high resolution 1p shell hypernuclear spectroscopy at jlab, hall a

Electroproduction of hypernuclei

E94-107 experiment in Hall A

Experimental equipment and setup

Analysis results of 2004 run on 12C

Preliminary results of 2005 run on 16O Future (experiment E07-012)

Conclusions G.M. UrciuoliINFN Roma III (Italy)

Hall A

High resolution, high yield, and

systematic study is essential

Improving energy

resolution

using electromagneti

c probe

and635 KeV

BNL 3 MeV(FWHM)

KEK336 2 MeV(FWHM)

≤ 500 KeV

1.45 MeV(FWHM)

G. M. Urciuoli INPC2007

A.Acha, H.Breuer, C.C.Chang, E.Cisbani, F.Cusanno, C.J.DeJager, R. De Leo,

R.Feuerbach, S.Frullani, F.Garibaldi*, D.Higinbotham, M.Iodice, L.Lagamba,

J.LeRose, P.Markowitz, S.Marrone, R.Michaels, Y.Qiang, B.Reitz, G.M.Urciuoli,

B.Wojtsekhowski

And the Hall A Collaboration

JLAB Hall A E94107

COLLABORATION


Present status of Hypernuclear Spectroscopy

O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys, in press.

(e,e’K+)

16N

This exp. E94-107


Hall A at Jefferson Lab

e- Source

Hall A

JLAB Hall A Experimental setupThe two High Resolution Spectrometer (HRS) in Hall A @ JLab

Beam energy: 4.0, 3.7 GeVE/E : 2.5 10-5

Beam current: 10 - 100 ATargets : 12C, 9Be, 16O Run Time : approx 6 weeks

HRS – QQDQ main characteristics:Momentum range: 0.3, 4.0 GeV/cp/p (FWHM): 10-4

Momentum accept.: ± 5 % Solid angle: 5 – 6 msrMinimum Angle : 12.5°


• Detection at very forward angle to obtain reasonable counting rate

(increase photon flux) Septum magnets at 6°

• Excellent ParticleIDentification system for unambiguous kaon selection

over a large background of p, RICH

• Accurate monitoring of many parameters over a long period of data taking : Beam energy spread and absolute calibration, spectrometers settings and stability, …

• Excellent energy resolution Best performance for beam and HRS+Septa

with accurate optics calibrations

Experimental requirements :

1. Ebeam/E : 2.5 x 10-5

2. P/P (HRS + septum) ~ 10-4

3. Straggling, energy loss…

Excitation energy resolution ≤ 600 keV


Ebeam = 4.016 — 3.777 — 3.656 GeV

Pe= 1.80 — 1.56 — 1.44 GeV/c

Pk= 1.96 GeV/c

e = K = 6°

= E 2.2 GeV – Q2 = 0.079 (GeV/c)2

Beam current : 100 A Target thickness : ~100 mg/cm2

Counting Rates ~ 0.1 – 10 counts/peak/hour

Kinematics, Counting rates

e beam


Septum Magnets

Electrons scatteredat 6 deg sent to theHRS at 12.5 deg.

•Superconducting magnets

•Commissioned 2003-4

RICH detector – C6F14/CsI proximity focusing RICH

Ch“MIP”

Performances: Np.e. # of detected photons (p.e.)and (angular resolution)

..

..

ep

ep

Nc

Cherenkov angle resolution

Separation Power

c n12


Rich – PID – Effect of ‘Kaon selection’:

P

K

Coincidence Time selecting kaons on Aerogels and on RICH:

AERO K AERO K && RICH K

Pion rejection factor ~ 1000


What do we learn from hypernuclear spectroscopy Hypernuclei and the -N interaction

“weak coupling model”

(parent nucleus) ( hyperon) (doublet state)

JA 1 (s shell) JHyp JA 1 12

VN = V0(r) + V (r)s

s N + V (r)

N

s + VN (r)

N

s N + VT (r)S12

S SNT

J 12

J

J 12

(A-1)A

SN

, S , T

Split by N spindependent interaction

HypernuclearFine Structure

Low-lying levels of Hypernuclei

Each of the 5 radial integral (V, , S, SN, T) can be phenomenologically determined from the low lying level structure of p-shell hypernuclei

V


Red line: Fit to the dataBlue line: Theoretical curve: Sagay Saclay-Lyon (SLA) used for the elementary K- electroproduction on proton.Hypernuclear wave function obtained by M.Sotona and J.Millener

Red line: Fit to the dataBlue line: Theoretical curve: Sagay Saclay-Lyon (SLA) used for the elementary K- electroproduction on proton.Hypernuclear wave function obtained by M.Sotona and J.Millener

Results on 12C target – Hypernuclear Spectrum of 12B

12C(e,e’K)12B12C(e,e’K)12B

- energy resolution ~ 635 KeV, the best achieved in hypernuclear production experiments

- first clear evidence of excited core states at ~2.5 and 6.5 MeV with high statistical significance

- the width of the strong ppeak and the distribution of strength within several MeV on either side of this peak can put constraints on the hypernuclear structure calculations

- hint for a peak at 9.65 MeV excitation energy (admixture)

Results on 12C target – Conclusion

2005 E-94107: Running on waterfall target

Be windows H2O “foil”

H2O “foil”


Theoretical model for 16Nexcitation-energy on 16O target

The structure of underlying nucleus 15N is dominated by:

(i) J=1/2-proton-hole state in 0p1/2 shell - ground state

(ii) J=3/2- proton-hole state in 0p3/2 shell - Excited states at Ex = 6.32 MeV

Details of the hypernuclear spectrum at Ex ~ 17-20 MeV depends not only on -N residual interaction but also on the single particle spin-orbit splitting (difference in energy of 0p3/2 and 0p1/2 states)

Coupling of

p1/2 and p3/2

16O(e,e’K)16N

15N energy spectrum 16N energy spectrum

Analysis on 16N spectrum : FIT to the data


The Angular Dependence of 16O(e, e K) 16N and H(e,e K+)

- hypernuclear physics

- the electromagnetic approach

- recent results

- motivation

- the elementary reaction

- angular distribution

- the apparatus

- kinematics and counting rates

- beam time request

- summary and conclusion

proposal for PAC 31 (F. Garibaldi January 0507 - Hall A Collaboration meeting - Jlab)

the proposed experiment will answer the following the proposed experiment will answer the following questionsquestions

• does the cross section for the photo-production continue in rising as the kaon angle goes to zero or is there a plateau or even a dip like for the high-energy data?(relationship with CLASS data)

• is the concept of the hadronic form factors as it is used in the isobaric models still correct? What is the angular dependence of the hypernuclear form factor at forward angle?

. is the hypernuclear angular dependence the same as the hypernuclear process?

• which of the models describes better the reality at forward angles and can be therefore used in analysis of hypernuclear data without introducing an additional uncertainty?

. the success of the previous experiment (very “clean” (background free) data) guarantees for the experimental equipment (optics, PID), analysis, rates (beam time) evaluation to be under control. (extrapolations “easy”).

“unique possibility” for this experiment in Hall A with waterfall target, septa and PID

these questions arethese questions are very important for our very important for our understanding of dynamicsunderstanding of dynamics of the of the process and process and vitalvital for the hypernuclear calculations and for the hypernuclear calculations and interpretation of the data, interpretation of the data, they urgethey urge to be answered also for “building” the to be answered also for “building” the hypernuclear program at Jlab in hypernuclear program at Jlab in the futurethe future

Conclusions:

Experiment E94-107 at Jefferson Lab: GOAL is to carry out a systematic study

of light hypernuclei (shell-p).

The experiment required important modifications on the Hall A apparatus.

Good quality data on 12C, 9Be and 16O targets (12B9Li and 16N hypernuclei)

have been taken

New experimental equipments showed excellent performance.

The RICH detector performed as expected and it is crucial in the kaon

selection.

Analysis of data on 12Ctargetshowed new information on the spectroscopy of

the 12Bhypernucleus

VERY Promising physics is coming out from new data on the waterfall target

for 16Nhypernuclear spectroscopy - also for p(e,e’K)X-Sect. measurementG. M. Urciuoli INPC2007

16O(e,e’K)16N16O(e,e’K)16N

E94-107 Hall A Experiment Vs. KEK-E336

16O(,K+)16O16O(,K+)16O

Mauro Iodice – XLIV Meeting on Nucl. Phys. - Bormio06, Italy - January 29 - February 5, 2006

16O(e,e’K)16N16O(e,e’K)16N

E94-107 Hall A Experiment Vs. -ray spectroscopy at BNL

16O(K-, ) 16O16O(K-, ) 16O


high resolution 1p shell hypernuclear spectroscopy at jlab, hall a

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