1. Upsilon Decays Helmut Vogel Carnegie Mellon University
for the CLEO Collaboration
FPCP 2006
Vancouver, BC
upsilon decay ('up-si-”l&n di-'kA). 1. decay of a bound bb state, decay of an unbound bb state to a bound bb state.

2. Motivation for Studying Bound State bb_
Test Lattice QCD – Masses, Transition Rates, ee, HF splittings
Decay Models –  via E1E1 gluons,  vs.  transitions
QCD & Potential Models – s, LS coupling, color octet/singlet
Comparison to charmonium -- radiative decays, e.g., (')
Correlation to B physics – inclusive '
Beyond SM tests – e.g., LFV via 
H. Vogel
FPCP 2006

3. The Renaissance in  Physics
CLEO II
CLEO III
CESR, Nov 2001 – Dec 2002:
* Dedicated (1S), (2S), (3S) runs
* fold increase in world supply
* State-of-the-art detector, CLEO III
B Factories, since 2000:
produce (nS), n=1,2,3 via ISR
(but have only recently begun to exploit them)
H. Vogel
FPCP 2006

4. The CLEO III Detector
H. Vogel
FPCP 2006

5. Recent and Hot News in Upsilon Decay (incomplete overview)
Photon Transitions from (2S) and (3S)
Decay of (1S) to Charmonium
Radiative Decays: (1S) →  h+ h- , (1S) →  (')
“Unusual” Hadronic Transitions within the Upsilon System
Precision Measurement of B and ee of (1S,2S,3S)
“Usual” (but intriguing) Dipion Transitions (CLEO, Belle, BaBar)
and more-- B , study of (5S), (1S) →  X, ... (sorry, not enough time!)
CLEO
H. Vogel
FPCP 2006

6. E1 Photon Transitions: n=1 and n=2
H. Vogel
FPCP 2006

7. Photon Transitions: Impact of E1 Results
Significant improvement in
precision (by now systematics
dominated)
Test relativistic corrections in
bb potential models (indeed
smaller in bb than in cc)
Verify spin dependence of E1
matrix element, (2J+1)(E)3
E1 transitions have large BRs --
copious production of P states
(not directly accessible
in e+e- collisions)
H. Vogel
FPCP 2006

8. Photon Transitions: the 13DJ State
First new Upsilon state in 20 years
First long-lived L=2 meson
below open-flavor threshold
Test of LQCD
H. Vogel
FPCP 2006

9. (1S) Decay to Charmonium: Motivation
Tests models of charmonium production
in gluon-rich environments
(cf. copious production of “prompt” J/
at the Tevatron)
Candidate Models:
* Color-Octet (Braaten & Fleming 1995)
* Color-Singlet (Li, Xie, & Wang 2000)
predict BR and J/ momentum spectrum
H. Vogel
FPCP 2006

10. (1S) Decay to Charmonium: Results
CLEO PRD 70 (2004)
B((1S) → J/+ X) = (6.4  0.4  0.6) x favors color-octet.
Momentum spectrum of J/'s is softer than predicted (FSI?)
Transitions to (2S) and c states are also observed.
H. Vogel
FPCP 2006

11. Radiative Decays: (1S) →  h+ h- (h = , K, p)
The hadron pair is produced in a
glue-rich environment --
Ideal source of glueballs (if they exist)
Probe two-gluon structure
Expected scaling from J/:
rates suppressed by ((qbmc)/(qcmb))2≈1/40
BF's suppressed by ≈1/25
Fit observed structure with relativistic,
spin dependent Breit-Wigner curves
Also studied the  final state
(no  continuum background)

bkgd
subtracted
H. Vogel
FPCP 2006

12. Radiative Decays, (1S) →  h+ h- : Results
CLEO PRD 73 (2006)
Confirm f2(1270) in  channel
Establish J=2 assignment
Observe f2'(1525) in KK channel; also J=2
BR = (10.2  0.8  0.7) x (f2(1270))
BR = (3.7  0.8  0.8) x (f2'(1525))
Consistent with scaling from J/
Tensor mesons dominate the
observed structure
No signal for fJ(2200), set UL:
f2(1270)
cos()
cos()
fit to J=2 helicity formalism
H. Vogel
FPCP 2006

13. Radiative Decays: Search for (1S) →  (')

CLEO
preliminary
Motivation:
Theoretically simple process (no hadronic FSI)
Extensively studied in J/ radiative decay -
good agreement with theory
Test models of scaling: - VDM
- NRQCD
- mixing with b
Previous UL ≈ 2x (CLEO II)
Choose 3 main decay modes for 
and 4 for ' (3x ( and )
No candidates seen in any  channel

CLEO
preliminary

H. Vogel
FPCP 2006

14. Radiative Decays: Search for (1S) →  ')
→
CLEO
preliminary
CLEO
preliminary
'→ 
No signal observed
in 21M (1S) events
Set upper limits,
→
→
preliminary
Strongly disfavors mixing with b
Still consistent with VDM and (barely) with NRQCD
H. Vogel
FPCP 2006

15. Hadronic Transitions between Upsilon States
Motivation:
Test of models of gluon (E1E1) emission
(e.g., Yan, Gottfried)
Most common process (known for decades):
Dipion transition between 3S1 states,
e.g., (mS) →  (nS) , m>n
(BR ≈ 50% in cc, BR ≈ % in bb)
H. Vogel
FPCP 2006

16. “Unusual” Hadronic Transition #1
b' →  (1S)
observed via
(3S) →  b'
Final state:  + ll-
First non-pionic hadronic transition
between Upsilon states
B(b' →  (1S)) = 1.6 %
B(b' →  (1S)) = 1.1 %
very large, considering phase space --
and nearly equal.
Agrees with prediction by Gottfried,
cf. also Voloshin hep-ph/
H. Vogel
FPCP 2006

17. 'b(2P) →  b(1P) “Unusual” Hadronic Transition #2 (3S) →  'b(2P)
observed via cascade,
(3S) →  'b(2P)
'b(2P) →  b(1P)
b(1P)→ (1S)
(1S) → l+l-
Very soft pions, plus substantial background from (3S) ->  (2S) !
H. Vogel
FPCP 2006

18. “Unusual” Hadronic Transition #2: Results
Example:
Observe both charged pions
Combining all analyses:
Significance 6 
First observation of a dipion cascade
between non- S states
Partial width
consistent with ≈ 0.4 keV
predicted by Kuang & Yan
CLEO PRD 73 (2006)
H. Vogel
FPCP 2006

19. Precision Measurement of B of (1S,2S,3S)
(a fundamental quantity in many analyses of widths and branching fractions!)
CLEO PRL 94 (2005)
sub-
tracted
on res
cont
The results for 2S) and 3S) are
significantly above previous PDG values!
Achieved relative precision of 2-3%
H. Vogel
FPCP 2006

20. Precision Measurement of ee , of (1S,2S,3S)
H. Vogel
FPCP 2006

21. Precision Measurement of ee of (1S,2S,3S)
Example:
Observed lineshape is convolution
of intrinsic width (O(keV)) with beam
energy spread (4 MeV)
Area is preserved;
must track “height” (lumi, eff'cy, bkg)
and “width” (shift in beam energy)
Performed repeated scans
Many backgrounds contribute
to the observed lineshape!
H. Vogel
FPCP 2006

22. Precision Measurement of ee of (1S,2S,3S)
All the scans:
11 on (1S),
6 on (2S),
7 on (3S) ...
...and the results:
CLEO hep-ex/
H. Vogel
FPCP 2006

23. Precision Measurement of ee of (1S,2S,3S)
Comparison of results --
with previous experiments
with LQCD calculations
H. Vogel
FPCP 2006

24. Hadronic Transitions (once more): Dipion Cascades between (nS) States
News from CLEO: currently finalizing high statistics measurement of
(3S) →  (1S, 2S) and (2S) →  (1S) .
(Almost ready! Plots shown today are for qualitative
comparison only.)
News from Belle: observed (4S) → +- (1S) ! (BR ≈ 1x10-4 )
News from BaBar: observed (4S) → + (1S) ( ≈ 2 keV)
AND (4S) → +- (2S) ! ( ≈ 2 keV)
... and an intriguing picture emerges!
H. Vogel
FPCP 2006

25. Dipion Cascades from the (4S)
BaBar
Belle
2S-1S
(ISR)
3S-1S
(ISR)
4S-1S
direct
M = M()-M() with M() near (1S)
H. Vogel
FPCP 2006

26. Dipion Cascades: Hot News
4S-2S
or What's So Special Aboutn=2 ?
Belle: hep-ex/
BaBar: talk at QCD Moriond'06
CLEO: very preliminary
Belle 2S-1S
Belle 4S-1S
Belle 3S-1S
4S-1S
CLEO 2S-1S
CLEO 3S-1S
very preliminary
very
preliminary
H. Vogel
FPCP 2006

27. Dipion Transitions in cc
compare with _
Dipion Transitions in cc
Y(4260)
CLEO-c Y(4260) → J
BaBar X(3872) → J
CLEO-c (3770) → J
BES (3682) → J
X(3872)
(3682)
(3770)
hep-ex/
PRD 71 (2005)
PRL 96(2006)
hep-ex/
H. Vogel
FPCP 2006

28. Summary Renaissance in non-BB Upsilon Physics (CLEO since 2001)
Test LQCD
Test basic QCD
Test scaling between charmonium and bottomium
Probe qq potential and test decay models
Explore the puzzle of dipion cascades
CLEO III has largest dedicated (1S,2S,3S) data sample (produced many papers already; many more in the pipeline)
Good to see BaBar & Belle also getting into the act! (dedicated (3S) run at KEK?)
H. Vogel
FPCP 2006

29. Backup Slides
H. Vogel
FPCP 2006

30. Dipion Cascades: Old News (1994-2000)
H. Vogel
FPCP 2006