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