000 pb-1 • ftt  mu+th • NN>0.9 • DRmt > 0.5 • MW < 20 GeV • Main BG • Z tt • QCD is well suppressed DATA: 1141 evt. MC : 1287 ± 130 evt. Eff(ftt) : 1.4% Observed events are fully consistent with expectation No excess ~ 140 GeV Dzero results on Higgs Search Lake Louise Y.Enari

  12. New limit on MA vs tanb New result with 1fb-1 • To maximize sensitivity NN output is used in the limit calculation NN input: Visible Mass, pT, pT (cal), pT (trk), hm, ht m t t Dzero results on Higgs Search Lake Louise Y.Enari

  13. New search: Fermiophobic Higgs hf hf W  ggg(g) X W/Z • Fermiophobic Higgs search with SM VVhf coupling: • LEP: e+e-  Zhf mhf > 105 GeV e+e-  Ahf mhf +mA > 160 GeV • TeV: qq  V  V+hf mhf > 82 GeV • There is still possibility in 2HDM tanb>1, mhf < 90 GeV, mH < 200GeV • Signature pp  hfH±  hfhfW± ggg(g) X pt1 >30 GeV, pt2 >20 GeV, pt3 >15 GeV q g hf q g VVhfcoupling mH = 150 GeV mhf = 50GeV W g u H hf g W hf g d g pt g (GeV/c) Dzero results on Higgs Search Lake Louise Y.Enari

  14. hf hf W  ggg(g) X New result fLdt = 1000 pb-1 Before applying HT cut • Additional selection HT > 25 GeV Observed Event : 0 ev Expected # of BG: 1.1 ± 0.2 ev Acceptance : 0.16 ± 0.03 MC: 3.5±0.6 Invariant mass of gg (GeV/c2) Limit: s = 25.3 fb @95%CL Mhf = 66GeV for mH < 100 GeV @ tanb =3 Mhf = 44GeV for mH < 150 GeV @ tanb =3 Mhf = 80GeV for mH < 100 GeV @ tanb =30 Mhf = 50GeV for mH < 150 GeV @ tanb =30 preliminary result Dzero results on Higgs Search Lake Louise Y.Enari

  15. Summary and Prospect • No excess yet observed in data from BG expectation. • Observed limit is getting close to SM expectation. • We are currently improving our analysis • bID performance much improved by using Neural Net • Optimization of selection • Use Event shape: NN, Matrix Element, etc… • Increased acceptance • Jet energy resolution • Reduce systematic uncertainty • Adding new channels • Combine with CDF • Increase statistics: 2fb-1 of data on tape, expect 4-8fb-1 by 2009. NOW is time for Higgs search at Tevatron! Stay tuned! Dzero results on Higgs Search Lake Louise Y.Enari

  16. Dzero results on Higgs Search Lake Louise Y.Enari

  17. Prospect • 4~8fb-1 will be available by 2009 Dzero results on Higgs Search Lake Louise Y.Enari

  18. Dzero results on Higgs Search Lake Louise Y.Enari

  19. MSSM parameter for f  tt Dzero results on Higgs Search Lake Louise Y.Enari

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