Measurement of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow /><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>16</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>O(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w

Grion, N.; Rui, R.; Fm, Rozon; Anderl, Timo; Ernst, J.; Dr, Gill; Hanna, Melvin W.; Jj, Kraushaar; Johnson, R.R.; Olszewski, Robert; Sevior, M. E.; Sheffer, Gabriel; Smith, G. R.; Rp, Trelle; Wu, Zhizhou

doi:10.1103/physrevlett.59.1080

Cited by 18 publications

(10 citation statements)

References 18 publications

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“…Because of its scalar character, the detection of these pairs does not seem obvious. An indication might be provided by the recent study of (% 2r [8] where an enhanced cross-section has been found. In any case, reactions with two pions in the exit channel seem to be an appropriate tool.…”

mentioning

confidence: 95%

Bound two-pion Cooper pairs in nuclei?

Schuck¹,

Nörenberg

Chanfray

1988

Z. Physik A - Atomic Nuclei

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The possibility of bound two-pion (Cooper) pairs in a mtclear medium and their eventual Bose condensation is pointed out.. This stems from the fact that free ~" -lr scattering in the I = 0, l = 0 channel shows attraction and that the kinetic energy is strongly suppressed in matter through coupling to A -h intermediate states. Connections to the a meson in effective field theories for nuclear matter are discussed.Phase shift analyses of 7r -7r scattering in the I = 0, t = 0 channel show [1] that there is attraction between two pions. However, the force is too weak to give rise to a bound two-pion state. Possibly this situation changes when two pions scatter within nuclear matter. Indeed it is well known that there is suppression of the pion kinetic energy, and hence binding is favoured. This effect is due to the self-energy contributions from nucleon-hole and delta-hole excitations and expressed in the pion dispersion relation ~(v) = ~/m# + (1 + a)p~ _~ m~ + 2m; + '" (1) by the parameter a ~ -0.6 to -0.8 or the effective mass rn;/m~ ~-2 to 3 in normal nuclear matter [2]. We have used the pion dispersion relation (1) for in-medium ~r -~r scattering. This is of course not entirely correct since, as usual, the (uncorreIated) two-pion propagator is defined by the folding integral G~(E,g) = / dE' f d3q'D~(E-E',g-~)D~(E',~) (2)whenever the single-pion propagator D~ contains an energydependent selfenergy such as the one created from p -h or A -h bubbles which in fact lead to the value of a indicated above. Nevertheless, under the assumption that the one-pion propagator exhibits a well-defined pole, the folding integral (2) indeed reduces to the free two-pion propagator with w(p) given by (1) replacing the vacuum dispersion relation (a = 0).We therefore employed the T-matrix parametrization of Johnstone and Lee [1] (5) which reproduces perfectly the measured 500 phase shifts. For the scattering in nuclear matter we simply replace in (4) the vacuum dispersion relation by (1). In Fig. 1

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mentioning

confidence: 95%

Bound two-pion Cooper pairs in nuclei?

Schuck¹,

Nörenberg

Chanfray

1988

Z. Physik A - Atomic Nuclei

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“…This state would behave like a Cooper pair in the medium, with repercussions in several observable magnitudes in nuclear reactions [15]. The possibility that such effects could have already been observed in some unexpected enhancement in the ( ¾ ) reaction in nuclei [16] was also noticed there. More recent experiments where the enhancement is seen in the · channel but not in the · · channel [17] have added more attraction to that conjecture.…”

Section: The Interaction In the Nuclear Medium In The Scalar Sectormentioning

confidence: 83%

Chiral unitary theory: Application to nuclear problems

Oset

Cabrera²,

Chiang³

et al. 2001

Pramana - J Phys

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In this talk we briefly describe some basic elements of chiral perturbation theory, È Ì , and how the implementation of unitarity and other novel elements lead to a better expansion of the Ì -matrix for meson-meson and meson-baryon interactions. Applications are then done to the interaction in nuclear matter in the scalar and vector channels, antikaons in nuclei and Ã atoms, and how the meson properties are changed in a nuclear medium.

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“…The property (i) could not be explained in terms of the π + A → π + π − p[A − 1] phase space [1]. Nor was a detailed model of the A(π + , π + π − ) reaction [4] able to reproduce the low-energy pion yield, although it embodied the kinematical limits of the experimental apparatus.…”

Section: Introductionmentioning

confidence: 99%

“…In early experimental works on π2π in nuclei it was observed that (i) pions preferentially populate the low-energy part of the kinetic energy spectra [1,2,3], and (ii) the π + π − invariant mass M A π + π − peaks increasingly toward the 2m π threshold as the nucleus mass number increases [3]. The property (i) could not be explained in terms of the π + A → π + π − p[A − 1] phase space [1].…”

Section: Introductionmentioning

confidence: 99%

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The ππ interaction in nuclear matter from a study of the πA→ππA′ reactions

et al. 2000

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The pion-production reactions π + A → π + π ± A ′ were studied on 2 H, 12 C, 40 Ca, and 208 P b nuclei at an incident pion energy of T π + =283 MeV. Pions were detected in coincidence using the CHAOS spectrometer. The experimental results are reduced to differential cross sections and compared to both theoretical predictions and the reaction phase space. The composite ratio C A ππ between the π + π ± invariant masses on nuclei and on the nucleon is also presented. Near the 2m π threshold pion pairs couple to (ππ) I=J=0 when produced in the π + → π + π − reaction channel. There is a marked near-threshold enhancement of C A π + π − which is consistent with theoretical predictions addressing the partial restoration of chiral symmetry in nuclear matter. Furthermore, the behaviour of C A π + π − is well described when the restoration of chiral symmetry is combined with standard Pwave renormalization of pions in nuclear matter. On the other hand, nuclear matter only weakly influences C A π + π + , which displays a flat behaviour throughout the energy range regardless of A.

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Measurement of the16O(π+,
N. Grion
¹
,
R. Rui
²
,
Rozon Fm
³

et al.

Cited by 18 publications

References 18 publications

Bound two-pion Cooper pairs in nuclei?

Bound two-pion Cooper pairs in nuclei?

Chiral unitary theory: Application to nuclear problems

The ππ interaction in nuclear matter from a study of the πA→ππA′ reactions

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Measurement of the16O(π+,N. Grion1, R. Rui2, Rozon Fm3 et al.

Cited by 18 publications

References 18 publications

Bound two-pion Cooper pairs in nuclei?

Bound two-pion Cooper pairs in nuclei?

Chiral unitary theory: Application to nuclear problems

The ππ interaction in nuclear matter from a study of the πA→ππA′ reactions

Contact Info

Product

Resources

About

Measurement of the16O(π+,
N. Grion
¹
,
R. Rui
²
,
Rozon Fm
³

et al.