HADRON@FAIR FIAS June 25-27, 2008. Collaboration: Phys.Rev. C 74 (2006) 025206 Phys.Rev. C 77 (2008)...

HADRON@FAIRFIAS

June 25-27, 2008

Collaboration:

Phys.Rev. C 74 (2006) 025206Phys.Rev. C 77 (2008) 065210

- Critical review of some claims of observed deeply bound antikaon states 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

Goals

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:

Oset, Ramos, NP A635 (1998) 99Oller, Meissner, PL B500 (2001) 263Lutz, Kolomeitsev, NP A700 (2002) 193Garcia-Recio et al., PR D67 (2003) 076009

Lutz, Kolomeitsev, NP A700 (2002) 193Borasoy, Nissler, Weise, PRL 94 (2005) 213401; EPJ A25 (2005) 79 Oller, Prades, Verbeni, PRL 95 (2005) 172502J. A.Oller, EPJ A28 (2006) 63Borasoy, Meissner, Nissler, PR C74 (2006) 055201

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

A moderate attraction of about -40 MeV at 0 is obtainedRamos, 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

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

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

A conventional explanation

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

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

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

Oset-Toki’s prediction:

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

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

it should be narrower and weaker as the nuclear size increases

The FINUDA proton missing mass experiment:

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

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

FINUDA experiment

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

But here both emitted particles are detected!

the invariant mass of the p pair is measured, Mp

The same elementary reaction as in KEK: K- p p p

(select p > 300 MeV/c to eliminate K- N

Nuclei:

Interpreted by the FINUDA experiment

as a (K-pp) bound state

FINUDA results

Transition to the g.s. of daughter nucleus

Conventional explanation

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

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

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

Conventional explanation

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

S. Hirenzaki, Y. Okumura, H. Toki, E. Oset and A. Ramos,

Phys. Rev. C61, 055205 (2000)

K- wave function

Our calculations



Primary and N are emitted accordingly to PS:

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

Nuclear density profile and overlap

K-pN N processThe K− absorption width from pN pairs in a nucleus is given in first approximation by

is the in-medium decay width for the process

Our calculations



Primary and N are emitted according to PS:


Further collisions of and N as they cross the nucleus according to

a probability per unit length with ~2N/3

Our calculations



Primary and N are emitted according to PS:


Further collisions of and N as they cross the nucleus according to

a probability per unit length with ~2N/3

Finally, the invariant p mass is reconstructed from the final events, experimental cuts are applied


for the light nuclei

First (narrow) peak:

Our model is not really suitable to reproduce this peak

Nucleons move in mean field Thomas-Fermi potenti al:

- ,

such that the maximum ΛN invariant mass allowed by our model

=

only forthe holes

=15-16 MeV (Li), 9.6 MeV (V)

we made a rough estimate of 10% of all events

Quasi-elastic peak (QEP) after K- absorption

A peak is generated in our Monte Carlo simulations: the primary 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’), (’),…(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!

Second (wider) peak:

Allowing up to three collisions

Results:

Compare to FINUDA

data

Back-to-back

Angular correlations

Results:

Our Estimate:

10 %

Mixture of the light targets

What have we learned?

Results:


We can study the FSI for different nuclei

FINUDA experiment

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

FINUDA results

No peak – because it is smeared out by the FSIM. Agnello et al. Phys. Lett. B654 (2007) 80-86

Interpreted by the FINUDA experiment

as a (K-pp) bound state

Evolution of the FINUDA ideas


Evolution of the FINUDA ideas

Now they learned that FSI is important for large nuclei

We suggest a conventional explanation:

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

We suggest a conventional explanation:

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

pp

p

n

n

nK

np

pp

p

n

n

nK

np

Our model

Results:

Good agreement with the data!

Results:

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

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

We give a conventional explanation: Final State Interactions (FSI) of the primary and p (produced after K- absorption) as they cross the daughter nucleus!

FINUDA results

C(p,p’) H(p,p’)12 2

K-pN N processFermi sea

const,

And finally

where

p

p

p

FSI of the primary N

where kernel describes further propagation of and N as they cross the nucleus according to a probability per unit length with ~2N/3


How much strength should we expect?

Formation probability (FP) x Survival probability (PS)

In light nuclei: FP ~ | 0.3 - 0.7 |2 = 0.1–0.5, PS ~ 0.6 (Li), 0.4 (C) 0.1-0.3In heavier nuclei: FP increases, but PS decreases: ~0.26 (Al), 0.18 (V)

also below 30%

First (narrow) peak:

Our estimate:

7Li (pp)-1 5H

Can the peak be due to other processes?

followed by

This peaks around 2170 MeV (where there is indeed a small thirdpeak in the experiment) and has a smaller strength than

A)

B)

followed by

located in the region of the QEP and all events back-to-back,but strength is small, ~ 10-30% of events

HADRON@FAIR FIAS June 25-27, 2008. Collaboration: Phys.Rev. C 74 (2006) 025206 Phys.Rev. C 77 (2008)...

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Transcript of HADRON@FAIR FIAS June 25-27, 2008. Collaboration: Phys.Rev. C 74 (2006) 025206 Phys.Rev. C 77 (2008)...