Victor Pavlunin

1

Y(5S) Results from CLEO

• Results from four CLEO Y(5S) analyses
• Exclusive Bs and B Reconstruction at the Y(5S)
• Inclusive Ds and ? Production at the Y(5S)

Victor Pavlunin on behalf of the CLEO
Collaboration DPF-2006
2
References

• Exclusive measurements
• Observation of Bs Production at the Y(5S)
  Resonance, (CLEO collaboration) PRL 96, 022002
  (2006)
• Measurements of the Exclusive Decays of the
  Y(5S) to B Meson Final States and Improved Bs
  Mass Measurement, (CLEO Collaboration) PRL 96,
  152001 (2006)
• Inclusive Measurements
• Evidence for Bs()Bs() Production at the
  Y(5S), (CLEO collaboration) PRL 95, 261801
  (2005). Includes a measurement of Ds production
  at the Y(5S)
• Measurement of B (Y(5S) ? Bs()Bs()) Using ?
  Mesons, (CLEO Collaboration) hep-ex/0610035.
  Submitted to PRD. Includes a measurement of ?
  production at the Y(5S)

3
Y(5S) Data Samples

• CLEO I (1985) 0.12 fb-1
• CLEO III (2003) 0.42 fb-1
• BELLE (2005) 1.9 fb-1
• BELLE (2006) 20 fb-1
• BABAR has not run at the Y(5S)

The topic of this talk
Note ECM are different by several MeV for
different data sets
4
CESR and CLEO

• The CLEO experiment is located at the Cornell
  Electron Storage Ring (CESR) operated in the
  region of the Upsilon resonances for over 20
  years.
• In 2003, we started collecting data at the
  ?(3770). Before that, we took a short run at the
  Y(5S).

• The CLEO detector was developed for B physics at
  the Y(4S). The CLEO-III configuration
• B-field 1.5 T
• Gas (drift chamber) He and C3H8
• Tracking 93 of 4?, ?P/P?0.6 for a 1.0 GeV
  track
• Hadron particle ID RICH (80 of 4?) and dE/dx
• E/M crystal calorimeter 93 of 4p, ?E/E ? 2.0
  (4.0) for a 1.0 GeV (100 MeV) photon
• Muon prop. chambers at 3, 5 and 7 ?I .

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Introduction Bs at the Y(5S) (1)

• The Y(5S) resonance was discovered by CLEO and
  CUSB at CESR in 1985.
• The Y(5S) is massive enough to decay into the
  following channels
• No evidence for Bs production at the Y(5S) was
  found in 116 pb-1 collected in1985.

6
Introduction Bs at the Y(5S) (2)

• There are two papers that measure 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) is described
  well by the Unitarized Quark Model (S.Ono et al.,
  Phys.Rev.D 34, 186 (1986)).
• The UQ model predicts
• Y(5S) ? BB or BsBs,
• The Bs cross section is ? 1/3 of the Y(5S) cross
  section.
• ?(e e- ? Y(5S)) ?? 0.35 nb

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Y(5S) Cross Section Measurements

• Count hadronic events at the Y(5S)
• Subtract the continuum using data taken below the
  Y(4S)
• Scale by ratios of luminosities and Ecm2
• Luminosity ratio is a significant source of
  systematic errorsince s(Y5S) 0.1s(continuum)
  and the continuum data are taken 300 MeV below
  the Y(5S)
• Results
• sY(5S)(0.3010.0020.039) nb
• Consistent with theoretical predictions

Ref hep-ex/0610035
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• Exclusive B(s) Reconstruction at the Y(5S)

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Overview of the Method (1)

• An extension of B reconstruction technique used
  at the Y(4S) is employed to reconstruct Bs mesons
  at the Y(5S)
• Continuum background suppression variables (e.g.,
  R2 H2/H0)
• Three decay channels of the Y(5S) to Bs mesons
  are possible
• Decay channel 1
• Decay channel 2
• Decay channel 3

MC
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Overview of the Method (2)

• The Y(5S) can decay into a variety of states with
  ordinary B mesons
• Large background from the continuum (ee- ? qq)

The ON Y(4S) data are used to model B bkg in the
Bs analysis
The OFF Y(4S) and ?b data are used to model the
continuum bkg
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Bs modes with a J/?

• Search for very clean modes having very large S/B
  ratio Bs?J/? ?, J/? ? and J/? ?.
• The J/? is reconstructed in the ?? and ee
  channels. The following channels are used for
  other particles ? ? KK, ? ? ??, ?? ? ?(??)??-.
• Expect to find few 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/???

• The level of non-Bs background is ? 0.08 events
  at 68 CL in the BsBs signal region.
• The 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
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A Signal Event
?
? -
K
K-
13
Bs modes with a Ds()-
B0 branching fractions

• Bs ? Ds() ?/? with Ds modes given in the
  tables
• MC predicts that a total of 10-14 events can be
  reconstructed in these channels
• In the Y(5S) data we find 10 signal candidates
  (including background)

• The level of background is ? 1.8 events at 68
  CL in the BsBs signal region.
• The 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
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Results for Bs() Production

• PI and PII are combined to obtain an overall
  probability for a background fluctuation P
  (PIPII)(1-ln(PIPII)) P ? 8 ? 10-10 (?6?).
• All signal events correspond to BsBs
  production. We set the following limits (90 CL)
• and
• Relating Bs branching fractions to B branching
  fractions, we find
• which is consistent with the theory (UQM)
  1/3 of 0.30 - 0.35 nb of the total Y(5S)
  cross-section.
• The mass of the Bs meson is measured to be

for more information see PRL 96, 022002 (2006)
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B modes with J/? and D()

• Modes B ? D() p / r and B ? J/y K() (in total
  25 modes)

Data
MC
Mbc (GeV)
?E (GeV)
Note the non-standard definition of ?E in these
plots (should have the opposite sign)
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Results for B() Production

• BB is again dominant (consistent with
  models)
• ?(BB)/?(BBX) (74158)
• ?(BB)/?(BBX) (2493)
• ?(BB)/?(BBX) lt 22 at 90 CL

In combination with
gives
consistent with theory and exper.
for more information see PRL 96, 152001 (2006)
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• Inclusive Ds and ? Measurements at the Y(5S)

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Overview of the Inclusive Method

• The method relies on the fact that Ds (and ?)
  mesons are produced more copiously in Bs decays
  compared to B decays.
• Main Analysis Steps
• Measure Ds yields (Ds ?? ?, ??KK-) 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 fs according to the equation above and
  account for systematic errors.

Model dependent estimate B(Bs ? Ds X) (92 ??
11) B(Bs ? ?X) (15 ?? 3)
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Results of the Inclusive Ds Method

• CLEO inclusive DS yields for x lt 0.5 and R2lt0.25

• The largest sources of the systematic uncertainty
  are
• the uncertainty associated with the luminosity
  measurements
• the uncertainty in B(Ds???).

for more information see PRL 95, 261801 (2005)
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Results of the inclusive f method

• CLEO inclusive f yields for x lt 0.5 and R2lt0.25

Y(5S)
Y(4S)
continuum
Y(4S)
Branching Fraction
Y(5S)
X P/Ebeam
for more information see hep-ex/0610035
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Summary and Conclusions

• Using 0.42 fb-1 of data at the Y(5S) resonance,
  we obtain the following results
• First observation of BS production at the Y(5S)
• and limits and
• First study of B production at the Y(5S)
• 
  
• Determination of
• Estimates of Bs production using inclusive
  measurements of Ds and ? production at the Y(5S)
  (model dependent)
• Ds production
• ? production
• Belle (using the 1.9 fb-1 sample) confirms CLEO
  results

The Y(5S) resonance is a significant source of
Bs mesons for a high luminosity ee- collider
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• Additional Slides

23
Model estimate of B(BS ? fX)

• Use CLEO-c inclusive yields (hep-ex/0610008) for
• B(Do ? fX)
  (1.00.100.10)
• B(D ? fX)
  (1.00.100.20)
• B(DS ? fX)
  (15.12.11.5)
• Demonstrate that majority of ? mesons arise from
  B ? D ? and B ? DS ? ? .
• Predict B(BS ? fX) (14.92.9)
• Consult hep-ex/0610035 for details