Phi meson physics Marianna Testa University of Roma La Sapienza & INFN for the KLOE collaboration...
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Transcript of Phi meson physics Marianna Testa University of Roma La Sapienza & INFN for the KLOE collaboration...
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
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
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
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