Energy dependence of jet transport parameter and parton saturation in quark-gluon plasma

We study the evolution and saturation of the gluon distribution function in the quark-gluon plasma as probed by a propagating parton and its effect on the computation of jet quenching or transport parameter $\hat{q}$. For thermal partons, the saturation scale $Q^2_s$ is found to be proportional to the Debye screening mass $\mu_D^2$. For hard probes, evolution at small $x=Q^2_s/6ET$ leads to jet energy dependence of $\hat{q}$. We study this dependence for both a conformal gauge theory in weak and strong coupling limit and for (pure gluon) QCD. The energy dependence can be used to extract the shear viscosity $\eta$ of the medium since $\eta$ can be related to the transport parameter for thermal partons in a transport description. We also derive upper bounds on the transport parameter for both energetic and thermal partons. The later leads to a lower bound on shear viscosity-to-entropy density ratio which is consistent with the conjectured lower bound $\eta/s\geq 1/4\pi$. We also discuss the implications on the study of jet quenching at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider and the bulk properties of the dense matter.Comment: 15 pages in RevTex with 9 figures (v4 final published version

Evidance for an Oxygen Diffusion Model for the Electric Pulse Induced Resistance Change Effect in Oxides

Electric pulse induced resistance (EPIR) switching hysteresis loops for Pr0.7Ca0.7MnO3 (PCMO) perovskite oxide films were found to exhibit an additional sharp "shuttle peak" around the negative pulse maximum for films deposited in an oxygen deficient ambient. The device resistance hysteresis loop consists of stable high resistance and low resistance states, and transition regions between them. The resistance relaxation of the "shuttle peak" and its temperature behavior as well as the resistance relaxation in the transition regions were studied, and indicate that the resistance switching relates to oxygen diffusion with activation energy about 0.4eV. An oxygen diffusion model with the oxygen ions (vacancies) as the active agent is proposed for the non-volatile resistance switching effect in PCMO.Comment: 7 pages, 5 figure

Twist-4 contributions to the azimuthal asymmetry in SIDIS

We calculate the differential cross section for the unpolarized semi-inclusive deeply inelastic scattering (SIDIS) process $e^-+N \to e^-+q+X$ in leading order (LO) of perturbative QCD and up to twist-4 in power corrections and study in particular the azimuthal asymmetry . The final results are expressed in terms of transverse momentum dependent (TMD) parton matrix elements of the target nucleon up to twist-4. %Under the maximal two-gluon correlation approximation, these TMD parton matrix elements in a nucleus %can be expressed terms of a Gaussian convolution of that in a nucleon with the width given by the jet transport %parameter inside cold nuclei. We also apply it to $e^-+A \to e^-+q+X$ and illustrate numerically the nuclear dependence of the azimuthal asymmetry by using a Gaussian ansatz for the TMD parton matrix elements.Comment: 9 pages, afigur

Constraints and Soliton Solutions for the KdV Hierarchy and AKNS Hierarchy

It is well-known that the finite-gap solutions of the KdV equation can be generated by its recursion operator.We generalize the result to a special form of Lax pair, from which a method to constrain the integrable system to a lower-dimensional or fewer variable integrable system is proposed. A direct result is that the $n$-soliton solutions of the KdV hierarchy can be completely depicted by a series of ordinary differential equations (ODEs), which may be gotten by a simple but unfamiliar Lax pair. Furthermore the AKNS hierarchy is constrained to a series of univariate integrable hierarchies. The key is a special form of Lax pair for the AKNS hierarchy. It is proved that under the constraints all equations of the AKNS hierarchy are linearizable.Comment: 12 pages, 0 figur

Energy average formula of photon gas rederived by using the generalized Hermann-Feynman theorem

By virtue of the generalized Hermann-Feynmam theorem and the method of characteristics we rederive energy average formula of photon gas, this is another useful application of the theorem.Comment: 2 page

Experimental Investigation of Blast-Pressure Attenuation by Cellular Concrete

Results from an experimental investigation of the dynamic response of cellular concrete subjected to blast-pressure loading are presented. The cellular concrete has large entrained porosity in the form of uniformly distributed air cells in a matrix of hardened cement. Under quasi-static loading, once the applied stress exceeds the crushing strength of the cellular concrete, crushing and densification of material results in an upward concave stress-strain response. The shock-tube experimental test setup used for generating blast-pressure loading in a controlled manner is described. Experimental results from the cellular concrete subjected to blast-pressure loading with pressure amplitude greater than its crushing strength indicate that a compression stress wave, which produces compaction of the material due to collapse of the cellular structure, is produced in the material. As the compaction front propagates in the material, there is a continuous decrease in its amplitude. The impulse of the blast pressure wave is conserved. When a sufficient length of the cellular concrete is present, the applied blast pressure wave is completely attenuated to a rectangular stress pulse. The transmitted stress to a substrate from cellular concrete when an applied blast pressure wave is completely attenuated resembles a rectangular stress pulse of amplitude slightly higher than the crushing strength of the material with a duration predicted by the applied blast impulse

Modified Fragmentation Function from Quark Recombination

Within the framework of the constituent quark model, it is shown that the single hadron fragmentation function of a parton can be expressed as a convolution of shower diquark or triquark distribution function and quark recombination probability, if the interference between amplitudes of quark recombination with different momenta is neglected. The recombination probability is determined by the hadron's wavefunction in the constituent quark model. The shower diquark or triquark distribution functions of a fragmenting jet are defined in terms of overlapping matrices of constituent quarks and parton field operators. They are similar in form to dihadron or trihadron fragmentation functions in terms of parton operator and hadron states. Extending the formalism to the field theory at finite temperature, we automatically derive contributions to the effective single hadron fragmentation function from the recombination of shower and thermal constituent quarks. Such contributions involve single or diquark distribution functions which in turn can be related to diquark or triquark distribution functions via sum rules. We also derive QCD evolution equations for quark distribution functions that in turn determine the evolution of the effective jet fragmentation functions in a thermal medium.Comment: 23 pages in RevTex with 8 postscript figure

Direct pulsed laser crystallization of nanocrystals for absorbent layers in photovoltaics: Multiphysics simulation and experiment

Direct pulsed laser crystallization (DPLC) of nanoparticles of photoactive material-Copper Indium Selenide (nanoCIS) is investigated by multiphysics simulation and experiments. Laser interaction with nanoparticles is fundamentally different from their bulk counterparts. A multiphysics electromagnetic-heat transfer model is built to simulate DPLC of nanoparticles. It is found smaller photoactive nanomaterials (e.g., nanoCIS) require less laser fluence to accomplish the DPLC due to their stronger interactions with incident laser and lower melting point. The simulated optimal laser fluence is validated by experiments observation of ideal microstructure. Selectivity of DPLC process is also confirmed by multiphysics simulation and experiments. The combination effects of pulse numbers and laser intensity to trigger laser ablation are investigated in order to avoid undesired results during multiple laser processing. The number of pulse numbers is inversely proportional to the laser fluence to trigger laser ablation. (C) 2013 AIP Publishing LLC

Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm(2)/V s at a low carrier concentration of 7.9 x 10(+19) cm(-3). This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity. (C) 2014 AIP Publishing LLC