JLab における中重ラムダハイパー核分光研究東北大学理学研究科 後神　利志

Contents

• Introduction• Experimental setup• Analyses• Missing mass• Summary

Contents

• Introduction• Experimental setup• Analyses• Missing mass• Summary e e

uud

ussud

–p K+

Λ

γ*

(e,e’K+) reaction

Spectroscopic experiment by the (e,e’K+) reaction

pn

γ*

ΛK+

e-

e + p ➝ e’ + K+ + Λ

target nucleus

~ 1990’s The (K-,π-) , (π+,K+) reactions• Energy resolution ~ a few MeV• n Λ

e’-Spectrometer

K+-Spectrometer

pe’

pK+

Coincidence Missing Mass MHY

2000~The (e,e’K+) reaction• Energy resolution ~0.5 MeV• p Λ

Experimental motivation• JLab E05-115 (2009, Hall-C)– Elementary processes (Λ,Σ0)– 7

ΛHe[1], 9ΛLi, 10

ΛBe• ΛN charge symmetry breaking• ΛN-ΣN coupling

– 12ΛB[2][3][4]

• Consistency check with the past experiments• Check analysis progress

– 52ΛV• Single particle energy • For measurements with heavier targets

[1] S.N.Nakamura et al., PRL 110, 012502 (2013)[2] T.Miyoshi et al., PRL 90, 232502 (2003)[3] L.Yuan, PRC 73, 044607 (2006)[4] M.Iodice, PRL 99, 052501 (2007)

Contents

• Introduction• Experimental setup• Analyses• Missing mass• Summary

HES

Experimental setup

10 msr

10 msr

Contents

• Introduction• Experimental setup• Analyses• Missing mass• Summary

Analysis

Analysis

x, x’, y, y’x, x’, y, y’

p, x’, y’p, x’, y’

@ Reference plane @ Reference plane

@ Target

Missing Mass

Energy scale calibration

x, x’, y, y’ @ RP

e, K+

p, x’, y’@ Target

Inverse transfer matrix

Polyethylene target (0.45 g/cm2)

FWHM ~ 1.8 MeV

Background events in the HKS

z [cm]

y [cm]

x [cm] KDC1

KDC2

KDC1

KDC2

9Be , 38.4 [μA]REAL DATA SIMULATION

e+

• 52Cr target– Luminosity ( 1/10 )– Worse S/N – Tracking is not easy

Tracking efficiency and residual

σ ~ 160 μm

Plane efficiency Tracking residual

σ ~ 350 μm

Contents

• Introduction• Experimental setup• Analyses• Missing mass• Summary

10ΛBe, 12

ΛB histograms

NsΛ~190

12C(e,e’K+)12ΛB10B(e,e’K+)10

ΛBe

sΛ

pΛ

FWHM~0.9 MeVFWHM~0.9 MeV

Accidental BackgroundAccidental Background

Quasi-free ΛQuasi-free Λ

NsΛ~530

sΛ

Preliminary Preliminary

52Cr(e,e’K+)52ΛV

Preliminary

Accidental Background

Quasi-free Λ

Nbind~870

Summary and outlook

• JLab E05-115 (2009)– Λ, Σ0, 7

ΛHe, 9ΛLi, 10

ΛBe, 12ΛB, 52

ΛV– Analyses are in progress• Matrix tuning• Blind analysis• Efficiencies

E05-115 collaboraton

Backup

Hit wire selection

REAL DATA

Black : hit wires Blue : selected wiresRed : track

52Cr Target

REAL DATACH2 Target

Compared to the conventional codeNumber of K+ +130%Analysis time – 30%

CUT

CUT

軽い核のミッシングマス

数、分解能

JLab E05-115, Carbon (112mg/cm2)

10LBe

Energy scale calibrationAngle, position @ FP

e, K+

Angle, momentum @ Target

6th order transfer matrix

conversion

Mx – MΛ < 100 keV/c2

トラッキング困難REAL DATA REAL DATA

Black : hit wires Blue : selected wiresRed : track

CH2 Target H2O Target

52LV

Singles rate summaryUp to ~30 [MHz]

Up to ~15 [MHz]HES

HKS

HKS trigger ~ 10[kHz]

HES trigger ~ a few[MHz]

COIN 2.0 [kHz]

HKS-HES Collaboration Meeting, T.Gogami 25

B.G. mix rate (real data)

ab

B.G mix rate =

* hks ntulpeHKS-HES Collaboration Meeting, T.Gogami 26

e+ simulation

SIMULATION

• To see 1. Number of event2. Angle & momentum

of e+ generated in target

HKS-HES Collaboration Meeting, T.Gogami 27

Spectroscopic experiment by the (e,e’K+) reaction

pn

γ*

ΛK+

e-

e + p ➝ e’ + K+ + Λe e

target nucleus

Feynman diagram

uud

ussud

–p K+

Λ

γ*

~ 1990’s The (K-,π-) , (π+,K+) reactions• Energy resolution ~ a few MeV• n Λ

e’-Spectrometer

K+-Spectrometer

pe’

pK+

Coincidence Missing Mass HHY

28

2000~The (e,e’K+) reaction• Energy resolution ~0.5 MeV• p Λ

2012/9/14 JPS meeting in Kyoto , Toshi Gogami

Background events in the HKS

z [cm]

y [cm]

x [cm] KDC1

KDC2

KDC1

KDC2

9Be , 38.4 [μA]REAL DATA SIMULATION

~2.24

~4.94

e+

• 52Cr target– Luminosity ( 1/10 )– Worse S/N – Tracking is not easy

10ΛBe, 12

ΛB histograms

NsΛ~190

12C(e,e’K+)12ΛB10B(e,e’K+)10

ΛBe

sΛ

pΛ

FWHM~0.9 MeVFWHM~0.9 MeV

Accidental BackgroundAccidental Background

Quasi-free ΛQuasi-free Λ

NsΛ~530

sΛ

Preliminary Preliminary

Experimental motivation• JLab E05-115 (2009, Hall-C)– Elementary processes (Λ,Σ0)– 7

ΛHe[1], 9ΛLi, 10

ΛBe• ΛN charge symmetry breaking• ΛN-ΣN coupling

– 12ΛB• Consistency check with the past experiments• Check analysis progress

– 52ΛV• Single particle energy (systematic な study)• ls splitting, core-configuration mixing• 将来重く行くため避けられない道

[1] S.N.Nakamura et al., PRL 110, 012502 (2013)

Detectors & TriggerK+

p, π+e-

Drift chambers

TOF walls (Plastic scintillators)

Cherenkov detectors • Aerogel (n=1.05)• Water (n=1.33)

HESHKS

HKS trigger(TOF1x2x3) x Chrenkov

~10 kHz

HES trigger(TOF1x2)

~2000 kHz

Coincidence triggerHES x HKS

< 2 kHz2012/10/6 Core2Core in Barcelona, Toshi Gogami 32

52Cr(e,e’K+)52ΛV

Mixed event analysis をやるs

pd

f

数 Preliminary