Chiral condensates and screening masses of neutral pseudoscalar mesons in thermomagnetic QCD medium

Abstract

We point out that chiral condensates at nonzero temperature and magnetic fields are in strict connection to the space-time integral of corresponding two-point neutral meson correlation functions in the pseudoscalar channel via the Ward-Takahashi identity. Screening masses of neutral pseudoscalar mesons, which are defined as the exponential decay of the corresponding spatial correlation functions in the long distance, thus are intrinsically connected to (inverse) magnetic catalysis of chiral condensates. To study this we performed lattice simulations of (2 + 1)-flavor QCD on 32 3 × Nt lattices with pion mass Mπ 220 MeV in a fixed scale approach having temperature T ∈ [17, 281] MeV and magnetic field strength eB ∈ [0, 2.5] GeV 2 . We find that screening lengths, i.e. inverses of screening masses of π 0 , K 0 and η 0 ss , turn out to have the similar complex eB and T dependences of the corresponding chiral condensates. Although the transition temperature is found to always decrease as eB grows, we show that the suppression due to magnetic fields becomes less significant for hadron screening length and chiral condensates with heavier quarks involved, and ceases to occur for η 0 ss and strange quark chiral condensate. The complex eB and T dependences of both screening masses and chiral condensates, reflecting the crossover nature of the QCD transition, are attributed to the competition between sea and valence quark effects. These findings could be useful to guide low-energy models and effective theories of QCD.

Magnetized pole-mass of neutral $ρ$ meson within full RPA evaluation

“…A very good way to test many properties of the quark matter under strong magnetic fields is to understand what is the behavior of the lightest mesons and its properties. Recent lattice QCD [31][32][33][34][35][36][37][38] and several effective model studies have been focused on the calculation on the masses of neutral and charged pions [24,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56], ρ 0 and ρ ± [57-60] an its properties. These results can be useful for extensions of the effetive models for application in beyond-mean-field approaches [61].…”

Quark condensate in QCD at nonzero magnetic field and temperature

“…We start with the simplest example of the quark condensate for the zero mass quarks which can be associated with Σ u , Σ d . Using (17) and [27] for the light quark theoretical values of R l 1s (0) = 0.376(8) GeV 3/2 , one obtains…”

“…which can be compared to numerous lattice data [4,5,6,7,8,9,10,11,12,13,14,15,16,17], e.g. in [30] Σ l = (283(2) MeV) 3 .…”

“…We now make the same series of approximations as in ( 16), (17), replacing m l + M 0 by c 0 m (+−) and keeping in the sum in (22) only the leading first term with n = 0 and obtain…”

“…Therefore the most important problem is to find the origin of this parameter and its connection and role in the overall dynamics of QCD, in particular, the connection of Σ i and the string tension σ, which provides confinement. This topic was intensively studied in the framework of the QCD lattice theory [4,5,6,7,8,9,10,11,12,13,14,15,16,17]. In the previous papers we have exploited the Chiral Confining theory (CCTh) [18,19,20,21,22,23] to calculate the chiral meson masses and the quark condensate via the string tension and the quark masses, where an additional parameter λ -the effective radius of the meson state, can be used as a multiplicative constant.…”