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Exclusive B s Reconstruction ( hep-ex/0510034 ) Inclusive D s Measurement ( hep-ex/0508047 )

Y(5S) Results from CLEO. Exclusive B s Reconstruction ( hep-ex/0510034 ) Inclusive D s Measurement ( hep-ex/0508047 ). Victor Pavlunin Purdue University CLEO collaboration PANIC-2005. Introduction (1).

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Exclusive B s Reconstruction ( hep-ex/0510034 ) Inclusive D s Measurement ( hep-ex/0508047 )

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  1. Y(5S) Results from CLEO • Exclusive Bs Reconstruction (hep-ex/0510034) • Inclusive Ds Measurement (hep-ex/0508047) Victor Pavlunin Purdue University CLEO collaboration PANIC-2005

  2. Introduction (1) • The Y(5S) resonance was discovered by CLEO and CUSB collaborations operating at CESR in 1985. • The Y(5S) resonance is massive enough to decay into the following channels: • No evidence for Bs production at the Y(5S) was found using 116 pb-1 of data collected in 1985. • The three channels with Bs mesons are in the focus of two CLEO III analyses using 0.42 fb-1 of data collected recently at the Y(5S). • Knowledge of Bs production at the Y(5S) is essential for assessing the potential of Bsphysics at a high luminosity e+e collider.

  3. Introduction (2) • Two papers exist that describe the hadronic cross section above the Y(4S) resonance: • CLEO: PRL 54, 381 (1985) • CUSB: PRL 54, 377 (1985) • The cross section above the Y(4S) resonance is described well by the Unitarized Quark Model (S.Ono et al., Phys.Rev.D 34, 186 (1986)). • The model predicts: • Y(5S)  B* B* or Bs* Bs*, • The Bs cross section is about 1/3 of the total cross section. • (e+ e-  Y(5S)) ~ 0.35 nb • Using these predictions, we expect about 100K of Bs mesons in the 0.42 fb-1data sample. Curve: UQM Data: CLEO ECM (GeV)

  4. EXCLUSIVE Bs RECONSTRUCTION (hep-ex/0510034; submitted to PRL)

  5. Overview of the Exclusive Method • An extension of B meson reconstruction technique used at the Y(4S) is employed to reconstruct Bs mesons at the Y(5S): • Continuum background suppression variables • Three decay channels of the Y(5S) to Bs mesons are possible: • Decay channel 1: • Decay channel 2: • Decay channel 3: MC

  6. Backgrounds The center of the signal band for Bs mesons The center of the signal band for ordinary B mesons • The Y(5S) resonance can decay into a variety of states with ordinary B mesons: • The continuum (e+e-  qq) background is large: • Bs decay modes are poorly known. MC

  7. Bs modes with a J/ • Search for very clean modes having very large S/B ratio. The best mode to start with is BsJ/ . The search is also made for BsJ/  and BsJ/ ’. • The J/ is reconstructed in the  and ee channels. The following channels are used for other particles:   KK,   ,   ()+-. • Expect to find only 2-3 signal events, assuming branching fractions similar to those for B mesons. In the Y(5S) data, we find: 4 events in the signal box for Y(5S) Bs* Bs*: 3 events in Bs J/ 1 event in Bs J/ • Using data taken at other energies, the level of non-Bs background is found to be  0.08 events at 68% CL in the Bs*Bs* signal region. • The Poisson probability for 0.08 events to fluctuate to 4 events or more is PI  1.6  10-6 • M(Bs*)=5.4150  0.0018(stat) (GeV) DATA DATA

  8. Bs modes with a Ds(*)- • The choice of Bs Ds(*) / and the four Ds modes listed above is motivated by the difficulty of background modeling • MC predicts that a total of 10-14 events can be reconstructed in these channels • In the Y(5S) data we find 10 signal events (including background): B0 branching fractions: • Using the events in the sidebands on the search plane, the level of background is found to be  1.8 events at 68% CL in the Bs*Bs* signal region. • The Poisson probability for 1.8 events to fluctuate to 10 events or more is PII  1.9  10-5 • M(Bs*)=5.4129  0.0012(stat) (GeV) DATA DATA

  9. Results for the Exclusive Bs Reconstruction • PI and PII are combined to obtain an overall probability for a background fluctuation: P  8  10-10 (~6.1) • All signal events correspond to Bs*Bs* production. We set the following limits: and • Relating Bs branching fractions to B branching fractions with contributions from the same quark-level diagrams and assuming SU(3) symmetry, we find: which is consistent with the theory (UQM): 1/3 of 0.35 nb. • The mass of the Bs* meson is measured to be

  10. INCLUSIVE Ds MEASUREMENT (hep-ex/050847; submitted to PRL)

  11. Overview of the Inclusive Method • Ds mesons are expected to be produced in Bs decays more copiously than in B decays (PDG): • B(Bs DsX) = (94  30)% • B(B  Ds X) = (10.5  2.6)% Main Analysis Steps: • Measure Ds yields (Ds  +, K+K-) in bins of x = |PDs|/Ebeam in the continuum, Y(4S) and Y(5S) data. • Measure B(Y(4S)  DsX) and B(Y(5S)  DsX) by subtracting properly scaled and normalized continuum yields from the Y(4S) and Y(5S) yields. • Extract B(Y(5S)  Bs(*)Bs(*) )from the measured B(Y(4S)  DsX) and B(Y(5S)  DsX).

  12. Ds spectra at the Y(4S) and the Y(5S) • The plots show the continuum subtracted and efficiency corrected Ds yields at the Y(4S) and Y(5S). (No Ds branching fraction correction was applied to be above plots.) • Using B(Ds) = (4.40.5)% [PDG+BABAR], CLEO finds: Ds spectrum Ds spectrum

  13. Results for the Inclusive Ds Method • The plot shows an excess in the Ds production at the Y(5S) over that at the Y(4S). The excess is interpreted as evidence for the Bs at the Y(5S). • From B(Y(4S)DsX)) and B(Y(5S)DsX)), we obtain a model dependent estimate: • The largest sources of the systematic uncertainty are • the uncertainty associated with the luminosity measurements • the error from the uncertainty in B(Ds).

  14. Summary • Using full reconstruction, we have observed the Bs meson at the Y(5S) energy. • Relating Bs branching fractions to B branching fractions with contributions from the same quark-level diagrams and assuming SU(3) symmetry, we find: • We have established that Bs production proceeds predominantly through the creation of Bs*Bs* pairs: and • The mass of the Bs* meson is measured to be • In a separate analysis, using inclusive Ds measurements at the Y(4S) and Y(5S), we find:

  15. Additional Slides

  16. The Data Sample and CLEOIII Detector • The Y(5S) data sample: 0.42fb-1 collected with the CLEO III detector in 2003: • if ( e+e- Bs(*)Bs(*) ) ~ 0.1 nb, expect ~ 90Kof Bs mesons in 0.42 fb-1 • Background from B mesons is studied using the ON Y(4S) CLEO III data • The continuum (e+ e-  qq) background is studied using the OFF Y(4S) CLEO III data and data from a b scan (11.2 – 11.4GeV)

  17. A Signal Event +  - K+ K-

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