Study of quark distribution amplitudes of 1<Emphasis Type="Italic">S</Emphasis> and 2<Emphasis Type="Italic">S</Emphasis> heavy quarkonium states

In this paper, the quark distribution amplitudes of 1S and 2S heavy quarkonium states are studied in terms of Gaussian-type wave functions. The transverse momenta p _⊥ integrals of the formulae for the decay constant are performed analytically. Then the quark distribution amplitudes are obtained. In addition, the ξ-moments are also calculated. After fixing the relevant parameters appearing in the quark distribution amplitude, the curves of the quark distribution amplitude for 1S and 2S heavy quarkonium states are plotted. Finally, the numerical results of this approach are compared with the other theoretical predictions.     

Final-state polarization in <Emphasis Type="Italic">B</Emphasis><Stack><Subscript><Emphasis Type="Italic">s</Emphasis></Subscript><Superscript>0</Superscript></Stack> decays

Certain B _s ⁰→V ₁ V ₂ decays (V _i is a vector meson) can be related by flavor SU(3) symmetry to corresponding B _d ⁰→V ₃ V ₄ decays. In this paper, we show that the final-state polarization can be predicted in the B _s ⁰ decay, assuming polarization measurements of the B _d ⁰ decay. This can be done within the scenario of penguin annihilation (PA), which has been suggested as an explanation of the unexpectedly large transverse polarization in B→φ K ^*. PA is used to estimate the breaking of flavor SU(3) symmetry in pairs of decays. Two of these for which PA makes a reasonably precise prediction of the size of SU(3) breaking are (B _s ⁰→φ φ,B _d ⁰→φ K ^0*) and ( ). The polarization measurement in the B _d ⁰ decay can be used to predict the transverse polarization in the B _s ⁰ decay and will allow for testing of PA as well as the other assumptions in the analysis.     

Recent high-<Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript> results from STAR

We present selected recent results of multi-hadron correlation measurements in azimuth and pseudorapidity at intermediate and high p _T in Au+Au collisions at , from the STAR experiment at RHIC. At intermediate p _T , measurements are presented that attempt to determine the origin of the associated near-side (small Δφ) yield at large pseudo-rapidity difference Δη that is found to be present in heavy ion collisions. In addition, results are reported on new multi-hadron correlation measures at high-p _T that use di-hadron triggers and multi-hadron cluster triggers with the goal to constrain the underlying jet kinematics better than in the existing measurements of inclusive spectra and di-hadron correlations.     

<Emphasis Type="Italic">Z</Emphasis><Superscript>0</Superscript>-tagged quark jets at the large hadron collider

The Large Hadron Collider will allow studies of hard probes in nucleus-nucleus collisions which were not accessible at the Relativistic Heavy Ion Collider—even the study of small cross-section Z ⁰-tagged jets becomes possible. Going beyond the measurement of back-to-back correlations of two strongly interacting particles to measure plasma properties, we replace one side by an electromagnetic probe which propagates through the plasma undisturbed and therefore provides a measurement of the energy of the initial hard scattering. We show that at sufficiently high transverse momentum the Z ⁰-tagged jets originate predominately from the fragmentation of quarks and anti-quarks while gluon jets are suppressed. We propose to use lepton-pair tagged jets to study medium-induced partonic energy loss and to measure in-medium parton fragmentation functions to determine the opacity of the quark gluon plasma.     

Production of secondaries in high-energy <Emphasis Type="Italic">d</Emphasis>+Au collisions

In the framework of the quark–gluon string model we calculate the inclusive spectra of secondaries produced in d+Au collisions at intermediate (CERN SPS) and at much higher (RHIC) energies. The results of numerical calculations at intermediate energies are in reasonable agreement with the data. At RHIC energies numerically large inelastic screening corrections (percolation effects) should be accounted for in the calculations. We extract these effects from the existing experimental data of RHIC on minimum-bias and central d+Au collisions. The predictions for p+Au interactions at LHC energy are also given.     

Energy and system dependence of high-<Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript> triggered two-particle near-side correlations

Previous studies have indicated that the near-side peak of high-p _T triggered correlations can be decomposed into two parts, the Jet and the Ridge. We present data on the yield per trigger of the Jet and the Ridge from d+Au, Cu+Cu and Au+Au collisions at GeV and 200 GeV and compare data on the Jet to PYTHIA 8.1 simulations for p+p. PYTHIA describes the Jet component up to a scaling factor, meaning that PYTHIA can provide a better understanding of the Ridge by giving insight into the effects of the kinematic cuts. We present collision energy and system dependence of the Ridge yield, which should help distinguish models for the production mechanism of the Ridge.     

<Emphasis Type="Italic">X</Emphasis>(3872) and other possible heavy molecular states

We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as , , in the framework of the meson exchange model. The exchanged mesons include the pseudoscalar, scalar and vector mesons. Through our investigation, we find the following results. (1) The structure X(3764) is not a molecular state. (2) There exists strong attraction in the range r<1 fm for the system with J=0,1. If future experiments confirm Z ⁺(4051) as a loosely bound molecular state, its quantum number is probably J ^P =0⁺. Its partner state Φ ^**0 may be searched for in the π ⁰ χ _c1 channel. (3) Vector meson exchange provides strong attraction in the channel together with pion exchange. A bound state solution may exist with a reasonable cutoff parameter Λ∼1.4 GeV. X(3872) may be accommodated as a molecular state dynamically although drawing a very definite conclusion needs further investigation. (4) The molecular state may exist.     

Orientation ordering of N<Subscript>2</Subscript> molecules in vertically aligned CN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanotubes

Arrays of vertically aligned nitrogen-doped carbon (CN _x ) nanotubes have been synthesized by decomposition of aerosol mixture of acetonitrile and ferrocene at 850°C. Nitrogen concentration in the outer shells of the CN _x nanotubes was found from X-ray photoelectron spectroscopy (XPS) data to reach ∼6%. The XPS N 1s spectra and N 1s near-edge X-ray absorption fine structure (NEXAFS) spectra identified three chemical forms of nitrogen in the CN _x nanotube arrays: pyridine-like, graphitic, and molecular nitrogen. The π ^* resonance of molecular nitrogen showed clear polarization dependence that indicates predominant orientation of N₂ molecules along the nanotubes axis. The estimated range of the polar angle distribution of the N₂ molecules orientation in the CN _x nanotube array amounts to 15°.     

Target-mass and finite <Emphasis Type="Italic">t</Emphasis> corrections to diffractive deep-inelastic scattering

The quantum field theoretic treatment of inclusive deep-inelastic diffractive scattering given in a previous paper (Blümlein et al. in Nucl. Phys. B 755:112–136, 2006) is discussed in detail using an equivalent formulation with the aim to derive a representation suitable for data analysis. We consider the off-cone twist-2 light-cone operators to derive the target-mass and finite t corrections to diffractive deep-inelastic scattering and deep-inelastic scattering. The corrections turn out to be at most proportional to x|t|/Q ², xM ²/Q ², x=x _BJ or x _ℙ, which suggests an expansion in these parameters. Their contribution varies in size considering diffractive scattering or meson-exchange processes. Relations between different kinematic amplitudes which are determined by one and the same diffractive GPD or its moments are derived. In the limit t,M ²→0 one obtains the results of (Blümlein and Robaschik in Phys. Lett. B 517:222, 2001) and (Blümlein and Robaschik in Phys. Rev. D 65:096002, 2002).     

Electronic structure of thin film iron-tetracyanoethylene: Fe(TCNE)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

Thin film iron-tetracyanoethylene Fe(TCNE) _x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe²⁺ valency. The highest occupied molecular orbital of Fe(TCNE) _x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE⁻ singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)₂ where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe²⁺ (3d⁶) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) _x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)₂ (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T _C ) seen for Fe(TCNE) _x -type magnets.     

Effect of tetragonal lattice distortion of Co<Subscript>70</Subscript>Fe<Subscript>30</Subscript> on the tunneling magnetoresistance of AlO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> based magnetic tunnel junction

The tunneling magnetoresistance of Co₇₀Fe₃₀/AlO _x /Co₇₀Fe₃₀ magnetic tunnel junctions with epitaxial bottom electrode annealed at different temperatures was studied. The TMR was significantly enhanced when the bottom electrodes were annealed at 300°C and above. The interface roughness, barrier width and height are almost identical within the experimental uncertainty. However, high resolution reciprocal space mapping studies showed that the lattice distortion of the epitaxial bottom electrodes from body centered cubic to body centered tetragonal had the same trend as the TMR. The tetragonal lattice distortion is attributed to be the dominant factor for this spin polarization enhancement.     

Observations of nanoscopic,face centered cubic Ti and TiH<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

Transmission electron microscopy has been used to study ball milled and H cycled NaAlH₄ with 10 mol% TiCl₃. Isolated from the main phases in this hydrogen storage system, nanocrystalline aggregates of fcc TiH _x (0≤x<0.67) were found. The value of x was determined based on the assumption of a linear increase of the TiH _x lattice parameter by increasing H content. The size of the TiH _x crystallites was in the range 10 to 20 nm, and the lattice parameter decreased from 4.22 Å in TiH_0.67 to 4.10 Å in pure fcc Ti. Non-equilibrium ball milling and subsequent H cycling in combination with a small crystallite size are believed to make the TiH _x phase stable. The present results are the first observations of fcc TiH _x with low hydrogen content, and the measured fcc lattice parameter of Ti matches first-principles calculations.     

Femtosecond laser ablation of neurons in <Emphasis Type="Italic">C</Emphasis>. <Emphasis Type="Italic">elegans</Emphasis> for behavioral studies

In this paper, the interaction between the inhomogeneous and anisotropic cloak covered infinitely long PEC circular cylinder and the parallel electric-line-source is investigated in detail. First, the permittivity and permeability tensors of the cloak are defined according to Pendry’s model, then the wave equation in the metamaterial cloak is derived; second, the far/near properties of the model are investigated, and using the boundary conditions the electromagnetic fields of the whole region are calculated analytically; finally, based on the analytical expressions, the electric fields of the whole region are demonstrated through numerical results which show the effects of invisibility. Finally, the effects of loss on the performance of the invisible cloak are investigated.     

Electronic structure of defective lithium cobaltites Li<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>CoO<Subscript>2</Subscript>

X-ray absorption, resonant X-ray emission, and X-ray photoelectron spectroscopical methods have been applied for the study of the electronic structure of defective lithium cobaltites Li _x CoO₂ (0.6≤x≤1.0). Resonant O K α X-ray emission spectra of LiCoO₂ showed localized excitonic states due to a dd transition between occupied and unoccupied Co 3d states. On the base of measurements of Co 3s X-ray photoelectron, Co 2p, and O 1s X-ray absorption spectra, it was established that in defective cobaltites the electronic holes are localized mainly in O 2p states. An evidence of phase separation in Li _x CoO₂ has been found. It was shown that the semiconductor-to-metal transition in Li _x CoO₂ (x<0.76) at about 160 K is not accompanied by changes in the Co 3d electronic configuration which remains 3d ⁶.     

Thermo-optic coefficients of monoclinic KLu(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The three thermo-optic coefficients of the biaxial laser host KLu(WO₄)₂ are measured at 633 nm by a deflection method. Their values at 300 K amount to ∂ n _g /∂ T=−7.4×10⁻⁶ K⁻¹; ∂ n _m /∂ T=−1.6×10⁻⁶ K⁻¹ and ∂ n _p /∂ T=−10.8×10⁻⁶ K⁻¹. Nearly athermal propagation directions are found for polarizations along the N _m and N _p dielectric axes.     

<Emphasis Type="Italic">Para</Emphasis>-hexaphenyl nanofiber growth on Au-coated porous alumina templates

The availability of easy and reproducible methods for formation of periodically nanostructured surfaces allows one to study the quasi-epitaxial growth of nanowires on such artificially modified substrates. Here, we demonstrate that crystalline nanofibers of para-hexaphenyl can grow on porous alumina templates with high pore regularity once the templates have been coated by a thin Au film. Nanofibers of that kind represent a model system for the general class of organic nanowires which have chemically changeable optoelectronic properties and hence are of interest for integration into future optoelectronic devices.     

Growth and magneto-optical properties of LiTb(MoO<Subscript>4</Subscript>)<Subscript>2</Subscript> crystal

Lithium terbium molybdate (LiTb(MoO₄)₂) single crystal was grown by the Czochralski method. The lattice parameters of the crystal were determined by X-ray diffraction analysis. The absorption coefficient and the Faraday rotation spectrum (B=1.07 T) were investigated at wavelengths of 400–1500 nm at room temperature. Verdet constants of LiTb(MoO₄)₂ crystal at 532-, 633- and 1064-nm wavelengths were measured by the extinction method. The results show that LiTb(MoO₄)₂ crystal has a larger magneto-optical figure of merit than that of terbium gallium garnet at wavelengths of 600–1500 nm.     

Laser emission in Nd:YVO<Subscript>4</Subscript> channel waveguides at 1064 nm

In this work, we report 1064 nm laser emission in Nd:YVO₄ channel waveguides fabricated by carbon implantation. Typical threshold pump powers (∼808 nm) were ≥45 mW. Maximum conversion efficiency was 11.5% (29.6% slope efficiency), and up to 9 mW of signal was delivered. Sample lengths of 4 mm were sufficient to completely absorb the pump power. The special spectral characteristics of this material such as broad absorption band and superior cross sections compared to the YAG crystal makes it suitable for developing compact sources to be integrated in optoelectronic devices.     

Topologically non-trivial chiral transformations

The role of chiral transformations in effective theories modeling Quantum Chromo Dynamics is reviewed. In the context of the Nambu-Jona-Lasinio model the hidden gauge and massive Yang-Mills approaches to vector mesons are linked by a special chiral transformation which removes the chiral field from the scalar-pseudoscalar sector. The chirally rotated axial vector meson field (à _μ ) transforms homogeneously under flavor rotations and may thus be dropped without violating chiral symmetry. The fermion determinant for static meson field configurations is computed by summing the discretized eigenvalues of the Dirac Hamiltonian. It is discussed how the local chiral transformation loses its unitary character in a finite model space. This technical issue proves to be crucial for the construction of the soliton within the Nambu-Jona-Lasinio model when the chirally rotated axial vector field is neglected. In the background of this soliton the valence quark is strongly bound, and its eigenenergy turns out to be negative. This important feature, which usually is generated by non-vanishing axial vector profiles, is thus maintained by the simplificationà _μ = 0.     

Ultrafast dynamics of bis (<Emphasis Type="Italic">n</Emphasis>-butylimido) perylene thin films excited by two-photon absorption

We report a pump-probe study of the two-photon induced reflectivity changes in bis (n-butylimido) perylene thin films. To enhance the two-photon excitation we deposited bis (n-butylimido) perylene films on top of gold nanoislands. The observed transient response in the reflectivity spectrum of bis (n-butylimido) perylene is due to a depletion of the molecule’s ground state and excited state absorption.