European Physical SocietyInternational Europhysics Conference on High Energy Physics

EPS July 17th-23rd 2003 Aachen, Germany

Camilla Di Donato INFN Napolifor the KLOE Collaboration

Rare decays at KLOE

KLOE @ DANE DANE 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%xy150 m ; z2 mm

Quadrupol Calorimeter:

Magnetic field: 0.5 T

KLOE data collection

1999 2.5 pb-1 machine and detector studies2000 25 pb-1 (7.5x107 ) published results

2001 190 pb-1 (5.7x108 ) analysis in progress

2002 300 pb-1 (9.0x108 ) analysis in progress

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

Radiative decays

Radiative decays: Pand S

• Pseudoscalar mesons (JPC= 0-+)

(547) (I=0) (958) (I=0)

• Scalar mesons (JPC= 0++)

f0(980) (I=0) a0(980) (I=1)

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)- - -

cosP 1 |uu+dd - sinP |ss 2 - - -sinP 1 |uu+dd + cosP |ss 2

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()

ms tg V

m sin 2P

p

p

ms

mR= = cotg2P 1-

2 3

; = 1.45

Br()/Br()

N() = 120125 tot() = 23% N() = 50210220 tot () = 37% R = (4.70 ± 0.47 ± 0.31) x10-3

• Using PDG value for Br():

Br() =(6.100.610.43)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 =NBr Br( )NBr Br( )

F

Gluonic content of a consistency check

• If we allow for a gluonic content

Z = 0 |Y| = cosP

other constraints on X and Y from:

(1) /(0

(2) /(0

X + Y = 0.94 (1)

(2)

+0.06-0.09 2 2

- - - X 1 |uu+dd + Y |ss + Z |glue 2

2001 runs: 100 pb-1

M (MeV)

preliminary

7

2000 data: Br() = (7.05±0.50 )x10-5

(first observation)

200020012002

E++E- (MeV)

dN/d

E

E++E- (MeV)

Ks

Kl

Ks Kl

2000

preliminary+0.53

-0.46

Scalar mesonsThe structure of f0 (980) a0 (980) is not well defined; both BR( S) and scalar mass spectra are sensitive to mesons’ natureSeveral 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( f0) BR( a0) qq 5x10-5 2x10-5

qqqq 3x10-4 2x10-4

kk 10-5 10-5

fa

Decays with 5 final statef0 ; f000

a0 ; a00

Decays with +- 5 final statea0 ; a00 +-0

Decays with +- final statef0 ; f0+-

first observation

340pb-1 2001/2

00 - M spectrum

00 3102 events; <>= 40%

estimated backgr. at level ~20%

Br(00)=(1.09 0.03 0.05) 10-4

SND: (1.220.10 0.06) 10-4 ; CMD-2: (1.080.170.09) 10-4

0 - M spectrum

0 with 916 events; <>=32% estimated backgr. at level ~30%

Br(0)=(8.510.510.57)10-5

SND: (8.8 1.40.9) 10 –5; CMD-2: (9.0 2.41.0) 10 –5

0 with +-0

197 events; <>= 19%estimated backgr. 44 events

Br(0)=(7.960.600.47)10-5

M(MeV)

Fit to the M, M spectra

Kaon loop Kaon loop (VMD) sigma(500) (VMD) sigma(500)

0

0

0

0k+

k-

a0

0k+

k- 0

f0

The structure of f0, a0 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 : f0, a0 dominated by kaon loop f0 , a0 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))

+-5

5

Kaon loop model : fit results

contribution negligible • adding the (500)

improves the fit (Large f0- destructive interference at M<700 MeV)

• gf0kk, gf0 is compatible with 4q hypothesis

Simultaneous fit to both channels

Ma0=984.8 MeV (PDG) fixed

contribution negligible

• Br(a00)=(7.40.7)10-5

• ga0kk, ga0 is not

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 data2000 data

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

A first look at : soft

• We also looked for the charged decay f0(980)

• Huge background due to ISR e+e- • Interference with FSR• photon detected at large angles (45°< <135°)

Fitting the spectrum with: - Signal f0 (980) - Background (ISR, FSR) - Interference with FSR Best results for destructive interference

340pb-1

2001+2002 data

M(MeV)

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(00) and Br(0)

• Analysis in progress on 2001+2002 events

16pb-1 (2000) 500pb-1:more statistics, complete analysis of Dalitz plot content