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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, 2. decay of an unbound bb state to a bound bb state. Upsilon Decays. _. Motivation for Studying Bound State bb.

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Upsilon Decays

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  1. 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, 2. decay of an unbound bb state to a bound bb state. Upsilon Decays

  2. FPCP 2006 _ 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 

  3. FPCP 2006 The Renaissance in  Physics CLEO II CLEO III CESR, Nov 2001 – Dec 2002: * Dedicated (1S), (2S), (3S) runs * 10-20-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)

  4. FPCP 2006 The CLEO III Detector

  5. FPCP 2006 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

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

  7. FPCP 2006 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)

  8. FPCP 2006 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

  9. FPCP 2006 (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

  10. FPCP 2006 (1S) Decay to Charmonium: Results CLEO PRD 70 (2004) 072001 • B((1S) → J/+ X) = (6.4  0.4  0.6) x 10-4 favors color-octet. • Momentum spectrum of J/'s is softer than predicted (FSI?) • Transitions to (2S) and c states are also observed.

  11. FPCP 2006 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

  12. FPCP 2006 Radiative Decays, (1S) →  h+ h- : Results CLEO PRD 73 (2006) 032001 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 10-5 (f2(1270)) BR = (3.7  0.8  0.8) x 10-5 (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

  13. FPCP 2006 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 ≈ 2x10-5 (CLEO II) Choose 3 main decay modes for  and 4 for ' (3x ( and ) No candidates seen in any  channel  CLEO preliminary 

  14. FPCP 2006 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

  15. FPCP 2006 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 ≈ 5 - 20 % in bb)

  16. FPCP 2006 “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/0304165

  17. FPCP 2006 “Unusual” Hadronic Transition #2 'b(2P) → b(1P) 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) !

  18. FPCP 2006 “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) 012003

  19. FPCP 2006 Precision Measurement of B of (1S,2S,3S) (a fundamental quantity in many analyses of widths and branching fractions!) CLEO PRL 94 (2005) 012001 sub- tracted on res cont The results for 2S) and 3S) are significantly above previous PDG values! Achieved relative precision of 2-3%

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

  21. FPCP 2006 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!

  22. FPCP 2006 Precision Measurement of ee of (1S,2S,3S) 1S 2S 3S All the scans: 11 on (1S), 6 on (2S), 7 on (3S) ... ...and the results: CLEO hep-ex/0512056

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

  24. FPCP 2006 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!

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

  26. FPCP 2006 Dipion Cascades:Hot News 4S-2S or What's So Special Aboutn=2 ? Belle: hep-ex/0512034 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

  27. FPCP 2006 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/0602034 PRD 71 (2005) 071103 PRL 96(2006) 082004 hep-ex/9909038

  28. FPCP 2006 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?)

  29. FPCP 2006 Backup Slides

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

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