On the order of the QCD chiral phase transition for different numbers of quark flavours

Abstract The nature of the QCD chiral phase transition in the limit of vanishing quark masses has remained elusive for a long time, since it cannot be simulated directly on the lattice and is strongly cutoff-dependent. We report on a comprehensive ongoing study using unimproved staggered fermions wi...

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Autores principales:	Francesca Cuteri, Owe Philipsen, Alessandro Sciarra
Formato:	article
Lenguaje:	EN
Publicado:	SpringerOpen 2021
Materias:	Lattice QCD Lattice Quantum Field Theory Phase Diagram of QCD Nuclear and particle physics. Atomic energy. Radioactivity QC770-798
Acceso en línea:	https://doaj.org/article/2335cb7d481d4dea80c1976935241c76
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spelling	oai:doaj.org-article:2335cb7d481d4dea80c1976935241c762021-11-21T12:41:44ZOn the order of the QCD chiral phase transition for different numbers of quark flavours10.1007/JHEP11(2021)1411029-8479https://doaj.org/article/2335cb7d481d4dea80c1976935241c762021-11-01T00:00:00Zhttps://doi.org/10.1007/JHEP11(2021)141https://doaj.org/toc/1029-8479Abstract The nature of the QCD chiral phase transition in the limit of vanishing quark masses has remained elusive for a long time, since it cannot be simulated directly on the lattice and is strongly cutoff-dependent. We report on a comprehensive ongoing study using unimproved staggered fermions with N f ∈ [2, 8] mass-degenerate flavours on N τ ∈ {4, 6, 8} lattices, in which we locate the chiral critical surface separating regions with first-order transitions from crossover regions in the bare parameter space of the lattice theory. Employing the fact that it terminates in a tricritical line, this surface can be extrapolated to the chiral limit using tricritical scaling with known exponents. Knowing the order of the transitions in the lattice parameter space, conclusions for approaching the continuum chiral limit in the proper order can be drawn. While a narrow first-order region cannot be ruled out, we find initial evidence consistent with a second-order chiral transition in all massless theories with N f ≤ 6, and possibly up to the onset of the conformal window at 9 ≲ N f ∗ $$ {N}_{\mathrm{f}}^{\ast } $$ ≲ 12. A reanalysis of already published O $$ \mathcal{O} $$ (a)-improved N f = 3 Wilson data on N τ ∈ [4, 12] is also consistent with tricritical scaling, and the associated change from first to second-order on the way to the continuum chiral limit. We discuss a modified Columbia plot and a phase diagram for many-flavour QCD that reflect these possible features.Francesca CuteriOwe PhilipsenAlessandro SciarraSpringerOpenarticleLattice QCDLattice Quantum Field TheoryPhase Diagram of QCDNuclear and particle physics. Atomic energy. RadioactivityQC770-798ENJournal of High Energy Physics, Vol 2021, Iss 11, Pp 1-32 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Lattice QCD Lattice Quantum Field Theory Phase Diagram of QCD Nuclear and particle physics. Atomic energy. Radioactivity QC770-798
spellingShingle	Lattice QCD Lattice Quantum Field Theory Phase Diagram of QCD Nuclear and particle physics. Atomic energy. Radioactivity QC770-798 Francesca Cuteri Owe Philipsen Alessandro Sciarra On the order of the QCD chiral phase transition for different numbers of quark flavours
description	Abstract The nature of the QCD chiral phase transition in the limit of vanishing quark masses has remained elusive for a long time, since it cannot be simulated directly on the lattice and is strongly cutoff-dependent. We report on a comprehensive ongoing study using unimproved staggered fermions with N f ∈ [2, 8] mass-degenerate flavours on N τ ∈ {4, 6, 8} lattices, in which we locate the chiral critical surface separating regions with first-order transitions from crossover regions in the bare parameter space of the lattice theory. Employing the fact that it terminates in a tricritical line, this surface can be extrapolated to the chiral limit using tricritical scaling with known exponents. Knowing the order of the transitions in the lattice parameter space, conclusions for approaching the continuum chiral limit in the proper order can be drawn. While a narrow first-order region cannot be ruled out, we find initial evidence consistent with a second-order chiral transition in all massless theories with N f ≤ 6, and possibly up to the onset of the conformal window at 9 ≲ N f ∗ $$ {N}_{\mathrm{f}}^{\ast } $$ ≲ 12. A reanalysis of already published O $$ \mathcal{O} $$ (a)-improved N f = 3 Wilson data on N τ ∈ [4, 12] is also consistent with tricritical scaling, and the associated change from first to second-order on the way to the continuum chiral limit. We discuss a modified Columbia plot and a phase diagram for many-flavour QCD that reflect these possible features.
format	article
author	Francesca Cuteri Owe Philipsen Alessandro Sciarra
author_facet	Francesca Cuteri Owe Philipsen Alessandro Sciarra
author_sort	Francesca Cuteri
title	On the order of the QCD chiral phase transition for different numbers of quark flavours
title_short	On the order of the QCD chiral phase transition for different numbers of quark flavours
title_full	On the order of the QCD chiral phase transition for different numbers of quark flavours
title_fullStr	On the order of the QCD chiral phase transition for different numbers of quark flavours
title_full_unstemmed	On the order of the QCD chiral phase transition for different numbers of quark flavours
title_sort	on the order of the qcd chiral phase transition for different numbers of quark flavours
publisher	SpringerOpen
publishDate	2021
url	https://doaj.org/article/2335cb7d481d4dea80c1976935241c76
work_keys_str_mv	AT francescacuteri ontheorderoftheqcdchiralphasetransitionfordifferentnumbersofquarkflavours AT owephilipsen ontheorderoftheqcdchiralphasetransitionfordifferentnumbersofquarkflavours AT alessandrosciarra ontheorderoftheqcdchiralphasetransitionfordifferentnumbersofquarkflavours
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On the order of the QCD chiral phase transition for different numbers of quark flavours

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