KLOE results on hadron physics

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KLOE results on hadron physics
MENU07, Julich 11/09/2007

• Cesare Bini
• Università La Sapienza and INFN Roma

• Outline
• The KLOE experiment
• Results on pseudoscalar mesons
• Results on scalar mesons
• Prospects

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1. The KLOE experiment at DA?NE

• DAFNE _at_ Frascati Laboratories
• ee- collider with 2 separate rings
• ?s Mf 1019.4 MeV
• Luminosity up to 1.51032 cm-2s-1
• 2 interaction regions
• 1. KLOE 2700 pb-1
• 2. DEAR (kaonic atoms) 100 pb-1
  FINUDA (hypernuclei) 1100 pb-1

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) ?
December 2006 - June 2007 FINUDA run ? Now
machine tests and preparation of SIDDHARTA
(kaonic atoms) run
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The KLOE 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)
The KLOE physics program Kaon physics CP and
CPT violation, CKM unitarity, rare decays, ChPT
tests Hadron physics lowest mass pseudoscalar,
scalar and vector mesons Hadronic cross-section
below 1 GeV hadronic corrections to g-2
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2. Results on pseudoscalar mesons.

• The lowest mass pseudoscalar mesons (JPC0-)
  are accessible
• at a ? - factory through the decays
• B.R. Nev KLOE (2.5 fb-1)
• ????KK- 0.49 3.7 ? 109
• ????K0K0 ??KSKL 0.33 2.5 ? 109
• ?????? 1.3 ? 10-2 9.7 ? 107
• ??????? 1.2 ? 10-3 9.0 ? 106
• ?????? 6.2 ? 10-5 4.6 ? 105

Results presented here 2.1 Precision
measurement of the ? mass 2.2 Improved
measurement of the ? - ? mixing 2.3 Dynamics of
? ??3? decays 2.4 Measurement of KS ???? 2.5
Other analyses in progress (????????,
???????-ee-)
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2.1 Precision measurement of the ??mass
Motivated by the discrepancy between the two best
measurements NA48 (2002) M(?) 547.843 0.030
0.041 MeV GEM (2005) M(?) 547.311 0.028
0.032 MeV (? gt10 ?, PDG average gives a scale
factor of 5.8 !) Recently a new measurement has
been presented by CLEO CLEO (2007) M(?)
547.785 0.017 0.057 MeV

• KLOE method analysis of fully neutral 3? events
• ??????? with ??????
• ???????? with ???????
• 3 clusters in the calorimeter only.
• Kinematic fit with 4 constraints gt energies by
  cluster positions
• Discrimination between ? and ?? very easy from
  Dalitz plot.
• Absolute energy scale from the ee- center of
  mass energy ?s
• (kinematic fit input) - calibrated comparing M(?)
  obtained by the
• energy scan to the PDG value

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3? Dalitz plot
? mass peak
KLOE final result M(?) 547.873 0.007
0.031 MeV Systematic error due to - space
uniformity - Dalitz plot cuts. ?? mass check
M(??) 134.906 ? 0.012 ? 0.048 (well compatible
with PDG value)
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2.2 Measurement of the h h mixing
KLOE method measurement of
2002 result (Phys.Lett.B541,45) Lint 16 pb-1
, ??????? final states 2007 result
(Phys.Lett.B648,267) Lint427 pb-1 , ???????
final states
Errors are now dominated by intermediate ? and
? B.R.s (BR(? ??????) known _at_ 3, BR((?
??????) _at_ 5.7)
() evaluated according to A.Bramon et al.,
Eur.Phys.J. C7, 271 (1999)
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Constrain to the ? gluonium content
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2.3 Dynamics of the ????3? decay
????'???3? decay ? isospin violation in strong
interactions mu ? md ? ms A test of low energy
effective theories of QCD
KLOE has studied with high statistics the
dynamics of both channels
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Fit results of the ?? ? ???????Dalitz plot
Including systematic errors a-1.090 ? 0.005
0.008 -0.019 b 0.124 ? 0.006 ? 0.010 d 0.057 ?
0.006 0.007 -0.016 f 0.14 ? 0.01 ? 0.02
Comments 0. the odd terms (c and e) in X are
compatible with 0 (no asymmetries) 1. the
quadratic term in X (d) is unambiguosly different
from 0 2. the cubic term in Y (f) is needed to
get an acceptable fit 3. the ba2/2 (current
algebra rule) is largely violated. According to
B.Borasoy and R.Nissler (Eur.Phys.J.A26 (2005)
383) it is difficult to accomodate such a small b
value in a ChPT approach
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Dalitz plot asymmetries gt test of C invariance
Left-Right C-invariance Quadrant C-invariance
in ?I2 amplit. Sextant C-invariance in
?I1 amplit. (see J.G.Layter et
al.,Phys.Rev.Lett.29 (1972) 316)
KLOE results x 5 statistics respect to best
previous experiment
All asymmetries are compatible with 0 up to the
10-3 level
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Fit results of the ?? ? ???????slope
The slope is evaluated by comparing the z
distribution of the data with a Montecarlo
simulation with ?0 (pure phase space) ? High
sensitivity to the value of M(?) (Dalitz plot
contour)
MC with M(?)547.3
MC with M(?)547.822
New result ? -0.027 ? 0.004 0.004 -0.006
gt in agreement with Crystal Ball
(?-0.031?0.004)
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2.4 Measurement of the decay KS ? ???
BR estimated by ChPT _at_ order p4 (G.DAmbrosio,
D.Espriu, Phys.Lett.B175 (1986)27)
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2.5 Others (2 flashes on other ongoing KLOE
analyses)

• ? ? ??-ee- signal observed
• 1500 events expected with 2.5 fb-1

Few sensitivity on plane asymmetry (CP
violation, D.Gao, Mod.Phys.Lett.A17 (2002) 1583)
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3. Results on scalar mesons.
KLOE contribution to the understanding of the
lowest mass scalars f0(980), a0(980), ?(500)
through radiative decays in pairs of
pseudoscalars

• ? S? ? ????? (I0)???????f0 ? ?
• ? ????? (I0) f0 ?
• ? ???? (I1) a0
• ? KK-? (I0,1) f0 a0
• ? K0K0? ?? (I0,1) ???f0 a0

Mass (GeV/c2)
f(1020)
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a0(980)
f0(980)
Motivations 1. f ? ssgt ?scalar quark
composition 2. Search for evidence of ?(500)
k(800)
s(500)
Results presented here 3.1 Review of KLOE
results on f0(980) 3.2 High statistics study
of ?????(preliminary) 3.3 Search for the
decay ? ? K0K0? ?
0
I0
I1/2
I1
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3.1Review of KLOE results on f0(980)
KLOE has observed the decay ? ? f0(980)? in
?????and ?0?0 channels ?????? Phys.Lett.B634
(2006) 148 ???????? Phys.Lett.B537 (2002) 21
Eur. Phys.J. C49 (2006) 433
??????FB asymmetry
??????Dalitz plot
f0(980)
??????mass spectrum

• Fit results
• 1.The Kaon-Loop well describes the mass spectra
• 2.The f0(980) is strongly coupled to the s quark
  gf0KK gt gf0pp-, g?f0??is large
• 3.The scalar amplitude has a large low mass tail
  (mlt600 MeV) that can be
• interpreted as due to the ?(500) (not clear
  results yet)

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3.2 High statistics study of ? ? ???? the
a0(980).
Pure final state, expected dominance of a0(980)
intermediate state

• Selection of
• 1. ???? events with ? ???? fully neutral 5?
  events
• 2. ???? events with ? ???????? 2tracks and 5?
  events
• Background subtraction 18 in sample 1, 13 in
  sample 2
• Event counting 18400 in sample 1,
  3600 in sample 2

B.R.(? ? ????)(1) (6.92 ? 0.10stat ? 0.20syst)
?10-5 B.R.(? ? ????)(2) (7.19 ?
0.17stat ? 0.24syst) ?10-5 In good agreement,
(part of the systematic errors are common). Error
improvement 9 (Phys.Lett.B536 (2002) 216) ? 3
(this result)

• M(???) spectra
• Combined fit of the two spectra with a0
  production parametrizations
• (convoluted with efficiencies and resolutions)

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• The fit parameters.
• ? Ratio BR(? ????)/BR(? ????????)
• ? BR(??? ????? ????) contribution
• (KL) Kaon-Loop
• (N.Achasov,A.V.Kiselev, Phys.Rev.D73(2006)054029)
  
• ? Ma0, couplings ga0KK ga0??, phase ??
• (NS) Breit-Wigner polynominal
• background
• (G.Isidori et al., JHEP0605 (2006) 049)
• ? Ma0, couplings g?a0? ga0KK ga0?? ?

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Comments 1. Good consistency between sample 1
and 2 the result is experimentally solid
2. KL fit is stable, NS requires to fix
some parameters Results 2.1 ga0KK ? 2
GeV and ga0KK / ga0???? ? 0.8 ?
conflict with qqqq hypothesys (not for
f0(980)) 2.2 Large values of BR(? ? ????)
and of g?a0? sizeable coupling with the ? (as
for f0(980))
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3.3 Search for the decay ? ? KSKS?
In??? ? K0K0? the K0K0 pair is in a J0 state ?
KSKSgtKLKLgt/?2 in a I0,1 isospin state ?
a0 and f0 can contribute Very small allowed
phase space 2MK lt MKK lt M????small
B.R. Predictions on B.R. from 10-13 (no scalar
contribution) up to 10-7

• We have used the decay chain
• ? KSKS?? ? (????)(????)?
• ? 4 tracks1 photon (E?max24 MeV)
• Overall efficiency 20.6
• Very small bckg (ISR ?KSKL)

Result (?Ldt 1.4 fb-1) 1 event found 0
expected background BR(? ? KSKS?)lt1.8?10-8 90
CL
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4. Prospects.
The DAFNE team is testing now a new scheme to
increase luminosity KLOE phase-2 could start
(?2009)
? ? 10 times more statistics ? improved
detector (inner tracker, improved calorimeter
readout, ?? tagger, new small angle
calorimeters) ? enriched physics program
Kaon, ?, ? decays (high statistics) ?? ? ??
(sigma), ?0 2? width deeply bound kaonic states
(AMADEUS proposal)
The possibility to increase the center of mass
energy up to 2.5 GeV is also considered (KLOE
phase-3) ? physics program extended
to hadronic cross-section (g-2, ?em) baryon
time-like form factors (DANTE proposal) ??
physics (?,?,f0(980),a0(980) 2? widths) see
http//www.lnf.infn.it/lnfadmin/direzione/roadmap/
roadmap.html F.Ambrosino et al., Eur.Phys.J.
C50,729 (2007)
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Conclusions Hadron Physics is an important part
of the KLOE program Many results have been
obtained Others are to come full data sample
to be analysed more channels not yet analysed
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SPARES
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