status of the fopi pp beamtime -motivation -particle reconstruction -inclusive reconstruction...

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

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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:

• p-beam@3.1 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

11Robert Münzer Leannis Meeting – Prag – May 2012

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

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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 φRobert Münzer Leannis Meeting – Prag – May 2012

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

Lp

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