Precision measurement of the total hadronic cross-section with CMD-2 at VEPP-2M e+e- collider. E. Solodov. Budker Institure of Nuclear Physics (Novosibirsk, Russia) CMD-2 Collaboration. ICHEP – 2004 Beijin, China, August 16-22, 2004. Outline. VEPP-2M and available data
Precision measurement of the total hadronic cross-section with CMD-2 at VEPP-2M e+e- collider
Budker Institure of Nuclear Physics (Novosibirsk, Russia)
ICHEP – 2004
Beijin, China, August 16-22, 2004
R(s) is defined as:
e+e- 2, 3, 4, KK, ..
e+e- , ,
Still a lot of data to analyzed !
Total hadronic cross-section measured by CMD-2 and SND
All modes except 2
Formfactor is measured to better precision than L
Definition of (e+e-hadrons) depends on the application
Initial and final state radiation
4 separate scans over 5 years, >1 million events, 100k published
Syst. Errors are under study
Ready for publication
Systematic error 5%
CMD-2/SND discrepancy recently resolved
Systematic error 3%
Br(w hg) = ( 4.9 +2.8-2.2 0.4)10-4
Br(r hg) = ( 2.9 +1.5-1.3 0.3)10-4
Br(f hg) = 1.355 0.014 0.063 %
e+e- w,r,f p0g
w’ , w” ?
Br(w p0g) = 9.46 0.17 0.57 %
Br(r p0g) = ( 4.2 +1.0-0.9 0.4)10-4
Br(f p0g) = (1.214+0.045-0.036 0.061) 10-3
Using data collected with CMD-2 detector in 720-840 MeV c.m.
energy range the branching fraction of the conversion decay was
The upper limits on the branching fractions of the
following decays have been set for the first time:
Br(r e+e-p0) < 2.210-5 (90% CL);
Br(r e+e-h) < 1.510-5 (90% CL);
Br(w e+e-h) < 2.310-5 (90% CL);
Under construction. Data taking is expected to start in 2006-2007.
Lxe calorimeter for CMD-3
Uncertainty of the hadronic contribution to a , 10-10