Lambda hypernuclear spectroscopy up to medium heavy mass number
at JLab Hall-C Graduate School of Science, Tohoku University
Toshiyuki Gogami for the HES-HKS collaboration 1. Introduction (
JLab E experiment ) 2. Experimental setup M 2 HY = (E e + M T - E
K+ - E e ) 2 - ( p e - p K+ - p e ) 2 Figure.1 : HES-HKS group
photo in the experimental hall C in JLab (2009). Figure.2 : The
experimental setup of JLab E (2009) Measure with spectrometers 3.
Kaon identification 4. Missing Mass Figure.3 : A photograph of the
HKS detector package NPE Mass square [GeV/c 2 ] 2 ++ 1 [m] K + p, +
K+K+ p ++ p K+K+ Figure.5 : NPE of Cherenkov detector vs. mass
squared Cherenkov detectors -AC,WC- Aerogel (n=1.05) Water (n=1.33)
Drift chambers -KDC1,KDC2- TOF walls -2X,1Y,1X- (Plastic
scintillators) 250 [m] TOF 170 [ps] Aerogel (n=1.05) Water (n=1.33)
Figure.4 : Mass squared distribution Mass squared [GeV/c 2 ] 2
Online + : % K + : 91.3% p : 3.8% 5. Electro-/photo- production of
K + 6. Summary Figure.11 : The differential cross section of K +
production SAPHIR : K.H.Glander et al., Eur. Phys. J. A 19, (2004)
CLAS : R.Bradford et al., Phys. Rev. C 73, (2006) Light to medium
heavy hypernucler spectroscopy , 0, , 7 He, 9 Li, 10 Be, 12 B, and
52 V Clean kaon identification High background rejection efficiency
with low K + loss fraction. Matrix tuning with , 0 and 12 B In
progress not only to get better resolution but also to keep
linearity. K + elementary production data at very forward kaon
angle cos k CM ~ 0.95, W~1.9 GeV, Q 2 ~0.01 [GeV/c] 2 Q 2
dependence p(e,eK + ) ~1.8MeV (FWHM) p(e,eK + ) 0 ~1.8MeV (FWHM) QF
from 12 C JLab E CH 2, ~ 450 [mg/cm 2 ] ~ 2.0 [A] ~ 38 [hours] The
polyethylene target was used as a proton target to optimize energy
scale and to study an elementary process of K + production.
Figure.6 : A missing Mass spectrum of Polyethylene (CH 2 ) target
Figure.7 : Coincidence time between K + s and scattered electrons.
Figure.8 : A missing mass spectrum of 12 C target. 12 C(e,eK + ) 12
B pp ss Preliminary Figure.10 : The differential cross section of
photo-production of K + ( P.Bydzovsky and T.Mart, Phys. Rev. C 76,
(2007) ) Lack of consistency at forward angles High statistical
data have been awaited The matrix tuning is on progress not only to
get better energy resolution but also to keep linearity. NUFRA
Kemer (Antalya), Turkey Light hypernuclei (A 12 ) N-N interaction
Charge symmetry breaking Light hypernuclei (A 12 ) N-N interaction
Charge symmetry breaking Medium heavy hypernuclei (A=52) Mass
dependence of single particle energy s-,p-,d-,f-orbit binding
energy & cross section ls splitting Medium heavy hypernuclei
(A=52) Mass dependence of single particle energy s-,p-,d-,f-orbit
binding energy & cross section ls splitting , 0 Elementary
processes Energy scale calibration , 0 Elementary processes Energy
scale calibration Accidental coincidence Figure.12 : Q 2 dependence
of differential cross section of K + production Offline + : 6.1 % K
+ : 86.7% p : 31.3% 80 : 1 : : 1 : : 1 : Online Offline + : K + : p
x, x, y, Plane p, x, 6 th order transfer matrix Tuned with , 0 and
12 B g.s. 12 C(e,eK + ) 12 B u u d u s s u d p K+K+ e e The (K -, -
), ( +,K + ) reactions Energy resolution ~ a few MeV n The (e,eK +
) reaction Energy resolution ~0.5 MeV (FWHM) p Mirror hypernuclei
Absolute energy scale calibration 1990s (e,eK+) reaction ss 10
B(e,eK + ) 10 Be Figure.9 : A missing mass spectrum of 10 B target.
10 B(e,eK + ) 10 Be Q 2 dependence was also measured and shown in
Fig. 11. It shows no dependence in the Q2 region of 0 ~ [GeV/c]
2
