c. di donato and ilaria villella i.n.f.n. and universita’ di napoli
DESCRIPTION
f Radiative decay meeting April 17th 2003. fhgp + p - gg. C. Di Donato and Ilaria Villella I.N.F.N. and Universita’ di Napoli. Why h p + p - g. PDG’02: BR( h p + p - g ) = (4.68±0.11)x10 -2 KLOE: 500pb -1 5x10 5 events ( e selection ~50%) BR measurement error: 0.2x10 -4 - PowerPoint PPT PresentationTRANSCRIPT
C. Di Donato and Ilaria VillellaI.N.F.N. and Universita’ di Napoli
Radiative decay meeting
April 17th 2003
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 2
Why Why
• PDG’02: BR() = (4.68±0.11)x10-2
• KLOE: 500pb-1 5x105 events (selection~50%)
• BR measurement error: 0.2x10-4
• Study of |M|2 (Gormley et al. P.R.D2(1970),501 7250 events) :
¤ simple gauge-invariant matrix element |M|2~q2k2sin2
¤different theoretical model include the effect of a final-state interaction assuming that the dipion phase shift is dominated by the meson;
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 3
Signal and BackgroundSignal and Background
(b)
• Signal decay 1.84 x10-3
•Background decay S/B
0.44 4 x 10-3
e+e- 7.66x10-6 240
8.717x10-3
0.2
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 4
Signal: Signal:
Final State: MC Signal Production: 5x104 events
Topological cut:• 2 prompt photons |tcl-lcl/c| < 5t;• 1 charged vertex with two associated tracks • The Vertex must be inside the following region: rxy < 4 cm; |z|< 8 cm.
Filfo EVCL(RADstream) topological cut Total selection: 99% 54% 86% 46 %
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 5
energy energy
RAD stream
efficiency
RAD stream
efficiency
E(Mev)
RA
Dst
ream
R
AD
stre
am
E(Mev
)
RPI= 11.50%
E(Mev)
RPIs
tre RPI stream
efficiencyRPI streamefficiency
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 6
Invariant mass of two photons
Invariant mass of two photons
(MeV)
MC true
MC trueRAD
StreamMC true
RPI Stream
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RAD+RPI Stream Efficiency
RAD+RPI Stream Efficiency
Average = 66%
E(Mev)
E(Mev)
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 8
RPI Stream cutsRPI Stream cuts
EEMeV
(E
E
) (M
eV
)(E)(Mev)
SIGNALSIGNAL
rest frame • rest frame: (Erad) =363 Mev; pp–p
• p in lab. Frame• Boost in rest frame
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 9
RPI Stream cutsRPI Stream cuts
EEMeV(E
E
)
(MeV
)(E)(Mev)
Background
Background
Signal Background =Ncuts/NRPI 80.7%17.8%
(S/B)RPI = 3x10-3
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 10
RAD+RPI stream RAD+RPI stream
E (MeV)
SS+B
S/B=2x10-2
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 11
CutsCuts
Both stream:
•356 MeV<Egrad<368MeV
•S/B =0.14
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 12
Strong cutsStrong cuts
Only RAD stream
•P(2) > 10-4
•356MeV<Erad< 368MeV•Track mass > 200 MeV
•S/B =163
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 13
Angular distributionAngular distribution
Expected angular distribution dN/d(cos)~sin2
cos
Corrected MC generator is now in geanfi
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A first look at data A first look at data
RAD stream1 pb-1
M(MeV)
M(MeV)
Mtr
ack
I. Villella April 17th 2003 - Phi Radiative Decay Meeting- Frascati 15
Conclusions and OutlookConclusions and Outlook
• Clear signal on data •Reasonable background for events in radiative stream (but more careful evaluation is in progress)
• Events in rpi stream are vital to fit the spectrum; a strategy to recover events is in development, but will be necessary only if we improve S/B in that kinematical region
• Angular variables can help