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
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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
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
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
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!
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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
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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
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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
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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
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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
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
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(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)
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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