Results from KLOE (1) First published papers (2) Analyses in progress 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

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

 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

KS Semileptonic 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 75 events (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

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

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 A2 and 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)

 stat. uncertainty at 0.14% level 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)].

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)]

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

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 Mpp spectrum (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

f  hp0g (Sample 1) h  gg (5g) Results (from 17 pb-1): 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

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0.01 0.3—0.5 0.5 2 ga0/ga0KK 1.350.09 0.9 1.5 1.5 f0 parameters compatible with 4q model a0 parameters not well described by the 4q model (2001 data  more accurate study of a0)

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  h g) 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

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  h g )  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))

comparison of KLOE results on BR (f  h’g ) 10 8 6 4 2 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

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

KL  p0p0p0 well measured in all the 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

 KL tagging (by KS  p+p-) 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)

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 Select p+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

[visible cross-section, no unfolding applied] 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 (%)

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!

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) PK from 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

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 x106 h in 2001 tag from f  hg Eg = 363 MeV photon]  ggg (improve C-test)  p+p-g (photon spectrum)  p+p-p0 p0p0p0 (Dalitz plot slopes)  p0gg (branching ratio) [significant checks of Chiral Perturbation Theory]

Tagging: K+  m+ n tags K-  p- p0 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  3p Dalitz 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

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.