Universal threshold enhancement

Patkós, A.; Szép, Zsolt; Szépfalusy, P.

doi:10.1103/physrevd.68.047701

Cited by 17 publications

(56 citation statements)

References 10 publications

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“…Nevertheless, threshold enhancement is indeed observed in nuclear matter experiments, both in πA → ππA ′ [23,24] and in γA → ππA ′ [25] reactions. Although the size of the effect is still under debate, a clear signal is seen in the scalar channel for increasing nuclear density as compared with the vector channel and this is in fair agreement with most theoretical analyses at finite nuclear density [26,27,28,29,30,31]. In contrast, finite temperature analyses show that this state remains broad even near the chiral phase transition despite the proximity of the pole to the two-pion threshold [12,30,32], which in practice does not produce any sizable enhancement in the scattering amplitude or cross section.…”

Section: Introductionsupporting

confidence: 84%

“…Although the size of the effect is still under debate, a clear signal is seen in the scalar channel for increasing nuclear density as compared with the vector channel and this is in fair agreement with most theoretical analyses at finite nuclear density [26,27,28,29,30,31]. In contrast, finite temperature analyses show that this state remains broad even near the chiral phase transition despite the proximity of the pole to the two-pion threshold [12,30,32], which in practice does not produce any sizable enhancement in the scattering amplitude or cross section. A striking possibility to be explored is that by increasing further the medium strength, the σ could become a ππ bound state, as suggested earlier in [33] and confirmed recently in [12,30,32].…”

Section: Introductionsupporting

confidence: 84%

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Chiral symmetry and light resonances in hot and dense matter

2008

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Abstract. We present a study of the ππ scattering amplitude in the σ and ρ channels at finite temperature and nuclear density within a chiral unitary framework. Meson resonances are dynamically generated in our approach, which allows us to analyze the behavior of their associated scattering poles when the system is driven towards chiral symmetry restoration. Medium effects are incorporated in three ways: (a) by thermal corrections of the unitarized scattering amplitudes, (b) by finite nuclear density effects associated to a renormalization of the pion decay constant, and complementarily (c) by extending our calculation of the scalar-isoscalar channel to account for finite nuclear density and temperature effects in a microscopic many-body implementation of pion dynamics. Our results are discussed in connection with several phenomenological aspects relevant for nuclear matter and Heavy-Ion Collision experiments, such as ρ mass scaling vs broadening from dilepton spectra and chiral restoration signals in the σ channel. We also elaborate on the molecular nature of ππ resonances. PACS

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Section: Introductionsupporting

confidence: 84%

Section: Introductionsupporting

confidence: 84%

Chiral symmetry and light resonances in hot and dense matter

2008

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“…The authors in [2,6] showed that the width grows with temperature, while the mass decreases slightly. This paper is organized as follows.…”

Section: Introductionmentioning

confidence: 99%

Momentum dependence of the spectral functions in theO(4)linear sigma model at finite temperature

2003

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The spatial momentum dependence of the spectral function for π and σ at finite temperature is studied by employing the O(4) linear sigma model and adopting a resummation technique called optimized perturbation theory (OPT). The poles of the propagators are also searched for.We analyze the spatial momentum dependence of the imaginary part of the self-energy and find its temperature-dependent part to vanish in the large momentum limit. This is because the energy of the particles in the heat bath which participate in the process becomes large and therefore the Bose distribution function vanishes.We then calculate the spectral functions and search for the poles of the propagators. First, we discuss the temperature dependence for zero spatial momentum. We reproduce the spectral functions in both π and σ channels in the previous work and find that the pole, which is responsible for the threshold enhancement of the spectral functions in both π and σ channels, is different from the one for the peak at zero temperature. Secondly, we discuss the spatial-momentum dependence.When the temperature is low the spatial momentum dependence is also small. As the temperature becomes higher the spatial momentum dependence becomes also large. When the spatial momentum is smaller than the temperature, the spectral functions do not deviate much from those at zero spatial momentum. Once the spatial momentum becomes comparable with the temperature, the deviation becomes considerable. As the momentum becomes much larger than the temperature, thermal effects effectively decrease.

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“…The line of analysis presented here has been applied also to the model with explicit O(4)-breaking external field [ 11,16], with parameters chosen the closest possible to the measured characteristics of the σ − π meson system. The behaviour found in this analysis proved generic also for the system with finite baryonic charge density.…”

Section: Resultsmentioning

confidence: 99%

Finite Temperature Spectral Function of the σ Meson from Large N Expansion

Patkós

Szép

Szépfalusy

2003

Acta Physica Hungarica A) Heavy Ion Physics

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Abstract. The spectral function of the scalar-isoscalar channel of the O(N ) symmetric linear σ model is studied in the broken symmetry phase. The investigation is based on the leading order evaluation of the self-energy in the limit of large number of Goldstone bosons. We describe its temperature dependent variation in the whole low temperature phase. This variation closely reflects the trajectory of the scalar-isoscalar quasiparticle pole. In the model with no explicit chiral symmetry breaking we have studied near the critical point also the corresponding dynamical exponent.

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Universal threshold enhancement

Cited by 17 publications

References 10 publications

Chiral symmetry and light resonances in hot and dense matter

Chiral symmetry and light resonances in hot and dense matter

Momentum dependence of the spectral functions in theO(4)linear sigma model at finite temperature

Finite Temperature Spectral Function of the σ Meson from Large N Expansion

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