the study of βπ 0,1,2indico.ihep.ac.cn/event/5100/contribution/14/material/slides/0.pdfΒ Β·...
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The study of πβ² β π+πβππ0,1,2
Zhang Jielei Zhang Jingzhi
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Outline
1γMotivation
2γData sets
3γThe study of πβ² β π+πβππ0,1,2
Event selection
Data and Background study
Data and MC distributions
4γSummary
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Motivation
In theory, the transition process πβ²(β²) β πΎπππ½ is not consistent with experiment measurement very well.
Q. Zhao et al consider open charm effects, many channels can consistent with experiment measurement very well except for πβ² β πΎππ2.
In the process πβ² β π+πβπππ½, π+πβ from a virtual photon. To study the process can
provide more information for theory. Furthermore, we can get the distribution of form factor, from the distribution we can extract parameters as theoretical input.
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Data sets
Boss Version : 6.6.4-p03
Data sets :
Signal MC :
πβ² β π+πβππ0,1,2(DIY), ππ0,1,2 β πΎπ½/π, π½/π β π+πβ/π+πβ
Inclusive MC (2009 and 2012 πβ² MC)
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106 M πβ² of year 2009341.5 M πβ² of year 2012continuum background study : ~44pbβ1 data @ 3650
Background MC :
1.πβ² β πΎππ0,1,2, ππ0,1,2 β πΎπ½/π, π½/π β π+πβ/π+πβ
2.πβ² β ππ½/π, π β πΎπΎ, π½/π β π+πβ/π+πβ
3.πβ² β π/π0π½/π, π/π0 β πΎπ+πβ, π½/π β π+πβ/π+πβ
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Event selections
Charged tracks- π π₯π¦ < 1ππ, π π§ < 10ππ
- πππ π < 0.93- π = 4, π = 0
Good photon- 0 β€ ππ·πΆ β€ 14- Barrel :πΈ > 0.025 GeV, πππ π < 0.8
- Endcap :πΈ > 0.050 GeV, 0.86 < πππ π < 0.92
- βπ > 200
- ππΎ β₯ 1
Particle separation- π from πβ² βΆ ππππ < 1 GeV- π from π½/π βΆ ππππ > 1 GeV&&πΈπππ >1 GeV- π from π½/π βΆ ππππ > 1 GeV&&πΈπππ <0.4 GeV
4C kinematic fit- Choose the photon with least π2
- π4πΆ2 < 40
Other selections- π½/π mass window : (3.08, 3.12) GeV- 0.16 < π πΎπ+πβ < 0.50 GeV- π π₯π¦ < 1.5||π π₯π¦ > 7.0 cm
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π4πΆ2 of kinematic fit
π2 distribution from 4C : π4πΆ2 < 40
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π½/π invariant mass distributions7
π½/π mass window : 3.08 < π π+πβ < 3.12 GeV
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Background study
The main background :
1.πβ² β πΎππ0,1,2, ππ0,1,2 β πΎπ½/π, π½/π β π+πβ/π+πβ
2.πβ² β ππ½/π, π β πΎπΎ, π½/π β π+πβ/π+πβ
3.πβ² β π/π0π½/π, π/π0 β πΎπ+πβ, π½/π β π+πβ/π+πβ
πΎ conversion
Same final state
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π π₯ VS π π¦ distributions9
Background(πΎπ1)
Background(πΎπ2)
DATA(π1)
DATA(π2)
Some variables from GammaConv package.
MC(π1)
MC(π2)
πΎ conversion MC
in ππ1 region
in ππ2 region
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π π₯π¦ distributions10 Remove πΎ conversion background
π π₯π¦ < 1.5||π π₯π¦ > 7.0 cm
From πΎ conversion MC, there are no events in the region. These events have large angle between π+ and πβ. For signal MC, if the π+
and πβ have large angle, the event will be reconstructed in the region.
πΎ conversion events
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π(πΎπ+πβ) distributions11
0.16 < π πΎπ+πβ < 0.50 GeV
Remove πβ² β π/π0π½/π, π/π0 β πΎπ+πβ, π½/π β π+πβ/π+πβ process
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Background study
From inclusive MC, we find only one events survived.
From 44 pbβ1 3650 data sample, only one event survived the event selections.
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π(πΎπ½/π) distributions13
Clear ππ1 and ππ2 signal, and some ππ0 signal
πβ² β πΎπππ½ , πππ½ β π+πβπ½/π process
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π π(π+πβ) distributions14
π+πβ recoiling invariant mass distribution π π(π+πβ)
(before 4C kinematic fit)
Clear ππ1 and ππ2 signal, and some ππ0 signal
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ππ+πβdistributions15
The angular distribution between π+ and πβ in ππ1
and ππ2 signal region
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Momentum distributions16
π+ and πβ momentum distribution in ππ1 and ππ2
signal region
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πππ π distributions17
π+ and πβ πππ π angular distribution in ππ1 and ππ2
signal region
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Invariant mass distributions18
π(π+πβ), π(π+ππ1,2) and π(πβππ1,2) distribution in ππ1
and ππ2 signal region
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Helicity πππ π distributions19
π+ and πβ helicity angular distribution in ππ1 and ππ2
signal region
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Scatter plots20
ππ+πβ VS π π₯π¦, π(π+πβ) VS π π₯π¦ and ππ+πβ VS π(π+πβ)
distributions for data.
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Signal extraction from data
Signal : MC-determined shape to describe signal ππ0,1,2, the πππ0,1,2 is float
Background : 1γ1-st order polynomial, the ππππ1 are float2γπβ² β πΎππ0, ππ0 β π+πβπ½/π process MC-determined shape, the ππππ2 are float
πππ0 = 62 Β± 10 πππ1 = 884 Β± 30 πππ2 = 229 Β± 16
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Summary
1γThe process πβ² β π+πβππ0,1,2 is studied, there are clear ππ1 and ππ2signal and some ππ0 signal.
2γThe most of events focus on the small angle between π+ and πβ, and there are some events focus on the large angle between π+ and πβ, these events canβt be understood.
3γThe process πππ½ β π+πβπ½/π also be observed.
Next to do1γFurther analysis of the background
2γStudy generator to get more accurate efficiency for data and give branching fraction
3γStudy the process πππ½ β π+πβπ½/π in detail
Thanks for your attention!
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BACK UP
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Some distributions for large angle between π+ and πβ
π(πΎπ½/π) π2
π+ track π2 πβ track π2
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Efficiency curve
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26 Some events for large angle between π+ and πβ
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Branching fraction
β¬ πβ² β π+πβππ0,1,2 =πππ0,1,2
ππ‘ππ‘ β β¬(ππ0,1,2 β πΎπ½/π) β β¬(π½/π β π+πβ) β π0,1,2
β¬ πβ² β π+πβππ1 = (5.9 Β± 0.2) Γ 10β4
β¬ πβ² β π+πβππ2 = (6.2 Β± 0.5) Γ 10β4
1. π0 = 11.7%
2. π1 = 8.1%
3. π2 = 3.5%
β¬ πβ² β π+πβππ0 = (6.7 Β± 1.3) Γ 10β4
Need further studyPHSP MC