KLOE results on hadron physics

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KLOE results on hadron physics
Hadron07, Frascati 09/10/2007

• Cesare Bini
• Università La Sapienza and INFN Roma
• on behalf of the KLOE collaboration

• 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

KLOE STATUS ? March 2006 end of KLOE data
taking 2500 pb-1 on-peak ? 8 109 f decays
200 pb-1 off-peak (energy scan1 GeV run) ? Dafne
test in progress
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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

• List of the ? decays branching ratios and number
  of events on tape
• B.R. Nev KLOE (2.5 fb-1)
• ????KK- 0.49 3.7 ? 109
• ?K0K0 ??KSKL 0.33 2.5 ? 109
• ???????????? ?0.15 ?1.1 ? 109
• ??? 1.3 ? 10-2 9.7 ? 107
• ???? 1.2 ? 10-3 9.0 ? 106
• ??? 6.2 ? 10-5 4.6 ? 105
• ??????????(f0(980), ?) 3 ? 10-4 2.5 ? 106
• ????? ???(a0(980)) 7 ? 10-5 4.6 ? 105
• ?KK?????(f0(980), a0(980)) ?
  ?
• Initial State Radiation ee- ?????????????????????
  ??????????

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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)
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2. Results on pseudoscalar mesons.
Results presented here 2.1 Precision
measurement of the ? mass 2.2 Improved
measurement of the ? - ? mixing (also f ?
wp0) 2.3 Dynamics of ? ??3? decays 2.4
Measurement of KS ???? 2.5 Preliminary
measurement of B.R.(???????-ee-) 2.6 A flash on
?????0gg
Talks by F.Ambrosino, A.De Santis, B.Di
Micco, R.Versaci (Light Meson Spectroscopy I)
M.Martini (Low energy QCD)
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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 published 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 (dominated by CMD-2)
  

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3? Dalitz plot
? mass peak
KLOE final result M(?) 547.873 0.007
0.031 MeV Systematic error due to - detector
uniformity - Dalitz plot cuts. ?? mass check
M(??) 134.906 ? 0.012 ? 0.048 (compatible at
1.5s with PDG)
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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
R.Escribano, J.Nadal (JHEP 0705,006,2007)
reanalyze all V? P? and P? V? decays updating
wavefunction overlaps parameters and neglecting
the Y1 constraint ? no evidence of gluonium
content
Experimentally improve ?(?), BR(?????),
???????????????????,BR(w?p0g)
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ee- ? wp0 interference pattern between f decay
and continuum fit of cross-section ?s dependence
using 2 decays channels of the w.
Cross-section parametrization
pp-p0p0
gp0p0
Preliminary results BR(f?wp0)(5.630.70)10-5 G(
w?p0g)/G(w?pp-p0)0.09340.0021
Using PDG values for the main decay we get
BR(w?p0g)(8.400.19) (error reduced to 2,
central value shifted 6)
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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 (a) ?? ? ???????Dalitz
plot analysis 1.34 ?106 events (b) ?? ?
???????slope analysis 0.65 ?106 events
(a) ?? ? ??????? Dalitz plot (submitted to
Phys.Lett.B) - large statistics - negligible
background - use X and Y variables
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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.
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Dalitz plot asymmetries ? 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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(b) 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 M(?) value (Dalitz plot
contour)
MC with M(?)547.3
MC with M(?)547.822
New (preliminary) result ? -0.027 ? 0.004
0.004 -0.006 ? 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)
KLOE method ? ? KSKL - KS tagging provided by
KL interacting in the calorimeter - Large
background from KS ? ???? decay (105 times more
frequent)
Red MC signal Blue MC background Pointsdata
BR(KS ? ???)(2.27 ? 0.12(stat) ?
0.05(syst))?10-6 Result compared to other
experiments and theory
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2.5 Preliminary measurement of BR(???????-ee-)

• -Up to now poorly measured (4 events CMD-2, 16
  events CELSIUS-WASA)
• (WASA_at_COSY program)
• BR predicted by ChPT and VMD models (2.6?3.6
  10-4)
• Plane asymmetry
• ? unconventional CP violation
• (D.Gao, Mod.Phys.Lett.A17 (2002) 1583)

KLOE preliminary result based on 622 pb-1 (1/4
of full data sample) Event selection 4 tracks
events 1 photon (363 MeV ) Kinematic Fit p-e
recognition (kinematic and calo PiD (in
progress)) Backgrounds other h decays (mainly
?????????and ??????g with g conversion) charged
kaon decays rp
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Fit of Minv(ppee) with signal background ?
73362 signal events (36 with respect to
previous experiments) Total efficiency
11.7 Systematic uncertainty still under
evaluation
(?) data points signal other h decays other bckg
(mainly K)
In progress asymmetry ? Few level sensitivity
BR(???????-ee-)(2.4 0.2stat 0.4syst) 10-4
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2.6 A flash on ?? ?0??
?ChPT golden mode KLOE has presented a 3?
signal (only 1/5 of full statistics)
CB_at_MAMI-B BR(22.44.61.7) 10-5
4g mass spectrum of selected events (1.5 fb-1
2005 data). Yellow expected bck. Points data
The signal is confirmed in the full data sample.
B.R. updated result with the full sample will
have 15 error
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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
? Motivations 1. f ? ssgt ? scalar quark
composition of f0(980), a0(980) 2. Search for
evidence of ?(500) ? Results presented here
3.1 KLOE results on f0(980)?pp 3.2 High
statistics study of ????? 3.3 Search for the
decay ? ? K0K0?
Mass (GeV/c2)
f(1020)
1
a0(980)
f0(980)
k(800)
s(500)
0
I0
I1/2
I1
Talks by S.Fiore, F.Nguyen (Light Meson
Spectroscopy II)
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3.1 Update of KLOE results on f0(980)
KLOE 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
Large unreducible backgrounds for both
channels wp0 and rp0 for p0p0g ISR, FSR and
rp for pp-g Extraction of the scalar amplitude ?
fit of the spectrum ? parametrization of signal
and background
??????Dalitz plot
f0(980)
??????mass spectrum
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Attempt to describe both spectra with a unique
scalar amplitude. Achasov and Kiselev,
Phys.Rev.D73 (2006) 054029 Scalar amplitude
f0(980) s(600) interference. ? s(600)
parameters and pp/KK scattering phases
fixed (10 different parameter sets, see Eur.
Phys.J. C49 (2006) 433) ? free parameters Mf0,
gf0KK , gf0pp- Preliminary results
(uncertainties under evaluation) are encouraging

• Comments
• 1.The Kaon-Loop well describes the mass spectra
• 2.The f0(980) is strongly coupled to the s quark
  gf0KK gt gf0pp-
• 3.The scalar amplitude has a large low mass tail
  (mlt600 MeV) that can be
• interpreted as due to the ?(600)
• In progress combined fit with improved
  background amplitudes

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

Preliminary results on the branching
ratio 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 spectra with a0 production
  parametrizations
• (convoluted with efficiencies and resolutions)

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• The fit parameters (preliminary).
• ? 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 hypothesis 2.2 Large
values of BR(? ? ????) and of g?a0? sizeable
coupling with the ? (as for f0(980))
Other descriptions ? Unitarized Chiral Model
Palomar et al., Nucl.Phys.A729 (2003) 743 ?
KK molecule Kalashnikova et al.,
Eur.Phys.J.A24 (2005) 437 ? Linear Sigma Model
Bramon et al., Phys.Lett.B494 (2000) 221
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3.3 Search for the decay ? ? KSKS?
In??? ? K0K0? the K0K0 pair is in a J0 state ?
KSKSgt-KLKLgt/?2 in a I0,1 isospin state ?
a0 and f0 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 (preliminary) (?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. (talks by P.Moskal and D.Domenici
(Future facilities))
DAFNE 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)
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/direz
ione/roadmap/roadmap.html F.Ambrosino et al.,
Eur.Phys.J. C50,729 (2007)