Hypernuclear spectroscopy in Hall A12C, 16O, 9Be, H E-07-012

Experimental issues

Perspectives (Hall A & Hall C collaboration)

High-Resolution Hypernuclear Spectroscopy ElectronScattering at Jlab

F. Garibaldi – Bormio 22-01-2013

Hypernuclear investigation• Few-body aspects and YN, YY interaction

– Short range characteritics ofBB interaction– Short range nature of the LN interaction, no pion exchange:

meson picture or quark picture ?– Spin dependent interactions– Spin-orbit interaction, …….– LS mixing or the three-body interaction

• Mean field aspects of nuclear matter– A baryon deep inside a nucleus distinguishable as a baryon ? – Single particle potential – Medium effect ?– Tensor interaction in normal nuclei and hypernuclei– Probe quark de-confinement with strangeness probe

• Astrophysical aspect– Role of strangeness in compact stars– Hyperon-matter, SU(3) quark-matter, …– YN, YY interaction information

HYPERNUCLEAR PHYSICS Hypernuclei are bound states of nucleons with a strange baryon (L)

Extension of physics on N-N interaction to system with S#0

Internal nuclear shell are not Pauli-blocked for hyperons

Spectroscopy

L-N interaction, mirror hypernuclei,CSB, L binding energy…

Ideal laboratory to study

This “impurity” can be used as a probe to study both the structure and properties of baryons in the nuclear medium and the structure of nuclei as baryoni many-body systems

H.-J. Schulze, T. Rijken PHYSICAL REVIEW C 84, 035801 (2011)

High resolution,

high yield, and systematic

study is essential

using electromagnetic probe

and

BNL 3 MeV

Improving energy

resolution

KEK336 2 MeV

~ 1.5 MeV

new aspects of hyernuclear structureproduction of mirror hypernuclei

energy resolution ~ 500 KeV

635 KeV635 KeV

LN interaction(r)

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

V

SL

SN

D

T

✔ most of information is carried out by the spin dependent part ✔ doublet splitting determined by D, sL, T

YN, YY Interactions and Hypernuclear Structure

Free YN, YY interactionConstructed from limited hyperon scattering data

(Meson exchange model: Nijmegen, Julich)

YN, YY effective interaction in finite nuclei(YN G potential)

Hypernuclear properties, spectroscopic informationfrom structure calculation (shell model, cluster model…)

Energy levels, Energy splitting, cross sectionsPolarizations, weak decay widths

high quality (high resolution & high statistics) spectroscopy plays a significant role

G-matrix calculation

AK

Z

iH iJ

*

1

ELECTROproduction of hypernucleie + A -> e’ + K+ + H

in DWIA (incoming/outgoing particle momenta are ≥ 1 GeV)

- Jm(i) elementary hadron current in lab frame (frozen-nucleon approx)- virtual-photon wave function (one-photon approx, no Coulomb distortion)- K– distorted kaon w. f. (eikonal approx. with 1st order optical potential)-YAYH - target nucleus (hypernucleus) nonrelativistic wave functions (shell model - weak coupling model)

good energy resolution

reasonable counting rates

forward angle

septum magnets

do not degrade HRS

minimize beam energy instability “background free” spectrum unambiguous K identification

RICH detectorHigh Pk/high Ein (Kaon survival)

1. DEbeam/E : 2.5 x 10-5 2. DP/P : ~ 10-4

3. Straggling, energy loss…

~ 600 keV

JLAB Hall A Experiment E94-107

16O(e,e’K+)16LN

12C(e,e’K+)12L

Be(e,e’K+)9LLi

H(e,e’K+)LS0

Ebeam = 4.016, 3.777, 3.656 GeVPe= 1.80, 1.57, 1.44 GeV/c Pk= 1.96 GeV/c

qe = qK = 6°W 2.2 GeV Q2 ~ 0.07 (GeV/c)2

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

Counting Rates ~ 0.1 – 10 counts/peak/hour

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 Collaborationand Theorists: Petr Bydzovsky, John Millener, Miloslav Sotona

E94107 COLLABORATION

E-98-108. Electroproduction of Kaons up to Q2=3(GeV/c)2 (P. Markowitz, M. Iodice, S. Frullani, G. Chang spokespersons)

E-07-012. The angular dependence of 16O(e,e’K+)16N and H(e,e’K+)L (F. Garibaldi, M.Iodice, J. LeRose, P. Markowitz spokespersons) (run : April-May 2012)

Kaon collaboration

hadron arm

septum magnets

RICH Detector

electron arm

aerogel first generation

aerogel second generation

To be added to do the experiment

Hall A deector setup

Kaon Identification through Aerogels

The PID Challenge Very forward angle ---> high background of p and p- TOF and 2 aerogel in not sufficient for unambiguous K identification !

AERO1 n=1.015

AERO2 n=1.055

pkp

ph = 1.7 : 2.5 GeV/c

Protons = A1•A2

Pions = A1•A2Kaons = A1•A2

pkAll events

p

k

RICH – PID – Effect of ‘Kaon selection

p P

K

Coincidence Time selecting kaons on Aerogels and on RICH

AERO K AERO K && RICH K

Pion rejection factor ~

1000

12C(e,e’K)12BL M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007)

Be windows H2O “foil”

H2O “foil”

The WATERFALL target: reactions on 16O and 1H nuclei

1H (e,e’K)L

16O(e,e’K)16NL

1H (e,e’K)LS

L

SEnergy Calibration Run

Results on the WATERFALL target - 16O and 1H

Water thickness from elastic cross section on H Precise determination of the particle momenta and beam energy using the Lambda and Sigma peak reconstruction (energy scale

calibration)

Fit 4 regions with 4 Voigt functions2

/ndf = 1.19

0.0/13.760.16

Results on 16O target – Hypernuclear Spectrum of 16NL

Theoretical model based on :SLA p(e,e’K+)L (elementary

process)LN interaction fixed parameters

from KEK and BNL 16LO spectra

• Four peaks reproduced by theory

• The fourth peak (L in p state) position disagrees with theory. This might be an

indication of a large spin-orbit term SL

Fit 4 regions with 4 Voigt functions2

/ndf = 1.19

0.0/13.760.16

Binding Energy BL=13.76±0.16 MeV

Measured for the first time with this level of accuracy (ambiguous interpretation

from emulsion data; interaction involving L

production on n more difficult to normalize

Within errors, the binding energy and the excited levels of the mirror hypernuclei 16OL and 16NL (this experiment) are in agreement, giving no strong evidence of charge-dependent effects

Results on 16O target – Hypernuclear Spectrum of 16NL

Radiative corrected experimental excitation energy vs theoretical data (thin curve). Thick curve: three gaussian fits of the radiative corrected data

Experimental excitation energy vs Monte Carlo Data (red curve) and vs Monte Carlo data with radiative Effects “turned off” (blue curve)

Radiative corrections do not depend on the hypothesis on the peak structure producing the experimental data

9Be(e,e’K)9LiL

10/13/09

p(e,e'K+)L on WaterfallProduction run

Expected data from E07-012, study the angular dependence of

p(e,e’K)L and 16O(e,e’K)16NL at low Q2

Results on H target – The p(e,e’K)L Cross Section

p(e,e'K+)L on LH2 Cryo Target

Calibration run

None of the models is able to describe the data over the entire range

New data is electroproduction – could

longitudinal amplitudes dominate?

W2.2 GeV

How?

The interpretation of the hypernuclear spectra is difficult because of the lack of relevant information about the elementary process.

Hall A experimental setup (septum magnets, waterfall target, excellent energy resolution AND Particle Identification ) give unique opportunity to measure, simultaneously, hypernuclear process AND elementary process

In this kinematical region models for the K+- L electromagnetic production on protons differ drastically

The ratio of the hypernuclear and elementary cross section measured at the same kinematics is almost model independent at very forward kaon scattering angles

Why?

The ratio of the hypernuclear and elementary cross section doesn’t depend strongly on the electroproducion model and contains direct information on hypercnulear structure and production mechanism

The results differ not only in the magnitude of the X-section (a factor 10) but also in the angular dependence (given by a different spin structure of the elementary amplitudes for smaller energy (1.3 GeV) where the differences are smaller than at 2 GeV

the information from the hypernucleus production, when the cross sections for productionof various states are measured, is reacher than the ordinary elementary cross section

Measuring the angular dependence of the hypernuclear cross section, we may discriminate among models for the elementary process.

Future mass spectroscopy

Hypernuclear spectroscopy prospectives at Jlab

Collaboration meeting - F. Garibaldi – Jlab 13 December 2011

Decay Pion Spectroscopy to Study L-Hypernuclei

- Put HKS behind a Hall A style septum magnet in

Hall A - Enhance setup in Hall A over HRS2 + Septum

-No compromise of low backgrounds - Independently characterize the optics of each arm using elastic scattering - The HKS+Septum arm would replace present Hall A Kaon arm (Septum+HRS)

- Keep the ability to use waterfall target or cryotargets

SL, p-1 states are weakly populated - small overlap of the corresponding single particle wave functions of proton and lasmbda. For L in higher s.p. states overlap as well as cross sections increases being of the order of ~ 1 nb.

208

208

208

208

208

We have to evaluate pion and proton background and fine tune it with data from (e,e’p)Pb

PR12-10-001 - Study of Light - Hypernuclei by Spectroscopy of Two Body Weak Decay Pions

Fragmentation of Hypernuclei And Mesonic Decay inside Nucleus

Free: L p + p -

2-B: ALZ A(Z + 1) + p - (and fragmentation of hypernuclei)

Thus high yield and unique decay feature allow high precision measurement of decay pion spectroscopy from which variety of physics may be extracted

- High yield of hypernuclei (bound or unbound in continuum) makes high yield of hyper fragments, i.e. light hypernuclei which stop primarily in thin target foil- Weak 2 body mesonic decay at rest uniquely connects the decay pion momentum to the well known structure of the decay nucleus, BL and spin-parity of the ground state of

hyperfragment

- High momentum transfer in the primary production sends most of the background particles forward, thus pion momentum spectrum is expected to be clean with minor 3-

boby decay pions.

(p - 0.1)

ConclusionsE94-107: “systematic” study of p shell light

hypernuclei

The experiment required important modifications on the Hall A apparatus.New experimental equipment showed excellent performance.

Data on 12C show new information. For the first time significant strength and resolution on the core excited part of the spectrum

Prediction of the DWIA shell model calculations agree well with the spectra of 12BL and 16NL for L in s-state. In the pL

region more elaborate calculations are needed to fully understand the data.

Interesting results from 9Be, interpretation underway Elementary reaction needs further studies More to be done in 12 GeV era (few body, Ca-40,Ca-

48,Pb…)

Back up slides

PAVI 09

Lead Target

Liquid Helium Coolant

Pb

C

208

12

Diamond Backing:

• High Thermal Conductivity• Negligible Systematics

Beam, rastered 4 x 4 mm

beam

Diaond LEAD

Lead / Diaond Taret

• Three bas• Lead 0.5 sandwihed b

diaond 0.15 • Liquid He oolin 30 Watts

Perforane of Lead / Diaond Tarets durin PREX

Last 4 days at 70 uA

Targets with thin diamond backing (4.5 % background) degraded fastest.

Thick diamond (8%) ran well and did not melt at 70 uA.

eltedelted

NOT elted

PREX-II plan: Run with 10 targets.

Coents on Pb/D Taret

If perfet theral ontat to diaond Iax > 100 uA. If no ontat Iax 10 uA

Soe have suested a spinnin taret.Miht work for soe expt’s but

• needs R&D• a ause noise relevant to parit expt’s

Ideas bein onsidered thouh no ation et: • sputter lead onto diaond ahieve better ontat• tests of new desins at Idaho State Universit

eletron bea failit