Photoproduction ofPhotoproduction of KK++ near near thresholdthreshold
►Main features of the reactionMain features of the reaction►KinematicsKinematics►KK++ meson identification meson identification►TAPS calibration for charged particlesTAPS calibration for charged particles►MC simulation conditionsMC simulation conditions►ResultsResults►SummarySummary
V.L. Kashevarov, CB@MAMI Collaboration Meeting, Basel 2006
p p → K→ K++ (1405)(1405)
►((oror**)) mass =mass = 1406.5 MeV 1406.5 MeV► TThreshold =hreshold = 1454.97 MeV 1454.97 MeV► Full width = 50 Full width = 50 2 MeV 2 MeV► decay modes:decay modes: ooo o (33%),(33%), (33%),(33%), (33%)(33%)► FFinal particles to be detected:inal particles to be detected:
(1)(1) KK++ { { oo ( ( oo n n ) ) o o } } 11.9%11.9%
(2)(2) KK++ oo ( ( pp ) ) o o } } 21.1%21.1%
(3)(3) KK++ {{oo p p ) ) 17.2%17.2%
(4)(4) KK++ { { ((++n n ) ) 15.8%15.8%
(5)(5) KK++ nn ) ) 33.3%33.3%
KinematicsKinematics
► = 1455 – 1507 MeV= 1455 – 1507 MeV
Ekin (MeV) (deg) Ekin (MeV) vs (deg)
(1)(1) oo{ { ((o o nn) ) } } oo
Ekin (MeV) vs (deg)
oo
oo nn
(2)(2) oo{ { ( (pp) ) } } oo
Ekin (MeV) vs (deg)
oo
pp
(3)(3) oo p p) )
Ekin (MeV) vs (deg)
oo pp
(4)(4) ((++nn) )
Ekin (MeV) vs (deg)
nn ++
(5)(5) nn) )
Ekin (MeV) vs (deg)
nn ++
KK++ meson identification in TAPSmeson identification in TAPS
Cluster energy (MeV)
Tim
e of
fli
ght (
ns)
TAPS calibration for charged particlesTAPS calibration for charged particles
pp
pp
++
++
Cluster Energy (MeV)
k
in(
MeV
) k
in(
MeV
)
Time of flight (ns)
TAPS calibration for charged particlesTAPS calibration for charged particles
pp
pp
++
++
Cluster Energy (MeV)
k
in(
MeV
) k
in(
MeV
)
Time of flight (ns)
MC simulation conditionsMC simulation conditions
► Endpoint taggerEndpoint tagger: E: E 1455 – 1507 MeV1455 – 1507 MeV
► Tagger bin = 2 MeVTagger bin = 2 MeV► Ladder = 800 kHz (Main tagger from 900 MeV)Ladder = 800 kHz (Main tagger from 900 MeV)► Tagging efficiency = 0.4Tagging efficiency = 0.4► Live time = 60%Live time = 60%► LH2 target length = 5 cmLH2 target length = 5 cm► Front of TAPS – Center of target = 120 cmFront of TAPS – Center of target = 120 cm► Old PID and MWPC, but without any materials in Old PID and MWPC, but without any materials in
forward directionforward direction► No Cherenkov detectorNo Cherenkov detector► Total cross section for 1480 MeV = 100 nbTotal cross section for 1480 MeV = 100 nb
ResultsResults
E K+ = F (E cluster) E K+ = F (ToF) E = 1475 MeV
( K +) M (MeV)
ResultsResults
( K +) M (MeV)
(1)(1)oo o o n nooPartial Partial contributioncontribution0.8% (0.06%)0.8% (0.06%)(2)(2)o o pp
oo1.8% (0.13%)1.8% (0.13%)
(3)(3) KK++ {{oo p p ) ) 44.8% (0.25%).8% (0.25%)
(4)(4) KK++ { { ((++n n ) ) nn 2.8% (0.45%) 10.2% (0.9%)10.2% (0.9%)
Results : InvMassResults : InvMass
(on ) o ( o n ) * ( o n o )
(1)(1)oo o o nnooPartial Partial contributioncontribution0.6% 0.6% (2)(2)o o pp
oo0.8%0.8% 1.4% 1.4%
(p ) o ( p ) * ( p o )
Results : InvMassResults : InvMass(3)(3) KK++ {{oo p p ) ) 22.4% .4%
(4)(4) KK++ { { ((++nn ) ) nn 4.2% 6.6% 6.6%
+ ( n) + n n * (
n)
+ ( o p) * ( o
p)
SummarySummary
► The best way for investigation of the reaction is to The best way for investigation of the reaction is to measure MM( measure MM( ,K ,K++););
► Coincidences between KCoincidences between K++ and two or three final and two or three final state particles are needed to suppress background;state particles are needed to suppress background;
► Endpoint tagger would be very useful;Endpoint tagger would be very useful;► TAPS detector allows to do a good identification of TAPS detector allows to do a good identification of
KK++ mesons for cluster size < 3 and cluster energy < mesons for cluster size < 3 and cluster energy < 200 MeV;200 MeV;
► Missing mass resolution: 25 MeV;Missing mass resolution: 25 MeV;► Detection efficiency: 10.2 %;Detection efficiency: 10.2 %;► Expected yield: 0.1 events/nb/h.Expected yield: 0.1 events/nb/h.
Recommended
