Λ hypernuclear spectroscopic experiment via (e,e’K+) at JLab

Graduate school of science , Tohoku Univ.Toshiyuki Gogami

JLab Hall-C in May 2009

Contents

• (e,e’K+) experiment• Introduction of JLab E05-115• Development for high multiplicity data

(e,e’K+) reaction experiment

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

JLab E05-115 experiment

E05-115 experimental motivation (1)

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

(CSB) ΛN-ΣN coupling

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

Λ Λ Λ Λ

First try

B Λ [M

eV]

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

A = 52

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

particle energy l ・ s splitting , core configuration

mixing dΛ, fΛ –state

Λ

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

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

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 ≈ 200 [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]

Data Summary

JLab E05-115 (2009/June – 2009/Nov)

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

This talk

Λ and Σ0

Because of high multiplicity of HKS(analysis code cannot handle with high multiplicity)

~40 hours(5 shifts)

p(γ*,K+)Λ,Σ0

Analysis for high multiplicity data

KDC1

KDC2

HKS event display

Background event of HKS

HKS dipole magnet

NMR port

z [cm]

y [cm]

x [cm] KDC1

KDC2

KDC1

KDC2

9Be , 38.4 [μA]Overhead view

Background events

Events on HKS optics

Β ≈ 1e- , e+

SIMULATION

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]

Multiplicity of typical layer of chamberHES HKS

~1.13

~1.28

~2.24

~4.94

Multiplicity is high for HKS

HKS drift chamber wire configuration

Hit wires in KDC1

Overhead viewKDC1

Black : hit wires Blue : selected wiresRed : track

Black : hit wires Blue : selected wiresRed : track

CH2 52Cr

Misidentification chance in hit wires selection increase !

REAL DATA REAL DATA

low high low high

Overhead view

New tracking scheme

Good TDC

Pattern recognition

Track fit

Solve left right

Select good combination

Combination selection with TOF counters

Reduce hit wire combinations (h_tof_pre.f)

High multiplicity

• Hit wire selection with TOF• 1X & 2X • Grouping

• Pre-PID• Cherenkov detectors

Reduce hit wires to analyze

NEW

DC hit info. selection with TOF

Selective region Maximum gradient

Minimum gradient

Particle direction

Gravity

CUT~8%

~17%

Procedure in “h_dc_tofcut.f”1. Get KTOF1X & 2X hit counter information2. Make combination of 1X and 2X hit counter if those two are in

same group (grouping) 3. Determine cut conditions on KDC1 & KDC24. Select Hit wires in KDC and Reorder them

CUT

Hit wires event display (1)

• GREEN regionSelective region

• RED markersSelected hit wires

• BLACK markersRejected hit wires

Seems to work well

Particle direction

Gravity

Apply to u,v-layer

Applied to uu’ and vv’ layers , too.

Selective region determined by 1X and 2X

Convert

v v’-layer

x x’-layer

Hit wires event display (2)

• GREEN region Selective region• RED markers & lines Selected hit wires• BLACK markers & lines Rejected hit wires

v v’ u u’

x x’

v v’ u u’

x x’

KDC1 KDC2particle particle

Results of Introduction new code

Λ c.s. (CH2/H2O) issue is solved

Increased !

Increased !

CH2

52Cr

Summary and Outlook• 3rd generation exp. E05-115 at JLab Hall-C in 2009• 7

ΛHe, 9ΛLi, 10

ΛBe, 12ΛB, 52

ΛV

• Analysis for high multiplicity data– Developed new tracking codeAnalysis efficiency is improved ! (number of event)Λ cross section of H2O and CH2 are consistent

• To get better energy resolution– Fine parameter optimization– Matrix tuning

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