1 / 17

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).

oona
Télécharger la présentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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-

More Related