The role of strangeness in chiral and $$U(1)_A$$ U ( 1 ) A restoration

A. Gómez Nicola (Departamento de Física Teórica and IPARCOS, Universidad Complutense, Madrid, 28040, Spain) ; J. Ruiz de Elvira (Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, Bern, 3012, Switzerland) ; A. Vioque-Rodríguez (Departamento de Física Teórica and IPARCOS, Universidad Complutense, Madrid, 28040, Spain) ; D. Álvarez-Herrero (Departamento de Física Teórica and IPARCOS, Universidad Complutense, Madrid, 28040, Spain)

We use recently derived Ward identities and lattice data for the light- and strange-quark condensates to reconstruct the scalar and pseudoscalar susceptibilities ( $$\chi _S^\kappa $$ χ S κ , $$\chi _P^K$$ χ P K ) in the isospin 1/2 channel. We show that $$\chi _S^\kappa $$ χ S κ develops a maximum above the QCD chiral transition, after which it degenerates with $$\chi _P^K$$ χ P K . We also obtain $$\chi _S^\kappa $$ χ S κ within Unitarized Chiral Perturbation Theory (UChPT) at finite temperature, when it is saturated with the $$K_0^*(700)$$ K 0 ( 700 ) (or $$\kappa $$ κ ) meson, the dominant lowest-energy state in the isospin 1/2 scalar channel of $$\pi K$$ π K scattering. Such UChPT result reproduces the expected peak structure, revealing the importance of thermal interactions, and makes it possible to examine the $$\chi _S^\kappa $$ χ S κ dependence on the light- and strange-quark masses. A consistent picture emerges controlled by the $$m_l/m_s$$ m l / m s ratio that allows one studying $$K-\kappa $$ K - κ degeneration in the chiral, two-flavor and SU(3) limits. These results provide an alternative sign for $$O(4)\times U(1)_A$$ O ( 4 ) × U ( 1 ) A restoration that can be explored in lattice simulations and highlight the role of strangeness, which regulated by the strange-quark condensate helps to reconcile the current tension among lattice results regarding $$U(1)_A$$ U ( 1 ) A restoration.

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      "surname": "Ruiz de Elvira", 
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      "title": "The role of strangeness in chiral and  $$U(1)_A$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>A</mi> </msub> </mrow> </math>   restoration"
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      "source": "Springer", 
      "value": "We use recently derived Ward identities and lattice data for the light- and strange-quark condensates to reconstruct the scalar and pseudoscalar susceptibilities ( $$\\chi _S^\\kappa $$  <math> <msubsup> <mi>\u03c7</mi> <mi>S</mi> <mi>\u03ba</mi> </msubsup> </math>  ,  $$\\chi _P^K$$  <math> <msubsup> <mi>\u03c7</mi> <mi>P</mi> <mi>K</mi> </msubsup> </math>  ) in the isospin 1/2 channel. We show that  $$\\chi _S^\\kappa $$  <math> <msubsup> <mi>\u03c7</mi> <mi>S</mi> <mi>\u03ba</mi> </msubsup> </math>   develops a maximum above the QCD chiral transition, after which it degenerates with  $$\\chi _P^K$$  <math> <msubsup> <mi>\u03c7</mi> <mi>P</mi> <mi>K</mi> </msubsup> </math>  . We also obtain  $$\\chi _S^\\kappa $$  <math> <msubsup> <mi>\u03c7</mi> <mi>S</mi> <mi>\u03ba</mi> </msubsup> </math>   within Unitarized Chiral Perturbation Theory (UChPT) at finite temperature, when it is saturated with the  $$K_0^*(700)$$  <math> <mrow> <msubsup> <mi>K</mi> <mn>0</mn> <mo>\u2217</mo> </msubsup> <mrow> <mo>(</mo> <mn>700</mn> <mo>)</mo> </mrow> </mrow> </math>   (or  $$\\kappa $$  <math> <mi>\u03ba</mi> </math>  ) meson, the dominant lowest-energy state in the isospin 1/2 scalar channel of  $$\\pi K$$  <math> <mrow> <mi>\u03c0</mi> <mi>K</mi> </mrow> </math>   scattering. Such UChPT result reproduces the expected peak structure, revealing the importance of thermal interactions, and makes it possible to examine the  $$\\chi _S^\\kappa $$  <math> <msubsup> <mi>\u03c7</mi> <mi>S</mi> <mi>\u03ba</mi> </msubsup> </math>   dependence on the light- and strange-quark masses. A consistent picture emerges controlled by the  $$m_l/m_s$$  <math> <mrow> <msub> <mi>m</mi> <mi>l</mi> </msub> <mo>/</mo> <msub> <mi>m</mi> <mi>s</mi> </msub> </mrow> </math>   ratio that allows one studying  $$K-\\kappa $$  <math> <mrow> <mi>K</mi> <mo>-</mo> <mi>\u03ba</mi> </mrow> </math>   degeneration in the chiral, two-flavor and SU(3) limits. These results provide an alternative sign for  $$O(4)\\times U(1)_A$$  <math> <mrow> <mi>O</mi> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>\u00d7</mo> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>A</mi> </msub> </mrow> </math>   restoration that can be explored in lattice simulations and highlight the role of strangeness, which regulated by the strange-quark condensate helps to reconcile the current tension among lattice results regarding  $$U(1)_A$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>A</mi> </msub> </mrow> </math>   restoration."
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Published on:
21 July 2021
Publisher:
Springer
Published in:
European Physical Journal C , Volume 81 (2021)
Issue 7
Pages 1-9
DOI:
https://doi.org/10.1140/epjc/s10052-021-09458-1
Copyrights:
The Author(s)
Licence:
CC-BY-4.0

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