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Exclusive Hadron Production in e + e - Annihilation at 10.6 GeV

Exclusive Hadron Production in e + e - Annihilation at 10.6 GeV. Kai Yi , SLAC for the BaBar Collaboration Phenomenology Symposium, Wisconsin May 8, 2007. Outline. Introduction First Observation of positive C parity hadronic final states in the reactions e + e -      , 

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Exclusive Hadron Production in e + e - Annihilation at 10.6 GeV

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  1. Exclusive Hadron Production in e+e- Annihilation at 10.6 GeV Kai Yi , SLAC for the BaBar Collaboration Phenomenology Symposium, Wisconsin May 8, 2007 Kai Yi, BaBar/SLAC

  2. Outline • Introduction • First Observation of positive C parity hadronic final states in the reactions e+e-, • Observation of e+e- (C=1final state) • First Observation of e+e-+- (C=1? ) • Summary and Outlook Kai Yi, BaBar/SLAC

  3. Introduction—General Information PDG 2006 (e+e-hadrons) ~ 3 nb @10.6 GeV The design goal of the B factory is the study of B physics. However, at s~10.6 GeV, (e+e-hadrons) ~3 nb and <Nch> ~8 Large integrated luminosity (~500 fb-1) can study low-multiplicity exclusive hadronic processes with  values ~fb; this provides tests of QCD at the amplitude level. Today’s talk makes use of: L~343 fb-1 @10.58 GeV (OnPeak); L~36 fb-1 @10.54 GeV (OffPeak)

  4. Introduction—Possible Processes at B Factories Two photon processes One photon processes Two Photon TP B physics ~nb or h C= C=+ M1 ~fb Low multiplicity M2 A subset of e+e-qq processes; e+e-M1 M2 can also be studied via ISR Excellent test ground for QCD Two-Virtual-Photon-Annihilation, TVPA; new observation at BaBar Kai Yi, BaBar/SLAC

  5. Observation of e+e-/ (C=+1) PRL 97, 112002 (2006) Select events with invariant mass of (K+K-+-/+-+-) within 170 MeV of c.m. energy. @10.6GeV Only one entry in the +-+- region of interest out of two possible combinations (no ambiguity) Use binned log-likelihood fit over 9 tiles to extract signal signal tiles: 0.5<m<1.1 GeV/c2 () 1.008<mKK<1.035 GeV/c2() Kai Yi, BaBar/SLAC

  6. Observation of e+e-/ (C=+1) +- against “” +- against “”   total  background+f2 f2  background f2 Correlated  and 0 signals Relativistic Breit-Wigner lineshapes used in the fit K+K- against “” total background Kai Yi, BaBar/SLAC

  7. Observation of e+e-/ (C=+1) The extracted signals: Yield significance consistent Y(4S) production cannot contribute because of C parity conservation. The yields are consistent with continuum production Signals large enough to analyze the angular distributions and investigate the production mechanism of these events. Kai Yi, BaBar/SLAC

  8. Observation of e+e-/ (C=+1) Efficiency-corrected projections Production angle *polar angle of  or forward in CM consistent with expectation for TVPA   1+cos2* for comparison Helicity angle H—the angle between daughter and recoil in the mother rest frame 00 0 0 sin2H distributions All angular distributions are consistent with TVPA expectation for quasi-real photons H for + H for K+ H for + Kai Yi, BaBar/SLAC

  9. Observation of e+e-/ (C=+1) We observe e+e-C=+1 exclusive hadronic final states and angular analyses support TVPA production For 1.008<m<1.035 GeV and 0.5<m<1.1 GeV (|cos*|<0.8); the cross sections are: (00)=20.70.7(stat) 2.7(syst)fb reminder: (0)=5.70.5(stat) 0.8(syst)fb (e+e-hadrons @10 GeV) ~ 3 nb Theory calculations (after the measurement) consistent with our results: hep-ph/0606155 PRD 74 074012,2006 (00)= 21.40.7 17.70.6 fb (0) = 6.00.1 5.60.2 fb Extending our results to low energy, the TVPA contribution to muon (g-2) is small; this removes a possible uncertainty source in the g-2 calculation (hep-ph/0606155) Kai Yi, BaBar/SLAC

  10. Observation of e+e- at ~10.6 GeV PRD (RC) 74, 111103 • e+e-  is analogous to e+e-J/c ( has s-sbar content) Interesting because observed (e+e-J/c ) 10X higher than QCD predictions • Provides information on s-dependence by combining with a CLEO measurement at lower energy • Selection procedures similar to those for e+e-/ final states  @ 10.58 GeV @10.58+10.54 GeV  We see  correlation. Use a two-dimensional log-likelihood fit to extract signal: P-wave relativistic Breit-Wigner for ;Gaussian resolution function for  Kai Yi, BaBar/SLAC

  11. Observation of e+e- at ~10.6 GeV Mass projections Yield for 1.008<m<1.035 GeV/c2, and 0.4<m<0.8 GeV/c2 : All data: 245 events @10.58 GeV: 205 @10.54 GeV: 32 Significance: 6.5  U.L. for BF of Y(4S) decay @90% CL based on -10  21 events: 2.5X10-6 Kai Yi, BaBar/SLAC

  12. Observation of e+e- at ~10.6 GeV The full angular distribution, assuming one-virtual-photon production, is given by: Projections: *: polar angle in c.m.  :  helicity angle  : azimuthal angle of the decay plane  w.r.t. production plane normal in the c.m. frame Distributions in data are consistent with predictions within limited statistics We weight isotropic MC angular distributions as above for efficiency estimation. Kai Yi, BaBar/SLAC

  13. Observation of e+e- at ~10.6 GeV For 1.008<m<1.035 GeV/c2 and|cos*|<0.8, the cross section after radiative corrections is measured as: ()=2.10.4(stat) 0.1(syst)fb Extending to(|cos*|<=1) by assuming a 1+ cos2* distribution, this becomes: ()=2.90.5(stat) 0.1(syst)fb Combine with CLEO measurement at lower energy; 1/s3 energy dependence favored over 1/s4 (pQCD prediction), assuming continuum production. Another QCD puzzle? Analysis of BaBar ISR data is ongoing; will provide improved measurement of the s dependence Recent theory value (after the measurement) (hep-ph/0702065): ~3.1~4.3 fb, and 1/s3 dependence favored. Kai Yi, BaBar/SLAC

  14. Observation of e+e-→ r+r- • In general: • C(+-)=(-1)L+S, + or -; • P(+- )= (-1)L; • Single photon production • L odd, S even, I(+- )=1(Bose Statistics). Single photon (JPC = 1--) r+ r- Other possibility: Two-Virtual Photon Annihilation (C = +1) followed by FSI → unlikely? u u r+ r0 u d r0 u d r- u u No angular correlation predictions Kai Yi, BaBar/SLAC

  15. Observation of e+e-→ r+r- • Selection procedures similar to other final states • Likelihood Fit in (m-0, m+0) plane: • Signal function= product of P-wave relativistic BWs • rpp = threshold function • Linear combinatorial background N = 308 ± 25 signal events (> 5s)s(e+e-→ r+r-) = (20.0 ± 1.6± 3.6 ± 1.7) fb preliminary extending to full angular range (stat) (syst) (ampl) Kai Yi, BaBar/SLAC

  16. Observation of e+e-→ r+r- Assuming one-virtual-photon production, the angular distribution projections are: pQCD prediction (single g*): q± = r± helicity angle f± = azimuthal angle of p in r frame q* = scattering angle in the CM frame Brodsky and Lepage, PRD 24, 2848 (1981) Kai Yi, BaBar/SLAC

  17. Observation of e+e-→ r+r- Fit normalization constraint: BaBar Preliminary Results: |F00|2≠ 1 s(e+e-→ r0r0) > s(e+e- → r+r-) No evidence for Y(4S) → rr Are we seeing TVPA + FSI? Combine with ongoing ISR analysis to measure s dependence of the cross section of the individual amplitudes. Kai Yi, BaBar/SLAC

  18. Summary and Outlook • At BaBar we have: • Made the first observations of the TVPA hadronic processes: • e+e-ande+e- • Observed the process e+e- and measured the cross section; this provides an interesting test of the QCD prediction of the energy dependence, assuming continuum production. • Observed the process e+e-+- and measured the cross section; the amplitude measured from the angular analysis contradicts the pQCD expectation, assuming single photon production. • We plan to use the high integrated luminosity at BaBar to investigate other interesting low-multiplicity exclusive final states in the near future! The corresponding ISR data will enable us to measure s dependence and compare to QCD predictions. Kai Yi, BaBar/SLAC

  19. Barrel now has LST Kai Yi, BaBar/SLAC

  20. Data input and physics output Publication “Luminosity” Run 6 Kai Yi, BaBar/SLAC

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