# Presentation: 715813

-   Exclusive Bs Reconstruction (hep-ex/0510034)
-   Inclusive Ds Measurement (hep-ex/0508047)

- Y(5S) Results from CLEO

**Victor Pavlunin**** **
**Purdue University**
**CLEO collaboration ****PANIC-2005**

## 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 Bs* *physics at a high luminosity *e**+**e*** collider.

## 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.

***E******CM ******(GeV)***

***Curve: UQM***
***Data:   CLEO***

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

## 
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:

- 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:

- Overview of the Exclusive Method

- MC

## Backgrounds

- 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

## 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/*****

- DATA

- DATA

-  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)

## Bs modes with a Ds(*)-

- 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):

-  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

- B0 branching fractions:

## 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

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

## Overview of the Inclusive Method

- Ds mesons are expected to be produced in Bs decays more copiously than in B decays (PDG):
-  B(Bs  Ds* **X*) = (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).

## Ds spectra at the Y(4S) and the Y(5S)

- 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

## 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**).

## 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:

## Additional Slides

## 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 ~ 90*K** *of 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)

## A Signal Event

*** **-*

***+*

*K**-*

*K**+*