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
Jan 20, 2018
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