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Gómez Nicola, Ángel and Torres Andrés, R. (2014) Electromagnetic effects in the pion dispersion relation at finite temperature. Physical review D, 89 (11). ISSN 15507998

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Official URL: http://dx.doi.org/10.1103/PhysRevD.89.116009
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http://journals.aps.org/  Publisher 
Abstract
We investigate the chargedneutral difference in the pion selfenergy at finite temperature T. Within chiral perturbation theory (ChPT) we extend a previous analysis performed in the chiral and soft pion limits. Our analysis with physical pion masses leads to additional nonnegligible contributions for temperatures typical of a meson gas, including a momentumdependent function for the selfenergy. In addition, a nonzero imaginary part arises to leading order, which we define consistently in the Coulomb gauge and comes from an infrared enhanced contribution due to thermal bath photons. For distributions typical of a heavyion meson gas, the charged and neutral pion masses and their difference depend on temperature through slowly increasing functions. Chiral symmetry restoration turns out to be ultimately responsible for keeping the chargedneutral mass difference smooth and compatible with the observed charged and neutral pion spectra. We study also phenomenological effects related to the thermal electromagnetic damping, which gives rise to corrections for transport coefficients and distinguishes between neutral and charged mean free times. An important part of the analysis is the connection with chiral symmetry restoration through the relation of the pion mass difference with the vectoraxial spectral function difference, which holds at T ¼ 0 due to a sum rule in the chiral and soft pion limits. We analyze the modifications of that sum rule including nonzero pion masses and temperature, up to OðT2Þ ∼ OðM2 πÞ. Both effects produce terms making the pion mass difference grow against chiralrestoring decreasing contributions. Finally, we analyze the corrections to the previous ChPT and sum rule results within the resonance saturation framework at finite temperature, including explicitly ρ and a1 exchanges. Our results show that the ChPT result is robust at low and intermediate temperatures, the leading resonance corrections within this framework being OðT2M2 π=M2 RÞ with MR the involved resonance masses.
Item Type:  Article 

Additional Information:  © 2014 American Physical Society. This work was partially supported by the Spanish Research Contract No. FPA201127853C0202 and the FPI programme (BES2009013672). We acknowledge the support of the EU FP7 HadronPhysics3 project. 
Uncontrolled Keywords:  Chiral perturbationtheory; Axialvector mesons; Mass difference; Virtual photons; strange quark; Light quark; Fieldtheory; Damping rate; Sumrules; Oneloop. 
Subjects:  Sciences > Physics > PhysicsMathematical models Sciences > Physics > Mathematical physics 
ID Code:  29601 
Deposited On:  16 Apr 2015 08:12 
Last Modified:  10 Dec 2018 15:09 
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