Strangeness 2010 at KEK

JLab における (e,e'K+) 反応を用いた精密ラムダハイパー核分光実験

東北大学理学研究科後神　利志Toshiyuki Gogami

June2009 @ JLab Hall-C

Strangeness 2010 at KEK

Contents• Introduction– (e,e’K+)– JLab , CEBAF

• JLab E05-115 experiment– Motivation– Setup– Analysis

• Summary

Spectroscopic experiment via (e,e’K+) reaction

pn

γ*

ΛK+

e-

e + p ➝ e’ + K+ + Λe e

M2HY = (Ee + MT - EK+ - Ee’)2 - ( pe - pK+ - pe’)2

measuretarget nucleus

Feynman diagram

uud

ussud

–p K+

Λ

γ*

Missing mass :

•Binding energy•Cross section

(e,e’K+) reaction

uud

ussud

e e

–p K+

Λ

γ*

ud

ddu

us

sdu

– –π+

Λn

us

ddu

ud

sdu

–K-

Λn

–π-

e + p ➝ e + K+ + Λ π+ + n ➝ K+ + Λ

K+

K- + n ➝ π- + Λ(π+ , K+) (K- , π-)(e,e’K+)

Momentum transfer(Typical )

~300 [MeV/c] ~300 [MeV/c] ~90 [MeV/c]

Λ’s SpinAt forward angle

Λ’s from proton neutron neutron

flip ≈ non-flip non-flip non-flip

Beam primary secondary secondary

Target Thin (~100 mg/cm2)(Isotopically enriched) Thick(> a few [g/cm2] ) Thick(> a few [g/cm2] )

Reaction

Λ can be bounded in deeper orbit

Spin dependent structure

Mirror lambda hypernuclei

High quality , high intensity

Fine structureEnergy resolution

(FWHM)≤ 500 [keV] 1 – 3 [MeV] 1 – 3 [MeV]

JLab CEBAF ( Continuance Electron Beam Accelerator Facility )

• (e,e’K+) experiment1. Coincidence experiment (K+ and e-)2. Small cross section ( ~100 [nb/sr] ) 1/10003. Energy resolution sub MeV (FWHM)

22nd Indian-summer school (SNP2010)100 [m]

Maximum beam energy 6.0[GeV]

Maximum beam intensity 200[μA/Hall]

Beam emittance ~2 [mm ・ μrad]Beam energy spread <1×10-4

Beam bunch interval ~2[ns] (499[MHz])

• Requirement for accelerator1. high duty factor2. high intensity3. small emittance small ΔE/E

CEBAF can satisfythese requirements

Thomas Jefferson National Accelerator Facility

Strangeness 2010 at KEK

(e,e’K+) experiment in JLab Hall-C2000 年

1st generation exp. JLab E89-009ENGE(e’) + SOS(K+)

12ΛB

~ 900 [keV] (FWHM)

2005 年 2nd generation exp. JLab E01-011ENGE(e’) + HKS(K+) + Tilt method

7ΛHe,12

ΛB,28ΛAl

~ 500 [keV] (FWHM)

2009 年 3rd generation exp. JLab E05-115HES(e’) + HKS(K+) + Tilt method

7ΛHe,9

ΛLi,10ΛBe, 12

ΛB,52ΛV

≤ 500 [keV] (FWHM)

Luminosity ×137e’ rate 1/200S/N ×2.7

Proof of feasibility

Establish exp. method

Medium heavy

E05-115 experimental motivation (1)

• p-shell(7He , 9Li , 10Be , 12B) Charge symmetry breaking Λ-Σ coupling

• Medium heavy (52V) s-,p-,d-,f-orbit binding energy & cross section Mass dependence of Λ single

particle energy l ・s splitting　∝ 2l+1

•2009 Aug – Nov @ JLab Hall-C•(e,e’K+) reaction•Target : 7Li , 9Be , 10B , 12C , 52Cr

Λ Λ Λ Λ

Λ

First try

B Λ [M

eV]

It is difficult experimentally.“ b.g. electron due to brems. ~Z∝ 2 “

A = 52

E05-115 experimental motivation(2)

22nd Indian-summer school (SNP2010)

s

p d f

Photo- and electro production of medium mass Λ-hypernuclei ,P.Bydzovsky et al. (2008)

FULL(8)1f7/2

1d3/2FULL(4) FULL(4)・・・・・・sn = 28 p = 24p

d

f

4-

5+

6-

7+

3-

4+

5-

6+

Λ52ΛV

52Cr

or

or

or

or

ls splitting 2l+1∝

• ls splitting • Core excited

Strangeness 2010 at KEK

JLab E05-115 experimental setup

2×10-4

7 [msr]3 – 12 [deg] 2×10-4

11 [msr]2 – 12 [deg]

e + p → e’ + Λ + K+

7Li , 9Be , 10B , 12C , 52Cr

HKS detectors

Strangeness 2010 at KEK

K+

p, π+

Drift chambers-KDC1,KDC2-TOF walls -2X,1Y,1X-

(Plastic scintillators)

Cherenkov detectors -AC,WC-• Aerogel (n=1.05)• Water (n=1.33)

1 [m] June 2009 in JLab Hall-C

HKS trigger• CP = 1X ×1Y × 2X • K = WC × AC

CP × K

~18 [kHz](8 [μA] on 52Cr)

−π+

K+

p

σ ≈ 250 [μm]TOF σ ≈ 170 [ps]

Strangeness 2010 at KEK

HES DetectorsDrift chambers- EDC1 , EDC2 -

TOF walls - EH1 , EH2 - (Plastic scintillators)

HES D magnet

HES triggerEH1 × EH2

~2 [MHz](8 [μA] on 52Cr)e

Time Of Flight

σ ~ 300 [ps]

Target Hypernucleus Thickness[mg/cm2]

Beam Typical rateHES/HKS/COIN

[kHz]Current [μA] Total charge[C]

7Li 7He 184.0 32.0 4.84 2000 / 7 / 0.9

9Be 9Li 188.1 38.3 5.33 2400 / 9 / 1.6

10B 10Be 56.1 38.7 6.25 1300 / 1 / 0.1

12C 12B 112.5 26.8 5.90 1200 / 5 / 1.0

52Cr 52V 134.0154.0

7.6 0.835.53

2000 / 17 / 1.8

Data summary

22nd Indian-summer school (SNP2010)

Λ

Λ

Λ

Λ

Λ

E05-115 ( 2009 Aug – Nov )

Target Hypernucleus Thickness[mg/cm2]

Beam

Current[μA] Total charge[C]

CH2 Λ , Σ0 450.8 2.0 0.28

H2O Λ , Σ0 ~500.0 2.7 0.20

Physics Data

Calibration Data

(@36μA)

Analysis process

trackingx , x’ , y , y’ at Reference plane

x’ , y’ , pat target

Missing Mass

trackingx , x’ , y , y’ at Reference plane

x’ , y’ , pat target

p : Λ , Σ0 ,12ΛB

Angle : Sieve slit

F2T functionF2T function

particle ID(select K+)

HKSHES

tune tune

450.8 [mg/cm2]2.0 [μA]38 [hours]

σ = 2 [MeV/c2](NOT TUNED)

p(e,e’K+)Λ

p(e,e’K+)Σ0

Strangeness 2010 at KEK

Tracking for high multiplicity

CH2 target

particleCH2 target

mean ~ 2 hit

52Cr target

mean ~ 6 hit

52Cr target

particle KDC1 trackingBlue : selected wiresBlack: hit wires

Multiplicity of typical layer

Multiplicity

Trac

king

eff.

52CrCH2

Developing new code

Traditional JLab Hall-C tracking code cannot handle with high multiplicity data.

Summary• 3rd generation exp. E05-115 experiment– 2009 Aug – Nov @JLab Hall C– 7He,9Li,10Be,12B,52V– Spectrometers and Detectors work well– Now analyzing• Tracking for high multiplicity

first try to measure Λ-hypernucleiup to A=52 via (e,e’K+)Λ Λ ΛΛΛ

Strangeness 2010 at KEK

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