Analysis of the dynamics of the decay  +  -  o Referees report Mario Antonelli, Luca Passalacqua KLOE general meeting

General: competitive results data  KLOE note soon  draft Analysis is in a good shape: relevant detector effects taken into account several checks DATA-MC systematic uncertainties evaluation robustness of the fit Main questions: bias on momentum measurement ISR not taken into account Detailed description in the KLOE MEMO 274 Comments

Momentum bias difference in measured momenta between negative and positive charged particles observed in the control samples:     and     events P(+)-P(-) (MeV)  NOW: main systematic for  Ms mesaurements 0.5 MeV ONLY the AVERAGE enter in  (  Ms) Profiles + lab frame

Momentum bias Referees comment: find source(s) of the effect  correct measured momenta (use control sample) verify consistency with  o mass systemaitcs from uncertainties on correction Closer look to the effect:  rest of frame + use gaussian fits to slides P(+)-P(-) (MeV)  ~ 280 KeV average slides +  frame 50 o <  <130 o

Momentum bias the wire droop is not taken into account in the present track reconstruction algorithm bias on the momentum ? X-Y view  w ~ 200  mNot in scale Sagitta (s)  p t =p t 2 /(0.3BL t 2 )8  s error on the wire poistion ss ptpt ssdroop ~ R-Z view 100  m 300 p=500MeV

Momentum bias Charge dependent effect: X-Y view + / –  s for + / - charge X-Y view   dependent effect   ww ss effective bias Parallel component to the sagitta  s=  w cos 

Momentum bias R-Z view   dependent effect Only relative positions are important  If wires have same droops  w no effect at  =90 o  s  w X-Z view  =0  s  w  s  At small angle

Momentum bias  w is not a constant effect at  =90 o expected (and observed)

Momentum bias use a toy model to verify consistency with data linear droop vs z evaluate average of effective  s:  dependencies and differences in  w(0) vs R taken into account curvature effect on effective  s also considered z  w(0) Not negligible R~1 m  dependence (  s) on the wire

Results P(+)-P(-) (MeV)  50 o <  <130 o check the model at low angles (large effects are expected)

results Use bhabha P(+)-P(-) (MeV)  35 o >  >155 o A bit asymmetric… under study Tilted plates?

ISR effects? Initial state radiation not taken into account in the fit  o E,P evaluated from missing E,P using knowledge of W Some event with  o kinetic energy out of boundaries? Fit stability checked varying cuts on variables sensitive to ISR