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Photoproduction of K + L(1405) near threshold. Main features of the reaction Kinematics K + meson identification TAPS calibration for charged particles MC simulation conditions Results Summary. V.L. Kashevarov, CB@MAMI Collaboration Meeting, Basel 2006. g p → K + L (1405).
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Photoproduction ofK+L(1405)near threshold • Main features of the reaction • Kinematics • K+ meson identification • TAPS calibration for charged particles • MC simulation conditions • Results • Summary V.L. Kashevarov, CB@MAMI Collaboration Meeting, Basel 2006
g p → K+L(1405) • L(1405) (or L*)mass = 1406.5 MeV • Threshold = 1454.97 MeV • Full width = 50 2 MeV • L*decay modes:So po (33%),S+p- (33%),S- p+ (33%) • Final particles to be detected: (1)K+L* { So [L ( po n ) g ]po } 11.9% (2)K+L* {So [L ( p-p ) g ]po } 21.1% (3)K+L* { S+ ( p o p ) p- } 17.2% (4)K+L*{ S+(p+n ) p- } 15.8% (5)K+L* { S- ( p-n ) p+ } 33.3%
Kinematics • E g= 1455 – 1507 MeV K+ Ekin (MeV) Q (deg) Ekin (MeV) vs Q (deg)
(1)So{ L (po n) g} po g po n po Ekin (MeV) vs Q (deg)
(2)So{ L (p- p) g} po po g p p- Ekin (MeV) vs Q (deg)
(3)S+ (p o p) p- po p- p Ekin (MeV) vs Q (deg)
(4)S+(p+n) p- p- p+ n Ekin (MeV) vs Q (deg)
(5)S- (p-n) p+ p+ p- n Ekin (MeV) vs Q (deg)
K+meson identification in TAPS Time of flight (ns) Cluster energy (MeV)
TAPS calibration for charged particles K+ E kin(MeV) p p+ Cluster Energy (MeV) p+ p K+ E kin(MeV) Time of flight (ns)
TAPS calibration for charged particles K+ E kin(MeV) p p+ Cluster Energy (MeV) p+ p K+ E kin(MeV) Time of flight (ns)
MC simulation conditions • Endpoint tagger: Eg = 1455 – 1507 MeV • Tagger bin = 2 MeV • Ladder = 800 kHz (Main tagger from 900 MeV) • Tagging efficiency = 0.4 • Live time = 60% • LH2 target length = 5 cm • Front of TAPS – Center of target = 120 cm • Old PID and MWPC, but without any materials in forward direction • No Cherenkov detector • Total cross section for 1480 MeV = 100 nb
Results E K+ = F (E cluster) E K+ = F (ToF) E g = 1475 MeV MM ( g, K +) - M L*(MeV)
Results (1)K+ L* { So[ L ( p o n ) g ] p o} Partial contribution = 0.8% (0.06%) (2)K+ L* { So [ L ( p -p) g ] p o} 1.8% (0.13%) (3)K+L* { S+ ( p o p ) p- } 4.8% (0.25%) (4)K+L*{ S+(p+n ) p- } + (5)K+ L* { S- ( p -n) p+}2.8% (0.45%) 10.2% (0.9%) MM ( g, K +) - M L*(MeV)
Results : InvMass (1)K+ L* { So[ L ( p on ) g ] p o} Partial contribution = 0.6% (2)K+ L* { So [ L ( p -p) g ] p o} 0.8% 1.4% L ( pon ) So ( po n g ) L* ( po n g po ) L ( p-p ) So ( p- p g ) L* ( p-p g po )
Results : InvMass (3)K+L* { S+ ( p o p ) p- } 2.4% (4)K+L*{ S+(p+n) p-} + (5)K+ L* {S- ( p -n)p+}4.2% 6.6% S+ ( po p) L* ( po p p-) S+ ( p+ n) + S- ( p -n ) L* ( p+n p-)
Summary • The best way for investigation of the reaction is to measure MM( g ,K+); • Coincidences between K+ and two or three final state particles are needed to suppress background; • Endpoint tagger would be very useful; • TAPS detector allows to do a good identification of K+ mesons for cluster size < 3 and cluster energy < 200 MeV; • Missing mass resolution: 25 MeV; • Detection efficiency: 10.2 %; • Expected yield: 0.1 events/nb/h.