40,021 research outputs found
Analyses of multiplicity distributions by means of the Modified Negative Binomial Distribution and its KNO scaling function
We analyze various data of multiplicity distributions by means of the
Modified Negative Binomial Distribution (MNBD) and its KNO scaling function,
since this MNBD explains the oscillating behavior of the cumulant moment
observed in e^+e^- annihilations, h-h collisions and e-p collisions. In the
present analyses, we find that the MNBD(discrete distributions) describes the
data of charged particles in e^+e^- annihilations much better than the Negative
Binomial Distribution (NBD). To investigate stochastic property of the MNBD, we
derive the KNO scaling function from the discrete distribution by using a
straightforward method and the Poisson transform. It is a new KNO function
expressed by the Laguerre polynomials. In analyses of the data by using the KNO
scaling function, we find that the MNBD describes the data better than the
gamma function.Thus, it can be said that the MNBD is one of useful formulas as
well as NBD.Comment: 12 pages, latex, 3 figure
Kosterlitz-Thouless Phase Transition of the ANNNI model in Two Dimensions
The spin structure of an axial next-nearest-neighbor Ising (ANNNI) model in
two dimensions (2D) is a renewed problem because different Monte Carlo (MC)
simulation methods predicted different spin orderings. The usual equilibrium
simulation predicts the occurrence of a floating incommensurate (IC)
Kosterlitz-Thouless (KT) type phase, which never emerges in non-equilibrium
relaxation (NER) simulations. In this paper, we first examine previously
published results of both methods, and then investigate a higher transition
temperature, , between the IC and paramagnetic phases. In the usual
equilibrium simulation, we calculate the layer magnetization on larger lattices
(up to sites) and estimate with
frustration ratio . We examine the nature of
the phase transition in terms of the Binder ratio of spin overlap
functions and the correlation-length ratio . In the NER simulation, we
observe the spin dynamics in equilibrium states by means of an autocorrelation
function, and also observe the layer magnetization relaxations from the ground
and disordered states. These quantities exhibit an algebraic decay at . We conclude that the two-dimensional ANNNI model actually
admits an IC phase transition of the KT type.Comment: 20 pages, 16 figure
Observation of EAS using a large water tank
Using a large water tank (30 m in diameter, 4.5 m in depth) transition of extensive air showers (EAS) was investigated at Taro (200 m above sea level). There are set 150,0.4 sq m proportional counters on the bottom of the water tank. A conventional EAS array of 25 plastic scintillation detectors was arranged within several tens meter from the water tank. A proportional counter (10x10x200 cc x2) is made of a square shaped pipe of iron. Tungsten wire (100 mu m phi) is stretched tight in the center of the counter. A gas mixture of 90% argon and 10% methane is used at 760 mmHg. About 3000 EAS were obtained through 1 m of water since 1984
Study of Magnetic Excitation in Singlet-Ground-State Magnets CsFeCl and RbFeCl by Nuclear Magnetic Relaxation
The temperature dependences of spin-lattice relaxation time of
Cs in CsFeCl and Rb in RbFeCl were measured in the
temperature range between 1.5 K and 22 K, at various fields up to 7 T applied
parallel (or perpendicular) to the c-axis, and the analysis was made on the
basis of the DCEFA. The mechanism of the nuclear magnetic relaxation is
interpreted in terms of the magnetic fluctuations which are characterized by
the singlet ground state system. In the field region where the phase transition
occurs, exhibited the tendency of divergence near , and
this feature was ascribed to the transverse spin fluctuation associated with
the mode softening at the -point. It was found that the damping constant of
the soft mode is remarkably affected by the occurrence of the magnetic ordering
at lower temperature, and increases largely in the field region where the phase
transition occurs.Comment: 12 pages, 18 figures, submitted to J. Phys. Soc. Jp
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