CLEO Results From Υ Decays

Transcription

1 CLEO Results From Υ Decays V. Credé Cornell University, Ithaca, NY 2 now at Florida State University Tallahassee, FL Hadron 05

2 Outline 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

3 Outline Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

4 The Bottomonium Spectrum The Υ System CLEO III Detector CLEO III Υ Data Samples Mass (MeV) η b Υ χ b Υ (bb) states are part of the 3 1 S S S S P P J 2 1 D D J 3 3 S S 1,ee P P S P J 1 3 P J 1 1 D D J Signal (S-wv) Background Bottomonium family QCD analogy of Positronium: e + e bb For n 4, the Υ s decay predominantly to B mesons For n = 1, 2, 3: the bb system annihilates and can produce hadrons or lepton pairs Or cascades to other n 2S+1 L J states mostly via γ or ππ, but also χ bj (J = 1, 2) Υ(1S) ω

5 The Υ System CLEO III Detector CLEO III Υ Data Samples The Υ System (bb with J PC = 1 ) CESR at Cornell CESR collides e + e in order to produce Υ (ns) states b quark is heavy Non relativistic QM Most Υ decays unaccounted for Σ BR(Υ(1S)) < 10 % in PDG

6 Outline Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

7 The Υ System CLEO III Detector CLEO III Υ Data Samples CLEO-III SC Quadrupole Pylon Solenoid Coil Barrel Calorimeter Ring Imaging Cherenkov Detector Drift Chamber Silicon Vertex Detector / Beampipe SC Quadrupoles Rare Earth Quadrupole Magnet Iron + A Great Accelerator Team Barrel Muon Chambers Endcap Calorimeter Iron Polepiece Excellent Calorimeter Excellent Tracking RICH and de/dx for PID Muon Chambers

8 Outline Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

9 CLEO Υ Datasets The Υ System CLEO III Detector CLEO III Υ Data Samples CLEO III has largest world sample of clean Υ events below the BB threshold Off resonance and scan data CLEO has also collected 0.42 fb 1 at the Υ(5S) 21,0 x ,0 15,0 10,0 5,0 0,0 Υ(1S) (e + e Hadrons) (nb) I ,3 5,8 Υ(2S) Υ(3S) 5 (CUSB) (CLEO) E c.m. (GeV) 0 (1S) (2S) (3S) (4S) Mass (GeV/c 2 ) R (4S) (5S) (6S)

10 Outline Introduction 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

11 Υ(2S) γ χ bj (1P) (J = 2, 1, 0) ( 10 4 ) 85 + Number of Photons / 2% Bin States are well separated compared to corresponding transitions in charmonium. χ b2 (1P) χ b1 (1P) χ b0 (1P) E (MeV) Statistical errors smaller than point size Solid line: total fit Photon lines represented by Gaussian + low energy tail Dashed line: background Photon spectrum observed in off resonance data and in Υ(1S) data Slowly varying background component accounts for deviations in decays of χ b

12 Υ(3S) γ χ bj (2P) (J = 2, 1, 0) ( 10 4 ) 62 + Number of Photons / 2% Bin χ b2 (2P) χ b1 (2P) χ b0 (2P) Bottom plot: background subtracted data Three photon lines Additional Peaks: Υ(2S) γ χ bj (1P) χ bj (2P) γ Υ(1D) E (MeV)

13 Υ(3S) γ χ bj (1P) and χ bj (1P) γ Υ(1S) (J = 2, 1, 0) ( 10 4 ) 27 + Number of Photons / 2% Bin χ b0 (1P) E (MeV) Six photon lines large overlap One line is different and its amplitude can be measured Υ(3S) γχ b0 (1P) Rate determined for the first time B(Υ(3S) γ χ b 0(1P)) = (0.30 ± 0.04 ± 0.10) %

14 Further Results (PRL 94, (2005)) Υ(2S) final state χ b0 (1P) χ b1 (1P) χ b2 (1P) # of γ s (10 3 ) 198 ± ± ± 6 B (%) 3.75 ± 0.12 ± ± 0.12 ± ± 0.11 ± 0.40 E γ (MeV) ± 0.19 ± ± 0.09 ± ± 0.08 ± 0.30 Υ(3S) final state χ b0 (2P) χ b1 (2P) χ b2 (2P) # of γ s (10 3 ) 225 ± ± ± 6 B (%) 6.77 ± 0.20 ± ± 0.18 ± ± 0.17 ± 0.73 E γ (MeV) ± 0.16 ± ± 0.07 ± ± 0.06 ± 0.27 E γ s in transitions to χ bj (1P) and χ bj (2P) in good agreement with previous measurements Most precise determinations Branching ratios for Υ(2S) γ χ bj (1P) also in good agreement with previous measurements Improved experimental errors B s for Υ(3S) γ χ bj (2P) significantly larger than CUSB II

15 Outline Introduction 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

16 Radiative decays of heavy quarkonia useful in studying color singlet two gluon systems For example, two gluons can hadronize into a meson or directly form a glueball Many interesting results from radiative J/ψ decays Tensor states f 2 (1270) and f 2 (1525) observed In 1996, glueball candidate f J (2220) observed by BES Enhancement observed at pp threshold X(1860) (BES) Threshold effect or pp bound state? (under investigation) Experimental observation of radiative Υ(1S) decays challenging Rates suppressed by a factor ( q b q c ) 2 ( m m c b )

17 Events / 25 (MeV/c 2 ) f 0 (980) f 4 (2050) 2220 f 2 (1270) π + π Events / 25 (MeV/c 2 ) f 4 (2050) 2220 π + π π + π Invariant Mass (GeV/c 2 ) Events / 25 (MeV/c 2 ) 40 0 f 2 (1270) 2220 f 2 (1525) f 0 (1710) K + K Invariant Mass (GeV/c 2 ) K + K Events / 25 (MeV/c 2 ) X(1860) π + π Invariant Mass (GeV/c 2 ) pp Invariant Mass (GeV/c 2 ) pp

18 : Results Fit decay angles Decay helicities for f 2 (1270) and f 2(1525) predominantly 0 Fit mass to spin dependent relativistic Breit Wigner (LP ) B(Υ(1S) γ f 2 (1270)) = (10.2 ± 0.8 ± 0.7) 10 5 B(Υ(1S) γ f 2 (1525)) = ( ± 0.8) 10 5 B(Υ(1S) γ K + K ) = (1.14 ± 0.08 ± 0.10) 10 5 (2 GeV < M KK < 3 GeV) B(Υ(1S) γ f 0 (980) γ π + π ) < B(Υ(1S) γ f 4 (2050) γ π + π ) < B(Υ(1S) γ f 0 (1710) γ K + K ) < B(Υ(1S) γ pp) < (2 GeV < M pp < 3 GeV) Limits on f J (2220) and X(1860) < 10 6 Preliminary

19 Outline Introduction 1 Introduction The Υ System CLEO III Detector CLEO III Υ Data Samples 2 3 4

20 Direct Photons in Υ Decays: Motivation Preferred decay mode for an Υ meson is through the production of a BB meson pair (Zweig rule) Energetically impossible for resonances below Υ(4S) Therefore, below B meson threshold, Υ decays can occur via: Three gluon decay (ggg) Single photon QED decay Υ γ qq Two gluon + single photon (ggγ) mode Cascades (e.g. two pion transitions to other Υ states) Since Γ ggg α 3 QCD and Γ ggγ α 2 QCD α em R γ = Γggγ Γ ggg Experimentally determined = N ggγ = f (q b, α em, α QCD ) Results

21 Background and Procedure <Υ(4S) Continuum Check inclusive <Υ(4S) resonant hadronic PP MC ISR MC ISR+PP Idea: search for hadronic events with a nice isolated photon N X γ = p γ /E beam X γ Sources of Background ISR (high X γ ) π 0 Decays (low X γ ) Photon spectrum using below Υ(4S) data

22 Direct Photons in Υ Decays: Raw Photon Spectra Υ(1S) Inclusive Spectrum inclusive Υ(1S) resonant hadronic (PP) Continuum Inclusive Υ(2S) Spectrum inclusive Υ(2S) resonant hadronic (PP) Continuum Υ(2S) Υ(1S) ggγ N N X γ Raw Photon Spectra with Off-resonance data (continuum contribution) MC resonant non direct pseudo photons X γ

23 Direct Photons in Υ Decays: Raw Photon Spectra N Inclusive Υ(3S) Spectrum inclusive Υ(3S) resonant hadronic (PP) Continuum Υ(3S) Υ(2S) ggγ Υ(3S) Υ(1S) ggγ X γ Raw Photon Spectra with Off-resonance data (continuum contribution) Resonant non direct pseudo photons from hadron decays Cascade contribution from Υ(2S) decays Cascade contribution from Υ(2S) decays

24 Direct Photons in Υ Decays: Yield Determination Υ(1S) Exponential Subtraction continuum subtracted data modified field (fitted) exponential (fitted) Υ(2S) Exponential Subtraction continuum/cascade subtracted data modified field (fitted) exponential (fitted) Υ(2S) Υ(1S) ggγ N 10 3 N X γ Subtraction of backgrounds using an exponential Direct spectrum fit using model (Field) X γ

25 Direct Photons in Υ Decays: Raw Photon Spectra N Υ(3S) Exponential Subtraction continuum/cascade subtracted data modified field (fitted) exponential (fitted) Υ(3S) Υ(1S) ggγ Υ(3S) Υ(2S) ggγ Subtraction of backgrounds using an exponential floating normalization to estimate non direct photon spectrum Direct spectrum fit using model (Field) X γ

26 Direct Photons in Υ Decays: Results Determination of R γ = Γggγ Γ ggg = N ggγ = f (q b, α em, α QCD ) ( not mentioned determined from N Υ, PDG, and MC) R γ (1S) = (2.90 ± ± 0.22 ± 0.15) % R γ (2S) = (3.49 ± ± 0.58 ± 0.18) % R γ (3S) = (2.88 ± ± 0.38 ± 0.12) % Preliminary Errors are statistical, systematic, and model (Field vs. Garcia/Soto) R γ (1S) consistent with previous value similar systematic, but smaller statistical error First measurements of R γ (2S) and R γ (3S) R.D. Field, Phys. Lett. B133, 248 (1983) X. Garcia, J. Soto, Phys. Rev. D69, (2004)

27 χ b (2P) χ b (1P) π + π Mass (MeV) S S S P P J 2 1 D D J 3 3 S S P P 1 χ b 2 3 P J 1 3 P J 1 1 D D J Dominant Background Reactions Υ(3S) Υ(2S) π + π Υ(2S) χ b γ χ b Υ(1S) γ Υ(3S) χ b (2P) γ χ b (2P) Υ(1S) ω ω π + π π 0 Υ(3S) Υ(2S) π + π Υ(2S) Υ(1S) π 0 π S 0,ee 1 3 S 1 Signal (S-wv) Background Single-Pion Di-Pion

28 Signal MC Υ(2S) Background MC E1 (MeV) E1 (MeV) Recoil Mass (MeV) Recoil Mass (MeV) E1 (MeV) Data Numerous Monte Carlo simulations to evaluate selection criteria to predict eventual background Recoil Mass (MeV) Example: 2π Analysis

29 χ b (2P) χ b (1P) π + π : Results Results from two analyses using events with both and only one soft pion, respectively: 2π Analysis: 7 events seen, expected background 0.6 ± 0.2 1π Analysis: 17 events seen, expected background 2.2 ± 0.6 Γ(χ b (2P) χ b (1P) π + π ) = (0.80 ± ) kev First observation of a ππ transition outside of 3 S 1 system Preliminary Work on χ b (2P) χ b (1P) π 0 π 0 in progress

30 Summary Many interesting results from Υ physics Many more CLEO results still in the pipeline...