study of two pion channel from photoproduction on the deuteron
DESCRIPTION
Study of two pion channel from photoproduction on the deuteron. Lewis Graham Proposal Phys 745 Class May 6, 2009. Overview. Physics Motivation EG3 Data Set Analysis Outlook. This CLAS Analysis…. will use eg3 data set will study 2 π decays measuring the cross section for - PowerPoint PPT PresentationTRANSCRIPT
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Study of two pion channel from photoproduction on the deuteron
Lewis Graham
Proposal
Phys 745 Class
May 6, 2009
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Overview
• Physics Motivation
• EG3 Data Set
• Analysis
• Outlook
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This CLAS Analysis…
will use eg3 data set
will study 2π decays measuring the cross section for γd → Δ++(pπ+)π- and the angular dependent cross sections detecting all final state particles
will study final-state interactions with the “spectator” neutron
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a first measurement of the Δ+
+π- channel covering the energies and kinematics required to investigate higher lying resonances.
a first look at cross sections for kinematic and systematic effects.
a better understanding of the eg3 systematics.
The proposal is based on results from this analysis!
The main motivations are to provide…
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N* photoproduction experiments at JLab
on the proton g1: circular beam polarization g8b: linear beam polarization FROST: polarized beam and target
Analysis of current photoproduction data on the proton finds
all PDG 2*, 3*, and 4* resonances below 2.1 GeV no 1* resonances (P31(1750), S11(2090), P11(2100), …) no ‘missing’ N* resonances
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High lying (W >1.7 GeV) nucleon resonances study. Current study of high lying (W >1.6 GeV) nucleon resonances (can compare).
Extraction of known resonances with data extending to high energy range ( ~ 5.5 GeV). Existing data is only up to 5.1 GeV.
Search for possible signals from missing baryon states.
Physics Goals
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From S. Capstick and W. Roberts,Phys. Rev. D49, (1994) 4570
(Relativized 3P0 model)
Predicted but not observed in the experiment states are expected to decouple from N channel
but couple to the , N, N channels. Most of the
Nucleon Spectroscopyinformation was
obtained from N N(X) reactions
Res. ()(MeV)
()(MeV)
()(MeV)
()(MeV)
N1(1880)+ 8 80 5 25N3(1910)+ 1 300 10 70N3(1950)+ 16 60 15 40N1(1975)+ 4 20 6 10N5(1980)+ 2 240 5 8
Therefore, missing states
may be observed in the channels of
multihadron production by photons for instance
in two pion channel.
Missing States
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Jefferson Lab
Hall B
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CEBAF Large Acceptance Spectrometer
Drift chambersargon/CO2 gas, 35,000 cells
Electromagnetic calorimetersLead/scintillator, 1296 PMTs
Torus magnet6 superconducting coils
Gas Cherenkov counterse/ separation, 216 PMTs
Time-of-flight countersplastic scintillators, 684 PMTs
Large angle calorimetersLead/scintillator, 512 PMTs
Liquid D2 (H2)target, NH3, ND3start counter; e minitorus
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CLAS 4detector torodail magnetic field 3 drift chamber regions time of flight electromagnetic calorimeter Cerenkov Counter
Electron Beam Energy 5.7 GeV Luminosity 1034 cm-2 s-1
Momentum Resolution < 1% Capability of detecting multiparticle final states
Particle production in CLAS
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CLAS Detection
Allows simultaneous detection of multiple particles in the final state.
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EG3 Run Conditions
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Analysis of γd →∆++(pπ+)π-
Particle IdentificationCutsTiming
Extracting YieldFitting ProcedureDetector Simulation
GSIMParameters (MC Events)
NormalizationGFlux Method
Systematic Errors
d
∆++
p
π+
(n)
on a deuteron target
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Particle Identification
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∆++ Identification
∆++ = 1232 MeV
p + π+
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Cuts
PID:
• 3-track Requirement
• Missing Mass2 Cut (.8 GeV2< MM2 < .97 GeV2)
• Skim Cut (0.7 GeV < M < 1.2 GeV) •Proton Momentum – 450 MeV
Timing:
• Max. Vertex time of protons and pions - 2ns
• TOF difference of photon and avg. particle – 2ns.
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Simulation
• Generated 10M Events.
• Events Generated with same parameters as Data.
• Binned in 44 Energy bins and fit with breit-wigner.
• Yield Extracted for each fit energy bin.
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Acceptance Calculation
Acceptance = Reconstructed / Generated Events
Reconstructed Generated Events
Acceptance
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Normalization
• Data was normalized by the photon flux
• Each event in the data sample is corrected by a corresponding number of photons in the flux spectrum
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Corrections
Acceptance (simulation)
Timing cuts
Eloss Correction
Proton Momentum Cut
GFlux Correction
Prescale
Luminosity
Fiducial Cuts
Energy Bin Correction
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Data Fits with Corrections
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Cross Section Extraction
After LuminosityAfter Acceptance
Luminosity = target density * target length * Avogadro’s Number /Mole mass
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Comparison of Preliminary Results
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Next Steps in Analysis!
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Fit of +-p single differential cross-sections and the contributions from particular mechanisms with the JLAB-MSU (JM) model.
Full calculationsp-++
p+0
ppp-P++
33(1600)
p+F015(1685)
direct 2production
p+D13(1520)
Combined fit of various 1-diff. cross-sections allowed to establish all significant mechanisms.
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Complete set of unpolarized 1-differential cross-sections in r,v→-+p reactions.
For unpolarized beam/target, the final state, r,v→-+p reaction offers 9 independent single-differential cross-sections in each (W&Q2) bin. All these cross-sections are available from CLAS for the first time.
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fit within the framework of JM06 model
resonant part
non-resonant part
differences in the shapes of resonant/non-resonant cross-sections make possible to isolate N* contribution.
Resonant and non-resonant contributions fit within the framework of JM model
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What’s to Come
Angular Dependence Cross Sections
Theoretical Model Incorporation and Interpretations to Data
Comparisons to Published Data
Contribution to World Data
Possible Missing Resonances found