Spectroscopic Investigation of P-shell Λ

hypernuclei by the (e,e'K+) Reaction

-Analysis Update of the Jlab Experiment

E05115-

Chunhua ChenHampton Universithy

Outline

Experimental Goal of E05115

Kinematics of the E05115

Experimental Setup of E05115

System calibration procedure and status

Preliminary results

Summary and to do

Experimental GoalThe 3rd Generation Hypernuclear Spectroscopy in JLab-HallC

Spectroscopy of Medium - heavy hypernucleus

52Cr(e,e’K+) 52LV

L single particle nature in the mean field

quark picture vs. conventional pictureSpectroscopy of Light L hypernuclei

LN interactions, ls splitting, Charge Symmetry Breaking

p shell hypernuclei : 12C(e,e'K+)12ΛB , 7Li(e,e'K+)7

ΛHe, 10B(e,e'K+)10ΛBe ,

and 9Be(e'K+)9ΛLi

Calibration by the elementary process p(e,e’K+)Λ or Σ: H2O and CH2

Kinematics of the E05-115 Experiment

+p →+K+

Momentum: 2.344GeV/c

Momentum: 0.844GeV/c ±17%Angular acceptance: 3°〜 9°

Momentum: 1.2GeV/c ±12.5%

Angular acceptance : 1°〜 13°

1.5GeV γ*

Scattered electron

K+

Electron beam

Target nucleus

pCoincidence

measurement

Experimental Setup

Splitter Magnet

HKS

HES

PreChicane-SPL-(HKS+HES) Configuration

Experimental Setup -Detector Package-

HES-D

e’

EHOD2

EHOD1

EDC2EDC1

HES Detectors

Calibration Procedure of the Spectrometer System

Forward Tuning

Backward tuning

mass spectroscopy

Nonlinear Least Chi2 fitting

Kinematical scan

Initial state

Magnetic field study

Geant4 Simulation Focal plane pattern

Real Data

Λ & Σ mass spectroscopy

Field map

Focal plane pattern

Matching level A

SS pattern SS hole

Matching level

B

Kinematical parameters

Independent level C

matrices

A&B&C

Forward Optics Tuning

Purple: Real HKS SS data Blue: Geant4 Simulation Splitter field contour on xoz plane

The leakage of splitter fringe field causes the cross talk between the splitter and quadrupoles

Purple: Geant4 simulation green: Real HES SS data

Target

Beam Kaon

Q1

Q2

Forward Optics Tuning

The asymmetry functions are introduced and tuned for HKS&HES quadruple field Bx and By, independently.

The Mass Status of Forward Optics Tuning

Start Point

after forward tuning 11

Backward Calibration Procedure

= = (Ebeam , Pk , xt’k, yt’k , Pe, , xt’e, ,yt’e’ )

(1+δ/100)

Nonlinear least 2 fitting

ΔEbeam0

optimization

Kinematical Calibration

Optical Calibration

MomentumMatrix

AngleMatrix

ΔPK,ΔPe optimization

Beam Energy Scan

iterate

iterate

+

𝜒22=𝜔 Λ (𝜎 Λ

𝑓𝑖𝑡 )2/¿𝜎 Λ>¿2+¿𝜔Σ (𝜎Σ

𝑓𝑖𝑡 )2/¿𝜎 Σ>¿2+𝜔𝑔𝑠(𝜎 𝑔𝑠

𝑓𝑖𝑡 )2/¿𝜎𝑔𝑠>¿2 ¿¿¿¿

gs : 12ΛBgs

Start Point

Fitting Function:Cauchy+pol3

Particle Mean(MeV) FWHM

Λ 0.4495 2.832

Σ0 76.74 3.27

σ~2.7MeV

H2O target Beam Momentum: 2.344GeV/c + 20 MeV/c

FWHM~2.6MeV

Preliminary Status

#1

#2

Peak# Mean(MeV) σ (MeV)

1 -11.39 0.367

2 -0.40 ~1.8

FWHM~1.675MeV

FWHM~1.775MeV

FWHM~1.565MeV

FWHM~2.0MeV

Preliminary Result 7ΛHe

E01011 data

E. Hiyama, et al., PRC53 2078 (1996)

n

n

6He core3/2+&5/2+

Preliminary Result 10ΛBe – 10

ΛBe

3/2-0.00

5.59 3/2-

7/2-6.38

5/2-7.94

2.43 5/2-1/2-2.78

1/2+1.68

5/2+3.04

3/2+4.70

9/2+6.76

Low Lying 9Be Level Structure

1-2-

(< 0.1)10

Be

Missing mass status – 9LLi

Hall A Result(To be published soon)

18

Summary and to do

By current calibration method, we are able to get clear

mass spectroscopy , which is not included in the calibration

data set;

Current resolution is still factor of 2 away from expected

resolution, the iteration will continue to improve the

optical matrices as well as the kinematics;

Other issue: High multiplicity tracking problem for heavy

target data.

19

Back up

New Data Sets

All carbon runs with clear beam current and

nominal beam energy.There are around 414 events in peak #1, and the S/N is around 2.35.

#1

The improvement of the resolution is small with the old

data, since the statistic of 12ΛBgs is small, which is

momentum sensitive .

ProblemSince the improvement of the resolution still small, increase the weight of 12

ΛBgs by factor of 4 on the base of the statistical weight .

7ΛHe Missing Mass

σ ~ 1.0 MeV

Target Straggling

σ~3.2MeV

First turn of optics tune with CH2 Data

1. There is still kinematical parameters dependence of Λ and Σ

(1-2MeV) after forward optical tuning;

2. Counts of 12ΛB from low luminosity data is small, and also its

resolution is bad, the S/N ratio of selected region is small;

σ~2.7MeV

Tune Angle matrix and momentum

matrix at same time

Preliminary Status -7

ΛHe-

E01011 data

Resolution : ~510 keV (FWHM) for g.s.Data taking : ~30 hours w/ 30 mA

Peak # Mean(MeV) σ (MeV)

1 -5.46 0.549

2 -3.94 4.66

Theoretical calculation Binding energy: Hiyama w/o CSB

1/2+ (-BΛ=-5.37)

#1#2

First turn optics tune with CH2 Data

Particle Mean(MeV) FWHM

Λ 0.2098 2.122

Σ0 77.41 2.456

First turn optics tune with CH2 Data

FWHM~2.9MeV

H2O target

FWHM~2.6MeV

H2O target Beam Momentum: 2.344GeV/c + 20 MeV/c

First turn optics tune with CH2 Data

FWHM~2.9MeV

H2O target

FWHM~2.6MeV

H2O target Beam Momentum: 2.344GeV/c + 20 MeV/c

Target Mass Events # above BG S/N

CH2 Λ 9976 3.54

Σ0 2650 1.40

H2O(Pe~2.364) Λ 283 2.96

C12 (BC=20uA) 309 1.61

Data sets

e , e+ background in GEANT simulation

Vacuum chamber(sus304)

NMR port(sus304)

KDC1 KDC2

e- , e+

Generated particle : e+

Distribution : spherical uniform Momentum : 860 – 1000 [MeV/c] Angle : 0 – 2 [mrad] 1000 events

29

e+

HKS

Calibration procedure-Beam Energy Scan-

𝜒12=𝜔 Λ(𝑚 Λ

𝑓𝑖𝑡−𝑚Λ0 )/𝜎 Λ

2+¿𝜔Σ(𝑚Σ𝑓𝑖𝑡−𝑚Σ

0 )/𝜎 Σ2 ¿

𝜒22=𝜔 Λ(𝜎 Λ

𝑓𝑖𝑡)/¿𝜎 Λ>¿2+¿𝜔Σ (𝜎 Σ

𝑓𝑖𝑡)/¿𝜎 Σ>¿2+𝜔𝑔𝑠(𝜎 𝑔𝑠

𝑓𝑖𝑡) /¿𝜎𝑔𝑠>¿2 ¿¿¿¿

ωi:statistic weigth

Coincident

Time: The correlation of HKS target time and HES target time, give us the coincident spectrum:

Real events

Accidental

Ktar

etarcoin TTT '

PID cut is applied and path length has been done

Coincident Trigger Set

HKS :

HKStrigger=(CP)×(K)

CP=(KTOF1X)×(KTOF1Y)×(KTOF2X)

K=WC×

HES:

HEStrigger=(EHODO1)×(EHODO2)

×:AND

COINtrigger=(HKStrigger)×(HEStrigger)

Kinematics of the E05-115 Experiment

Momentum: 2.344GeV/c

Momentum: 0.844GeV/c ±17%Angular acceptance: 3°〜 9°

Momentum: 1.2GeV/c ±12.5%

Angular acceptance : 1°〜 13°

1.5GeV γ*

Scattered electron

K+

Electron beam

M.Q.Tran et al. PLB445 (1998) 20

+p →+K+

Target nucleus

pCoincidence

measurement

Preliminary Status

#1

#2

Peak# Mean(MeV) σ (MeV)

1 -11.39 0.367

2 -0.40 ~1.8

FWHM~1.675MeV

FWHM~1.775MeV

FWHM~1.565MeV

FWHM~2.0MeV

#1 #2

FWHM~1.675MeV

FWHM~1.565MeV

Spectrometer System Calibration-Minimize -

Kinematics calibration: utilizing well known masses of , produced from CH2 , 12

ΛBgs from 12C to determine binding energy to a level of precision ~100keV

Optical calibration: Minimize Chisquare w.r.t reconstruction matrix M by an Nonlinear Least Square method.

Mgs: fitted meanMΛ &MΣ : theoretical dataωi : statistic weigth

𝜒12=𝜔 Λ(𝑚 Λ

𝑓𝑖𝑡−𝑚Λ0 )/𝜎 Λ

2+¿𝜔Σ(𝑚Σ𝑓𝑖𝑡−𝑚Σ

0 )/𝜎 Σ2 ¿

𝜒22=𝜔 Λ(𝜎 Λ

𝑓𝑖𝑡)/¿𝜎 Λ>¿2+¿𝜔Σ (𝜎 Σ

𝑓𝑖𝑡)/¿𝜎 Σ>¿2+𝜔𝑔𝑠(𝜎 𝑔𝑠

𝑓𝑖𝑡) /¿𝜎𝑔𝑠>¿2 ¿¿¿¿

34

35

PreChicane-SPL-(HKS+HES) Configuration

Calibration Data Set

Target CH2 12C H2O

Mass Λ Σ Λ12B Λ

Beam P(MeV/c) ~2.344 ~2.344 2.364

Beam Current(uA) ~2 ~20 ~3.5

38

Mass spectroscopy ofΛ,Σ and 12

ΛB(mean and peak

width)