Status of the FOPI pp Beamtime

Status of the FOPI pp Beamtime- Motivation

- Particle Reconstruction- Inclusive Reconstruction

- Exclusive Reconstruction with kinematical Refit- Summary and Outlook

Motivation

3

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

4

N* - Resonances


Production Mechanism: p + p -> p + K+ + Λ

M. S.-W. : Eu. Phys. Jou. A 46

The Experiment

6

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


7

SiLViO

Beam

Magnet

CDC

Barrel

RPC

Helitron

PLAWA


8

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


Particle Selection

Particle Identification

10

Backward HemisphereCDC momentum + energy loss

Forward HemisphereHelitron momentum + Plawa TOFPreliminary

Preliminary


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

13

Λp

p

CDC HELITRON

SiLViO

RPC


Inclusive Λ Reconstruction

Data LVL2Data LVL1

Enhancement:> 4,4

Fits to simulation

Preliminary

Preliminary

14

Lp

p

CDC HELITRON

SiLViO

RPC


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

16

p-value(refit) =

Background


Diploma ThesisD. Pleiner

Kinematical Refit

Conservation Constraint

17

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


Kinematical Refit

Mass Constraint

18

K+

pp


(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


Kinematical Refit

Mass Constraint

19

K+

pp


(E,p)pion

(E,p)secproton

(E,p)primproton

p

p

π-

K+

Λ

Vertex Constraints: Intersection p and π

(E,p)kaon


Kinematical Refit

Mass Constraint

20

K+

pp


(E,p)pion

(E,p)secproton

(E,p)primproton

p

p

π-

K+

Λ

Vertex Constraints: Intersection p and K+

(E,p)kaon


Kinematical Refit

Mass Constraint

21

K+

pp


(E,p)pion

(E,p)secproton

(E,p)primproton

p

p

π-

K+

Λ

Vertex Constraints: Primary & Secondary Vertex

(E,p)kaon


Exlcusive Reconstructionpp – Simulation (URQMD)

K+

p-

pL




24

pval> 0.007 pval> 0.007



25

Invariant mass (p, π)With refit Without refit


Conservation + Mass Constraint



{ (E,p)secproton + (E,p)pion }² = M(Λ)²

27

Invariant mass (p, π)With refit Without refit


pval>0.007

28

Missing Mass(p)Without Refit With Refit

N* included in Urqmd


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

31

N*

MM (p) - refitted

Pp UrQMD

MM (p) - refitted

Data

Unrefittedrefitted

|Inv(p,pi)-1.116|<40 Mev


32

Systematical Errors

Primary proton

pion

1/p ϑ φ


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)

35

Polar angle of particles from Λ decay (pK+Λ / K+ in RPC acceptance)


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


Best

Refit Ref Ref Ref Ref


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


allpkΣ

𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦=𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡𝑠 (𝑝𝑣𝑎𝑙>𝑝𝑣𝑎𝑙𝑐𝑢𝑡 )

𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡 (𝑎𝑙𝑙)Purity


allpkΣ

Best Value: 0.0007

𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦=𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡𝑠 (𝑝𝑣𝑎𝑙>𝑝𝑣𝑎𝑙𝑐𝑢𝑡 )

𝑝𝑘𝐿−𝐸𝑣𝑒𝑛𝑡 (𝑎𝑙𝑙)Purity


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


Missing Mass(p)Conservation pKL - Phasespace


Missing Mass (p, K)

Different ContraintsConservation Conservation+ Mass

Exlcusive ReconstructionData

K+

p-

pL

Data

Original pval cut(>0.87)Original Invariant Mass (p,π)


Data

RefittedOriginal

Missing Mass pK+

μ=1.132σ=0.039

μ=1.24σ=0.050

|InvM(p,p)-1.116|<0.02Pval.ne.0


μ=1.112σ=0.016

Absolutely Preliminary

DatapkL Phasespace

Missing mass K (refitted)

Refit

Refit

Status of the FOPI pp Beamtime

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