Misura di R

Importanza di R

• QED(MZ)

• (g-2)

• Test di CVC nei decadimenti del • Regole di somma di QCD e S

Hadronic contributions to ahad

12 - 5 - 12 (+)3.7 - 5 (+J/, )1.8 - 3.743 (+,)2 > 4 (+KK)

< 1.8 GeV

ahad

2[ahad]

<1.8 GeV

<1.8 GeV

1%

Calculations based onDavier, Eidelman, Höcker, Zhang

e+e- data only!

2 contrib. ahad

8% [2m - 0.5 GeV] 54% [0.6 - 1.0 GeV] 10% [Rest<1.8 GeV]

2 contrib. ahad

8% [2m - 0.5 GeV] 34% [0.6 - 1.0 GeV] 31% [Rest< 1.8 GeV]1GeV

Contribution to had from F. Jegerlehner

Comparison of different evaluations of had

had Method Ref

0.0280 0.00065 data<12 GeV S.Eidelman F.Jegerlehner ’95

0.02777 0.00017 data<1.8 GeV J.H.Kuhen, M.Steinhauser ’98

0.02763 0.00016 data<1.8GeV M.Davier, A.Höcker ’98

0.0277300.000148 Euclidean>2.5 GeV F.Jegerlehener ’99

0.0274260.000190 scaled data, pQCD 2.8-3.7, 5-

A.D.Martin et al. ’00

0.0278960.000391 data<12 GeV (new data CMD2 & BES)

F.Jegerlehner ’01

0.02761 0.00036 data<12 GeV

(new data CMD2 & BES)

H.Burkhardt,B.Pietrzyk ’01 ( ’05)

0.00007

(0.00005)

up to J/up to )

magnitude errors

Burkhardt & Pietrzyk

2001Contributions to

had

Including KLOE results, a preliminary analysis of B.& P. found a value of (5)(mZ

2) which confirms their 2001 estimate: (5)(mZ

2) =0.02761±0.00036

Results on R from scan at s<12 GeV

Place Ring Detector Ecm(GeV) pts Year

Novosibirsk VEPP-2M

VEPP-2

CMD2,SND

Olya,ND,CMD

<1.4

<1.4

128 97-99

79-85

Beijing BEPC BESII 2-5 85 98-99

Orsay DCI M3N,DMI,DM2 1.35-2.13 33 ’78

Frascati Adone 2,MEA,

Boson,BCF

1.42-3.09 31 ’78

SLAC Spear MarkI 2.8-7.8 78 ’82

Hamburg Doris DASP

PLUTO

C.Ball

LENA

3.1-5.2

3.6-4.8,9.46

5.0-7.4

7.4-9.4

64

27

11

95

’79

77

‘90

’82

Novosibirsk VEPP-4 MD-1 7.23-10.34 30 ‘91

Recent Results from…

’01 ‘03

128<1.4CMD2,SNDVEPP-2MNovosibirsk

’05,…

<10 Gev (via ISR)

(0.5-4.5 GeV)

Babar PEPIISLAC

’05<1 (via ISR)KLOEDANEFrascati

YearptsEcm(GeV)DetectorRingPlace

Future Projects or Upgrades

Place Ring Detector Ecm(GeV) pts Year

Novosibirsk VEPP-2000 Upgrades of CMD2 and SND

<2 ’08?

Beijing BEPCII BESIII 2-5 ’06?

Cornell CESR CLEO-C 3-5 ’05

Data at ‘95

Data at ‘05

• 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- + - + -, + - o o (syst~7%), e+e- + - o

(syst~12%), e+e- KS,KL, e+e- + -,+ - (syst~15%) from CMD2 and SND

– e+e- + - from CMD2 with syst~1.4% published on ’99 and with syst~0.6% ( 0.61<E<0.96 GeV) published on ’01

– e+e- + - from SND with syst~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 R/R~7%

(improvement of a factor 2) - New results on 4from BES with R/R~10% (presented on Oct

2005 in Frascati)

Recent results with energy Scan:

BES: 4Ecm L Ecm L2.00 45.81.4 2.80 89.0 1.8

2.20 123.5 3.7 2.90 94.0 2.6

2.40 61.0 1.6 3.00 947 22

2.50 47.0 1.0 3.07 2272.8 36.4

2.60 1231.0 14.8 3.65 6450.4 90.3

2.70 71.6 2.1

Luminosity (nb-1)2(+-)

• 1)KLOE:– e+e- + - with syst~1.3% (0.35<E<0.95 GeV2) published on ’05

– e+e- + - at threshold is under way(0.1 GeV2 bin width (5-20 MeV))

• 2)BABAR:- e+e- + - 0 between 1. and 3 GeV with syst~5%-10%published on ’05

(25 MeV bin width)

- e+e- 4h (+ -+ -, + -+ -, + -+ -) between 0.6 and 4.5 GeV published on ’05:

- syst(+ -+ -) is 12% (<1GeV), 5%(1.-3 GeV), 16% (>3 GeV)

- syst(+ -+ -) is 15% (1.5-4.5 GeV)

- syst(+ -+ -) is 20% (2.0-4.5 GeV)

- e+e- 6h (3(+ -, 2(+ -) 00, 2(+ -) + -) between 1.5 and 4.5 GeV with syst between 6 and 10%

– e+e- + - with syst<=1% is under way

Recent/expected results with ISR:

Babar: 3+-0

Babar: 4h

Babar: 6

3(+-) 2(+-)00

Total systematic: ~6-8% Total systematic: ~11%

Babar: 2K4

2(+-)K+K-

Total systematic: ~7%

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

had

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 Nbar-N bound state

Open issues

• Buco di FOCUS nella sezione d’urto dei 6

• Babar conferma in entrambi i canali

Errore percentuale

R/R R/R

Punti con errore ~3% dalla misura inclusiva di BES

ZOOM

PRL 84, 594 (2000) – PRL 88, 101802 (2002)