hypernuclei, – n interaction electroproduction of hypernuclei e94-107 experiment update...

Hypernuclei, – N interaction

Electroproduction of hypernuclei

E94-107 experiment UPDATE

Experimental equipment and setup

Kaon identification RICH detector

Analysis results of 2004 run

Preliminary results of 2005 run

E07-012 proposed experiment

Conclusions

Francesco Cusanno – Hypernuclear Spectroscopy - Hall A Collaboration Meeting, June 22, 2007

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

JLAB Hall A E94107

COLLABORATION


Hypernuclei are bound states of nucleons with a strange baryon (Lambda

hyperon). A hypernucleus is a “laboratory” to study nucleon-hyperon

interaction (-N interaction).

Extension of physics on N-N interaction to system with S0

Internal nuclear shell are not Pauli-blocked for hyperons.

Experimental goals :

Spectroscopy – Excitation Energy – doublet splitting

Information on -N interaction

Hypernuclei


E94107 experiment has taken data in two separate period on 2004. Data have been collected on solid targets. The second part of the experiment is currently running in Hall A using the waterfall target

January 2004 12C target and commissioning of waterfall target

April 2004 12C target and May 2004 9Be

June 2005 Waterfall target for hypernuclear state production on 16O

Approved Experiment E07012 to study the angular dependence of

strangeness electroproduction

Data Taking and Future Plan


“weak coupling model”

(parent nucleus) ( hyperon) (doublet state)21

11 )( AHypA JJshellsJ

N interaction potential:VN = Vo(r) V central

+ V(r) N · (spin-spin)

+ Vso(r) N· (spin-orbit)

+ Vso(r) N· NN(spin-orbit)

+ VT(r) S12 T tensor

9Be

9Li9B

e

9Li excita

tion e

nerg

yHypernuclei and -N interaction

9Be 9Li


Electroproduction of Hypernuclei

e

p

K+

e’

*

N … N

nucleus

Hypernucleus

p

beam

Scattered electronDetected by HRSe

Kaon detected by HRSk

N … N

1 ZKeZe AA 1 ZKeZe AA

High luminosity, high duty cycle, excellent beam energy spread

Better energy resolution than hadronic induced reactions, BUT smaller cross section


Electroproduction of hypernuclei by the reaction:

Nuclear targets and resulting hypernuclei: 9Be 9Li(spin doublets, information on s-s term of -N interaction potential)

12C 12B(comparison with previous data: better understanding of results with hadron

probes and E89-009 in Hall C at Jefferson Lab) 16O 16N(details of the hypernuclear spectrum also depends on single particle

spin-orbit splitting)

Experimental requirements:1. Excellent Energy Resolution (Best performance for Beam and HRS)2. Detection at very forward angles (6° to obtain reasonably high counting

rates septum magnets)

3. Excellent Particle Identification system (PID) for unambiguous kaon selection RICH

E94-107 Experiment:“High Resolution 1p Shell Hypernuclear Spectroscopy”(spokespersons: F. Garibaldi, S. Frullani, J. Le Rose, P. Markowitz, T. Saito – Hall A Coll.)

1 ZKeZe AA 1 ZKeZe AA


SEPTUM magnets in Hall A

FWHM = 1.1x10-4

=20x20 mrad2


Carbon Peaks

Kinematics, Counting rates

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


Hadron identification using Aerogel Threshold Cherenkov detectors

p

k All events

AERO1 n=1.015

AERO2 n=1.055

p

k

ph = 1.7 : 2.5 GeV/c

Protons = A1•A2

Pions = A1•A2

Kaons = A1•A2


KAON Id Requirements physics case

Process Rates

signal Bound states (e,e’K)

10-4 – 10-2

accidentals (e,e’)(e,)

(e,e’)(e,p)(e,e’)(e,k)

1001000.1

Forward angles higher background of and p

TOF and 2 Threshold Cherenkov NOT sufficient for

unambiguous kaon identification

RICH DETECTOR

Signal Vs. Background


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


The RICH detector at Jefferson Lab


Rich – PID – Effect of ‘Kaon selection’:

P

K

Coincidence Time selecting kaons on Aerogels and on RICH:

AERO K AERO K && RICH K

RICH Pion rejection factor ~ 1000


Rich – PID – Effect of ‘Kaon selection’:

PK

Coincidence Time selecting kaons on Aerogels and on RICH:

AERO K AERO K && RICH K

GREATLY improved AEROGEL performance!


Monte Carlo simulation of 12Bexcitation-energy levels produced on 12C target

12C(e,e’K)12B

a cb d

)())((3

(Tensor) )(

orbitspin )(

orbitspin )(

spin)(spin )(

(central)V )(

12

12

0N

NN

T

NNNSO

NSO

N

rrS

TSrV

SrV

SrV

rV

rVV

Absolute and relative positions of “resolved” levels a,b,c,d, may provide information on parameters of interaction potential and its terms (spin-spin, spin-orbit, tensor, …)


Results from 12C target

Analysis of the reaction 12C(e,e’K)12B


Aerogel Kaon selection

RICH Kaon selection

12C(e,e’K)12B12C(e,e’K)12B

Signal

Bckgnd2.5

Signal

Bckgnd 7

Spectroscopy analysis of 12B : Aerogel vs. RICH K-selection


12C(e,e’K)12B12C(e,e’K)12B

635 keV FWHM

Missing energy (MeV)

Results on 12C target – Hypernuclear Spectrum of 12B


Experiment

SLA Model

M. Iodice et al, submitted to Phys Rev Lett, arXiv:0705:3332

Theoretical model for 16Nexcitation-energy on 16O target

The structure of underlying nucleus15N 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

Preliminary Results on WATERFALL target

Analysis of the reaction 16O(e,e’K)16N

and 1H(e,e’K)(elementary reaction)


2005 E-94107: Running on waterfall target

Be windows H2O “foil”

H2O “foil”


2005 E-94107: Preliminary Analysis

1H (e,e’K)1H (e,e’K)

16O(e,e’K)16N16O(e,e’K)16N

Low counting levels above Ethr.

16O(e,e’K)16N

16O(e,e’K)16N


Missing Energy (MeV)

g.s. missing energy: -1.44 0.09 MeV Theor –1.56 MeV

9Be(e,e’K)9Li

a c db

)())((3

(Tensor))(

orbitspin)(

orbitspin)(

spin)(spin)(

(central)V)(

12

12

0N

NN

T

NNNSO

NSO

N

rrS

TSrV

SlrV

SlrV

rV

rVV

Monte Carlo simulation of 9Liexcitation-energy levels

Produced on 9Be target Excitation-energy levels of 9Lihypernucleus, especially from the first-doublet levels a and b,

would provide important information on S and T terms of the N interaction. Separation of c and d doublets may provide information on the spin-orbit term SN


Results on 9Be target

Analysis of the reaction 9Be(e,e’K)9Li

(still preliminary)



Cou

nts

/ 4

00 k

eV

9Be(e,e’K)9Li9Be(e,e’K)9Li

Aerogel Kaon selection

RICH Kaon selection

JLAB Hall A E-94107: Preliminary Results on 9Be target



Cou

nts

/ 2

00 k

eV

Red line: Bennhold-Mart (K MAID)

Blue line: Sagay Saclay-Lyon (SLA)

Curves are normalized on g.s. peak.

Red line: Bennhold-Mart (K MAID)

Blue line: Sagay Saclay-Lyon (SLA)

Curves are normalized on g.s. peak.

JLAB Hall A E-94107: Preliminary Results on 9Be target


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)


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 and 9Be targets (12Band 9Li hypernuclei) have been

taken last year

New experimental equipments showed excellent performance.

The RICH detector performs as expected and it is crucial in the kaon selection.

Submitted paper on 12Ctarget analysisis showing new information on 12B-

interesting comparison with theory for 12B and 9Li.

VERY Promising physics is coming out from preliminary analysis on

16Nhypernuclear spectroscopy

Approved Experiment on angular dependence of strangeness

electroproductionFrancesco Cusanno – Hypernuclear Spectroscopy - Hall A Collaboration Meeting, June 22, 2007

hypernuclei, – n interaction electroproduction of hypernuclei e94-107 experiment update...

Documents

nn interaction

hall c

collaboration meeting

vsor n n n spinorbit

n n high luminosity

n details

aero2 n

v r n spinspin