1. KLOE C. Di Donato: Fisica di KLOE (40’)
T.Capussela: Dinamica del decadimento h p+p-p0 (15’)
G. Saracino: R&D GEM / TPG (25’)

2. Status report on KLOE physics
Outline:
Published papers
Neutral kaons
Charged kaons
f decays
Hadronic cross section
Conclusions
Camilla Di Donato

3. KLOE integrated luminosity
1999 run: 2.5 pb machine and detector studies
2000 run: 25 pb-1
7.5 x 107 f
published results
2001 run: pb x 108 f
2002 run: pb x 108 f
analysis in progress

4. Published results: 2000 data
Measurement of branching fraction for the decay KS -> pen
(Phys. Lett. B 535 (2002) 37)
BR(KS -> pen ) = (6.91±0.37)x10-4
Study of the decay f -> p0 p0 g with the KLOE detector
(Phys. Lett. B537 (2002) 21)
BR(f -> f0 g ) = (4.47±0.21)x and f0 shape
Study of the decay f -> h p0 g with the KLOE detector
(Phys. Lett. B536 (2002) 209)
BR(f -> a0 g ) = (7.4 ±0.7) x and a0 shape

5. Published results: 2000 data
Measurement of G(KS -> p+p- (g)) / G(KS -> p0 p0)
(Phys. Lett. B 538 (2002) 21-26)
G(KS -> p+p- (g)) / G(KS -> p0 p0)=(2.236   0.015)
Measurement of G(f -> h' g) / G(f -> h g) and the pseudoscalar
mixing angle (Phys. Lett. B 541 (2002) 45-51)
BR(f -> h'g ) = (6.10±0.61±0.43)x10-5

6. KS -> pen Npen BR(KS -> pen) epen = Npp BR(KS -> p+p-) epp KL
The method already used for 2000 data (PLB 535, 37(2002)) has been used to analyze 90 pb-1 out of the 2001 data set p e
boost KS KL
‘Kcrash’ cluster n
Npen
Npp =
BR(KS -> pen)
BR(KS -> p+p-)
epen
epp x
Events tagged by a ‘Kcrash’ cluster
2 tracks and 1 vertex close to the IP
Reject events with invariant mass Mpp close to the K0 mass
Use time information from calorimeter clusters to perform PID for charged
tracks

7. p/e identification AS,L = e-p+ dt(me1)-dt(mp2) dt(me2)-dt(mp1) 6 ns
Time of flight e/p identification (Dt = 2 ns) :
dt(m) = tcluster – t.o.f. calculated with mass hypothesis m
Sign of the charge is determined
-> semileptonic asymmetry accessible
AS,L =
G+S,L - G-S,L
G+S,L + G-S,L
e-p+
dt(me1)-dt(mp2)
dt(me2)-dt(mp1)
6 ns
e+p-

8. Charge identified yields
N(p-e+n) = 1450±70
N(p+e-n) = 1520± 70
Emiss=ES-Ee- Ep
Preliminary result on the asimmetry has an
overall error of 3% and is consistent with 0.
We expect 1% error with full 500 pb-1 data set
ES,PS from KL direction and f momentum
Pmiss= |PS-p1-p2|
Charge independent fit compatible with the sum: N(pen)=2950±120

9. BR(KL->gg)/BR(KL->3p0)
Motivations:
 Long distance contribution to the rare KL  m+m- decay
 Relative uncertainty on BR(KL  p0p0p0 )  1.3%
Common preselection, essentially:
KLtag
Neutral vertex
Fiducial volume
gg preselection, essentially:
Eg> 100 MeV
Photons angular separation in the plane transverse to KL momentum > 150o

10. KL->gg selection
Two discriminating variables exploiting the fixed kinematics in KL center of mass system: E*
Mgg after E* cut
Mgg after a cut
Mggafter preselection a

11. KL->3p0 selection 2001+2002 data ‘01 data
The three pions sample is trivially selected with minimal requirements on photon energies. To limit systematics due to photon splitting/merging inclusive selection is done with Ng3
data
( ) pb-1
KLOE: tL = 51.6 ± 0.8 ns
PDG: tL = ± 0.4 ns
‘01 data
KLOE preliminary: R = (2.80 ± 0.03stat ± 0.03 syst)10-3
NA48 (2002): R = (2.81 ± 0.01stat ± 0.02 syst)10-3
Data quality and stability with different data taking conditions is very good

12. A first glance at interference
Neutral kaons produced in a pure
quantum state (JPC = 1- - ) :
Time evolution for p+p-p+p- :
L ~ 280 pb-1
No simultaneous events:
same final state + antisymmetric initial state
|Dt|/ts
Peak position sensitive to Dm value
KL regeneration on the pipe

13. Charged kaons Improved energy loss treatment in track fit
Many improvements have been introduced for charged kaons in the reconstruction – classification – analysis chain, in order to cope with the peculiar features of these events at KLOE:
Improved energy loss treatment in track fit
Refined treatment of multiple scattering correlation matrix
Improved merging of split kaon tracks
Realistic drift chamber noise simulation from data
T0 global finding
Kaon time of flight corrections
Single arm tagging method in event classification

14. sf measurement with K±
Good statistical power few % accuracy with 1 pb-1
Exploits the K0 TAG
K counting  insensitive to Kaon BR’s and reconstruction efficiencies  + K K+
N2 = number of ev with 2 triggering pp0 tags
N2 = Nkk eand (id BRK )2
N1 = 2 Nkk BRK id [eor (1- BRK) + BRK eand (1- id)] K+ +
N1 = number of ev with 1 triggering pp0 tag
The number of K+K- events Nkk is function of N1, N2 and geometrical acceptances (eor ,eand ), but not of the Tag efficiency (id ) !!

15. sf measurement with K± (2)
To count N1 and N2 look at the pion
Momentum in the kaon rest frame p* MC
Before tagging
m peak
p peak
Or Tagged
AND tagged
Kl3 background
Shapes for the pion (muon)
peak are obtained from data in
K±->m±n tagged events.

16. Preliminary results 2002 (7.0 pb-1): (1713±32stat±34lumi) nb (e=10.2%)
Analysis procedure used to extract the cross section e+eK+K- at the peak on a subsample of 2002 data set:
2002 (7.0 pb-1): (1713±32stat±34lumi) nb (e=10.2%)
W dependence for the 2002 scan (± 2 MeV)
Together with the other channels will allow the extraction of all f parameters.

17. f->p+p-p0 dynamics Fit function The two main terms are :
Y=(E0– M0) X=(E+ - E- )/3
Fit function
The two main terms are :

18. f->p+p-p0 dynamics ad = 0.093  0.011  0.015
The (not quite) preliminary results, on 20 pb-1 (2000 data) are:
ad =   0.015
fd =  0.09  0.11 rad
M(r0) =  0.57  0.67 MeV
DM0+ =  0.34  0.68 MeV
DM+- =  0.39  0.67 MeV
Gr =  1.2  1.0 MeV
c2/dof = 1947(1874-8)

19. f-> hp0g update Same selection as of 2000 Event number scales with
luminosity
5g final state
2001 data (140 pb-1)
2000 data
Events
p+p-5g final state
Events
M (MeV)
M (MeV)

20. f-> p0p0g update Same selection as of 2000 5g final state Events
Event number scales with
luminosity
5g final state
M (MeV)
Events
2001 data
2000 data

21. f0 -> p+p-
data
With the (almost) complete statistics of we finally found evidence for the
f0 -> p+p- decay
The amount of events in the f0 peak is already indicative of a destructive interference with FSR
Preliminary
980
Mpp (MeV)

22. f->h(h,)g->p+p-ggg update
100 pb-1 (2001)
hg bands
Sidebands for bkg shape evaluation
700 evts in the peak
hg region

23. h-h, ratio
The selected number of hg events scales with luminosity within errors as expected. Events are very clean with background <1%
300 kevents
Year 2000 (16.3 pb-1):
Nh’g/Nhg = (2.4 ± 0.24 stat ± 0.1 bkg )·10-3
Year 2001 (preliminary) (100 pb-1):
Nh’g/Nhg = (2.2 ± 0.09 stat ± 0.05 bkg )·10-3

24. f->h,g->p+p-7g 2000: 16 pb-1 2001: 118pb-1 2002: 223pb-1 c2/Ndgf
Ep++Ep-
2000:
16 pb-1
2001:
118pb-1
2002:
223pb-1

25. h->ggg KLOE preliminary 142 pb-1 BR(hggg) < 3.5  10-5
KLOE can improve the current PDG limit for this C violating decay
Mggg (MeV)
Mggg (MeV)
142 pb-1
BR(hggg) < 3.5  10-5
KLOE preliminary

26. Hadronic cross section and am
Davier, Eidelman, Höcker, Zhang: hep-ph/
1.6 s
3.0 s
hep-ex/
Disagreement between e+e- based
and t based evaluations
FJ 02 (e+e- based)
2.8 s
PRELIMINARY
Experiment and Theory with
almost identical errors ( ± 8·10-10 ):

27. Radiative Return
We measure the cross-section s(e+ e-  hadrons ) as function of the hadronic c.m.s energy M 2hadrons by using the radiative return
ds(e+ e-  hadrons + g )
dMhadrons
disadvantage advantage
Requires precise calculations of ISR Data comes as by-product of standard program
 EVA + Phokhara MC Generator
Requires good suppression (or knowledge) Systematic errors from Luminosity, s, … enter only once
of FSR

28. Pion tracks are measured at angles
Signal selection
Two fiducial volumes are currently studied:
550< q < 1250
q < 150
q > 1650 p
Pion tracks are measured at angles
40o< p <140o
large angle: 55o<<125o
Allows a tagging of the radiative photon
small angle:  < 15o and  > 165o
Photon cannot be detected efficiently with EmC, untagged measurement in which we cut on the missing momentum pp
The two kinematical regions differ for:
ppg cross section (SA: 24 nb; LA: 3 nb)
M2pp spectrum shape
background contamination
relative contribution of FSR

29. Small angle analysis Performed on 73 pb-1 of 2001 data set
Mpp2(GeV)
Ni/0.01GeV2
Performed on 73 pb-1 of 2001 data set
after selection: about 106 events
statistical error/bin < 1%
for M2>0.45 GeV2
30000
20000
10000
Signal
Background
Luminosity
Selection efficiency

30. Preliminary results MC DATA
DATA is compared with the MC generator PHOKHARA (NLO) whose output is expected to be accurate at 0.5% level and
has been interfaced with the detector simulation program (GEANFI).
MC events are generated with the SA fiducial volume cuts:
d/dM2(nb/GeV2) MC
DATA
M2pp (GeV2)
qg<15o (qg>165o), 40o<qp<140o

31. Pion form factor (prelim.):
Data points have been fitted with the
Gounaris-Sakurai-Parametrization
|Fp|2
=CMD2
=KLOE
M2p+ p- (GeV2)
KLOE
PRELIMINARY
(G.J. Gounaris and J.J. Sakurai, Phys.Rev. Lett. 21 (1968), 244)
mr, Gr ,  ,  are free parameters
of the fit, while mw Gw mr Gr are
fixed to CMD-2 values
Mr = MeV
Gr = MeV
 =(-0.08) •10-3
 = 2.893•10-3
124.80
(Stat. Errors only)

32. pp(g): conclusions & outlook
Experimental and Theoretical groups are in close contact to improve the measurement and to allow an interpretation for the evaluation of the hadronic contribution to am.
Work is in progress in order to refine the analysis with all the statistics of 2001 (~170 pb-1 )
Short term goal: a paper in beginning 2003 with:
a measurement of ds(e+e-->p+ p-g)/dM2pp for SA cuts
based on full 2001 statistics with a precision of 2 %
a derivation of s(e+e-->p+ p-) obtained by dividing
ds(e+e-->p+ p-g)/dM2pp for the radiation function
a fit of the pion form factor

33. Conclusions
The increased performances of DAFNE are giving us the chance to investigate deeper and deeper the unique KLOE physics program.
All previously performed analyses are obtaining significantly improved results, and many new ones are coming to a definitively sound status. Precision measurements are on arrival also for relatively rare processes…
…we are ready for the fb-1 era…!

34. Background p+ p- p0 p+ p- g m+ m- g
Trackmass
M2pp
The signal is further selected by performing a cut in the so called trackmass variable in order to reduce p+ p- p0 background
p+ p- p0
This background contamination
is more significant at
small M2pp values and affects mainly the LA region
p+ p- g
m+ m- g background
(Mtrack104 MeV)
rejected by a cut on Mtrack =120 MeV
m+ m- g
Remaining contamination estimated from MC:below 1% for SA region

35. Charge asymmetry AS = N+/e+ - N-/e- N+/e+ + N-/e-
To get the asymmetry, one has to correct the e+p- and e-p+ event yields using the charge dependent efficiencies…
N+/e N-/e-
AS =
N+/e N-/e-
Efficiencies are determined on data using several control samples and currently read:
e(p+e-) = (21.7 ± 0.5)%
e(p-e+) = (21.0 ± 0.5)%
Quoted errors depend mainly on the statistics of the KL->pen control sample and determine the overall systematic uncertainty (2%)
Preliminary result on the asimmetry has an overall error of 3% and is consistent with 0. We expect 1% error with full 500 pb-1 data set.

36. KS pen : motivations AL -AS =4Rd =0
In the S.M., in a completely independent way from hadronic matrix elements and related uncertainties one has:
(DS=DQ)
(CPT)
AS,L =
G+S,L - G-S,L
G+S,L + G-S,L
AL -AS =4Rd =0
with
Currently:
Rx = (-1.8 ± 6.1)· from CPLEAR (1998)
With 2 fb-1 KLOE can improve the accuracy by a factor ten
AS not yet measured. Need 20 fb-1 to measure with 30% accuracy