[Clas_hadron] Abstract for April APS meeting

[Reinhard Schumacher]

Hello All,

     Dao Ho plans to give a talk at the April 2013 APS meeting based on 
work he has shown at the CLAS hadron spectroscopy meetings.  The final 
results have been approved by the working group on 11-7-12. Dao plans to 
give the talk at the next CLAS meeting in February for practice.  Below 
is the abstract that we will submit this Friday. Any comments before 
then are welcome.  Note the it is at its maximum length already, so it 
cannot be expanded at all.  Sorry it is not in PDF form:  the new APS 
web "test" submission process makes that difficult to do.

Sincerely,
Reinhard
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Abstract for April 2013 APS meeting in Denver

Decay of the $\Lambda(1520)$ to $\Lambda\pi\pi$ via $\Sigma(1385)\pi$

Dao Ho^1, R. A. Schumacher^1, K. Moriya^2
1 Carnegie Mellon University
2 Indiana University
(for the CLAS Collaboration)

The $\Lambda(1520)$ $J^P = 3/2^-$ hyperon may have a $\Sigma(1385)\pi$ 
substructure proposed in recent unitarized coupled-channel calculations. 
While
the branching fraction of the $\Lambda(1520) \to \Lambda\pi\pi$ is well 
known to be $0.10\pm0.01$, less well established is the relative branching
fraction of the intermediate quasi-two-body mode $\Lambda(1520) \to 
\Sigma(1385)\pi \to \Lambda\pi\pi$.  Previous measurements range from an 
upper
limit of 0.44 to a value of 0.82. At CLAS a tagged real photon beam with 
highest energy at 3.8 GeV impinged upon a 40 cm LH2 target to 
reconstruct the
parent hyperon using $\gamma p \to K^+ \Lambda(1520)$ from the detected 
kaon. Detection of both $\pi^+$ and $\pi^-$, with a ground state 
$\Lambda$ in
the overall missing mass, allowed complete reconstruction of the event 
kinematics.  An incoherent Dalitz-type analysis of the $\Lambda\pi\pi$ 
final
state was used to determine the relative  proportion of quasi-two-body 
$\Sigma\pi$ and direct $\Lambda\pi\pi$ in the decay process.  Simulation 
of the
direct and two-step decay processes was used to match the data, with the 
branching fraction as a fitting parameter. Backgrounds were also modeled 
and
included in the fits for the $\Lambda(1520)$ mass from 1.48 to 1.59 GeV.

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Reinhard Schumacher         Department of Physics, 5000 Forbes Ave.
Carnegie Mellon University, Pittsburgh, PA 15213, U.S.A.
phone: 412-268-5177         web: www-meg.phys.cmu.edu/~schumach
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