L(1405)/S(1385) Photoproduction in SLH2

Deuk Soon Ahn

t-channel dynamics dominance

Basic assumption:At Eγ ≈ 2 GeV, the γ p → K+ π0 Λ and γ p→K+π Σ reactionsin the region of the Σ(1385) and the Λ(1405) resonances arelargely driven by the K- t-channel exchange.

1. t- channel dynamics, to gain understanding of the K-p-> π0Λ and of the K-p-> πΣ amplitudes below the KN thereshold, where they are dominated by the Σ(1385) and Λ(1405) resonances.

2. Ingoing photon dissociates into real K+ and virtual K-, the off-shell K-scattering subsequently off the proton target to the dsigma/dt with increasing |t|. (t means the square of the 4 momentum transfer from the proton to the L(1405)and S(1385))

3. Theoretical differential cross sections for the γ p → K+ (π0Λ) and γ p → K+ (πΣ) reactions in the region of the Σ(1385) and the Λ(1405) resonances .(double kaon pole term contribution is large.)

Nucl. Phys. A 748 (2005) 499

Old data: Production of hyperons by virtual photons

T. Azemoon et al. NP B95 (1975) 77

e-p →e- K+ Y Y = Λ, Σ, Σ(1385), Λ(1405), Λ(1520)

Rapid fall-off suggesting a t-channel exchange process

w = (π Y) total center of mass energy

The γ p → K+ π 0Λ and γ p → K+ π Σ cross sections as functions of the total π Y center of mass energy for different values of Eγ

W=1.415

W=1.425W=1.405

W=1.395

W=1.435

Double pole term single pole term

Event SelctionCut HORI VERT HORI+VERT Comments

Analyzed Event 5040394 4907022 9947416

ntag=1 3274650 3067322 6341972

Itagc.f>0 3404480 3231379 6635859 ~4.6% increased

ntrk>0 2595506 2445390 5040896

K+ PID (3sigma) 107031 109822 216853

DecayInFlight 98961 101267 199958

e+e- bar 93423 96569 189992

-1100<vtz<-900 46529 48412 94941

Vtz w/Cu cut 45320 47283 92603 ~2.5% decreased

npl(1)=0.or.npl(2)=0 44124 45929 900531.91<Eg<1.93,2.27<Eg<2.30 44883 46757 91640

MissingMass –Z-vertex Cut Z-vertex , X-Vertex

X-vertx , Y-vertex in the target region for double track events. Coming from target cell.Because of extended size of photon beam spot@target,(especially in Hori) part of photon beam hit the target cell(Cu) and events produced from there.

-1000<vtz<-900 -900<vtz<-800

-910<vtz<-900 -900<vtz<-890

-1200<vtz<-1100 -1100<vtz<-1000

Photon energy spectrum for ntag=1or2 events by kato’s itagc.f

Rejected events by tagcut using npl

Shieding materials are placed in High electron E of tagger(corresponding Low photon energy). There remains possibility that recoil electron with high energy outside the range of tagger.Or produce the shower at the material. npl1=0or npl2=0 is the number of hits which is not associated in PL. (selected event for which is no other hit than recoil electron, at least one of two.

Because of a few dead stripes in SSD layer. We allow there is no hit in these strips to save tracks passed these area.

MissingMass & momemtum transfer

MissingMass |t|-|t|min

Coun

ts

Coun

ts

0<|t|-|t|min<0.10 0.10<|t|-|t|min<0.20

0.20<|t|-|t|min<0.30 0.30<|t|-|t|min<0.40

0.40<|t|-|t|min<0.50 0.50<|t|-|t|min<0.60

MissingMass(GeV/c^2)

Coun

ts/5

MeV

MissingMass –E18bins (E1.5-2.4)

Photon Energy

|t|-|t|min

K+MissingMassL(1116)

S(1193)S(1385)/L(1116)

L(1520) nonresont

Eg(GeV)

MMp(g,K+) – all T &T1-T5 cut

All |t|-|t|min

0.<|t|-|t|min<0.10

0.10<|t|-|t|min<0.20 0.20<|t|-|t|min<0.30

0.30<|t|-|t|min<0.400.40<|t|-|t|min<0.50

Differential cross section

• Minimum momemtum transfer |t|min varies drastically when photon energy changed. -> t’ = |t|-|t|min is introduced.

• ds/dt’ =a (exp(-bt)) b : slope 　；　 The yield which is corrected acceptance is fitted with

exponential function • Photon normalization not included yet.

dt

A * (NK+ - B)dsNB * NT * dt

=

Yields of L(1116) as function of|t|-|t|min , Data

|t|-|t|min

Coun

ts

Acceptance of L(1116) as function of |t|-|t|min , MC

|t|-|t|min

dsig

ma/

dt (A

br.U

nit.)

|t|-|t|min

Differential Cross Section :Acceptance corrected yield|t|-|t|min distribution on L(1116)

Energy dependence of slope parameter b

Yields of L(1405)/S(1385) |t|-|t|min , Data

|t|-|t|min

Coun

ts

Acceptance of L(1405) |t|-|t|min , MC

|t|-|t|min

dsig

ma/

dt (A

br.U

nit.)

|t|-|t|min

Differential Cross Section of L(1405)/S(1385)

Energy dependence of slope parameter b

Yields of L(1520) |t|-|t|min , Data

|t|-|t|min

Coun

ts

Acceptance of L(1520) |t|-|t|min , MC

|t|-|t|min

dsig

ma/

dt (A

br.U

nit.)

|t|-|t|min

Differential Cross Section of L(1520)

Energy dependence of slope parameter b

Acceptance-corrected t’ ; 1.35<MM<1.44(9 MMslice)&E1-E9

1.35<MM<1.36 1.36<MM<1.37 1.37<MM<1.38

1.38<MM<1.39 1.39<MM<1.40 1.40<MM<1.41

1.41<MM<1.42 1.42<MM<1.43 1.43<MM<1.44

Energy dependence of slope parameter b

1.35<MM<1.36 1.36<MM<1.37 1.37<MM<1.38

1.38<MM<1.39 1.39<MM<1.40 1.40<MM<1.41

1.41<MM<1.42 1.42<MM<1.43 1.43<MM<1.44

1.37<MM<1.38 1.38<MM<1.39 1.39<MM<1.40 1.40<MM<1.41 1.41<MM<1.42

2.1<Eg<2.2 2.85896 1.53428 1.70853 1.78659 2.09702

2.2<Eg<2.3 1.93896 2.37078 1.76626 1.51546 1.70541

2.3<Eg<2.4 1.50479 2.93334 2.21105 2.21628 3.36527

b parameter