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KLOE results on hadron physics

Hadron07, Frascati 09/10/2007. KLOE results on hadron physics. Cesare Bini Università “La Sapienza” and INFN Roma on behalf of the KLOE collaboration. Outline: The KLOE experiment Results on pseudoscalar mesons Results on scalar mesons Prospects. 1. The KLOE experiment at DA  NE.

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KLOE results on hadron physics

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  1. Hadron07, Frascati 09/10/2007 KLOE results on hadron physics Cesare Bini Università “La Sapienza” and INFN Roma on behalf of the KLOE collaboration Outline: The KLOE experiment Results on pseudoscalar mesons Results on scalar mesons Prospects

  2. 1. The KLOE experiment at DANE DAFNE @ Frascati Laboratories • e+e-collider with 2 separate rings: s = Mf= 1019.4 MeV • Luminosity up to 1.5×1032 cm-2s-1 • 2 interaction regions 1. KLOE2700 pb-1 2. DEAR (kaonic atoms) 100 pb-1FINUDA (hypernuclei) 1100 pb-1 KLOE STATUS:  March 2006: end of KLOE data taking 2500 pb-1 on-peak 8 × 109f decays 200 pb-1 off-peak (energy scan+1 GeV run)  Dafne test in progress

  3. The KLOE physics program: Kaon physics: CP and CPT violation, CKM unitarity, rare decays, ChPT tests Hadron physics: lowest mass pseudoscalar, scalar and vector mesons Hadronic cross-section below 1 GeV: 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 3.7  109 K0K0KSKL 0.33 2.5  109  0.15 1.1  109 1.3  10-2 9.7  107 1.2  10-3 9.0  106 ’6.2  10-5 4.6  105 (f0(980), )3  10-4 2.5  106  (a0(980))7  10-5 4.6  105 KK(f0(980), a0(980))?? Initial State Radiation e+e-

  4. The KLOE detector: A large drift chamber A hermetic calorimeter A solenoidal superconducting coil Drift Chamber (He-IsoBut. 2m × 3m) E.M. Calorimeter (lead-scintillating fibres) Magnetic field (SuperConducting Coil) = 0.52 T (solenoid)

  5. 2. Results on pseudoscalar mesons. Results presented here: 2.1 Precision measurement of the  mass 2.2 Improved measurement of the  - ’ mixing (also f wp0) 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 0gg Talks by: F.Ambrosino, A.De Santis, B.Di Micco, R.Versaci (Light Meson Spectroscopy I) M.Martini (Low energy QCD)

  6. 2.1 Precision measurement of the mass Motivated by the discrepancy between the two best measurements: NA48 (2002) M() = 547.843 ± 0.030 ± 0.041 MeV GEM (2005) M() = 547.311 ± 0.028 ± 0.032 MeV ( >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 MeV • KLOE method: analysis of fully neutral 3 events • with  • with • 3 clusters in the calorimeter only. • Kinematic fit with 4 constraints ==> energies by cluster positions • Discrimination between  and  very easy from Dalitz plot. • Absolute 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)

  7. 3Dalitz plot  mass peak KLOE final result: M() = 547.873 ± 0.007 ± 0.031 MeV Systematic error due to: - detector uniformity; - Dalitz plot cuts.  mass check: M() = 134.906  0.012  0.048 (compatible at 1.5s with PDG)

  8. 2.2 Measurement of the h – h’ mixing KLOE method: measurement of 2002 result (Phys.Lett.B541,45) Lint= 16 pb-1 ,  final states 2007 result (Phys.Lett.B648,267) Lint=427 pb-1 ,  final states 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. C7, 271 (1999)

  9. KLOE analysis uses the constraints: J.L.Rosner, Phys.Rev. D27 (1983) 1101, A.Bramon et al., Phys.Lett. B503(2001) 271 E.Kou, Phys.Rev.D63(2001) 54027 Y1: ’ Y2: ’ Y3: R Y4: ’ A >3 effect is found: Z2’ = 0.14  0.04 P = (39.7  0.7)o Constrain to the ’ gluonium content: R.Escribano, J.Nadal (JHEP 0705,006,2007) reanalyze all V P and P V decays updating wavefunction overlaps parameters and neglecting the Y1 constraint no evidence of gluonium content Experimentally: improve (’), BR(’), ’,BR(wp0g)

  10. e+e- wp0: interference pattern betweenfdecay and continuum: fit of cross-section s dependence using 2 decays channels of the w. Cross-section parametrization: p+p-p0p0 gp0p0 Preliminary results: BR(fwp0)=(5.63±0.70)×10-5 G(wp0g)/G(wp+p-p0)=0.0934±0.0021 Using PDG values for the main decay we get: BR(wp0g)=(8.40±0.19)%(error reduced to 2%, central value shifted –6%)

  11. 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

  12. 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=a2/2(current algebra rule) is largely violated.

  13. 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

  14. (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 MC with M()=547.822 New (preliminary) result:  = -0.027  0.004 +0.004-0.006  in agreement with Crystal Ball (=-0.0310.004);

  15. 2.4 Measurement of the decay KS  BR estimated by ChPT @ order p4 (G.D’Ambrosio, D.Espriu, Phys.Lett.B175 (1986)27) KLOE method:  KSKL - KStagging 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

  16. 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 ChPT and VMD models (2.63.6 × 10-4); • Plane asymmetry •  “unconventional” CP violation ; • (D.Gao, Mod.Phys.Lett.A17 (2002) 1583) KLOE preliminary result based on 622 pb-1 (1/4 of full data sample) Event selection: 4 tracks events + 1 photon (363 MeV ); Kinematic Fit p-e recognition (kinematic and calo PiD (in progress)) Backgrounds: other h decays (mainly and g with g conversion) charged kaon decays + rp

  17. Fit of Minv(ppee) with signal + background 733±62signal events (×36 with respect to previous experiments) Total efficiency = 11.7% Systematic uncertainty still under evaluation () data points signal other h decays other bckg (mainly K±) In progress: asymmetry  Few % level sensitivity BR(-e+e-)=(2.4 ±0.2stat± 0.4syst) × 10-4

  18. 2.6 A flash on  0 ChPT “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 4g 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

  19. 3. Results on scalar mesons. KLOE contribution to the understanding of the lowest mass scalars: f0(980), a0(980), (500) through radiative decays in pairs of pseudoscalars  Motivations: 1. f  |ss> scalar quark composition of f0(980), a0(980) 2. Search for evidence of (500)  Results presented here: 3.1 KLOE results on f0(980)pp 3.2 High statistics study of  3.3 Search for the decay K0K0 Mass (GeV/c2) f(1020) 1 a0(980) f0(980) k(800) s(500) 0 I=0 I=1/2 I=1 Talks by: S.Fiore, F.Nguyen (Light Meson Spectroscopy II)

  20. 3.1 Update of KLOE results on f0(980) KLOE observed the decay  f0(980) in and 00 channels: : Phys.Lett.B634 (2006) 148; : Phys.Lett.B537 (2002) 21; Eur. Phys.J. C49 (2006) 433; Large “unreducible” backgrounds for both channels: wp0 and rp0 for p0p0g; ISR, FSR and rp for p+p-g Extraction of the scalar amplitude  fit of the spectrum  parametrization of signal and background Dalitz plot f0(980) massspectrum

  21. Attempt to describe both spectra with a unique scalar amplitude. [Achasov and Kiselev, Phys.Rev.D73 (2006) 054029]: Scalar amplitude = f0(980) + s(600) + interference.  s(600) parameters and pp/KK scattering phases fixed (10 different parameter sets, see Eur. Phys.J. C49 (2006) 433)  free parameters: Mf0, gf0KK , gf0p+p- Preliminary results (uncertainties under evaluation) are encouraging: Comments: 1.The Kaon-Loop well describes the mass spectra; 2.The f0(980) is strongly coupled to the s quark: gf0KK > gf0p+p- 3.The scalar amplitude has a large low mass tail (m<600 MeV) that can be interpreted as due to the (600); In progress: combined fit with improved background amplitudes

  22. 3.2 High statistics study of  : the a0(980). “Pure” final state, dominance of a0(980) intermediate state • Selection of: • 1.  events with : fully neutral 5 events; • 2.  events with : 2tracks 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  0.10stat 0.20syst) 10-5 B.R.( )(2) = (7.19  0.17stat 0.24syst) 10-5 in good agreement, (part of the systematic errors are common). Error improvement: 9% (Phys.Lett.B536 (2002) 216) 3% (this result) • M() spectra • Combined fit of the spectra with a0 production parametrizations • (convoluted with efficiencies and resolutions)

  23. KL fit: points =data red =fitting curve (model  efficiency and resolution) The fit parameters (preliminary). Ratio BR()/BR()  BR(  ) contribution (KL) Kaon-Loop: (N.Achasov,A.V.Kiselev, Phys.Rev.D73(2006)054029)  Ma0, couplings ga0KKga0, phase  (NS) Breit-Wigner + polynominal “background”: (G.Isidori et al., JHEP0605 (2006) 049)  Ma0, couplings ga0ga0KK ga0

  24. 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 ga0KK~ 2 GeV and ga0KK / ga0 ~ 0.8  “conflict” with qqqq hypothesis; 2.2 Large values of BR( ) and of ga0 sizeable coupling with the (as for f0(980)) Other descriptions:  Unitarized Chiral Model [Palomar et al., Nucl.Phys.A729 (2003) 743]  KK molecule [Kalashnikova et al., Eur.Phys.J.A24 (2005) 437]  Linear Sigma Model [Bramon et al., Phys.Lett.B494 (2000) 221]

  25. 3.3 Search for the decay  KSKS In K0K0 the K0K0 pair is: in a J=0 state  = [|KSKS>-|KLKL>]/2; in a I=0,1 isospin state a0 and f0 contribute; Very small allowed phase space: 2MK < 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 MeV) • 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

  26. 4. Prospects. (talks by P.Moskal and D.Domenici (Future facilities)) DAFNE is testing now a new scheme to increase luminosity KLOE phase-2could 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 GeV is also considered (KLOE phase-3)  physics program extended to hadronic cross-section (g-2, em) baryon time-like form factors (DANTE proposal)  physics (,’,f0(980),a0(980) 2 widths) [see http://www.lnf.infn.it/lnfadmin/direzione/roadmap/roadmap.html F.Ambrosino et al., Eur.Phys.J. C50,729 (2007)]

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