Chiral condensate at finite density using the chiral Ward identity

Earlier work suggested that the in-medium πN threshold isovector amplitude b 1 (ρ) gets renormalized in pionic atoms by ∼ 30% away from its ρ = 0 freespace value, relating such renormalization to the leading low-density decrease of the in-medium quark condensate and the pion decay constant f π in terms of the pion-nucleon σ term σ πN . Accepting the validity of this approach, we extracted σ πN from a large-scale fit of pionic-atom level shift and width data across the periodic table. Our fitted value σ πN = 57 ± 7 MeV is robust with respect to variation of πN interaction terms other than the isovector s-wave term with which σ πN was associated. Higher order corrections to the leading order in density involve some cancellations, suggesting thereby only a few percent overall systematic uncertainty. The value of σ πN derived here agrees with values obtained in several recent studies based on near-threshold πN phenomenology, but sharply disagrees with values obtained in recent direct lattice QCD calculations.

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“…and also by adding corrections of order ρ 4/3 [58,59] which at ρ eff are negligible. The pion mass dependence in Eq.…”

Section: Discussion and Summarymentioning

confidence: 99%

The pion-nucleon σ term from pionic atoms

Friedman

Gal

2019

Physics Letters B

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“…Other works along these lines are Refs. [8,9], which work out the next-to-leading order (NLO) in-medium corrections to some pion properties by applying the many-body formalism derived in Ref. [4] and following the perturbative power counting of Ref.…”

Section: Introductionmentioning

confidence: 99%

An in-medium chiral power-counting scheme for nuclear matter and some applications

Oller¹

2019

J. Phys. G: Nucl. Part. Phys.

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We review on a chiral power counting scheme for in-medium chiral perturbation theory with nucleons and pions as explicit degrees of freedom coupled to external sources. It allows for a systematic expansion taking into account both local as well as pion-mediated inter-nucleon interactions. One can identify from this power counting classes of non-perturbative diagrams that require resummation. A non-perturbative method based on Unitary Chiral Perturbation Theory (UChPT) was also developed for performing those needed resummations. This power counting and non-perturbative techniques were firstly applied to calculate the pion self-energy, the pion-decay constants and the quark condensate in nuclear matter up-to-and-including next-to-leading order (NLO) contributions. The cancellation of the contributions at NLO to the pion self-energy and decay constants from in-medium nucleon-nucleon (N N ) interactions was derived. Some NLO contributions from the in-medium N N interactions survive for the quark condensate due to the quark-mass dependence of the pion mass. Next, we discuss the calculation of the energy density in the nuclear medium by employing the derived in-medium N N scattering amplitudes. For symmetric and neutron matter it reproduces in good agreement, and without fine tuning, calculations from realistic N N potentials with a model for the three-nucleon interaction. These results are applied to derive the equation of state (EOS) for neutron stars and obtain an upper limit for a neutron mass slightly above 2 solar masses, in agreement with recent observations. Furthermore, our results also fulfill other constraints from the detection of the gravitational waves in the event GW170817 by the LIGO and Virgo Collaborations, like the upper bound on the maximal mass of a neutron star and the allowed interval of values for the radius of a 1.4-solar-mass neutron star. The knowledge of the neutron-matter EOS is also employed to give an upper bound of the gravitational constant within the strong gravitational field of a 2 solar-mass neutron star.

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“…For further detailed study of the medium effects on K + , we need to develop in-medium chiral perturbation theory for the K meson similar for the pion developed, for example, in Refs. [33,34].…”

Section: Wavefunction Renormalizationmentioning

confidence: 99%

K +–nucleus elastic scattering revisited from the perspective of partial restoration of chiral symmetry

Aoki

2017

Progress of Theoretical and Experimental Physics

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The K + meson properties in the nuclear medium are investigated by considering the wavefunction renormalization as a first step to reveal the in-medium properties of the K + meson in the context of partial restoration of chiral symmetry. The K + N elastic scattering amplitude is constructed using chiral perturbation theory up to the next-to-leading order. Using the constructed amplitude, we calculate the wavefunction renormalization in the Thomas-Fermi approximation. We obtained a good description of the K + N elastic scattering amplitude. The obtained wavefunction renormalization factor suggests the 2 to 6% enhancement of the K + N interaction at the saturation density. We conclude that the wavefunction renormalization could be one of the important medium effects for the K + meson.

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Chiral condensate at finite density using the chiral Ward identity

Cited by 35 publications

References 44 publications

The pion-nucleon σ term from pionic atoms

The pion-nucleon σ term from pionic atoms

An in-medium chiral power-counting scheme for nuclear matter and some applications

K +–nucleus elastic scattering revisited from the perspective of partial restoration of chiral symmetry

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