11

Àngels RamosÀngels Ramos

Recent Progress in Many-Body Theories 14Recent Progress in Many-Body Theories 14

Barcelona, July 16-20, 2007Barcelona, July 16-20, 2007

33

Strangeness nuclear physics is a field that emerged after the discover of the strange particles (,K-,K+) in 1947.

It has experienced an steady progress in major laboratories across the world

CERN (Europe)Brookhaven (USA)KEK (Japan)

Jlab (USA)FiNUDA@DAPHNE (Italy)MAMIc@Mainz (Germany)

J-PARC (Japan)HypHI@FAIRPANDA@FAIR

Past(1970-2005)

Present

Future2008

2012?

(in lates 50’s emulsions, from 70’s colliders)

44

This field studies nuclear phenomena involving one or more strange particles (containing the s quark or antiquark)

This talk will focuss on:

HYPERNUCLEIKAON PHYSICSNEUTRON STARS (briefly)

55

The hypernuclear chart as of 1989

And almost 20 years later: basically the same hypernuclei … but measured with better statistics and energy resolution excited hypernuclear states are now available!

HYPERNUCLEI

66

77

(K- ,

- ) (

+ ,K+ )

(,K+ )

A A

PRODUCTION OF HYPERNUCLEI(collider era)

Strangeness exchange: CERN, BNL, KEK, DAPHNE

Associated production: BNL, KEK

Electroproduction: JLab

88

n

Fixing the indicent beam energy and the detection angle, the energy of the emitted meson (K+) is directly related to the binding energy

H. Hotchi et al., PRC64 (2001) 044302

99U

c

RN

See e.g. D.J. Millener, C.B. Dover and A. Gal, Phys. Rev. C38 (1988) 2700

1010

6 MeV ~6 MeV

neutron spin orbit: 6 MeV

neutron PLUS hyperon spin orbit: ~ 6 MeV

W. Brückner et at, Phys. Lett. 55B(1975)107

Spin-orbit potential for the hyperon is very weak!

Spin-orbit potential

1111

Isospin = 0Isospin = 1

Th. A. Rijken, Y. Yamamoto, V.G.J. Stoks, PRC59 (1999) 21

B. Hozelkamp, K. Holinde, J. Speth, NPA500 (1989) 485

M.M. Nagels, Th.A. Rijken, J.J. de Swart, PRC40 (1989) 2226

Juelich A,B

Nijmegen NSC89

Nijmegen NSC97

Fitted to: 4300 data on NN scattering

35 data on YN scattering + SU(3)

YN interaction (bare)

J. Haidenbauer, U.G. Meissner, PRC72 (2005) 044005

Th. A. Rijken, Y. Yamamoto, V.G.J. Stoks, PRC73 (2006) 044008

H. Polinder, J. Haidenbauer, U.G. Meissner, NPA779 (2006) 244Juelich (EFT)

Nijmegen ESC04

1212

Total cross sections for YN scattering

1313

Effective YN interaction (G-matrix: microscopical approach)

B1

B5

B3

B2

B6

B4

B1

B3 B4

B2

G

B1

B3 B4

B2

V

= +

Bi

Bi

Bj

Coupled channel problem!S=-1: N,NS=-2: ,N,

I. Vidaña, A. Polls, A. Ramos and M. Hjorth-Jensen, Nucl. Phys. A644 (1998) 201

I. Vidaña, A. Polls, A. Ramos and H.-J. Schulze, Phys. Rev. C64 (2001) 044301

Medium effects:Pauli blockingBaryon dressing

YN models explain the depth of the nucleus potential

the spin-dependence varies considerably in the different YN models apreciable differences in the spectra of hypernuclei!

1414

New info from precise -ray (coincidence) experiments !

BNL E930, Tamura speakperson

H. Akikawa et al, PRL88 (2002) 082501

The new generation of experiments performed in the last 5 years have disclosed many interesting aspects of hypernuclear structure crucial information for constraining the YN interaction!

Nijmegen NSC97f spin-orbit splitting in 9Be: 150-200 keV

E.Hiyama et al., PRL85 (2000) 270

Nijmegen ESC03 spin-orbit splittings in 9Be: ~ 80 keV

1515

Sigma-hypernuclei

Narrow states in spite of NN conversion?

R. Bertini et al, Phys.Lett 83B (1979) 306

S. Bart et al, Phys. Rev. Lett 83 (1999) 5238

Not confirmed with better statistics!

1616

(K- ,

- ) (

+ ,K+ )

(,K+ )

A A

WEAK HYPERNUCLEAR DECAY

Weak decay of hypernuclei allows to obtain new and complementary information on the properties of hypernuclei and the weak YN interaction

Hypernuclear structure

1717

N

N

N

N

MESONIC

NON-MESONIC

n: n n n

p: p n p

: pkN~100 MeV/c < kF

: n

Pauli blocked!

kN~400 MeV/c

2: N N n N N

NN~~~

N

N

N kN~340 MeV/c

T= M + NM = + + n + p +2

WEAK HYPERNUCLEAR DECAY

1818

free : free= 3.8 109 s -1

Hypernuclear width: T ~ free

Observed decay rates

BNL, 91

KEK, 95, 98

Jülich, 93, 97, 98

free/

free =1.78 ~ 2 I=1/2 !

free : p

free : n

1919

The emerging nucleons are very energetic and this process is not sensitive to nuclear structure details

Q ~ m - mN ~ 175 MeV

Ideal process to characterize the baryon-baryon weak interaction!

S=1 S=0

NON-MESONIC DECAY: N N N

In particular, for processes having S=1 (NNN), the PC amplitude is not masked by the strong interaction like in the case S=0 (NNNN)

Both PC and PV weak amplitudes can be studied from hypernuclear weak decay

Only the PV amplitudes are accessible

W.M. Alberico and G. Garbarino, Phys. Reports 369 (2002) 1E. Oset and A. Ramos, Prog. Part. Nucl. Phys. 41 (1998) 191

2020

Non-mesonic processes: n: n n n

p: p n p

weak interacction: meson exchange: ,K,,K*

quark models

strong interaction between initial N and final NN pair

Decay width 1=n+p well reproduced by all models but…

not the ratio n/p !

OPE mechanism dominated by tensor transitions

3S1 3D1

N NN

Antisymmetry requires isospin I=0nn pairs are in isospin I=1 n: n nn supressed in OPE!

2121

0 0.5 1 1.5 2

n/p

BNL, 91

KEK, 95

KEK, 02

BNL, 91

Theoretical models

A. Parreño, A. Ramos and C. Bennhold, PRC 56 (1997) 339

D. Jido, E. Oset and J. E. Palomar, NPA 694 (2001) 525

K. Itonaga, T. Ueda and T. Motoba, PRC65 (2002) 034617

K. Sasaki, T. Inoue and M. Oka, NPA 669 (2000) 331

. . .

A challenge in hypernuclear weak decay for many years!

A realistic analysis of np must consider:

1. The influence of the 2-nucleon induced decay (2)

Nn = p + 2 n + 2 2

Np = p + 2

p

p

n

n n

n

n n

p

n p

2. The final state interaction (FSI) of the primary nucleons

A. Ramos, M.J. Vicente-Vacas and E. Oset, PRC55 (1997) 735-743; Erratum: ibid. C66 (2002) 039903

A. Ramos, E. Oset and L.L. Salcedo, PRC50 (1994) 2314

The primary nucleons produced in the weak decay continuously change energy, direction, charge and new secondary nucleons are emitted.

Theoretical improvements

2323

Measuring distributions of NN pairs in coincidence permits a better determination of the ratio n/p .

The more exclusive measurement of final states:

Reduces contamination from the process 2: NN NNN

Eliminates some FSI effects

Angular correlations12

Energy correlations: T1+T2

T1

T2

Experimental improvement: NN coincidences

Single proton spectra

Neutron spectrum

Angular correlation between n and p pairs

Kinetic energy correlations between np pairs

B.H. Kang et al., Phys. Rev. lett. 96 (2006) 062301

Without FSI and ignoring 2:

With FSI:

Nnn, Nnp: number of nucleon-nucleon per weak decay (after FSI)

G. Garbarino, A. Parreño and A. Ramos, PRL 91, 112501 (2003)

The n/p problem has been solved!

n n n

p n p

3030

+ n K+

New challenge in hypernuclear decay: Asymmetry

12C

y: polarization axis

K

p

n 0.5

0

-0.5

-1

E278

E462

E508

a

K. Sasaki, T. Inoue, M.Oka, Nucl. Phys. A707 (2002) 477

A. Parreño and A. Ramos, Phys. Rev. C65 (2002) 015204

W. Alberico, G. Garbarino, A. Parreño and A. Ramos, Phys. Rev. Lett. 94 (2005) 082501 (FSI)

An EFT study has revealed the dominance of an scalar (J=0) and isoscalar (I=0) contact term which is crucial to reproduce the small value of the asymmetry parameter a

This term can be interpreted as coming from the exchange of the broad meson (J=0,I=0). M ~ 450 MeV

A. Parreño, C. Bennhold and B.R. Holstein, Phys. Rev. C70 (2004) 051601(R)

D. Jido, E. Oset, J.E. Palomar, Nucl. Pys. A694 (2001) 525

Recent improvements:

From a fundamental point of view, the meson is dynamically generated from correlated two-pion exchange

OMEOME+2

C. Chumillas, G. Garbarino, A. Parreño, A. Ramos,, e-Print: arXiv:0705.0231 [nucl-th]

3333

(ANTI)KAONS IN THE MEDIUM

The K- feels attraction in the medium

Kaon condensation in neutron stars?D.B. Kaplan and A.E. Nelson, Phys. Lett. B175 (1986) 57G. E. Brown and H. A. Bethe, Astrophys. Jour. 423 (1994) 659

e

2

200

(MeV)

K

31

400

Kaons are bosons a condensate of (anti)kaons would appear

Best fits to kaonic atoms seem to prefer UK~ - 200 MeV at 0

K-

A

E. Friedman, A. Gal, and C.J. Batty, NPA 579 (1994) 518

Phenomenology:

3535

In the S=-1 strangeness sector (1405) resonance 27 MeV below K-p thresold

Coupled-channel Bethe-Salpeter equation

= +Tij = Vij + Vil Gl Tlj

Mj

BjBi

Vij =

Mi

KKN

1255 1331 1435 1663 1741 1814 (MeV)

1)

2)

Microscopic theory:

Implement Unitarity

Take an elementary KN interaction (e.g. from Chiral Lagrangian)

3636

Since the pioneering work of Kaiser, Siegel and Weise [Nucl. Phys. A594 (1995) 325] many other chiral coupled channel models have been developed.

E. Oset and A. Ramos, Nucl. Phys. A635 (1998) 99J.A. Oller and U.G. Meissner, Phys. Lett. B500 (2001) 263M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A700 (2002) 193C.Garcia-Recio et al., Phys. Rev. D (2003) 07009 M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A700 (2002) 193

more channels,next-to-leading order,Born terms beyond WT (s-channel, u-channel),Fits including new data…

B.Borasoy, R. Nissler, and W. Weise, Phys. Rev. Lett. 94, 213401 (2005); Eur. Phys. J. A25, 79 (2005) J.A. Oller, J. Prades, and M. Verbeni, Phys. Rev. Lett. 95, 172502 (2005)J. A.Oller, Eur.Phys.J.A28, 63 (2006)B. Borasoy, U. G. Meissner and R. Nissler, Phys.Rev.C74, 055201,2006.

3737

K in a nuclear medium:The presence of the (1405) resonance makes the in-medium KN interaction to be very sensitive to the particular details of the many-body treatment.

we’d better do a good job! (SELF-CONSISTENCY)

Pauli blocking

free(repulsive)

medium(attractive)

Self-consistent kaon dressing

pion and kaon dressing

K

K

K

K

K

K

Weise, Koch

Ramos,Oset

Lutz

3838

and kaonic atom data are also well described!

S. Hirenzaki et al., PRC61 (2000) 055205A. Baca, C. García-Recio, J. Nieves, NPA 673 (2000) 335

Microscopic models moderate attraction for the K-nucleus potential!

A. Ramos and E. Oset, NPA 671 (2000) 481

Kaonic atom data are not sensitive to the K-nucleus potential at 0

only the nuclear surface (up to~0/4) is explored!

3939

Deeply bound kaonic nuclear states?

In spite of te relatively shallow potentials (UK = -70 to -50 MeV) predicted by various self-consistent many-body approaches:

there has been high expectations about the existence of deeply bound kaonic states triggered by the work of Akaishi and Yamazaki

Y.Akaishi, T.Yamazaki, Phys.Rev.C65,044005 (2002)

Simple local KN- potential:

+simplified many-body treatment (self-consistency ignored)

Subsequent few body calculations (variational): Y.Akaishi, A. Dote, T.Yamazaki,Phys.Lett.B613, 140 (2005)

nucleus shrinked enourmously ((0)~100!) and BK = 169 MeV in ppn-K- (T=0) BK = 194 MeV in pnn-K- (T=1)

A. Ramos, E. Oset, Nucl. Phys. A671, 481 (2000)L. Tolós, A. Ramos, E. Oset, Phys. Rev. C (2006)J. Schaffner-Bielich, V.Koch, M. Effenberber, Nucl. Phys. A669, 153 (2000)A.Cieply, E.Friedman, A.Gal, J.Mares, Nucl. Phys. A696, 173 (2001)

4040

The KEK proton missing mass experiment:

T. Suzuki et al., Phys. Lett. B597, 263 (2004)

S0 is a tribaryon with S = -1 and T = 1

If interpreted as a pnn-K- bound system… BK = 197 MeV

formation rate: 1% per absorbed K-

But withdrawn in a recent reanalysis of data (Iwasaki, HYP06)

arXiv:0706.0297[nucl-ex]

4141

Conventional view:

K- absorption by two nucleons leaving the other nucleons as spectators

E. Oset, H. Toki, Phys. Rev. C74, 015207 (2006)

do not absorbe energy nor momentum from the probe

some Fermi motion broadening is possible, it would explain the ~60 MeV/c peak spreading

4242

The FINUDA proton missing mass experiment:

M. Agnello et al, Nucl. Phys. A775, 35 (2006)

This view is consistent with the observation bythe FINUDA collaboration of a peak in the proton missing mass spectrum at ~ 500 MeV/c(from K- absorbed in 6Li)

A study of the angular correlations (p and - are emitted back-to-back) allow them to conclude that the reaction:

in 6Li is the most favorable one to explain their signal

6Li4He

4343

Another FINUDA experiment: measuring the (p) invariant massM. Agnello et al. Phys. Rev. Lett. 94, 212303 (2005)

But here both emitted particles are detected! (not just the proton)

the invariant mass of the p pair is measured, Mp

The same elementary reaction takes place: K- p p p (select p > 300 MeV/c to eliminate K- N

A peak for the transition to the g.s. of the daugther nucleus should be observed at:

Nuclei:

4444

Transition to the g.s. of daughter nucleus

Interpreted by the FINUDA experiment

as a (K-pp) bound state

M. Agnello et al. Phys. Rev. Lett. 94, 212303 (2005)

Another view (conventional):Final State Interactions (FSI) of the primary and p (produced after K- absorption) in their way out of the daughter nucleus!

4545

Monte Carlo simulation of K- absorption by pp and pn pairs in nuclei

Primary and N emitted according to phase space:

The K- is absorbed by two nucleons with momenta randomly chosen within the local Fermi sea:

The or N scatter within the nucleus, loosing energy and producing new (slow) nucleons

Finally, the invariant p mass is reconstructed from the final events

V.K. Magas, E. Oset, A. Ramos, H. Toki, Phys.Rev. C74, 025206 (2006)

4646

A peak is generated when the primary and p, undergo quasi-elastic collisions with the nucleus, exciting it to the continuum.

(it is the analogue of the quasi-elastic peak observed in nuclear inclusive reactions using a variety of different probes: (e,e’), (p,p’), (’),…)

4747

N.V. Shevchenko, A. Gal, J. Mares, Phys.Rev.Lett.98,08230 1(2007) (Fadeev)

A. Doté, W. Weise, nucl-th/071050 (Variational)

All the experimental claims for the existence of very deeply boundkaonic nuclear states can be explained in terms of conventionalnuclear physics processes.

This is further substantiated by NEW theoretical developments: realistic few body calculations of the K-pp system:

Crucial ingredient: realistic NN SRC (which prevent from reaching densities o!)

BK ~ 50-70 MeV ~ 100 MeV

4848

STRANGENESS IN NEUTRON STARS

Central density ~ c = (4 – 8) 0 (0 = 0.17 fm-3 = 2.8 1014 g/cm3)

Mass ~ 1.4 to 2.2 Msun

Radius ~ 10 km

Strangeness

confined form

deconfined form

hyperons: -,

kaons: K-

strange quark matter

u d s

4949

The central density of a neutron star is highc = (4 – 8) 0 (0 = 0.17 fm-3 = 2.8 1014 g/cm3)

The nucleon chemical potential increases very rapidly with density

Above a threshold density, T = (2– 3) 0 , hyperons are created in the stellar interior!

HYPERONS IN NEUTRON STARS HYPERONIC MATTER

First proposed in 1960: V.A. Ambartsumyan, G.S. Saakyan, Sov. Astron. AJ. 4 (1960) 187

The core of a neutron star is a fluid of neutron rich matter in equilibrium with respect to the weak interactions (-stable nuclear matter)

Why is it likely to have hyperons?

5050

-stable hadronic matter

Equilibrium with respect to weak interaction processes:

Charge neutrality:

5151

The Equation-of-State (EoS) of hyperonic matter

The presence of hyperons produces a softening in the EoS!

The composition of a neutron star depends on the hyperon properties in the medium (i.e. on the YN and YY interactions)

5252

Profile of a neutron star with hyperons

Neutron stars are “giant hypernuclei” under the influence of gravity and strong interactions

I. Vidaña, A. Polls, A. Ramos, L. Engvik and M. Hjorth-Jensen, Phys. Rev. C62 (2000) 035801

5353

Influence of hyperons:

lower maximum masses smaller radius higher central densities

need extra pressure at high densityThree-body forces: YNN, YYN, YYY ??

H. J. Schulze, A. Polls, A. Ramos, I. Vidaña, PRC 73, 058801 (2006)

Other degrees of freedom: quarks ??

Observational limit ~ 1.44 M3(but PSR0751+1807 (2005): 2.1 M3)

5454

STRANGENESS NUCLEAR PHYSICS is a fascinating field that adds a new dimension (strangeness) into conventionalnuclear physics and opens the door to investigate new phenomena associated to the enlarged flavour SU(3) world

Interdisciplinary field !

hypernuclear structure: properties of the YN, YY interactions the penetrates inside the nucleus

hypernuclear decay:

ASTROPHYSICS(neutron star interior)

mesonic mode

non-mesonic mode weak non-leptonic baryon-baryon interaction

NUCLEAR PHYSICS

PARTICLE PHYSICS