1. Λ 1520 Invariant Mass Analisys
Jung Han Kim
2006년 12월 14일

2. Contents Λ 1520 Decay mode Date Set PID ( Particle Identification )
Λ 1520 Invariant mass

3. Λ 1520 Decay mode Mass 1519.5±1.0 MeV Full width Γ 15.6±1.0 MeV
Λ1520 -> NK 45±1 %
Λ1520 -> Σπ 42±1 %
Λ1520 -> Λππ 10±1 %
Λ1520 -> Σππ 0.9±0.1 %
Λ1520 -> ΛΓ 0.8±0.2 %

4. Data Set run type Event Track 00R : sdt+-160GeV-pp-00R
Energy per nucleon : 160 GeV
Collision type : proton – proton
Event
Total event 2,000,000
Accepted event (cut) 1,304,781
Track
Accepted tracks(cut) 8,251, N/event
PID tracks Proton 175, N/event
Kaon 132, N/event
Total 307, N/event

5. Data Set Cut Event cut Track cut VertexX : -1, 1 VertexY : -1, 1
VertexZ : -620, 500
Multiplicity : 2, 30
EVeto : No information
Track cut
Bx : -4, 4
By : -2, 2
P : 0, 100
NPoint : 5, 200
dEdxNPoint : No inforation
TOF mass^2 : No information

6. Event Cut

7. Track Cut

8. PID ( Particle Identification )
dEdx
Separate Proton+Kaon, Pion, Electron.
Mass square from TOF
Determine Proton, Kaon
00R run type not have TofMass2 information.
Proton, Kaon separation.
Proton+ - Positive charge dEdx hitogram.
Kaon- - Negative charge dEdx histogram.
a few anti-Proton.
not consider about Kaon+

9. PID : 12 GeV ≤ P ＜ 13 GeV π
P + K e

10. PID : 12 GeV ≤ P ＜ 13 GeV
all charge
positive charge
negative charge
- Proton is dominant in positive charge dEdx histogram.
- Kaon is dominant in negative charge dEdx histogram.

11. P I D : all

12. P I D : positive - Proton

13. P I D : negative - Kaon

14. PID : proton vs kaon
Proton
Kaon

15. PID : proton vs kaon

16. Λ 1520 Invariant mass Signal Spectrum. Conditions Same event
Select event has more than 1 proton track, more than 1 kaon track.
Caculate invariant mass from all protons and all kaons.
Event 1
Event 2
Event 2
Event 2
6 Signal
2 Signal

17. Λ 1520 Invariant mass Event Mixing Background Spectrum. Conditions
Different event
Select event has more than 1 proton track, more than 1 kaon track.
Event 1
Event 2
Event 3
Event 4
Event 1
Event 2
Event 3
Event 4
7 Background

18. Λ 1520 Invariant mass
Signal & Background Spectrum.

19. Λ 1520 Invariant mass
Λ 1520 Invariant mass?
1.520 GeV

20. Thank you

21. Data Set run type Event Track 00R : sdt+-160GeV-pp-00R
Energy per nucleon : 160 GeV
Collision type : proton – proton
Event
Total event ,000
Accepted event (cut) 374,033
Track
Accepted tracks(cut) 2,364, N/event
PID tracks Proton 50, N/event
Kaon 38, N/event
Total 88, N/event

22. Λ 1520 Invariant mass
Signal & Background Spectrum.

23. Λ 1520 Invariant mass
Λ 1520 Invariant mass?