arXiv subjects
Publications and source records attributed to N. Maeda.
We studied a feasibility of measuring Higgs boson pair production in a Photon Linear Collider. The optimum energy of gamma gamma collision was estimated with a realistic luminosity distribution. We also discussed simulation study for detecting the signal against W boson pair backgrounds.
An analysis of inclusive pion production in proton-beryllium collisions at 6.4, 12.3, and 17.5 GeV/c proton beam momentum has been performed. The data were taken by Experiment 910 at the Alternating Gradient Synchrotron at the Brookhaven National Laboratory. The differential $π^+$ and $π^-$ production cross sections ($d^2σ/dpdΩ$) are measured up to 400 mRad in $θ_π$ and up to 6 GeV/c in $p_π$. The measured cross section is fit with a Sanford-Wang parameterization.
The induced Chern-Simons term for a paired electron state is calculated in the quantum Hall system by using a field theory on the von Neumann lattice. The coefficient of the Chern-Simons term, which is the Hall conductance, has not only the usual term proportional to a filling factor due to P (parity) & T (time reversal) symmetry breaking but also correction terms due to P & T & U(1) symmetry breaking. The correction term essentially comes from the Nambu-Goldstone mode and depends on an infrared limit. It is shown that the correction term is related to a topological number of a gap function in the momentum space.
Published measurements of semi-inclusive Lambda production in p-Au collisions at the AGS are used to estimate the yields of singly strange hadrons in nucleus-nucleus A-A collisions. Results of a described extrapolation technique are shown and compared to measurements of K+ production in Si-Al, Si-Au, and Au-Au collisions at the AGS and net Lambda production in Su-Su, S-Ag, Pb-Pb, and inclusive p-A collisions at the SPS. The extrapolations can account for more than 75% of the measured strange particle yields in all of the studied systems except for very central Au-Au collisions at the AGS where RQMD comparisons suggest large re-scattering contributions.
Using symmetries of the current correlation function, we analyze the frequency dependence of the photon energy absorption rate of a striped Hall gas. Since the magnetic translational symmetry is spontaneously broken in the striped Hall gas, a Nambu-Goldstone (NG) mode appears. It is shown that the NG mode causes a sharp absorption at the zero energy in the long wavelength limit by using the single mode approximation. The photon energy absorption rate at the NG mode frequency strongly depends on the direction of the wave number vector. Whereas, the absorption rate at the cyclotron frequency does not depend on the direction of the wave number vector in the long wavelength limit. The cyclotron resonance is not affected in the striped Hall gas. Our result supplements the Kohn's theorem in the system of the NG mode.
We calculate the polarization function including only intra-Landau level correlation effects of striped Hall gas. Using the polarization function, the dielectric function, the dispersion of the plasmon and the correlation energy are computed in a random phase approximation (RPA) and generalized random phase approximation (GRPA). The plasmon becomes anisotropic and gapless owing to the anisotropy of the striped Hall gas and two dimensionality of the quantum Hall system. The plasmon approximately agrees with the phonon derived before by the single mode approximation. The (G)RPA correlation energy is compared with other numerical calculations.
The von Neumann lattice representation is a convenient representation for studying several intriguing physics of quantum Hall systems. In this formalism, electrons are mapped to lattice fermions. A topological invariant expression of the Hall conductance is derived and is used for the proof of the integer quantum Hall effect in the realistic situation. Anisotropic quantum Hall gas is investigated based on the Hartree-Fock approximation in the same formalism. Thermodynamic properties, transport properties, and unusual response under external modulations are found. Implications for the integer quantum Hall effect in the finite systems are also studied and a new quantum Hall regime with non-zero longitudinal resistance is shown to exist.
Neutral collective excitations in the striped Hall state are studied by using the single mode approximation and Hartree-Fock approximation at the half-filled third and fourth Landau level. We find that the spectrum includes anisotropic NG modes and periodic line nodes.
The physical properties of striped Hall state in the presence of an external unidirectional periodic potential is investigated. The study of searching the optimal orientation of the state is reported for the state at filling factor $ν=2+1/2$ and for the state at higher Landau levels at $l+1/2$ where $l=3,4,5,6,7,8$. It is predicted that two phases of the orientation, parallel phase and perpendicular phase, exist and a phase transition from one to another phase occurs.
In the striped Hall state, a magnetic translation in one direction is spontaneously broken to the discrete translation. The spectrum of the neutral collective excitation is obtained in the single mode approximation at half-filled third and fourth Landau levels. The spectrum is anisotropic and has a multiple line node structure. In one direction, the spectrum resembles the liquid Helium spectrum with the phonon and roton minimum.
We investigate neutral collective excitations in the striped Hall state. In the striped Hall state, the magnetic translation and rotation symmetries are spontaneously broken. Using the commutation relation between charges and currents corresponding to the broken and unbroken symmetry, the existence of the gapless neutral excitation is proved. The spectrum of the neutral collective excitation at the half-filled third Landau level is obtained in the single mode approximation. We find the periodic line nodes in the spectrum. The spectrum is compared with the particle-hole excitation spectrum in the Hartree-Fock approximation.
We study striped states in the quantum Hall system around half-filled high Landau levels and obtain the optimal orientation of the striped state in the presence of an external unidirectional periodic potential. It is shown that the optimal orientation is orthogonal to the external modulation in the Coulomb dominant regime (the orthogonal phase) and is parallel in the external modulation dominant regime (the parallel phase). The phase boundary of these two phases is determined numerically in the parameter space of the strength and wave number of the external modulation at the half-filled third Landau level.
Physical properties of anisotropic compressible quantum Hall states and their implications to integer quantum Hall effect are studied based on a mean field theory on the von Neumann lattice. It is found that the Hall gas has unusual thermodynamic properties such as negative pressure and negative compressibility and unusual transport properties. Transport properties and density profile of Hall gas states at half fillings agree with those of anisotropic states discovered experimentally in higher Landau levels. Hall gas formed in the bulk does not spread but shrinks, owing to negative pressure, and a strip of Hall gas gives abnormal electric transport at finite temperature. Conductances at finite temperature and finite injected current agree with recent experiments on collapse and breakdown phenomena of the integer quantum Hall effect. As a byproduct, existence of new quantum Hall regime, dissipative quantum Hall regime, in which Hall resistance is quantized exactly even in the system of small longitudinal resistance is derived.
Differential cross-sections are presented for the inclusive production of charged pions in the momentum range 0.1 to 1.2 GeV/c in interactions of 12.3 and 17.5 GeV/c protons with Be, Cu, and Au targets. The measurements were made by Experiment 910 at the Alternating Gradient Synchrotron in Brookhaven National Laboratory. The cross-sections are presented as a function of pion total momentum and production polar angle $θ$ with respect to the beam.
Inclusive and semi-inclusive measurements are presented for antiproton ($\bar{p}$) production in proton-nucleus collisions at the AGS. The inclusive yields per event increase strongly with increasing beam energy and decrease slightly with increasing target mass. The $\bar{p}$ yield in 17.5 GeV/c p+Au collisions decreases with grey track multiplicity, $N_g$, for $N_g>0$, consistent with annihilation within the target nucleus. The relationship between $N_g$ and the number of scatterings of the proton in the nucleus is used to estimate the $\bar{p}$ annihilation cross section in the nuclear medium. The resulting cross section is at least a factor of five smaller than the free $\bar{p}-p$ annihilation cross section when assuming a small or negligible formation time. Only with a long formation time can the data be described with the free $\bar{p}-p$ annihilation cross section.
Thermodynamic and electric properties of anisotropic compressible Hall states at higher Landau levels are studied using a mean field theory on the von Neumann lattice basis. It is shown that resistances agree with the recent experiments of anisotropic compressible states and the states have negative pressure. As implications, the collapse phenomena of the integer quantum Hall effect are discussed.
The first detailed measurements of the centrality dependence of strangeness production in p-A collisions are presented. Lambda and Kshort dn/dy distributions from 17.5 GeV/c p-Au collisions are shown as a function of "grey" track multiplicity and the estimated number of collisions, nu, made by the proton. The nu dependence of the Lambda yield deviates from a scaling of p-p data by the number of participants, increasing faster than this scaling for nu<=5 and saturating for larger nu. A slower growth in Kshort multiplicity with nu is observed, consistent with a weaker nu dependence of K-Kbar production than Y-K production.
Pressure, compressibility, and Hall conductance of anisotropic states at higher Landau levels are computed. Pressure and compressibility become negative. Hall conductance is unquantized and varies with filling factor. These facts agree with the recent experimental observations of highly anisotropic compressible states at higher Landau levels. It is shown, as an implication of negative pressure, that the quantum Hall effect has extraordinary stability, that is, Hall resistance is quantized even when the longitudinal resistance does not vanish.