Scalar quark mass splitting effects in lepton-proton interactions

The mass splitting of scalar quarks of the same flavour leads to parity violation in deep inelastic scattering, even at one photon exchange level. This effect modifies the asymmetries measured in the polarized lepton-proton scattering. We calculate them in leading order and give numerical estimates of their shapes.     

The role of instantons in generation of mesonic mass spectrum

It is suggested that instantons play the leading role in the mixing of $\text{s}\text{s and}\text{u}\text{u}\text{+}\text{d}\text{d}$ quark states in mesonic nonets and in the explanation of the Okubo-Zweig-Iizuka (OZI) rule. The non-diagonal polarization operator Π^su = 〈0|T{j^s(x)j^u(y)}0〉 is considered where $\text{j}{}^{\mathrm{<mtext>s</mtext>}}\text{=}\text{s}\text{O}\text{s}$ and $\text{j}{}^{\mathrm{<mtext>u</mtext>}}\text{=}\text{u}\text{O}\text{u}$ are the currents of the s and u quarks. It is proved that in the dilute instanton gas approximation for quarks in the external instanton field Π^su = 0 for the vector and tensor currents and Π^su≠0 for the axial current. Hence, after saturating Π^su by the low-lying mesonic states, we obtain the qualitative explanation of the OZI rule. The Q² dependence of the non-diagonal polarization operator of the axial currents, Π^su(Q²), is calculated and compared with the η′ meson pole term. Taking account of terms ～m_q² allows one, using the experimentally known ηη′ mixing angle, to find the η′ meson coupling constant with the axial current F_η′ ≈ 150 MeV and to estimate the η′π mixing angle.     

再论质量的起源

物质的质量是怎么来的？能从理论上研究质量的起源吗? 人类目前所能做的实验是否到了可探索这些质量起源的程度? 本文将要介绍目前物理学对这些问题的认识.我们首先通过修改牛顿第零定律引入结合能来介绍物质的各个不同层次上的质量起源的研究链条,然后重点讨论基本粒子质量的起源,并介绍基本粒子质量与对称性的关系,最后讨论三种与质量起源有关的质量产生和分裂的机制.     

On the total mass of closed universes

The total mass, the Witten type gauge conditions and the spectral properties of the Sen–Witten and the 3-surface twistor operators in closed universes are investigated. It has been proven that a recently suggested expression $\mathtt{M}$ M for the total mass density of closed universes is vanishing if and only if the spacetime is flat with toroidal spatial topology; it coincides with the first eigenvalue of the Sen–Witten operator; and it is vanishing if and only if Witten’s gauge condition admits a non-trivial solution. Here we generalize slightly the result above on the zero-mass configurations: $\mathtt{M}=0$ M = 0 if and only if the spacetime is holonomically trivial with toroidal spatial topology. Also, we show that the multiplicity of the eigenvalues of the (square of the) Sen–Witten operator is even, and a potentially viable gauge condition is suggested. The monotonicity properties of $\mathtt{M}$ M through the examples of closed Bianchi I and IX cosmological spacetimes are also discussed. A potential spectral characterization of these cosmological spacetimes, in terms of the spectrum of the Riemannian Dirac operator and the Sen–Witten and the 3-surface twistor operators, is also indicated.     

Instanton effects on the interaction potential between light quarks and the isomultiplet mass splitting of baryons

On the basis of current assumptions of instanton theory we derive strictly the explicit dependence on the masses and spins of the instanton induced potential between a pair of light quarks in baryons, namelyV ₁₂=γ+β(m _* ^1+α )(m _* ^2+α )η(1-σ ₁ησ ₁), wherem _i ^* andσ _i (i=1.2) are respectively the mass and Pauli spin of theith quark. On the additional basis of the MIT bag model, we obtain γ=c/R ³ and β=b/R ³>0, and α>0 is independent of the radiusR of the baryon. The magnitudes of the parametersb and α are also estimated. The MIT bag model is improved by taking into account this potential. Isomultiplet mass splitting formulas are derived in good agreement with experiment.     

Edison revisited: Electro mechanical effects in wet porous materials

Edison discovered that the coefficient of friction between a metallic plate and a porous material moistened with a dilute electrolyte could be modulated by an electric field. In experiments on the same kind of contacts (clays or chalks on carbon or metals) but without continuous tangential relative motion we measure two electro-mechanical effects at frequencies of the order of 10 kHz. An alternating field induces an alternating normal force between the porous material and the conducting base. The force is lagging by versus the field. A forced normal relative motion induces through the contact a current nearly in phase with the motion. For an explanation we start from Helmholtz theory of stationary electrophoretic phenomena. We present a model in which liquid motions obey the Helmholtz laws. It explains decently the phase relations between causes and effects, and approximately the values of the effects. In optical experiments on contacts between a wet clay and the transparent conducting coating of a glass plate we measure in the frequency range 1-100 kHz a modulation of reflecting power induced by an alternating potential. The decrease of reflecting power is lagging by an angle close to behind the field. We think the modulation observed is induced by a modulation of the amount of liquid in the film present between glass and clay. In friction experiments this alternating liquid lubrication acting exclusively at the very places where friction occurs may have significant effect. Received: 22 July 1997 / Revised: 21 October 1997 / Accepted: 21 November 1997     

Thin nematic films: Anchoring effects and stripe instability revisited

We study theoretically the formation of long-wavelength instability patterns observed at spreading of nematic droplets on liquid substrates. The role of surface-like elastic terms in nematic films of submicron thickness is (re)examined by extending our previous work to hybrid aligned nematics. We identify the upper threshold for the formation of stripes and compare our results with experimental observations. We find that the wavelength and the amplitude of the in-plane director undulations can be related to the small but finite azimuthal anchoring. Within a simplified model we analyse the possibility of non-planar base state below the Barbero–Barberi critical thickness.     

A note on the mass splitting of K*(892)

Belle Collaboration reported a new observed value of K*-(892) mass by studying τ- → KSπ-ντ decay, which is significantly different from the current world average value given by Particle Data Group 2006. Motivated by this new data, we revisit the issue on the K*0(892)-K*±(892) mass splitting. Our theoretical estimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues.     

Measurement of the neutrino mass splitting and flavor mixing by MINOS

Measurements of neutrino oscillations using the disappearance of muon neutrinos from the Fermilab NuMI neutrino beam as observed by the two MINOS detectors are reported. New analysis methods have been applied to an enlarged data sample from an exposure of 7.25×10(20) protons on target. A fit to neutrino oscillations yields values of |Δm(2)|=(2.32(-0.08)(+0.12))×10(-3) eV(2) for the atmospheric mass splitting and sin(2)(2θ)>0.90 (90% C.L.) for the mixing angle. Pure neutrino decay and quantum decoherence hypotheses are excluded at 7 and 9 standard deviations, respectively.     

A note on the mass splitting of K*(892)

Belle Collaboration reported a new observed value of K*-(892) mass by studying τ- → Ksπ-γτ decay, which is significantly different from the current world average value given by Particle Data Group 2006.Motivated by this new data, we revisit the issue on the K*0(892)-K*±(892) mass splitting. Our theoreticalestimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues.     

Optimal channels of the Garvey-Kelson mass relations in extrapolation

Garvey-Kelson mass relations connect nuclear masses of neighboring nuclei within high accuracy, and provide us with convenient tools in predicting unknown masses by extrapolations from existent experimental data. In this paper we investigate optimalchannels of the Garvey-Kelson relations in extrapolation to the unknown regions, and tabulate our predicted masses by using these optimized channels of the Garvey-Kelson relations.     

Recoil and strong formfactor effects in mesonic exchange corrections on the charge distribution of 3He and 3H

Effects of meson exchange on the charge distribution of ³He and ³H are determined, including intermediate nucleon-antinucleon states, pion-nucleon resonances and recoil effects. The role of a strong interaction formfactor in these effects is discussed. The calculation is based on a tri-nucleon wavefunction obtained from the Reid soft core potential.     

Raman scattering studies of individual polar semiconducting nanowires: phonon splitting and antenna effects

Results from Raman scattering experiments on individual crystalline GaP nanowires are presented which indicate that the shape of the nanowire, i.e., the high aspect ratio, may be responsible for two new phenomena involving optical phonons: (1) a shape-inducedsplitting of both the longitudinal optical (LO) and transverse optical (TO) phonons at the center of the Brillouin zone (q=0), and (2) a Raman scattering “antenna” effect which masks the normal Raman polarization selection rules. We suggest that (1) stems from the asymmetry in the long range dipolar sums that control the electromagnetic LO-TOsplitting, and we identify the Raman antenna effect (2) with the internal electric field created by Mie resonances in the nanowire driven by the incident laser field. Although these effects are reported here for GaP, they are expected to be general effects observable in many semiconducting nanowire systems. PACS 78.67.-n; 78.67.Lt; 78.30.-j; 78.30.Fs; 72.10.Di     

$J/\psi$ gluonic dissociation revisited: II. Hydrodynamic expansion effects

We explicitly take into account the effect of the hydrodynamic expansion profile on the gluonic break-up of the 's produced in an equilibrating parton plasma. Attention is paid to the space-time inhomogeneities as well as Lorentz frames while deriving new expressions for the gluon number density n_g, the average dissociation rate , and the survival probability of , S. A novel type of partial wave interference mechanism is found to operate in the formula of . A non-relativistic longitudinal expansion from the small length of the initial cylinder is found to push the S(p_T) graph above the no flow case considered by us earlier [9]. However, the relativistic flow corresponding to the large length of the initial cylinder pushes the curve of S(p_T) downwards at LHC but upwards at RHIC. This mutually different effect on S(p_T) may be attributed to the different initial temperatures generated at LHC and RHIC. Received: 16 March 2005, Published online: 27 September 2005 PACS: 12.38.Mh     

Band-gap problem in semiconductors revisited: effects of core states and many-body self-consistency

A novel picture of the quasiparticle (QP) gap in prototype semiconductors Si and Ge emerges from an analysis based on all-electron, self-consistent, GW calculations. The deep-core electrons are shown to play a key role via the exchange diagram-if this effect is neglected, Si becomes a semimetal. Contrary to current lore, the Ge 3d semicore states (e.g., their polarization) have no impact on the GW gap. Self-consistency improves the calculated gaps-a first clear-cut success story for the Baym-Kadanoff method in the study of real-materials spectroscopy; it also has a significant impact on the QP lifetimes. Our results embody a new paradigm for ab initio QP theory.     

Isospin splitting of nucleon effective mass and symmetry energy in isotopic nuclear reactions

Within an isospin and momentum dependent transport model, the dynamics of isospin particles(nucleons and light clusters) in Fermi-energy heavy-ion collisions are investigated for constraining the isospin splitting of nucleon effective mass and the symmetry energy at subsaturation densities. The impacts of the isoscalar and isovector parts of the momentum dependent interaction on the emissions of isospin particles are explored, i.e., the mass splittings of m_n~*=m_p~* and m_n~* m_p~*(m_n~* m_p~*). The single and double neutron to proton ratios of free nucleons and light particles are thoroughly investigated in the isotopic nuclear reactions of ~(112)Sn+~(112)Sn and ~(124)Sn+~(124)Sn at incident energies of 50 and 120 MeV/nucleon, respectively. It is found that both the effective mass splitting and symmetry energy impact the kinetic energy spectra of the single ratios, in particular at the high energy tail(larger than 20 Me V). The isospin splitting of nucleon effective mass slightly impacts the double ratio spectra at the energy of 50 MeV/nucleon. A soft symmetry energy with stiffness coefficient of γ_s =0.5 is constrained from the experimental data with the Fermi-energy heavy-ion collisions.