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Photoproduction of M. Niiyama

p K++0p0p K++∓-n

TPC data w/ CH2 and carbon target.

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Physics Motivation structure of Λ*(1405)

• To measure in medium modification of the lineshape of • First, measure the production cross section from free proton in CH2

E. Oset et al.

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TPC

E // B

700mm

Target holder

High voltage plane

Wire & padplane

Drift field cage

Beam

Active volume (cylindrical shape) 700 mm in length 400 mm in diameter

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• The mass difference between and is too small to be separated by missing mass mm(K+).• Detect decay products and distinguish these two hyperon resonances.• Measure the production ratio / using TPC data• Extract the absolute value of and from liquid hydrogen target with the input of measured production ratio.p K++0p0p K++∓-n

Outline

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spectrum of in 2 Ebins

p K++0p0

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Spectrum of comparison with Ahn-san’s

measurement at LEPS

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Angular distribution of from decay. (angle K in CM)Ahn-san’s measurement This work

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spectrum of in 2 Ebins

p K++∓-n

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Ratio of in 2 Ebins GeV 0.54±0.17 GeV 0.084±0.076

GeV GeV

|t| GeV^2 |q|^2 (GeV/c^2

t nor q^2 doesn’t change.Edependence should be due to the other reason.

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Absolute value of the differential cross section

Fit to MM(K+) spectrum of liq. H2 data with the input of production ratio of /

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Summary

he production cross section of decreases in higher photon energy region. It seems not due to t-dependence or q^2-dependence. It should be due to the other production mechanism.

We have measured the ratio of The absolute value is obtained using LH2 data.

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MC

p K+

in 2 tbins

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spectrum of in 2 tbins

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mm(K) for tagged eventsin 2 tbins

|t|<0.22 |t|>0.22