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Misura di R

Misura di R. Importanza di R. a QED (M Z ) (g-2) m Test di CVC nei decadimenti del t Regole di somma di QCD e a S. 2 . 3  (+,). 4 . > 4  (+KK). 1.8 - 3.7. 3.7 - 5 (+J/, ). 5 - 12 (+). 12 - . < 1.8 GeV. 2 p contrib. a  had 8% [2m p - 0.5 GeV]

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Misura di R

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  1. Misura di R

  2. Importanza di R • aQED(MZ) • (g-2)m • Test di CVC nei decadimenti del t • Regole di somma di QCD e aS

  3. 2 3 (+,) 4 > 4 (+KK) 1.8 - 3.7 3.7 - 5 (+J/, ) 5 - 12 (+) 12 -  < 1.8 GeV 2p contrib. ahad 8% [2mp - 0.5 GeV] 54% [0.6 - 1.0 GeV] 10% [Rest<1.8 GeV] r 2p contrib. dahad 8% [2mp - 0.5 GeV] 34% [0.6 - 1.0 GeV] 31% [Rest< 1.8 GeV] r > 1GeV Hadronic contributions to amhad Calculations based on Davier, Eidelman, Höcker, Zhang ahad <1.8 GeV 2[ahad] <1.8 GeV 1% e+e- data only!

  4. Contribution to Da(5)had from F. Jegerlehner

  5. Comparison of different evaluations of Da(5)had

  6. Burkhardt & Pietrzyk 2001 Contributions toDahad magnitude errors Including KLOE results, a preliminary analysis of B.& P. found a value of Da(5)(mZ2) which confirms their 2001 estimate: Da(5)(mZ2) =0.02761±0.00036

  7. Results on R from scan at s<12 GeV

  8. Recent Results from… Place Ring Detector Ecm(GeV) pts Year Novosibirsk VEPP-2M CMD2,SND <1.4 128 ’01 ‘03 Frascati DAFNE KLOE <1 (via ISR) ’05 SLAC PEPII Babar <10 Gev (via ISR) (0.5-4.5 GeV) ’05,… Future Projects or Upgrades

  9. Data at ‘95

  10. Data at ‘05

  11. Recent results with energy Scan: • After ’95 main results were published from CMD2 and SND @VEPP-2M and BESII@BEPC: • 1)VEPP-2M, Novosibirsk (exclusive measurements) 0.4 <Ecm<1.4 GeV • New results on e+e-p+ p- p+ p-, p+ p- po po (ssyst~7%), e+e-p+ p- po • (ssyst~12%), e+e-KS,KL, e+e-w p+ p-,hp+ p- (ssyst~15%) from CMD2 and SND • e+e-p+ p-from CMD2 with ssyst~1.4% published on ’99 and with ssyst~0.6% ( 0.61<E<0.96 GeV) published on ’01 • e+e-p+ p-from SND with ssyst~1.3%(hep-ex/0506076) • 2)BESII @ BEPC, Beijing (inclusive measurement) 2 <Ecm<5 GeV • New result on R in 2 <Ecm<5 GeV from BESII coll., with sR/R~7% • (improvement of a factor 2) • - New results on 4p from BES with sR/R~10% (presented on Oct 2005 in Frascati)

  12. BES: 4p Luminosity (nb-1) 2(p+p-)

  13. Recent/expected results with ISR: • 1)KLOE: • e+e-p+ p- with ssyst~1.3% (0.35<E<0.95 GeV2) published on ’05 • e+e-p+ p-at threshold is under way • (0.1 GeV2 bin width (5-20 MeV)) • 2)BABAR: • - e+e-p+ p- p0 between 1. and 3 GeV with ssyst~5%-10%published on ’05 • (25 MeV bin width) • - e+e- 4h (p+ p-p+ p-, p+ p-K+ K-, K+ K-K+ K-) between 0.6 and 4.5 GeV published on ’05: • - ssyst(p+ p-p+ p-) is 12% (<1GeV), 5%(1.-3 GeV), 16% (>3 GeV) • - ssyst(p+ p-K+ K-) is 15% (1.5-4.5 GeV) • - ssyst(K+ K-K+ K-) is 20% (2.0-4.5 GeV) • - e+e- 6h (3(p+ p-), 2(p+ p-)p0p0, 2(p+ p-) K+ K-) between 1.5 and 4.5 GeV with ssyst between 6 and 10% • e+e-p+ p-with ssyst<=1% is under way

  14. Babar: 3p p+p-p0

  15. Babar: 4h

  16. Babar: 6p 3(p+p-) 2(p+p-)p0p0 Total systematic: ~6-8% Total systematic: ~11%

  17. Babar: 2K4p 2(p+p-)K+K- Total systematic: ~7%

  18. Proiezione a 10 anni Con cosa deve essere competitiva una misura tra 10 anni? • Babar... • BES... • VEPP 2000... • Altro? • La regione 1-2 GeV particolarmente interessante: l’errore attuale (15%) contribuisce con un 40% all’errore totale su Da(5)had

  19. Open issues • Buco nella sezione d’urto multiadronica vicino a soglia p bar-b • narrow vector meson resonance, with a mass M 1.87 GeV and a width   10-20 MeV, consistent with an Nbar-N bound state

  20. Open issues • Buco di FOCUS nella sezione d’urto dei 6p • Babar conferma in entrambi i canali

  21. Errore percentuale ZOOM DR/R DR/R Punti con errore ~3% dalla misura inclusiva di BES PRL 84, 594 (2000) – PRL 88, 101802 (2002)

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