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ISR physics at BaBar

ISR physics at BaBar. Vladimir Druzhinin (BINP, Novosibirsk) for BaBar Collaboration. ISR method. High PEP-II luminosity  precise measurement of the e + e - cross section  0 at low c.m. energies with BaBar . Few previous data in the 1.4-3.0 GeV range.

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ISR physics at BaBar

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  1. ISR physics at BaBar Vladimir Druzhinin (BINP, Novosibirsk) for BaBar Collaboration

  2. ISR method • High PEP-II luminosity  precise measurement of the e+e- cross section0at low c.m. energies with BaBar. • Few previous data in the 1.4-3.0 GeV range. • Improved hadron spectroscopy. • Input to (gm-2) and aemcalculations.

  3. ISR program at BABAR • p+p- pion form factor • p+p- p+p- • p+p- 0 0 r resonance recurrences • p+p- h • p+p- 0w resonance recurrences • 5 • 6 structure near 2 GeV • K+K-p+p, K+K-K+K- • K+K-p+p p+p • K+K- , KSKL kaon form factor • K+K- h, f hfresonance recurrences • KK • pp baryon form factors • 

  4. Selection of ee h  candidates • All final particles are detected • Charged particle identification with the use of Cherenkov angle and dE/dx measurement • Kinematic fit with requirement of energy and momentum balance and mass constraint for 0 candidates.

  5. Background subtraction signal region Main sources of background: • ISR events with misidentified particles K+K-0 for+-0 K+K-, +- for pp • events with 0 instead of ISR photon +-00for+-0 pp0 for pp • other ISR and e+e-→qq events +-, +-00for+-0 pp0for pp +-0 K+K-0, +-00 +-, +-00, … sideband

  6.   +-0mass spectrum PRD 70, 072004 (2004)  90 fb-1 f B(Vee)B(V3) PDG  (6.700.06 0.27)10-5 (6.350.11)10-5 f (4.300.08 0.21)10-5(4.590.14)10-5  (0.820.050.06)10-6  (1.30.10.1)10-6 PDG M()= 13502020 MeV/c21400 - 1450 ()= 4507070 MeV 180 - 250 M()= 1660102 MeV/c21670  30 ()= 2303020 MeV 315  35

  7. SND BaBar DM2 e+e-  +-0cross section PRD 70, 072004 (2004) • coverage of wide region in this experiment - no point-to-point normalization • problems • consistent with SND data EC.M. < 1.4 GeV • inconsistent with DM2 results • overall normalization error ~5% up to 2.5 GeV

  8. ee 22cross section PRD 71, 052001 (2005) 90 fb-1 Systematic errors: • 12% for m4 < 1 GeV, • 5% for 1 < m4 < 3 GeV, • 16% for higher masses Good agreement with direct eemeasurements Most precise result above 1.4 GeV a1(1260) - dominant, f0(1370) final state is seen.

  9. ee KK, 2K2K cross sections PRD 70, 072004 (2004) J/ J/ Systematic error – 15% Substantial resonance sub-structures observed: • K*(890)K dominant • f, KK contribute strongly • K*2(1430)K seen. First measurement Systematic error – 25% No clear mass structures in the two- or three-kaon subsystems No ’ s !

  10. The cross section depends on two form factors, electric and magnetic. From the total cross section we obtain effective form factor Ratio of form factors can be extracted from analysis of angular dependence Advantage of ISR measurement: low mass and angular dependence of detection efficiency.

  11. J/ 232 fb-1 (2S)

  12. Angular distribution 1 4 2 5 preliminary 6 3 Dominant contribution of electric form factor near threshold

  13. Hep:-ph/0507085 BaBar |GE/GM| measurements vs previous ones and dispersion relation prediction (yellow) based on JLab space-like GE/GM and analyticity DM2+FENICE • BaBar preliminary • LEAR • hep-ph/0507085 E835

  14. Cross section preliminary preliminary In reasonable agreement with e+e- previous measurements Negative steps at M ~ 2.2 and 3 GeV (!?)

  15. Effective proton form factor preliminary preliminary • Steep behaviour at threshold confirmed • Similar behaviourat threshold is seen in other processes with different quantum numbers preliminary

  16. ee 3(), KK2(), 2(0) cross sections preliminary preliminary preliminary ee 3() Systematic error – 6-8% 4 intermediate state ee 2(0), Systematic error – 11%, Substantial substructure: 4,3,,3 ee KK2() First measurement Systematic error – 15% Complex substructure: weak , strong K(890) 232 fb-1

  17. Fit of 6 cross sections preliminary 3() 2(0) FOCUS M, GeV 1.880.03 1.860.021.910.01 , GeV 0.130.030.160.020.0370.013 , deg. 2040-3151030 preliminary Dip near 1.9 GeV is confirmed but wider than in DM2 (e+e-)and FOCUS (diffractive photoproduction) experiments.

  18. J/ and (2S) decays PDG B(J/ +-0) (2.180.19)10-2(1.50.2) 10-2 BES 2.100.12 B(J/ 2+2-) (3.610.37)10-3(4.01.0) 10-3 B(J/  3+3-) (4.400.41)10-3(42) 10-3 B(J/ 2+2-20) (1.650.21)10-2– B(J/ K+K-+-) (6.090.73)10-3(7.22.3) 10-3 B(J/ 2K+2K-) (6.71.5)10-4(9.23.3) 10-4 B(J/ K+K-2+2-) (5.090.55)10-3(3.11.3) 10-3 B(J/ pp) (2.220.16)10-3(2.170.08) 10-3 B((2S) 2+2-20) (5.31.7)10-3– B((2S) K+K-2+2-) (2.11.0)10-4– B((2S) pp) (3.30.9)10-4(2.360.24) 10-4

  19. Summary • Using ISR method the several e+e—annihilation cross sections have been measured from threshold to 4.5 GeV. • These are the most precise measurements to date for c.m. energies greater than 1.4 GeV. • The proton form factor has complex mass dependence. • Near-threshold enhancement. • Two mass regions, near 2.25 and 3 GeV, with the rapid decrease of the form factor. • Noticeable deviation of |GE/GM| ratio from unity. • The existence of the dip in e+e 6 cross section near 1.9 GeV is confirmed. • Several B(J/, (2S) -> X) measurements are better than current world averages.

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