Hypernuclear Spectroscopy in Hall-A at JLAB

Electroproduction of hypernuclei.

E94-107 experiment.

Experimental equipment and setup

Kaon identification RICH detector: 2004 vs 2005

Analysis results of C data.

Preliminary results of Be, O and H.

ConclusionsS. Marrone – Indian-Summer School, Rez, Prague 3-7 October 2006

S. Marrone on behalf of E94-107 Collaboration.Dipartimento di Fisica and INFN, Bari.

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 E94-107

COLLABORATION(spokespersons: F. Garibaldi, S. Frullani,

J. Le Rose, P. Markowitz, T. Saito)

S. Marrone – Indian-Summer School, Rez, Prague 3-7 October 2006

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 obtained at CEBAF in Hall-A.

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

+e p e K +e p e K


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 ) -> 1H(e,e’K) for free because of the waterfall target.

Experimental requirements:1. Excellent Energy Resolution: Best performances ever obtained for Beam and

High Resolution Spectrometer in Hall-A.

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”

1 ZKeZe AA 1 ZKeZe AA


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


Hall A - Two High Resolution SpectrometersHall A - Two High Resolution SpectrometersQDQ - Momentum Range: 0.3 –4 GeV/c p/p : 1 x 10-4 – p = =-5% - –mr

Hadron Arm:3 Scintillators for

trigger,VDC for tracking,

2 Cherenkov Aerogels

+ RICHfor PID

In this case the PID is between /K/p .

Two High Resolution Spectrometers (HRS).

Electron Arm: 3 Scintillators for Triggers;VDC for tracking;

/e GAS Cherenkov for PIDShower and Preshower for PID.

SEPTUM Magnets in Hall A

FWHM = 1.1x10-4

=20x20 mr2Before optimization

After optimization

Septa

Minimal angle between two HRS = 12°.

We need 6° to get a high cross section.

We use two more magnets to bend the particles, the SEPTA.

Optimixed the transfer matrix of the HRS with the Carbon elastic.

12°


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


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

Pion rejection factor ~ 1000


Rich – PID – Effect of ‘Kaon selection’:

PK

Coincidence Time selecting kaons on Aerogels and on RICH, after solving the Aerogel problems.

AERO K AERO K && RICH K

GREATLY improved AEROGEL performance!


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

650 keV FWHM

Missing energy (MeV)

Results on 12C target – Hypernuclear Spectrum of 12B

g.s.


JLAB Hall A E94-107: preliminary comparison with theory for 12Bhypernucleus


Cou

nts

/ 2

00 k

eV 12C(e,e’K)12B

12C(e,e’K)12BTwo theoretical curves (blue and red), two different model for the elementary K- production on proton.

Same hypernuclear wave-function (by Miloslav Sotona).

Red line: Bennhold-Mart (K MAID)

Blue line: Sagay Saclay-Lyon (SLA).

Curves are normalized on g.s. peak.

RESOLUTION: 650 keV FWHM.

Two theoretical curves (blue and red), two different model for the elementary K- production on proton.





RESOLUTION: 650 keV FWHM.

The relative intensity of first excited-core peak at 2.6 MeV and strongly populated p-Lambda peak at 11 MeV would be better described by K MAID model than SLA. SLA viceversa reproduces better the last peak.

The relative intensity of first excited-core peak at 2.6 MeV and strongly populated p-Lambda peak at 11 MeV would be better described by K MAID model than SLA. SLA viceversa reproduces better the last peak.


JLAB Hall A E94-107: preliminary comparison with theory for 12Bhypernucleus


Cou

nts

/ 2

00 k

eV

12C(e,e’K)12B12C(e,e’K)12B











Theory = 4.4 nb/(GeV sr2 )

Stat ~ 5 %Tot. ~ 20 %

g.s. CrossSection = 4.6 nb/(GeV sr2 )


Results from last year run 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


Blue line: Sagay Saclay-Lyon (SLA)



Blue line: Sagay Saclay-Lyon (SLA)


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


First Results from current experiment 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”


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

2005 E-94107: Preliminary spectra of missing energy

1H (e,e’K)1H (e,e’K)

16O(e,e’K)16N16O(e,e’K)16N

16O(e,e’K)16N

16O(e,e’K)16N

Low counting levels above Ethr.

16O(e,e’K)16N

16O(e,e’K)16N


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.

New experimental equipments demonstrated excellent performance.

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

selection.

On-going Analysis of data on 12Ctargetis showing new information on

12Band interesting comparison with theory for 12B and 9Li.

VERY Promising physics is coming out from the presently running

experiment on 16Nhypernuclear spectroscopy (also with p(e,e’K)X-Sect.

MeasurementS. Marrone – Indian-Summer School, Rez, Prague 3-7 October 2006

There is growing evidence that hyperons appears the first of the strange

hadrons in neutron stars at around twice normal density….The onset of the hyperon

formation is controlled by the attactive hyperon-nucleon interaction wich can be

extracted from hypernucleon scattering data and hypernuclear data

(J. Shaffner-Bielich et al: Hyperstars: Phase Transition to (meta)-Stable Hyperonic matter in

neutron Stars, arXiv: astroph/0005490

“ Additional experimental data from hypernuclei will be useful in establishing

the foundations of high density matter models. This is especially relevant for the

hyperon-nucleon interactions, for which relevant systems are more likely to be

produced in current accelerators than for hyperon-hyperon interactions”

in S. Balberg et al: Roles of hyperons in Neutron Stars, arXiv: astro-ph/9810361

HYPERNUCLEI and ASTROPHYSICS contd


Documents

Hypernuclear Spectroscopy in Hall-A at JLAB