Phi meson physicsPhi meson physics

Marianna Testa University of Roma La Sapienza & INFN

for the KLOE collaboration

“e+e- Collisions from Phi to Psi”,

Novosibirsk 27 February-2 March 2006

2

High signal for the decay in KK, at the edge of the kinematically allowed region, decay suppressed Zweig ruless

discovery

First seen in bubble chamber experiments at Brookhaven in 1962 in the reactions K- + p + K+K K- + p + K++K-

Mass 1020 MeV, <<20 MeV Quantum numbers JPC = 1--

3

at e+e- collider

22tot

-

m

f)()ee( 12)f(

Absolute BR can be determined using ( f) and e+e-) (only)at a factory

SND (e+e- KSKL)PRD 63,072002 (2001)

m =1019.42 0.05 MeV = 4.21 0.04 MeV

040.0938.0)f(BRf

Using

• f /tot from SND & CMD-2 with f = K+K- , KK, , , • e+e-) from KLOE

4

factories

VEPP 2M (1974-2000)•Ebeam :180-700 MeV

• scan step: s = (1 –10 )MeV•1 bunch•beam current 10-50 mA

•Lpeak 3 1030 cm-2s-1

• Circumference 18 m•Time collisiont 60 ns•2 experiments CMD-2 & SND

• 40 pb-1/detectorLdt

DAFNE •Ebeam :510 MeV

•2 separate rings for e+ e- to minimize beam-beam

•Lpeak 1.3 1032 cm-2s-1

•up to 120 bunches 20 mA per bunch

•Crossing angle at 12.5 mrad

• KLOE experiment

• 2.4 fb-1 Ldt

5

A factory is a collider e+e- running at s = Mb

(1020)

a0(980)

f0(980)

'

KK

0-

0- 1-

1-

0+

0+

BR 83%

BR 15%

BR 1.3%

KAON physics• Vus , kaon form factors from semileptonic KS,L ,K decays• Rare KS,L decays (Ks) • CPT test with semileptonic Ks , KL charge asymmetries

Non Kaon Physics•radiative decays (scalars, pseudoscalars + photon)•hadronic cross section

Physics at a -factory

6

The KK pairs in the final state have the same quantum numbers, i.e. are produced in a pure JPC = 1– – state

pppp ,,,,2

1SLSL KKKKi

KS (K) KL (K)

The decay at rest provides monochromatic and pure beam of kaons

Kaon production at the resonance

1.5 109 K± pairs/fb-1, 1. 109 KS KL pairs/fb-1

7

Kaon at a Factory:

Tagging:

observation of KS,L signals presence of KL,S

precision measurement of absolute BR’s

• Kinematical closure of the events

•Pure beam

of tagged KS mesons

•Interference measurementes in the K system

Kaon physics at a factory

Kaon at fixed target experiments

•Higher rate production

•Higher energy particles

8

2112

2/21

2

2

2

1122211

cos2

,;,

21

2121

ttme

eeCtftfItt

tttt

LS

LSSL

where t1(t2) is the time of one (the other) kaon decay into f1 (f2) final state and:

SiLii

ii KfKfe i

fi = letc

characteristic interference termat a -factoryentire set of K parameters from interferometry

2

21212

2

SSN KfKfC

p,Kp,Kp,Kp,K2

1i SLSL

Kaon interferometry

9

Kaon interferometry (II)

Integrating in (t1+t2) we get the time difference (t=t1-t2) distribution (1-dim plot):

21 and 0for

cos2

0;,

122/

21

2

2

2

12112

ttt

tme

eetffI

t

ttC

LS

SL

LS

From these distributions for various final states fi one can measure the following quantities: Phases (difference of) from the

interference term only at a factory arg , , , , i iiLS m

10

KLOE preliminaryFit with PDG values for S, L:

m = (5.34 0.34) × 10 ħ s

PDG ’04: (5.301 0.016) × 10 ħ s

Fix m to PDG ’04 value, obtain:

No simultaneous events:same final state/ antisymmetric initial state

Peak position sensitive to m

Coherent KL regeneration on beam pipe

|t1 t2|/S

S,L = 0.0430.0380.035 0.008

S,L = 0.130.160.15

cf. Bertlmann ’99 (CPLEAR):

• Data: 7366 evts– Fit: 2/dof = 15.1/22

I(t) eL eS 2(1 S,L) eSL cos(mt)

KL(S) at t2KS(L) at t1

13

KSKL interference and QM coherence

11

K physics

KS “beam”:

• UL on BR(KS )

• BR(KS e) and charge asymmetry

KL “beam”:• main KL BR’s and KL lifetime• form factors • K from KL Re(/’)

Charged kaons:• BR’s for semileptonic and 2-body decays, K lifetime

Vus

CP, CPT tests

12

At at factory all experimental inputs are aviable: Branching ratios, lifetimes and form factors.

(K0 e) |Vus |2 |f+i(0) |2 Ii(+ ,,0 ,) Sew

where i runs over the four modes K,0 (e3), K ,0 (3)f+

i(0) form factor, I() phase space integral, Sew short distance correction (1.0232)

• Extract |Vus| from (K())/(()) ratio.

Dominated by the theoretical uncertainity on the fK/f evaluation.

• At af factory all experimental inputs aviable: Branching ratios, lifetimes, and form factors.

Vus at a factory

•Extract |Vus| from (K())/(()) |Vus|2/|Vud|2fK2/f2.

•Extract |Vus| From Kl3 decays:

Can test if = 0 at few 10-3:from super-allowed 0+ 0+ Fermi transitions, n -decays: 2|Vud|Vud = 0.0010from semileptonic kaon decays (PDG 2004 fit): 2|Vus|Vus = 0.0011

|Vud|2 + |Vus|2 + |Vub|2 ~ |Vud|2 + |Vus|2 1 – • Most precise test of unitarity possible at present comes from 1st row:

13

Vus: KL branching ratios, life time, slopes

Lesser of pmiss-Emiss in or hyp (MeV)

Data7% of samplee

KLOE mmts at 0.5%BR(KL → πeν(γ)) = 0.4007 0.0006 0.0014 BR(KL → πμν(γ)) = 0.2698 0.0006 0.0014 BR(KL → 3π0) = 0.1997 0.0005 0.0019 BR(KL → π+π−π0(γ))= 0.1263 0.0005 0.0011

L = 50.84 0.23 ns

’ 103

’’

10

3

KTeVISTRA+

KLOE NA48

1 contours

For Ke3 Form factors slopes:

f(t) = f(0) [1 t] or

f(0) [1 ’ t½ ’’ t2]

see talk “Neutral Kaons at KLOE”...

14

K00

K0

K nucl.int.K e3

K 3

V us: Charged kaon decays

e

P*(MeV)

Particle momentum in

K rest frame

Nev

/MeV

MC

BR(K+ +()) = 0.6366 0.0009stat. 0.0015syst

PLB632,76-80(2006).

KLOE preliminary

BR(K e3) = 5.047 0.046stat

BR(K 3 ) = 3.310 0.040stat

systematic error evaluation to be completed

Vus = 0.2223±0.0025

see Versaci’s talk

15

Vus at a factory

Vus

Vus = 0.2248 0.0020 from KLe3, KL3, Ke3, K 3,Kse3

Vud = 0.97377 0.00027 CKM 2005 Proceedings

Vus/Vud = 0.2294 0.00026 from K 2

Quad form-factor param.(KLOE+KTeV + ISTRA+NA48)f+(0)=0.961(8) Leutwyler & Roos

unitarity

16

CPT & CP test : KS physics

11

KLOE BR(KS e) = (7.09 0.08stat 0.05syst) × 104

AS = (2 9stat 5syst) × 103

AL = (3.322 0.058 0.047) × 10-3

Re(x) =1/4 ((KS e)/(KL e) -1 )= (.6 3.1stat 1.8syst) 10

KS 30 is purely CP violating

If CPT conserved, S = L |’000|

SM prediction: BR(KS 30) = 1.9 × 109

BR(KS 30) < 1.4×105 (first limit, SND)

BR(KS 30) < 1.2×107 (KLOE)

KS eSensitivity to CPT violating effects through charge asymmetry AS Test of the S = Q rule, Vus determination

CMD2’99first observation

P-Eloss-Eclu (MeV)

Data— MC fitsignalbad

bad

other 50 5000

100200

300

400

500

600

700

Emiss(e) cPmiss(MeV)100150

17

CP : BR KL

(MeV) )( 22missmiss pE

KLOE Preliminary resultBR(KL )= (1.963 0.012 0.017) 10-3

4 standard deviations discrepancy wrt PDG04 = (2.090 0.025) 10-3

agreement with KTeV

Using BR(KL ) and L

from KLOE and S from PDG04 | = (2.216 0.013) 10-3

|| PDG04 = (2.284 0.014)10-3

1.6 agreement with prediction from Unitarity Triangle

18

’ physics

BR( ) = (1.295 ±0.025)10-2

BR( ’) = (6.2 ± 0.7) 10-5

At a factory: 4 107 /fb-1, 4. 105 ’/fb-1

• lower bkg with respect topp reactions• tagging: ’ antiparallel to monoenergetic photon (360 MeV for , 60 MeV for ’) • ’ simultaneously collected

• (’) /tot 100 with respect to hadronic production

→→ KLOE

19

biggest contribution p6 in PT

KLOE preliminary:BR(→) = ( 8.4 ± 2.7stat ± 1.4syst ) × 10-5

agrees with Op6 calcolutions

C,P,CP, pt test: physics

M4 (MeV)

KLOE

l+l-,lll(‘)l(‘) (dalitz & double dalitz decays) e.m. form factorsCMD-2 BR( e+e- ) =(7.10 ± 0.64 ± 0.46) 10-3

BR( e+e-) = (3.7 +2.5 –1.8 0.3) 10-4 (CP violating in flavour conserving process) SND BR( e+e- )= (5.15 ± 0.62 ± 0.39) 10-3

C violatingKLOE BR(3.6105 @ 90% CL

20

(’) Isospin violation

lowest order of PT:

; F33

u)t,M(s,)m(m

m

m

Q

1u)t,A(s,

2π

2K

2π2

π

2K

2

2u

2d

22s2

mm

mmQ

ˆ

C,P,CP, pt test: physics (II)

KLOE preliminary

X (T+-T-) , YT0

Q = 22.8 0.4 [B.Martemyanov,V.Sopov, PRD 71 (2005) 017501]violation of the Dashen theorem (QDash.= 24.2 if (m2

+-m20)em= (m2

K+-m2K0)em)

CMD-2: BR < 3.3 10-4 @90% C.L.

KLOE: BR < 1.3 10-5 @90% C.L.

C,CP violating

see next talk

21

Scalar mesons

Radiative decays: f0(980) a0(980) f0(600)

a0(980)

I=0 I=1/2 I=1

f0(980)

f0(600)“”

K*0(800)“”

(1020)

Mass (MeV/c2)

0

500

1000

not easily interpreted as qq meson(3P0 nonet)other interpretations: qqqq states (Jaffe ’77), KK molecules (Weinstein-Isgur ’90)

Extract to scalar “coupling” Since |ss> ( ”scalar”) s-quark content 4-quark vs. 2-quark states

confirm of f0(600) Both BRS and scalar mass spectra are sensitive to their nature[Achasov, Ivanchenko 1989]

22

First observation ’99 CMD-2 of

( ): Looking for f0

First observation’98 SND of f000

M() MeV

SND PLB485,349 (2000) (2 107

KLOE: clear evidence of f0 see next talk)

f0(980) region

M() (MeV)• data MC: ISR+FSR MC: ISR+FSR+ f0(KL)

M() MeV

23

Looking for a0(980)→π0

KLOE PLB536,209 (2002) 16 pb–1 ’BR() = (8.5 0.5stat 0.6syst) 10–5

•Statistics x 20

First observation of a0 by SND PLB 438,441CMD-2 PLB462,380 (1999)BR() = (0.90 0.24stat 0.10syst) 10–4

first observation

24

Future of factory?

Dafne short term upgradeL up to ~ 5 1032 cm-2 s-1, Lint 20fb-1

Present Linof KLOE now Lpeak= 1.3 1032 cm-2 s-1

new machine L > 8 1032 cm-2 s-1

Lint > 50fb-1

LNF proposals

see Venanzoni’s talk

25

Prospectives for KS physics

KS 0 0 0 CP,CPT < 1.2 10-7 < 5 10-9 seenKS e CPT, S= Q (7.09 0.10)10-4 0.2 10-5 0.1 10-5

As CPT (1.5 11) 10-3 2 10-3 1 10-3

KS + - 0 pt (3 1)10-7 0.4 10-7 0.3 10-7 KS e+e- < 1.4 10-7 < 2 10-8 < 9 10-9

KS 0 e+e- KL (6 3)10-9 seen 2 10-9 KS pt (2.78 0.07)10-6 0.03 10-6 0.02 10-6

Assuming present efficiencies or 5-10%

Present @20fb-1 @50 fb-1

measurement

Lint= 20-50 fb-1

CPT and S= Q violating parameters down to the per mill levelCompetitive on rare dacays, interesting for pt mostly

26

Kaon interferometry: main observables

measured quantity parameters

mode

0;,0;,

0;,0;,0000

0000

tItI

tItItA

00 LS KK

LS KK

a

dK

a

cK

LS KK teIteI

teIteItA

;,;,

;,;,

tI ;, LS KK L Sm

adab

A KKL

2

0;,0;,

0;,0;,

teeIteeI

teeIteeItACPT

27

Mode Parameter Best measurement

or PDG-04 fit

KLOE-2

L=100 fb-1

m 5.288 ± 0.043 109 s-1

± 0.02STAT

109 s-1

Re’ (1.67 ± 0.26) 10-3 ± 0.2STAT 10-3

Im’ 0.0012± 0.0023 ± 0.0022STAT

e AL (3322± 58 ± 47 ) 10-

6

± 18STAT 10-6

e e Re() (0.29 ± 0.27) 10-3 ± 0.2STAT 10-3

e e Im() (0.24 ± 0.50) 10-4 ± 20STAT 10-4

Prospectives for Interferometry

28

Several models can be tested (only) at a factory

DHit ,

Simple decoherence model: 0 QM

22112211,

2

2211

2

221122211

12

,;,

tKftKftKftKf

tKftKftKftKftftfI

KK

N

LLSSSLLS KKKKKKKKi

Decoherence related to Quantum gravity and CPT violation, J. Ellis et al (1984)

GeV 102,, 202

PLANCK

K

M

MO

Test of Quantum Mechanics and CPT at a factory

3652

210~1010

PLANCKMEO

Novel type of CPT violation for correlated KK states , J. Bernabeu et al. (2004)

29

int. lum. (fb-1)

• present KLOE

• KLOE + VDET

-- CPLEAR results

-- Planck’s scale region

65PLANCK2

1010~ME,,

Decoherence related to Quantum gravity and CPT:

30

Novel type of CPT for correlated KK states:

• present KLOE

• KLOE + VDET

-- Planck’s scale region

int. lum. (fb-1)

Re (similar for Im )

3

652

2

10~

1010~

PLANCKME

31

(1 + i tanSW)(Re iIm f A*(KSf) A(KLf)

S

1

CP CPT

Test of CPT trough Bell Steinberger relation

At present f = contributes with the bigger error to Im sensitivity

only at a factory:pure KS beams gives access low BR,access to KSKL interference term

CPT: Bell-Steinberger

32

R( 8.0 ± 2.7 ) × 10 with=4.63% 3000 evts

study of spectrum

’ l+l-,lll(‘)l(‘) (Dalitz & double dalitz decays) with high statistics

e+e - test of CP violation beyond SM

’ sensitive toexpcted

200.000 events

Prospectives for & scalars physics@20fb-1

With 20 fb-1 f0 , fK+K- (KK) (expected BR ~ 10-6(-8) ) well measured (105 K+K- and 103 KK), direct measure of the gfKK coupling

Large samaple of 9x108 and ’ 4x106

Intersting channels

33

Physics with 20-100 fb-1

Kaon physics:General remark @20 fb-1

CPT and S= Q violating parameters down to the per mill level competitive on super rare dacys, interesting for pt mostly

Re(x+) Contribution of BR(KS e @20fb-1 (2 10-3 ) similar to ohersAs @20 fb-1 3 measurement

Bell Steinberger Relation Interference in the () channle bring to total error Im to present of 10-5 down to 10-6, equivalent to K0 K0 mass relative difference below 10-19

KS 0 l+l- pollution to KL 0 l+l- via KSKL mixing @20 fb-1 seen,@50fb-1 sensitivity to 10-9

theory request 15% accuracy

KS 0 0 0 @20 fb-1 5 10-9 sensity @50fb-1 few events obervableKS + - 0 @20 fb-1 precision 15% KS @20 fb-1 5 error

d (l0) 10-3 d(l0’) l0-4 check of the SU(3) breaking in f+(0)

34

101 fb-1 Kaon physics:

CPT and S= Q violating parameters down to the per mill levelCompetitive on super rare dacays, interesting for pt mostlyRe(e/e) @10-4 (direct CPV)K L,S interferometry Im(e/e) @10-2 (CPT)

physics

Dalitz decays e+e-, , e+e-e+e-,e+e- decays (BR’s 10-3 10-5)C,P,CP ,LF test via , , e-,e+, Significant improvement on UL study of the shape on mass, sensitive to test of VDM and a0 e+e-, exp BR 6 10-9a4 process BR( 10-8, 10-6) helicity suppressed , sensitive to new interactionsUL (<7.7 10-5) expe BR 4 10-6 () BR(5.8 0.8)10-6

Physics program vs luminosity

35

102 fb-1 CPT test @ unprecedentetest level of precision via 1) rare KL&KS interferences 2) rare direc CPV violation in K+ asym and rare KL

103 fb-1 sensitivity ot KL (&KL pee, KL+ p+vv) @ SM level (@ f factory no bkg from neutral baryons, kaons 4 mom know) region of high discovery potential for non standards source of CPV via new tests of CKM mech in then kaon system

36

physics@ 20 fb-1 6 108 mesons produced

Dalitz and double Dalitz decays e+e-, , e+e-e+e-,e+e- decays (BR’s 10-3 10-5) easily reached @20 fb-1

C,P,CP ,LF violating decays , , e-,e+, Signifacant improvement on UL

Statistics benefit on other decays study of the shape on mass, sensitive to test of VDM and a0

e+e-, exp BR 6 10-9UL (<7.7 10-5) (but bkg from ee ee(g)) expe BR 4 10-6 BR(5.8 0.8)10-6

37

@20 f KKG well measured 104 K+k+ and 103 K0K)

38

Sensitivity to CPT violating effects through charge asymmetry AS

Test of the S = Q rule,

(KS e)/(KL e) =

1 + 4 Re(x )

FISRT OBSERVATION CMD-2

BR(Ks e ) = (7.2 ±1.4) 10-4

KLOE BR(KS e) =

(7.09 0.08stat 0.05syst) × 104

CPT: KS semileptonic decays

Data— MC fitsignalbad

bad

other

50 5000

100

200

300

400

500

600

700

Emiss(e) cPmiss(MeV)100150

AS = (2 9stat 5syst) × 103 AL = (3322 58 47) × 10-6

Re(x) = (.6 3.1stat 1.8syst) 10

KLOE

39

Physics with 100 fb-1

AS sensitivity 10-4

probe the K0 K0 mass difference to 10-18 level (if CPT is violated only in the mass matrix)

KS 0 l+l- pollution to KL 0 l+l- via KSKL mixing error at 10% level theory request 15% accuracy

40

Conclusions

A f favcotry provides the ideal place to perform almosto without competitorsKS physics Quantum interferencem studiesh/h physics

High luminosity to access rare KS decays sensitivity to CPT testNeutral kaon InterferometryX pt studiesProgram complementary to LHC

41

Spare slides

42

Leptonic width ll) ll)

SND, PRL 86, 1698 (2001) from e+e- +-

B( l+l-) = sqrt(B( e+e-) B( +-))= (2.89 ± 0.10 ± 0.06) 10-4

KLOE, PLB 608, 199 (2005)using e+e- e+e- and e+e- +-

( l+l-) = (1.320 ± 0.017 ± 0.015) keV

43

Measure using KL

tagged by KS π+π- events

KLOE L = 50.92 0.17 0.25 ns

Average with result from KL BR’s:L = 50.84 0.23 ns

cfr Vosburgh ’72,:L = 51.54 0.44 ns

× 102 Events/0.3 ns

L/c (ns)

6 - 24.8 ns40-165 cm

0.37 L

PK = 110 MeVExcellent lever

arm for lifetime measurement

KL lifetime

44

Parameterization:

t = (pK p)2/m2

For Ke3:f(t) = f(0) [1 t] or

f(0) [1 ’ t½ ’’ t2]KLOE preliminaryLinear fit:

= (28.6 ±0.5 ± 0.8) 103

Quadratic fit:

’ = (25.5 ± 1.5 ± 1.9) 103

’’ = (1.4 ± 0.7 ± 0.7) 103

(’, ’’) = 0.95 ’ 103

’’

10

3

KTeV

ISTRA+

KLOE NA48

1 contours

KLe3 form-factor slopes

45

CMD2 collaboration PLB605, 26 (2005)

BR( ) = (1.373± 0.014 ± 0.085) 10-2 BR( ) = (1.258± 0.037 ± 0.077) 10-3

SND collaboration PRD 63,072002 (2001)??BR( e+e-) = (2.93± 0.02 ± 0.14 ±0.02) 10-4 BR( ) = (47.6± 0.3 ± 1.6 ± 0.3 ) 10-2

BR( KSKL) = (35.1± 0.2 ± 1.2 ± 0.3 ) 10-2

BR( + -0) = (15.9± 0.2 ± 0.7 ± 0.4 ) 10-2

??BR( ) = (1.33± 0.03 ± 0.05 ± 0.01 ) 10-2

m= (1019.42 ± 0.02 ± 0.04) MeV( ± ±)MeV

46s (MeV)

First observation in f hpg by SND (PLB 438,441) 395 pb-1 at peak + 10 pb-1 1) → (39.43%) 5 final state 2.2 104 events2) →π+π-π0 (22.6%) π+π-+ 5 4180 events• Fit the two spectra simultaneously

20000 γηπρπγηπγ

dm

dσ a

→

→ →

→

Kaon Loop No Structure

Mπ (MeV)

→

→

Nature of the scalar a0: a0(980)→π0

KLOE 2000 data (2 107 f) PLB485,349 (2000)

47

First observation SND of 00 1998 Br(f f0g)= (3.42± 0.30 ± 0.36)10-4

M(pp) MEV

Looking for f0

Kaon-loop fit: 1. VDM part still not perfect (see residuals); 2. Scalar part ok BUT f0(600) is needed [p(2) ~ 10-4 30% !]; 3. f0(980) parameters agree with analysis again R > 1 (gfKK > gf -).

Residuals vs. DPposition

Data- fit comparison (on projections)

KLOE preli

min

ary

48

CP Test in flavour conserving processesSM predictions small signature of New Physics beyond SM

JPC= 0-+

e e CP asymmetry between and ee planes (as KL)

CMD-2 3.8 +2.5 –1.3 0.3 P,CP (large background in hadron production) 4 P,CP 4 (background free)

C Test not extensively studied in em and strong interactions C

e+e-, +-, if * SM: via BR 3 10-9

49

KS physics

Ks Test of pt

KS

Rchanged along the years

Measurement of Na48 ( (relevant bkg from KL )

differs for PT O(p4) by 30%, useful to fix O(p6) counterterm

50

Sensitivity to CPT violating effects through charge asymmetry AS

Test of the S = Q rule,

(KS e)/(KL e) =

1 + 4 Re(x )

FISRT OBSERVATION CMD-2

BR(Ks e ) = (7.2 ±1.4) 10-4

KLOE BR(KS e) =

(7.09 0.08stat 0.05syst) × 104

CPT: KS semileptonic decays

Data— MC fitsignalbad

bad

other

50 5000

100

200

300

400

500

600

700

Emiss(e) cPmiss(MeV)100150

AS = (2 9stat 5syst) × 103 AL = (3322 58 47) × 10-6

Re(x) = (.6 3.1stat 1.8syst) 10

KLOE

51

52

First observation CMD-2 of PLB462,371(1999)

KLOE: evidence of f0 in charge asymmetry

• data MC: ISR+FSR MC: ISR+FSR+ f0(KL)

M() MeV

SgKK

gSKK

gSPP

PK

KP

SV

gVS

gSpp

Pe+

e-

f0 more coupled to kaons than to pions

: Looking for f0

M() MeVf0(980) region

M() (MeV)

53

First observation SND in 00PLB 440,442 (1998)SND BR()= (1.14 0.10 0.12)10-4

Looking for f0

CMD2 PLB463,380 (1999) BR()=(0.92 0.08 0.06)10-4

SND PLB485,349 (2000) (2 107 BR()= (1.221 0.098 0.061) 10-4

KLOE PLB537,21 (2002) (5 107 ) BR()=(1.09 0.03stat .05syst)104

M (MeV)

54

First observation in by SND PLB 438,441CMD-2 PLB462,380 (1999)BR() = (0.90 0.24stat 0.10syst) 10–4

Looking for a0(980)→π0

KLOE PLB536,209 (2002) 16 pb–1 ’00 dataBR() = (8.5 0.5stat 0.6syst) 10–5

•New data (statistics x 20)

first observation

55

Zweig rule: decay KK prefered dispite of the phase sapce,because consttitunent qurks have to survivef = ss

56

f0(980) K+K-[ 2m(K)~m(f0)~m() ] expected BR ~ 10-6

K0K0““ ~ 10-8

a0(980) K+K- expected BR ~ 10-6

K0K0 expected BR ~ 10-8