1. KLOE Status Report Open Session of the LNF Scientific Committee
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

2. Outline Studies on KS KL Data Quality Detector Status and Calibrations
Results from the 1999 Data taking
Radiative Phi Decays
Studies on KS KL
The 2000 Data Taking
Luminosity and Background
Data Quality
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

3. The KLOE Detector Large Detector: 7m Diameter, 6 m Length
Large Superconducting Coil : B=0.6 Tesla
Lead Scintillating Fiber EMC: (4880 Channels)
Large Helium Drift Chamber: (12582 Sense Wires)
Two Quadrupole Calorimeters
Spherical berillium beam pipe (radius > 10 ls )
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

4. Calorimeter Energy calibration
Absolute scale set using gg and Bhabha events
All cells are equalized with MIPs (needed for triggering)
F  p+ p  p 0 events give a p0 mass of 134 MeV (s = 16 MeV), uniform all over the calorimeter!
h  gg
events give a h mass of 546 MeV
(s = 42 MeV)
Non-linearity ~1%
e+e- e+e-g Eg from DC
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

5. Calorimeter Time calibration
Energy (Mev)
Time resolution vs E
Absolute Time Scale:
New method to extract both the Global T0
and the Interbunch Time using the DFT
Precision on IT ~ 3 ps and
on T0G ~ 10 ps (10 nb-1 each)
old
new {
Bunch structure
Intercalibration term
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

6. Calibration Monitoring & Stability
July-August Run
Energy variations (~2%)
measured and corrected every 100 nb-1
E (A.U.)
Run #
T0 global variations up to
ps corrected run by run.
IT stable during runs
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

7. Calorimeter Performances
Mass reconstruction of fully neutral final states
Ks 0 0
Mk= 494 MeV k = 27 MeV
Calorimeter efficiency vs energy ( MeV)
measured using rad Bhabha
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

8. Calorimeter M.B. On End Cap very hot regions close to beam pipe.
Counting rate on the hot regions
during 2000 run
This machine background induces on average ~ 8% of accidental neutral clusters on good events (0.2% of wrong T0G)
On End Cap very hot regions close to beam pipe.
Single rate 100 KHz.
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

9. Drift Chamber Hardware Status
To cope with the high M.B. we
introduced 5000 ppm of water
vapour in the chamber gas.
Moreover we decreased the HV on the four inner layer by 50 V.
RS232
Cooler/Heater
Temperature
feedback
Level control
Water bubbler
Water vapor subsystem
Refilling
volume
Overpressure
compensation
He in
Flow meter
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

10. Drift Chamber Calibration
residuals
DC CALIB GO
STOP
EmC recon
selective filter
raw
DC tracking 8%
100% = 400 Hz
selcos raw
32 Hz
HepDB
DC CHECK OK
DC CHECK
starts automatically every
run
integrates 300K cosmics
(3 hr)
histograms track-hit
residuals
40 mm residual tolerance
DC CALIB
reconstructs selected
events using residuals
(45 evt/sec, ~2hr)
fits s -t relations
stores new calibrations in
DB along with DC conditions
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

11. Drift Chamber calibration II
Sept-Oct Run
STRs are calibrated at the level of
20 µm for the residuals
T0 Stability:
For stable hardware conditions the T0 are reproducible at the level of 0.5 ns
Check of the online calibration and of the STRs Stability.
With 40 µm tolerance on residuals no need for frequent calibrations.
Water vapour effect on STR
1st Iter
2nd iter
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

12. Drift Chamber Performances
Bhabha
KS  p+p-
sp /p < 0.3%
45° < q < 135°
Polar angle
sp (MeV/c)
sM ~ 1 MeV/c2
KL  p+p- p0
M(p0) = MeV
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

13. Drift Chamber Accidentals
Positron Injection
Charge integrated in July: Q  1 mC/cm/month
Wire ageing:
Q = mC/cm, no effect
literature: QMAX = mC/cm
Rate on inner layer
~ 20 KHz.
Single counting rate measured from the number of hit in a time window of 200 ns out
of the drift time signal region.
Rate on the first 3 layers as a function of run time:
the rate follows the decrease of the beam currents.
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

14. The Trigger Logic
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

15. EMC Trigger efficiency
Events are triggered requiring 2 calorimeter sectors fired.
KL Inter. in EMC fires at least 1 sector
etrig(KCR,KSpp) = 1 - PKCR(1) • PKS(0)
PKCR(1) measured to be = 54.7  0.3 %
PKS (0) measured to be = 0.21  0.03 % ( p0p0 )
Effect of c.r. veto evaluated by downscaled events
etrig =  0.02% ( p0p0 )
etrig =  0.04% ( p+p- )
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

16. Slow Control
DCH counting rate
Beam pos.
DCH currents
Luminosity
Calo Accidentals
Informations on the luminosity and background are made available to DAFNE via WWW
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

17. DAQ Status
DAQ System stable since long time : Acquisition Rates up to 10 KHz aquired without problems
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

18. 1999 Physics Run
Apr 14-May10: data taking in single bunch mode.
F line shape scan (3 nb-1)
Ldt = 2.4 pb-1
From July 30th to December 19th:
 Recorded:
7.7106 F
 Reconstructed:
1.1106 Ks  p+p -
14106 Bhabha q > 200
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

19. f  f0 g  p + p - g r Backgrounds: e+ e-  p+ p- g ( ISR )
e+ e-  p+ p- g ( FSR )
Interference ( +, - ) ?
Sample contaminated by radiative Bhabhas
Signal
Region r
Analysis:
Likelihood - Method for
p/e - separation
(95% p-acceptance; 94% e-rejection)
Q + - > 45° (Bhabha suppression)
Q g > 45° ( ISR suppression )
Mpp2 - spectrum from threshold to
0.84 GeV2 under the assumption of
pure ISR / FSR
Extrapolate to signal region
> GeV2
Result: 35 ± 166 Events
BR( f  f0g  p+p-g ) < 1.6 ·10-4
@ 95% C.L.
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

20. f  f0 g  p 0 p 0 g 5 Prompt g’s + Kinematic fit Main background:
Great interest for light meson spectroscopy because of controversial nature of a0 and f0 !
5 Prompt g’s + Kinematic fit
Main background:
e+e-  wp0, w  p0g
Rejection requires:
cut on cos() (angle between p0 and g
in the dipion rest frame) p0 g
cosy
Nev sel = with M(p0 p0)> 700 MeV/c2
KLOE preliminary:
BR(f  p0p0g f0Region)=
( )10-4
[vs BR=( )10-4 (SND-2)
and BR=( )10-4 (CMD-2)]
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

21. f  a0 g   p 0 g  5 g Backgrounds: f  r p0   p0 g ( S/B = 7 )
e+ e-  w p0   p0 g ( S/B = 20 )
f  p0 p0 g ( S/B = 0.1 )
f   g  p0 p0 g
Analysis:
2 step kinematic fit (w. and w/o
mass constraint)
Best photon pairing in all
relevant hypothesis
kinematical cuts in -p0 rest frame
Result: Nobs=74, Nbkg=21 Events
BR(f  p0g)=(0.77±0.15±0.11)·10-4
[vs BR=( )10-4 (SND-2)
and BR=( )10-4 (CMD-2)]
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

22. f  hg , f  p0g fit. (1.297+0.033)  10-2 p0g band hg band
After bkg subtraction we obtain:
Nhg= (stat) + 167(syst)
Np0g = (stat) (syst)
For 3gs events we study the correlations between cosqgg and DEgg (non radiative g). The bkg is uniform in the side bands.
BR ( f hg ) =
( (Syst)+0.06(Lum))10-2
fit. ( )  10-2
PDG 2000
Aver.( )  10-2
SND ( )10-2
CMD ( )  10-2
hg band
p0g band
BR ( f  p0g ) =
( (Syst) +0.06(Lum))10-3
fit. ( )  10-2
PDG 2000
Aver.( )  10-2
SND ( )10-2
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

23. f  h'g F  h'g, h' hp+p-, h gg F  h'g, h' hp0p0, h gg
Nev sel =
Great interest since gluonic content of h’
and mixing angle h-h’ still controversial
A vertex with two tracks (p+p-)
near the origin + 3 prompt g’s
F  h'g, h' hp0p0, h gg
First observation !
7 prompt g’s
Nev sel=6
+3.3
-2.2
KLOE preliminary:
RF=BR (Fh’g )/ BR (Fhg )= ( )10-3 (charged)
( )10-3 (fully neutral)
BR (Fh’g)= ( )10-5
-0.6
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

24. f  p+p-p0 2.14 pb-1  330K events 3 contributions to Dalitz plot:
f  r ,0p 0, 
f  p+p-p0 (direct)
e+e-  wp0
E0 – mp0 GeV
(E+ - E-)/3 GeV
First observation
 10%
Amplitudes of rp and direct
terms not well established
Analysis of Dalitz plot sensitive
to r line shape
Measure r,0p0, simultaneously
f(X,Y)=|p+p-|2•|A+ Adirect+A|2
No isospin breaking observed
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

25. Radiative f summary and prospects
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

26. KS,KL Studies: Tagging strategies
Observation of KL(KS) tags the presence
of the recoiling KS(KL)
A Kl is tagged by KS  p+p-
(KLTAG) with etag ~ 50%
A Kl is tagged by KS  p0p0
(KSNEUT) with etag ~ 20%
A KS is tagged by Kl  p+p- p0
or Kl  pln with etag ~ 30%
A KS is tagged by Kl interacting
in the calorimeter (KLCRASH)
with etag ~ 30%
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

27. Measuring BR(KS  p+p-)/BR(KS  p0p0)
Select events using the KLCrash Tag
Look for a cluster with:  And a cluster with:
 Ecl  50 MeV  Ecl  100 MeV
 |cos(qcl)|  0.7
 RT  60 cm  b* = [0.195,0.245]
t0 evaluation }
Diff. on b for p0p0
and p+p- events
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

28. KS decay type selection
KS  p0p0 decays
KS  p+p- decays
Look for two tracks with:
dminxy  10 cm
rfirst  35 cm, zfirst  40 cm
| cos(q)|  0.9
pmax = max(P1, P2)  130 MeV/c
ptot = | PKl+ P1+ P2 |  65 MeV/c
Look for clusters with:
dt = | tcl - Rcl/c |  5 s(Ecl)
| cos(qcl)|  0.9
Ncl  4
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

29. Efficiency determination
T0 efficiencies
Tagging:
KLCrash Tagging efficiencies is different for neutral and charged decays: ratio of tagging efficiencies determined directly by data*
atag =  0.003
Cluster efficiencies
Decay selection:
Dominated by tracking efficiency ( p+p- ) and clustering efficiency ( p0p0 ) determined by data*. Acceptancies by MC.
e =  e00 =  0.002
* G. Cabibbo : PhD Thesis, Roma “ La Sapienza ” University (in preparation)
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

30. BR(KS  p+p-)/BR(KS  p0p0) = 2.23  0.020  0.007
Result
On the ‘99 sample:
NKcr =
N+- =
N00 =
Errors
statistical 0.3%
tag eff. 0.5%
e00 sel. eff. 0.7%
e+- sel. eff. 0.3%
trg eff. 0.5%
KLOE VERY PRELIMINARY:
BR(KS  p+p-)/BR(KS  p0p0) = 2.23   0.007
PDG mean value: 0.026
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

31. KS semileptonic decay KL p- n e+
BR (KS®pen) = (7.2±1.4) x 10-4 measured at VePP-2M with
75 events (15pb-1)
In KLOE with 5 pb-1 we expect ~150 semileptonic Ks decays tagged by the KLCrash and with 20% analysis efficiency (~8% stat error)
with 20pb-1 KLOE can measure this BR with a statistical error of 0.3 x 10-4 p- e+ n KL
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

32. Invariant mass of pen events (MeV/c2)
KS Semileptonic decay
After Kinematic and time of flight cuts the Ks mass
is reconstructed using the n momentum obtained from the KlCrash
Invariant mass of pen events (MeV/c2)
Number of events / 5MeV/c2
127 events
after background
subtraction
Including data from July run
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

33. The July 2000 data taking All data reconstructed at
Aug 5
Inverse nb
Jul 5
Jul/Aug 2000 L dt = 4.18 pb-1
corresponding to:
1.2 × 107 f’s
1.7 × 106 KSKL KS  p+p- Tag
1.4 × 106 KSKL KLCRASH Tag
5.1 × 106 K+K- Vertex tag
All data reconstructed at
acquisition
Detectors continuously
calibrated on-line
Calo: energy/time calibration
DCH s-t relations
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

34. Luminosity and background
19 July
The background in October was slightly lower than the one observed in July at lower luminosity
9 Oct
From the July run to the
Sept-Oct run we had an increase of peak and integrated luminosity:
Lpeak(10  12) x 1030
Lint(220  320) nb-1/day
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

35. Data quality Ks Mass reconstruction stable during the full july run.
July/August 2000
Center of mass energy monitored by the KLOE offline analysis:
All the “jumps” are correlated with machine changes and f scan.
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

36. Conclusions: Detector
The detector is performing very well:
The calorimeter performances are unaffected by the high bkg
The chamber working point has been varied to cope with the bkg but still the performances are good
The Slow Control provides lot of information to DAFNE helping in manageing the bkg.
The Trigger rate is too high, overloading the data reconstruction
DAQ system works very well even at high rate (10 KHz)
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma

37. Conclusions: Physics In Y2K with 20 pb-1 of good data KLOE can obtain:
New measurements on the f radiative decay with ~factor 3 better accuracy than present PDG values
Precise measurements of the KS®pen decays
A definitive measurements of BR(KS  p+p-)/BR(KSp0p0)
Refine the KLKs decays analysis to prepare for e’/e
In 2001 with 200 pb-1 KLOE can produce:
R(e’/e) to ~ 10-3
Ke4 decays
Non leptonic radiative decays
+…...
KLOE S.C. 13/10/2000
L.Pontecorvo INFN Roma