Recent KLOE results on Hadron Physics QNP06 – Madrid – 09/06/06 Recent KLOE results on Hadron Physics Cesare Bini Universita’ “La Sapienza” and INFN Roma Outline: The KLOE experiment at DAFNE Results on Scalar Mesons Results on Pseudoscalar Mesons Prospects for e+e- at Frascati

DAFNE: the Frascati f - factory e+e- collider with 2 separate rings: s = Mf= 1019.4 MeV 2 interaction regions 1. KLOE 2. DEAR (kaonic atoms) FINUDA (hypernuclei) Luminosity was delivered to the 3 experiments KLOE 2700 pb-1 FINUDA 250 pb-1 DEAR 100 pb-1 Luminosity has increased up to 1.5×1032 cm-2s-1

The KLOE experiment Drift Chamber (He-IsoBut. 2m × 3m) The 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) 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)

Physics at a f – factory: a window on the lowest mass mesons Sketch of the f decays: Main decay channels Branching fraction  K+K- 49.2 % KSKL 34.0 %  rp + p+p-p0 15.3 %  hg 1.301 %  p0g 0.125 %  h’g 6.2 × 10-5  p0p0g 1.1 × 10-4  hp0g 8.3 × 10-5 + “radiative return” to p+p- (1020)  a0(980) f0(980)  ' KK  0-+ 1-- 0++  r(770) Direct decay Radiative decay p-emission #events = Br.F. × 8 × 109  ~105 h’, pp, hp

Overview of KLOE physics (1) Kaon physics: several “fundamental physics” items: Extraction of the Vus element of the CKM matrix from 5 semi-leptonic decays of neutral and charged kaons  test of CKM Unitarity  CPT tests: first measurement of KS semi-leptonic asimmetry Kaon interferometry in p+p-p+p- final states:  bounds on quantum decoherence + CPT violation Reduced upper bound on KS  p0p0p0 CP violating decay Precision measurement of KS  p+p- / KS  p0p0 Measurement of KL and KS  gg  ChPT test ~ 450 pb-1 analysed = 20 × previous analyses (2) Hadron physics:  Scalar Mesons ( a0(980), f0(980) s(500) )  Pseudoscalar Mesons ( p0, h, h’ )  Vector Mesons ( properties of r(770), w(780) ) (3) Measurement of the Hadronic Cross-Section below 1 GeV  hadronic corrections to g-2

How a f-factory can contribute to the understanding of Scalar Mesons How a f-factory can contribute to the understanding of the scalar mesons Mass (GeV/c2) f(1020) Scalar Mesons Spectroscopy: f0(980), s(500) and a0(980) are accessible (k not accessible) through f  Sg; Questions: 1. Is s(500) needed to describe the mass spectra ? 2. “couplings”of f0(980) and a0(980) to f  |ss> and to KK, pp and hp.  4-quark vs. 2-quark vs. KK molecule 1. f0(980) a0(980) k(800) s(500) 0. I=0 I=1/2 I=1

Scalar Mesons with KLOE  f0(980)g  p+p-g  p0p0g  K+K-g [ 2m(K)~m(f0)~m(f) ]  expected BR ~ 10-6  K0K0g “ “ ~ 10-8  a0(980)g  hp0g  K+K-g expected BR ~ 10-6  K0K0g  “ ~ 10-8  s(500)g  p+p-g  p0p0g General Comments:  fits of mass spectra are needed to extract the signals: this requires a parametrization for the signal shape;  the unreducible background is not fully known: a parametrization is required and some parameters have to be determined from the data themselves;  sizeable interferences between signal and background;

The p+p-g analysis P.L.B 634 ,148 (2006) Event selection: 2 tracks with qt>45o; missing momentum qpp>45o (large angle) Each track is pion-like (tracking, ToF and Shower shape) 1 photon matching the missing momentum  6.7 ×105 events / 350 pb-1 Particle identification: p vs. e and m (Likelihood: Tof and Shower shape) pions, muons (“trackmass”) muons pions electrons

The p+p-g final state is dominated by: Initial State Radiation Final State Radiation The f0(980) is observed as a “bump” in: ds/dm(pp) vs. m(pp) Ac vs. m(pp) -- Forward-Backward asymmetry f0(980) signal Events Ac data MC no f0 MC with f0 m(pp) (MeV)

 “Large” coupling to the f Fit of the mass spectrum using 2 different models for the scalar amplitude:  Kaon-Loop model [N.N.Achasov et al. ] mf0, gf0p+p-, gf0K+K-,  “No Structure” model [G.Isidori et al. ] mf0, gf0p+p-, gf0K+K-, gff0g, b0,b1 Free parameters: scalar amplitude + background An acceptable fit is obtained with both models: P(c2)(KL)=4.2% P(c2)(NS)=4.4% Mass values ok  gf0K+K-> gf0p+p-  “Large” coupling to the f B.R.(f  f0(980)g  p+p-g) = 2.1  2.4 × 10-4 (from integral of |Amplitude|2)

The p0p0g analysis Event selection: 5 photons with qg>21o ; no tracks; Kinematic fit  energy-momentum conservation; Kinematic fit  p0 masses: choice of the pairing.  4 ×105 events / 450 pb-1  analysis of Dalitz-plot 2 components in the Dalitz-plot

Fit of the Dalitz-plot (without rejecting wp0) using the same 2 models:  Improved Kaon-Loop model (introducing the fs(500)g)  “No Structure” model Parameters: mass and couplings ( mf0, gf0p+p-, gf0K+K-, gff0g) + background The s(500) parameters are fixed. The fit is repeated by changing them 2-dim fit shown slice bt slice. A good fit is obtained with both models: P(c2)(KL)=14% P(c2)(NS)= 4%

Fit results f0(980) param. NS model KL model mf0 (MeV) 981 ÷ 987 976 ÷ 987 gffg (GeV-1) 2.5 ÷ 2.7 - gfp+p- (GeV) 1.3 ÷ 1.4 1.4 ÷ 2.0 gfKK (GeV) 0.1 ÷ 1.0 3.3 ÷ 5.0 R=g2fKK /g2fp+p- 0. ÷ 0.9 3.0 ÷ 7.3 Comments:  s(500) is needed in KL fit [p(c2) ~ 10-4  14% !] (best s parameters are: M=462 MeV, G=300 MeV);  f0(980) parameters agree with p+p-g analysis KL fit again R > 1 (gf0KK > gf0p+p-);  NS fit gives large gff0g but R<1 (??);  BR extracted:  integral of |scalar amplitude|2 BR( p0p0g) ~ 1/2 × BR(p+p-g): neglecting KK, we add the 2 BRs  BR(f  f0(980)g) = (3.1 ÷ 3.5) × 10-4  G(f  f0(980)g) = 1.2 ÷ 1.6 keV

The hp0g analysis Simultaneous analysis of hgg and hp+p-p0 channels: Pts. = data 450 pb-1 = 20 × published results, hist = KL fit The spectra are dominated by the a0 production (negligible unreducible backgrounds). Work in progress, results soon

Scalar Mesons: Summary and Outlook Complete analysis of f  f0(980)g with f0(980)  p+p- and p0p0  good description of the scalar amplitude with KL model:  large couplings to Kaons: hint of a large s-quark content  s(500) is still required to describe the p0p0 Dalitz-plot  NS fit suggests large coupling of f0(980) to the f 2) Work in progress to:  make a combined analysis of f0(980)  p+p- and p0p0  complete the analysis of f  a0(980)g with a0(980)  hp0  study the decay chain f  [f0(980)+a0(980)]g  KKg (expected sensitivity down to 10-8) 3) Further studies:  search for e+e-  e+e-p0p0 events (gg  p0p0 ) using the run @ s = 1 GeV (off-peak = less background); search for the s(500) [F.Nguyen et al. 2005]

Pseudoscalar Mesons  9 ×106 p0  4 ×105 h’ Large samples of p0, h and h’ through the radiative decay f  Pg  8 ×107 h  9 ×106 p0  4 ×105 h’ List of the analyses done or in progress Measurement of the h (and p0) masses  this talk Measurement of the h – h’ mixing angle in p+p- 3g Phys.Lett.B541 (2002) 45 Measurement of the h – h’ mixing angle in p+p- 7g Dynamic of the decay h  p+p-p0 AIP:Conf.Proc.814:463,2006 Dynamic of the decay h  p0p0p0 Measurement of the BR(h  p0gg) Upper limit on the C-violating decay h  ggg Phys.Lett.B591 (2004) 49 Upper limit on the P(CP)-violating decay h  p+p- Phys.Lett.B606 (2005) 276 Study of the decay h  p+p-e+e- in progress Upper limit on the P(CP)-violating decay h  p0p0

Measurement of the h (and p0) masses 2 recent measurements done with different techniques: GEM (COSY) p+d  3He+h  M(h)=(547311 ± 28 ± 32) keV/c2 (missing mass technique) NA48 (CERN) p-+p n+h  M(h)=(547843 ± 30 ± 41) keV/c2 (h  3p0 reconstruction) 8 s discrepancy: dM(h)=(532 ± 41 ± 52) keV/c2 (errors added in quadrature) KLOE: ;  check with 0; 0 Technique: kinematic fit mostly based on photon positions and timing;  energy-momentum and vertex position from large angle Bhabha scattering 3g Dalitz-plot The p0 and the h peak are well defined p0 h Mass (MeV)

Results (still preliminary): The statistical uncertainty is ~negligible Systematic uncertainties from knowledge of s and vertex position (work in progress to reduce it) The p0 mass is well in agreement with PDG value M(p0) = ( 134990  6stat  30syst ) keV M(p0)PDG = ( 134976.6  0.6 ) keV The h mass is in agreement with NA48 and in disagreement with GEM M(h) = ( 547822  5stat  69syst ) keV KLOE NA48 GEM (see Kirillov @ QNP06) h mass (MeV)

Measurement of the h – h’ mixing angle in p+p- 7g Method: measurement of using similar h and h’ decay chains Previous analysis: h’  p+p-h h  gg  p+p-3g h  p+p-p0 p0  gg  p+p-3g This analysis: h’  p+p-h h  p0p0p0  p+p-7g h’  p0p0h h  p+p-p0  p+p-7g h  p0p0p0 p0  gg  7g 427 pb-1 2001/2002 data N(hg) = 1665000  1300 (no bck) N(p+p-7g’s) = 375060 (Nbckg= 345)  N(h´g) = 3405 ± 61stat ± 28syst h’ signal (~10% bck) h signal (no bck) The systematic uncertainty is due to the uncertainty on the intermediate BRs

Pseudoscalar mixing angle: extracted using the parametrisation [A.Bramon et al. 1999] Mixing angle (2) Analysis of h’ gluonic content: [E.Kuo, 2001] Before KLOE results Including new KLOE result X2+Y2 = 0.93 ± 0.06

Prospects for e+e- physics at Frascati Short term program:  New FINUDA Run 2006 – 2007 previous statistics × 5  SIDDHARTA Run 2007 – 2008 upgraded version of DEAR (see C.Curceanu talk @ QNP06)  ??? > 2009 Discussions are open in the laboratory about a possible continuation of a low-energy e+e- program Present project == DANAE (not approved yet):  higher luminosity f – factory (L~1033 cm-2s-1)  energy scan: √s = 1 ÷ 2.5 GeV (L~1032 cm-2s-1)

 Kaon physics + h / h’ physics @ f AMADEUS 3 Expressions of Interest have been presented: KLOE2  Kaon physics + h / h’ physics @ f  gg physics + hadronic cross-section up to 2.5 GeV AMADEUS  deeply bound hypernuclei @ f DANTE  baryon time-like form factors (√s > 1.9 GeV) Waiting for the final decision of the laboratory. Any contribution is welcome ! http://www.lnf.infn.it/lnfadmin/roadmap/roadmap.html

Spare Slides

Scalar Mesons Renewed interest after B-factory results: new scalar meson “zoology” above 2.3 GeV  reconsider the low mass spectrum A 0++ meson arises from a qq pair in a triplet spin state (S=1) and P-wave (L=1) Assuming 2 quarks interacting by a single gluon exchange, other configurations are found [Jaffe 1977]:  Color triplet diquarks and anti-diquarks Attractive interaction between diquark and anti-diquark giving a color singlet  it is possible to build up 4-quarks scalar meson

Provided s and k are there Analysis of the mass spectra of the lowest mass mesons Pseudoscalar multi-plet Vector multi-plet Scalar multi-plet: s(500), k(700), f0(980), a0(980) Provided s and k are there the scalars have an “Inverted Spectrum”

Inverted Mass spectrum  hint of a 4q picture Building Rule: Mass Q=0 Q=0 Q=1 Q=-1 (the f0(980) and a0(980)) add 2 Quarks s Q=0 Q=1 Q=0 Q=-1 (the k(800)) add 1 Quark s I3=0 Q=0 (the s(500)) 2 important consequences: if 4q hypothesis is correct  the s(500) and the k(800) have to be firmly established  the s-quark content of f0 and a0 should be sizeable ( f0 and a0 couplings with f (ss) and with kaons [N.N.Achasov and V.Ivanchenko 1989]

Definition of the relevant couplings (S=f0 or a0): S to f gfSg (GeV-1) S to kaons gSKK=gSK+K-=gSK0K0 (GeV) f0 to pp (I=0) gf0pp=√3/2 gf0p+p-=√3 gf0p0p0 (GeV) a0 to hp (I=1) ga0hp (GeV) Coupling ratio Rf0=(gf0K+K-/ gf0p+p-)2 Ra0=(ga0K+K-/ ga0hp)2 K+ K- p+ p- g Kaon-loop No-structure f0,a0 f