Results from KLOE LNF Scientific Committee 23/05/2002 C.Bini

1. Results from KLOE LNF Scientific Committee 23/05/2002 C.Bini Universita’ “La Sapienza” and INFN Roma (1) First published papers (2) Analyses in progress (3) 2001/2002 data physics perspectives

2. KLOE physics papers [4+1] (based on data taken in 2000: ~20 pb-1): (1) Measurement of the branching fraction for the decay KS  p e n Phys.Lett. B 535 37 (2002) (2)Study of the decay f  hp0g with the KLOE detector Phys.Lett. B 536 209 (2002) (3)Study of the decay f  p0p0g with the KLOE detector • Phys.Lett.B 537 21 (2002) • (4)Measurement of G(KSp+p-(g))/G(KSp0p0) • hep-ex/0204024 , accepted by Phys.Lett.B • (5)Measurement of f  h’g / f  hg • KLOE Note 179 , to be submitted to Phys.Lett. B • KLOE detector papers: • (6) The KLOE electromagnetic calorimeter • Nucl.Instr. and Meth. A482 364 (2002) • (7) The QCAL tile calorimeter of KLOE • Nucl.Instr. and Meth. A483 649 (2002) • (8) The KLOE drift chamber • accepted by Nucl.Instr. and Meth. A • (9) The KLOE trigger system • submitted to Nucl.Instr. and Meth. A

3.  Results on KS physics [papers (1) and (4)]: tagging of a pure KS beam (unique opportunity of a f-factory). • KL interaction in the calorimeter (ToF signature) •  s measurement • KS “tagging” Analysis of 2000 data concentrated on: semileptonic KS decay G(KSp+p-(g)) / G(KSp0p0) Other analyses in progress on larger statistics. • Measurement of KS decays

4. KSSemileptonic decays Paper dedicated to the memory of L. Paoluzi • Motivation: •  If (CPT ok) .AND. (DS=DQ at work): • G(KS p en) = G(KL p en) BR(KS p en) = BR(KL p en) x (GL/GS) • = ( 6.704 ± 0.071 ) x 10-4 • (using all PDG information). • Only one measurement 75events (CMD-2 1999): • = ( 7.2 ± 1.4 ) x 10-4 MC: the signal Selection uses: 2 tracks invariant mass difference of ToF between e and p ToF selection illustrated for MC events Notice: sign of the charge is determined  Semileptonic asymmetry accessible MC: the background

5. 2000 After ToF cuts  assignment of electron and pion  Emiss –Pmiss distribution  a clear signal peaked at 0 Result from 17 pb-1 BR(KS p en) BR(KS p en) = (6.91 ± 0.34stat ± 0.15syst) x 10-4

6. G(KSp+p- (g)) / G(KSp0p0) Motivations:  First part of double ratio Notice: experiments measure double ratio at 0.1% and the single ratio at 1% KLOE aims to measure each single ratio (KL and KS)at 0.1%  Extractions of Isospin Amplitudes and Phases A0 A2and d0-d2 consistent treatment of soft g in KS p+p- (g) [Cirigliano, Donoghue, Golowich 2000] Selection procedure: 1. KS tagging 2. KS p+p-(g) two tracks from I.P + acceptance cuts: fully inclusive measurement: no request on g in calorimeter e pp(g) eppg(Eg*) from MC  folded to theoretical g spectrum 3.KS p0p0 neutral prompt cluster (Eg>20 MeV and (T-R/c) < 5st ) at least 3 neutral prompt clusters (p0 e+e-g included)

7. Result (from 17 pb-1): Nev (KS p+p- ) = 1.098 x 106 Nev (KS p0p0 ) = 0.788 x 106 R = 2.239 ± 0.003stat ± 0.015syst  stat. uncertainty at 0.14% level  contributions to “systematic”: tagging eff. Ratio 0.55% photon counting 0.20% tracking 0.26% Trigger 0.23% -------------------------------------- Total syst. uncertainty 0.68% PDG 2001 average is 2.197 ± 0.026 ( without clear indication of Eg*cut ) Notice: efficiencies by data control samples (statistically limited) Goal = reach 0.1% systematic uncertainty [< 2 x 10-4 on Re(e’/e)].

8. Results on f radiative decays: [papers (2), (3) and (5)] Rad. Decay BR (PDG) hg 1.26% p0g 1.3 x10-3 h’g ~10-4 ppg ~10-4 hp0g ~10-4 f P (0-+) g f  S (0++) g S  pp / hp • Analysis of 2000 data on: • f h’g / hg[paper (5)] • f  p0p0g[paper (2)] • f  hp0g[paper (3)]

9. f Scalar Meson + g[f0(980) I=0, a0(980) I=1] • Motivations: • f0, a0, not easily interpreted as qq states; other interpretations suggested: •  qqqq states (lower mass) [Jaffe 1977]; •  KK molecule (m(f0,a0)~2m(K)) [Weinstein, Isgur 1990]; •  f0g , a0g BR, mass spectra sensitive to f0,a0 nature [Achasov, Ivanchenko 1989]: Kaon loop approach: radiative g f0,a0 f Kaon loop final state Overlap = structure dependent function k = f0 momentum g(fKK) from G(fK+K-) g(f0KK) g(a0KK) f0, a0 model g(f0pp) g(a0hp) M(p0p0) M(hp) spectra

10. f  p0p0g  5g Result (from 17 pb-1): Nev = 2438  61 BR(f  p0p0g )=(1.09  0.03stat  0.05syst)x10-4 CMD-2 (0.920.080.06)x10-4 SND (1.140.100.12)x10-4 Fit to the Mppspectrum (kaon loop): contributions from f  f0g f  sg + “strong” negative interference negligible contribution f  r0p0 p0p0g Fit results: M(f0) = 973  1 MeV g2(f0KK)/4p = 2.79  0.12 GeV2 g(f0pp) /g(f0KK) = 0.50  0.01 g(fsg) = 0.060  0.008 BR(f  f0g  p0p0g ) = (1.49  0.07)x10-4

11. f  hp0g Measured in 2 final states: (Sample 1) h  gg (5g) (Sample 2) h  p+p-p0 (2t + 5g) Results (from 17 pb-1): (Sample1) Nev = 916 Nbck = 309  20 BR(f  hp0g) = (8.5  0.5stat 0.6syst)x10-5 (Sample2) Nev = 197 Nbck = 4  4 BR(f  hp0g) = (8.0  0.6stat 0.5syst)x10-5 CMD-2 (9.02.41.0) x 10-5 SND (8.81.40.9) x 10-5 Combined fit to the Mhp spectra: dominated by f a0g negligible f  r0p0 hp0g Fit results: M(a0) = 984.8 MeV (PDG) g2(a0KK)/4p = 0.40  0.04 GeV2 g(a0hp) /g(a0KK) = 1.35  0.09 BR(f  a0g  hp0g) = (7.4  0.7)x10-5

12. Summary: KLOE Results on Scalars vs. models. KLOE qqqq qq(1) qq(2) g2f0KK/(4) 2.790.12“super-allowed” “OZI-allowed” “OZI-forbidden” (GeV2) (~2 GeV2) g2a0KK/(4) 0.400.04“super-allowed” “OZI-forbidden” “OZI-forbidden” (GeV2) (~2 GeV2) gf0 /gf0KK 0.500.010.3—0.5 0.5 2 ga0/ga0KK 1.350.090.9 1.5 1.5 • f0parameters compatible with 4q model • a0parameters not well described by the 4q model • (2001 data  more accurate study of a0)

13. f Pseudoscalar + g  hg  h’g According to quark model:  assuming: no other contents (e.g. gluon)) p0 = (uu-dd)/2 h = cosaP(uu+dd)/2 + sinaPss h’ = -sinaP(uu+dd)/2 + cosaPss  assuming: f = ss state (aV=0) (F slowly varying function; model dependent) G(f  h’g) Kh’ R = = cotg2aP ( )3 x F(aP, aV) G(f  hg) Kh • Decay chains used: (same topology 2T + 3 photons / final states different kinematics) • (a) f  hg  p+p-p0g  p+p- 3g • (b) f  h’g  h p+p-g  p+p- 3g

14. Results: N(a) = 50210  220 N(b) = 120  12stat ±5bck Invariant mass spectrum of h’g • to get R, effect of non resonant e+e-( : • 5% correction (opposite sign interference of r with h and h’) • BR(f h’g) • R = = (4.70  0.47stat 0.31syst) x 10-3 • BR(f hg) • aP = ( 41.8  1.7)o [ qP = (-12.9  1.7)o ] Using the PDG value for BR(f  hg )  BR(f  h’g )[PDG : (6.7 )  10-5 ] BR(f  h’g ) = (6.10  0.61stat 0.43syst) x 10-5 • + preliminary result using +-7;  +-(00) 000 (+-0) • BR (f  h’g )= (7.0  0.6  1.0)  10-5 (not included in paper (5))

15. 10 8 6 4 2 0 2000 data comparison of KLOE results on BR (f  h’g ) with previous results (from VEPP-2M) BR (f  h’g ) x 10-5 CMD-2 SND KLOE BR (f  h’g ) helps in assessing the h’ gluon content: combined analysis. h’ = X h’(uu+dd)/2 + Y h’ ss + Z h’ gluonium Assume Z h’ =0  evaluate X h’ from other channels  evaluate Y h’ from f  h’g Result

16. Analyses in progress(aim to publish by end of 2002): • Published results x 10 statistics + improve systematic. In particular: -BR(KS p en) measurement down to 2% + first look at charge asymmetry -G(KSp+p-(g))/G(KSp0p0) measurement down to 0.1% (work on systematic) • -high statistics a0 spectrum •  KL  gg / KL  3p0(**) •  Hadronic cross-section s(e+e-  p+p-) vs s 2mp < s < mf (**) •  Measurement of the K0 mass from f  KSKL, KS  p+p-KLOE Note 181(**) •  Dynamics of the f  p+p-p0 decay  r+ r- r0 parameters •  Upper limit on h  ggg (test of C invariance in EM decays) KLOE Note 180

17. G(KL gg ) / G( KL p0p0p0 ) Motivations:  Long distance contribution to the rare KL  m+m- decay  Predictions on KS  gg  Test of Chiral Perturbation Theory BR(KL gg) = (5.86 ±0.15) x 10-4 [NA31 BR(KL gg) /BR ( KL p0p0)] KLOE improvement to 1% measurement Drift Chamber volume • Normalization to BR (KL p0p0p0) • 1.3% uncertainty (not 2.2%) KL p0p0p0 well measured in all the fiducial volume: Measurement of tKL

18. Event Selection:  KL tagging (by KS  p+p-)  Neutral Vertex from 2 g Eg > 100 MeV 8540 ± 120 events (after background subtraction) from 150 pb-1 analyzed Efficiency checks in progress (data vs Montecarlo) Distribution of M(gg): data (red) MC signal (black) MC bckg (blue)

19. Hadronic cross-section s(e+e-  p+p-) vs s 2mp < s < mf Measured by Radiative Return complementary approach to the standard energy scan Key points: knowledge of ISR function background (mostly FSR)  EVA Montecarlo Selectp+p-g events. Tracks from I.R. 40o < TRACK < 140o + Part.ID using calorimeter. 1) large angle 55o <  < 125o (blue)a g in the calorimeter required 2) small angle  < 15o or  > 165o (red) no g required Sample 1) = higher background (FSR + p+p-p0); all Mpp spectrum Sample 2) = higher s, less background but kinematically limited (acceptance loss) ds dM2pp pions M2pp photon

20. Comparison of data (22.6 pb-1) with Montecarlo (EVA + detector response): [visible cross-section, no unfolding applied] 1) Large angle sample (45000 events) - 2) Small angle sample (265000 events) 55o < pp< 125o  < 15o or  > 165o • MC • data • MC • data d(ee  )/dM2(nb/GeV2) d(ee  )/dM2(nb/GeV2) (DATA-MC)/MC (%) (DATA-MC)/MC (%)

21. Outlook: • KLOE 2001 data (175 pb-1) are enough to measure the hadronic cross-section s(e+e- p+p-) with a statistical uncertainty of ~ 0.15% for small angle sample and ~ 0.3% for large angle sample. • The new NLO generator from Kühn et al. (PHOKARA,a,a2), improves the theoretical description of ISR. • The uncertainty from unaccounted higher order ISR is estimated to be around 0.5% (hep-ph/0112184) • Expected improvement in the knowledge of the radiator function and in the luminosity measurement. • Results are expected before the end of the year!

22. Measurement of the K0 mass from f  KSKL, KS  p+p- 1.0 0.8 0.6 0.4 0.2 0.0 Method: f  KSKL , KS  p+p- M2K=W2/4 - P2K W from e+e- invariant mass spectrum; absolute calibration from f - scan (normalizing to CMD-2 Mf value) PKfrom KS  p+p- Result: single event kaon mass resolution ~ 430 keV MK = 497.574 ± 0.005stat± 0.020syst MeV s(e+e- KSKL )(mb) 0.10 0.05 0.00 -0.05 -0.10 Ds (mb) 497.9 497.7 497.5 1015 1020 1025 1030 W (MeV) CMD-2 NA48 KLOE

23. 2001/2002 data physics perspectives: • KS decays: p+p-g with measurement of g spectrum •  gg • limits on  p0p0p0 • KL decays:  p+p- / p0p0 •  pl±n  sin qC • h decays: [6 x106h in 2001 tag from f  hg Eg = 363 MeV photon] •  ggg (improve C-test) •  p+p-g (photon spectrum) •  p+p-p0p0p0p0 (Dalitz plot slopes) •  p0gg (branching ratio) • [significant checks of Chiral Perturbation Theory]

24. K decays: mutual tagging [6 x 105 tags / pb-1  large statistics]but: • sensitive to machine background • difficult analysis (requiring specific tools) • List of items: •  p0l±n sin qC (check with sin qC from KL) •  p p0 … all K  BR can be improved •  m n  fK •  3pDalitz plot parameters • radiative decays final state + g Tagging: K+ m+n tags K- p- p0 momentum distribution of the daughter particle in the K rest frame: m n peak p p0 peak

25. Conclusion First 4+1 papers using a ~20 pb-1 sample: previous results are improved. We have learned how to extract physics results from our data: Machine parameters monitor and control (example) Calibration Efficiency from data Corrections to Montecarlo We warmly acknowledge the DAFNE team for their efforts in providing us good data.