Lattice Quantum Monte Carlo Study of Chiral Magnetic Effect in Dirac Semimetals

In this paper Chiral Magnetic Effect (CME) in Dirac semimetals is studied by means of lattice Monte Carlo simulation. We measure conductivity of Dirac semimetals as a function of external magnetic field in parallel $\sigma_{\parallel}$ and perpendicular $\sigma_{\perp}$ to the external field directions. The simulations are carried out in three regimes: semimetal phase, onset of the insulator phase and deep in the insulator phase. In the semimetal phase $\sigma_{\parallel}$ grows whereas $\sigma_{\perp}$ drops with magnetic field. Similar behaviour was observed in the onset of the insulator phase but conductivity is smaller and its dependence on magnetic field is weaker. Finally in the insulator phase conductivities $\sigma_{\parallel, \perp}$ are close to zero and do not depend on magnetic field. In other words, we observe manifestation of the CME current in the semimetal phase, weaker manifestation of the CME in the onset of the insulator phase. We do not observe signatures of CME in the insulator phase. We believe that the suppression of the CME current in the insulator phase is connected to chiral symmetry breaking and generation of dynamical fermion mass which take place in this phase.Comment: 6 pages, 4 figure

Thermal phase transitions in rotating QCD with dynamical quarks

Relativistic rotation causes a change of QCD critical temperatures. Various phenomenological and effective models predict a decrease of the critical temperatures in rotating QCD. Nevertheless, lattice simulations showed that the critical temperature in gluodynamics increases due to rotation. We extend the lattice study to the theory with dynamical fermions. We present the first lattice results for rotating QCD with $N_f=2$ dynamical clover-improved Wilson quarks. We also study separately the effect of rotation on gluonic and fermionic degrees of freedom. It is shown that separate rotations of gluons and fermions have opposite effects on the critical temperatures. In aggregate, the pseudo-critical temperatures in QCD increase with angular velocity. Dependence of the results on the pion mass is also discussed.Comment: 10 pages, 5 figures, Proceedings of the 39th International Symposium on Lattice Field Theory, 8th-13th August, 2022, Bonn, German

Phase diagram and Chiral Magnetic Effect in Dirac Semimetals from Lattice Simulation

Dirac Semimetals Na 3 Bi and Cd 3 As 2 are recently discovered materials, which low energy electronic spectrum is described by two flavours of massless 3+1D fermions. In order to study electronic properties of these materials we formulated lattice field theory with rooted staggered fermions on anisotropic lattice. It is shown that in the limit of zero temporal lattice spacing this theory reproduces effective theory of Dirac semimetals. Using the lattice field theory we study the phase diagram of Dirac semimetals in the plane effective coupling constant - Fermi velocity anisotropy. We also measure conductivity of Dirac Semimetals within lattice field theory in external magnetic field. Our results confirm the existence of Chiral Magnetic Effect in Dirac Semimetals. © The Authors, published by EDP Sciences, 2018.Acknowdedgements. The work supported by the RSF grant under contract 16-12-10059. Numerical simulations were carried out on GPU cluster of NRC Kurchatov Institute and at MSU supercomputer "Lomonosov".Consejo Superior de Investigaciones Cient�ficas;et al.;Institute of Cosmos Sciences (ICCUB);Universidad Aut�noma de Madrid (UAM);Universidad de Granada;Universidad Valenci

Progress in crystal extraction and collimation

Recent IHEP Protvino experiments show efficiencies of crystal-assisted slow extraction and collimation of 85.3+-2.8%, at the intensities of the channeled beam on the order of 10^12 proton per spill of 2 s duration. The obtained experimental data well follows the theory predictions. We compare the measurements against theory and outline the theoretical potential for further improvement in the efficiency of the technique. This success is important for the efficient use of IHEP accelerator and for implementation of crystal-assisted collimation at RHIC and slow extraction from AGS onto E952, now in preparation. Future applications, spanning in the energy from order of 1 GeV (scraping in SNS, slow extraction from COSY and medical accelerators) to order of 1 TeV and beyond (scraping in Tevatron, LHC, VLHC), can benefit from these studies.Comment: 7pp. Presented at HEACC 2001 (Tsukuba, March 25-30

Crystal experiments on efficient beam extraction

Silicon crystal was channeling and extracting 70-GeV protons from the U-70 accelerator with efficiency of 85.3+-2.8% as measured for a beam of 10^12 protons directed towards crystals of 2 mm length in spills of 1-2 s duration. The experimental data follow very well the prediction of Monte Carlo simulations. This success is important to devise a more efficient use of the U-70 accelerator in Protvino and provides a crucial support for implementation of crystal-assisted collimation of gold ion beam in RHIC and slow extraction from AGS onto E952, now in preparation at Brookhaven Nat'l Lab. Future applications, spanning in the energy from sub-GeV (medical) to order of 1 GeV (scraping in the SNS, extraction from COSY) to order of 1 TeV and beyond (scraping in the Tevatron, LHC, VLHC), can benefit from these studies.Comment: 12pp. Presented at 19-th Intern. Conference on Atomic Collisions in Solids (ICACS-19: Paris, July 29 - August 3, 2001

Highly efficient crystal deflector for channeling extraction of a proton beam from accelerators

The design and performance of a novel crystal deflector for proton beams are reported. A silicon crystal was used to channel and extract 70 GeV protons from the U-70 accelerator in Protvino with an efficiency of 85%, as measured for a beam of ~1e12 protons directed towards crystals of ~2 mm length in spills of ~2 s duration. Experimental data agree with the theoretically predicted Monte Carlo results for channeling. The technique allows one to manufacture a very short deflector along the beam direction (2 mm). Consequently, multiple encounters of circulating particles with the crystal are possible with little probability of multiple scattering and nuclear interactions per encounter. Thus, drastic increase in efficiency for particle extraction out of the accelerator was attained. We show the characteristics of the crystal- deflector and the technology behind it. Such an achievement is important in devising a more efficient use of the U-70 accelerator and provides crucial support for implementing crystal-assisted slow extraction and collimation in other machines, such as the Tevatron, RHIC, the AGS, the SNS, COSY, and the LHC.Comment: Presented at PAC 2003 (Portland, May 12-16