14791294
Heavy-heavy-light quark potential in SU(3) lattice QCD
Abstract We perform the first study for the heavy–heavy–light quark ( QQq ) potential in SU ( 3 ) quenched lattice QCD with the Coulomb gauge. The calculations are done with the standard gauge and O ( a ) -improved Wilson fermion action on the 16 4 lattice at β = 6.0 . We calculate the energy of QQq systems as the function of the distance R between the two heavy quarks, and find that the QQq potential is well described with a Coulomb plus linear potential form up to the intermediate distance R ⩽ 0.8 fm . Compared to the static three-quark case, the effective string tension between the heavy quarks is significantly reduced by the finite-mass valence quark effect. This reduction is considered to be a general property for baryons.
119245257
QCD Dirac spectrum and components of the gauge field
Abstract We analyze the relation between the Dirac spectrum and the gauge field in SU(3) lattice QCD. We focus on how a certain component of the gauge field is related to the Dirac spectrum. First, we consider momentum components of the gauge field. It turns out that the broad momentum region is relevant for the low-lying Dirac spectrum and topological charges. The connection with chiral random matrix theory is also discussed. Second, we consider an SU(2) subgroup component of the SU(3) gauge field. The SU(2) subgroup component behaves like the SU(2) gauge field in the low-lying Dirac spectrum.
119264611
Relevant gluonic energy scale of spontaneous chiral symmetry breaking from lattice QCD
We analyze which momentum component of the gluon field induces spontaneous chiral symmetry breaking in lattice QCD. After removing the high-momentum or low-momentum component of the gluon field, we calculate the chiral condensate and observe the roles of these momentum components. The chiral condensate is found to be drastically reduced by removing the zero-momentum gluon. The reduction is about 40% of the total in our calculation condition. The nonzero-momentum infrared gluon also has a sizable contribution to the chiral condensate. From the Banks-Casher relation, this result reflects the nontrivial relation between the infrared gluon and the zero-mode quark.
27061707
Lattice QCD in rotating frames.
We formulate lattice QCD in rotating frames to study the physics of QCD matter under rotation. We construct the lattice QCD action with the rotational metric and apply it to the Monte Carlo simulation. As the first application, we calculate the angular momenta of gluons and quarks in the rotating QCD vacuum. This new framework is useful to analyze various rotation-related phenomena in QCD.
118515420
Charged vector mesons in a strong magnetic field
We show that charged vector mesons cannot be condensed by a magnetic field. Although some hadron models predict the charged vector meson condensation in a strong magnetic field, we prove, by means of the Vafa-Witten theorem, that this is not the case in QCD. We also perform the numerical analysis for the meson mass and condensation in lattice QCD. The lattice QCD data confirm no charged vector meson condensation in a magnetic field.
4592271
Lattice analysis for the energy scale of QCD phenomena.
We formulate a new framework in lattice QCD to study the relevant energy scale of QCD phenomena. By considering the Fourier transformation of link variable, we can investigate the intrinsic energy scale of a physical quantity nonperturbatively. This framework is broadly available for all lattice QCD calculations. We apply this framework for the quark-antiquark potential and meson masses in quenched lattice QCD. The gluonic energy scale relevant for the confinement is found to be less than 1 GeV in the Landau or Coulomb gauge.
19387199
In-Line Control in T2K Proton Beam Line Magnet Safety System
Magnet Safety Systems (MSS) frequently use quench detection based on voltage measurement, in order to protect superconducting magnets. Disconnecting quench detection cables and using a voltage generator to simulate quench voltages is a good way to check the system. This paper describes another method, with a hardware and software in-line control system, used to periodically check the MSS of the 28 superconducting magnets of the T2K proton beam line, at J-PARC. With in-line control, an isolated simulation voltage is added to each real input voltage of the detectors, without disconnecting quench detection cables. In-line control can also check if quench detection cables are connected or not, and if a detection wire is broken. In-line control is realized with additional electronic hardware and software on the MSS electronic boards and with a connection to a PC with a specific software and Graphic User Interface running under Windows. Nevertheless, quench detection and safety actions are always based on hardware only. Extreme care is taken so that in-line control cannot prevent the MSS to protect the magnet system, even if software stops running. Other remote functions are also available with this system, like monitoring of analog and logical signals and setting of detection and electronic parameters, if needed.
21013020
Conduction Cooling Test of a Splittable Quadrupole for ILC Cryomodules
A superconducting splittable quadrupole magnet was designed at Fermilab for use in ILC-style cryomodules, in which the magnet is to be assembled around the beam tube to avoid contaminating the ultraclean superconducting RF beam volume. This quadrupole was built and first tested in a liquid helium bath environment at Fermilab, where its quench and magnetic performance were characterized. The device is intended to be cooled by conduction when installed in cryomodules, so a separate test was made at KEK where an appropriate conduction cooling test facility exists. We present results of the thermal performance of the magnet in the conduction cooling mode, and discuss its excitation characteristics in this operating mode.