JLAB Hall A Experiment E94-107

1616O(e,e’KO(e,e’K++))1616NN

1212C(e,e’KC(e,e’K++))1212

Be(e,e’KBe(e,e’K++))99LiLi

H(e,e’KH(e,e’K++))00

Ebeam = 4.016, 3.777, 3.656 GeV

Pe= 1.80, 1.57, 1.44 GeV/c Pk= 1.96 GeV/c

e = K = 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 Collaboration

E94107 COLLABORATION

• 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

G. M. Urciuoli INPC2007

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

G. M. Urciuoli INPC2007

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

G. M. Urciuoli INPC2007

METHOD TO IMPROVE THE OPTIC DATA BASE:

An optical data base means a matrix T that transforms the focal plane coordinates inscattering coordinates:

y

x

X

Y

DP

Y

XTY

To change a data base means to find a new matrix T’ that gives a new set of values:

: XTY

''

YTX

1Because: this is perfectly equivalent to find a matrix 1' TTF

YFY

'you work only with scattering coordinates.

.

From F you simply find T’ by:

TFT '

METHOD TO IMPROVE THE OPTIC DATA BASE (II)

You have:

Y)Φ,Θ,P(DP,DPδ(DP)DPYδFDPDP'

FF 1Expressig:

just consider as an example the change in the momentum DP because of the change in the data base:

with a polynomial expression

Because of the change DPDP’ also the missing energy will change:

),,,()()()(

)())(()'( YDPADPEmissDPDP

EmissDPEmissDPDPEmissDPEmiss

In this way to optimize a data base you have just to find empirically a polynomial

in the scattering coordinates that added to the missing energy improves its resolution:

)(

')(

DP

EmissEmissEmiss

DP

and finally to calculate

Emiss ),,,( YDPP

),,,( YDPA

)(' YYYFYY

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 112

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

G. M. Urciuoli INPC2007

Results on 12C target

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

Results published: M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007).Results published: M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007).

Results on 12C target – Hypernuclear Spectrum of 12B

G.S. width is 1150 keV; an unresolved doublet?What would separation be between two 670 keV peaks? ~650 keV (theory predicts only 140)

Narrowest peak is doublet at 10.93 MeV experiment resolution < 700 keV

670 keVFWHM

Preliminary Results on the WATERFALL target

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

and 1H(e,e’K)(elementary reaction)

Waterfall target allows energy-scale calibration of 16O(e,e’K)16N

by 1H(e,e’K)(peak at binding energy = zero)

Be windows H2O “foil”

H2O “foil”

the WATERFALLWATERFALL target: provides 16O and H targets

1H (e,e’K)1H (e,e’K)

16O(e,e’K)16N16O(e,e’K)16N

1H (e,e’K)1H (e,e’K)

Energy Calibration Run

Preliminary Results on the WATERFALL target - 16O and H spectra

Excitation Energy (MeV)N

b/sr

2 G

eV

MeV

Water thickness from elastic cross section on H Fine determination of the particle momenta and beam energy

using the Lambda peak reconstruction (resolution vs position)

Results on 16O target – Hypernuclear Spectrum of 16N

- Peak Search :Identified 4 regions with excess counts above background

Binding Energy B=13.68 ± 0.16 (stat) ± 0.05 (sys) MeVMeasured for the first time with this level of accuracy (ambiguous interpretation from emulsion data; interaction involving production on n more difficult to normalize)

Fit to the data (red line): Fit 4 regions with 4 Voigt functions 2

/ndf = 1.19 Theoretical model (blu line)

superimposed curve based on :i) SLA p(e,e’K+) (elementary

process)ii) N interaction fixed

parameters from KEK and BNL 16O spectra

Results on 16O target – Hypernuclear Spectrum of 16N

11

11.5

12

12.5

13

13.5

14

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Serie1

E94-107

(+,K+)

(K-,-) (Kstop,-)

[2] O. Hashimoto, H. Tamura,Part Nucl Phys 57, 564 (2006)

[3] private communication from D. H. Davis, D. N. Dovee, fit of data from Phys Lett B 79, 157 (1978) [4] private communication from H. Tamura, erratum on Prog Theor Phys Suppl 117, 1 (1994)

[2] [3] [4]

Comparison with the mirror nucleus 16O

Difference expected with respect to mirror nucleus:

400 – 500 keV (M. Sotona)

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

p(e,e'K+) on LH2 Cryo TargetCalibration run

Expected data from theExperiment E07-012 to study the angular dependence of p(e,e’K) and 16O(e,e’K)16N at Low Q2

(approved January, 2007)

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

Be(e,e’KBe(e,e’K++))99LiLi

1.4

1.2

1.0

0.6

0.8

0.4

Li9

Chi2/NDF: 266.342 / 232 = 1.14803

0:       7.23 +/- 3.68 ,   6.44+/- 0.21 , 0.71 +/- 0.15

Peak    Strength     Position   FWHM  

1:     23.20+/- /4.75 ,   7.10 +/- 0.08,   0.71 +/- 0.15

2:     12.57 +/- 5.66,   8.06 +/- 0.08,   0.71 +/- 0.15

3:     11.01 +/- 5.68 ,   8.54 +/- 0.08,   0.71 +/- 0.15

4:    11.87 +/- 3.51 ,   9.18+/- 0.11, 0.71 +/- 0.15

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

Conclusion• E94-107 experiment successfully performed:

• Three hypernuclei studied:

+ the reaction:

1616N N ((submitted ) and 99

LiLi1212(published),

H(e,e’KH(e,e’K++))00

Experiment E07-012 will study the angular dependence of p(e,e’K)L and 16O(e,e’K)16NL at Low Q2(approved January, 2007)