Recent results from KLOE Cesare Bini Universita La Sapienza and INFN Roma 1.The KLOE physics program 2.The KLOE detector 3.Status of the experiment 4.Results on neutral kaon decays 5.Results on radiative decays 6.Conclusions and perspectives 1. The KLOE physics program. e + e W = m = MeV b Decay channels K + K = 49.2% Charged Kaon decays + CP/CPT tests K 0 K 0 = 33.8% Neutral Kaon decays + CP/CPT tests ( / ) = 15.5% 3 pion decay ( shape parameters) = 1.3% Radiative decays: pseudoscalar: physics = ~10 -3 = ~10 -4 pseudoscalar mixing angle = ~10 -4 scalar f0 = ~10 -4 a0 e + e = ~10 -4 Conversion decays: transition form factor F e + e = ~10 -5 F e + e Initial state radiation (e + e ) 2m < W < m e + e around peak (energy scan) resonance parameters 2. The KLOE detector : Drift chamber Calorimeter (Pb-scint.fib.) Magnetic field = 0.56 T Drift chamber: Large volume d=4m l=3.3m He Isob gas mixt. Momentum resolution p/p < 0.4% Calorimeter: Energy resolution: /E = 5.4% / (E(GeV)) Time resolution t = 55 ps / (E(GeV)) 40 ps (cal.) 120 ps (coll.time) Present day performance: peak average L(cm 2 s 1 ) 5 10 31 day L dt (pb 1 ) Status of the experiment Data taken from april 1999 to december 2001~ at peak + 1 energy scan Analysis status: 2000 data ~completed (25 pb -1 7.5 x 10 7 ) 2001 data in progress (190 pb -1 5.7 x 10 8 ) All results are still preliminary 4.Results on Neutral Kaon decays Neutral kaons produced in a pure quantum J PC = 1 state: p K = 110 MeV S = 6 mm L = 3.5 m Tagging: pure K S and K L beams analysis of kaon decays double ratio ( / ) Interferometry studies Example of K S K L K S tagging by identification of K L interacting in the EmC (K L crash) [ ~50% of K L ] Selection cuts: E clus > 200 MeV |cos( clus )| < 0.7 ( = K L velocity in the rest frame) Position of the K L K S momentum Tagging efficiency tag ~ 30% K S tagging by identification of K L interacting in the EmC (K L crash) [ ~50% of K L ] Selection cuts: E clus > 200 MeV |cos( clus )| < 0.7 ( = K L velocity in the rest frame) Position of the K L K S momentum Tagging efficiency tag ~ 30% * distribution of K L crash Example of K S K L crash KLOE has now about tagged K S. All channels are accessible. Results from 2000 data ( tagged K S ) on: (1) R= (K S + - ) / (K S 0 0 ) (2) BR(K S e ) (1)R= (K S + - ) / (K S 0 0 ) Motivations: First part of double ratio Extractions of Isospin Amplitudes and Phases A 0 A 2 and 0 - 2 consistent treatment of soft in K S + - ( ) (PDG data contain ambiguities) [Cirigliano, Donoghue, Golowich 2000] Selection procedure: 1. K S tagging 2. K S + - ( ) two tracks from I.P + acceptance cuts: fully inclusive measurement (E up to E max =170 MeV) (E *) from MC folded to theoretical spectrum correction = (-3.4 0.1) x K S 0 0 neutral prompt cluster (E >20 MeV and (T-R/c) < 5 t ) at least 3 neutral prompt clusters ( 0 e + e - included) Result: N ev (K S + - ) = x 10 6 N ev (K S 0 0 ) = x 10 6 R = stat syst stat. uncertainty at 0.14% level contributions to systematics: tagging eff. Ratio 0.55% photon counting 0.20% tracking 0.26% Trigger 0.23% Total syst. uncertainty 0.68% PDG 2001 average is ( without clear indication of E cut ) With 2001 data (180 pb-1) improvement on: absolute scale tagg.eff. Bias statistics of control sub-samples E spectrum (2) BR(K S e ) Motivation: If (CPT ok).AND. ( S= Q at work): (K S e ) = (K L e ) BR(K S e ) = BR(K L e ) x ( L / S ) = ( ) x (using all PDG information). Only one measurement (CMD ): = ( 7.2 1.4 ) x Selection procedure Vertex with two tracks from I.P. kinematics (against huge background) time of flight ( electron vs pion) final signal variable = E miss -|p miss | BR evaluation: normalization to K S + ( (BR)~0.5%) both charge states are considered (well separated charge asymmetry) ToF selection illustrated for MC: 1. K S + MC events 2. K S e MC events Result: N ev (K S e = 627 30 [after the fit, residual background subtraction is included] BR(K S e ) = (6.79 0.33 stat 0.16 syst ) x stat. uncertainty at 4.7% level contributions to systematics: tag eff, ratio 0.6% tracking + vertex 2.0% time of flight 0.8% trigger + t0 0.9% Total systematics 2.4% BR(K S e ) 5.Results on radiative decays Pseudoscalar + According to quark model: assuming: no other content (e.g. gluonic)) 0 = (uu-dd)/ 2 = cos P (uu+dd)/ 2 + sin P ss = -sin P (uu+dd)/ 2 + cos P ss assuming: = ss state ( V =0) assuming: no OZI-rule violations g( ) = F s cos V cos P F q sin V sin P g( ) = F s cos V sin P + F q sin V cos P ( V P = mixing angles in the flavour base) ( F s F q = form factors) ( ) K R = = cotg 2 P ( ) 3 ( ) K Decay chain used: (same topology 2T + 3 photons / final states different kinematics) (a) (b) Selection: 2t (E T1 +E T2 7 MeV kinematic fit (without mass const.) Result: N ev = 2438 61 BR( )=(1.09 0.03 stat 0.05 syst )x10 -4 CMD-2 (0.92 0.08 0.06)x10 -4 SND (1.14 0.10 0.12)x10 -4 Fit to the M spectrum (kaon loop): contributions from f 0 + strong negative interference negligible contribution Fit results: M(f 0 ) = 973 1 MeV g 2 (f 0 KK)/4 = 2.79 0.12 GeV 2 g(f 0 ) /g(f 0 KK) = 0.50 0.01 g( ) = BR( f 0 ) = (1.49 0.07)x10 -4 Measured in 2 final states: (Sample 1) (5 ) is the main background 5 selection (see ) + kinem. fit (Sample 2) (2t + 5 ) Negligible bckg with the same topology: e + e 0 2t + 4 K S K L (K L prompt decay) 2t + 4/6 2t + 5 selection + kinem.fit Results: (Sample1) N ev = 916 N bck = 309 20 BR( ) = (8.5 0.5 stat 0.6 syst )x10 -5 (Sample2) N ev = 197 N bck = 4 4 BR( ) = (8.0 0.6 stat 0.5 syst )x10 -5 CMD-2 (9.0 2.4 1.0) x SND (8.8 1.4 0.9) x Combined fit to the M spectra: dominated by a 0 negligible Fit results: M(a 0 ) = MeV (PDG) g 2 (a 0 KK)/4 = 0.40 0.04 GeV 2 g(a 0 ) /g(a 0 KK) = 1.35 0.09 BR( a 0 ) = (7.4 0.7)x10 -5 Interpretation of KLOE results on scalars (within the context of kaon-loop framework): (preliminary) parameter KLOE result 4q model qq(1) model qq(2) model g 2 (f 0 KK)/4 (GeV 2 ) 2.79 0.12 super-allowed OZI-allowed OZI-forbidden g(f 0 ) /g(f 0 KK) 0.50 g 2 (a 0 KK)/4 (GeV 2 ) 0.40 0.04 super-allowed OZI-forbidden OZI-forbidden g(a 0 ) /g(a 0 KK) 1.35 4q doesnt describe a 0 parameters; 4q compatible with f 0 parameters; f 0 /a 0 ratio sensitive to isospin mixing [Close Kirke 2001] : BR( f 0 ) g 2 (f 0 KK) = 6.0 0.6 ; = 6.9 1.0 BR( a 0 ) g 2 (a 0 KK) if F f0 (R) = F a0 (R) S = (47 2) o [no isospin mixing S = 45 o ] f 0 = ss f 0 = (uu+dd)/ 2 a 0 = (uu-dd)/ 2 a 0 = (uu-dd)/ 2 6. Conclusions and perspectives DAFNE performance has improved considerably during the first two years of KLOE data taking KLOE detector well performing and under control From 2000 data (25 pb -1 ) results on: K S decays radiative decays improve previous PDG knowledge Analysis of 2001 data (190 pb -1 ) in progress. Expected new results will be: rare K S decays [ , , limits on 3 ] K L decays [ , .] K decays decays (6 x10 6 produced) [chiral perturbation theory checks] hadronic cross-section (e + e ) 2m < W < m Data taking 2002 starting now 500 pb -1 realistic by end of the year Detector calibrated on-line (run by run ~ hour): - Drift Chamber s-t relations momentum scale (M K ) - Calorimeter energy scale (e + e - ) time scale + offset - s and p evaluated (Bhabha K S, K L ) Start reconstruction and event classification (~ 1 hour delay) Efficiencies are evaluated and monitored using data control samples: photon detection efficiency ~ 99% on most of the energy range + decrease below 100 MeV tracking efficiency ~ 97.5% + decrease at small p T and trigger efficiency in case of K S K L configuration if K S triggers measure K L trigger efficiency if K L triggers measure K S trigger efficiency Decay chain used: (same topology 2T + 3 photons / final states different kinematics) (a) (b) MC Selection: 2 tracks (E T1 +E T2 20 MeV and (T-R/c) < 5 t ) at least 3 neutral prompt clusters ( 0 e + e - included) Soft photon emission: (E *) not uniform correction Theoretical spectrum folded with experimental efficiency = (-3.4 0.1) x 10 -3 Scalar (0 ++ quantum numbers) + [f 0 I=0, a 0 I=1, I=0] (f 0 , f 0, ) 5 final state ( ) 2t + 1 final state: huge background from: ISR (radiative return) FSR + interference (signal hidden) a 0 a 0 ) [ ] 5 final state (40%) [ ] 9 final state (32%) [ ] 2t + 5 final state (23%) Motivations: f 0, a 0, not easily accomodated in a qq nonet; qqqq states (lower mass) [Jaffe 1977]; KK molecule (m(f 0,a 0 )~2m(K)) [Weinstein, Isgur 1990]; f 0 , a 0 sensitive to f 0,a 0 nature [Achasov, Ivanchenko 1989]: f 0,a 0 Kaon loop Final state