Prospects on Hypernuclear PhysicsProspects on Hypernuclear Physics

• Hypernuclear physics: state of the artHypernuclear physics: state of the art

• DADAΦΦNE: an efficient hypernuclear factoryNE: an efficient hypernuclear factory

• FINUDA physics programFINUDA physics program

• Future prospectsFuture prospects

• ConclusionsConclusions

• Hypernuclear physics: state of the artHypernuclear physics: state of the art

• DADAΦΦNE: an efficient hypernuclear factoryNE: an efficient hypernuclear factory

• FINUDA physics programFINUDA physics program

• Future prospectsFuture prospects

• ConclusionsConclusions

Paola Gianotti

LNF

Hypernuclear Physics: state of the artHypernuclear Physics: state of the art

Hypernuclear physics is a good tool to match nuclear and particle

physics. The study of this field may help in understanding some

crucial questions:

four baryon weak

interaction vertex;

YN and YY strong interactions;

change of hyperon and meson properties in the nuclear medium;

existence of di-baryon particles;

the role played by the quark degrees of freedom,

flavor symmetry and chiral models in nuclear and hypernuclear field.

N 　 　 N

　 　 N

　 　 N

　 　 N

K

　 　

d

6Li

+ d

Li7Λ

120 )(sl)(sl)(ss)()()( SrVrVrVrVrVrV TNN NNΛΛNΛΛN

120 )(sl)(sl)(ss)()()( SrVrVrVrVrVrV TNN NNΛΛNΛΛN

d

s

u

W u

d

dn

u

u

d

u

u

d

pp

The 2nd roundFirst Counter Experiments CERN & BNL1973 Stopped (K,π) at CERN1974 in-flight (K,π) at CERN PS and BNL AGS

very small spin-orbit splitting

The 2nd roundFirst Counter Experiments CERN & BNL1973 Stopped (K,π) at CERN1974 in-flight (K,π) at CERN PS and BNL AGS

very small spin-orbit splitting

The 1st round 1953 Discovery of Λ hypernucleiEmulsion detectors --- CERN PS, BNL AGS K beam

Λ potential depth about 1/2

The 1st round 1953 Discovery of Λ hypernucleiEmulsion detectors --- CERN PS, BNL AGS K beam

Λ potential depth about 1/2

The 3rd roundNew reactions with New Detectors1985 (π+,K+) started at AGS1990 S=-2 searches at AGS and KEK (Emulsion-counter hybrid technique)1993 S=-1 Λ Spectroscopy, Weak decay, SKS spectrometer1998 　ray spectroscopy (Hyperball)

ΛN potential definition Γn/ Γp puzzle in the non-mesonic decays

The 3rd roundNew reactions with New Detectors1985 (π+,K+) started at AGS1990 S=-2 searches at AGS and KEK (Emulsion-counter hybrid technique)1993 S=-1 Λ Spectroscopy, Weak decay, SKS spectrometer1998 　ray spectroscopy (Hyperball)

ΛN potential definition Γn/ Γp puzzle in the non-mesonic decays

50 years of Hypernuclear Physics50 years of Hypernuclear Physics

Production of Production of ΛΛ-Hypernuclei-Hypernuclei

nK nK

Kn Kn

Kepe )()( Kepe )()(

Different production mechanisms can be used to form an hypernuclei:

strangeness exchange reaction (in flight, stopped)

σ ≈ 100 mb ; Ibeam = 104 s-1

associated production

σ ≈ 1 mb ; Ibeam = 107 s-1

real and virtual photo- production σ ≈ μb ; Ibeam = 1010 s-1

Hyp

eron

rec

oil m

omen

tum

[MeV

/c] θL= 0o

Kn

Kepe )()(

NK

Projectile momentum pLab [GeV/c]

Production of Production of ΛΛ-Hypernuclei-Hypernuclei(K+,π+), and (K-

stop,π-) are similar, both give

to the hyperon a large momentum transferred, but not identical. Many excited hypernuclear states

Electroproduction mainly populates streched

and unnatural parity nuclear states.

DWIA calculationsDWIA calculations

12C(K-,π-)

pK=800 MeV/c

12C(π+,K+) pπ=1040 MeV/c

θ=0o

12C(π+,K+) pπ=1040 MeV/c

θ=0o

12C(K-stop,π

-)

a

b

c

K.Itonaga et al., Prog. Theor. Phys 84 (1990) 291.

T.S.H. Lee et al., Phys. Rev. C 58 (1998) 1551.

12C(,K+)12ΛB

E=1.1GeV

θ=10o

Saclay-Lyon amplitudeSaclay-Lyon amplitude

12C(K-,π-)

Production of Production of ΛΛ-Hypernuclei-Hypernucleiexp. resultsexp. results

12C(,K+)12ΛB

HNSS(E89-009) high resolution (900MeV FWHM) spectrometer

FINUDA experiment high resolution (1.4 MeV FWHM) spectometer

pΛ

sΛ

pΛsΛ

• GOALGOAL: understanding Baryon-Baryon interactions

• NN interaction: experimentally well known from elastic scattering data phenomenologically well reproduced by meson-exchange and quark-cluster models• YN, YY interaction: poor scattering data low yield, short lifetime (c < 10 cm)

Hypernuclear SpectroscopyHypernuclear Spectroscopy

information from hypernuclei are important mostly Λ-hypernuclei ΛN interaction In Λ-hypernuclei: No Pauli effect, weak coupling simple structure extraction of ΛN interaction is rather straightforward

information from hypernuclei are important mostly Λ-hypernuclei ΛN interaction In Λ-hypernuclei: No Pauli effect, weak coupling simple structure extraction of ΛN interaction is rather straightforward

Hypernuclear SpectroscopyHypernuclear Spectroscopy

Phenomenological NN, YN potential, mainly based on OBE mechanism, improves (Nijmegen ESC02, 03) thanks to hypernuclear physics

Textbook example of

Single-particle orbits in nucleus

Hotchi et al., PRC 64 (2001) 044302

The peak positions is well describedby a Wood-Saxon potential

The peak positions is well describedby a Wood-Saxon potential

spectroscopy 　 7

Li, 9Be, 10

B, 11B, 15

N, 16O KEK E419, E509, E518; BNL E930

　 13C BNL E929 NaI array

Recent improvements Recent improvements (1998~2003)(1998~2003)

Hyperball

120 )(sl)(sl)(ss)()()( SrVrVrVrVrVrV TNN NNΛΛNΛΛN

　　　　　　　　　　　　　　　　　　　　　　　　　　　S　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　S　　　　　　　　　　　　　　　　　　　　p shell: 4 radial integrals for pN,sΛ w.f.

KEK E419 (π+,K+) 7ΛLi

Towards hyper-fine splitting understanding

N- LS interaction SN~ -0.4 MeV

N- LS interaction SN~ -0.4 MeV

spin-spin interaction = 0.50 MeV

spin-spin interaction = 0.50 MeV

BNL E930 (K-　π-) 9ΛBe S= 　　0.01 MeVS= 　　0.01 MeV

BNL E929 (K-,π-) 13ΛC

HYPERBALL

S = 152 ± 54(stat) ± 36(syst) keVS = 152 ± 54(stat) ± 36(syst) keV

The experimental measurements on SΛ are in agreement but smaller than the values given by the meson exchange models

The experimental measurements on SΛ are in agreement but smaller than the values given by the meson exchange models

NaI

BNL E930 (K　π) 13ΛC

OBEP predictions agree with the experimental value ND NF NSC89 NSC97f T (keV) 18 33 36 54

OBEP predictions agree with the experimental value ND NF NSC89 NSC97f T (keV) 18 33 36 54

T ~ 30 keV (prelim.) First info. on TT ~ 30 keV (prelim.) First info. on T

ΛΛΛΛ interactioninteraction• Unique channel in SU(3) BB interaction classification• Repulsive core may vanish in this channel possibile existense of H-dibaryon (uuddss, J=I=0)• Original prediction by Jaffe (PRL38 (1977) 195) - H is predicted 80 MeV below ΛΛ mass • No experimental evidence so far - at least, deeply bound H is rejected• ΛΛ - Ξ N (- ΣΣ) coupling important (ΔE = 28 MeV)• ΛΛ interaction study performed by - ΛΛ hypernuclei - ΛΛ final state interaction in (K-,K+) reaction (J. K. Ahn et al., PLB444 (1998) 267 )• Present data suggests ΛΛ interaction is weakly attractive

Hybrid emulsion experiment Hybrid emulsion experiment (KEK-PS E373)(KEK-PS E373)

• Hybrid emulsion -- (K-,K+) reaction to produce Ξ -

then stop it in emulsion• The best event found (H. Takahashi et al., PRL87(2001)212502)

6• Track #1 is the• Binding energy of is obtained to be B = 7.3±0.3 MeV (from )• In order to extract interaction, we take B　= B　　　　　　　　　 　　　　　　　　　= 1.0±0.3 MeV weakly attractive

• Track #1 is the• Binding energy of is obtained to be B = 7.3±0.3 MeV (from )• In order to extract interaction, we take B　= B　　　　　　　　　 　　　　　　　　　= 1.0±0.3 MeV weakly attractive

He6

He

He5

K- K+

-

Chain of π- decays (BNL E906)

D6 line CDS detector: (K-,K+) Ξ -　, Ξ - + 9Be -> ΛΛ Z 　 + X

First production of ΛΛ　hypernuclei by a counter experiment

PRL 87(2001) 132504

3H

4H

4 ΛΛ H → 4

ΛHe* + π- (104)

→ 3 Λ H + p

→ 3He + π- (114.3)

3H

4H

Neutron rich Neutron rich ΛΛ-Hypernuclei-Hypernuclei

Better candidates to study matter with extreme N/Z ratio are neutron rich Λ-hypernuclei 7

ΛH, 6ΛH, 12

ΛBe,...

Here more extended mass distribution are expected thanks to the “gluing role” of the Λ

Interesting also for astrophysics studies on high density nuclear matter in neutron stars

A new branch of nuclear physics is studyng light nuclei with extended spatial distribution giving rise to a neutron halo.

number　of　neutrons

number　of　protons

solarburning

Proton-rich　nuclei

Neutron-rich　nuclei

Superheavy　elements

Neutron rich Neutron rich ΛΛ-Hypernuclei-HypernucleiTretyakova et al., Nucl. Phys, A691 (2001) 351c, Akaishi et al., Frascati Phys. S. XVI, (1999) 59

Two different production mechanisms have been invoked:1. Double charge exchange

K- p → Λ π0 ; π0 p → n π+

π-p → π0 n ; π0 p → K+ Λ• Strangeness exchange with

Λ-Σ couplingK- p → Σ- π+ ; (Σ- n Λ p)

π-p → Σ- K+ ; (Σ- n Λ p)

KEK E521

FINUDA

10B

Weak decay of hypernucleiWeak decay of hypernuclei• In free space...

Λ p + π- (63.9%, Q = 38 MeV) n + π0 (35.8%, Q = 41 MeV)• ΔI=1/2 rule holds - initial state: I=0, final state: I=1/2 or 3/2 if If = 1/2, branch is 2:1 3/2, 1:2 - this is a general rule in strangeness decay, but no one knows why• This decay (called mesonic decay) is suppressed in hypernuclei due to Pauli blocking for the final state nucleon.• Therefore, non-mesonic decay occurs in hypernuclei p + Λ p + n, n + Λ n + n, .... - Is the ΔI=1/2 still valid? We need to measure Γn and Γp

observables:observables:

　　

tot 0 np nn 3N　　

tot 0 np nn 3N

non- mesonicdecay

mesonicdecay

Do we need quarks to describe non-mesonic decay or the OBE description is good?

Do we need quarks to describe non-mesonic decay or the OBE description is good?

Weak decay of hypernucleiWeak decay of hypernuclei

OPE0.05 0.2

OME (with heavy meson )Quark models …

10 0.5 1.5Γn / Γ p

Exp. Value0.5 2

asymmetry of the weak decay of polarized Hypernucleiasymmetry of the weak decay of polarized Hypernuclei

Experimental measurements Experimental measurements (past)(past)

Λ lifetime is almost constant for A > 10 non-mesonic decay dominate short range nature of non-mesonic decay

Past experiments only measured Γtot

5He (E462) : Γn/ Γp 0.45±0.11±0.03

systematic error : 　 neutron efficiency(6%) + acceptance (3%)

Experimental measurements Experimental measurements (present)(present)

Modern experiments can measure

Γp and Γn at the same time:

KEK SKS FINUDA

En+Ep

En+En

First results are coming from KEK

To be compared with the old data: 0.93±0.55 (Szymanski et al. PRC 43 (1991)849)

Is the puzzle of Γn/ Γp solved? Stay tuned....

%)13(

%),34(

%),49()1020(00

LSKK

KKee

%)13(

%),34(

%),49()1020(00

LSKK

KKee

FINUDAFINUDA

FIFIsicasica NU NUclearecleare aa DADAΦΦNENE

The Φ　provide a unique “K- beam” :

1. monochromatic low momentum (127 MeV/c)

2. trigger tagging K-stop event through the associate K+

3. no hadronic background

that can be stopped in thin targets to produce hypernuclei

K-stop ++ AAZ Z AA

ΛΛZZ ++ ππ --K-stop ++ AAZ Z AA

ΛΛZZ ++ ππ --

FINUDA scientific programFINUDA scientific program

• comparison with the 6Li; available data of poor quality7Li

6Li • source of Λ4He and Λ

5He ( Λ6Li unstable) to study of the decay of

light hypernuclei

HeH

pHHe

ddHe

nnHeHe

nnHeHe

pnHHe

44

34

4

46

35

35

• reference target for spectroscopy and weak decay studies• expected over 105 events in the excitation spectrum• search for weakly excited states, ≤ 10-5/Kstop

(present limit 10-4/Kstop)• weak decays: Γp (Λp →→ n p)

Γn (Λn →→ n n) Γpn (Λ n p →→ n n p) New

Γnn (Λ n n →→ n n n) New

Γπ- (Λ →→ p π-)

12C

• never studied before• measurement of the capture rate in medium A hypernuclei

27Al

• no measurements available with K- at rest, useful for weakdecay studies

• important to assess the capture rate for medium and heavyA hypernuclei

51V

Accelerator

Complex

DADAΦΦNE Complex NE Complex energy 510 MeV

Design Luminosity

5 1032 cm-2 s-1

X(rms) 2.11 mm

y(rms) 0.021 mm

z(rms) 35 mm

Bunch length 30 mm

Crossing angle 13 mrad

Frequency (max) 368.25 MHz

Bunch/ring Up to 120

Part./bunch 8.9 1010

Current/ring 5.2 A (max)

FINUDA

KLOE

Mechanical support (Mechanical support (clessidraclessidra))Straw tubes, LMDC, Vertex/targetStraw tubes, LMDC, Vertex/target

Magnet end-capMagnet end-cap

Magnet yokeMagnet yokeB=1.0 TB=1.0 T

TOFONE detectorTOFONE detector

FINUDA DetectorFINUDA Detector

FINUDA Interaction RegionFINUDA Interaction Region

Be 500μm

2mm Sci.

Vanadium target profile

Aluminum target profile

Carbon target profile

Lithium target profiles

200.00

44.10210.0044.10

26.0

1.7

0

0.0

3

4.7

0

0.0

3

244.00

244.00

27.10

3.7

0

2.6

02

.60

4.1

027.10

27.10

27.10

4.7

0

1.0

0

4.7

0

0.6

0

3.3

25

0.0

3

2.6

0

210.00

200.00

44.1044.10

0.6

25

2.6

0

210.00

200.00

1.0

0

44.1044.10

3.7

0.0

3

Targets

3 12C1 51V1 27Al2 6Li 1 7Li

FINUDA first runFINUDA first run : October 2003 – March 2004 : October 2003 – March 2004

pb-1

nb-1

Integrated　luminositydelivered　to　FINUDA　Integrated　luminositydelivered　to　FINUDA　

FINUDA

FINUDA

Daily integrated luminosity [nbarn-1]

Integrated luminosity [nbarn-1]

From 14-Oct- 2003 to 22-Mar-2004 DAΦNE delivered 250 pb-1to IP233 pb-1 machine tuning10 pb-1 FINUDA debugging190 pb-1 useful data taking

From 14-Oct- 2003 to 22-Mar-2004 DAΦNE delivered 250 pb-1to IP233 pb-1 machine tuning10 pb-1 FINUDA debugging190 pb-1 useful data taking

DAΦNE peak luminosiy (cm-2s-1)

30∙106 events recorded30∙106 events recorded

FINUDA Detector performancesFINUDA Detector performances

• S.C. Solenoid: B = 1.0 T field homogeneity within 2% •Interaction/Target region: selection of K+- K- pairs , production and detection of hypernuclei.

• External tracking device: trajectories and momenta of charged particles with high precision Δp/p = 0.3%.

• External scintillator barrel: trigger purposes and neutron detection (10% eff. , 8 MeV en. Resol.)• Helium gas chamber: reduction of particle multiple scattering.

• S.C. Solenoid: B = 1.0 T field homogeneity within 2% •Interaction/Target region: selection of K+- K- pairs , production and detection of hypernuclei.

• External tracking device: trajectories and momenta of charged particles with high precision Δp/p = 0.3%.

• External scintillator barrel: trigger purposes and neutron detection (10% eff. , 8 MeV en. Resol.)• Helium gas chamber: reduction of particle multiple scattering.

LMDC: (r,) 150 m; z 1% wire length

ST: (r,) 150 m; sz = 500 m

LMDC: (r,) 150 m; z 1% wire length

ST: (r,) 150 m; sz = 500 m

z = 30 m ; en. res. 20% FWHM z = 30 m ; en. res. 20% FWHM

VDET z resolution

Outer TOF time resolutionFINUDA momentum resolution p/p is:

0.3% in He 1.5% in air

FINUDA momentum resolution p/p is:0.3% in He 1.5% in air

Pid in VDET

Distribution of stopped KDistribution of stopped K--

Reconstructed K- stopping points – external layer: 8 targets– inner layer: microstrip ISIM modules

Φ

7Li

6Li　

27Al　51V

12C12C

12C

6Li　

ISIM 7

ISIM 8

ISIM 1

ISIM 2

K　stopping in ISIM are about 10% of the total due to a boost (≈ 13 MeV) of the Φ in the x direction

K　stopping in ISIM are about 10% of the total due to a boost (≈ 13 MeV) of the Φ in the x direction

e+

e-

ΦΦ12.5 mrad

Λ -　hypClean hypernuclear structures can be seen in any target material

π- spectra coming form

different target materials

π- spectra coming form

different target materials

Experimental resultsExperimental results

π-spectrum contributions

Looking for protons from the Non-Mesonic Looking for protons from the Non-Mesonic ΛΛ decay decay

Particles coming from background processes can be easily

rejected requiring: dE/dx in the proton region; pπ- >240 MeV/c

all positive from

K- vertex 12C target 12C target

-1.8<BΛ<11.MeV

FINUDA future prospectsFINUDA future prospects

The Segmented Clover DetectorThe Segmented Clover Detector

BGO Comptonsuppression shield

Ge crystals

active collimator(scintillator)

Geometrical acceptancereduced to 72%

Geometrical acceptancereduced to 72%

@ L = 1033 cm-2 s-1 FINUDA can observe ~ 1.6 · 103 ev/h from YN g.s.@ L = 1033 cm-2 s-1 FINUDA can observe ~ 1.6 · 103 ev/h from YN g.s.

~ 1.87 · 103 ev/d~ 1.87 · 103 ev/d machine duty cycle: 75% spectrometer acceptance: 72% Ge acceptance: ~ 30% εGe: ~ 30%

machine duty cycle: 75% spectrometer acceptance: 72% Ge acceptance: ~ 30% εGe: ~ 30%

ConclusionsConclusions

Hypernuclear Physics has reached the status of a mature science

It helps in understanding BB weak and strong force allowing a detailed study into a SU(3) flavor symmetry environment

Some open problems still remain:

precise measurements of the spin-observables;

double Lambda hyp. binding force B;

Existence of neutron rich hypernuclei;

Survey on different targets of Γn /Γp.

Future activitiesFuture activities

• Jlab Hall A (HRS), Hall C (HKS)

• DAΦNE FINUDA 　 →　 DAΦNE2 with spect.

• KEK-PS, BNL-AGS (E930,E963,E964) SKS, Hyperball2,..

• J-PARC

　　　　　　 ・ Ξ hyp. Spectroscoy using K-K+ reaction

　　 ・ ΛΛ hyp. Study using π- seq. decay

• GSI PANDA

ΛΛ hyp. Ge spectroscopy

Bhabha events eBhabha events e++ e e-- e e++ e e--

e+

e

e+ e invariant mass (GeV/c)

Ks +

e+ e e+ e

0　　+　

KKss ++ -- eventsevents

-

+

Ks

-

+

Hypernuclear typical eventHypernuclear typical event

+

-

K-

K+

+

-

Momentum resolutionMomentum resolution

K+ +

K+ + o (205 MeV/c)

K+ μ+ νμ , π+πo

From the width of the μ+ the spectrometer momentum resolution is evaluated.

(236 MeV/c)

Δp/p 0.4%Δp/p 0.4%After mechanicalalignment

Δp/p 0.9%

K- n -

p -

K- p+ -

K- p- +

- n -

K- (NN)- N - n -

K- n0 -

TOT

Background contributionsBackground contributions