Numerical simulation tests with light dynamical quarks

Two degenerate flavors of quarks are simulated with small masses down to about one fifth of the strange quark mass by using the two-step multi-boson (TSMB) algorithm. The lattice size is with lattice spacing about which is not far from the N _t =4 thermodynamical cross-over line. Autocorrelations of different physical quantities are estimated as a function of the quark mass. The eigenvalue spectra of the Wilson-Dirac operator are investigated. Received: 20 June 2002 / Revised version: 30 August 2002 / Published online: 25 October 2002     

Chiral Symmetry,Ward-Takahashi Identities and Mass Spectra in (2+1) Dimensional Chiral Gross-Neveu Model

Chiral Ward-Takahashi identities with composite fields are applied to investigate mass spectra in (2+1) dimensional chiral Gross-Neveu model.The fermion mass and bound state spectra are obtained,which are in agreement with large-N expansion in the lowest approximation.When the chiral symmetry is an approximate one,we obtain the PCAC.     

Path Integral Formulation for Chern-Simons Quantum Mechanics

Chern-Simons quantum mechanics is studied by using the path integral formulation. We find that the model can be decomposed into two independent oscillators when a set of new coordinate is chosen. The propagator is constructed in this new set of coordinate and the spectra is read off directly from it. The spectra will be divergent when the mass of the particle tends to zero. In order to get a physical result, one must regularize the spectra properly. We afford a new scheme of regularization. Interestingly, our scheme shows that the regularization we proposed amounts to erase one of the oscillators in the new set of coordinate. Physical interpretations for the regularization are given and some ambiguities in the literatures are clarified.     

基于FT-ICR质谱仪的光解离光谱自动化谱图采集程序的开发与应用

光解离光谱在气相离子结构及动力学研究中发挥着重要的作用。这种方法非常灵活,可在实验室中利用不同种类的激光器及质谱仪的结合来开展相应的研究。但也存在一些问题,例如,自动化水平低,费时,长时间的操作容易引入人为错误,使实验结果的可信度降低。为解决此类问题,该工作开发了一套可用于光谱自动采集和分析的程序AutoMS。该程序包含:(1)AutoSpecMS用于在无需改变原仪器配套的商业化操作软件的前提下,实现多台商业激光器及一台商业高分辨FT-ICR质谱仪的集成,只需要预设参数即可自动获取action光谱;(2)AutoDataMS用于实验数据的分析,可以通过一维、二维或三维图示的方法来展示光解离质谱和光谱等。为验证改程序的可行性,针对tetraphenylpyrrin(四苯基卟啉,TPP), tetra(4-carboxypyryl)porphyrin(四对羧基苯基卟啉,TCPP)以及tetra(4-aminophenyl)porphyrin(四对氨基苯基卟啉,TCPP)三种卟啉衍生物分别开展了相应的实验。使用光解离光谱自动采集程序采集了TPP, TCPP和TAPP在210～700 nm波段...     

SOME CONJECTURES ON LEPAONIC AND STRATON'IC SPECTRA

In this note the spectra of leptons and stratons are conjectured and some interes-ting results are obtained:If the number of the generations of leptons are four,then the next lepton mass is about 4.2 GeV,and if the number of the leptons are five,then the fourth lepton mass is about 5.6 GeV.For stratons,if the number of flavour is six,then the mass of the meson with(tt)as a bound state is about 15 GeV,and if the number of flavour is eight,then it is about 23 GeV.     

Exact Solutions of the Klein–Gordon Equation with Position-Dependent Mass for Mixed Vector and Scalar Kink-Like Potentials

The relativistic problem of spinless particles with position-dependent mass subject to kink-like potentials (~tanh αx) is investigated. By using the basic concepts of the supersymmetric quantum mechanics formalism and the functional analysis method, we solve exactly the position-dependent effective mass Klein–Gordon equation with the vector and scalar kink-like potential coupling, and obtain the bound state solutions in the closed form. It is found that in the presence of position-dependent mass there exists the symmetry that the discrete positive energy spectra and negative energy spectra are symmetric about zero energy for the case of a mixed vector and scalar kink-like potential coupling, and in the presence of constant mass this symmetry only appears for the cases of a pure scalar kink-like potential coupling or massless particles.     

Characteristics of nitrogen-incorporated silicon oxycarbide films and plasmas for plasma enhanced chemical vapor deposition with TMOS/N2/NH3

Plasma enhanced chemical vapor deposition of nitrogen-incorporated silicon oxycarbide thin films obtained from the gas mixture of TMOS (tetramethoxysilane), N₂, and NH₃ is studied. The effects of the TMOS to N₂ pressure ratio on the properties of the film and the plasma are investigated. The deposited films are analyzed by in situ ellipsometry, ex situ Fourier transform infrared spectroscopy (FTIR), and by X-ray photoelectron spectroscopy (XPS). The plasma is characterized by using optical emission spectroscopy (OES). The mass spectra of the constituents in the plasma are obtained by quadrupole mass spectroscopy. The correlation between the film properties and the plasma characteristics is explained wherever possible. As the partial pressure of N₂ is decreased, the refractive index begins to decrease, reaches a minimum, and then saturates. The FTIR absorption bands are observed from about 850 to 1000 cm⁻¹ and from 1000 to 1250 cm⁻¹, and can be attributed to the formation of a nitrogen-incorporated silicon oxycarbide thin film. The variation of the refractive index is discussed in relationship with the deposition rate, the OES spectra, the mass spectra of the plasma, the film composition obtained by XPS, and FTIR spectra.     

Identification of baryon resonances in central heavy-ion collisions at energies between 1 and 2 AGeV

The mass distributions of baryon resonances populated in near-central collisions of Au on Au and Ni on Ni are deduced by defolding the p_t spectra of charged pions by a method which does not depend on a specific resonance shape. In addition the mass distributions of resonances are obtained from the invariant masses of (p, π^±) pairs. With both methods the deduced mass distributions are shifted by an average value of −60 MeV/c² relative to the mass distribution of the free Δ(1232) resonance, the distributions descent almost exponentially towards mass values of 2000 MeV/c². The observed differences between (p, π⁻) and (p, π⁺) pairs indicate a contribution of isospin I = 1/2 resonances. The attempt to consistently describe the deduced mass distributions and the reconstructed kinetic energy spectra of the resonances leads to new insights about the freeze out conditions, i.e. to rather low temperatures and large expansion velocities. Received: 26 June 1998 / Revised version: 2 September 1998     

Fast electrostatic sweep of a mass spectrum in permanent-magnet mass spectrometers

As was shown earlier [1], in a permanent-magnet mass spectrometer, one can record mass spectra in a considerably wide range of mass numbers by using several specially arranged collectors. This scheme is easy to implement in magnetic mass analyzers with an angle of rotation other than 180°.     

Determining a 'safe' high-mass limit in matrix-assisted laser desorption/ionisation time-of-flight mass spectra of coal derived materials with reference to instrument noise

Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Mass spectra of dual strings

Dual strings seem to correspond uniquely to certain subgroups of the modular group. From three axioms, one of which is a tentative simplicity assumption, a finite number of possible mass spectra is derived, but not yet the corresponding amplitudes. Above space-time dimension 8, this approach yields just the mass spectra of the known models, plus one additional candidate for 10 dimensions. Further models exist probably for dimensions 8, 6, and 4, and perhaps for dimensions 5 and 3. The mass spectrum of one candidate for the “correct model” is determined. It yields only mesons of charge zero, but otherwise the agreement with experiment is amazing.     

Mass spectra of meson molecular states for heavy and light sectors

We obtain mass spectra of the light and heavy meson-antimeson(molecular states) sectors by using a nonrelativistic potential model with Coulomb and one pion exchange potential terms for meson-meson interaction.The digamma decay widths are also obtained for the light sector.We compare our results with available experimental and theoretical data.     

Physical Features of Binary Coulomb Crystals: Madelung Energy,Collective Modes and Phonon Heat Capacity

Electrostatic energy, collective modes, and thermodynamic functions of a Coulomb crystal with equal number of ions of two different types and uniform charge‐compensating electron background are studied using harmonic lattice model. Simple cubic and hexagonal lattices with two different ions in the elementary cell (we denote these lattices sc2 and h2, respectively) are considered. The static sc2 lattice is more tightly bound than the h2 one at any charge ratio of the constituent ions. The phonon spectra depend on the ion charge and mass ratio. An analysis shows that these binary Coulomb crystals are stable, if the charge ratio is not too different from 1 (about 3.6 for sc2 and 1.3 for h2 lattices) regardless of the mass ratio. Heat capacity of the sc2 lattice is obtained by numerical integration over the first Brillouin zone as a function of temperature and charge and mass ratios. Well known classic and quantum asymptotes of the heat capacity are reproduced, and the dependence of the coefficient in the Debye T³ law on charge and mass ratios is presented (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

碘化铯分子的光离解及生成物铯原子的共振电离研究

利用脉冲激光束与分子的相互作用，对ＣｓＩ分子进行了光离解。同时，用另一束可调谐激光对ＣｓＩ分子离解后产生的中性铯原子进行共振激发，然后把处在激发态的铯原子进行光电离。对Ｃｓ＋的飞行时间质谱进行了分析，并对光离解及光电离过程中可能存在的多光子电离（ＭＰＩ）进行了讨论。     

Experimental signature of medium modifications for rho and omega mesons in the 12 GeV p+A reactions

The invariant mass spectra of e+e- pairs produced in 12 GeV proton-induced nuclear reactions are measured at the KEK Proton Synchrotron. On the low-mass side of the meson peak, a significant enhancement over the known hadronic sources has been observed. The mass spectra, including the excess, are well reproduced by a model that takes into account the density dependence of the vector meson mass modification, as theoretically predicted.     

Cold nuclear matter effects on dijet productions in relativistic heavy-ion reactions at LHC

We investigate the cold nuclear matter (CNM) effects on dijet productions in high-energy nuclear collisions at LHC with the next-to-leading order perturbative QCD. The nuclear modifications for dijet angular distributions, dijet invariant mass spectra, dijet transverse momentum spectra and dijet momentum imbalance due to CNM effects are calculated by incorporating EPS, EKS, HKN and DS parametrization sets of parton distributions in nucleus. It is found that dijet angular distributions and dijet momentum imbalance are insensitive to the initial-state CNM effects and thus provide optimal tools to study the final-state hot QGP effects such as jet quenching. On the other hand, the invariant mass spectra and the transverse momentum spectra of dijet are generally enhanced in a wide region of the invariant mass or transverse momentum due to CNM effects with a feature opposite to the expected suppression because of the final-state parton energy loss effect in the QGP. The difference of EPS, EKS, HKN and DS parametrization sets of nuclear parton distribution functions is appreciable for dijet invariant mass spectra and transverse momentum spectra at p+Pb collisions, and becomes more pronounced for those at Pb+Pb reactions.     

Reaction mechanisms for two-neutron halo breakup

We describe a reaction mechanism which is consistent with all available experimental information of high energy three-body breakup processes. The dominating channels are removal of one of the three halo particles leaving the other two either undisturbed or absorbed. We compare with the commonly used deceptive assumption of a decay through two-body resonance states. Our predictions can be tested by measuring neutron-neutron invariant mass spectra.     

基于模糊聚类算法的大气粒子激光电离质谱数据分析

实验室自行研制了一台大气气溶胶飞行时间激光质谱仪(ATOFLMS),它可以在线地对气溶胶单粒子进行物理和化学特性分析,利用双束连续激光对单个粒子的空气动力学粒径进行测量,并通过飞行时间完成单粒子化学成分的检测。该仪器在运行过程中将产生海量的实验数据,对这些数据的快速、自动处理并提取有价值的信息是整机系统的关键之一。文章介绍模糊聚类算法FCM(fuzzy c-means)在大气气溶胶单粒子聚类分析中的成功运用。利用该算法对连续24 h采集的室内空气气溶胶单粒子质谱数据进行了聚类分析,在得到的5个聚类结果中包含了无机的海盐粒子、矿物质粒子以及其他的三种二次气溶胶成分粒子类型。在对室内空气气溶胶粒子的粒径进行实时检测的结果表明室内可吸入颗粒物以细粒子为主,其中大于1 μm的粒子所占比重较小。小于1 μm的粒子均占95％以上, 在0.4～0.8 μm之间的粒子占据主要部分。     

Neutrino masses

A status report about experimental searches for neutrino masses is given. Direct mass experiments for the three different neutrino flavours are discussed. Under the assumption of neutrino mixing results of experiments looking for neutrino decay and distortions in spectra of weak decays are reported.     

Event patterns from negative pion spectra in proton-proton and nucleus-nucleus collisions at SPS

Rapidity-dependent transverse momentum spectra of negatively charged pions measured at different rapidities in proton-proton collisions at the Super Proton Synchrotron(SPS) at various energies within its Beam Energy Scan(BES) program are investigated by using one-and two-component standard distributions where the chemical potential and spin property of particles are implemented. The rapidity spectra are described by a doubleGaussian distribution. At the stage of kinetic freeze-out, the event patterns are structured by the scatter plots in the three-dimensional subspaces of velocity, momentum and rapidity. The results of the studies of the rapidityindependent transverse mass spectra measured at mid-rapidity in proton-proton collisions are compared with those based on the similar transverse mass spectra measured in the most central beryllium-beryllium, argon-scandium and lead-lead collisions from the SPS at its BES energies.