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HADRON@FAIR FIAS June 25 -2 7 , 200 8. Volodymyr Magas. Two and three nucleon absorption of. the antikaon in nuclei. Collaboration:. V. Magas, Angels Ramos. University of Barcelona, Spain. Eulogio Oset. Hiroshi Toki. University of Valencia, Spain. RCNP, Osaka University, Japan.

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slide1

HADRON@FAIR

FIAS

June25-27, 2008

Volodymyr Magas

Two and three nucleon absorption of

the antikaon in nuclei

slide2

Collaboration:

V. Magas, Angels Ramos

University of Barcelona, Spain

Eulogio Oset

Hiroshi Toki

University of Valencia, Spain

RCNP, Osaka University, Japan

Phys.Rev.C74 (2006) 025206

Phys.Rev.C77 (2008) 065210

slide3

Goals

  • Critical review of some claims of observed deeply
  • bound antikaonstates in nuclei
  • - Present a conventional explanation of the data
  • Attempt to extract new physics from the data,
  • even if experiment has been done for reasons which
  • are not supported a posteriori
slide4

K N interaction

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

more channels,

next-to-leading order,

Born terms beyond WT (s-channel, u-channel),

fits including new data

Oset, Ramos, NP A635 (1998) 99

Oller, Meissner, PL B500 (2001) 263

Lutz, Kolomeitsev, NP A700 (2002) 193

Garcia-Recio et al., PR D67 (2003) 076009

Lutz, Kolomeitsev, NP A700 (2002) 193

Borasoy, Nissler, Weise, PRL 94 (2005) 213401; EPJ A25 (2005) 79

Oller, Prades, Verbeni, PRL 95 (2005) 172502

J. A.Oller, EPJ A28 (2006) 63

Borasoy, Meissner, Nissler, PR C74 (2006) 055201

slide5

A moderate attraction of about -40 MeV at r0 is obtained

Ramos, Oset, NP A671 (2000) 481

Tolós, Ramos, Oset, PR C74 (2006) 015203

Similar results for optical potentials:

Schaffner-Bielich, Koch, Effenberber, NP A669 (00) 153

Cieply, Friedman, Gal, Mares, NP A696 (2001) 173

slide6

If true -- New era in nuclear physics

Critical review can be found in

Oset, Toki, Phys.Rev.C74 (06) 015207Ramos,Magas,Oset,Toki,Nucl.Phys.A804 (08) 219

slide9

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 [K- pnn] bound system…  BK =197 MeV

New experiment with a more precise measurement:

only a broad bump remains Sato et al., PL B659 (2008) 107

slide10

A conventional explanation

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

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

do not absorbe energy nor momentum

from the probe

Fermi motion + mometum conservation explain the peak width

Ramos, Magas, Oset, Toki, Nucl. Phys. A804 (08) 219

slide11

Oset-Toki’s prediction:

Such a peak should be seen in other light or medium nuclei, and

it should be narrower and weaker as the nuclear size increases

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

slide12

6Li

4He

The FINUDA proton missing mass experiment:

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

This view is consistent with the observation by

the 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 S- are emitted back-to-back)

allow them to conclude that the reaction:

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

slide14

FINUDA experiment

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

Nuclei:

  • The same elementary reaction as in KEK: K- p p  L p
  • (select pL > 300 MeV/c to eliminate K- N  L p)
  • But here both emitted particles are detected!
  •  the invariant mass of the Lp pair is measured, MLp
slide15

FINUDA results

Interpreted by the

FINUDA experiment

as a (K-pp) bound state

Transition to the g.s. of daughter nucleus

slide16

Conventional explanation

Magas, Oset, Ramos, Toki, PRC 74 (06) 025206 –

a conventionalexplanation:

+

Final StateInteractions (FSI) of theprimaryL and p (producedafter K- absorption) as theycrossthedaughternucleus!

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

slide17

Conventional explanation

A conventional explanation:

Final State Interactions (FSI) of the primary L and p (produced after K- absorption) as they cross the daughter nucleus!

Discarded by FINUDA on the basis of back-to-back correlations

slide18

Our calculations

Monte Carlo simulation of K- absorption by

pp and pn pairs in nuclei

  • The K- is absorbed mainly from the lowest atomic orbit for which the energy shift has been measured
slide19

K- wave function

S. Hirenzaki, Y. Okumura,

H. Toki, E. Oset and A. Ramos,

Phys. Rev. C61, 055205 (2000)

slide20

The K- is absorbed by two nucleons with momenta randomly chosen

  • within the local Fermi sea:
  • Primary L and N are emitted accordingly to PS:

Our calculations

Monte Carlo simulation of K- absorption by

pp and pn pairs in nuclei

  • The K- is absorbed mainly from the lowest atomic orbit for which the energy shift has been measured
slide21

K-pN  N process

Nuclear density profile and overlap

The K− absorption width from pN pairs in a nucleus is given in first approximation by

PRC 50, 2314

is the in-medium decay width for the process

slide22

The K- is absorbed by two nucleons with momenta randomly chosen

  • within the local Fermi sea:
  • Primary L and N are emitted according to PS:

Our calculations

Monte Carlo simulation of K- absorption by

pp and pn pairs in nuclei

  • The K- is absorbed mainly from the lowest atomic orbit for which the energy shift has been measured
  • Further collisions of L and N as they cross the nucleus according to
  • a probability per unit length sr with sL~2sN/3
slide23

The K- is absorbed by two nucleons with momenta randomly chosen

  • within the local Fermi sea:
  • Primary L and N are emitted according to PS:

Our calculations

Monte Carlo simulation of K- absorption by

pp and pn pairs in nuclei

  • The K- is absorbed mainly from the lowest atomic orbit for which the energy shift has been measured
  • Further collisions of L and N as they cross the nucleus according to
  • a probability per unit length sr with sL~2sN/3
  • Finally, the invariant Lp mass is reconstructed from the final events, experimental cuts are applied
slide24

First (narrow) peak:

Transition to the g.s. of daughter nucleus

for the light nuclei

Our model is not really suitable to reproduce this peak

we made a rough estimate of 10% of all events

Nucleons move in mean field Thomas-Fermi potenti al:

only for

the holes

- ,

such that the maximum ΛN invariant mass allowed by our model

=

=15-16 MeV (Li), 9.6 MeV (V)

slide25

Second (wider) peak:

Quasi-elastic peak (QEP) after K- absorption

A peak is generated in our Monte Carlo simulations: the primary

L and p (produced after K- absorption) undergo quasi-elastic collisions with the nucleus exciting it to the continuum

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

(The QEP comes mostly from one collision of the particles exciting the nucleus to the continuum)

  • The QEP accounts for the second peak of

the FINUDA experiment!

slide26

Results:

Back-to-back

Allowing up to three collisions

Compare to

FINUDA

data

slide27

Results:

Angular correlations

Our

Estimate:

10 %

slide31

What have we learned?

We can study the FSI for different nuclei

slide34

FINUDA experiment

M. Agnello et al. Phys. Lett. B654 (2007) 80-86

slide35

FINUDA results

No peak – because it is smeared out by the FSI

M. Agnello et al. Phys. Lett. B654 (2007) 80-86

slide36

Evolution of the FINUDA ideas

Interpreted by the

FINUDA experiment

as a (K-pp) bound state

Transition to the g.s. of daughter nucleus

slide37

Evolution of the FINUDA ideas

Now they learned that FSI is important

for large nuclei

slide38

Magas, Oset, Ramos, Toki, PRC 77 (08) 065210

We suggest a conventional explanation:

K- absorption by three nucleonsleaving

the other nucleons as spectators

slide39

Magas, Oset, Ramos, Toki, PRC 77 (08) 065210

We suggest a conventional explanation:

K- absorption by three nucleonsleaving

the other nucleons as spectators

n

p

n

K

n

p

p

L

p

n

slide40

Our model

n

p

n

K

n

p

p

L

p

n

slide41

Results:

Good agreement with the data!

slide44

Conclusion

We have shown that there are (so far?) no experimental evidences of deeply bound K- state in nuclei

All “signals” of deeply bound state can be explained

in conventional scheme:

K- absorption by two or three nucleons leaving the others as spectators

+ Final State Interaction for heavy nuclei

However, the FINUDA data allows to study in

details the two and three nucleon K- absorption

mechanisms

slide45

K in a nuclear medium:

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

free

(repulsive)

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

medium

(attractive)

K

K

p

Pauli blocking

Weise, Koch

K

K

p

Self-consistent kaon dressing

Lutz

K

K

p

pion and kaon dressing

Ramos,Oset

slide46

FINUDA results

We give a conventional explanation:

Final State Interactions (FSI) of the primary L and p (produced after K- absorption) as they cross the daughter nucleus!

C(p,p’) H(p,p’)

2

12

slide47

K-pN  N process

Fermi sea

 const,

And finally

where

slide48

FSI of the primaryN

where kernel describes further propagation

ofLand N as they cross the nucleus according to

a probability per unit lengthsrwithsL~2sN/3

p

L

L

p

p

L

slide49

First (narrow) peak:

Transition to the g.s. of daughter nucleus

How much strength should we expect?

Our estimate:

Formation probability(FP)xSurvival probability (PS)

7Li (pp)-1  5H

In light nuclei: FP ~ | 0.3 - 0.7 |2 = 0.1–0.5, PS ~ 0.6 (Li), 0.4 (C) 0.1-0.3

In heavier nuclei: FP increases, but PS decreases: ~0.26 (Al), 0.18 (V)

also below 30%

slide50

Can the peak be due to other processes?

A)

followed by

This peaks around 2170 MeV (where there is indeed a small third

peak in the experiment) and has a smaller strength than

B)

followed by

 located in the region of the QEP and all events back-to-back,

but strength is small, ~ 10-30% of events