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Wenfeng Wang Laboratoire de l'Accélérateur Linéair e, Orsay for the BABAR Collaboration

Wenfeng Wang Laboratoire de l'Accélérateur Linéair e, Orsay for the BABAR Collaboration. Studies of s( e + e   hadrons ) at BABAR using Initial State Radiation (ISR). XII International Conference on Hadron Spectroscopy 8-13 October, 2007, Frascati. Outline. Introduction

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Wenfeng Wang Laboratoire de l'Accélérateur Linéair e, Orsay for the BABAR Collaboration

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  1. Wenfeng Wang Laboratoire de l'Accélérateur Linéaire, Orsay for the BABAR Collaboration Studies ofs(e+ehadrons)at BABAR using Initial State Radiation (ISR) XII International Conference on Hadron Spectroscopy 8-13 October, 2007, Frascati R measurements at BaBar-ISR

  2. Outline • Introduction • ISR method at BABAR • Exclusive Analyses • Inclusive analysis • Summary R measurements at BaBar-ISR

  3. PEP-II is an asymmetric e+ecollider with a CM energy of (4S). Peak luminosity = 1.17 1034cm-2s-1 Integrated luminosity = 500 fb-1 BaBar/PEP-II BaBar EMC: • 6580 CsI(Tl) crystals, E resolution ~1-2 % at high E. • Covers 91% of solid angle. • BaBar DIRC • Covers 80% of solid angle • Particle ID up to 4-5 GeV/c R measurements at BaBar-ISR

  4. Objective Precise measurements of cross section for all significant processes, e+e hadrons, from threshold to ~4-5GeV • Summing up exclusive cross sections==>Improve the precision of R • Study spectroscopy of JPC=1−− states and their decays M. Davier et al., 2003 • R(s): crucial input for hadronic contributions to • Muon anomalous magnetic moment (am) -----dispersion integrals • K(s) known QED kernel • Running ofaQED (for SM fits Þ Higgs Mass). Ös R measurements at BaBar-ISR

  5. gISR e+ Hadrons e ISR at (4S) Energies Born cross-section: • Whole Ös’spectrum from threshold to ~4-5GeV with tagged photon; high transverse momentum, high acceptance • Obtained in one experiment, as opposed to scan experiments: point-to-point uncertainties greatly reduced • High PEP-II luminosity and BABAR detector performance allow to be competitive with low energy e+emachines 232 fb-1 Ös’ MC simulation (AfkQed) uses Born-level ISR + FSR + Interference, + Structure functions for soft photons; precision ~1% R measurements at BaBar-ISR

  6. BaBar ISR: e+e-hadrons • Reactions for which results have been published : • ppPRD 73, 012005 (2006) • p+p-p0 PRD 70, 072004 (2004) • 2p+2p-, K+K-p+p-, PRD 71, 052001 (2005) • K+K-p+p- K+K-p0p0 , 2K+2K- PRD 76, 012008 (2007) • 3p+3p-, 2p+2p-p0p0, K+K-2p+2p- PRD 73, 052003 (2006) • New results presented in this meeting : • K+Kp0,KSKp+,K+Kh, BaBar Preliminary • LL , LS0 , S0S0 Submitted to PRD e-Print: arXiv:0709.1988 [hep-ex] • +ppBaBar Preliminary • 2p+2pp0,2p+2ph,KK p+pp0, KKp+ph Submitted to PRD e-Print: arXiv:0708.2461 [hep-ex] • Work in progress on : • ,K+K, p+p3p0 • Inclusive R R measurements at BaBar-ISR

  7. BaBar ISR: +pp BaBar preliminary r(2150)? ψ ->p0p0J/ψ(->mm) J/ψ • Important mode for a and QED • Preliminary precision: 8% in peak 5% • Good agreement with SND <1.4 GeV • Huge improvement >1.4 GeV • First measurement >2.5 GeV R measurements at BaBar-ISR

  8. BaBar ISR:+pp--substructure • Intermediate states: • 0 • +- large and 1st seen • 0 f0(980) • a1(1260) BaBar preliminary MC 2 entries/event R measurements at BaBar-ISR

  9. BaBar ISR:p+-+p-p • ~30,000 events => allow to study details • Lower mass : 20% bg. • ~4.5GeV : 60-80% bg. • Wider energy region • ~4.0 nb at 1.65 GeV, generally decrease except for J/ψ and ψ(2S) • systematic error~7% at peak. J/ψ ψ(2S) BG qq BaBar preliminary R measurements at BaBar-ISR Only statistical errors in plot,

  10. BaBar ISR:p+-+p-p--substructure Rich internal structure: • +-  0 •  • X =  3 + 0 3 X = (1300) or a1(1260) inconsistent witha2(1320)  f h J/ψ Non-ISR bg 3 R measurements at BaBar-ISR

  11. BaBar ISR:p+-+p-p--sub-modes Cross sections of sub-mode: +-  0  X =  3 + 0 3 : from subtraction /+- 0 3 p+-+p-p   0 (h->3) R measurements at BaBar-ISR

  12. BaBar ISR: +p- BaBar preliminary BaBar,3   BaBar preliminary f0(980) 1st measurement 1.35  0.03 0.45  0.14 1.66  0.01 0.22  0.04 BaBar,3 R measurements at BaBar-ISR

  13. BaBar ISR: p+-+p- • First measurement of cross section • Peak 1.2 nb at 2.2 GeV • 10% systematic error below 3 GeV • ~4,300 events selected, J/ψ seen, • Lower mass <20% bg • Higher mass 50-80% bg BaBar preliminary R measurements at BaBar-ISR

  14. BaBar ISR: p+-+p---substructure f1(1285) hr(1450) dominant h’(958) (958)0 f1(1285)0 Internal structure: +-+ = (1450) (958) = (958)0 f1(1285) = f1(1285)0 m=2.150.040.05 GeV =0.350.040.05 GeV (2150)? R measurements at BaBar-ISR

  15. BaBar measurement summary To calculate R in the energy range 1-2 GeV the processes +-, +-30, +-40, K+K-, KSKL, KSKL, KSK+-0 must be measured. R measurements at BaBar-ISR

  16. J/yandy(2S) decays @BaBar • J/y and y(2S) used to monitor mass scale and resolution • byproduct but important: measure Geex B(J/y->f) => B(J/y->f) BaBar preliminary +pp ψ ->p0p0J/ψ(->mm) J/ψ BaBar preliminary 2(+)p p+p- J/yincluded Part of results, more seen in papers. R measurements at BaBar-ISR

  17. Inclusive R: Analysis Technique • Select events with a high-energy photon in a region with good energy resolution. • Primary background: QED events with a high-E photon • Remove/subtract: e+e-g , gg; t+t-g and m+m-g ... • Compute the integral: Taken from MC Selection summary (MC) HadronicBkg ttg Signal mmg QED R measurements at BaBar-ISR

  18. Inclusive R: Energy Resolution effects • Energy resolution ~2%, affects the spectrum, especially at low s’: • Fortunately, we measure an integral of R(s)/s, not R(s)/s itself: • SmearingÞevents move in s’; Problem only if weight function is non-uniform. • OK forDaHad • Does not work for am True Spectrum True Spectrum (MC) Smeared spectrum Smeared spectrum s’ [GeV2] s’ [GeV2] • The region <5 GeV dominates overall uncertainty ~ 3.2% • Preliminary systematic uncertainty 4.4% -->3.6% , improve overall precision R measurements at BaBar-ISR

  19. Summary • BaBar continues study of low energy e+e cross section using ISR • Results published: pp, p+p-p0, 2p+2p-, 2K+2K-, 3p+3p-, 2p+2p-p0p0, K+K-2p+2p-, K+K-p+p-, K+K-p0p0 • Preliminary results: +pp, 2p+2pp0,2p+2ph,K+Kp0,KSKp+,K+Kh, LL , LS0 , S0S0,KK p+pp0, KKp+ph • Obtained data allow to determine parameters of excited-, -, -states. Simultaneous fit of all channels? • Work in progress: p+p-, K+K-, KK(p,h), p+p-p0p0,inclusive-R… BABAR providing high statistics measurements of exclusive hadronic cross sections with ~5-10% syst. uncertainties ==> large improvement over the existing data in the lower mass range! R measurements at BaBar-ISR

  20. Backup Slides

  21. Relevance of precision of R measurements Contributions toahad,LO : low-s region crucial Contributions to Dahad sensitive to full accessible range (1-5) GeV has dominant uncertainties Burkhardt & Pietrzyk 2001 Davier-Eidelman-Höcker-Zhang 2006 magnitude < 1.8 GeV 2 errors <1.8 GeV 2 < 1.8 GeV R measurements at BaBar-ISR 2 3 (+,) 4 > 4 (+KK) 1.8 - 3.7 3.7 - 5 (+J/, ) 5 - 12 (+) 12 - 

  22. BaBar ISR:+pp non  r(2150) ?  +- R measurements at BaBar-ISR

  23. J/yandy(2S) decays @BaBar • J/y and y(2S) used to monitor mass scale and resolution • byproduct but important: measure Geex B(J/y->f) => B(J/y->f) BaBar preliminary R measurements at BaBar-ISR

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