Quark masses, isospin breaking and the vector piece of π → eνγ

In the standard model the isospin symmetry is broken by electro magnetic interactions as well as the difference in the quark masses. Given a systematic scheme that allows to disentangle these two effects it is possible to get direct access to properties of QCD from low and medium energy hadronic reactions. Recently interest in isospin breaking reactions has revived due to the measurement of a forward–backward asymmetry in pn→dπ0 as well as the total cross section for dd→απ0—both quantities vanish in an isospin symmetric world. The current status of the theoretical analysis for these reactions is disucssed. In addition, I will briefly discuss how the isospin violating a0(980)-f0(980) transition amplitude can be studied in dd and pn induced production reactions—a quantity that is believed to reveal important information on the nature of these lightest scalar mesons.

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Leading isospin-breaking corrections to meson masses on the lattice

EPJ Web of Conferences ◽

10.1051/epjconf/201817506002 ◽

2018 ◽

Vol 175 ◽

pp. 06002 ◽

Cited By ~ 3

Author(s):

Davide Giusti ◽

Vittorio Lubicz ◽

Guido Martinelli ◽

Francesco Sanfilippo ◽

Silvano Simula ◽

...

Keyword(s):

Fine Structure ◽

Quark Mass ◽

Light Quark ◽

Structure Constant ◽

Mass Splitting ◽

Fine Structure Constant ◽

Isospin Breaking ◽

Decay Constants ◽

Quark Masses ◽

Small Parameters

We present a study of the isospin-breaking (IB) corrections to pseudoscalar (PS) meson masses using the gauge configurations produced by the ETM Collaboration with Nf = 2+1+1 dynamical quarks at three lattice spacings varying from 0.089 to 0.062 fm. Our method is based on a combined expansion of the path integral in powers of the small parameters [see formula in PDF] and αem, where [see formula in PDF] is the renormalized quark mass and αem the renormalized fine structure constant. We obtain results for the pion, kaon and Dmeson mass splitting; for the Dashen’s theorem violation parameters ϵγ(MM, 2 GeV), ϵπ0 ϵK0(MS, 2 GeV) for the light quark masses [see formula in PDF] for the flavour symmetry breaking parameters R(MS, 2 GeV) and Q(MS, 2 GeV) and for the strong IB effects on the kaon decay constants.

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Isospin breaking and quark masses in technicolor

Physics Letters B ◽

10.1016/0370-2693(89)90302-x ◽

1989 ◽

Vol 226 (1-2) ◽

pp. 137-141 ◽

Cited By ~ 33

Author(s):

Bob Holdom

Keyword(s):

Isospin Breaking ◽

Quark Masses

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Water, Water, Here and There

10.1093/oso/9780198814825.003.0004 ◽

2018 ◽

Author(s):

Steven E. Vigdor

Keyword(s):

Quark Mass ◽

Mass Difference ◽

Baryon Number ◽

Electroweak Phase Transition ◽

Hydrogen Burning ◽

Quark Masses ◽

Grand Unified Theories ◽

Down Quark ◽

Unified Theories ◽

The Stability

Chapter 4 deals with the stability of the proton, hence of hydrogen, and how to reconcile that stability with the baryon number nonconservation (or baryon conservation) needed to establish a matter–antimatter imbalance in the infant universe. Sakharov’s three conditions for establishing a matter–antimatter imbalance are presented. Grand unified theories and experimental searches for proton decay are described. The concept of spontaneous symmetry breaking is introduced in describing the electroweak phase transition in the infant universe. That transition is treated as the potential site for introducing the imbalance between quarks and antiquarks, via either baryogenesis or leptogenesis models. The up–down quark mass difference is presented as essential for providing the stability of hydrogen and of the deuteron, which serves as a crucial stepping stone in stellar hydrogen-burning reactions that generate the energy and elements needed for life. Constraints on quark masses from lattice QCD calculations and violations of chiral symmetry are discussed.

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Challenges for a QCD axion at the 10 MeV scale

Journal of High Energy Physics ◽

10.1007/jhep05(2021)138 ◽

2021 ◽

Vol 2021 (5) ◽

Author(s):

Jia Liu ◽

Navin McGinnis ◽

Carlos E. M. Wagner ◽

Xiao-Ping Wang

Keyword(s):

Higgs Boson ◽

Standard Model ◽

Structure Constant ◽

Fine Structure Constant ◽

Multiple Sources ◽

Standard Model Extension ◽

Mixing Angles ◽

Quark Masses ◽

Model Extension ◽

The One

Abstract We report on an interesting realization of the QCD axion, with mass in the range $$ \mathcal{O} $$ O (10) MeV. It has previously been shown that although this scenario is stringently constrained from multiple sources, the model remains viable for a range of parameters that leads to an explanation of the Atomki experiment anomaly. In this article we study in more detail the additional constraints proceeding from recent low energy experiments and study the compatibility of the allowed parameter space with the one leading to consistency of the most recent measurements of the electron anomalous magnetic moment and the fine structure constant. We further provide an ultraviolet completion of this axion variant and show the conditions under which it may lead to the observed quark masses and CKM mixing angles, and remain consistent with experimental constraints on the extended scalar sector appearing in this Standard Model extension. In particular, the decay of the Standard Model-like Higgs boson into two light axions may be relevant and leads to a novel Higgs boson signature that may be searched for at the LHC in the near future.

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Decay amplitudes to three hadrons from finite-volume matrix elements

Journal of High Energy Physics ◽

10.1007/jhep04(2021)113 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

Maxwell T. Hansen ◽

Fernando Romero-López ◽

Stephen R. Sharpe

Keyword(s):

Finite Volume ◽

Decay Amplitude ◽

Weak Decay ◽

Matrix Elements ◽

Isospin Breaking ◽

Final State ◽

Identical Particles ◽

Hadron Decay ◽

Finite State ◽

Particle Decays

Abstract We derive relations between finite-volume matrix elements and infinite-volume decay amplitudes, for processes with three spinless, degenerate and either identical or non-identical particles in the final state. This generalizes the Lellouch-Lüscher relation for two-particle decays and provides a strategy for extracting three-hadron decay amplitudes using lattice QCD. Unlike for two particles, even in the simplest approximation, one must solve integral equations to obtain the physical decay amplitude, a consequence of the nontrivial finite-state interactions. We first derive the result in a simplified theory with three identical particles, and then present the generalizations needed to study phenomenologically relevant three-pion decays. The specific processes we discuss are the CP-violating K → 3π weak decay, the isospin-breaking η → 3π QCD transition, and the electromagnetic γ* → 3π amplitudes that enter the calculation of the hadronic vacuum polarization contribution to muonic g − 2.

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DK I = 0, $$ D\overline{K} $$ I = 0, 1 scattering and the $$ {D}_{s0}^{\ast } $$(2317) from lattice QCD

Journal of High Energy Physics ◽

10.1007/jhep02(2021)100 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Gavin K. C. Cheung ◽

◽

Christopher E. Thomas ◽

David J. Wilson ◽

Graham Moir ◽

...

Keyword(s):

Elastic Scattering ◽

Scattering Amplitudes ◽

Lattice Qcd ◽

Finite Volume ◽

Energy Region ◽

Light Quark ◽

Bound State ◽

Vector Resonance ◽

Quark Masses ◽

Partial Waves

Abstract Elastic scattering amplitudes for I = 0 DK and I = 0, 1 $$ D\overline{K} $$ D K ¯ are computed in S, P and D partial waves using lattice QCD with light-quark masses corresponding to mπ = 239 MeV and mπ = 391 MeV. The S-waves contain interesting features including a near-threshold JP = 0+ bound state in I = 0 DK, corresponding to the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ (2317), with an effect that is clearly visible above threshold, and suggestions of a 0+ virtual bound state in I = 0 $$ D\overline{K} $$ D K ¯ . The S-wave I = 1 $$ D\overline{K} $$ D K ¯ amplitude is found to be weakly repulsive. The computed finite-volume spectra also contain a deeply-bound D* vector resonance, but negligibly small P -wave DK interactions are observed in the energy region considered; the P and D-wave $$ D\overline{K} $$ D K ¯ amplitudes are also small. There is some evidence of 1+ and 2+ resonances in I = 0 DK at higher energies.

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Quarkonia Formation in a Holographic Gravity–Dilaton Background Describing QCD Thermodynamics

Particles ◽

10.3390/particles4020015 ◽

2021 ◽

Vol 4 (2) ◽

pp. 159-177

Author(s):

Rico Zöllner ◽

Burkhard Kämpfer

Keyword(s):

Quark Mass ◽

Heavy Ion ◽

Mass Dependence ◽

Holographic Model ◽

Spectral Functions ◽

Special Aspect ◽

Quark Masses ◽

Ion Collisions ◽

Heavy Quark Mass ◽

Quark Mass Dependence

A holographic model of probe quarkonia is presented, where the dynamical gravity–dilaton background was adjusted to the thermodynamics of 2 + 1 flavor QCD with physical quark masses. The quarkonia action was modified to account for the systematic study of the heavy-quark mass dependence. We focused on the J/ψ and Υ spectral functions and related our model to heavy quarkonia formation as a special aspect of hadron phenomenology in heavy-ion collisions at LHC.

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