Study of Strangeness -1 and -2 hypernuclei

Radhey Shyam

CSSM, University of Adelaide, Australia and Saha Institute of Nuclear Physics, Kolkata, India

• A brief review and comparison of production reactions

• Introduction

• Brief sketch of the theoretical model

• Results, cross sections, spectroscopy • Conclusions

OUTLINE

What are Hypernuclei

Hypernuclei are nuclear systems where at least one nucleon in one of its orbits is replaced by A hyperon (e.g. ).

Z is a bound state of Z protons (A-Z-1) neutrons and a Λ hyperon

A

Λ

Hypernuclei are a laboratory to study the hyperon-nucleon, Hyperon-hyperon interactions.

Neutron Number

Stra

nges

s S = - 2, Hypernuclei at J-PARC, JAPAN by (K-, K+) reaction, No definite evidence for a bound state so far, hypernuclei

S = -1 So far: and , at BNL, KEK, FINUDA

Antihypertriton, RHIC, STAR Collaboration

hyperon can stay in contact with nucleons inside a Nucleus

Good probe for deeply bound single particle states.

Hyperons are free from Pauli principle restrictions

Can occupy quantum states already filled up with nucleons

ΛY 89

New type of nuclear matter, new symmetries, New selection rules. First kind of flavored nuclei.

Why are Hypernuclei interesting!

This makes a hyperon embedded in the nucleus a unique tool for exploring the nuclear structure.

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

The nuclear structure and the many body nuclear dynamics is extended to new non conventional symmetries, due to the inclusion of an S≠ 0 degree of freedom in the nucleus, YN interaction

Study of S = -1 hypernuclei ( or )

The Skyrme type N interaction from the known BE of hypernuclei.

The study of four fermion, strangeness changing, baryon-baryon weak interaction YN→NN, which can occur only inside hypernuclei

Neelam Guleria, S.K. Dhiman and R. Shyam, Nucl. Phys. A (to be published)

The role played by quark degrees of freedom in nuclear phenomena: Quark-Meson coupling model, extended for hypernuclei

Guichon, Tsushima, Saito, Thomas

S = -2 systems

• For a detailed understanding of the quark aspect of the baryon-baryon forces in the SU(3) space, information on the YY channel is essential.

New Physics items

• Search for H particle

Neutron star composition

• Are there S=-2 deeply bound K states ??

six-quark system uuddss

Conjectured composition of a neutron star

• Formation of compact stars depends On the nature of the YY interaction.

Juergen Schaffner-Bielich, Nucl. Phys. A804 (2008) 309

Production of a hypernucleus

γ

γ

γ

strangeness deposition

FINUDA stopp

Ad

Ae

KKZ ZK

e eπ

+ − −

−Λ

+

−

+ → Φ → +

+ → +

Strangeness exchange

(K_, p-) ,(K

_, p0)

BNL,KEK

electroproduction (e,e´K+) , Jlab, (g,K+)

MAMI-C, Mainz

target nucleus

strangeness production (p+, K+), (p-, K0) BNL,KEK,(GSI)

(K-,K+) J-PARC

Low momentum transfer

Momentum transfer > pF

Large Momentum transfers

12C

KINEMATICS

Momentum transfer > pF

Excitation Energy Spectra

(K–, π–) substitutional 0+

state dominates

(π+, K+) non-substitutional 1–

and 2+ states dominate

(γ, K+) unnatural parity states dominate

GS: (p3/2-1,s1/2

Λ ) 1–,2– (p3/2-1,p3/2

Λ ) 0+ 1+,21+,3+ (p3/2

-1,p1/2Λ )1+,22

+

Production processes for reactions leading to S=-1 hypernuclei

Target emission Projectile emission A (p,K+)ΛB

A (π+,K+)ΛB* A (γ,K+)ΛB′

N * (1650), N*(1710), N*(1720) baryonic resonances.

+

Production process of Cascade (S=-2) hypernuclei

S-channel and u-channel diagrams for elementary reaction

Cascade Hypernuclear production in s-channel

(1116), (1189), (1405), (1670), (1180), (1890), (1520), (1750), (1385), (1670)

Covarient Description of A (hγ,K+) YB reaction, Effective Lagrangian model

Effective Lagrangians at Meson-baryon-Resonance vertices

Bound state nucleon (hole) and hyperon (particle) spinors Initial and final state interactions (distorted waves).

Medium modification effects of Resonances

Coupling constants, form-factors (from the description of elementary reaction)

All calculations in momentum space, so nonlocalities are included.

Propagators for resonances (spin-1/2, spin-3/2)

A typical amplitude

Pi Pi

q

PK

PK

PN* q

Effective Lagrangian model for γ p → K Λ reaction

R. Shyam, K. Tsushima, A.W. Thomas, Phys. Lett. B676 (2009) 51

Effective Lagrangian model for the p (K-,K+ ,0 ) - (0)

The information about the coupling constants is very scanty From SU(3) model, old experimental determinations

R. Shyam, Olaf Scholten and A.W. Thomas, Phys. Rev. C84 (2011) 042201(R)

(1116), (1180), (1405), (1520), (1670), (1890), (1189), (1385), (1670), (1750)

Intermediate state LIJ M Width gKRN gKR (R) (GeV) (GeV) ------------------------------------------------------------------------------- 1.116 0.0 -16.750 10.132 1.189 0.0 5.580 -13.500 (1405) S01 1.406 0.050 1.585 -00.956 (1670) S01 1.670 0.035 0.300 -00.182 (1810) P01 1.180 0.150 2.800 02.800 (1890) P03 1.890 0.100 0.800 00.800 (1520) D03 1.520 0.016 27.46 -16.610 (1750) S11 1.750 0.090 0.500 00.500 (1385) P13 1.383 0.036 -6.22 -06.220 (1670) D13 1.670 0.060 2.80 02.800

Elementary reactions for - production, Role of resonances

R .Shyam , O. Scholten, A. W. Thomas, Phys. Rev. C 84 (2011) 042201

Momentum space Dirac Eq.

Bound state spinors A mean field approach, Phenomenological, OR QMC

Bound Hypernuclear wave spinors

In the region of the momentum transfer of interest, the lower component of the spinor is not negligible.

Cascade bound states

Phenomenological and quark-meson Coupling models

A(π+,K+)B reactions

S. Bender, R. Shyam and H. Lenske, Nucl. Phys. A839 (2010) 51

12C(+, K+)12C

1-

2+

1-

12C(+, K+)12C

89Y

Differential cross sections: 12C (γ, K+) ΛB

1- , 2- ⇒ (1p3/2, 1s1/2) -p Λ

2+ , 3+ ⇒ (1p3/2, 1p3/2) -p Λ

R. Shyam, K. Tsushima, A.W. Thomas, Phys. Lett. B676 (2009) 51

Phenomenological model

Quark Meson Coupling model

Unnatural parity states of highest J strongly excited

R. Shyam, H. Lenske and U. Mosel, Phys. Rev. C 77, (2008) 052201 (R)

Bound state Excitation Spectrum of 16N

Cross section for - hypernuclear production

R. Shyam, K. Tsushima and A.W. Thomas, Nucl. Phys. A (in press)

qmc Phen.

Cross section for -hypernuclear production

Dover and Gal, Ann. Phys. 146 (1983) 256 R. Shyam, K. Tsushima and A.W. Thomas, Nucl. Phys. A (in press)

Difference between Old and our New results

SUMMARY AND OUTLOOK

A(hγ,K+)ΛB reactions provide mutually complimentary information about the hypernuclear spectrum.

A fully covariant description of these reactions is desirableand is possible.

(γ,K +), (γ*,K +) strongly excite the unnatural parity stretched states.

Tighter constraints on the models of Λ-N interaction

We developed a new description of the cascade hypernuclear production via (K-, K+) reaction that is based on the mechanism of hyperon resonance excitation and decay. New calculations differ significantly from the older one.

New Measurements are needed for some key quantities to resolve the differences between the two calculations. J-PARC facility should be ideal for this purpose.

ℓKBR1/2 = -gKBR1/2 ΨR1/2 [ i ΦK + ((1-)/M) γμ (∂μΦK)]ΨB

= 5 even parity resonance, 1 odd parity resonance

ℓKBR3/2 = - gKBR3/2 ΨR3/2 ∂μΦKΨB + h.c.

scattering states

Φpf (pK) = δ (pK0 – EK) ∑ℓ m (- ) ℓ Yℓm (pf ) Y*ℓm (pK ) Fℓ (pK )

Fℓ (pK) = ∫ jℓ (pK r) ƒℓ (pf ,r) r2 dr

800 MeV/c 2EVK(r) = -Ab0k2 ρ(r)+Ab1∇.ρ∇

b0 and b1 are parameters of the potential

Kaon optical potential

This provides ƒℓ (pf ,r)

(γ,K+) reaction on Nuclei K+ is weakly absorbing so reaction occurs deep in the nuclear interior.

Unnatural parity states strongly excited

γp→ΛK+ reaction well understood within an effective Lagrangian picture

A proton is converted into a Λ, produces neutron rich hypernuclei.

Excitations of N*(1650), N*(1710), N*(1720) resonances.