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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, 1219 March 2005
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DAFNE the Frascati f-factory

• ee collider _at_ ?s ?1020 MeV ? M?
• ?peak ? 3 mb
• 2004 best Lpeak 1.2 1032 cm-1s-1

? L(pb-1)

• Lint(01/02) 450 pb-1
• Lint (2004) 700 pb-1
• 2005 data taking in progress

• 1.5 109 f in 2001/2002
• 2.3 109 f in 2004

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The KLOE experiment
The KLOE design was driven by the measurement of
direct CP violation through the double ratio R
G(KL ?pp?) G(KS ?p0p0) / G(KS ?pp?) G(KL?p0p0)

• DRIFT CHAMBER
• Helium based gas mixture
• dpt / pt lt 0.4
• ?xy ? 150 ?m ?z ? 2 mm

• E.M. CALORIMETER
• sE / E 5.4 / ?(E(GeV))
• st 55 ps / ?(E(GeV)) ? 40 ps
• 98 solid angle coverage
• PID capabilities

Magnetic field B 0.52 T
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Light scalar mesons at KLOE
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• 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

-
-
-
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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

1) Kaon Loop Achasov-Ivanchenko, NPB315
(1989) 465
2) No Structure Isidori-Maiani,
private comunication
S described as a standard BW (fixed ?S) higher
order corrections
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Fit to the M(hp) spectra
20012002 data ???? (BR
39.43) 1.2 ? 104 events 39510 pb-1
??pp-p0 (BR 22.6 )
4180 events
Kaon Loop
No Structure
????
????
????
??pp-p0
??pp-p0
??pp-p0
M?p (MeV)
vs (MeV)
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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 _at_ Mf
f?Sg?p0p0g
vs 1019.6 MeV
ee-?wp0?p0p0g
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Fit to the p0p0g Dalitz kaon loop
Fit to the Dalitz plot includes 1. scalar term
f0(980) 2. VDM contributions 3. All
interference terms
Statistical errors only
? Data ? Fit

• VDM well under control
• Scalar term not well reproduced

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Fit to the p0p0g Dalitz kaon loop
Kaon loop model including s(600) according to PRD
56 (1997) 4084 significantly improves the fit!
? Data ? Fit
Statistical errors only
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Fit to the p0p0g Dalitzno structure
Also in this case we fit the p0p0g Dalitz with
the scalar term, the VDM contributions and their
interferences
Statistical errors only
? Data ? Fit

• Similar fit quality w.r.t. KL including s(600)
• Low mass tail less evident

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The pp-g final state

• ee-? ??-? events with the
• photon at large angle (45?lt??lt135?)
• Main contributions
• ISR (radiative return to ?, ?)
• FSR
• Search for the f0 signal as a deviation
• on M(??-) spectrum from the
• expected ISR FSR shape
• 676,000 events selected (20012002)

Events/1.2 MeV
M(pp) (MeV)

• Expected interference pattern of svis vs vs
• in the signal region Mpp?900?1000 MeV

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Fit to pp-g
Fit of the full Mpp spectrum with
NS
KL
Full spectrum
Signal region
ISRFSR
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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)
Increasing strange quark content
Large coupling values!
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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
with
and, at L.O. ,
A good understanding of M(s,t,u) can lead to a
very accurate determination of Q
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The h?ppp decay _at_ KLOE
The h meson is produced via f? hg (17 Mevts in
2001/2002) Final state for h ? pp-p0
??-??? Final state for h ? p0p0p0
7gs In both decays the physical background is
almost negligible

• pp-p0 selection
• 2 track vertex 3g candidates
• Kinematic fit
• p0p0p0 selection
• 7 photon candidates
• Kinematic fit

f? hg ? p0p0p0g
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The h?pp-p0 Dalitz plot
Resolution
Dalitz shape
core sX 0.018
X?(T-T-) , Y?T0
B/S ? 0.8
Efficiency ? 36 , almost flat
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Fit to the h?pp-p0 Dalitz plot
A(X,Y)2 1aYbY2cXdX2eXYfY3
KLOE Preliminary
c and e are C violating
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Q evaluation
Using the preliminary KLOE result presented _at_
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 (QDT24.2) based on DMp(e.m.)DMK(e.m.)
and is in agreement with Q 22.0 0.6
J.Donoghue and A.Perez, PRD 55 (1997) 7075
J.Bijnens and
J.Prades, NPB 490 (1997) 239 Q 22.4 0.9
J.Kambor., C.Wiesendanger and D.Whyler,
NPB 465 (1996) 215 Q 22.7 0.8
A.V.Anisovich and H.Leutwyler, PLB 375 (1997)
335 The theoretical error is currently
dominated by PDG error on G(h?ppp)
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The h?p0p0p0 Dalitz plot
The Dalitz plot density is described with a
single parameter A2 ? 1 2 a
z with 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
z ? 0 , 1
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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 ?? 0.004syst
KLOE Preliminary
Current best measurement from Crystal Ball a
-0.031 0.004statsyst
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h?p0gg a window on p6 cPT
L2 contributions at tree level
0 (Q 0)
p2
Coupling proportional to the charges, zero also
for L4 _at_ tree level.
1-loop contributions from L2 vertices, suppressed
by G parity conservation and kaon mass
suppression
p4
Gp-loops 0.84 10-3 eV GK-loops 2.45 10-3 eV
L6 coefficients determined by the meson
propagator. Th. expectations G6VMD ( 0.42
0.20 ) eV G6ENJL ( 0.58 0.3 ) eV G6Ch
unit ( 0.47 0.10 ) eV
p6
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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) f hg (SND
01)
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Analysis of h?p0gg _at_ KLOE

5g final state s 8 pb (GAMS BR measurement)
Background candidates
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h?p0gg BR evaluation
The shape of signal background after fit well
reproduces the data
NDATA 735 Nbkg 667 ? 36 Nsig
68 ? 23 N(??3p0) 2,288,882
BR(h?p0gg) ( 8.4 2.7stat 1.4syst ) 10-5
KLOE Preliminary
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BRh?p0gg comparison with models
1
2
3
4
5
6
7
8
GAMS (1984)
Crystal Ball (2004)
KLOE
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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 pp- 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 all main h BRs rare/forbidden h
  decays (Nh 90 Mevts )
• Limit on gluonium content in h?
  BR(f?h?g)/BR(f?hg)