KLOE results on hadron physics MENU07, Julich 11/09/2007 KLOE results on hadron physics Cesare Bini Università “La Sapienza” and INFN Roma Outline: The KLOE experiment Results on pseudoscalar mesons Results on scalar mesons Prospects

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. KLOE 2700 pb-1 2. DEAR (kaonic atoms) 100 pb-1 FINUDA (hypernuclei) 1100 pb-1 STATUS:  March 2006: end of KLOE data taking 2500 pb-1 on-peak  8 × 109 f decays 200 pb-1 off-peak (energy scan + 1 GeV run)  December 2006 - June 2007: FINUDA run  Now: machine tests and preparation of SIDDHARTA (kaonic atoms) run

Drift Chamber (He-IsoBut. 2m × 3m) 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) 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

2. Results on pseudoscalar mesons. The lowest mass pseudoscalar mesons (JPC=0-+) are accessible at a  - factory through the decays: B.R. Nev KLOE (2.5 fb-1) K+K- 0.49 3.7  109 K0K0 KSKL 0.33 2.5  109  1.3  10-2 9.7  107  1.2  10-3 9.0  106 ’ 6.2  10-5 4.6  105 Results presented here: 2.1 Precision measurement of the  mass 2.2 Improved measurement of the  - ’ mixing 2.3 Dynamics of  3 decays 2.4 Measurement of KS  2.5 Other analyses in progress (, -e+e-)

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 presented 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

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

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 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. C7, 271 (1999)

Constrain to the ’ gluonium content: 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 R.Escribano and J.Nadal (JHEP 0705,006,2007) reanalyze all V P and P V decays updating wavefunction overlaps parameters ==> no evidence of gluonium content Experimentally: improve (’), BR(’), ’measurements

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:   Dalitz plot analysis: 1.34 106 events   ”slope” analysis: 0.65 106 events

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. According to B.Borasoy and R.Nissler (Eur.Phys.J.A26 (2005) 383) it is difficult to accomodate such a small b value in a ChPT approach

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

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 value of M() (Dalitz plot contour) MC with M()=547.3 MC with M()=547.822 New result:  = -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 ChPT @ order p4 (G.D’Ambrosio, D.Espriu, Phys.Lett.B175 (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  0.13(stat) +0.03 -0.04(syst))10-6 Result compared to other experiments and theory

2.5 Others (2 flashes on other ongoing KLOE analyses)   +-e+e-: signal observed: 1500 events expected with 2.5 fb-1    0: ChPT “golden mode” 3 signal (only 1/5 of full statistics) Updated B.R. result soon with 15% statistical error signal confirmed in full data sample. Few % sensitivity on plane asymmetry (CP violation, D.Gao, Mod.Phys.Lett.A17 (2002) 1583)

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  S   (I=0)f0     (I=0) f0    (I=1) a0  K+K- (I=0,1) f0 a0  K0K0  (I=0,1) f0 a0 Mass (GeV/c2) f(1020) 1 f0(980) a0(980) k(800) Motivations: 1. f  |ss> scalar quark composition 2. Search for evidence of (500) s(500) Results presented here: 3.1 Review of KLOE results on f0(980) 3.2 High statistics study of (preliminary) 3.3 Search for the decay   K0K0 : I=0 I=1/2 I=1

3.1Review of KLOE results on f0(980) KLOE has 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; FB asymmetry Dalitz plot f0(980) mass spectrum Fit results: 1.The Kaon-Loop well describes the mass spectra; 2.The f0(980) is strongly coupled to the s quark: gf0KK > gf0p+p-, gf0is large 3.The scalar amplitude has a large low mass tail (m<600 MeV) that can be interpreted as due to the (500) (not clear results yet);

3.2 High statistics study of   : the a0(980). “Pure” final state, expected 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 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 two spectra with a0 production parametrizations (convoluted with efficiencies and resolutions)

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

1. Good consistency between sample 1 and 2: 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 hypothesys (not for f0(980)); 2.2 Large values of BR(  ) and of ga0 sizeable coupling with the  (as for f0(980)) Meson gM (GeV-1) 0  0.13   0.71 ´  0.75 a0(980)  1.6 f0(980) 1.2 – 2.7

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 can 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 : (Ldt = 1.4 fb-1) 1 event found; 0 expected background; BR(  KSKS)<1.810-8 90% CL

4. Prospects. The DAFNE team 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) The possibility to 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)]

Conclusions: Hadron Physics is an important part of the KLOE program; Many results have been obtained; Others are to come: full data sample to be analysed more channels not yet analysed

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