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N. Suzuki

Publications and source records attributed to N. Suzuki.

At least 91 records · Page 5Linked to original sources
arXiv2004

A Concordance Model of the Lyman-alpha Forest at z = 1.95

We present 40 fully hydrodynamical numerical simulations of the intergalactic gas that gives rise to the Ly-alpha forest. We make artificial spectra from each and measure three output parameters: the mean flux, a measure of the most common Ly-alpha line width (b-value), and the 1D power spectrum of the flux on scales from 0.01 - 0.1 s/km. We investigate how these output parameters are correlated with the input parameters that describe the simulations. These input parameters include the main cosmological parameters; and two astrophysical parameters gammah and gammahe. The parameter gammah controls the rate of ionization of H I, He I and He II while gammahe controls the rate of heating. We compare the output from the simulations to data from HIRES and UVES spectra and we give a new measurement of the flux power from these spectra at z=1.95. We find that simulations with a wide variety of sigma_8 values, from at least 0.8 - 1.1, can fit the small scale flux power and b-values when we adjust gammahe to compensate for the sigma_8 change. We can also use gammah to adjust the H I ionization rate to simultaneously match the mean flux. We derive scaling relations that give the output parameter values expected for a variety of input parameters with errors of 2% for optical depth and 1.4% for b-balues. We can break the degeneracy between gammahe and sigma_8 using large scale power or other data to fix sigma_8.

astro-ph↗
arXiv2004

H I gas in higher density regions of the intergalactic medium

Using H I absorption alone, we attempt to separate H I absorption lines in quasar spectra into two categories; HDLs (Higher Density Lines) and LDLs (Lower Density Lines), and we discuss the difference in their physical properties. We deblend and fit all H I lines with Voigt profiles, and make an unbiased sample of H I lines covering a wide column density range (12 < log N_HI < 19 cm^-2). To reduce the influence of line blending, we simultaneously fit several Lyman series lines. As a result of a two-point correlation analysis, we found that higher column density H I lines are clustering at $Δ$ v < 200 km/s, while lower ones at $Δ$ v < 100 km/s. We define HDLs as H I lines with 15 < log N_HI < 19 cm^-2 and all H I lines within +/- 200 km/s of a line with log N_HI > 15 cm^-2, and LDLs as others with 12 < log N_HI < 15 cm^-2. We found that the HDLs have smaller minimum b-values for a given column density than the LDLs. This difference is successfully reproduced by our Hydrodynamic simulation. The LDLs seem to be cool or shock-heated diffuse IGM gas, while the HDLs are likely to be cooler dense gas near to galaxies.

astro-ph↗
arXiv2003

A formulation for description of pi^+(2pi^-) and pi^-(2pi^+) channels in Bose-Einstein correlation by Coulomb wave function

In order to analyze data on charged pions correlation channels, pi^+(2pi^-) and pi^-(2pi^+), we propose new interferometry approach using the Coulomb wave function. We show that to describe adequately data we have to introduce new parameter describing the contribution of pi^-(k_1) pi^+(k_2) --> pi^-(k_2) pi^+(k_1) process. Using this new formula we analyze data on pi^+(2pi^-) and pi^-(2pi^+) channels at sqrt(s) = 91 GeV by DELPHI Collaboration, and estimate the magnitude of this new parameter as well as the degree of coherence.

hep-ph↗
arXiv2002

Scaling Behavior of $(N_{ch})^{-1}dN_{ch}/dη$ at $\sqrt{s_{NN}} = 130$ GeV by the PHOBOS Collaboration and Its Implication --A Possible Explanation Employing the Ornstein-Uhlenbeck Process--

Recently, interesting data concerning $dN_{ch}/dη$ in Au-Au collisions [$η=-\ln \tan (θ/2)$] with centrality cuts have been reported from the PHOBOS Collaboration. In most treatment these data are divided by the number of participants (nucleons) in collisions. Instead of this method, we use the total multiplicity $N_{ch} = \int (dN_{ch}/dη)dη$ and find that there is scaling phenomenon among $(N_{ch})^{-1}dN_{ch}/dη= dn/dη$ with different centrality cuts at $\sqrt{s_{NN}} = 130$ GeV. To explain this scaling behavior of $dn/dη$, we employ a stochastic approach using the Ornstein-Uhlenbeck process with two sources. A Langevin equation is adopted for this explanation. Moreover, comparisons of $dn/dη$ at $\sqrt{s_{NN}} = 130$ GeV with that at $\sqrt{s_{NN}} = 200$ GeV are made, and no significant difference is found. A possible method fot the detection of the quark-gluon plasma (QGP) through $dN_{ch}/dη$ is presented.

nucl-th↗
arXiv2001

Scaling behavior of $(N_{ch})^{-1}dN_{ch}/dη$ at $\sqrt{s_{NN}} = 130$ GeV by PHOBOS Collaboration and its analyses in terms of stochastic approach

Recently interesting data on $dN_{ch}/dη$ in Au-Au collisions ($η=-\ln \tan (θ/2)$) with the centrality cuts have been reported by PHOBOS Collaboration. Their data are usually divided by the number of participants (nucleons) in collisions. Instead of this way, using the total multiplicity $N_{ch} = \int (dN_{ch}/dη)dη$, we find that there is scaling phenomenon among $(N_{ch})^{-1}dN_{ch}/dη= dn/dη$ with different centrality cuts at $\sqrt{s_{NN}} = 130$ GeV. To explain this scaling behavior of $dn/dη$, we consider the stochastic approach called the Ornstein-Uhlenbeck process with two sources. Moreover, comparisons of $dn/dη$ at $\sqrt{s_{NN}} = 130$ GeV with that at $\sqrt{s_{NN}} = 200$ GeV have been made. A possible detection method of the quark-gluon plasma (QGP) thorough $dn/dη$ is presented.

hep-ph↗
arXiv2001

Scintillation efficiency of nuclear recoils in a CaF-2(Eu) crystal for dark matter search

The scintillation efficiency (quenching factor) of fluorine and calcium nuclei recoiling in a CaF-2(Eu) crystal was measured in an energy region relevant to dark matter searches. The recoiling nuclei were obtained via the 19-F(n,n') and 40-Ca(n,n') reactions, where the neutron beam was provided via the d(d,n)3-He reaction. The quenching factor of F and Ca nuclei in the CaF-2(Eu) crystal was found to be 11 ~ 20 %, and 9 ~ 23 % relative to the electron equivalent energy for 53 ~ 192 keV and 25 ~ 91 keV recoil energies, respectively, and the energy dependence was observed. The quenching factor we measured here is a little larger than that of previous studies, which may depend on the Eu doping concentration of the crystal.

nucl-ex↗
arXiv2001

Analyses of multiplicity distributions at Tevatron by a two-component stochastic model --- No leading particle effect in E735 Experiment ---

Comparisons of multiplicity distributions at sqrt(s) = 1.8 TeV (E735 Experiment and CDF Collaboration) with our predictions by a two-component stochastic model have been made. This stochastic model is described by the pure-birth and Poisson processes. It is found that there are discrepancies among data at the CERN Sp-bar-pS collider and those at the Tevatron collider. The latter data by E735 do not contain the leading particle effect described by the Poisson process, providing that the view of the two-component stochastic model is correct. The data by CDF contain small leading particle effect. The reason is probably attributed to the correction made by E735, which is necessary to make the data of the full phase space from the restricted rapidity |eta|<3.25.

hep-ph↗
arXiv2001

Fractional Fokker-Planck Equation and Oscillatory Behavior of Cumulant Moments

The Fokker-Planck equation is considered, which is connected to the birth and death process with immigration by the Poisson transform. The fractional derivative in time variable is introduced into the Fokker-Planck equation. From its solution (the probability density function), the generating function (GF) for the corresponding probability distribution is derived. We consider the case when the GF reduces to that of the negative binomial distribution (NBD), if the fractional derivative is replaced to the ordinary one. Formulas of the factorial moment and the $H_j$ moment are derived from the GF. The $H_j$ moment derived from the GF of the NBD decreases monotonously as the rank j increases. However, the $H_j$ moment derived in our approach oscillates, which is contrasted with the case of the NBD. Calculated $H_j$ moments are compared with those given from the data in $p\bar{p}$ collisions and in $e^+e^-$ collisions.

hep-ph↗
arXiv2001

Fractional Fokker-Planck Equation in Time Variable and Oscillation of Cumulant Moments

Fractional derivative in time variable is introduced into the Fokker-Planck equation of a population growth model. It's solution, the KNO scaling function, is transformed into the generating function for the multiplicity distribution. Formulas of the factorial moment and the $H_j$ moment are derived from the generating function, which reduces to that of the negative binomial distribution (NBD), if the fractional derivative is replaced to the ordinary one. In our approach, oscillation of $H_j$ moment appears contrary to the case of the NBD. Calculated $H_j$ moments are compared with those given from the data in $p\bar{p}$ collisions and in $e^+e^-$ collisions.

hep-ph↗
arXiv2000

Pickoff and spin-conversion quenchings of ortho-positronium in oxygen

The quenching processes of the thermalized ortho-positronium(o-Ps) on an oxygen molecule have been studied by the positron annihilation age-momentum correlation techinique(AMOC). The Doppler broadening spectrum of the 511 keV gamma-rays from the 2gamma annihilation of o-Ps in O_2 has been measured as a function of the o-Ps age. The rate of the quenching, consisting of the pickoff and the spin-conversion, is estimated from the positron lifetime spectrum. The ratio of the pickoff quenching rate to the spin-conversion rate is deduced from the Doppler broadening of the 511 keV gamma-rays from the annihilation of the o-Ps. The pickoff parameter ^1Z_eff, the effective number of the electrons per molecule which contribute to the pickoff quenching, for O_2 is determined to be 0.6 +- 0.4. The cross-section for the elastic spin-conversion quenching is determined to be (1.16 +- 0.01) * 10^{-19} cm^2.

physics.atom-ph↗
arXiv2000

Structural and superconducting transition in selenium under high pressures

First-principles calculations are performed for electronic structures of two high pressure phases of solid selenium, $β$-Po and bcc. Our calculation reproduces well the pressure-induced phase transition from $β$-Po to bcc observed in selenium. The calculated transition pressure is 30 GPa lower than the observed one, but the calculated pressure dependence of the lattice parameters agrees fairly well with the observations in a wide range of pressure. We estimate the superconducting transition temperature $T_{\rm c}$ of both the $β$-Po and the bcc phases by calculating the phonon dispersion and the electron-phonon interaction on the basis of density-functional perturbation theory. The calculated $T_{\rm c}$ shows a characteristic pressure dependence, i.e. it is rather pressure independent in the $β$-Po phase, shows a discontinuous jump at the transition from $β$-Po to bcc, and then decreases rapidly with increasing pressure in the bcc phase.

cond-mat.supr-con↗
arXiv1999

Oscillations of Cumulant Moments - Universality of Amplitudes

We demonstrate on simple examples that oscillatory behaviour of moments of multiplicity distributions P(n) observed in e^+e^- annihilations, in hadronic pp collisions and in collisions on nuclei, p+A, is to a large extend caused by the experimental artifact of measuring only limited range of P(n). In particular we show that by applying a suitable universal cutt-off procedure to the measured P(n) one gets for reactions mentioned before oscillations of similar magnitude. The location of zeros of oscillations as a function of the rank of moments and their shapes remain, however, distinctively different for different types of reactions considered. This applies to some extend also to collisions of nuclei, which otherwise follow their own pattern of behaviour.

hep-ph↗
arXiv1999

Multiplicity dependence of identical particle correlations in the quantum optical approach

Identical particle correlations at fixed multiplicity are consideres in the presence of chaotic and coherent fields. The multiplicity distribution, one-particle momentum density, and two-particle correlation function are obtained based on the diagrammatic representation for cmulants in semi-inclusive events. Our formulation is applied to the analysis of the experimental data on the multiplicity dependence of correlation functions reported by the UA1 and the OPAL Collaborations.

hep-ph↗
arXiv1998

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.

hep-ph↗
arXiv1997

Comparative Analysis of Multiplicity Distributions in Inelastic Processes for Different Colliding Particles and Nuclei

Theoretical prediction of oscillations of cumulant moments of parton multiplicity distributions inside a jet supported by experimental data in some multiple production processes asks for analysis of the phenomenon for the whole set of available reactions. We have found out that the oscillations persist in any kind of processes and increase for particles with more complicated structure i.e. in the order of ee, eh, hh, hA, AA. The effect is not strongly dependent on the available phase space. Theoretical values of moments for quark and gluon jets up to 5th rank are shown. Zeros of the truncated generating function and singularities of the total generating function are discussed.

hep-ph↗
arXiv1997

Wavelet Analyses of High Multiplicity Events

Pseudo-rapidity distributions of high multiplicity JACEE events ( Ca-C, Si-AgBr and G27) and Texas Lone Star (TLS) event are analysed by the wavelet transform method. Using the Daubechies' waveltes, $D_4, D_6, D_8,$ and $ D_{10} $, wavelet spectra of those events are calculated. Two JACEE events are compared with the simulation calculations. We discuss how to distinguish prominent peak from apparent peaks. The wavelet spectrum of Ca-C event seems to resemble that simulated with the Poisson random number distributions. The wavelet spectrum of TLS event shows an oscillatory behavior. It is found that the wavelet spectra of JACEE G27 event are different from those of Arizona group.

hep-ph↗
arXiv1996

Charge Distribution in Soft Chiral Pion Bremsstrahlung

Bremsstrahlung of soft chiral pions in high-energy processes is considered. The distribution over number of neutral and charged pions is shown to obey the inverse square root law. This law is argued to be generic for multiple coherent production of soft chiral pions.

hep-ph↗