scholarly journals CHIRAL PARTNERS IN A CHIRALLY BROKEN WORLD

2009 ◽  
Vol 24 (02n03) ◽  
pp. 229-236 ◽  
Author(s):  
STEFAN LEUPOLD ◽  
MARKUS WAGNER
Keyword(s):  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Axial Vector ◽  
Vector Current ◽  
The Other ◽  
Other Hand ◽  
Chiral Transformation ◽  
Pion Interaction ◽  
Hadronic Level ◽  
Prominent Peak

The isovector–vector and the isovector–axial-vector current are related by a chiral transformation. These currents can be called chiral partners at the fundamental level. In a world where chiral symmetry was not broken, the corresponding current-current correlators would show the same spectral information. In the real world chiral symmetry is spontaneously broken. A prominent peak — the ρ-meson — shows up in the vector spectrum (measured in e+e--collisions and τ-decays). On the other hand, in the axial-vector spectrum a broad bump appears — the a1-meson (also accessible in τ-decays). It is tempting to call ρ and a1 chiral partners at the hadronic level. Strong indications are brought forward that these "chiral partners" do not only differ in mass but even in their nature: The ρ-meson appears dominantly as a quark-antiquark state with small modifications from an attractive pion-pion interaction. The a1-meson, on the other hand, can be understood as a meson-molecule state mainly formed by the attractive interaction between pion and ρ-meson. A key issue here is that the meson-meson interactions are fixed by chiral symmetry breaking. It is demonstrated that one can understand the vector and the axial-vector spectrum very well within this interpretation. It is also shown that the opposite cases, namely ρ as a pion-pion molecule or a1 as a quark-antiquark state lead to less satisfying results. Finally speculations on possible in-medium changes of hadron properties are presented.

scholarly journals Nuclear currents in chiral effective field theory

2020 ◽  
Vol 56 (9) ◽  
Author(s):  
Hermann Krebs
Keyword(s):  
Field Theory ◽  
Chiral Symmetry ◽  
Effective Field Theory ◽  
Unitary Transformation ◽  
Axial Vector ◽  
Vector Current ◽  
Effective Field ◽  
Axial Vector Current ◽  
Leading Order ◽  
Chiral Effective Field Theory

Abstract In this article, we review the status of the calculation of nuclear currents within chiral effective field theory. After formal discussion of the unitary transformation technique and its application to nuclear currents we give all available expressions for vector, axial-vector currents. Vector and axial-vector currents are discussed up to order Q with leading-order contribution starting at order $$Q^{-3}$$ Q - 3 . Pseudoscalar and scalar currents will be discussed up to order $$Q^0$$ Q 0 with leading-order contribution starting at order $$Q^{-4}$$ Q - 4 . This is a complete set of expressions in next-to-next-to-next-to-leading-order (N$$^3$$ 3 LO) analysis for nuclear scalar, pseudoscalar, vector and axial-vector current operators. Differences between vector and axial-vector currents calculated via transfer-matrix inversion and unitary transformation techniques are discussed. The importance of a consistent regularization is an additional point which is emphasized: lack of a consistent regularization of axial-vector current operators is shown to lead to a violation of the chiral symmetry in the chiral limit at order Q. For this reason a hybrid approach at order Q, discussed in various publications, is non-applicable. To respect the chiral symmetry the same regularization procedure needs to be used in the construction of nuclear forces and current operators. Although full expressions of consistently regularized current operators are not yet available, the isoscalar part of the electromagnetic charge operator up to order Q has a very simple form and can be easily regularized in a consistent way. As an application, we review our recent high accuracy calculation of the deuteron charge form factor with a quantified error estimate.

NONPERTURBATIVE QCD, THE CONSTITUENT QUARK MODEL AND CONFINEMENT

1988 ◽  
Vol 03 (01) ◽  
pp. 203-223 ◽  
Author(s):  
B.H.J. MCKELLAR ◽  
M.D. SCADRON ◽  
R.C. WARNER
Keyword(s):  
Quark Model ◽  
Chiral Symmetry ◽  
Constituent Quark ◽  
Chiral Symmetry Breaking ◽  
Constituent Quark Model ◽  
The Other ◽  
Hadron Structure ◽  
Potential Models ◽  
Dynamical Breaking ◽  
Quark Models

There are currently two major QCD-inspired quark models for hadrons. Nonrelativistic potential models and ultrarelativistic bag models have both had their successes. In this paper we present the case for an alternative quark picture, emphasizing the nonperturbative dynamical breaking of chiral symmetry in QCD. The relativistic constituent quark model which emerges recovers the main results of the other approaches, and also holds better prospects for the calculation of relativistic phenomena, and for the eventual understanding of the interrelations between chiral-symmetry breaking, hadron structure and confinement.

scholarly journals NEW ANGLE ON THE STRONG CP AND CHIRAL SYMMETRY PROBLEMS FROM A ROTATING MASS MATRIX

2009 ◽  
Vol 24 (01) ◽  
pp. 101-112 ◽  
Author(s):  
JOSÉ BORDES ◽  
HONG-MO CHAN ◽  
TSOU SHEUNG TSUN
Keyword(s):  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Mass Matrix ◽  
Energy Scale ◽  
Fermion Mass ◽  
Mass Hierarchy ◽  
Quark Masses ◽  
Chiral Transformation ◽  
The Masses ◽  
Fermion Mass Matrix

It is shown that when the mass matrix changes in orientation (i.e. rotates) in generation space for a changing energy scale, the masses of the lower generations are not given just by its eigenvalues. In particular, these masses need not be zero even when the eigenvalues are zero. In that case, the strong CP problem can be avoided by removing the unwanted θ term by a chiral transformation not in contradiction with the nonvanishing quark masses experimentally observed. Similarly, a rotating mass matrix may shed new light on the problem of chiral symmetry breaking. That the fermion mass matrix may so rotate with the scale has been suggested before as a possible explanation for up–down fermion mixing and fermion mass hierarchy, giving results in good agreement with experiment.

scholarly journals Axial vector current of exact chiral symmetry on the lattice

1999 ◽  
Vol 547 (1-2) ◽  
pp. 413-423 ◽  
Author(s):  
Yoshio Kikukawa ◽  
Atsushi Yamada
Keyword(s):  
Chiral Symmetry ◽  
Axial Vector ◽  
Vector Current ◽  
Axial Vector Current

scholarly journals CHIRAL SYMMETRY BREAKING IN A SOFT-WALL MODEL OF AdS/QCD

2010 ◽  
Vol 25 (02n03) ◽  
pp. 453-463 ◽  
Author(s):  
JOSEPH I. KAPUSTA ◽  
THOMAS M. KELLEY ◽  
TONY GHERGHETTA
Keyword(s):  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Mass Spectra ◽  
Chiral Symmetry Breaking ◽  
Scalar Potential ◽  
Axial Vector ◽  
Wall Model ◽  
Quartic Term ◽  
Soft Wall Model ◽  
Soft Wall

We incorporate chiral symmetry breaking in a soft-wall version of the AdS/QCD model by using a modified dilaton profile and a quartic term in the bulk scalar potential. This allows one to separate the dependence on spontaneous and explicit chiral symmetry breaking. The resulting mass spectra in the scalar, vector and axial-vector sectors compares favorably with the respective QCD resonances.

scholarly journals Multivacuum states in a fermionic gap equation with massive gluons and confinement

2015 ◽  
Vol 30 (13) ◽  
pp. 1550061
Author(s):  
R. M. Capdevilla
Keyword(s):  
Symmetry Breaking ◽  
Quantum Chromodynamics ◽  
Chiral Symmetry ◽  
Previous Analysis ◽  
Chiral Symmetry Breaking ◽  
Stable Solution ◽  
The Other ◽  
Nontrivial Solutions ◽  
Gap Equation ◽  
Gluon Mass

We study the nontrivial solutions of the Quantum Chromodynamics (QCD) fermionic gap equation (FGE) including the contribution of dynamically massive gluons and the confining propagator proposed by Cornwall. Without the confining propagator, in the case of nonrunning gluon mass (mg), we found the multivacuum solutions (replicas) reported in the literature and we were able to define limits on mg for dynamical chiral symmetry breaking (CSB). On the other side, when considering the running in the gluon mass the vacuum replicas are absent in the limits on mg where the chiral symmetry is broken. In the pure confining sector, the multivacuum states are always absent so it is said that only one stable solution for the gap equation is found as claimed in previous analysis using different approaches. Finally, in the case of the complete gap equation i.e. with both contributions, the vacuum replicas are also absent in both cases; with constant and with running gluon mass.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

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