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

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

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

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

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

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 100-200 ps corrected run by run. IT stable during runs KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

Calorimeter Performances Mass reconstruction of fully neutral final states Ks 0 0 Mk= 494 MeV k = 27 MeV Calorimeter efficiency vs energy (20 - 200 MeV) measured using rad Bhabha KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

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

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

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

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

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) = 135.3+0.1 MeV KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

Drift Chamber Accidentals Positron Injection Charge integrated in July: Q  1 mC/cm/month Wire ageing: lab-tested @ Q = 2.5-5 mC/cm, no effect literature: QMAX = 10-50 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

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

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 = 99.89  0.02% ( p0p0 ) etrig = 98.15  0.04% ( p+p- ) KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

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

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

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

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 > 0.84 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

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 = 195+22 with M(p0 p0)> 700 MeV/c2 KLOE preliminary: BR(f  p0p0g f0Region)= (0.81+0.09+0.06)10-4 [vs BR=(1.034+0.066 +0.046)10-4 (SND-2) and BR=(0.92+0.08 +0.06)10-4 (CMD-2)] KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

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=(0.88+0.14 +0.09)10-4 (SND-2) and BR=(0.90+0.24 +0.10)10-4 (CMD-2)] KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

f  hg , f  p0g fit. (1.297+0.033)  10-2 p0g band hg band After bkg subtraction we obtain: Nhg=23428 + 153(stat) + 167(syst) Np0g =5825 + 76(stat) + 64(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 ) = (1.26+0.01+0.01(Syst)+0.06(Lum))10-2 fit. (1.297+0.033)  10-2 PDG 2000 Aver.(1.26+0.04)  10-2 SND2000 (1.312+0.012+0.052)10-2 CMD2-2000 (1.18+0.03+0.06)  10-2 hg band p0g band BR ( f  p0g ) = (1.31+0.02+0.03(Syst) +0.06(Lum))10-3 fit. (1.26+0.10)  10-2 PDG 2000 Aver.(1.31+0.13)  10-2 SND2000 (1.226+0.036+0.093)10-2 KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

f  h'g F  h'g, h' hp+p-, h gg F  h'g, h' hp0p0, h gg Nev sel = 21+4.6 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 )= (7.1+1.6+0.3)10-3 (charged) (6.9+3.8 +0.9)10-3 (fully neutral) BR (Fh’g)= (8.9+2.0 +0.6)10-5 -0.6 KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

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

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

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

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

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

Efficiency determination T0 efficiencies Tagging: KLCrash Tagging efficiencies is different for neutral and charged decays: ratio of tagging efficiencies determined directly by data* atag = 0.951  0.003 Cluster efficiencies Decay selection: Dominated by tracking efficiency ( p+p- ) and clustering efficiency ( p0p0 ) determined by data*. Acceptancies by MC. e = 0.814  0.004 e00 = 0.576  0.002 * G. Cabibbo : PhD Thesis, Roma “ La Sapienza ” University (in preparation) KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

BR(KS  p+p-)/BR(KS  p0p0) = 2.23  0.020  0.007 Result On the ‘99 sample: NKcr = 697331 N+- = 294157 N00 = 102630 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  0.020  0.007 PDG mean value: 2.1970.026 KLOE S.C. 13/10/2000 L.Pontecorvo INFN Roma

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

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

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

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

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

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

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