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hadrons

. Vacuum Polarization and the impact of BaBar data. Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay. QWG Workshop 2007 October 1 7 - 20 , 200 7 , DESY. . . . hadrons. davier@lal.in2p3.fr. Essentials of Hadronic Vacuum Polarization.

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  1. Vacuum Polarization and the impact of BaBar data Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay QWG Workshop 2007 October 17 - 20, 2007, DESY    hadrons davier@lal.in2p3.fr

  2. Essentials of Hadronic Vacuum Polarization vacuum polarization modifies the interacting electron charge with: photon vacuum polarization function (q2) Leptonic lep(s) calculable in QED. However, quark loops are modified by long-distance hadronic physics, cannot (yet) be calculated within QCD (!) Way out: Optical theorem (unitarity) ... ... and subtracted dispersion relation for (q2) (analyticity) Im[ ]  | hadrons |2 ... and equivalently for a [had]

  3. The Muonic (g–2) Contributions to the Standard Model (SM) Prediction: Dominant uncertainty from lowest order hadronic piece. Cannot be calculated from QCD (“first principles”) – but:we can use experiment (!) The Situation 1995 had  ”Dispersion relation“  had   ...

  4. Contributions to the dispersion integral 2 3 (+,) 4 > 4 (+KK) 1.8 - 3.7 3.7 - 5 (+J/, ) 5 - 12 (+) 12 -  < 1.8 GeV ahad,LO 2 2[ahad,LO] 2

  5. Improved Determinations of the Hadronic Contribution to (g–2) and (MZ ) 2 Eidelman-Jegerlehner’95, Z.Phys. C67 (1995) 585 • Since then: Improved determi-nation of the dispersion integral: • better data • extended use of QCD • Inclusion of precise  data using SU(2) (CVC) Alemany-Davier-Höcker’97, Narison’01, Trocóniz-Ynduráin’01, + later works • Extended use of (dominantly) perturbative QCD Martin-Zeppenfeld’95, Davier-Höcker’97, Kühn-Steinhauser’98, Erler’98, + others Improvement in 4 Steps: • Theoretical constraints from QCD sum rules and use of Adler function Groote-Körner-Schilcher-Nasrallah’98, Davier-Höcker’98, Martin-Outhwaite-Ryskin’00, Cvetič-Lee-Schmidt’01, Jegerlehner et al’00, Dorokhov’04 + others • Better data for the e+e–  +– cross section and multihadron channels CMD-2’02 (revised 03), KLOE’04, SND’05 (revised 06), CMD-2’06, BaBar’04-06

  6. Goals of the BaBar ISR Program Precise measurements of cross section for all significant processes, e+e hadrons, from threshold to ~4-5GeV • Measure , KK channels with high precision • Summing up exclusive cross sections==>Improve the precision of R • Study spectroscopy of JPC=1−− states and their decays M. Davier et al., 2003 Ös

  7. Exclusive Channels with BaBar ISR ISR • systematic program underway using ISR from (4S) energies, taking • advantage of high luminosity (B-factory) • statistics comparable to CMD-2/SND for Ecm<1.4 GeV, much better than • DM1/DM2 above • full energy range covered at the same time • channels identified using particle ID and kinematic fitting • systematic uncertainties at 5-10% level • large acceptance for hadronic system (boosted opposite to ISR photon) X = 2E /Ecm H is radiation function

  8. 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 last Summer : • 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 accepted by PRD e-Print: arXiv:0708.2461 [hep-ex] • Work in progress on : • ,K+K, p+p3p0 • Inclusive R

  9. BaBar ISR:  errors include systematics huge discrepancy with DM2 SND BaBar DM2 contribution to ahad (1.05-1.8 GeV) : • all before BaBar 2.45  0.26  0.03 • all + BaBar 2.79  0.19  0.01 • all – DM2 + BaBar 3.25  0.09  0.01 x1010

  10. BaBar ISR: 22 contribution to ahad (<1.8 GeV) : • all before BaBar 14.20  0.87  0.24 • all + BaBar 13.09  0.44  0.00 x1010

  11. BaBar ISR: 33 BaBar contribution to ahad (<1.8 GeV) : • all before BaBar 0.10  0.10 • all + BaBar 0.108  0.016 x1010

  12. BaBar ISR: 222 BaBar contribution to ahad (<1.8 GeV) : • all before BaBar 1.42  0.30  0.03 • all + BaBar 0.890  0.093 x1010

  13. BaBar ISR: +00 Only statistical errors plotted BaBar preliminary ψ ->p0p0J/ψ(->mm) J/ψ • Previous situation chaotic • Preliminary syst. error: 8% in peak 5% • Good agreement with SND <1.4 GeV • Huge improvement >1.4 GeV • First measurement >2.5 GeV

  14. BaBar ISR: +00--substructure • Intermediate states: • 0 • +- large and first seen • 0 f0(980) • a1(1260) BaBar preliminary MC

  15. BaBar ISR: ++0 Cross sections of sub-mode: +-  0  X =  3 + 0 3 : from subtraction /+-  0 3

  16. 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

  17. BaBar ISR: p+-+p- • ~4,300 events selected • first measurement BaBar preliminary

  18. BaBar ISR:KSK, K+K-p KSK-++- Dominant states: K*(980)K and K2*(1430)K K+K-p Isoscalar channel dominates over isovector Parameters(1680): PDG m=172320 MeV, 168020  = 37175 MeV, 15050 ee= 58060 eV, B/BK*K 1/3

  19. BaBar ISR: KK, K+K-pp K+K-p+p- Substructure in the final state K*(892) - 1 per event K+K-0p0 K+K-0 p0 K1(1270),K1(1400) – 1+ K+K-p+p- ~ 1500

  20. BaBar ISR:KKKK,KKppp,KKpp K+K- K+K- jK+K-dominated J/Y K+K-+p-p K+K-+p- First measurement !

  21. BaBar ISR: KKpppp Cross section Substructures K*0(892) j J/y first measurement

  22. Present BaBar Measurements only statistical errors syst. 5-10% to obtain R in the energy range 1-2 GeV the processes +-, +-30, +-40, K+K-, KSKL, KSKL, KSK+-0 remain to be measured

  23. Evaluating the Dispersion Integral use data Agreement bet-ween Data (BES) and pQCD (within correlated systematic errors) use QCD Better agreement between exclusive and inclusive (2) data than in 1997-1998 analyses use QCD

  24. Update for ICHEP-Tau06 Hadronic HO – ( 9.8 ± 0.1) 10–10 Hadronic LBL + (12.0 ± 3.5) 10–10 Electroweak (15.4 ± 0.2) 10–10 QED (11 658 471.9 ± 0.1) 10–10 inclu-ding: Knecht-Nyffeler,Phys.Rev.Lett. 88 (2002) 071802 Melnikov-Vainshtein, hep-ph/0312226 Davier-Marciano, Ann. Rev. Nucl. Part. Sc. (2004) Kinoshita-Nio (2006) BNL E821 (2004): aexp = (11 659 208.0  6.3) 1010 Observed Difference with Experiment (DEHZ)

  25. Conclusions and Outlook • Hadronic vacuum polarization is still the dominant systematics for SM prediction of the muon g –2 • Significant step in precision from new experimental input • CMD-2 + SND for 2 BaBar for multipion channels • Precision of SM prediction (5.6)now exceeds experimental precision (6.3) • SM prediction for a differs by 3.3  [e+e – ] from experiment (BNL 2004) • In the next months many new results expected • KLOE 2p (different analyses) • BaBar 2p, 2K, remaining multihadrons in 1-2 GeV range • VEPP-2000 in the longer run • vacuum polarization calculations in line for the next challenges • new g-2 measurements • precision EW measurements (Tevatron, LHC, ILC)

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