Status of the FOPI pp Beamtime- Motivation
- Particle Reconstruction- Inclusive Reconstruction
- Exclusive Reconstruction with kinematical Refit- Summary and Outlook
Motivation
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p
Kaonic bound statesΛ(1405)
Doorway Mechanism
Sp
pK
Λ (1405)
pK
p+T. Yamazaki et T. Akahishi, Phys. Rev. C 76 (2007) 045201
p–K- Potential
Robert Münzer Leannis Meeting – Prag – May 2012
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N* - Resonances
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Production Mechanism: p + p -> p + K+ + Λ
M. S.-W. : Eu. Phys. Jou. A 46
The Experiment
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The Experiment
s(Start – RPC) : 200 psS(Start – PLAWA) : 400 ps
Exclusive measurement:
• [email protected] GeV• Target: 2cm Liquid Hydrogen• 80 Million LVL2 Trigger Events
p + p
p- + p
+ K+ppK-
L + p
L(1405) + p + K+3.1 GeV
Beam
Magnet
CDC
Barrel
RPC
Helitron
PLAWA
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SiLViO
Beam
Magnet
CDC
Barrel
RPC
Helitron
PLAWA
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Polar angle of particles from Λ decay (pK+Λ / K+ in RPC acceptance)
LVL1 / LVL2: Signal (pK+Λ): 5.8
Background (UrQMD pp 3.1GeV): 20.3
Trigger conditions
LVL1: M(TOF) > 1
LVL2: LVL1 + SiΛVIO
Silicon Λ-Vertexing and Identification OnlineSiΛViO
M>0
M>1
NIMA617:300-302,2010
SiΛViO Acceptance
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Particle Selection
Particle Identification
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Backward HemisphereCDC momentum + energy loss
Forward HemisphereHelitron momentum + Plawa TOFPreliminary
Preliminary
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Calibration not final
Kaon IdentificationTime of Flight Detectors: Resistive Plate Chambers (RPC)Preliminary
Preliminary
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p-
p
Λ
Inclusive Reconstruction
Inclusive Λ Reconstruction
Datapp SimulationPreliminary
Preliminary
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Λp
p
CDC HELITRON
SiLViO
RPC
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Inclusive Λ Reconstruction
Data LVL2Data LVL1
Enhancement:> 4,4
Fits to simulation
Preliminary
Preliminary
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Lp
p
CDC HELITRON
SiLViO
RPC
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Exlcusive Reconstruction
K+
p-
pL
Kinematical Refit Modify Particle Track Parameters (mom, phi, theta) within error
to fulfill contraints.Results: New Particle Track Parameters , c2
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p-value(refit) =
Background
Robert Münzer Leannis Meeting – Prag – May 2012
Diploma ThesisD. Pleiner
Kinematical Refit
Conservation Constraint
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K+
pp
(E,p)beam (E,p)target
(E,p)kaon (E,p)pion
(E,p)secproton
(E,p)primproton
p
p
π-
K+
Λ
Esecproton + Epion + Eprimproton + Ekaon = Ebeam + Etarget
psecproton + ppion + pprimproton + pkaon = pbeam + ptarget
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Kinematical Refit
Mass Constraint
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K+
pp
(E,p)beam (E,p)target
(E,p)pion
(E,p)secproton
(E,p)primproton
p
p
π-
K+
Λ
{ (E,p)secproton + (E,p)pion }² = M(Λ)²
(E,p)kaon
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Kinematical Refit
Mass Constraint
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K+
pp
(E,p)beam (E,p)target
(E,p)pion
(E,p)secproton
(E,p)primproton
p
p
π-
K+
Λ
Vertex Constraints: Intersection p and π
(E,p)kaon
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Kinematical Refit
Mass Constraint
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K+
pp
(E,p)beam (E,p)target
(E,p)pion
(E,p)secproton
(E,p)primproton
p
p
π-
K+
Λ
Vertex Constraints: Intersection p and K+
(E,p)kaon
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Kinematical Refit
Mass Constraint
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K+
pp
(E,p)beam (E,p)target
(E,p)pion
(E,p)secproton
(E,p)primproton
p
p
π-
K+
Λ
Vertex Constraints: Primary & Secondary Vertex
(E,p)kaon
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Exlcusive Reconstructionpp – Simulation (URQMD)
K+
p-
pL
Conservation Constraint
Esecproton + Epion + Eprimproton + Ekaon = Ebeam + Etarget
psecproton + ppion + pprimproton + pkaon = pbeam + ptarget
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pval> 0.007 pval> 0.007
Conservation Constraint
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Invariant mass (p, π)With refit Without refit
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Conservation + Mass Constraint
Esecproton + Epion + Eprimproton + Ekaon = Ebeam + Etarget
psecproton + ppion + pprimproton + pkaon = pbeam + ptarget
{ (E,p)secproton + (E,p)pion }² = M(Λ)²
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Invariant mass (p, π)With refit Without refit
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pval>0.007
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Missing Mass(p)Without Refit With Refit
N* included in Urqmd
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pval>0.007
p+p -> p + N* ( -> Λ + K+ )
Exlcusive ReconstructionData
K+
p-
pL
Data
Original pval cut(>0.87)Original Invariant Mass (p,π)
Energy & Momentum Contraint
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N*
MM (p) - refitted
Pp UrQMD
MM (p) - refitted
Data
Unrefittedrefitted
|Inv(p,pi)-1.116|<40 Mev
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Systematical Errors
Primary proton
pion
1/p ϑ φ
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Summary & Outlook• Inclusive Lambda-Routine:
– Lambda are visible in Semi Forward Kombination– Reduction Compareable with Simulations
• Exclusive Reconstruction tested with simulation– Event Selection: Refit is sensitive to Different Channels– Additional Constraints (Vertex) has to be tested.– Resolutiuon can be improved signal: N* signal as a crosscheck
• Refit with Data– Pval Cut reduced Background of Exclusive Lambda.– N*- signal visble : Crosscheck of analysis– Problem: Systematical Errors
• New Calibration– Finished recently. Has to be tested.
Backup
Different Regions
Lp
p
CDC HELITRON
SiLvio
RPC
L
p
p
CDC HELITRON
SiLvio
RPC
Semi – Forward (CDC – (RPC) )
Forward (SiLViO – Helitron - Plawa)
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Polar angle of particles from Λ decay (pK+Λ / K+ in RPC acceptance)
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Event Selection
- + + + Available tracks
4 5
+
321
Pi-cand
1
K+ -Cand
1
P-cand
1
P-cand
2Rough PID
4 5
p-cand
3
321
Pi-cand
1
K+ -Cand
1
P-cand
1
P-cand
2Bild Kombination
p-cand
3
Pi-cand
1
P-cand
1
K+ -Cand
1
P-cand
2
Pi-cand
1
P-cand
2
K+ -Cand
1
P-cand
1
Komb 1 Komb 2
Pi-cand
1
P-cand
1
K+ -Cand
1
P-cand
3
Komb 3 Komb i
PrefitKomb (i)
Prefit
Komb (i)
Chi2 - Pval
PrefitKomb (i)
Sort descending by pval
Komb 1 (biggest pval) will be used
Chi2 - Pval
Remaining particle is treated as faketrack
Best
Lambda Preselection
Preselectio Option 2: 75% of Lambda Kombination are select
Main Fit
Orig Orig Orig Orig
Komb 1 (biggest pval) will be used
Best
Refit Ref Ref Ref Ref
Komb 1 (biggest pval) will be used
BestNtuple
Chi2 Pval
Inv(p,π)
Inv(Λ,p)
Inv(Λ,K)
mm(p)
mm(K)
rInv(p,π)
rInv(Λ,p)
Inv(Λ,K)r
rmm(p)
rmm(K)mm(K,p) rmm(K,p)Vertices rVertices
Conservation ConstraintPval > 0.1
Conservation Constraint
allpkΣ
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦=𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡𝑠 (𝑝𝑣𝑎𝑙>𝑝𝑣𝑎𝑙𝑐𝑢𝑡 )
𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡 (𝑎𝑙𝑙)Purity
Conservation Constraint
allpkΣ
Best Value: 0.0007
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦=𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡𝑠 (𝑝𝑣𝑎𝑙>𝑝𝑣𝑎𝑙𝑐𝑢𝑡 )
𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡 (𝑎𝑙𝑙)Purity
Conservation Constraint
Missing Mass (p, K)
Different ContraintsConservation Conservation+ Mass
Invariant Mass (p,π)
Invariant mass (p, π)Conservation Conservation+ Mass
Missing Mass (p)
Missing Mass(p)Conservation Conservation+ Mass
N* included in Urqmd
Missing Mass(p)Conservation pKL - Phasespace
N* included in Urqmd
Missing Mass (p, K)
Different ContraintsConservation Conservation+ Mass
Exlcusive ReconstructionData
K+
p-
pL
Data
Original pval cut(>0.87)Original Invariant Mass (p,π)
Energy & Momentum Contraint
Data
RefittedOriginal
Missing Mass pK+
μ=1.132σ=0.039
μ=1.24σ=0.050
|InvM(p,p)-1.116|<0.02Pval.ne.0
Energy & Momentum Contraint
μ=1.112σ=0.016
Absolutely Preliminary
DatapkL Phasespace
Missing mass K (refitted)
Refit
Refit