BOTTOMONIUM STUDIES AT BABAR Veronique Ziegler SLAC Representing

BOTTOMONIUM STUDIES AT BABAR Veronique Ziegler (SLAC) Representing the Ba. Bar Collaboration EPS 2009, Krakow, Poland, Jul. 16 -22 2009 1

OVERVIEW • Brief overview of the bottomonium system • Report on selected Ba. Bar analyses of – the hb(1 S) state – the hb(1 P) state – the cb 0(1 P) state – the decay of the U(1 S) resonance to open charm 2

Ba. Bar RUN 7 (Dec. 2007 – Apr. 2008) PEP-II e+e- Asymmetric Collider Running at the U(2 S, 3 S)… BABAR DATASETS: ~ 120 x 106 Y(3 S) events ≈ 20 X previous dataset (CLEO) ~ 100 x 106 Y(2 S) events ≈ 11 X previous dataset (CLEO) 3 3

Current Picture of the Bottomonium Spectrum threshold hadrons (n. L) where n is the principal quantum number and L indicates the bb angular momentum in spectroscopic notation (L=S, P, D, …) hadrons S-wave [Orbital Ang. Momentum between quarks] P-wave 4

Bottomonium Transitions § U(n. S) resonances undergo: ©Hadronic transitions via p 0, h, w, pp emission ©Electric dipole transitions ©Magnetic dipole transitions -- Allowed transition: © Electromagnetic transitions between the levels can be calculated in the quark model important tool in understanding the bottomonium 5 internal structure

Mass Splittings in Heavy Quarkonia Hyperfine splitting Fine splitting S=1 Triplet-Singlet mass splitting of quarkonium states Mass splitting of triplet n. P quarkonium states: cc, b(n 3 P 0), cc, b(n 3 P 1), cc, b(n 3 P 2) S=0 Non-relativistic approximation = 0 for L≠ 0 ( → 0 for r → 0), if long-range spin forces are negligible ≠ 0 for L=0 6 6 botto U(1 S)-hb(1 S) mass splitting meast. key test of applicability of perturbative QCD to the

The hb(1 S) State 1 (1 S 0) 7

Expected hb Production Mechanism The U(n. S) states are produced in hadronic interactions or by virtual photons in e+e− interactions One of the expected production mechanisms of the hb(n’S) is by M 1 transition from the U(n. S) states [n’<n] 8

The Search for the hb at Ba. Bar • Decays of hb not known Search for hb signal in inclusive photon spectrum – Search for the radiative transition Y(3 S)→ghb(1 S) • In c. m. frame: √s = c. m. energy = m(Y(3 S)) m = m(hb) – For hb mass m = 9. 4 Ge. V/c 2 monochromatic line in Eg spectrum at 915 Me. V, i. e. look for a bump near 900 Me. V in inclusive photon energy spectrum from data taken at the U(3 S) 9

The Inclusive Photon Spectrum in U(3 S) Data Peaking background components (1): ~1/10 Analysis Sample U(3 S) cb 0(2 P) g soft E(g soft) = 122 Me. V U(1 S) g hard E(g hard) = 743 Me. V U(3 S) cb 1(2 P) g soft U(1 S) g hard E(g soft) = 99 Me. V E(g hard) = 764 Me. V U(3 S) cb 2(2 P) g soft U(1 S) g hard E(g soft) = 86 Me. V E(g hard) = 777 Me. V Look for a bump near 900 Me. V in the inclusive photon spectrum Large background U(3 S) cb. J(2 P) g soft (J=0, 1, 2) U(1 S) g hard [ E g = 856 Me. V ] Peaking background component (2): Radiative return from Y(3 S) to Y(1 S): e+e- → g ISR Y(1 S) 10

The Observation of the hb All backgrounds 19152 ± 2010 eventssubtracted Non-peaking Background subtracted g. ISR h b 11

The Inclusive Photon Spectrum in U(2 S) Data Peaking background components: U(2 S) cb 0(1 P) g soft E(g soft) = 163 Me. V U(1 S) g hard E(g hard) = 391 Me. V U(2 S) cb 1(1 P) g soft U(1 S) g hard E(g soft) = 130 Me. V E(g hard) = 423 Me. V U(2 S) cb 2(1 P) g soft U(1 S) g hard E(g soft) = 110 Me. V E(g hard) = 442 Me. V Look for a bump near 610 Me. V in the inclusive photon spectrum Large background U(2 S) cb. J(1 P) g soft (J=0, 1, 2) U(1 S) g hard [ E g = 545 Me. V ] ISR 12

Comparison of Eg Spectra Non-peaking Background subtracted U(3 S) spectrum Comparison with Y(3 S) g hb Analysis: ☛ Better photon energy resolution at lower energy better separation between peaks U(2 S) spectrum 13 ☛ More random photon background at lower energy less significance at similar BF 13

Summary of hb Results • hb mass: • Hyperfine splitting: v Combined mass is m(hb(1 S)) = 9390. 4± 3. 1 Me. V/c 2 resulting in a hyperfine splitting of 69. 9 ± 3. 1 Me. V/c 2 14

Expected hb Decay Properties hb b q The hb is expected to decay almost entirely through 2 gluons (OZI. . . hadronization suppressed large multiplicities expected ) Ba. Bar Search for hb(1 S) via exclusive decay mode hb→ K 0 S K+ p- in inclusive e+e- → hb X reactions. Toy MC study to establish sensitivity to nb. of signal candidates and to estimate expected U. L. on s(e+e- → hb X )x. B(hb→ K 0 S K+ p- ) 15 [analyses in progress for many other different hadronic final states] 15

The hb(1 P) State 1 (1 P 1) 16

Expected hb(1 P) Mass all: In non-relativistic approximation DMHF (triplet-singlet)~ 0 for 17

The Discovery of the hc(1 P) state of charmonium at CLEO Similar strategy to look for the hb(1 P) state of bottomonium U(3 S) b b 18

(Ge. V/c 2) Double Search Strategy: U(3 S) → p 0 hb(1 P) g Signal MC hb(1 S) Peaking background from cb. J(1 P) radiative m. m. (p 0) transitions (Ge. V) MC arbitrary scale E* (g) Generic MC Signal 19 19

The cb 0(1 P) State 3 (1 P 0) 20

The Search for the transition cb 0(1 P)→ U(1 S) g • No previous observation U(2 S) cb 0(1 P) g soft U(1 S) g hard Suppressed due to limited statistics due to E(g soft) = 163 Me. V expected • Ba. Bar has ~500 x more large hard E(g ) = 391 Me. V Y(2 S) data than used in hadronic previous attempts (Crystal width Ball) U(2 S) cb 1(1 P) g soft E(g soft) = 130 Me. V Strategy: Exclusive reconstruction U(1 S) g hard E(g hard) = 423 Me. V U(2 S) cb 2(1 P) g soft E(g soft) = 110 Me. V U(1 S) g hard E(g hard) = 442 Me. V 21 21

U(1 S)→ Open Charm 22

Measurement of Υ(1 S) decays to open charm • Little information on open charm decays of the Υ(1 S) • Only published limit (ARGUS collaboration) obtained using 41 pb− 1 collected at the Υ(1 S) resonance: B[Υ(1 S) → D*±X] < 1. 9% • Ba. Bar analyses in progress. . . Estimate of contribution using: - Rhad (ratio of hadronic to muon cross section) - BF(Y(1 S)→m+m-) - Mult. of D*±’s in qq fragmentation Well-established = (1. 52 ± 0. 20)% • Determine decay rate and D*± momentum distribution using the decay chain Υ(2 S) p+p−Υ(1 S), Υ(1 S) D*+ X • C. m. momentum distribution for the virtual photon process expected to follow the measured distribution for D*±’s from qq fragmentation. • Expected rate and the momentum distribution of D*± mesons from the virtual photon process can be used to determine the contribution of other 23 processes to this decay channel 23

CONCLUDING REMARKS • At present all bottomonium L = 0 and L = 1 spin-triplet states below B B threshold, U(n. S) and cb. J (n. P) observed • Several bottomonium states below Y(3 S) not yet discovered: 2 S-wave (hb), 2 P-wave (hb), 4 D-wave & possibly 4 F-wave • Among the recently discovered states is the ground state, the hb(1 S), ~70 Me. V/c 2 below the Y(1 S) • The measurement of the complete spectrum of the bottomonium system provides critical input to tests of predictions of lattice QCD and other QCD-based models of the bottomonium system such as NRQCD, etc. . . • The large data samples collected at the Y(3 S) (30 fb-1) and Y(2 S) (14 fb-1) resonance allow measurements of the few known transitions with very high precision and possibly first observations of many of the missing states thus providing a useful checks of QCD predictions for the bottomonium system 24

BACK-UP SLIDES 25

DCH Charged tracks momentum d. E/dx for PID DIRC Charged particle ID by means of velocity measurement Angles and positions of charged tracks just outside the beam pipe 26

QCD Calculations of the ηb mass and branching fraction • Recksiegel and Sumino, Phys. Lett. B 578, 369 (2004) [hep-ph/0305178] • Kniehl et al. , PRL 92 242001 (2004) [hep-ph/0312086] • Godfrey and Isgur, PRD 32, 189 (1985) • Fulcher, PRD 44, 2079 (1991) • Eichten and Quigg, PRD 49, 5845 (1994) [hep-ph/9402210] • Gupta and Johnson, PRD 53, 312 (1996) [hep-ph/9511267] • Ebert et al. , PRD 67, 014027 (2003) [hep-ph/0210381] • Zeng et al. , PRD 52, 5229 (1995) [hep-ph/9412269] e+e- → g. ISRY(1 S) Calculations 59 27

SUMMARY OF hb MEASUREMENTS from Y(3 S) CLEO ar. Xiv: hep-ph/0412158 A. Gray et al. , Phys. Rev. D 72, 094507(2005) (L QCD) DM = 61 +/- 14 Me. V/c 2 • lattice spacing: +/- 4 Me. V/c 2 • QCD radiative corrections: +/- 12 Me. V/c 2 • relativistic corrections: +/- 6 Me. V/c 2 S. Godfrey and N. Isgur, Phys. Rev. D 32, 189(1985) DM = 60 Me. V/c 2 ( Relativized Quark Model with Chromodynamics) cf. upper limit on B. F. < 4. 3 x 10 -4 @ 90% [CLEO III] 28

M(PDG) (Ge. V/c 2) Y(3 S) 10. 3552 Y(2 S) 10. 0233 Y(1 S) 9. 4603 Transition BF E*(g) (Ge. V) Transition Y(3 S)->Y(2 S) BF E*(g) (Ge. V) 10. 60% ee(@Y 3 S) → g Y(2 S) 0. 001% 0. 3266 ee(@Y 3 S) → g Y(1 S) 0. 8562 cb 2(2 P) 10. 2687 Y(3 S) → g cb 2(2 P) 13. 1% 0. 0862 cb 2(2 P) → g Y(2 S) 0. 0212% 0. 2425 Y(2 S) → g cb 2(1 P) 0. 758% 0. 1104 cb 1(2 P) 10. 2555 Y(3 S) → g cb 1(2 P) 12. 6% 0. 0993 cb 1(2 P) → g Y(2 S) 0. 0204% 0. 2296 Y(2 S) → g cb 1(1 P) 0. 731% 0. 1296 cb 0(2 P) 10. 2325 Y(3 S) → g cb 0(2 P) 5. 9% 0. 1220 cb 0(2 P) → g Y(2 S) 0. 0096% 0. 2071 Y(2 S) → g cb 0(1 P) 0. 403% 0. 1625 cb 2(1 P) 9. 9122 Y(3 S) → g cb 2(1 P) 0. 4335 cb 2(1 P) → g Y(1 S) 0. 0005% 0. 4416 cb 1(1 P) 9. 8928 Y(3 S) → g cb 1(1 P) 0. 4521 cb 1(1 P) → g Y(1 S) 0. 0005% 0. 4230 cb 0(1 P) 9. 8594 Y(3 S) → g cb 0(1 P) 0. 003% 0. 4839 cb 0(1 P) → g Y(1 S) 0. 0004% 0. 3911 hb(1 S) 9. 3889 Y(3 S) → g hb(1 S) 0. 9212 hb(2 S) 9. 9633 Y(3 S) → g hb(2 S) 0. 3845 hb(2 S) → g Y(1 S) 0. 4903 29