Recent KLOE results on Hadron Physics

1. 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

2. 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

3. The KLOE experiment 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 × 109f decays 200 pb-1 off-peak (energy scan + 1 GeV run)

4. 0-+ 1-- 0++ (1020) KK  a0(980)  f0(980)  '   r(770)   Direct decay Radiative decay p-emission  Physics at a f – factory: a window on the lowest mass mesons Sketch of the f decays: #events = Br.F. × 8 × 109  ~105h’, pp, hp

5. 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 p0p0p0CP 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

6. 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 (knot 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-quarkvs.2-quarkvs. KK molecule 1. a0(980) f0(980) k(800) s(500) 0. I=0 I=1/2 I=1

7. Scalar Mesons with KLOE •  f0(980)g  p+p-g  p0p0g  K+K-g [ 2m(K)~m(f0)~m(f) ] expectedBR ~ 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 signaland background;

8. (“trackmass”) pions muons Thep+p-ganalysis P.L.B 634 ,148 (2006) Event selection: 2 tracks withqt>45o; missing momentumqpp>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 electrons

9. 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 Ac Events data MC no f0 MC with f0 m(pp) (MeV)

10. 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)

11. Thep0p0ganalysis Event selection: 5 photons withqg>21o; no tracks; Kinematic fit  energy-momentum conservation; Kinematic fit p0masses: choice of the pairing.  4 ×105 events / 450 pb-1  analysis of Dalitz-plot 2 components in the Dalitz-plot

12. 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%

13. Fit results Comments:  s(500) is neededin KL fit[p(c2) ~ 10-4  14% !] (best s parameters are: M=462 MeV, G=300 MeV);  f0(980) parameters agree withp+p-ganalysis 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

14. Thehp0ganalysis Simultaneous analysis ofhggand hp+p-p0channels: 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

15. 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 p0p0Dalitz-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]

16. Pseudoscalar Mesons Large samples of p0, h and h’ through the radiative decay f  Pg  8 ×107h  9 ×106p0  4 ×105h’ List of the analyses done or in progress

17. 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 positionfrom large angle Bhabha scattering 3gDalitz-plot The p0 and the h peak are well defined p0 h Mass (MeV)

18. Results (still preliminary): The statistical uncertainty is ~negligible Systematic uncertainties from knowledge of s and vertex position (work in progress to reduce it) Thep0mass 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)

19. Measurement of the h – h’ mixing anglein p+p- 7g using similar h and h’ decay chains Method: measurement of Previous analysis: h’  p+p-hh  gg  p+p-3g h  p+p-p0p0  gg  p+p-3g This analysis: h’  p+p-hh  p0p0p0  p+p-7g h’  p0p0hh  p+p-p0  p+p-7g h  p0p0p0p0  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) hsignal (no bck) The systematic uncertainty is due to the uncertainty on the intermediate BRs

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

21. 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)

22. 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

23. Spare Slides

24. 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

25. 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) Providedsandkare there the scalars have an “Inverted Spectrum”

26. 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]

27. p+ g Kaon-loop No-structure f0,a0 p+ p- f0,a0 K+ f f K- g p- Definition of the relevant couplings (S=f0 or a0): S to fgfSg (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