KLOE results on
f0(980) , a0(980) scalars and
h decays
S. Giovannella (LNFINFN)
for the KLOE Collaboration
 Study of the f0(980) , a0(980) mesons
 Dynamics of h→ppp decay
 BR of h→p0gg
RENCONTRES DE MORIOND 2005 – QCD and Hadronic Interactions
La Thuile, 12–19 March 2005
DAFNE: the Frascati f-factory
 e+e– collider @ s 1020 MeV  M
 peak  3 mb
 2004 best: Lpeak = 1.2 × 1032 cm-1s-1
 L(
pb-1
)
0BR = 83%
1-
0+
F(1020)
a0(980)
KK
f0(980)
h'(960)
BR = 1.3%
h(550)
r(770)
BR = 15%
p0
 Lint(01/02) = 450 pb-1
 Lint (2004) = 700 pb-1
 2005: data taking in progress
S. Giovannella - MORIOND QCD - 12-19 March 2005
 1.5 ×109 f in 2001/
 2.3 ×109 f in 2004
2
The KLOE experiment
The KLOE design was driven by the measurement of direct CP violation through
the double ratio: R = G(KL p+p) G(KS p0p0) / G(KS p+p) G(KLp0p0)
DRIFT CHAMBER:
• Helium based gas mixture
• dpt / pt < 0.4%
• xy  150 mm ; z  2 mm
E.M. CALORIMETER:
• E / E = 5.4% / (E(GeV))
• t = 55 ps / (E(GeV))  40 ps
• 98% solid angle coverage
• PID capabilities
Magnetic field:
B = 0.52 T
S. Giovannella - MORIOND QCD - 12-19 March 2005
3
Light scalar mesons at KLOE
e+e-
→f
g+f0(980)
(I=0)
g+a0(980)
(I=1)
p+pp0p0
h p0
gg
p+p- p0
─
 f0(980) and a0(980) scalar mesons not easily interpreted as qq
states
 Other interpretations suggested:
──
 qqqq
states [Jaffe 1977]
─
 KK molecule [Weinstein, Isgur 1990]
Both BR(f→Sg) and scalar mass spectra are sensitive to their nature
[Achasov, Ivanchenko 1989]
S. Giovannella - MORIOND QCD - 12-19 March 2005
4
Light scalar mesons at KLOE
Properties of light scalars can be investigated by fitting the Dalitz plot
of the three body PPg final state or the MPP spectra to extract the
relevant couplings.
We use two models:
2) “No Structure”
1) Kaon Loop
[Isidori-Maiani, private comunication]
[Achasov-Ivanchenko, NPB315 (1989) 465]
K+
S
K-
P
P
gfKK
gSKK
gSPP
S. Giovannella - MORIOND QCD - 12-19 March 2005
e+
e-
V
S
P
gVSg
gSpp
g
S described as a standard BW (fixed GS)
+ higher order corrections
5
Fit to the M(hp) spectra
hgg
(BR = 39.43%) 1.2  104 events
h→π+π-π0 (BR = 22.6% )
4180
2001+2002 data:
395+10 pb-1
events
Kaon Loop
hgg
hgg
hp+p-p0
hp+p-p0
No Structure
hgg
hp+p-p0
Mhπ (MeV)
√s (MeV)
2
dσ
0
0
0
 (  a0g  hp g )  (  rp  hp g )
dm
S. Giovannella - MORIOND QCD - 12-19 March 2005
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The p0p0g final state
450 pb-1 from 2001 – 2002 data taking
~ 400k events
Two main contributions to p0p0g final state @ Mf:
f→Sg→p0p0g
√s = 1019.6 MeV
e+e-→wp0→p0p0g
S. Giovannella - MORIOND QCD - 12-19 March 2005
7
p0p0g Dalitz: kaon
Fit to the
loop
Fit to the Dalitz plot includes:
Statistical errors only
1. scalar term [f0(980)]
2. VDM contributions
e+
w
p2(1)
g
e─
r/r
p1(2)
p2(1)
e+
r
e─
f/w/w g
p1(2)
3. All interference terms
S. Giovannella - MORIOND QCD - 12-19 March 2005
 Data
 Fit
 VDM well under control
 Scalar term not well reproduced
8
Fit to the p0p0g Dalitz: kaon loop
Kaon loop model including s(600) according to PRD 56 (1997
significantly improves the fit!
 Data
 Fit
Statistical errors only
S. Giovannella - MORIOND QCD - 12-19 March 2005
9
Fit to the p0p0g Dalitz:no
structure
Also in this case we fit the p0p0g Dalitz with the scalar term, the
VDM contributions and their interferences
f0 + s (KL)
Scalar (NS)
Statistical errors only
 Data
 Fit
 Similar fit quality w.r.t. KL including s(600)
 Low mass tail less evident
S. Giovannella - MORIOND QCD - 12-19 March 2005
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The p+p-g final state
 e+e-→ p+p-g events with the
photon at large angle (45<g<135)
Events/1.2 MeV
 Main contributions:
 ISR (radiative return to r, )
 FSR
 Search for the f0 signal as a deviation
on M(p+p-) spectrum from the
expected ISR + FSR shape
f0(980) region
M(pp) (MeV)
 676,000 events selected (2001+2002)
 Expected interference pattern of svis vs √s
in the signal region Mpp[9001000 MeV]
S. Giovannella - MORIOND QCD - 12-19 March 2005
√s (MeV)
11
Fit to p+p-g
Fit of the full Mpp spectrum with:
d  d 
 d 
  0
 

 bckg(p p p  m m g )  


dm
 d 


 dm  Scalar  dm  int .Scalar FSR
 dm  ISR FSR rp
KL
NS
Full spectrum
Signal region
ISR+FSR
S. Giovannella - MORIOND QCD - 12-19 March 2005
12
Scalar mesons: coupling to the f
In the “no structure” approach the crucial parameter is the
coupling of the scalars to the f (i.e. to the s quark)
Meson
p0
h
h
a0
f0
gMg (GeV-1)
0.12
0.66
0.70
1.3
1.8 – 2.3
S. Giovannella - MORIOND QCD - 12-19 March 2005
Increasing
strange quark
content
Large coupling values!
13
The h→ppp decay in cPT
The amplitude of the h→ppp decay occurs primarily due to the d-u
quark mass difference. From lowest order Chiral Pertubation Theory:
1 m K2
2
2 M ( s, t , u )
A( s, t , u )  2 2 (mp  m K )
Q mp
3 3Fp2
with
2
2
ˆ
m

m
Q 2  s2
md  mu2
and, at L.O. ,
3s  4mp2
M ( s, t , u )  2
mh  mp2
A good understanding of M(s,t,u) can lead to a very accurate
determination of Q:
G(h  3p )  A  Q 4
2
S. Giovannella - MORIOND QCD - 12-19 March 2005
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The h→ppp decay @
KLOE
The
h meson is produced via f→
hg
(17
Mevts in 2001/2002)
Final state for h
Final state for h
→
→
p+p-p0 : p+p-ggg
:
p 0p 0p 0
7g’s
In both decays the physical background is almost negligible
f→
hg →
-p0
0g
p 0p
pp
p0+
selection:
 2 track vertex + 3g candidates
 Kinematic fit
p0p0p0 selection:
 7 photon candidates
 Kinematic fit
S. Giovannella - MORIOND QCD - 12-19 March 2005
15
The h→p+p-p0 Dalitz plot
Resolution:
Dalitz shape
“core”
sXY = 0.027
0.018
X(T+-T-) , YT0
Efficiency  36% , almost flat
S. Giovannella - MORIOND QCD - 12-19 March 2005
B/S  0.8%
16
Fit to the h→p+p-p0 Dalitz
plot
|A(X,Y)|2 = 1+aY+bY2+cX+dX2+eXY+fY3
c and e are C violating
Ndf
147
150
150
150
P2
(%)
a
b
c
d
e
f
60
1.072  0.006
0.007  0.005
0.117  0.006
0.006
0.004
0.0001  0.0029
0.0021
0.0003
0.047 0.006
0.005
0.004
0.006
0.008
0.  0.013
0.13 0.01
0.01
0.02
63
1.072  0.005
0.008 0.005
0.117  0.006
0.006
0.004

0.047 0.006
0.005
0.004

0.13 0.01
0.01
0.02
0.02
1.055  0.004 0.100 0.005
0.007 0.006 0.002 0.004
0
1.013  0.003
0.007 0.004
0.120  0.005
0.023  0.
S. Giovannella - MORIOND QCD - 12-19 March 2005



0.12 0.01
0.02
0.02

0.043 0.006
0.003
0.004


17
Q evaluation
Using the preliminary KLOE result presented @ ICHEP04 :
[B.V. Martemyanov and V.S. Sopov, PRD 71 (2005) 017501] :
Q = 22.8 ± 0.4
This result implies a violation of the Dashen theorem (QDT=24.2)
based on DMp(e.m.)=DMK(e.m.) and is in agreement with:
Q = 22.0 ± 0.6
Q = 22.4 ± 0.9
Q = 22.7 ± 0.8
[J.Donoghue and A.Perez, PRD 55 (1997) 7075]
[J.Bijnens and J.Prades, NPB 490 (1997) 239]
[J.Kambor., C.Wiesendanger and D.Whyler, NPB 465 (1996) 215]
[A.V.Anisovich and H.Leutwyler, PLB 375 (1997) 335]
The theoretical error is currently dominated by PDG error on G(h→ppp
S. Giovannella - MORIOND QCD - 12-19 March 2005
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The h→p0p0p0 Dalitz plot
The Dalitz plot density is described with a single parameter: |A|2
 1 + 2a z
with:
2 3  3Ei  M h
z 
3 i 1  M h  3M p
2
2

r
 
2

r max

z[ 0 , 1 ]
Ei : Energy of the i-th pion in the h rest frame
r : Distance from the center of the Dalitz plot
rmax : Maximum value of r
S. Giovannella - MORIOND QCD - 12-19 March 2005
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Fit to the h→p0p0p0 Dalitz
plot
350 pb-1 of 2001-2002 data, using an high purity sample on the
photon pairing in p0 → Purity = 98.5% , e = 4.5%
a = -0.013 ± 0.005stat
Current best measurement from Crystal Ball:
S. Giovannella - MORIOND QCD - 12-19 March 2005
 0.004syst
a = -0.031 ± 0.004stat+syst
20
h→p0gg: a window on p6
cPT…
0
g
p2
L2 contributions
at tree level:
Coupling proportional to the
charges, zero also for
L4 @ tree level.
p4
p6
1-loop contributions from L2
vertices, suppressed by G
parity conservation and kaon
mass suppression:
Gp-loops = 0.84 ×10-3 eV
GK-loops = 2.45 ×10-3 eV
p
g
= 0 (Q = 0)
h8
g
p+,K+ p0
g
h8
p-,K-
p0
L6 coefficients determined by the
g
meson propagator. Th. expectations: h
G6VMD = ( 0.42 ± 0.20 ) eV
G6ENJL = ( 0.58 ± 0.3 ) eV
g
6
G Ch unit= ( 0.47 ± 0.10 ) eV
S. Giovannella - MORIOND QCD - 12-19 March 2005
g
h8
p0
g
21
… and an experimental challenge!
p  p  h  n
(CERN, Brookhaven, GAMS,
Crystal Ball)
p  d  p + p + h (67)
p  p  p  p +h (67,69)
K  p  L  h (70 AGS)
p  n  h  p (71)
p  n  p  n  h (80)
 hg (SND 01)
S. Giovannella - MORIOND QCD - 12-19 March 2005
22
Analysis of h→p0gg @
KLOE
f →
h g
}
p0
gg
5g final state
 ~ 8 pb (GAMS BR measurement)
Background candidates:
s (pb)
Process
e+e-→wp0
,
w→p0g
,
p0→gg
450
f→f0g , f0→ p0p0 ,
p0→gg
300
f→a0g , a0→ hp0 ,
h/p0→gg
260
f→hg , h→gg
Rejected with veto on
additional w-p0h
17000
Rejected with0energy
momentum conservation and likelihood
0
f→hg , h→ p p
13000 merged clusters
technique to identify
p0
S. Giovannella - MORIOND QCD - 12-19 March 2005
23
h→p0gg: BR evaluation
The shape of signal +
background after fit
well reproduces the data
NDATA = 735
Nbkg = 667  36
Nsig = 68  23
N(h3p0)  2,288,882
BR(h→p0gg) = ( 8.4 ± 2.7stat ± 1.4syst ) × 10-5
S. Giovannella - MORIOND QCD - 12-19 March 2005
24
BRh→p0gg: comparison with
models
[1] [2] [3]
[4] [5] [6] [7]
[8]
GAMS
(1984)
Statistical significance
[1] J. N. Ng et al.(1992)
99%
[2] J.N. Ng et
al (1993)
95%
[3-4] L. Ametller et al. (1992)
90%
Crystal Ball
(2004)
KLOE
[5] S. Bellucci68%
et al. (1995)
[6] E. Oset et al (2003)
[7] J. Bijnens et al. (1996)
[8] A. A. Belkov et al.(1996)
S. Giovannella - MORIOND QCD - 12-19 March 2005
KLOE 1s
KLOE 2s
KLOE 3s
P6 calculations
25
Conclusions/Outlook
 The f0(980), a0(980) scalar resonances are clearly observed in different
final states, indicating large values for the couplings with f
 We are analyzing an unprecedented statistics of h→3p decays,
determining
accurate values of the Dalitz plot slopes for p+p- p0 /p0 p0 p0
final states
 We measure a value of BR(h→p0gg) smaller than previous
measurement
and in agreement with ChPT p6 calculations
 A factor 5 improvement in statistics expected at the end of current run:
 Complection/extensions of the on-going analysis (including out of peak data)
 Search for S→KK
 Measure
of allQCD
main- 12-19
h BRs
rare/forbidden h decays (Nh ~ 90 Mevts )
S. Giovannella
- MORIOND
March+2005
26