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Search for h b in two-photon collisions with L3 Detector at LEP

Search for h b in two-photon collisions with L3 Detector at LEP. Carmen Palomares CERN On behalf of L3 Collaboration. The Charmonium System. _ cc. Mass. The Bottomonium System. ---- Uncertain states Based on charmonium system h b meson is expected. _ bb. Mass.

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Search for h b in two-photon collisions with L3 Detector at LEP

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  1. Search for hb in two-photon collisions with L3 Detector at LEP Carmen Palomares CERN On behalf of L3 Collaboration C.Palomares / ICHEP02

  2. The Charmonium System _ cc Mass C.Palomares / ICHEP02

  3. The Bottomonium System ---- Uncertain states Based on charmonium system hb meson is expected _ bb Mass C.Palomares / ICHEP02

  4. hb( ) 1S state, JPC 0-+not yet seen • Mass should be close to Υ(1S) mass (9.46 GeV) C.Palomares / ICHEP02

  5. Experimental expectations • High statistics of gg collisions at LEP II In L3 :Le+e- = 610pb-1 ,189 GeV < s < 209 GeV • Predicted cross-section: QCD Potential model  Ggg(hb)  0.5 keV (predictions for hc compatible with the measurements) s(e+e- e+e-hb) = 0.26 pb at <s> = 197 GeV hb decays: BR(4 charged particles) ~ 3%  5 expected events A.Böhrer, Search for the hb meson, PHOTON 2001(eff = 100%) C.Palomares / ICHEP02

  6. Previous searches • In radiative decay of the Ύ(3S)  g hb (CUSB & CLEO) • CLEO(1994) BR(Ύ(3S)pphb) x BR(hb g hb) < 0.1%at 90% C.L. for hb mass range from 9.32 GeV to 9.46 GeV Phys. Rev. D49(1994) 40 • In two-photon collisions • ALEPH(2002) * Ggg(hb) x BR(4 charged part) < 48 eV at 95% C.L. 0 events found (background: 0.30±0.25) • * Ggg(hb) x BR(6 charged part) < 132 eV at 95% C.L. • 1 candidate m=9.30±0.04 GeV (background: 0.70±0.34) • Phys. Lett. B530 (2002) C.Palomares / ICHEP02

  7. Selection Studied decays 4 charged particles and 4 charged particles + po 6 charged particles and 6 charged particles + po Charged particles are p and/or K • Preselection: to define good tracks with pT>150 MeV • and e.m. cluster compatible with photons from po • (Eg> 80 MeV) • Selection: gg R n charged particles • n tracks (no other accidental tracks must be present) • S pT2 < 0.1 GeV2 • Reject: photon conversions, cut: m(e+e-)>50 MeV gg -> t+t-, cut:m(3p) > 1.9 GeV C.Palomares / ICHEP02

  8. 2 bumps from po (mass(gg) = po mass (105-165 MeV)) Data Selected 4 track +po Data Selected 6 track +po C.Palomares / ICHEP02

  9. Results Wggbetween 9 —10 GeV C.Palomares / ICHEP02

  10. 4 charged particles C.Palomares / ICHEP02

  11. 6 charged particles C.Palomares / ICHEP02

  12. 6 charged particles + po C.Palomares / ICHEP02

  13. Invariant mass distribution 4 charged particles + po 4 charged particles 1 candidate C.Palomares / ICHEP02

  14. Invariant mass distribution 6 charged particles 6 charged particles + po 1 candidate 1 candidate C.Palomares / ICHEP02

  15. Invariant mass distribution All channels combined C.Palomares / ICHEP02

  16. Invariant mass of the candidates Average reconstructed mass of the most significant candidates: M= 9.7 ± 0.3 GeV * * Mass resolution due to detector effects ~ 300 MeV p/K misidentification ~ 50 MeV C.Palomares / ICHEP02

  17. Possible Interpretations • The observation is found to be compatible with • the background expectation (expectation 1.3) • If we assume the production of hb resonance • in the invariant mass range 9-10 GeV: Upper limits on Ggg(hb)xBR: Ggg(hb) x BR(4 charged part.) < 0.3 keV Ggg(hb) x BR(4 charged part. + po) < 0.5 keV Ggg(hb) x BR(6 charged part.) < 0.4 keV Ggg(hb) x BR(6 charged part. + po) < 1.4 keV At 95% of C.L Assuming the same BR for each channel: Ggg(hb) x BR(all channels) < 0.2 keV at 95% of C.L. C.Palomares / ICHEP02

  18. Conclusions • We find 3 candidates in the Wgg range 9-10 GeV • They are compatible with background (1.3 events) The observation is also compatible with a signal. • The analysis will be slightly improved to increase the sensitivity C.Palomares / ICHEP02

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