The Carnegie Mellon University Program

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The Carnegie Mellon University Program for
Studying Baryon Resonance Photoproduction using
Partial Wave Analysis
Mike Williams
Curtis Meyer Matt Bellis Reinhard Schumacher
Zeb Krahn Doug Applegate
N 2005 FSU October 12-15
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Talk Outline
Program Goals
A Look at Our Data
Covariant Tensor Formalism
PWA Fitting Procedure
www-meg.phys.cmu.edu/pwa
Fit Output
Where were headed
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Program Goals
Our Goal Study the Baryon Spectrum by
Performing a Partial Wave
Analysis on the following channels
? p ? p p p
? p ? p?
? p ? p?
N Filters
www-meg.phys.cmu.edu/pwa
? p ? p?
? p ? K ?
? p ? K S
start analysis soon
Were Looking for Missing Baryons
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The Data
Our data was taken using the CEBAF Large
Acceptance Spectrometer located at Jefferson Lab
www-meg.phys.cmu.edu/pwa
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The Data
? p ? p?
? p ? p?
www-meg.phys.cmu.edu/pwa
Dalitz plot for ? p ? p p p
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Formalism
Covariant Tensor Formalism (Anisovich,Laget,)
u(p,m) eµ(p,m),
?µ ?5
Include terms for s,t,u and contact terms
www-meg.phys.cmu.edu/pwa
use regge trajectories for t-channel
Software C Code (see Doug Applegates Poster)
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Fitting Procedure
Un-binned Maximum Likelihood Method in each W-bin
Event by Event (we do NOT fit to cross sections)
Couplings and Fit Parameters
www-meg.phys.cmu.edu/pwa
Mass Independent Fit (only use BWs in daughter
decays)
We fit to intensity and phase of each wave
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Fit Output
Fit gives contribution of each wave in each W-bin
Ex.)
? p ? p?
(8 free parameters)
www-meg.phys.cmu.edu/pwa
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Coupled Channel
? p ? p?
Different Acceptance and Systematics
? p ? p?
? p ? p p p
www-meg.phys.cmu.edu/pwa
Use omega as N filter
? p ? p?
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Where were headed
Right now were working out Experimental Issues
Amplitude generation and Fitting code is up and
running
Weve run extensive test fits already
www-meg.phys.cmu.edu/pwa
Preliminary results in some channels should be
ready soon!