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Evidence for the h c

‘. Evidence for the h c. Sookyung Choi Gyeongsang University & Stephen L. Olsen University of Hawaii. ‘. Expected mass of the h c. 3 D c3. 3 D c1. 3 D c2. cc level diagram:. y ’. ??. D ’=???. 1 h 1 ?. ‘. h c. c c0,1,2. D =117 MeV. J/ y. h c. potential model:. close to

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Evidence for the h c

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  1. ‘ Evidence for the hc Sookyung Choi Gyeongsang University & Stephen L. Olsen University of Hawaii

  2. ‘ Expected mass of the hc 3Dc3 3Dc1 3Dc2 cc level diagram: y’ ?? D’=??? 1h1? ‘ hc cc0,1,2 D=117 MeV J/y hc potential model: close to they’ expect M(hc’)  3.62~3.64 GeV

  3. Expected widths/decay modes • Similar to hc • narrow (but not like the J/y) • 10< G< 20~30 MeV • ~same decay channels • Search in a channel with strong hc signal but absent in y’ decays

  4. Search in hc’KSK±pchannel • Br(hcK0K-p+) is respectable (2%) • all charged particles (s(DE) 13 MeV) • low combinatoric background • noy’ background (Br(y’K0K-p+)<10-4 • Br(y’K0Kp)<Br(J/yK0Kp)/30

  5. Event selection Use expts 7 thru 13; b20010523_0725 library • Skim Hadron B: • R2<0.35 • 2chrgd K’s; 1chrgd p; 1KS • Mbc>5.2 GeV; |DE|<0.2 GeV • |cosqthrust| < 0.9 between B and rest of evnt • all candidate tracks constrained to IP

  6. Charged kaon selection • K/p-id: atcpid(3,1,5)>0.6 • p/K-id: atcpid(3,1,5)<0.95 • m veto: m_likelihood < 0.9 • e veto: eid_prob(3,-1,5)<0.9 • CDC hits: Nax8 ; Nster3 • vertex : dr<0.3 ; |dz|<2.2

  7. Charged pion selection • K/p-id: atcpid(3,1,5)<0.4 • p/p-id: atcpid(3,1,5)<0.9 • e veto: eid_prob(3,-1,5)<0.95 • CDC hits: Nax8 ; Nster3 • vertex : dr<0.3 ; |dz|<2.2

  8. KSp+p- selection • flight-length > 0.3 • |Df| <0.2 • |Mpp – MKs|< 12 MeV • if both trks have SVD hits: • Zdist<1.2 • otherwise: • Zdist<10 ; dr>0.015 ; |Df|<0.1

  9. continuum-bkgd suppression • Fisher • 5 SFW moments • cosqthrust • S|pt|particles with qthrust>60o • cosqB  B candidate production angle L = PDF( fisher ) x PDF(cosqB)

  10. Fisher SFW cosqthrust S|pt| use: R 2,4 & R 2,3,4 major maj minor

  11. Likelihood Ratio Fisher cosqB cut LR = Lsig/(Lsig+ Lqq)

  12. K* and charm veto • 0 -+ 1–-- 0-+ suppressed by an angular • hc  K* K momentum barrier • backgrounds commonly have K*’s •  veto events with K*: • |MKp – M K* |>50 MeV • also veto events with charm: • |MKp – M D |>10 MeV • |MKKs – M Ds |>10 MeV

  13. Look at K KsK+p- combinations Select events in the DE Mbc signal box

  14. M(KSK+p-) for signal-box evts (B+ K+ KS K+p- + B0KS KSK+p- combined) 1.5-entries/evnt 2-entries/evnt 100 evts 38 evts ? 28 evts “hc’ ” properties • M = 3653 ± 9 MeV • G= 30 +44 MeV • S = 3.8s -?? NB: N(y’KSKp)<N(J/yKSKp)/30 1evt

  15. Do slice fits: 3.55 GeV 6±4 evts 3.60 GeV 13± 4 evts 26±6 evts 3.65 GeV (S=5.2s) 16± 5 evts 3.70 GeV 4 ± 4 evts 3.75 GeV

  16. Slice fit results BW with M =3653 & G = 30 MeV; not a fit! Poor agreement maybe due to the coarseness (50MeV) of the slice-fit bins

  17. Summary 3625<MKSKp<3675 MeV • We observe a 5.2s signal for BK KSK+p- near 3650 MeV. • This cannot be the y’ • Most likely this is BKhc’ with: • Mhc’ = 3653 ± 9 MeV • Ghc’ = 30 +44 MeV • This disagrees with the Crystal-Ball result Mhc’=3594±5 MeV but agrees with potential models. -?? Mbc

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