Exotic meson decays in the environment with chiral imbalance

Abstract

Abstract. An emergence of Local Parity Breaking (LPB) in central heavy-ion collisions (HIC) at high energies is discussed. LPB in the fireball can be produced by a difference between the number densities of right-and left-handed chiral fermions (Chiral Imbalance) which is implemented by a chiral (axial) chemical potential. The effective meson lagrangian induced by QCD is extended to the medium with Chiral Imbalance and the properties of light scalar and pseudoscalar mesons (π, a 0 ) are analyzed. It is shown that exotic decays of scalar mesons arise as a result of mixing of π and a 0 vacuum states in the presence of chiral imbalance. The pion electromagnetic formfactor obtains an unusual parity-odd supplement which generates a photon polarization asymmetry in pion polarizability. We hope that the above pointed indications of LPB can be identified in experiments on LHC, RHIC, CBM FAIR and NICA accelerators. Topological charge, Chiral Imbalance and axial chemical potentialThe behaviour of baryonic matter under extreme conditions has got recently a lot of interest [1,2]. A medium generated in the heavy ion collisions may serve for detailed studies, both experimental and theoretical, of various phases of hadron matter. In this context new properties of QCD in the hot and dense environment are tested in current accelerator experiments on RHIC and LHC [3,4].In heavy ion collisions, in principle, there are two distinct experimental situations for peripheral and central collisions. In the first case the so-called Chiral Magnetic Effect (CME) can be detected, details see in [5] and also [6] for a review and additional references.In the second case there are some experimental indications of an abnormal dilepton excess in the range of low invariant masses and rapidities and moderate values of the transverse momenta [7]-[11] (see the reviews in [12]), which can be thought of as a result of LPB in the medium (the details can be found in [13]). In particular, in heavy-ion collisions at high energies, with raising temperatures and baryon densities, metastable states can appear in the finite-volume fireball with a nontrivial topological ⋆

Chiral Imbalance in Hadron Matter: Its Manifestation in Photon Polarization Asymmetries

“…For b 2 > 0 in the rest frame of vector (b µ ) = (µ 5 , 0, 0, 0) one can compare the predictions of our effective meson lagrangianwith the lattice estimations [17] that clearly shows the enhancement of CSB [14].…”

“…The general solution of this equation v(b µ ) can be found explicitly [14]. Note that there are different regions for chiral vector, invariant under Lorentz transformations of the fireball frame: chiral imbalance region where b 2 > 0, then in the rest frame the chiral background (b µ ) = (µ 5 , 0, 0, 0); chiral vector imbalance region where b 2 < 0, then in the static frame the chiral background can be along the beam axis (b µ ) = (0, 0, 0, b).…”

“…To fit the physical spectral data [14] one can find λ 1 = 1.64850 × 10, λ 2 = −1.31313 × 10, c = −4.46874 × 10 4 MeV 2 , B = 1.61594 × 10 5 MeV 2 .…”

“…After diagonalization of the mass matrix the states for a 0 and π mesons happen to be mixed. The eigenstatesã,π are easily determined [14].…”

Exotic meson decays and polarization asymmetry in hadron environment with chiral imbalance

“…We would like to consider the possibility that in a collision it could be possible to produce longlived bubbles with a non-vanishing value of the topological charge, where parity is locally broken. These topological fluctuations would take place in a finite volume and large temperature and these topological fluctuations were first proposed by Kharzeev, Pisarski and Tytgat [5] and later considered in a number of works [6][7][8]. Large fluctuations in the gauge field could exist in a hot environment and could generate a local chiral imbalance quarks which is associated with topological charge.…”