Search for + via K + p + X r eaction with high-resolution spectrometer system Kyoto University S. Dairaku for E559 collaboration
Jan 27, 2016
Search for + via K+p +X reaction with high-resolution spectrometer syste
m
Kyoto University
S. Dairaku
for E559 collaboration
E559 collaboration
Gifu U. T. Kameyama, K. Nakazawa, T. Watanabe
KEK S. Ishimoto, T. Nagae, H, Noumi, Y. Sato, S. Sawada, M. Sekimoto, S. Suzuki, H. Takahashi, T. Takahashi, N. Tanaka, A. Toyoda
Kyoto U. S. Dairaku, H. Funahashi, K. Imai*, K. Miwa, K. Shoji, M. Hayata,M. Miyabe, M. Niiyama, N. Saito, Y. Seki
Ohio U. K. Hicks, R. Zavislak
Osaka U. S. Ajimura
Osaka EC U. T. Fukuda
RCNP T. Nakano, M. Yosoi
RIKEN M. Naruki, K. Tanida
Tohoku U. S. Kinoshita, T. Koike, Y. Ma, Y. Miura, K. Shirotori, H. Tamura
U. Paris-Sud J. Arvieux
U. Tokyo H. Fujioka, T. Maruta, D. Nakajima, T. N. Takahashi
Purpose
Search for + Pentaquark ( E559 at KEK-PS K6) if + exists, < 1 MeV/c2 (M=1530 1540 MeV/c2)High Resolution spectrometer SKS & K6beamline
⇒resolution : 2.4 MeV/c2 (FWHM)
High statisticsHadronic reaction K+p +X1.2 GeV/c K+ beam and liquid H2 target
Determination of decay angle distributionLarge solid angle Drift Chamber & Range Counter do
wnstream of targetSpin and Parity
K+ (1.2GeV/c)
SKS
K+
+
For π+veto
π+(0.5 0.6 GeV/c)
Solid angle0 60 deg
1.6 T
mass2(GeV/c2)2
+
Setup
Data set
RUN2 ( 2005/12/13 2005/12/28 )
H(K+,+) run @1.2GeV/c for + K+ yield : 2.79x109
Empty target run @1.2GeV/c for B.G.H(+,K+) run @1.1GeV/c for +
RUN1 ( 2005/5/24 2005/7/1 )
H(K+,+) run @1.2GeV/c for + K+ yield : 2.09x109
Empty target run @1.2GeV/c for B.G.H(+,K+) run @1.1GeV/c for +
Resolution for + and
1st run
2nd run
1st run is consistent with 2nd run
Missing mass value
Resolution K6 : p/p = 0.047% (FWHM)SKS : p/p = 0.43% (FWHM)
(simulation) for 2.4 MeV/c2 (FWHM)
M=1189.31 ± 0.03 MeV/c2
=2.03 ± 0.06 MeV/c2
M=1189.33±0.03 MeV/c2
=1.94±0.07 MeV/c2
Mass(GeV/c2)
Mass(GeV/c2)
(simulation) for + 1.98 MeV/c2 (FWHM)This is consistent with real data
Vertex distribution (before B.G. cut)
1st run 2nd run
(K+, +)
(+, +)
vertex z(mm) vertex z(mm)
(K+, +) reaction : large background from K+ decay
(K+, +)
(+, +)
Suppression of K+ decay events(SDC1 analysis cut)
K+
( to SKS )
K+p reaction event
K+
( to SKS )
K+ decay event
SKS
RCSDC1
TargetAerogel
Beam line chamber
K+
SDC2
π+
π+veto
vertex
SDC1 analysis cut
Even charged &Large scattered angle
98.0% of K+ decay events are suppressed (simulation)
70.1% of + production events remain(simulation --- assume isotropic angular distribution)
drift chamber
vertex distribution (after B.G. cut)
16900 event (-30<z<100) 11900 event (-40<z<85)
1st run 2nd run
vertex z(mm)vertex z(mm)
Missing Mass (pX)
1530MeV/c2
=50bisotropic distribution
Assumption
Expected peakunder assumption
Sum of 1st and 2nd runs
Preliminary
Missing Mass (pX)
Preliminary
170 ( 90% C.L. upper limit)
Upper limity)(efficienc
Ktgt NN
N
N Counts(90% C.L.)
Ntgt 5.04x1023
NK+ 4.88x109
Survival rate 0.858
Interaction factor 0.94
K6 efficiency 0.935(K6 tracking)
SKS efficiency 0.953(SdcOut)x0.875(SdcIn)
x0.93(SksTrack)=0.775
SDC1 analysis cut 0.701 ( assume angular distribution )
vertex cut 0.85
Trigger efficiency 0.95(LC)x0.99(TOF)
Acceptance 0.11sr(Laboratory frame)
0.0293(assume angular distribution)
Preliminary
90% C.L. upper limit
90% C.L. upper limit
Cross section of H(K+,π+) reaction
gK*N= + gKNgK*N= - gKNgK*N= 0
W/O F.F. =1.2GeV
Y. Oh et al. Phys. Rev. D 69, 074016
=1MeV
√s=1.89GeV ( E559 exp. )
Cross section of H(K+,π+) reaction
W/O F.F. =1.2GeV
gK*N= + gKNgK*N= - gKNgK*N= 0
Y. Oh et al. Phys. Rev. D 69, 074016
Preliminary
=1MeV
E559 exp. 90% C.L. upper limit
Summary
Search for + via H(K+, +) reaction at KEK-PS K6 beamline
K+ beam yield 4.88x109 reaction event 28800 (after SDC1 cut)
No significant peak (1520 - 1560 MeV/c2) cross section 7.0b, 1.9b/sr
90% C. L. upper limit(assume angular distribution)
much smaller than theoretical value under K* exchange (calculated by Y.Oh )
Preliminary
END
peak at SDC1 position
SDC1
SDC2
Decay
K+ beam
RC
Target
20cm
(K+, +)
(+, +)
SKS Gap
20cm
Vertex collect near SDC1
Background in H(K+,+)reaction
K+ decay event * SKS
K+ 1.000
K+ 0.151
K+ e+e 0.122
K+ 0.129K+p reaction event SKS
K+p K++ +K+n 0.008
K+p +K+n
0.006
K+p K0++ +K0p 0.101
K+p K+p +K0p 0.046
K+p +K0p 0.008
Angle cut study
SKS
TargetK+ π+
1
2K+
nSelection of 2
select kinematics?
No correlation between() and (K+, p)
Simulation
2 (degree)
1 (
degre
e)
SDC1 analysis
• If we assume that + decay is isotropic in center of mass frame, accepted ratio of each decay mode – K+n : 0.637– K0
Sp : 0.729– K0
Lp : 0.804
• Weighted mean with decay ratio ( 0.5:0.25:0.250.701 )→ 0.701
0
10
20
30
40
50
60
-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0
Q2=q2-w2
kaon 1.2GeV/cphoton 2.4GeVphoton 1.8GeVphoton 3.0GeVpion 1.9GeV/c
Q2 of reactions
Q2=q2-2 [GeV2]
Ang
le [
degr
ee]
LEPS
CLAS
E559(K+,)1.2GeV/c
E522(,K)1.9GeV/c