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Document Sample
SFB – TR 16
Plans for
Strangeness Photoproduction at B1
• L(1405) photoproduction
• Double polarisation observables in KL/S
photoproduction
Vera Kleber 06.12.2007 1
Quark Model Predictions: L
Löhring, Metsch, Petry, EPJ A10 (2001) 447
Vera Kleber 06.12.2007 2
Quark Model Predictions: L
Löhring, Metsch, Petry, EPJ A10 (2001) 447
S=1/2
L=1
Vera Kleber 06.12.2007 3
Structure of the L(1405)
large theoretical effort JP=1/2- JP=3/2-
quark model state with orbital excitation
L(1405) L(1520)
→ mass degenerated partner with JP=3/2-
L(1520): 115 MeV away
KN molecule, dynamically generated L(?) L(1520)
→ another JP=1/2- L near the L(1520)
unobserved
double structure @ 1405 MeV a.u.
D. Jido et al.,
Nucl. Phys. A725 (2003) 181
Vera Kleber 06.12.2007 4
Strange Particle…
located close to many thresholds L(1405)
pL p0S0 p+S- K0n
p-S+ K-p Mass
L(1405) S0(1385): similar masses, overlapping due to width
L(1405) → pS (100%) and S(1385) → p+/-S-/+ (12%) / Lp(88%)
Dalitz and Tuan predicted (1959) a
subthreshold KN resonance
R.J. Hemingway,
from K-p scattering data NP B 253 (1985) 742
R.H. Dalitz, A. Deloff,
JPG 17 (1991) 289
→ L(1405) was discovered
a few years later; m(p-S+)
only 30 MeV below KN threshold
Vera Kleber 06.12.2007 5
Access to L(1405)
above KN threshold K-p→K-p
K-p scattering data
J. A. Oller, U.-G. Meissner,
at KN threshold Phys. Lett. B 500 (2001) 263
kaonic hydrogen
below KN threshold
pS mass distribution
Vera Kleber 06.12.2007 6
pS Mass Distribution: LEPS
gp → K+p+/-S-/+
J.K. Ahn, Nucl. Phys. A 721 (2003) 715c
p+S-
cut on
m(X) = m(S)
L(1405) L(1520)
(S(1385))
p-S+
12% 66%
S0(1385) pS (1405)
L
Vera Kleber 06.12.2007 7
pS Mass Distribution: Crystal Ball
S cut and bg
subtraction S. Prakhov et al.,
PRC 70 (2004)
pK-= 034605
K-p → S0p0p0 581 MeV/c
-- phase space
Lg S0 687 MeV/c
L(1405)
p0n
714 MeV/c
L(1520)
→ 7g n
750 MeV/c
Vera Kleber 06.12.2007 8
Two L(1405) Resonances
V.K. Magas et al., Phys.Rev.Lett. 95 (2005) 052301
D. Jido et al., Nucl. Phys. A 725 (2003) 181
Two L(1405):
in experiments superposition is seen
different reactions can pick up
the poles with different strength
Vera Kleber 06.12.2007 9
pS Mass Distribution: ANKE
pp → K+pLX, X=p0g
Thomas
Hemingway
I. Zychor et al., arXiv:0705.1039
Vera Kleber 06.12.2007 10
Plans for L(1405) at CB-ELSA
gp → K+L(1405) → K+n5g
mass distribution S0p0
invariant mass of (S0p0) system or Lg
missing mass of K+ np0
t-distribution
momentum transfer to L(1405)
L(1405)
if t-channel dominant
→ access to pK- scattering amplitude
below threshold
Vera Kleber 06.12.2007 11
Dominant Production Mechanism
L(1405)
M. Lutz, M. Soyeur, Nucl.Phys. A748 (2005) 499-512
Vera Kleber 06.12.2007 12
Planned Setup
gp → K+L(1405) → K+n5g
S0p0
Drift- Momo2 Lg
kammern
Momo 1m np0
Photonen-
strahl
Target
Crystal Barrel
Innendetektor
Aerogel Forward-Plug
Dipol -Cherenkov
TOF-Detektor Zeichnung: Dieter Walther
Vera Kleber 06.12.2007 13
(Double Polarisation) Observables in KY
gp → K+L, gp → K+S, (gp → K0S+)
SAPHIR, CLAS, LEPS, GRAAL + CB
s total cross section Unresolved discrepancies
ds/dW differential angular distributions in absolute normalisation,
shoulder at W=1900 MeV
P recoil polarisation
missing resonance?
S beam asymmetry
(T target asymmetry) double polarisation
observables
Cx, Cz spin transfer coefficients
Vera Kleber 06.12.2007 14
Spin Transfer Coefficients
gp → K+L
(Py2 + Cx2 + Cz2)1/2
Cz
+1
0
-1
cos θKcm cos θKcm
R. Bradford et al., PRC 75 (2007) 035205
Vera Kleber 06.12.2007 15
Reaction Mechanism
• Quark dynamics? • Resonances?
R. Schumacher, A. Anisovich et al.,
nucl-ex/0611035 hep-ph/arXiv:0707.3596v1
good description of data
K+ new P13 with mass around 1900
s
g
s
u s
p
p u
d
u
d
L
S=0 diquark S=0 diquark
Vera Kleber 06.12.2007 16
Reaction Mechanism
• Quark dynamics? • Resonances?
A. Anisovich et al.,
hep-ph/arXiv:0707.3596v1
s good description of data
s
favoured new P13 with mass around 1900
u s
p u u
d d
s
Similar behaviour for other
suppressed double polarisation observables,
u
s
s e.g. Ox, Oz
p u u
d d
Opposite behaviour for K*
photoproduction
Vera Kleber 06.12.2007 17
Identifikation geladener Teilchen
t
[ns] p Simulation
p+ : K+ : p
200 : 1 : 200
K+
s(t) = 0.5 ns
s(p)/p ≈ 1.7%
p+
p [MeV]
Vera Kleber 06.12.2007 18
Identifikation geladener Teilchen
t p < 1000 MeV
[ns] Zeitdifferenz zur
Flugzeit
p+ eines Kaons
p K+
Dt [ns] p < 1300 MeV
K+
p+
p
Dt [ns]
p [MeV]
Vera Kleber 06.12.2007 19
Identifikation geladener Teilchen
t p < 1000 MeV
[ns] Zeitdifferenz zur
p Flugzeit
p+ eines Kaons
K+ mit Veto auf
Cherenkovsignal
Dt [ns] p < 1300 MeV
p
K+ p+
Dt [ns]
p [MeV]
Vera Kleber 06.12.2007 20
K+ Identification – Scenario I
TOF @ 5.3 m
Stefan Höffgen
→ K+ identification up to 600 MeV (black line)
Vera Kleber 06.12.2007 21
Estimate of Total Cross Section
Eg 1.5-2.0 GeV
stot(gp→K+L(1116)) ~ 1mb
stot(gp→K+L(1405))
~ stot(gp→K+S(1385))
IL(1116) : (2•IL(1405)/S(1385))
stot(gp→K+L(1405))
~ 1mb / 4 = 0.25 mb
Vera Kleber 06.12.2007 22
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