Analysis of the dynamics of the Analysis of the dynamics of the decay decay + + - - o o Referees report Referees report Mario Antonelli, Luca Passalacqua KLOE general meeting 10-10- 2002
Jan 19, 2016
Analysis of the dynamics of the Analysis of the dynamics of the decay decay ++--oo
Referees reportReferees report
Mario Antonelli, Luca Passalacqua
KLOE general meeting 10-10-2002
General:• competitive results + 2000 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 biasReferees 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
50o<<130o
Momentum bias
• the wire droop
is not taken into account in the present track reconstruction algorithm bias on the momentum ?
X-Y view
w ~ 200m Not in scale
Sagitta (s)
pt=pt2/(0.3BLt
2)8 s
error on the wire poistion s pt
sdroop ~
R-Z view
100 m 300 keV @ p=500MeV
Momentum biasCharge dependent effect:
X-Y view
+ / –s for + / - charge
X-Y view
dependent effect
w
s
effective bias
Parallel component
to the sagitta
s=w cos
Momentum bias
R-Z viewdependent effect
Only relative positions are important
If wires have same droops w no effect at =90o
sw
X-Z view =0
sw
s
At small angle
Momentum bias
w is not a constantWIRE SAGITTA vs. LAYER #
100
150
200
250
300
350
400
450
0 20 40 60 80 100 120
LAYER #
SA
GIT
TA
(m
icro
n)
SAGW micron
SAGAl micron
effect at =90o 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(-
) (M
eV
)
50o<<130o
check the model at low angles (large effects are expected)
results
Use bhabha
P(+
)-P
(-)
(MeV
)
35o>>155o
A bit asymmetric…under studyTilted 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 witho kinetic energy outof boundaries?
Fit stability checked varying cuts on variables sensitive to ISR