Relativistic approach to pionic atoms

Birbrair, B.L.; Gridnev, A.

doi:10.1016/0375-9474(91)90255-5

Cited by 19 publications

(16 citation statements)

References 3 publications

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“…The proposed mechanism was implemented in fits to a large set of pionic atom data [14] and indeed found to remove most of the 'anomaly' in the s-wave term. A relativistic impulse approximation (RIA) term that was proposed earlier following Birbrair [15][16][17][18][19] was also shown [18,14] to remove part of the anomaly. Combining the two effects [14] removed the anomaly completely.…”

Section: Introductionmentioning

confidence: 91%

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Density dependence of the s-wave repulsion in pionic atoms

Friedman

2002

Nuclear Physics A

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Several mechanisms of density dependence of the s-wave repulsion in pionic atoms, beyond the conventional model, are tested by parameter fits to a large (106 points) set of data from $^{16}$O to $^{238}$U, including `deeply bound' states in $^{205}$Pb. Special attention is paid to the proper choice of nuclear density distributions. A density-dependent isovector scattering amplitude suggested recently by Weise to result from a density dependence of the pion decay constant is introduced and found to account for most of the so-called anomalous repulsion. The presence of such an effect might indicate partial chiral symmetry restoration in dense matter. The anomalous repulsion is fully accounted for when an additional relativistic impulse approximation term is included in the potential.Comment: 18 pages, 5 figures, version 2 (extended

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Section: Introductionmentioning

confidence: 91%

“…The coefficient d 0 = −0.190m −3 π originates in the spin-dependent interaction [2]. For the effective nucleon mass the following parameterization was used [17] M(ρ)…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Density dependence of the s-wave repulsion in pionic atoms

Friedman

2002

Nuclear Physics A

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“…This scaling can be identified [17] as the "intrinsic" density dependence required by matching to QCD. The other medium modification Friedman needs goes back to the relativistic impulse approximation used by Birbrair and collaborators [63] which gives small components of the Dirac wave functions for the nucleon enhanced by the factor F = m N /M (r) (29) where M (r) = m N + 1 2 [S(r) − V (r)] with S(r) and V (r) the vector mean fields. In fact, if we write…”

Section: In-medium Pion Decay Constantmentioning

confidence: 99%

Double decimation and sliding vacua in the nuclear many-body system

Brown

Rho

2004

Physics Reports

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We propose that effective field theories for nuclei and nuclear matter comprise of "double decimation": (1) the chiral symmetry decimation (CSD) and (2) Fermi liquid decimation (FLD). The Brown-Rho scaling identified as the parametric dependence intrinsic in the "vector manifestation" of hidden local symmetry theory of Harada and Yamawaki results from the first decimation, i.e., CSD. In a recent work we showed that in matter under conditions of high density or high temperature, dynamically generated hadron masses scaled with a common scale. Namely for low densities and temperatures the masses scaled as m ⋆ /m ≃ [ qq ⋆ / qq ] 1/2 whereas at higher densities and temperatures as [ qq ⋆ / qq ]. In the present work we summarize new empirical evidence for Brown-Rho (BR) scaling and discuss in a general way its impact on the nuclear many-body problem. While the double decimation should be carried out, it has been a prevalent practice in nuclear physics community to proceed with the second decimation, assuming density independent masses, without implementing the first, chiral symmetry decimation. We show why most nuclear phenomena can be reproduced by theories using either densityindependent, or density-dependent masses, a grand conspiracy of nature that is an aspect that could be tied to the Cheshire-Cat phenomenon in hadron physics. We go through some of the history of the chiral symmetry decimation (CSD) which involves BR scaling, in order to show that historically one had to look at very specific phenomena involving transition matrix elements to see that it is necessary. We identify what is left out in the Fermi liquid decimation (FLD) that does not incorporate the CSD. Experiments such as the dilepton production in relativistic heavy ion reactions, which are specifically designed to observe effects of dropping masses, could exhibit large effects from the reduced masses. However they are compounded with effects that are not directly tied to chiral symmetry. We discuss a recent STAR/RHIC observation where BR scaling can be singled out in a pristine environment.1 The holes are on-shell in the Brueckner-Bethe theory. 2 We are assuming U (2) flavor symmetry in the two-flavor case. 3 Implementing temperature effects is straightforward and hence will be ignored in what follows in this section. 11 In HLS/VM with the explicit vector degrees of freedom, the scaling parameters are the gauge coupling g * , the vector-meson mass m * V , the pion decay constant F * π and the coefficient a. However in medium a * ≈ 1, g * ≈ g, so mV * goes as F * π through HLS/VM relations. We are left with only one scaling factor as in the case where the vectors are integrated out. 12 The deviation from vector dominance in the photon coupling to the baryons has been known since some time. In fact, the chiral bag model [27, 68] provided a natural mechanism for such a deviation.

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“…The occupation numbers of protons (neutrons) are denoted by p (n ) and (cr~I)"= l"or (I"+1) -for angular momentum j = l 6 2. Almost the same expression for the term in question was obtained recently by Birbrair and Gridnev [27] in the framework of relativistic meanfield approach but it differs from that published earlier by Friedman and Gal [4]. The last one is probably in error.…”

Section: The Optical Modelmentioning

confidence: 56%

“…In order to avoid a possible confusion, we recall the reader that Birbrair and Gridnev obtained another spin term [pg(r) in their notation], which is of "relativistic" origin [27]. The term pI, (r) does not vanish for spin satmismatch b, = 360 MeV/c in the pion annihilation~AN ; NN, the scattering matrix t'~~(E) is expected to vanish for internucleon separations larger than r = 0.3 fm.…”

Section: The Optical Modelmentioning

confidence: 99%

Influence of nuclear structure on the characteristics of light pionic atoms

Ciepl

Mach

1994

Phys. Rev. C

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An extended version of the standard pion-nucleus optical potential is presented using the momentum-space formulation of the multiple scattering theory. This potential is used for studying the in6uence of nonlocal effects and nuclear structure on the characteristics of light pionic atoms. A method is suggested to treat the long-range two-nucleon correlations involved in the second-order optical potential. Particularly, the spin-orbital Fermi motion correction to the 6rst-order optical potential, the center-of-mass correlations, and the spin-isospin corrections to the second-order optical potential are discussed in some detail. The results are presented in comparison with the experimental data for the 1s and 2p levels of light pionic atoms up to Ca. PACS number(s): 25.80. -e, 36.10.Gv

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Relativistic approach to pionic atoms

Cited by 19 publications

References 3 publications

Density dependence of the s-wave repulsion in pionic atoms

Density dependence of the s-wave repulsion in pionic atoms

Double decimation and sliding vacua in the nuclear many-body system

Influence of nuclear structure on the characteristics of light pionic atoms

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