1. Hadronic results from KLOE
European Physical Society
International Europhysics Conference on High Energy Physics
EPS (July 17th-23rd 2003) in Aachen, Germany
Hadronic results from KLOE
E. Santovetti (INFN – Roma II)
for the KLOE Collaboration

2. DAFNE: the Frascati F factory
electron positron collider at the f mass energy (ECM= 1020 MeV)
separate rings to minimize beam-beam interaction
two interaction points (KLOE – DEAR/FINUDA)
Machine parameters
Design
2002
Total length (m) 98
Max. bunches
120 51
Bunch spacing (ns)
2.7
5.4
Lifetime (min) 40
Bunch current (mA) 20
L single bunch (cm-2 s-1)
L peak (cm-2 s-1)
f per year (109) 15
0.9
E. Santovetti
HEP2003 Aachen, July 2003

3. KLOE data taking history
Year
pb-1/day
average
peak
2000
25 pb-1
0.1
0.4
First published results
2001
170 pb-1
0.7
1.8
Luminosity improved but high background
Further analyses published
2002
280 pb-1
2.0
4.5
Higher luminosity and background reduced
Analysis in progress
in 2002
An upgrade of the machine has been done.
An increase in luminosity ( > x2 )
is expected in the next data taking.
E. Santovetti
HEP2003 Aachen, July 2003

4. Kaon physics at DAFNE
The kaons are produced in pairs (K+ K- and KS KL ) with opposite momentum.
The detection of a kaon on one side can be used to tag the other kaon in the opposite side
Measure of absolute branching ratios
Interferometry studies on KS KL system
F decay %
#/pb-1
K+ K-
49.2
1.5x106
KS KL
33.7
106
r p / p+ p- p0
15.5
5x105
h g
1.3
4x104
p (MeV/c)
l (cm)
K+ K-
127 95 KS
110
0.6 KL
343 f e- e+ KL KS
all KS decay close to the IP
reasonable acceptance for KL
E. Santovetti
HEP2003 Aachen, July 2003

5. The KLOE detector Electromagnetic calorimeter
lead/scintillating fibers structure
15 X0 thickness
4880 PMT's
Drift chamber (4m Ø x 3.3m)
90% He – 10% IsoB mixture (X0 ~ 500m)
12582/52140 sense/total wires
stereo geometry for z measurement
Quadrupole calorimeter
lead/sc. tiles calorimeter surrounding the permanent quadrupoles (32 PMT's)
Superconducting coil (5m Ø)
B = 0.52 T
E. Santovetti
HEP2003 Aachen, July 2003

6. Detector performances
calorimeter
Drift chamber
High efficiency for low energy photons
E. Santovetti
HEP2003 Aachen, July 2003

7. KLOE physics program 500 pb-1 now on tape 2 fb–1 2002 200 pb–1 20 pb–1
Discrete symmetries
Re(e/e) via double ratio (CP direct)
KLKS Semileptonic asymmetry (CPT)
KLKS interferometry
2 pb–1
20 pb–1
200 pb–1
2 fb–1
2002
KS  gg , KS  3p, KS  ppg
KL  2p, KL  gg
Vus from K± and KL decays
K± branching ratios
s(e+e–  p+p–) to 1%
2000
f radiative decays
f  f0g , a0g scalar
f  h’g , hg pseudoscalar
KS decays
BR(KS  p+p–)/BR(KS  p0p0)
BR(KS  pen)
first published results
1999
500 pb-1 now on tape
E. Santovetti
HEP2003 Aachen, July 2003

8. (Mass is calibrated with the CMD-2 value)
f mass and width
+ corrections
(phase space + contributions from w r )
f line shape has been fitted for the main f decays
K+K–
KSKL rp hg
In the case of  a fit with several points has been used to find the correct line shape form (interference between direct,  and w)
K+K– %
KLKS %
 %
 %
f parameters:
mass, total width, peak cross sections
With a combined fit, we measure the f width: Gf=4.19±0.04 MeV (preliminary)
(Mass is calibrated with the CMD-2 value)
W(MeV)
E. Santovetti
HEP2003 Aachen, July 2003

9. Neutral kaon mass W (MeV)
KLOE can study masses of particles with high accuracy thanks to excellent drift chamber momentum resolution
Neutral kaon mass can be measured using KSgp+p-
Energy scale from CMD-2 f mass value
fgKSKL
KSgp+p-
s(e+e- g KSKL) (mb)
MKs= ±0.005stat±0.020syst MeV*
PDG: ±0.022 MeV
*KLOE Note 181 (
2001
Energy scan
W (MeV)
E. Santovetti
HEP2003 Aachen, July 2003

10. KS/KL tagging
KS is tagged by identification of KL in the calorimeter (KL crash): a neutral cluster in a fixed time window
efficiency ~ 30% ( largely geometrical)
angular resolution on tagged KS ~ 1°
momentum resolution ~ 2 MeV
KL is tagged by identification of the
KS g p+ p- decay: a vertex near the interaction point with the kaon inv. mass
efficiency ~ 70%
angular resolution on tagged KL ~ 1°
momentum resolution ~ 2 MeV
E. Santovetti
HEP2003 Aachen, July 2003

11. G(KSgp+p-(g))/G(KSgp0p0)
Can be used to extract d0-d2 phase shifts and Kgpp amplitudes
Provides information on isospin symmetry breaking from EM terms Chiral pert. theory
First part of the double ratio
From the K g pp decays (KS, K+),
in the exact isospin symmetry hypothesis, we have:
considering the EM correction:
Kgpp decays measure c0-c2
To extract d0-d2, we need a theoretical
input dEM.
Important to know the effective
Eg cutoff in p+ p- g decay
E. Santovetti
HEP2003 Aachen, July 2003

12. G(KSgp+p-(g))/G(KSgp0p0)
at least 3 neutral clusters in time
Ecl> 20 MeV, |cosq| < 0.9
to reduce machine Bkg
Efficiency ~ 90%
KSgp+p-
2 tracks from IP extrapolated to the EmC (120 MeV <pTRK < 300 MeV) Efficiency ~ 60%
MC 
MC 
The measurement is fully inclusive in the radiated photon energy (no cut in the p+p- invariant mass)
Efficiency is corrected for the radiated photon in the final state by folding the MC distribution (linear interpolation) with the photon spectrum theoretically predicted
0.3% effect
E. Santovetti
HEP2003 Aachen, July 2003

13. G(KSgp+p-(g))/G(KSgp0p0)
KLOE '02
2.236   0.015
17 pb data
PDG ’02
2.197  0.026
World average
Physics Letters B538 (2002)
KLOE ‘02
c0-c2
d0-d2
KLOE
G(KSgp+p-(g))/G(KSgp0p0)
47.8±2.8
47.7±1.5**
PDG '02
56.7±8.0*
*Cirigliano et al. (2000)
**G. Colangelo et al. (2001)
E. Santovetti
HEP2003 Aachen, July 2003

14. KSgp-e+n, p+e-n
Together with the KLgpen, can be used to strictly test CPT and the DS=DQ
Provides information about Vus
Cut on time of flight:
The mass hypothesis m=me and m=mp on both tracks allows to discriminate a large part of background
Difficoult to isolate Ksgpen respect to the more abundant (x1000) Ksgpp
best measurement CMD-2: BR(Ksgpen) = (7.2 ± 1.4) x (75 events)
E. Santovetti
HEP2003 Aachen, July 2003

15. KSgp-e+n, p+e-n Use of variable Emiss-cpmiss
For pen decays this is the neutrino mass, while for the p+p- decays a value larger than zero is expected.
A fit of the data to the sum of the signal and background spectra simulated by MonteCarlo allows to extract the number of events. 6 7
8 ×10-4
CMD-2 ’99
PDG eval. from KL
KLOE ’02* (17 pb data)
KLOE ’03 preliminary
*Physics Letters B535 (2002)
KLOE preliminary (170 pb-1 '01 data)
BR(p-e+n)
3.46 ± 0.09stat ± 0.06syst
BR(p+e-n)
3.33 ± 0.08stat ± 0.05syst
BR(pen)
6.81 ± 0.12stat ± 0.10syst
E. Santovetti
HEP2003 Aachen, July 2003

16. K0gpen, CPT and DS=DQ AS = (19 ± 17stat ± 6syst) x 10-3
CPT: b = d = 0
AS = AL if CPT conserved
KLOE preliminary
AS = (19 ± 17stat ± 6syst) x 10-3
First measurment of AS ! AL
PDG '02
(3.33 ± 0.14) x 10-3
KTeV '02
(3.322 ± ± 0.047) x 10-3
DSDQ transitions are forbidden at lowest order in the SM
DS=DQ: c = d = Re(x) = 0
Re(x) (x 10-3)
KLOE preliminary
3.3 ± 5.2 ± 3.5
CPLEAR '98
-1.8 ± 4.1 ± 4.5
E. Santovetti
HEP2003 Aachen, July 2003

17. G(KLggg)/G(KLgp0p0p0)
Provide information about the absortive contribution (Aabs) to the KLgmm decay (long-distance term) – Prediction on Ksggg
Very sensitive to the calorimeter performance in reconstructing the neutral vertex
very clean signals: low background (KLgp0p0)
KLgp0p0p0
inclusive measure: at least four neutral clusters in time with Eg > 20 MeV
Efficiency > 99%
Background ~ 0.4% (KLgp0p0)
KLggg
Close kynematics: cuts on
- E*tot, Collinearity, Invariant mass
Efficiency ~ 80%
Background negligible
gg invariant mass plot after the cut on collinearity and total energy
362 pb-1 of data analysed
('01+'02 data)
Preliminary
1/10 of 362 pb-1
tL (ns)
51.7 ± 0.4
PDG '02
51.5 ± 0.4
KLOE
KLgp0p0p0
G(KLggg)/G(KLgp0p0p0) (x10-3)
KLOE '03*
2.793 ± 0.022stat ± 0.024syst
NA48 '02
2.81 ± 0.01stat ± 0.02syst
PDG '02
2.82 ± 0.08
*Physics Letters B? (2003)
E. Santovetti
HEP2003 Aachen, July 2003

18. Pmiss - Emiss in pm or mp hyp. (MeV)
KLg charged (very preliminary)
KLOE*
PDG ‘02
KLgp+p-p0
0.1320.002
0.12570.0019
KLgpmn
0.2710.002
0.27170.0025
KLgpen
0.3840.002
0.38780.0027
KLgp+p-
(2.020.19)·10-3
(2.0810.026)·10-3
Pmiss - Emiss in pm or mp hyp. (MeV)
pen
pmn
p+p-p0
p+p-
*Errors are statistical only!
(including MC statistics)
Systematic errors also ~1-2%
but not yet fully evaluated
Very preliminary
78 pb-1 ’02 data
E. Santovetti
HEP2003 Aachen, July 2003

19. K±gpp0p0 (t')  + K+ – K– 0
Direct CP violation in the charge asimmetry (from theory 10-6 ÷ 10-4)
Dalitz plot parameters (CP)
Extract isospin amplitudes and phase shifts for Kgppp decay (cPT)
(t') best value (PDG '02) has ~2% error and concerns only K+ 0 – K– K+ + 
Selection
mn/pp0 – tagging and self-triggering
2-tracks vtx in DC volume
p* < 135 MeV/c
4 clusters vtx (Dt<4s)
Etot < 450 MeV
Background: main K± decays, Ke4’
Efficiencies evaluated from data by using control samples
(ex. ecl from K±gpp0)
E. Santovetti
HEP2003 Aachen, July 2003

20. K±gpp0p0 (t') BR(K±±00) (%) KLOE '03* 1.781±0.013stat±0.016syst
PDG '02
1.73±0.04
*KLOE Note 187
187 pb-1 event counting (~80000 ev.)
250 pb-1 efficiency estimate
Preliminary Dalitz plot analysis:
F(X,Y) = 1+gY+hY2+kX2
si=( PK–Pi )2
s0=isi/3 ;
X=(s1–s2)/m2
Y=(s3–s0)/m2
KLOE* (6.3 pb-1)
PDG '02 g
0.586±0.010 ±0.012
0.652±0.031 h
0.030±0.010 ±0.013
0.057±0.018 k
0.0055± ±0.0018
0.0197±0.0054
Charge asimmetry analysis in progress
E. Santovetti
HEP2003 Aachen, July 2003

21. Experimental inputs to Vus from PDG 02
Vus determination
Introduced in 1963, known to 1.5%
|Vus| = ± exp ± th
KLOE preliminary BR’s confirm previous values for K0e3, K0m3
KLOE will have BR(K+e3) soon
KLOE will measure all BR’s to < 1% and can also significantly improve l+, l0, tL
preliminary
E865
For Ke3 modes:
exp th
Experimental inputs to Vus from PDG 02
Mode
BR(%)
103 l+
103 l0
K+e3
4.87 ± 0.06
28.5 ± 2.1
K0e3
38.79 ± 0.27
29.1 ± 1.8
K+m3
3.27 ± 0.06
3.3 ± 1.0
4 ± 9
K0m3
27.18 ± 0.25
3.3 ± 0.5
27 ± 6
tL = (5.17 ± 0.04) · 10-8 s
tS = ( ± ) · s
t+ = ( ± ) · 10-8 s
E. Santovetti
HEP2003 Aachen, July 2003

22. f grp,p+p-p0
DaFne produces 5·105 p+p-p0 events/pb-1 ,allowing a detailed study of the decay dominated by the rp intermediate state: r mass measurement (CPT)
Selection
2 charged tracks with vtx at I.P.
|Mmiss– Mp° | < 20 MeV (p0 mass)
2 photons (cos q*gg < –0.98) (collinearity)
c2 = (Etot- Mf )2/sE2 + (Mgg-Mp°)2/sM2 < 8
Efficiency ~ 30% - Negligible background
Fit of the Dalitz plot considering a direct decay together with rp (dominant) and wp intermediate staes:
Arp : 3 terms : Mr+, Mr–, Mr0 and Gr (Gounaris Sakurai shape)
Awp : standard Breit Wigner
Adir: constant  ad eifd : |ad|2 =  |Adir|2 /  |Arp|2
E. Santovetti
HEP2003 Aachen, July 2003

23. f grp,p+p-p0 X=(E+– E–)/3 Y=(E°– M°)
2×106 events analyzed (16 pb–1 – 2000 data)
Very different values
depending on the used techniques:
e+e-, t decay, hadronproduction
KLOE* (6.3 pb-1)
PDG '02
Mr (MeV)
775.8  0.5  0.3
771.1  0.9
Gr (MeV)
143.9  1.3  1.1
149.2  0.7
m0-m± (MeV)
0.4  0.7  0.6
0.4 ±0.8
m+-m- (MeV)
1.5  0.8  0.7 ad
0.78  0.09  0.13 aw
(7.1  0.6  0.8)×10–3
X=(E+– E–)/3
Y=(E°– M°)
*Physics Letters B561 (2003)
Relative decay intensities from integration of |A|2 over Dalitz plot
Irp = 0.937
Idir =
Iwp =
Irp + Idir + Iwp  1 (+6%)
Interference between
rp and direct decays
E. Santovetti
HEP2003 Aachen, July 2003

24. Conclusions and outlook
DANE luminosity has been continuously improving.
KLOE expects to collect at least 1 fb-1 in 2003/2004
Analysis of data brought to several published results on neutral kaons and  decays
Work in progress with 2001/2002 data:
- K , KL semileptonic decays (Vus)
– Rare kaons decays: KS  p+p- g, KS  3p0, KS  p+p- e+e, KS  gg
–  decays (about 2×107  produced in 500 pb-1)
E. Santovetti
HEP2003 Aachen, July 2003