Recent KLOE results on Hadron Physics

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QNP06 Madrid 09/06/06
Recent KLOE results on Hadron Physics
Cesare Bini Universita La Sapienza and INFN
Roma

• Outline
• The KLOE experiment at DAFNE
• Results on Scalar Mesons
• Results on Pseudoscalar Mesons
• Prospects for ee- at Frascati

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DAFNE the Frascati f - factory

• ee- collider with 2 separate rings ?s Mf
  1019.4 MeV
• 2 interaction regions
• 1.? KLOE
• 2.? DEAR (kaonic atoms)
• FINUDA (hypernuclei)

?Luminosity was delivered to the 3
experiments KLOE 2700 pb-1 FINUDA 250
pb-1 DEAR 100 pb-1 ?Luminosity has
increased up to 1.51032 cm-2s-1
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The KLOE experiment
The detector A large drift chamber A
hermetic calorimeter A solenoidal
superconducting coil
Drift Chamber (He-IsoBut. 2m 3m)
E.M. Calorimeter (lead-scintillating fibres)
Magnetic field
(SuperConducting Coil) 0.52 T
(solenoid)
STATUS March 2006 end of KLOE data taking 2500
pb-1 on-peak ? 8 109 f decays 200 pb-1
off-peak (energy scan 1 GeV run)
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Physics at a f factory a window on the lowest
mass mesons
Sketch of the f decays
Main decay channels Branching fraction
? KK- 49.2
KSKL 34.0
? rp pp-p0 15.3
? hg 1.301
? p0g 0.125
? hg 6.2 10-5
? p0p0g 1.1 10-4
? hp0g 8.3 10-5
radiative return to pp- radiative return to pp-
events Br.F. 8 109 ? 105 h, pp, hp
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Overview of KLOE physics

• (1) Kaon physics several fundamental physics
  items
• Extraction of the Vus element of the CKM matrix
  from
• 5 semi-leptonic decays of neutral and charged
  kaons
• ? test of CKM Unitarity
• ? CPT tests first measurement of KS
  semi-leptonic asimmetry
• Kaon interferometry in pp-pp- final states
• ? bounds on quantum decoherence CPT violation
• Reduced upper bound on KS ? p0p0p0 CP violating
  decay
• Precision measurement of KS ? pp- / KS ? p0p0
• Measurement of KL and KS ? gg ? ChPT test

450 pb-1 analysed 20 previous analyses
(2) Hadron physics ? Scalar Mesons (
a0(980), f0(980) s(500) ) ? Pseudoscalar
Mesons ( p0, h, h ) ? Vector Mesons (
properties of r(770), w(780) ) (3)
Measurement of the Hadronic Cross-Section below 1
GeV ? hadronic corrections to g-2
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Scalar Mesons
How a f-factory can contribute to the
understanding of the scalar mesons
Mass (GeV/c2)
f(1020)
Scalar Mesons Spectroscopy f0(980), s(500) and
a0(980) are accessible (k not accessible) through
f ? Sg Questions 1. Is s(500) 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 vs. KK
molecule
1.
a0(980)
f0(980)
k(800)
s(500)
0.
I0
I1/2
I1
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Scalar Mesons with KLOE

• ? f0(980)g ? pp-g
• ? p0p0g
• ? KK-g 2m(K)m(f0)m(f) ? expected BR
  10-6
• ? K0K0g 10-8

• ? a0(980)g ? hp0g
• ? KK-g ?expected BR 10-6
• ? K0K0g ? 10-8

• ? s(500)g ? pp-g
• ? p0p0g

General Comments ? fits of mass spectra are
needed to extract the signals this requires a
parametrization for the signal shape ? the
unreducible background is not fully known a
parametrization is required and some parameters
have to be determined from the data
themselves ? sizeable interferences between
signal and background
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The pp-g analysis P.L.B 634 ,148 (2006)
Event selection 2 tracks with qtgt45o missing
momentum qppgt45o (large angle) Each track is
pion-like (tracking, ToF and Shower shape) 1
photon matching the missing momentum ? 6.7 105
events / 350 pb-1
Particle identification p vs. e and m
(Likelihood Tof and Shower shape)
pions, muons
electrons
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The pp-g final state is dominated by Initial
State Radiation Final State Radiation The
f0(980) is observed as a bump in ds/dm(pp)
vs. m(pp) Ac vs. m(pp) -- Forward-Backward
asymmetry
f0(980) signal
Ac
Events
data MC no f0 MC with f0
m(pp) (MeV)
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Fit of the mass spectrum using 2 different models
for the scalar amplitude ? Kaon-Loop model
N.N.Achasov et al. mf0, gf0pp-,
gf0KK-, ? No Structure model G.Isidori
et al. mf0, gf0pp-, gf0KK-, gff0g, b0,b1 Free
parameters scalar amplitude background
An acceptable fit is obtained with both
models P(c2)(KL)4.2 P(c2)(NS)4.4
?Mass values ok
? gf0KK-gt gf0pp- ? Large coupling to the f
B.R.(f ? f0(980)g ? pp-g) 2.1 ? 2.4 10-4
(from integral of Amplitude2)
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The p0p0g analysis
Event selection 5 photons with qggt21o no
tracks Kinematic fit ? energy-momentum
conservation Kinematic fit ? p0 masses choice
of the pairing. ? 4 105 events / 450 pb-1 ?
analysis of Dalitz-plot
2 components in the Dalitz-plot
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Fit of the Dalitz-plot (without rejecting wp0)
using the same 2 models ? Improved Kaon-Loop
model (introducing the f?s(500)g) ? No
Structure model Parameters mass and couplings
( mf0, gf0pp-, gf0KK-, gff0g) background The
s(500) parameters are fixed. The fit is repeated
by changing them
2-dim fit shown slice bt slice. A good fit is
obtained with both models P(c2)(KL)14 P(c2)(NS
) 4
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Fit results
f0(980) param. NS model KL model
mf0 (MeV) 981 987 976 987
gffg (GeV-1) 2.5 2.7 -
gfpp- (GeV) 1.3 1.4 1.4 2.0
gfKK (GeV) 0.1 1.0 3.3 5.0
Rg2fKK /g2fpp- 0. 0.9 3.0 7.3

• Comments
• ? s(500) is needed in KL fit p(c2) 10-4 ? 14
  !
• (best s parameters are M462 MeV, G300 MeV)
• ? f0(980) parameters agree with pp-g analysis KL
  fit
• again R gt 1 (gf0KK gt gf0pp-)
• ? NS fit gives large gff0g but Rlt1 (??)
• ? BR extracted ? integral of scalar amplitude2

• BR( p0p0g) 1/2 BR(pp-g) neglecting KK, we
  add the 2 BRs
• ? BR(f ? f0(980)g) (3.1 3.5) 10-4
• ? G(f ? f0(980)g) 1.2 1.6 keV

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The hp0g analysis
Simultaneous analysis of h?gg and h?pp-p0
channels Pts. data 450 pb-1 20 published
results, hist KL fit
The spectra are dominated by the a0
production (negligible unreducible backgrounds).
Work in progress, results soon
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Scalar Mesons Summary and Outlook

• Complete analysis of f ? f0(980)g with f0(980) ?
  pp- and p0p0
• ? good description of the scalar amplitude with
  KL model
• ? large couplings to Kaons hint of a large
  s-quark content
• ? s(500) is still required to describe the p0p0
  Dalitz-plot
• ? NS fit suggests large coupling of f0(980)
  to the f
• 2) Work in progress to
• ? make a combined analysis of f0(980) ? pp- and
  p0p0
• ? complete the analysis of f ? a0(980)g with
  a0(980) ? hp0? study the decay chain f ?
  f0(980)a0(980)g ? KKg
• (expected sensitivity down to 10-8)
• 3) Further studies
• ? search for ee- ? ee-p0p0 events (gg ? p0p0 )
  using the
• run _at_ ?s 1 GeV (off-peak less background)
• search for the s(500) F.Nguyen et al. 2005

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Pseudoscalar Mesons
Large samples of p0, h and h through the
radiative decay f ? Pg ? 8 107 h ? 9 106
p0 ? 4 105 h
List of the analyses done or in progress
Measurement of the h (and p0) masses ? this talk
Measurement of the h h mixing angle in pp- 3g Phys.Lett.B541 (2002) 45
Measurement of the h h mixing angle in pp- 7g ? this talk
Dynamic of the decay h ? pp-p0 AIPConf.Proc.814463,2006
Dynamic of the decay h ? p0p0p0 AIPConf.Proc.814463,2006
Measurement of the BR(h ? p0gg) AIPConf.Proc.814463,2006
Upper limit on the C-violating decay h ? ggg Phys.Lett.B591 (2004) 49
Upper limit on the P(CP)-violating decay h ? pp- Phys.Lett.B606 (2005) 276
Study of the decay h ? pp-ee- in progress
Upper limit on the P(CP)-violating decay h ? p0p0 in progress
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Measurement of the h (and p0) masses
2 recent measurements done with different
techniques GEM (COSY) pd ? 3Heh ?
M(h)(547311 28 32) keV/c2 (missing mass
technique) NA48 (CERN) p-p? nh ?
M(h)(547843 30 41) keV/c2 (h ? 3p0
reconstruction) 8 s discrepancy dM(h)(532 41
52) keV/c2 (errors added in quadrature)
KLOE ???? ???? check with ???0?
?0??? Technique kinematic fit mostly based on
photon positions and timing ? energy-momentum
and vertex position from large angle Bhabha
scattering
3g Dalitz-plot
The p0 and the h peak are well defined
p0
h
Mass (MeV)
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Results (still preliminary)
The statistical uncertainty is negligible Systema
tic uncertainties from knowledge of ?s and vertex
position (work in progress to reduce it)
The p0 mass is well in agreement with PDG
value M(p0) ( 134990 ? 6stat ? 30syst )
keV M(p0)PDG ( 134976.6 ? 0.6 ) keV
The h mass is in agreement with NA48 and in
disagreement with GEM M(h) ( 547822 ? 5stat ?
69syst ) keV
KLOE NA48 GEM (see Kirillov _at_ QNP06)
h mass (MeV)
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Measurement of the h h mixing angle in pp- 7g
using similar h and h decay chains
Method measurement of
Previous analysis h ? pp-h h ? gg ?
pp-3g h ? pp-p0 p0 ? gg ? pp-3g This
analysis h ? pp-h h ? p0p0p0 ?
pp-7g h ? p0p0h h ? pp-p0 ? pp-7g h
? p0p0p0 p0 ? gg ? 7g
427 pb-1 2001/2002 data N(hg) 1665000 ? 1300
(no bck) N(pp-7gs) 3750?60
(Nbckg 345) ? N(hg) 3405
61stat 28syst
h signal (10 bck)
h signal (no bck)
The systematic uncertainty is due to the
uncertainty on the intermediate BRs
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• Pseudoscalar mixing angle extracted using the
  parametrisation
• A.Bramon et al. 1999

Mixing angle
(2) Analysis of h gluonic content
E.Kuo, 2001
Before KLOE results
Including new KLOE result
X2Y2 0.93 0.06
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Prospects for ee- physics at Frascati
Short term program ? New FINUDA Run 2006
2007 previous statistics 5 ? SIDDHARTA Run
2007 2008 upgraded version of DEAR (see
C.Curceanu talk _at_ QNP06) ? ??? gt 2009
Discussions are open in the laboratory about a
possible continuation of a low-energy ee-
program Present project DANAE (not
approved yet) ? higher luminosity f factory
(L1033 cm-2s-1) ? energy scan vs 1 2.5
GeV (L1032 cm-2s-1)
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3 Expressions of Interest have been
presented KLOE2 ? Kaon physics h / h
physics _at_ f ? gg physics hadronic
cross-section up to 2.5 GeV AMADEUS ? deeply
bound hypernuclei _at_ f DANTE ? baryon time-like
form factors (vs gt 1.9 GeV) Waiting for the
final decision of the laboratory. Any
contribution is welcome ! http//www.lnf.infn.it/
lnfadmin/roadmap/roadmap.html
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Spare Slides
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Scalar Mesons
Renewed interest after B-factory results new
scalar meson zoology above 2.3 GeV ?
reconsider the low mass spectrum
A 0 meson arises from a qq pair in a triplet
spin state (S1) and P-wave (L1)
Assuming 2 quarks interacting by a single gluon
exchange, other configurations are found Jaffe
1977

• ? Color triplet diquarks and anti-diquarks
• Attractive interaction between diquark and
  anti-diquark
• giving a color singlet
• ? it is possible to build up 4-quarks scalar
  meson

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Analysis of the mass spectra of the lowest mass
mesons
Pseudoscalar multi-plet
Vector multi-plet
Scalar multi-plet s(500), k(700), f0(980),
a0(980)
Provided s and k are there the scalars have
an Inverted Spectrum
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Inverted Mass spectrum ? hint of a 4q picture
Building Rule
Mass
Q0 Q0 Q1 Q-1 (the
f0(980) and a0(980))
add 2 Quarks s
Q0 Q1 Q0 Q-1 (the k(800))
add 1 Quark s
I30 Q0 (the s(500))
2 important consequences if 4q hypothesis is
correct ? the s(500) and the k(800) have to be
firmly established ? the s-quark content of f0
and a0 should be sizeable (? f0 and a0
couplings with f (ss) and with kaons N.N.Achaso
v and V.Ivanchenko 1989
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Definition of the relevant couplings (Sf0 or a0)
S to f gfSg (GeV-1) S to
kaons gSKKgSKK-gSK0K0 (GeV) f0 to pp
(I0) gf0ppv3/2 gf0pp-v3 gf0p0p0 (GeV) a0 to
hp (I1) ga0hp (GeV) Coupling
ratio Rf0(gf0KK-/ gf0pp-)2 Ra0(ga0KK-/
ga0hp)2