Astrophysical Constraints on the Axion Mass and the Number of Quark Flavors

AbstractDifferent aspects of the phase diagram of strongly interacting matter described by quantum chromodynamics (QCD), which have emerged from the recent studies using lattice gauge theory techniques, are discussed. A special emphasis is given on understanding the role of the anomalous axial U(1) symmetry in determining the order of the finite temperature chiral phase transition in QCD with two massless quark flavors and tracing its origin to the topological properties of the QCD vacuum.

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A composite Higgs with a heavy composite axion

Journal of High Energy Physics ◽

10.1007/jhep12(2020)094 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

Tony Gherghetta ◽

Minh D. Nguyen

Keyword(s):

Cp Violation ◽

Gauge Group ◽

Scalar Fields ◽

Higgs Model ◽

Global Symmetry ◽

Color Group ◽

High Scale ◽

Axion Mass ◽

Composite Higgs ◽

The Standard Model

Abstract We consider the strong dynamics associated with a composite Higgs model that simultaneously produces dynamical axions and solves the strong CP problem. The strong dynamics arises from a new Sp or SU(4) hypercolor gauge group containing QCD colored hyperfermions that confines at a high scale. The hypercolor global symmetry is weakly gauged by the Standard Model electroweak gauge group and an enlarged color group, SU(N + 3) × SU(N)′. When hyperfermion condensates form, they not only lead to an SU(5)/SO(5) composite Higgs model but also spontaneously break the enlarged color group to SU(3)c× SU(N)D. At lower energies, the SU(N)D group confines, producing two dynamical axions that eliminates all CP violation. Furthermore, small instantons from the SU(N)′ group can enhance the axion mass, giving rise to TeV scale axion masses that can be detected at collider experiments. Our model provides a way to unify the composite Higgs with dynamical axions, without introducing new elementary scalar fields, while also extending the range of axion masses that addresses the strong CP problem.

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Accidental SO(10) axion from gauged flavour

Journal of High Energy Physics ◽

10.1007/jhep11(2020)074 ◽

2020 ◽

Vol 2020 (11) ◽

Author(s):

Luca Di Luzio

Keyword(s):

Mass Window ◽

High Quality ◽

High Scale ◽

Quality Problem ◽

Axion Mass ◽

Grand Unified Theories ◽

Unified Theories ◽

Canonical Dimension ◽

General Perspective ◽

Effective Operators

Abstract An accidental U(1) Peccei-Quinn (PQ) symmetry automatically arises in a class of SO(10) unified theories upon gauging the SU(3)f flavour group. The PQ symmetry is protected by the ℤ4 × ℤ3 center of SO(10) × SU(3)f up to effective operators of canonical dimension six. However, high-scale contributions to the axion potential posing a PQ quality problem arise only at d = 9. In the pre-inflationary PQ breaking scenario the axion mass window is predicted to be ma ∈ [7 × 10−8, 10−3] eV, where the lower end is bounded by the seesaw scale and the upper end by iso-curvature fluctuations. A high-quality axion, that is immune to the PQ quality problem, is obtained for ma ≳ 2 0.02 eV. We finally offer a general perspective on the PQ quality problem in grand unified theories.

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Possible Origin of Lepton and Quark Flavors

Progress of Theoretical Physics ◽

10.1143/ptp.60.851 ◽

1978 ◽

Vol 60 (3) ◽

pp. 851-856 ◽

Cited By ~ 3

Author(s):

H. Terazawa

Keyword(s):

Quark Flavors

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$ {\Lambda_{{\overline {\text{MS}} }}} $ from the static potential for QCD with n f = 2 dynamical quark flavors

Journal of High Energy Physics ◽

10.1007/jhep01(2012)025 ◽

2012 ◽

Vol 2012 (1) ◽

Cited By ~ 27

Author(s):

Karl Jansen ◽

Felix Karbstein ◽

Attila Nagy ◽

Marc Wagner

Keyword(s):

Static Potential ◽

Quark Flavors ◽

Dynamical Quark

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MEASUREMENT OF POLARIZED QUARK DISTRIBUTIONS AT HERMES

International Journal of Modern Physics A ◽

10.1142/s0217751x03014502 ◽

2003 ◽

Vol 18 (08) ◽

pp. 1185-1192

Author(s):

◽

STEFAN BERNREUTHER

Keyword(s):

Cross Section ◽

Kinematic Range ◽

Spin Asymmetries ◽

Double Spin ◽

Hermes Experiment ◽

Down Quark ◽

Up Quark ◽

Rich Detector ◽

The Individual ◽

Quark Flavors

The HERMES experiment has measured double spin asymmetries in the cross section for deep–inelastic scattering of longitudinally polarized positrons on longitudinally polarized 3 He (1995), 1 H (1996/97), and 2 D (1998) targets. A kinematic range of 0.023 < x < 0.6, and 1 GeV 2 < Q2 < 15 GeV 2 has been covered. From these asymmetries, based on inclusive and semi–inclusive measurements, polarized quark distributions are extracted as a function of x for up [Formula: see text] and down [Formula: see text] flavors as well as for valence and sea quarks. In the measured range, the up quark polarization is positive while the down quark polarization is negative. The sea quark polarization is compatible with zero. In this analysis all sea quark polarizations have been assumed to be flavor symmetric. Presently HERMES is analyzing a high statistics 2 D data sample taken in 1999-2000. For these data it is possible to identify pions and kaons with a RICH detector which was installed in 1998. This will enable an extraction of the individual sea quark flavors [Formula: see text], [Formula: see text], and [Formula: see text] without any symmetry assumptions.

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QUARK ORBITAL ANGULAR MOMENTUM IN THE BARYON

International Journal of Modern Physics A ◽

10.1142/s0217751x01005018 ◽

2001 ◽

Vol 16 (22) ◽

pp. 3673-3697 ◽

Cited By ~ 6

Author(s):

XIAOTONG SONG

Keyword(s):

Angular Momentum ◽

Orbital Angular Momentum ◽

Orbital Motion ◽

Magnetic Moments ◽

Sum Rule ◽

Quark Spin ◽

Quark Flavor ◽

Quark Orbital Angular Momentum ◽

Quark Flavors ◽

Partition Factor

Analytical and numerical results, for the orbital and spin content carried by different quark flavors in the baryons, are given in the chiral quark model with symmetry breaking. The reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as a function of the partition factor κ and the chiral splitting probability a is shown. The cancellation between the spin and orbital contributions in the spin sum rule and in the baryon magnetic moments is discussed.

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