B→ηlν decays and the flavor-singlet form factors

We study semileptonic decays B→η^(′)lν, taking into account the flavor-singlet contribution (F^singlet₊) to the B→η^(′) form factors, which arises from the two-gluon emission in a decaying B meson. It has been recently pointed out that, in addition to large weak annihilation effects, the unknown value of F^singlet₊ prevents accurate theoretical estimates in the analysis of B→η′K decays in QCD factorization. We present a certain method to determine F^singlet₊ with a reasonable accuracy, using B→η^(′)lν and B→πlν decays. We also investigate the possible effect of F^singlet₊ on the estimated branching ratios (BRs) for B→η^(′)lν and find that the BR for B→η′lν is particularly sensitive to the effect of F^singlet₊.     

Multivortex states in large pinning centers

We have studied the vortex pinning in the large centers, i.e. in the spatial regions with the characteristic size a comparable with the London lenght λ. It is shown that the type of configuration and the number of vortices in the cluster are dependent on the ration a/λ and change nonmonotonically with the temperature. The influence of such vortex clusters on the decay of magnetization and the current-voltage characteristics are discussed. The important role of the potential barrier for the penetration of vortices into the pinning center is shown. The new state of vortex cluster, “vortex polaron”, is predicted. The stability of the multivortex state is discussed.     

Duality and quantum-algebra symmetry of the AN−1 open spin chain with diagonal boundary fields

We show that the transfer matrix of the A_N−1⁽¹⁾ open spin chair with diagonal boundary fields has the symmetry U_q(SU(l)) × U_q(SU(N−l)) × U(1), as well as a “duality” symmetry which maps l ↔ N − l. We exploit these symmetries to compute exact boundary S-matrices in the regime with q real.     

Same-sign dileptons as a signature for heavy Majorana neutrinos in hadron-hadron collisions

We discuss the possibility of same-sign dileptons as a signature for Majorana neutrinos. The production mechanism is given by a single heavy neutrino production and decay pp → l^±NX → l^±l^±X′. Cross section and distributions are presented for the LHC energies.     

On the pp → ppη(η′) reactions near threshold

The production rate for η′ in pp → ppη′ at rest is calculated in a covariant one boson exchange model, previously applied to study π⁰ and η production in NN collisions. The transition amplitudes for the elementary BN → η′N processes with B being the meson exchanged (B = π, σ, η, , ω and a₀) are taken to be the sum of s- and u-channels with a nucleon in the intermediate states, and an a₀ meson pole in a t-channel. The couplings of the η′ to hadrons are a factor 0.4 weaker than the respective η-hadron couplings, as suggested by a quark model and a singlet-octet mixing angle θ = −23°. The model reproduces near threshold cross sections for the quasielastic processes π⁻p → nη(η′) and pp → ppη(η′) reactions.     

Statistical approach of the effects of roughness on the polarization of light scattered by dust grains

In order to study the effect of shape on the optical properties of dust grains, we statistically analyze the linear polarized scattered light. We start by examining a homogeneous spherical grain using the discrete dipole approximation (DDA) Draine (Astrophys J 1988;333:848). Using a uniform law we remove elements of matter on the surface of the grain to describe a random roughness. Then, for various scattering angles, the linear polarization P_l is calculated. We successively repeat the simulation in order to obtain a sample of random variables constituting the values P_l of the linear polarization. The analysis of the results is then achieved through a Gaussian kernel method which provides the probability density function of P_l for each scattering angle. We present the results for a typical interstellar grain of water–ice with radius a comparable to the incident wavelength λ so that the parameter size x≡2πa/λ1. We apply this method for two wavelengths in the near IR, when water–ice is transparent at 1.9 μm, and, when water–ice is absorbing at 3.1 μm. We find that the shape of the density function of the linear polarization is asymmetric to the mean value of the density function and non-unimodal for several scattering angles. This allows us to separate the effects of roughness from those of volume. When water–ice is absorbing, we also observe a significant shift of the polarization peak toward greater scattering angles.     

Neutrino masses, muon g−2, and lepton-flavour violation in the supersymmetric see-saw model

In the light of the recent muon (g_μ−2) result by the E821 experiment at the Brookhaven National Laboratory, we study the event rates of the charged lepton-flavour-violating (LFV) processes in the supersymmetric standard model (SUSY SM) with the heavy right-handed neutrinos (SUSY see-saw model). Since the left-handed sleptons get the LFV masses via the neutrino Yukawa interaction in this model, the event rate of μ→eγ and the SUSY-SM correction to (g_μ−2)/2 (δa_μ^SUSY) are strongly correlated. When the left-handed sleptons have a LFV mass between the first and second generations ( ) in the mass matrix, it should be suppressed by 10⁻³ (10⁻⁹/δa_μ^SUSY) compared with the diagonal components (m_SUSY²), from the current experimental bound on μ→eγ. The recent (g_μ−2) result indicates δa_μ^SUSY10⁻⁹. The future charged LFV experiments could cover . These experiments will give a significant impact on the flavour models and the SUSY-breaking models. In the SUSY see-saw model is proportional to square of the tau-neutrino Yukawa-coupling constant. In the typical models where the neutrino-oscillation results are explained and the top-quark and tau-neutrino Yukawa couplings are unified at the GUT scale, a large LFV mass of is generated, and the large LFV event rates are predicted. We impose a so-called no-scale condition for the SUSY-breaking parameters at the GUT scale, which suppresses the FCNC processes, and derive the conservative lower bound on μ→eγ. The predicted Br(μ→eγ) could be covered at the future LFV experiments.     

Measurement of apex angle of the prism using total internal reflection

Total internal reflection technique is examined critically for the measurement of apex angle of the prism. Recognition of the critical boundary completely specifies the apex angle ‘A’ of the prism by keeping constant the ratio of refractive index of sample fluid (n₁=1.4) to that of glass (n₂=1.7). Recording of observations in the laboratory is dependent upon whether the apex angle ‘A’ of prism is greater than or less than or equal to critical angle ‘r_c’. The minimum value of error function ‘χ’ in the proximity of Abbe angle explain the choice of Abbe type instruments and shown invariant by relating positive ‘₊’ and the negative angle of emergence ‘₋’. Using ray-tracing technique, an expression for the length of the critical boundary ‘l’ is derived and is shown as a measure of the apex angle ‘A’ of the prism.

The choice of the realistic grazing condition leads us to two turning points for which error function ‘χ’ is minimal and yields appropriate option of the measurement of apex angle ‘A’ of the prism. It is further shown that the small error ‘ζ’ crept in the apex angle ‘A’ of the prism can lead to a significant error in the design of Pulfrich type instruments.

Experimental measurements are in-line with the predictions made.     

Wγγ production as a test of three- and four-gauge-boson couplings at LHC and SSC

The reaction pp→W^±γγX is considered at centre-of-mass energies √s = 16 and 40 TeV, including anomalous three- and four- gauge-boson couplings κ and λ. Limits are obtained on these quantities by comparison with the standard model.     

A 62 K superconductor with an original structure: Sr4−xBaxTlCu2CO3O7

A new superconductor with an original structure, Sr_4−xBa_xTlCu₂CO₃O₇ has been isolated for 1≤x≤2. It crystallizes in a A-type space group with a=3.84 Å≈a_p, b≈8 × a_p, c≈17.0 Å. The HREM study of this new curprate shows that it derives from the Tl_0.5Pb_0.5Sr₄Cu₂CO₃O₇ structure by a shearing mechanism. Indeed, it can be described as ribbons of the latter structure, four octahedra thick, shifted c/2 with respect to each other. It results in infinite single perovskite layers waving along the (001) plane and connected through flat mixed layers [(TIO)₄(CO)₄]∞. This oxycarbonate can also be described as a 1201-type structure in which the [TIO]∞ layers are replaced by mixed [(TIO)₄(CO)₄]∞ layers. The susceptibility measurements show that this cuprate exhibits a significantly higher critical temperature than the 1201-cuprates. The T_{c onset} of the synthesized phase is 56 K and it can be increased up to 62 K by hydrogen annealing; in the same way, one observes a large Meissner volume fraction of 35% at 4.2 K.     

Temperature dependence of the dielectric properties of SBN in the frequency range of 10kHz–10MHz

The dielectric constant of Sr_0.75 Ba_0.25 Nb₂O₆ and its dielectric loss have been measured from -20°C to +90°C at various frequencies in the range of 10 KHz– 10 MHz. The result show, that despite the low half-wave field distance product (E·l)λ/2, the use for light modulation purposes is limited because of the high value of tan σ.     

Phase segregation of LixMn2O4 (0.6<x<1) in non-equilibrium reduction processes

Chemical synthesis routes to Li_xMn₂O₄ (0.15≤x≤1) in non-equilibrium reduction processes were developed to carry out detailed structural analysis. Non-equilibrium Li_xMn₂O₄ (0.15≤x≤1) samples were prepared by chemical lithiation of λ-MnO₂ with LiI for 24 h; longer than 1 week was needed to reach true equilibrium at room temperature. The samples were characterized by X-ray diffraction analysis. The phase diagram was different from that in the equilibrium state; three cubic phases (phases A, B and C) were observed for Li_xMn₂O₄ (0.15≤x≤1). There were two regions of two-phase coexistence: the region of 0.25<x<0.55 (phase B+phase C) and 0.6<x<1.0 (phase A+phase B). In the compositional range of 0.6<x<1.0, the lattice constants of phases A and B change with the lithium composition, this indicates that it is a structural anomaly with a metastable two-phase character in non-equilibrium reduction processes.     

Scaling properties of eden clusters in three and four dimensions

We study the scaling properties of noise reduced Eden clusters in three and four dimensions for variant B in the strip geometry. We find that the width W for large times behaves as a(s)g(L/s^d−1), where L is the width of the strip, s the noise reduction parameter, d the dimension of space, and a(s) a decreasing function of s, g is a scaling function with the property g(u)→1/2 as u→0 and g(u)u^x as u→∞, where χ is the roughness exponent. This scaling result leads to a new way of determining χ. In 3 dimensions, our numerical values for χ support a recent conjecture by Kim and Kosterlitz: χ = 2/(d + 2), and contradict all the former analytical conjectures. In 4 dimensions, we cannot distinguish between the conjectures of Kim and Kosterlitz and the conjecture of Wolf and Kertész, because large crossovers and finite size effects make the measurement of the exponents difficult.     

Mean distance of closest approach of ions: Lithium salts in aqueous solutions

Numerical values for the mean distance of closest approach of ions, “a”, for lithium salts in aqueous solutions are presented and discussed. These values were obtained from both experimental activity and diffusion coefficients, and estimated by using different theoretical approaches.     

Intensity dependence of two-center nonvolatile holographic recording in LiNbO3:Cu:Ce crystals

Nonvolatile photorefractive gratings have been recorded in LiNbO₃:Cu:Ce crystals by using a He–Ne laser (633 nm) for recording and an argon ion laser (458 nm) for sensitizing. The sensitizing light increases the recording sensitivity by a−bexp(−I_s/c) and saturation behavior will appear with high enough intensity of sensitizing light. The recording light increases the slope of η^1/2 as a function of time during the initial stages of hologram formation by sublinear I^x_r (x<1) and thus the recording light decreases the recording sensitivity. The dependence of saturation diffraction efficiency on the intensities of the recording and sensitizing light shows that there is a maximum dynamic range of the recording process.     

Investigation of light scalar resonances a0(980)/ƒ0(980) with ANKE

A program to investigate the light scalar resonances a₀(980)/ƒ₀(980) in hadronic interactions via their decay into the πη and channels has started at the ANKE spectrometer of COSY-Jülich. As the first step the reactions pp → dπ⁺X and pp → dK⁺X have been measured at two energies, T_p = 2.65 GeV and 2.83 GeV. The status of the analysis at T_p = 2.65 GeV is presented. A total cross section of about 50 nb has been determined for the reaction .     

Superconductivity mechanism of Ba1−xKxBiO3

Based on the singly occupied a_iσ picture and the mechanism of charge fluctuation, the effective Hamiltonian of the two-band Hubbard model is derived by using the degeneracy perturbation theory for the noncuprate compound Ba_1−xK_xBiO₃. By considering the next-neighbour pairing of two opposite spin holes in coordinate space, the Green's function equation of motion and the superconductivity equation are obtained. Furthermore, how the superexchange interaction and the hopping energy affect the next-neighbour pairing has been reasonably explained, and the superconductivity window is due to the Cooper pairing in coordinate space.     

On the B→Xs ll decays in general supersymmetric models

We analyze the inclusive semileptonic decays B→X_s l⁺l⁻ in the framework of the supersymmetric standard model with non-universal soft-breaking terms at GUT scale. We show that the general trend of universal and non-universal models is a decreasing of branching ratio (BR) and increasing of energy asymmetry (AS). However, only non-universal models can have chances to get very large enhancements in BR and AS, corresponding to large (negative) SUSY contributions to the b→sγ amplitude.     

Surface plasmon dispersion relation for normal and tangential modes

A theoretical investigation has been made for the surface plasmon dispersion relations for the case of normal and tangential modes to the surface. The hydrodynamical model has been used. We have obtained the dispersion relation by using the continuity of φ and dφ/dx, where φ is the scalar potential. The dispersion relations obtained in the present work have been successfully compared with the theoretical and experimental work of several authors.