Meson-nucleus scattering lengths and sigma-terms

Gensini, Paolo M.

doi:10.1007/bf02902459

Cited by 21 publications

(8 citation statements)

References 43 publications

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“…first proposed by Drukarev et al [6], and later re-justified by many authors [7], we get, from the requirement n * = ρ * , the very interesting relation σ N = 6m 0 , i.e., the pion-nucleon sigma term σ N is six times the average current quark mass m 0 . If one takes σ N = 45 MeV [8][9][10] and m 0 = (m u0 + m d0 )/2 = (5 + 10)/2 = 7.5 MeV [11], we confirm this result.…”

supporting

confidence: 72%

A new treatment of the in-medium chiral condensates

Peng

Loewe

Lombardo

et al. 2004

Nuclear Physics B - Proceedings Supplements

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A new formalism to calculate the in-medium chiral condensate is presented. At lower densities, this approach leads to a linear expression. If we demand a compatibility with the famous model-independent result, then the pion-nucleon sigma term should be six times the average current mass of light quarks. QCD-like interactions may slow the decreasing behavior of the condensate with increasing densities, compared with the linear extrapolation, if densities are lower than twice the nuclear saturation density. At higher densities, the condensate vanishes inevitably.Comment: contribution to the QCD 2003 conference in Montpellie

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supporting

confidence: 72%

A new treatment of the in-medium chiral condensates

Peng

Loewe

Lombardo

et al. 2004

Nuclear Physics B - Proceedings Supplements

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“…Thus, the method under consideration seems to be preferable compared to utilization of the Fubini-Furlan type sum rules in [-3-5]. This is seen, for example, from the fact that only the different manners, used in [3] and [5] for the estimate of the dispersion integral of the pion-nuclear scattering amplitude imaginary part, led to the essentially different results for a~N (26_+8 MeV and 57 _+6 MeV). Such a discrepancy gives an evidence of the significant uncertainty of the method used in those papers.…”

Section: +T8 2a12mentioning

confidence: 76%

Calculation of the pion-nucleon ? term value from the experimental data on pionic atoms

Efrosinin

Zaikin

1984

Z Physik A

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The pion-nucleon a term value is calculated using pion-nuclear scattering lengths extracted from the data on pionic atoms with A<24 and isospin I=0. The renormalization of the soft-pion ~rN amplitude in nuclear matter is taken into account. The Adependence of the pion-nuclear scattering lengths is studied. Comparison with other results for a term leads to the conclusion that the most probable interval for it is 30-50 MeV. The dispersive part of the S-wave pion-nuclear potential is discussed. The Sum Rule for the Pion-Nuclear AmplitudesOne of the methods for determination of the pionnucleon a term value (%N) is utilization of the sum rule [1] which connects the pion-nuclear iso-symmetric amplitude on the physical threshold T+ (m~) with the same amplitude in the soft-pion limit (so called Weinberg point) T +(0):Here m= and f~ denote the pion mass and the charged pion decay constant (=0,94 m=) respectively, /) -+ are the axial current divergences, IB> is the nuclear ground state, j+ are the pion source functions; the intermediate state In) runs over all states allowed by the selection rules (actually, the authors of [1] limited the set of states In> to the ground or excited nuclear states without pions or with only one pion; for our approach such a restriction is not necessary); E, and P, are energy and momentum of the intermediate system; c.t. stands for the crossed term q2 ~J+, E,-E B ~-E B-E,). Assuming validity of PCAC the commutator in the right-hand side of (1) is equal to zero. Then, if in the sum (1) we separate the coherent rescattering terms, i.e. In>=lB~>, we obtain (see [13)instead of (1) m2 d3q 2 2). T+(m~)=TB+ q (2=)32mAY~(21T,,q] +lTo~ ] (2)Here m A is the mass of the nucleus, q and (Oq are the intermediate pion momentum and energy; T,,q are iso-symmetric and iso-antisymmetric parts of the coherent scattering amplitudeand fl being isotopic indices, and the state IB(-q) ~(q)> being off-shell. As it is shown in [13 the quantitiy T + includes the soft-pion part of the pionnuclear amplitude and also terms corresponding to the incoherent rescattering (In>=lB'=>) and to the pion absorption (In>=lB'>). It was proved [1] that in the nonrelativistic potential model the quantity TB + is nothing but the Born iso-symmetric amplitude of the pion-nuclear scattering. In the framework of that model the expression for the pion-nuclear scattering length has the same structure as (2) (see [1]), namely

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“…The values of σ N and y remain controversial [52][53][54]. In this paper, we take σ N = 45 MeV, which is the value obtained in a recent analysis [54], and consider values of y in the range of 0 − 0.6, which covers the values discussed in [52][53][54].…”

Section: A In-medium Condensatesmentioning

confidence: 99%

QCD sum rules for Σ hyperons in nuclear matter

Jin¹,

Nielsen²

1995

Phys. Rev. C

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Within the finite-density +CD sum-rule approach we investigate the self-energies of Z hyperons propagating in nuclear matter from a correlator of Z interpolating fields evaluated in the nuclear matter ground state. We find that the Lorentz vector self-energy of the Z is similar to the nucleon vector self-energy. The magnitude of Lorentz scalar self-energy of the Z is also close to the corresponding value for nucleon; however, this prediction is sensitive to the strangeness content of the nucleon and to the assumed density dependence of certain four-quark condensate. The scalar and vector self-energies tend to cancel, but not completely. The implications for the couplings of Z to the scalar and vector mesons in nuclear matter and for the Z spin-orbit force in a finite nucleus are discussed.PACS number(s): 24.85. +p, 21.65.+f, 21.80.+a, 11.55.Hx

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Meson-nucleus scattering lengths and sigma-terms

Cited by 21 publications

References 43 publications

A new treatment of the in-medium chiral condensates

A new treatment of the in-medium chiral condensates

Calculation of the pion-nucleon ? term value from the experimental data on pionic atoms

QCD sum rules for Σ hyperons in nuclear matter

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