Phi Radiative decays at KLOE

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• Phi Radiative decays at KLOE

Camilla Di Donato for the KLOE Collaboration
Sezione I.N.F.N. Napoli
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Outline

• Scalar mesons at f-factory
• f ? f0(980)g ?p p- g PLB634 (2006) 148
• f ? f0(980)g ?p0 p0 g
• Pseudoscalar mesons at f-factory
• h mass measurement
• BR(f ? h?g) and mixing angle

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Scalar mesons at a f-factory
How a f-factory can contribute to the
understanding of the scalar mesons

• Scalar Mesons Spectroscopy
• f0(980), s(600) and a0(980)
• are accessible (k not accessible)
• through f ? Sg
• Questions
• 1. Is s(600) needed to describe
• the mass spectra ?
• 2. couplingsof f0(980) and
• a0(980) to f ? ssgt and to KK,
• pp and hp.
• ? 4-quark vs. 2-quark states

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The scalar amplitude description
We use three different approaches in the
description of the scalar amplitude
g

• Kaon-loop KL (Achasov-Ivanchenko, NPB315 1989)
  for each scalar meson S there are three free
  parameters of the fit gSpp, gSKK, MS
• No-Structure NS (by G.Isidori and L.Maiani) a
  modified BW a polynomial continuum gfSg, gSpp,
  gSKK, MS pol. cont. parameters
• Scattering Amplitudes SA
• (M.E.Boglione, M.R.Pennington, Eur. Phys.,
  J. C30 (2003))
• A ? (a1b1m2c1m4) T(pp?pp)
  (a2b2m2c2m4) T(pp?KK) ? pole residual gf

p
5
pp-g _at_ large angle looking for f0
Events/1.2 MeV

• 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
• of M (??-) spectrum from the
• expected ISR FSR shape
• 676,000 events selected (20012002)

M(pp) (MeV)
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Fit to the m(pp) spectrum

• (491 bins, 1.2 MeV wide,
• m(pp) 420 to 1009 MeV)
• Fit ISR FSR rp
• scalar interf(SCAL FSR)
• Kaon-Loop and No-Structure fits
• Good description in both cases
• of signal and background
• (Kuhn-Santamaria)
• negative interference
• The introduction of a s(600)
• doesnt improve the fit.

KL fit
NS fit


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Scattering Amplitude Fit
gf 6.6 10-4 ? BR ( f?f0 g) BR ( f0 ? pp- )
3 10-5 similar conclusion from Boglione
Pennington analysis of p0p0g data (KLOE SND)
Summarizing The peak at 980 MeV is well
interpreted in both KL and NS approaches as due
to the decay f ? f0(980)g with a negative
interference with FSR. The couplings suggest the
f0(980) to be strongly coupled to kaons and to
the f. Scattering Amplitude gives a marginal
agreement.
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Forward-Backward asymmetry
A (N(qgt90o) N(qlt90o)) / (N(qgt90o)
N(qlt90o)) pp- system A(ISR) C-odd
A(FSR) A(scalar) C-even Cross-section A(
tot)2 A(ISR) A(FSR) A(scalar)2
FB asymmetry vs. m(pp) ?Clear signal 980MeV ?
Interesting comparison with Phokara MC simulation
zoom

• Data
• Simulation FSRISR
• Simulation FSRISR
• scalar(KL) (G. Pancheri,
• O. Shekhovtsova, G. Venanzoni,
• hep-ph/0506332)

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p0p0g final state VMD vs scalar
450 pb-1 from 2001 2002 data taking
400k events Two main contributions to
p0p0g final state _at_ Mf
KLOE preliminary
f?Sg?p0p0g
vs 1019.6 MeV
ee-?wp0?p0p0g
New analysis scheme Allow for interference
between e e- ? wp0 and f ? Sg Bi-dimensional
analysis of Dalitz-plot m(p0p0) vs m(p0g)
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p0p0g final state VMD vs scalar

• Fit with No-Structure approach in progress
• Fit Dalitz plot with improved Kaon loop
  parametrization
• (Achasov, Kiselev hep-ph/0512047)
• Insertion of a KK scattering phase
• New parametrization of pp scattering phase
• Scalar contributions f0(980) and s(600)
• Combined fit to pp scattering data and to
  already published KLOE data on f?Sg gives six
  sets of parameters able to describe both
  distributions

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K-Loop fit f0s (dalitz-slices) _at_ ?1019.6 MeV
KLOE preliminary

• Free parameters Mf0, g_f0pp-, g_f0KK-, VMD
  description
• pp/KK phases and s(600) fixed to Achasovs
  results

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KL fit results
KLOE preliminary

• parameter values are from best fit
• The first error is statistical error from fit,
  the second one reflects the changes related to
  the other fit variants with acceptable c2

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Pseudoscalar mesons at f-factory

• h mass measurement
• Br(f?h?g)/Br(f?hg) with p p- 7g final state
• Pseudoscalar mixing angle.

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h mass measurement
Large discrepancy between the two most precise
measurements GEM measurement M? (547.311
0.028 0.032) MeV/c2 Reaction used p d ? 3He
? M. Abdel-Bary et al., Phys. Lett. B 619
(2005) 281-287 NA48 measurement Using ??3??
from ?????p ? ????n M? (547.843 0.030
0.041) MeV/c2 A, Lai et al., Phys. Lett. B 533
(2002) 196

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Measurement method

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Mh measurement _at_ KLOE

• Kinematic fit applied on f ?ggg events
• h and p0 selected by looking at different Dalitz
  plot regions

c2/ndf 304/257
p0
p0
h
Mgg (MeV)
m ( 134.956 ? 0.018 ) MeV s ( 1.66 ? 0.005 )
MeV
E1ltE2ltE3
c2/ndf 146/161
h
m ( 547.708 ? 0.014 ) MeV s ( 2.143 ? 0.012 )
MeV
Mgg (MeV)

Mgg (MeV)
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Mh measurement _at_ KLOE
KLOE preliminary
2001-2002 data sample divided into 8 periods,
each of 50 pb-1
M(p0) ( 134990 ? 6stat ? 30syst )
keV M(p0)PDG ( 134976.6 ? 0.6 ) keV
M(h) ( 547822 ? 5stat ? 69syst ) keV

• Systematics mainly from vs and vertex position
• - EMC linearity in progress
• NA48 compatibility 0.24 s

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BR(f?h?g)/ BR(f?hg)

• f?h'g, h' p p-h, h3p0
• h' p0 p0h, h pp-p0
• f?hg, h 3p0

• Signal selection
• charged vertex in a cylinder with a 4
  cm radius and a 16 cm height around the
  interaction point
• 7 prompt photons t r/c lt 5st and
  21? lt qg lt 159?
• anti KSKL tag
• No way to separate radiative g and g from p0

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Signal extraction data 2001-2002
427 pb-1 _at_ vs Mf Nobs 3750 observed Nbkg
345 estim. bkg Nsig(Nobs -
Nbkg)3405 65stat 28syst
f?h'g, h' p p-6g
wrong combination
h' mass distribution after wrong mass combination
subtraction
KLOE preliminary

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Results
KLOE preliminary
Systematics dominated by knowledge of h,h
branching ratios
Previous KLOE results Phys. Lett. B541 (2002)
45-51

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Mixing angle and h gluonic content
Using the Bramon approach (A.Bramon et. al. Eur.
Phys. J. C7, 271(1999)) we extract mixing angle
KLOE preliminary
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Conclusions

• Extensive study of f0(980) properties with
  2001-2002 KLOE data
• Clear evidence of f ? f0 g ? p p- g both in pp
  invariant mass and in the forward-backward
  asymmetry. Mpp fitted with three different
  theoretical approaches PLB634 (2006) 148
• Preliminary results on f ? S g ? p0 p0 g fit to
  Dalitz plot with improved kaon loop model
• Perspectives with our new data sets
• 2 fb-1 _at_ Mf search for f0 / a0 ? KK
• Energy scan (4 points - 10 pb-1 each - in the
  1010-1030 MeV range) improved study of the
  vs-dependence of the cross-section
• Off-peak data (200 pb-1 1000 MeV) search for gg
  ? p0p0
• Measurement of ? mass KLOE preliminary result is
  in agreement with NA48 measurement
• ????? in ??- 7 ? final state, in agreement
  with the KLOE previous result in ??- 3 ? final
  state Pseudoscalar mixing angle

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KL fit results f0s (the six variants), Sg term
Fixed M, G s
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KL fit results VDM/Sg compositions
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Fit function the Achasov parametrization