Hadron 07 Frascati 09102007 KLOE results on hadron

Hadron 07, Frascati 09/10/2007 KLOE results on hadron physics Cesare Bini Università “La Sapienza” and INFN Roma on behalf of the KLOE collaboration Outline: 1. The KLOE experiment 2. Results on pseudoscalar mesons 3. Results on scalar mesons 4. Prospects

1. The KLOE experiment at DA NE DAFNE @ Frascati Laboratories • e+e- collider with 2 separate rings: s = M = 1019. 4 Me. V • Luminosity up to 1. 5× 1032 cm-2 s-1 • 2 interaction regions 1. KLOE 2700 pb-1 2. DEAR (kaonic atoms) 100 pb-1 FINUDA (hypernuclei) 1100 pb-1 KLOE STATUS: March 2006: end of KLOE data taking 2500 pb-1 on-peak 8 × 109 decays 200 pb-1 off-peak (energy scan+1 Ge. V run) Dafne test in progress

The KLOE physics program: Kaon physics: CP and CPT violation, CKM unitarity, rare decays, Ch. PT tests Hadron physics: lowest mass pseudoscalar, scalar and vector mesons Hadronic cross-section below 1 Ge. V: hadronic corrections to g-2 List of the decays: branching ratios and number of events “on tape” B. R. Nev KLOE (2. 5 fb-1) K+K 0. 49 K 0 K 0 KSKL 0. 33 0. 15 1. 3 10 -2 1. 2 10 -3 ’ 6. 2 10 -5 (f 0(980), ) 3 10 -4 (a 0(980)) 7 10 -5 KK (f 0(980), a 0(980)) ? 3. 7 109 2. 5 109 1. 1 109 9. 7 107 9. 0 106 4. 6 105 2. 5 106 4. 6 105 ? Initial State Radiation e+e-

The KLOE detector: A large drift chamber A hermetic calorimeter A solenoidal superconducting coil Drift Chamber (He-Iso. But. 2 m × 3 m) E. M. Calorimeter (lead-scintillating fibres) Magnetic field (Super. Conducting Coil) = 0. 52 T (solenoid)

2. Results on pseudoscalar mesons. Results presented here: 2. 1 Precision measurement of the mass 2. 2 Improved measurement of the - ’ mixing (also 0) 2. 3 Dynamics of 3 decays 2. 4 Measurement of KS 2. 5 Preliminary measurement of B. R. ( -e+e-) 2. 6 A flash on 0 Talks by: F. Ambrosino, A. De Santis, B. Di Micco, R. Versaci (Light Meson Spectroscopy I) M. Martini (Low energy QCD)

2. 1 Precision measurement of the mass Motivated by the discrepancy between the two best measurements: NA 48 (2002) M( ) = 547. 843 ± 0. 030 ± 0. 041 Me. V GEM (2005) M( ) = 547. 311 ± 0. 028 ± 0. 032 Me. V ( >10 , PDG average gives a scale factor of 5. 8 !) Recently a new measurement has been published by CLEO: CLEO (2007) M( ) = 547. 785 ± 0. 017 ± 0. 057 Me. V KLOE method: analysis of fully neutral 3 events with ü 3 clusters in the calorimeter only. üKinematic fit with 4 constraints ==> energies by cluster positions üDiscrimination between and very easy from Dalitz plot. üAbsolute energy scale from the e+e- center of mass energy s (kinematic fit input) - calibrated comparing M( ) obtained by the energy scan to the PDG value (dominated by CMD-2)

3 Dalitz plot KLOE final result: M( ) = 547. 873 ± 0. 007 ± 0. 031 Me. V Systematic error due to: - detector uniformity; - Dalitz plot cuts. mass check: M( ) = 134. 906 0. 012 0. 048 (compatible at 1. 5 with PDG) mass peak

2. 2 Measurement of the – ’ mixing KLOE method: measurement of 2002 result (Phys. Lett. B 541, 45) 2007 result (Phys. Lett. B 648, 267) Lint= 16 pb-1 , final states Lint=427 pb-1 , final states 2002 2007 N( ) 5 107 1. 4 109 N( ) 5 104 1. 7 106 N( ’) 120 3400 R (4. 70 0. 47 0. 31) 10 -3 (4. 77 0. 09 0. 19) 10 -3 BR( ’ ) (6. 10 0. 61 0. 43) 10 -5 (6. 20 0. 11 0. 25) 10 -5 P(*) (41. 8 +1. 9 -1. 6)o (41. 4 0. 3 0. 9)o Errors are now dominated by “intermediate and ’ B. R. s”: (BR( ’ ) known @ 3%, BR(( ’ ) @ 5. 7%) (*) evaluated according to A. Bramon et al. , Eur. Phys. J. C 7, 271 (1999)

Constrain to the ’ gluonium content: KLOE analysis uses the constraints: J. L. Rosner, Phys. Rev. D 27 (1983) 1101, A. Bramon et al. , Phys. Lett. B 503(2001) 271 E. Kou, Phys. Rev. D 63(2001) 54027 Y 1: ’ Y 2: ’ Y 3: R Y 4: ’ A >3 effect is found: Z 2 ’ = 0. 14 0. 04 P = (39. 7 0. 7)o R. Escribano, J. Nadal (JHEP 0705, 006, 2007) reanalyze all V P and P V decays updating wavefunction overlaps parameters and neglecting the Y 1 constraint no evidence of gluonium content Experimentally: improve ( ’), BR( ’ ), ’ , BR( 0 )

e+e- 0: interference pattern between decay and continuum: fit of cross-section s dependence using 2 decays channels of the . Cross-section parametrization: Preliminary results: BR( 0)=(5. 63± 0. 70)× 10 -5 ( )/ ( )=0. 0934± 0. 0021 Using PDG values for the main decay we get: BR( )=(8. 40± 0. 19)% (error reduced to 2%, central value shifted – 6%)

2. 3 Dynamics of the 3 decay ' 3 decay isospin violation in strong interactions mu md ms A test of low energy effective theories of QCD KLOE has studied with high statistics the dynamics of both channels: (a) Dalitz plot analysis: 1. 34 106 events (b) ”slope” analysis: 0. 65 106 events (a) Dalitz plot (submitted to Phys. Lett. B): - large statistics - negligible background - use X and Y variables

Fit results of the Dalitz plot Including systematic errors a=-1. 090 0. 005 +0. 008 -0. 019 b= 0. 124 0. 006 0. 010 d= 0. 057 0. 006 +0. 007 -0. 016 f= 0. 14 0. 01 0. 02 Comments: 0. the odd terms (c and e) in X are compatible with 0 (no asymmetries); 1. the quadratic term in X (d) is unambiguosly different from 0; 2. the cubic term in Y (f) is needed to get an acceptable fit; 3. the b=a 2/2 (current algebra rule) is largely violated.

Dalitz plot asymmetries test of C invariance Left-Right C-invariance Quadrant C-invariance in I=2 amplit. Sextant C-invariance in I=1 amplit. (see J. G. Layter et al. , Phys. Rev. Lett. 29 (1972) 316) KLOE results: x 5 statistics respect to best previous experiment All asymmetries are compatible with 0 up to the 10 -3 level

(b) Fit results of the ”slope” The slope is evaluated by comparing the z distribution of the data with a Montecarlo simulation with =0 (pure phase space) High sensitivity to the M( ) value (Dalitz plot contour) MC with M( )=547. 3 New (preliminary) result: MC with M( )=547. 822 = -0. 027 0. 004 +0. 004 -0. 006 in agreement with Crystal Ball ( =-0. 031 0. 004);

2. 4 Measurement of the decay KS BR estimated by Ch. PT @ order p 4 (G. D’Ambrosio, D. Espriu, Phys. Lett. B 175 (1986)27) KLOE method: KSKL - KS tagging provided by KL interacting in the calorimeter: - Large background from KS decay (105 times more frequent) Red= MC signal Blue= MC background Points=data BR(KS )=(2. 27 0. 12(stat) 0. 05(syst)) 10 -6 Result compared to other experiments and theory

2. 5 Preliminary measurement of BR( -e+e-) -Up to now poorly measured (4 events CMD-2, 16 events CELSIUS-WASA); (WASA@COSY program) -BR predicted by Ch. PT and VMD models (2. 6 3. 6 × 10 -4); -Plane asymmetry “unconventional” CP violation ; (D. Gao, Mod. Phys. Lett. A 17 (2002) 1583) KLOE preliminary result based on 622 pb-1 (1/4 of full data sample) Event selection: 4 tracks events + 1 photon (363 Me. V ); Kinematic Fit -e recognition (kinematic and calo Pi. D (in progress)) Backgrounds: other decays (mainly and with conversion) charged kaon decays +

Fit of Minv( ee) with signal + background 733± 62 signal events (× 36 with respect to previous experiments) Total efficiency = 11. 7% Systematic uncertainty still under evaluation ( ) data points signal other decays other bckg (mainly K±) In progress: asymmetry Few % level sensitivity BR( -e+e-)=(2. 4 ± 0. 2 stat± 0. 4 syst) × 10 -4

2. 6 A flash on 0 Ch. PT “golden mode” KLOE has presented a 3 signal (only 1/5 of full statistics) CB@MAMI-B: BR=(22. 4± 4. 6± 1. 7) × 10 -5 4 mass spectrum of selected events (1. 5 fb-1 2005 data). Yellow = expected bck. Points = data The signal is confirmed in the full data sample. B. R. updated result with the full sample will have ~15% error

3. Results on scalar mesons. KLOE contribution to the understanding of the lowest mass scalars: f 0(980), a 0(980), (500) through radiative decays in pairs of pseudoscalars Mass (Ge. V/c 2) (1020) 1 a 0(980) f 0(980) Motivations: 1. |ss> scalar quark composition of f 0(980), a 0(980) 2. Search for evidence of (500) Results presented here: 3. 1 KLOE results on f 0(980) 3. 2 High statistics study of 3. 3 Search for the decay K 0 K 0 k(800) (500) 0 I=1/2 I=1 Talks by: S. Fiore, F. Nguyen (Light Meson Spectroscopy II)

3. 1 Update of KLOE results on f 0(980) KLOE observed the decay f 0(980) in and 0 0 channels: : Phys. Lett. B 634 (2006) 148; : Phys. Lett. B 537 (2002) 21; Eur. Phys. J. C 49 (2006) 433; Large “unreducible” backgrounds for both channels: w 0 and 0 for ; ISR, FSR and for Extraction of the scalar amplitude fit of the spectrum parametrization of signal and background Dalitz plot f 0(980) mass spectrum

Attempt to describe both spectra with a unique scalar amplitude. [Achasov and Kiselev, Phys. Rev. D 73 (2006) 054029]: Scalar amplitude = f 0(980) + (600) + interference. (600) parameters and /KK scattering phases fixed (10 different parameter sets, see Eur. Phys. J. C 49 (2006) 433) free parameters: Mf 0, gf 0 KK , gf 0 + Preliminary results (uncertainties under evaluation) are encouraging: Mf 0(Me. V) gf 0 KK (Ge. V) gf 0 + - (Ge. V) P(c 2) 982. 1 983. 7 4. 0 4. 7 -1. 7 -2. 2 6. 3% 2. 5% Comments: 1. The Kaon-Loop well describes the mass spectra; 2. The f 0(980) is strongly coupled to the s quark: gf 0 KK > gf 0 + 3. The scalar amplitude has a large low mass tail (m<600 Me. V) that can be interpreted as due to the (600); In progress: combined fit with improved background amplitudes

3. 2 High statistics study of : the a 0(980). “Pure” final state, dominance of a 0(980) intermediate state • Selection of: 1. events with : fully neutral 5 events; 2. events with : 2 tracks and 5 events • Background subtraction: 18% in sample 1, 13% in sample 2 • Event counting: 18400 in sample 1, 3600 in sample 2 Preliminary results on the branching ratio B. R. ( )(1) = (6. 92 0. 10 stat 0. 20 syst) 10 -5 B. R. ( )(2) = (7. 19 0. 17 stat 0. 24 syst) 10 -5 in good agreement, (part of the systematic errors are common). Error improvement: 9% (Phys. Lett. B 536 (2002) 216) 3% (this result) • M( ) spectra • Combined fit of the spectra with a 0 production parametrizations (convoluted with efficiencies and resolutions)

The fit parameters (preliminary). Ratio BR( )/BR( ) contribution (KL) Kaon-Loop: (N. Achasov, A. V. Kiselev, Phys. Rev. D 73(2006)054029) Ma 0, couplings ga 0 KK ga 0 , phase (NS) Breit-Wigner + polynominal “background”: (G. Isidori et al. , JHEP 0605 (2006) 049) Ma 0, couplings g a 0 ga 0 KK ga 0 KL fit: points =data red =fitting curve (model efficiency and resolution)

Comments: 1. Good consistency between sample 1 and 2: the result is experimentally “solid”; 2. KL fit is stable, NS requires to fix some parameters; Results: 2. 1 ga 0 KK ~ 2 Ge. V and ga 0 KK / ga 0 ~ 0. 8 “conflict” with qqqq hypothesis; 2. 2 Large values of BR( ) and of g a 0 sizeable coupling with the (as for f 0(980)) Other descriptions: Unitarized Chiral Model [Palomar et al. , Nucl. Phys. A 729 (2003) 743] KK molecule [Kalashnikova et al. , Eur. Phys. J. A 24 (2005) 437] Linear Sigma Model [Bramon et al. , Phys. Lett. B 494 (2000) 221] Meson g M (Ge. V-1) 0 0. 13 0. 71 ´ 0. 75 a 0(980) 1. 6 f 0(980) 1. 2 – 2. 7

3. 3 Search for the decay KSKS In K 0 K 0 the K 0 K 0 pair is: in a J=0 state = [|KSKS>-|KLKL>]/ 2; in a I=0, 1 isospin state a 0 and f 0 contribute; Very small allowed phase space: 2 MK < MKK < M small B. R. Predictions on B. R. : from 10 -13 (no scalar contribution) up to 10 -7 We have used the decay chain: KSKS ( ) 4 tracks+1 photon (E max=24 Me. V) Overall efficiency = 20. 6% Very small bckg (ISR KSKL) Result (preliminary): ( Ldt = 1. 4 fb-1) 1 event found; 0 expected background; BR( KSKS )<1. 8 10 -8 90% CL

4. Prospects. (talks by P. Moskal and D. Domenici (Future facilities)) DAFNE is testing now a new scheme to increase luminosity KLOE phase-2 could start ( 2009): ~10 times more statistics improved detector (inner tracker, improved calorimeter readout, tagger, new small angle calorimeters) “enriched” physics program Kaon, , ’ decays (high statistics) (sigma), 0 2 width deeply bound kaonic states (AMADEUS proposal) Increase the center of mass energy up to 2. 5 Ge. V is also considered (KLOE phase-3) physics program extended to hadronic cross-section (g-2, em) baryon time-like form factors (DANTE proposal) physics ( , ’, f 0(980), a 0(980) 2 widths) [see http: //www. lnf. infn. it/lnfadmin/direzione/roadmap. html F. Ambrosino et al. , Eur. Phys. J. C 50, 729 (2007)]