Perturbative QCD correction to the B → π transition form factor

We report on the perturbative O(_s) correction to the light-cone QCD sum rule for the B → π transition form factor f⁺. The correction to the product f_Bf⁺ in leading twist approximation is found to be about 30%, that is similar in magnitude to the corresponding O(_s) correction in the two-point sum rule for f_B. The resulting cancellation of large QCD corrections in f⁺ eliminates one important uncertainty in the sum-rule prediction for this form factor.     

The ΔNγ electromagnetic transition form factors GM(q) and GE(q)

A parameter-free, nonperturbative calculation of the ΔNγ electromagnetic transition amplitudes GM*(q2), GE*(q2), and the resonant multipole ratio REM(q2)≡E1+3/2(q2)/M1+3/2(q2) is performed in terms of the well-known nucleon isovector Sachs form factor GMV. Our methods are fully relativistic with conservation of the electromagnetic current guaranteed. We find that GM*(q2) decreases more rapidly than the nucleon dipole form factor when −q21 GeV2/c2 and that REM(q2) remains small even for very high four-momentum transfer implying that the perturbative QCD prediction REM(q2)→1 is purely asymptotic and is valid only for extremely high |q2|.     

Transverse momentum distribution in Drell-Yan pair and W and Z boson production

We exhibit and discuss the QCD prediction for the transverse momentum distribution of W bosons, Z bosons and high-mass virtual photons produced in high-energy hadron-hadron collisions. Recent work has shown that this prediction is consistent with the structure of leading twist initial state interactions.

The expression we present is expected to give results correct up to order _s^N(Q) for any Q_T when the boson mass Q is very large (> 10⁸ GeV!), given only input from perturbative calculations at order _s^N+2 and deeply inelastic scattering structure functions. We specify the required N = 0 coefficients, employing the order _s² results of Kodaira and Trentadue and of Davies and Stirling. We then show how the expression should be modified to deal with current energy scales. We also discuss the connection between low-Q_T and high-Q_T formulae.     

What can we learn from B→DsKπ, Bd→DsKπ and Bd→DsK decays?

We study the nonresonant three-body decays of B⁺→D^(*)−_sK⁺π⁺ and B_d→D_s^(*)−K⁰π⁺. We find that these decays can provide the information on the time-like form factors of D^(*)_sK. We also explicitly investigate B_d→D_s^(*)−K^*+ decays by discriminating the nonresonant contributions with the unknown D^(*)_s wave functions being fixed by the measured mode of B_d→D_s⁻K⁺.     

Remarks on stochastic non-linear birth and death models

The first part of this paper is an attempt to formulate and motivate additional work on the important problem of obtaining global bounds applicable to the controlled truncation of the paper relates specifically to the linear birth, quadratic death model. Asymptotic results are given for the first finite difference ΔT_m where T_m is the exactly known mean time to extinction starting from state m (m= 0,1,…). These results are in terms of the environmental carrying capacity n^* taken to be large. For m near zero ΔT_me^n*/(n^*)²; whereas, for m near n^*ΔT_m ≈ (π/2)^1/2/(n^*)^3/2. This indicates the vastly different time scales in those two regions of state space - with considerably slower action near extinction than near n^*.     

A hybrid mode of one- and two-surface multipactor on grooved dielectric surface

A hybrid mode of one- and two-surface multipactor on the grooved dielectric surface is studied in detail using both an analytical approach and two-dimensional particle-in-cell(2D PIC) simulations. When the groove width L eE_0/(4πm_ef~2),there are one-surface multipactor and one-order two-surface multipactor on the grooved dielectric surface, and only one slope of the groove has the multipactor anytime. When L eE0/(4πme f~2), both slopes may have the multipactors. The electron surface density of the multipactor discharge has a sharp increase at the length L = eE_0/(4πm_ef~2).     

波动方程辛算法的迭代求解

对(∂²)/(∂x²)利用中心差商算子,对expt作对角Padé逼近,由波动偏微分方程可得到两类具有O(Δx²+Δt^2l)和O(Δx⁴+Δt^2l)精度的辛格式.对由此类辛格式产生的线性方程组构造了两种迭代解法,并对l=1,2,3,4给出了它们的收敛条件.并进行了数值实验.     

Froissart bound from gluon saturation

We demonstrate that the dipole–hadron cross-section computed from the non-linear evolution equation for the Colour Glass Condensate saturates the Froissart bound in the case of a fixed coupling and for a small dipole (Q²Λ_QCD²). That is, the cross-section increases as the logarithm squared of the energy, with a proportionality coefficient involving the pion mass and the BFKL intercept (_sN_c/π)4ln2. The pion mass enters via the non-perturbative initial conditions at low energy. The BFKL equation emerges as a limit of the non-linear evolution equation valid in the tail of the hadron wavefunction. We provide a physical picture for the transverse expansion of the hadron with increasing energy, and emphasize the importance of the colour correlations among the saturated gluons in suppressing non-unitary contributions due to long-range Coulomb tails. We present the first calculation of the saturation scale including the impact parameter dependence. We show that the cross-section at high energy exhibits geometric scaling with a different scaling variable as compared to the intermediate energy regime.     

1/f-type fluctuation of electron transmission in one-dimensional disordered systems

A universal feature of 1/f-type fluctuation is numerically observed in the system-size n dependence of the transmission amplitude t_n in various one-dimensional disordered systems. The power spectrum P(f) of the transmission coefficient T(n)=|t_n|² exhibits the power law of 1/f², irrespective to the type of disorder of the system whether it is of short-range or of long-range correlation. That of the phase θ_t(n) of t_n also does the universal power law of 1/f^1.4.     

Neutrino oscillations induced by two-loop radiative mechanism

Two-loop radiative mechanism, when combined with an U(1)_L′ symmetry generated by L_e − L_μ − L_τ (=L′), is shown to provide an estimate of Δm²/Δm²_atm εm_e/m_τ, where ε measures the U(1)_L′-breaking. Since Δm²_atm 3.5×10⁻³ eV², we find that Δm² ε10⁻⁶ eV², which will fall into the allowed region of the LOW solution to the solar neutrino problem for ε 0.1.     

一端附壁高分子链的Monte Carlo研究

采用简立方格点上的Monte Carlo模拟,研究一端被无限大不可穿透平面壁吸附的高分子链的均方末端距<R²>,以及高分子链的质量中心到平面吸附壁的平均距离<Z>,与链长N、参数u(u=e^-ε/kT,ε是链骨架原子间的相互作用能量,k是玻耳兹曼常数,T是热力学温度)的关系。结果表明:<R²>和<Z>都服从标度律,<R²>=αN^γ,<Z>=βN^η,其中,γ、η、α、β都是u的函数;u从1减小到0.5,则γ从1.01增大到1.19,η从0.51增大到0.60.     

Impurity levels of iron-group ions in TiO2(II)

Photocurrent measurements on oxidized, single-crystal TiO₂ undoped and doped with V, Cr, Mn or Fe were made both before and after exposure to white light from a tungsten lamp; they revealed a band of states centered at 2.0 eV below the conduction-band edge E_c that appears to be the band of surface states active in the photoelectrolysis of water. They also revealed a band of bulk states extending from near the valence-band edge E_v to about 1.9 eV below E_c. The ESR signals from V⁴⁺, Cr³⁺ and Fe³⁺ ions in oxidized samples and from Mn³⁺ ions in reduced samples were measured before and after exposure to white and monochromatic light; changes in the ESR signal intensities allow placement of the V⁴⁺: d¹ level about 2.1 eV below E_c, the Cr³⁺: d³ level about 2.7 eV belo E_c, the Fe³⁺ level at or just below the valence band edge E_v which is 3.0 eV below E_c, the Fe²⁺ level approximately at E_c, the Mn³⁺ level about 1.9 eV below E_c. Comparison of experiments on oxidized and reduced samples suggests that the bulk states are associated with cation vacancies, and measurements with polarized light gave anisotropies that are qualitatively interpretable with a cation-vacancy model for the oxidized samples.     

Projective and affine connections on S and integrable systems

It is known that the Korteweg–de Vries (KdV) equation is a geodesic flow of an L² metric on the Bott–Virasoro group. This can also be interpreted as a flow on the space of projective connections on S¹. The space of differential operators Δ⁽ⁿ⁾=∂ⁿ+u₂∂ⁿ⁻²++u_n form the space of extended or generalized projective connections. If a projective connection is factorizable Δ⁽ⁿ⁾=(∂−((n+1)/2−1)p₁)(∂+(n−1)/2p_n) with respect to quasi primary fields p_i’s, then these fields satisfy ∑_i=1ⁿ((n+1)/2−i)p_i=0. In this paper we discuss the factorization of projective connection in terms of affine connections. It is shown that the Burgers equation and derivative non-linear Schrödinger (DNLS) equation or the Kaup–Newell equation is the Euler–Arnold flow on the space of affine connections.     

Ion-size effects on the structure and superconductivity of La-214 compounds at 1/8 doping

A structural transition to a low-temperature tetragonal (TLT) phase occurs below T_d2≈60 K in La_2−xBa_xCuO₄ only around x=0.125, accompanied by sharp suppression of superconductivity. In this study we investigated the effects of partial substitution of smaller divalent cations for Ba²⁺ ions (Ba²⁺ > Sr²⁺ > Ca²⁺) on these anomalous low-temperature properties. The suppression of superconductivity is strongly affected by the appearance of the TLT phase for this carrier concentration. We also show that the variations of T_d2 and T_c are quantitatively scaled by the averaged size of cations at the La site. This dependence can be interpreted as chemical effects acting effectively as applied pressure. We discuss how our observation is related to recent reports which claim that the TLT structure itself does not necessarily destroy the superconductivity.     

Domain-wall supergravities from sphere reduction

Kaluza-Klein sphere reductions of supergravities that admit Ads × Sphere vacuum solutions are believed to be consistent. The examples include the S⁴ and S⁷ reductions of eleven-dimensional supergravity, and the S⁵ reduction of ten-dimensional type IIB supergravity . In this paper we provide evidence that sphere reductions of supergravities that admit instead Domain-wallxSphere vacuum solutions are also consistent, where the background can be viewed as the near-horizon structure of a dilatonic p-brane of the theory. The resulting lower-dimensional theory is a gauged supergravity that admits a domain wall, rather than AdS, as a vacuum solution. We illustrate this consistency by taking the singular limits of certain modulus parameters, for which the originalSⁿ compactifying spheres (n = 4, 5 or 7) becomes S^p × R^q, with p = n − q < n. The consistency of the S⁴, S⁷ reductions then implies the consistency of the ^Sp reductions of the lower-dimensional supergravities. In particular, we obtain explicit non-linear ansätze for the S³ reduction of type IIA and heterotic supergravities, restricting to the U(1)² subgroup of the SO(4) gauge group of S³. We also study the black-hole solutions in the lower-dimensional gauged supergravities with domain-wall backgrounds. We find new domain-wall black holes which are not the singular-modulus limits of the AdS black holes of the original theories, and we obtain their Killing spinors.     

Testing supersymmetry in the associated production of CP-odd and charged Higgs bosons

In the Minimal Supersymmetric Standard Model (MSSM), the masses of the charged Higgs boson (H±) and the CP-odd scalar (A) are related by MH+2=MA2+mW2. Furthermore, because the coupling of W−–A–H+ is fixed by gauge interaction, the tree level production rate of depends only on one supersymmetry parameter—the mass (MA) of A. We show that to a good approximation this conclusion also holds at the one-loop level. Consequently, this process can be used to distinguish MSSM from its alternatives (such as a general two-Higgs-doublet model) by verifying the above mass relation, and to test the prediction of the MSSM on the product of the decay branching ratios of A and H± in terms of only one single parameter—MA.     

Deuteron and neutron structure functions and the effect of relativistic Fermi motion

The deep-inelastic deuteron structure function (SF) F₂^D in the covariant approach in the light-cone variables is considered. The neutron SF F₂ⁿ is extracted from the deuteron and proton experimental data taking into account the relativistic deuteron model and the parametrization of F₂ⁿ is obtained. The effect of the relativistic Fermi motion is estimated to be 6% at x0.7. The extracted neutron SF is used to verify the Gottfried sum rule. It is shown that the violation of the flavour symmetry of the sea can be large with increasing Q².     

Reconciling cold dark matter with COBE/IRAS plus solar and atmospheric neutrino data

We present a model where an unstable MeV Majorana tau neutrino can naturally reconcile the cold dark matter model (CDM) with cosmological observations of large and small scale density fluctuations and, simultaneously, with data on solar and atmospheric neutrinos. The solar neutrino deficit is explained through long wavelength, so-called just-so oscillations involving conversions of ν_e into both ν_μ and a sterile species ν_s , while atmospheric neutrino data are explained through ν_μ to ν_e conversions. Future long baseline neutrino oscillation experiments, as well as some reactor experiments will test this hypothesis. The model is based on the spontaneous violation of a global lepton number symmetry at the weak scale. This symmetry plays a key role in generating the cosmologically required decay of the ν_τ with lifetime τ_ντ ≈ 10²-10⁴ seconds, as well as the masses and oscillations of the three light neutrinos ν_e, ν_μ and ν_s required in order to account for solar and atmospheric neutrino data. It also leads to the invisibly decaying Higgs signature that can be searched at LEP and future particle colliders.     

A new two-mode thermo- and squeezing-mixed optical field

We propose a new two-mode thermo-and squeezing-mixed optical field, described by the new density operator ρ=1-e~f-|g|~2 e~(ga~+b~+)e~(fa~+a)|0〉 f_(bb) 〈0| e~(g*ab), where |0〉_(bb) 〈0| is the b-mode vacuum, e ~(fa~+a)represents the thermo-field, and e~(ga~+b~+) indicates squeezing. The photon statistics for ρ is studied by virtue of the method of integration within ordered product(IWOP) of operators. Such a field can be generated when a two-mode squeezed state passes through a one-mode dissipation channel.     

Analytical result for dimensionally regularized massless master non-planar double box with one-leg off shell

The dimensionally regularized massless non-planar double box Feynman diagram with powers of propagators equal to one, one leg off the mass shell, i.e., with p₁²=q²≠0, and three legs on shell, p_i²=0, i=2,3,4, is analytically calculated for general values of q² and the Mandelstam variables s,t and u (not necessarily restricted by the physical condition s+t+u=q²). An explicit result is expressed through (generalized) polylogarithms, up to the fourth order, dependent on rational combinations of q²,s,t and u, and simple finite two- and three-fold Mellin–Barnes integrals of products of gamma functions which are easily numerically evaluated for arbitrary non-zero values of the arguments.