Sabino Meola Charged kaon group meeting 14 December 2006 Status of analysis.
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Transcript of Sabino Meola Charged kaon group meeting 14 December 2006 Status of analysis.
Sabino Meola Charged kaon group meeting 14 December 2006
Status of analysis Status of analysis400eK 400eK
Sabino Meola Charged kaon group meeting 14 December 2006
The aim is to measure two relative branching ratios
The aim is to measure two relative branching ratios
4
3
3
400
00
00
00
00
00
)(
)(
eK
KObs
K
Obs
eKe
N
N
KBR
eKBR
Two normalization samples:- to events in order to obtain a cancellation of the systematic errors.- to events in order to keep under control the track-to-cluster association efficiency.
300K
3ke
4
3
3
40
00
00
00
)(
)(
eK
KeObsKe
Obs
eK
e
e
N
N
eKBR
eKBR
Sabino Meola Charged kaon group meeting 14 December 2006
K00e4 VS K003K00e4 VS K003
The measurement strategy is articulated in 5 steps:1. Neutral vertex (4).2. → association.3. Kinematic fit.4. Track to cluster association.5. Background rejection.
Sabino Meola Charged kaon group meeting 14 December 2006
Step 1: The neutral vertex method (4)
Step 1: The neutral vertex method (4)
Allows the selection of events with 2 0
in the final state
±→X±
The neutral vertex must satisfy thefollowing requests:
• 4 neutral clusters on time(t - r/c) = (t - r/c)2= (t - r/c) = (t - r/c)
• consistency with Kaon time of flight
Signal K003 Ke3
783 ~6·105 2690
S/B ratio after:~ 8·10-2
Signal PDG value: (2.2±0.4)·10-5
K00 3 PDG value: (1.757±0.024)·10-2
Ke3 PDG value: (4.98±0.07)·10-2
Sabino Meola Charged kaon group meeting 14 December 2006
Step 2: →0 associationStep 2: →0 association
• Cut on 2 of the
association →
• Cut on
2=|2best – 2
near|
Signal K003 Ke3
239 ~1.8·105
326
S/B ratio after:~ 7.5·10-2
Sabino Meola Charged kaon group meeting 14 December 2006
Step 3: kinematic fitStep 3: kinematic fit
• 4-momentum conservation
• invariant mass
• clusters on time
• consistency with Kaon time of flight
• missing 4-momentum having zero mass
• invariant mass
• clusters on time
• consistency with Kaon time of flight
3 hypothesis K00e4 hypothesis
Sabino Meola Charged kaon group meeting 14 December 2006
Step 3: kinematic fitStep 3: kinematic fit
Signal K003 Ke3
234 ~1·105 179
S/B ratio after:~ 4·10-2
2
400ek
2
300K
2
400ek
2
300K
Sabino Meola Charged kaon group meeting 14 December 2006
The measurement methodThe measurement methodWe consider the events distribution in the(m2,p) plane.
1
2
sec22
TrkVtxNeucl L
cttpm
Sabino Meola Charged kaon group meeting 14 December 2006
The measurement methodThe measurement method
K00e4 (blue region):
-900 < m2 < 3500 (MeV2)35 < p < 180 (MeV)
3 (violet region):
m2 < -1000 (MeV2)25 < p < 180 (MeV)
Sabino Meola Charged kaon group meeting 14 December 2006
Measure of the branching ratioMeasure of the branching ratio
)1(00
300
3 KMC
KData NN
The contribution of background on data is:
23.0
Sabino Meola Charged kaon group meeting 14 December 2006
Step 4: Track to cluster associationStep 4: Track to cluster association
Signal K003 Ke3
81 114 77
S/B ratio after:~ 0.4
Sabino Meola Charged kaon group meeting 14 December 2006
Background analysisBackground analysis
K00Is due to photon’s clusters wrongly associated to the secondary track.
Cut on P/E.
Ke3Is due to Ke3 radiative events.
02
01
sec EEEEE Kmiss
• Cut on minimum angle between the 4 photons and the secondary track
• Cut on Emiss
Sabino Meola Charged kaon group meeting 14 December 2006
Background rejectionBackground rejection
Signal K003 Ke3
71 77 21
S/B ratio after background rejection cuts:~ 0.7
Sabino Meola Charged kaon group meeting 14 December 2006
Measure of the branching ratioMeasure of the branching ratio
4
400
00
00
003
003
00
)(
)(
eK
K
Obs
K
Obs
eKe
N
N
KBR
eKBR
31048.1
21591663
4
003
00KeB
KB
ObsObs
eKNNNN
1586
51045.060.2
2300 10757.11048.1)( eveKBR
Relative error ~ 17%
Sabino Meola Charged kaon group meeting 14 December 2006
K00e4 VS Ke3K00e4 VS Ke3
The measurement strategy is articulated in 3 steps:1. Neutral vertex (2).2. Track to cluster association.3. Background rejection.
Sabino Meola Charged kaon group meeting 14 December 2006
Step 1: The neutral vertex method (2)
Step 1: The neutral vertex method (2)
Allows the selection of events with 1 0
in the final state
±→X±
The neutral vertex must satisfy thefollowing requests:
• 2 neutral clusters on time(t - r/c) = (t - r/c)2
• consistency with Kaon time of flight
• invariant mass
Signal K003 Ke3
1859 ~1.5·106 ~5.7·106
S/B ratio after:~ 4·10-3
Signal PDG value: (2.2±0.4)·10-5
K00 3 PDG value: (1.757±0.024)·10-2
Ke3 PDG value: (4.98±0.07)·10-2
Sabino Meola Charged kaon group meeting 14 December 2006
Step 2: Track-to-cluster associationStep 2: Track-to-cluster association
-900 < m2 < 3500 Mev/c2
Signal K003 Ke3
229 2317 ~5.7·105
S/B ratio after:~ 2.5·10-3
Sabino Meola Charged kaon group meeting 14 December 2006
sec0 EEEE Kmiss sec0 PPPP Kmiss
We perform a kinematic fit to constrain the photons 4-momentum.
Step 3: Ke3 event rejectionStep 3: Ke3 event rejection
We consider the E2miss-P2
miss variable
Sabino Meola Charged kaon group meeting 14 December 2006
3ke
400ek
Step 3: Ke3 rejectionStep 3: Ke3 rejection
We require E2m-P2
m < 2·104
Sabino Meola Charged kaon group meeting 14 December 2006
Background rejectionBackground rejection
• We require two more neutral clusters in the calorimeter.• Cut on p* to reject K±→0± events.• Cut on P/E in order to reject events with a charged pion in the final state.
Signal K003 Ke3
91 214 195
S/B ratio after background rejection cuts:~ 0.2
Sabino Meola Charged kaon group meeting 14 December 2006
Ke3 normalization method:• Implement a kinematic fit in Ke3 hypothesis (almost done).
To be doneTo be done
For both measurement strategy:• Tracking efficiency (already done).• TCA efficiency (almost done).• Trigger efficiency (almost done).• Tag Bias.• Systematic checks.
Sabino Meola Charged kaon group meeting 14 December 2006
ConclusionsConclusions
• The measurement method allows to estimate the K003 background contribution directly from data.
• Normalization to 3 events guarantees a cancellation of the systematic effects.
• A second measurement method with normalization to Ke3 events would allow to keep under control the track-to-cluster association efficiency.
• Will benefit of 2 fb-1 statistics.