Hypernuclei: A quick introduction Electroproduction of hypernuclei E94-107 experiment UPDATE Experimental equipment and setup Analysis results of 2004.

Hypernuclei: A quick introduction

Electroproduction of hypernuclei

E94-107 experiment UPDATE

Experimental equipment and setup

Analysis results of 2004 run on 12C and 9Be

Preliminary results of 2005 run on 16O

Conclusions

Mauro Iodice – e94107 update – Hall A Collaboration Meeting, JLAB, Dec 6 2005

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

Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005

HYPERNUCLEI …what they are

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.


HYPERNUCLEI and ASTROPHYSICS

Strange baryons may appear in neutral -stable matter through process like:

€

n + e− → Σ− + ν e

The presence of strange baryons in neutron stars strongly affect their

properties. Example: mass-central

density relation for a non-rotating (left) and a rotating (right) star

The effect strongly depends upon the poorly known interactions of strange baryons

More data needed to constrain theoretical models.


Hypernuclei - historical background - experimental techniques

To commemorate their discovery the above postcard was issued by the Polish Post in May 1993

1953 : discovery of first hypernucleus by Danysz and Pniewskiwhile studying cosmic radiation with emulsion techniques

1962 : The first double Hypernucleus wasdiscovered in a nuclear emulsionirradiated by a beam of K- mesons

at CERN

The first observation of a hypernucleus


1953 1970 : hypernuclear identification with visualizing techniquesemulsions, bubble chambers

1970 Now : Spectrometers at accelerators:

CERN (up to 1980)

BNL : (K-, -) and (K+, +) production methods

KEK : (K-, -) and (K+, +) production methods

> 2000 : Stopped kaons at DANE (FINUDA) : (K-stop, -)

> 2000 : The new electromagnetic way :

HYPERNUCLEAR production with

ELECTRON BEAM at JLAB

Elementary reactionon neutron :

€

K− + n → π − + Λ

€

+ + n → K + + Λ

€

12C → 12CΛ

e.g.

Elementary reactionon proton :

€

e + p → ′ e + K + + Λ

€

12C → 12BΛ

e.g.

Hypernuclei - historical background - experimental techniques

Production of MIRROR hypernuclei

: I=0, q=0 n = pSpectroscopy of mirror hypernuclei reveal n ≠ p 0 mixing and N-N coupling

Present status of Hypernuclear Spectroscopy

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

(e,e’K+)

€

16N

This exp. E94-107


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

“weak coupling model”

(parent nucleus) ( hyperon) (doublet state)

€

JA−1 + Λ(s − shell) → JHyp = JA−1 ± 12

€

VΛN = V0(r) + Vσ (r)r s Λ ⋅

r s N + VΛ (r)

r l ΛN ⋅

r s Λ + VN (r)

r l ΛN ⋅

r 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


Electroproduction of hypernuclei

by the reaction:

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

€

e +AZ → ′ e + K + + A

Z −1( )Λ

€

e +AZ → ′ e + K + + A

Z −1( )Λ

Hypernucleus

K+

ee’

p

AZ(e,e’K)A(Z-1)HRSe at 6˚

HRSk at 6˚ e beam~4 GeV

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; clear identification of core excited states)

16O 16N(details of the hyper. spectrum also depends on single particle spin-orbit splitting )

Spin flip states

p Production of mirror nuclei / n rich hypernuclei

High energy resolution


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 spread (SLI, OTR) and absolute energy, spectrometers NMR, BPMs, …

Excellent energy resolution Best performance for beam and HRS+Septa

with accurate optics calibrations

Experimental requirements :

1. E/E : 2.5 x 10-5

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

3. Straggling, energy loss…

≤ 600 keV


Last year e94107 experiment took data in two separate periods. Data have been collected on solid targets. The second part of the experiment took data in June 2005 in Hall A using the waterfall target

January 2004 12C target

April 2004 12C target and May 2004 9Be

June 2005 Waterfall target for hypernuclear state production on 16O and (as a byproduct) on the elementary process on Hydrogen

Data taking, 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


SEPTUM magnets in Hall A: new optics DB for the D+QQDQ system

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

FWHM = 1.1x10-4

FWHM = 2.2x10-4

NEW DB “2005”OLD DB “2004”


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

Chϑ“MIP”

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

..

..

ep

ep

Nc

ϑϑ

=

Cherenkov angle resolution

Separation Power

cϑϑϑ n12 =−


Rich Performance ‘key parameters’:

mrad c

5≈ϑAngular resolution:

Npe /p ratio:

66.01

122

22

=−−

=nn

NN P

clus

Pclus

Npe for and p

Cherenkov angle for

Cherenkov average angle (rad)

Nclusters


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:

AERO K AERO K && RICH K

GREATLY improved AEROGEL performance!


Shell model excitation levels for 12B

dependence on the N potential - different set of potential params.

x 0p

x 0s

11C energy spectrum

J=1-, 2- doublet

x 0sJ=1-

J=2-

J=2+, 3+

J=1/2-

E=~2 MeV

J=3/2-

E=0.0 MeV

J=3/2-

E=~5 MeV

J=5/2-

E=~4.5 MeV

x 0s

12B energy spectrum

J=1-

J=2-

J=2+, 3+

J=1-

J=2-

J=2+, 3+

YNG potential “Canonical” “Standard”


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

ΛΛ

Λ

ΛΛΛ

Λσ

Λ

σ⋅σ−⋅σ⋅σ=

+

−σ⋅+

−σ⋅+

−Δσ⋅σ+

=

NN

T

NNNSO

NSO

N

rrS

TSrV

SrV

SrV

rV

rVV

rr

l

l

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, …)


9Be(e,e’K)9Li

a c db

( )( )

)())((3

(Tensor))(

orbitspin)(

orbitspin)(

spin)(spin)(

(central)V)(

12

12

0N

ΛΛ

Λ

ΛΛΛ

Λσ

Λ

σ⋅σ−⋅σ⋅σ=

+

−σ⋅+

−σ⋅+

−Δσ⋅σ+

=

NN

T

NNNSO

NSO

N

rrS

TSrV

SlrV

SlrV

rV

rVV

rr

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


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

Results from last year run on 12C target

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


Results on 12C target – Hypernuclear Spectrum of 12B

12C(e,e’K)12B12C(e,e’K)12B

< 1 MeV FWHM

Missing energy (MeV)

g.s.


As obtained with the old optics DB. The new one does not improve the resolution … still under analysis/investigation

Aerogel Kaon selection

RICH Kaon selection

12C(e,e’K)12B12C(e,e’K)12B

€

Signal

Bckgnd= 2.5

€

Signal

Bckgnd> 7

Analysis on 12B spectrum : Aerogel vs. RICH K-selection


Analysis on 12B spectrum : FIT to the data

Gaussian fit systematically underestimateThe peaks try with different shapes :


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

Two 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.






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.

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.


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.










Theory = 5.4 nb/(GeV sr2 ) …!!!

Stat ~ 4.3 %Syst ~ 20 %

g.s. CrossSection = 5.00 nb/(GeV sr2 )


Analysis on 12B spectrum : COMPARISON with models

New comparison: inclusion of ”all” predicted levels bring to a stronger disagreement for levels with in p-shell


H. Hotchi et al., Phys. Rev. C 64 (2001) 044302 H. Hotchi et al., Phys. Rev. C 64 (2001) 044302

E94-107 Hall A Experiment Vs. KEK-E369

12C(e,e’K)12B12C(e,e’K)12B 12C(,K+)12C

12C(,K+)12C

Statistical significance of core excited states:

€

Signal

Bckgnd> 7


E94-107 Hall A Experiment Vs. FINUDA (at Dane)

12C(e,e’K)12B12C(e,e’K)12B 12C(K-, )12C

12C(K-, )12C


€

Signal

Bckgnd> 7


E94-107 Hall A Experiment Vs. HallC E89-009

12C(e,e’K)12B12C(e,e’K)12B 12C(e,e’K)12B

12C(e,e’K)12B

Miyoshi et al., PRL 90 (2003) 232502.

New analysis


€

Signal

Bckgnd> 7


E94-107 Hall A Experiment: status of 12B data

12C(e,e’K)12B12C(e,e’K)12B


€

Signal

Bckgnd> 7

Energy resolution is ~ 900 keV with old optics database

More than one year spent to improve the resolution

Although the new database does a very good job for single arm elastics data: 1.1 10-4 the expected resolution of less than 600 keV is not yet achieved

some more check and tuning has to be done, …but :

despite the fact that optimal resolution has not yet been obtained, the data are of extremely good quality

… to be published soon


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



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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”


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


Analysis on 16N spectrum : FIT to the data


15N energy spectrum16N energy spectrum

Analysis on 16N spectrum : COMPARISON with models

High energy excited MULTIPLETS seems NOT WELL reproduced by the model.

-interaction here is in p-state, poorly known….

High energy excited MULTIPLETS seems NOT WELL reproduced by the model.

-interaction here is in p-state, poorly known….


Analysis on 16N spectrum : COMPARISON with models

…SHIFTING “by hand” the positions of these MULTIPLETS in the model, while mantaining the predicted strength, a VERY GOOD agreement with the data can be reached.

…SHIFTING “by hand” the positions of these MULTIPLETS in the model, while mantaining the predicted strength, a VERY GOOD agreement with the data can be reached.

Work is in progress for a deeper physics interpretation.

Work is in progress for a deeper physics interpretation.


16O(e,e’K)16N16O(e,e’K)16N

E94-107 Hall A Experiment Vs. KEK-E336

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


16O(e,e’K)16N16O(e,e’K)16N

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

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


Importance of the elementary reaction 1H(e,e’K)at low Q2

In K+ photoproduction on proton there is a clear inconsistency of the experimental data (CLAS vs SAPHIR) at K

cm < 40 deg. Electroproduction at very low Q2 can clarify this inconsistency, which is also important for calculation for hypernuclear cross sections.

1H (e,e’K)1H (e,e’K)K+ photoproduction


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 performed 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 new data on the waterfall target

for 16Nhypernuclear spectroscopy - also for p(e,e’K)X-Sect. measurement


Hypernuclei: A quick introduction Electroproduction of hypernuclei E94-107 experiment UPDATE Experimental equipment and setup Analysis results of 2004.

Documents

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nn coupling slide

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collaboration meeting

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