1. European Physical Society International Europhysics Conference on High Energy Physics EPS July 17th-23rd 2003 Aachen, Germany Camilla Di Donato INFN Napoli for the KLOE Collaboration Rare  decays at KLOE

2. KLOE @ DA  NE DA  NE is an e+e- Collider at  resonance  s =1020 MeV ; DEAR E.m. calorimeter:   /E = 5.7% /  (E(GeV))  t = 54 ps/  (E(GeV))  50ps 98% of 4  Drift chamber:  p/p < 0.4%  xy  150  m ;  z  2 mm Quadrupol Calorimeter: Magnetic field: 0.5 T

3. KLOE data collection 1999 2.5 pb -1 machine and detector studies 2000 25 pb -1 (7.5x10 7  ) published results 2001 190 pb -1 (5.7x10 8  )  analysis in progress 2002 300 pb -1 (9.0x10 8  )  analysis in progress

4. Radiative  decays The analysis of 16 pb -1 from 2000 runs has produced the following publications:   Phys. Lett. B541 (2002), 45       Phys. Lett. B537 (2002), 21     Phys. Lett. B536 (2002), 209 The analysis of full statistic (2001/2002) is in progress

5. Radiative  decays Radiative decays:  P  and  S  Pseudoscalar mesons (J PC = 0 -+ )  (547) (I=0)  (958) (I=0) Scalar mesons (J PC = 0 ++ ) f 0 (980) (I=0) a 0 (980) (I=1)

6. Pseudoscalar mesons The mass eigenstates ,  are related to SU(3) octet- singlet  8,  1 through the mixing angle P Recent studies based on  PT and phenomenological analyses suggested a two mixing angle scenario In the quark flavour basis the two mixing angles are almost equal  mixing is described by only one parameter (  P )  -  - -  cos  P 1 |uu+dd  - sin  P |ss   2 -  - -  sin  P 1 |uu+dd  + cos  P |ss   2

7. Pseudoscalar mesons  P can be extracted from the ratio: (Bramon et al., Eur.Phys.J.C7(1999)) Br(  ) can probe the gluonic content of  - - -  X  1 |uu+dd  + Y  |ss  + Z  |glue   2 Br(  ) Br(  ) m s tg  V m sin 2  P p  p  msmmsm R= = cotg 2  P 1- 23 ; = 1.45

8. Br(  )/Br(  ) N(  ) = 120  12  5  tot (  ) = 23% N(  ) = 50210  220  tot (  ) = 37%  R = (4.70 ± 0.47 ± 0.31) x 10 -3 Using PDG value for Br(  ): Br(  ) = (6.10  0.61  0.43)  10 -5 Pseudoscalar mixing angle:  P = (41.8  1.7)  (flavor)  P = (-12.9  1.7)  (octet-singlet) F  =0.95 ( interference with e + e -  (  ) M  (MeV) Phys. Lett. B 541 (2002), 45 R = N    Br        Br(    ) N    Br      Br(   ) FF

9. Gluonic content of  a consistency check If we allow for a gluonic content Z  = 0  |Y  | = cos  P other constraints on X  and Y  from: (1)  /  (  0  (2)  /  (  0  X  + Y  = 0.94 (1) (2) +0.06 -0.09 22 - - -  X  1 |uu+dd  + Y  |ss  + Z  |glue   2

10. 2001 runs: 100 pb -1 M  (MeV) preliminary

11.     7  2000 data: Br(  ) = (7.05±0.50 )x10 -5 (first observation) 2000 2001 2002 E  + +E  - (MeV) dN/dE E  + +E  - (MeV) Ks      Kl        Ks       Kl        2000 preliminary +0.53 -0.46

12. Scalar mesons The structure of f 0 (980) a 0 (980) is not well defined; both BR(  S  ) and scalar mass spectra are sensitive to mesons’ nature Several hypothesis has been proposed: qq states qqqq states (Jaffe 1977) kk molecule (Weinstein and Isgur 1990) meson-meson scattering resonances in a chiral unitary approach (E.Oset) Models BR(  f 0  ) BR(  a 0  ) qq 5x10 -5 2x10 -5 qqqq 3x10 -4 2x10 -4 kk 10 -5 10 -5

13.  f    a    Decays with 5  final state  f 0  ; f 0  0  0  a 0  ; a 0  0  Decays with  +  - 5  final state  a 0  ; a 0  0  +  -  0 Decays with  +  -  final state  f 0  ; f 0  +  - first observation 340pb -1 2001/2

14.  0  0  - M  spectrum  0  0   3102 events; = 40% estimated backgr. at level ~20% Br(  0  0  )=(1.09  0.03  0.05)  10 -4 SND: (1.22  0.10  0.06)  10 -4 ; CMD-2: (1.08  0.17  0.09)  10 -4

15.  0  - M  spectrum  0  with   916 events; =32% estimated backgr. at level ~30% Br (  0  )=(8.51  0.51  0.57)  10 -5 SND: (8.8  1.4  0.9)  10 –5 ; CMD-2: (9.0  2.4  1.0)  10 –5  0  with  +  -  0  197 events; = 19% estimated backgr. 4  4 events Br(  0  )=(7.96  0.60  0.47)  10 -5 M  (MeV)

16. Fit to the M , M  spectra Kaon loop  (VMD) sigma(500) Kaon loop  (VMD) sigma(500)   00 00     00  00 k+k+ k-k-  a0a0      00 k+k+ k-k- 00 f0f0  The structure of f 0, a 0 states can be investigated by comparing the M , M  spectra to theoretical models. As a first step we have tried to fit our data with the kaon-loop model used for the CMD-2/SND data. Model :  f 0 , a 0  dominated by kaon loop f 0, a 0 propagator with finite width corrections (Achasov-Ivanchenko, Nucl.Phys.B315(1989))  + interference term parametrizations (Achasov-Gubin, Phys.Rev.D63(2001))  (500) : B-W with M  =478 MeV and   =324 MeV (Fermilab E791-Phys.Rev.Lett.86(2001)770) point-like coupling of  (500) to  (Gokalp,Yilmaz,Phys.Rev.D64(2001))

17. +-5+-5 55 Kaon loop model : fit results  contribution negligible adding the  (500) improves the fit (Large f 0 -  destructive interference at M  <700 MeV) g f0kk, g f0  is compatible with 4q hypothesis Simultaneous fit to both channels M a0 =984.8 MeV (PDG) fixed  contribution negligible Br(  a 0  0  )=(7.4  0.7)  10 -5 g a0kk, g a0  is not       

18. A first look at 2001 and 2002 data Much more statistics (x25) w.r.t. 2000 Good agreement between the three data sets (2000/2001/2002) M  (MeV) 2001+2002 data 2000 data

19. A first look at 2001/2002 data:      Re-analysis of 2001+2002 data: new approach The large statistics allows now to perform a Dalitz plot fit

20. A first look at :          soft   We also looked for the charged decay f 0 (980)      Huge background due to ISR e+e-       Interference with FSR photon detected at large angles (45°<  <135°) Fitting the spectrum with: - Signal f 0 (980) - Background (ISR, FSR) - Interference with FSR  Best results for destructive interference 340pb -1 2001+2002 data M  (MeV)

21. Conclusions and Outlooks First KLOE papers on  radiative decays published using data collected in 2000: Measurement of Br(  ) and of  P,  -  mixing angle in the quark flavor basis Measurement of Br(  0  0  ) and Br(  0  ) Analysis in progress on 2001+2002 events 16pb -1 (2000)  500pb -1 :more statistics, complete analysis of Dalitz plot content