Experimental Measurement of the F meson radiative decays into scalars and pseudoscalars mesons The KLOE Coll. presented by Camilla Di Donato I.N.F.N. Naples International Conference on the Structure and Interactions of the Photon

KLOE data collected 1999 run : 2.5 pb-1 machine and detector studies 7.5x107 f published results 2001 run: 190 pb-1 5.7x108 f analysis in progress 2002 run: 300 pb-1 9.0x108 f

KLOE Drift chamber: dp/p < 0.4% xy150 m ; z2 mm E.m. calorimeter: sE/E = 5.4% / (E(GeV)) st = 55 ps/(E(GeV))40 ps 98% of 4 Magnetic field: 0.52 T

F radiative decays Analysis of 2000 data:  Ldt = 16 pb-1 F  hg / hg Phys. Lett. B541 (2002), 45 F  p0 p0 g Phys. Lett. B537 (2002), 21 F  h p0 g Phys. Lett. B537 (2002), 209

F radiative decays Pseudoscalar mesons (JPC= 0-+) h (547) (I=0) h (958) (I=0) Scalar mesons (JPC= 0++) f0(980) (I=0) a0(980) (I=1)

 /  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)

 /  Br() can probe the gluonic content of  P can be extracted from the ratio (Bramon et al., Eur.Phys.J.C7(1999)) : Br() can probe the gluonic content of 

 /  Decays with +- 3 final state: ;+-0;0 Br  310-3  ; +- ;  Br  210-5 Background from +-0 and KLKS (with KL decaying near the IP) Analysis cut: 1 vertex in IR with 2 tracks 3 prompt  (E>10 MeV, |cos|<0.93) Constrained kinematic fit topological cuts on the energy of particles tot () = 37 % tot () = 23 %  ´

 /  R = Br()/Br() M (MeV) Main background is  Selection: elliptic cut in the plane of the two most energetic photons Phys. Lett. B 541 (2002), 45 M (MeV) F =0.95 (interference with e+e-( ) N() = 120 12 5 events; N() = 50210  220 events R = Br()/Br()

 /  Using PDG value for Br(): Pseudoscalar mixing angle: P = (41.8  1.7) (flavor)  P = (-12.9 1.7) (octet-singlet) Gluonic content of : Consistency check: if Z=0  |Y|=cosP other constraints on X and Y from: (1) /(0 (2) /(0 (1) (2)

 /  M (MeV) 100 pb-1 (2001)

p+p-7 preliminary N() = 153 12 2000 2001 2002 Selection: 2000 2001 2002 Ep++Ep- (MeV) dN/dE dN/dE Eg (MeV) Ks  p0 p0 Kl  p+p-p0 Ks  p+p-g Kl  p0p0p0 data preliminary Ks  p0 p0 Kl  p+p-p0 Ks  p+p-g Kl  p0p0p0 data Ep++Ep- (MeV) N() = 153 12 Br() = (7.05±0.50+0.53/-0.46)x10-5

f f0 (980) g / a0 (980) g The scalar mesons f0 (980) a0 (980) are not easily interpreted as qq states Jaffe(1977) suggested qqqq states Weinstein, Isgur (1990) suggested KK molecule Both BR and scalar mass spectra are sensitive to nature Br(f0) 5  10-5 3  10-4 10-5 Br(a0) 2  10-5 2  10-4 10-5

Models Predictions from Achasov-Ivanchenko, Nucl.Phys.B315(1989) f0 model g2f0KK/(4) 2.3 0.15 0.3 (GeV2) (=g2a0KK/4) (=g2a0KK/4) (=2g2a0KK/4) gf0 /gf0KK 0.3—0.5 2 0.5 Br(00)104 ~ 1 ~ 0.15 ~ 0.2 a0 model g2a0KK/(4) 2.3 0.15 (GeV2) (=g2f0KK/4) (=g2f0KK/4) ga0/ga0KK 0.91 1.53 Br( a0)104 ~ 2 ~ 0.2

Scalar mesons (JPC= 0++) f0(980) (I=0) f000+- a0(980) (I=1) a0 Studied decays (data sample: 16 pb-1 from the 2000 data,~5107) f0 ; f000  5  final state a0 ; a00  (39%)  5  a0 ; a00 +-0 (23%)  2 ch. tracks +5  first observation  Previous meas. at VEPP2M

5 g final states cross sect.(nb) Signal: 00 (f0 ; (500) ; 00) ~ 0.35  00  0 0 ( a0 ;  00) ~ 0.1   Background: e+e-0 00 ~ 0.5 3 (with accidental ’s) (~17)  000 (with 2 lost) (~14) Sample selection: exactly 5 prompt photons E > 7 MeV |cos| < 0.93 to avoid the quadrupole region 5Ei > 700 MeV to reject KLKS neutrals

00 Constrained kinematic fit to improve resolutions Photon pairing |M - M| < 5(M) Reject events with: |M - M| < 3(M)  3102 events <> = 40% Estimated backgr. (~20%) e+e-0 00 33924 0 16616  000 15912 1+cos2 0  

Fit to M spectrum gKK gf0KK gf0 Model : radiative g gKK gf0KK gf0 0 K+ K- Model : 1) f0 dominated by kaon loop (Achasov-Ivanchenko, Nucl.Phys.B315(1989)) 2) f0 propagator with finite width corrections 3) (500) B-W with M=478 MeV and =324 MeV (Fermilab E791-Phys.Rev.Lett.86(2001)770) 4) point-like coupling of (500) to  (Gokalp,Yilmaz,Phys.Rev.D64(2001)) 5)  + interference term parameterizations from Achasov-Gubin, (Phys.Rev.D63(2001)) Two fits: Fit A : | (f0) + (00 )|2 Fit B : | (f0) + () + (00 )|2 Free parameters: Mf0, g2f0KK, g2f0/g2f0KK, g and (gg)2

Fit results A B 2/ndf 109.5/33 43.2/32 Mf0 (MeV) 9624 973 1 g2f0KK/(4) 1.290.14 2.79 0.12 (GeV2) g2f0KK/g2f0 3.220.29 4.000.14 g — 0.060 0.008 (  contribution negligible ) Br(00) = (1.09  0.03  0.05)  10-4 (Fit B) (SND: (1.220.10 0.06)  10-4 ; CMD-2: (1.080.170.09)  10-4)  Large f0- destructive interference at M < 700 MeV Br(f0)= (4.47  0.21)  10-4

0 (with ) Events Constrained kinematic fit to improve resolutions Photon pairing: (1) 00 ; (2) 0  reject 00 events M  < 760 MeV (reject f0 events) |M - M| < 3(M)  916 events <> = 32 % M (MeV/c2) Events cos Data —MC Estimated backgr.: (~30%) e+e-0 00 546 00 15216  000 9810   52 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 +-5 (+-0) No background with the same final state Backgr.: 2 Tracks + 3/4 photons (e+e-0 ; +-0) ( ; +-0) 2 Tracks + 6 photons (KSKL+-000) 1 vertex in IR with 2 tracks 5 prompt  (E>10 MeV, |cos|<0.93) Constrained kinematic fit M+-< 425 MeV (reject KS  p+p-)  197 events <>=19% estimated backgr. 44 events Br(0)=(7.960.600.47) 10-5

Fit to Mh spectrum Same model as for the f0 (kaon loop) Combined fit, relative normalization fixed to Br()/Br(+-0) Free parameters: g2a0KK, ga0/ga0KK and Br(000) Ma0=984.8 MeV (PDG) fixed 2/ndf 27.2/25 g2a0KK/(4) (GeV2) 0.40  0.04 ga0/ga0KK 1.35  0.09 Br(000) (0.5  0.5)  10-5 5 +-5 Br(a00)= (7.4  0.7)  10-5

Summary of fit results f0 parameters are compatible with model Comparison with predictions from Achasov-Ivanchenko, Nucl.Phys.B315(1989) KLOE f0 model g2f0KK/(4) 2.790.12 2.3 0.15 0.3 (GeV2) (=g2a0KK/4) (=g2a0KK/4) (=2g2a0KK/4) gf0 /gf0KK 0.500.01 0.3—0.5 2 0.5 Br(00)104 1.090.07 ~ 1 ~ 0.15 ~ 0.2 a0 model g2a0KK/(4) 0.400.04 2.3 0.15 (GeV2) (=g2f0KK/4) (=g2f0KK/4) ga0/ga0KK 1.350.09 0.91 1.53 Br( a0)104 0.740.07 ~ 2 ~ 0.2 f0 parameters are compatible with model a0 parameters seem not compatible with model

f f0(980) g / a0(980) g M (MeV) 2001+2002 data 2000 data Phys. Lett. B 537 (2002), 21 M0 (MeV) Phys. Lett. B 536 (2002), 209

Conclusions First KLOE published papers on f radiative decays, 2000 events: Br() = (6.100.610.43)10-5 P = (41.8  1.7) (flavor) Br(00) = (1.09  0.03  0.05)  10-4 Br(f0) = (4.47  0.21)  10-4 Br(a0) = (7.4  0.7)  10-5 Analysis in progress on 2001+2002 events  500pb-1: more statistic and models with more free parameters

====================================================== Author : KLOE Collab. (Speaker: Camilla Di Donato) Type : Experimental Measurement of the Phi meson radiative decays into scalars and pseudoscalars mesons. The Kloe experiment has measured the radiative decays of the Phi meson into pi0, eta and eta'(958); these measurements are relevant to assess the mixing in the pseudoscalar nonet as well as to evaluate the gluon content in the eta'(958). Moreover also the radiative decays into pi0 pi0 gamma and eta pi0 gamma have been measured. These decays are dominated by the final states f0(980) and a0(980). The measurement of the branching ratios and of the pi0-pi0 or eta-pi0 invariant mass spectrum helps to understand the controversial nature of the above scalar mesons. ==================================================