110 GHz rapid, continous tuning from an optical parametric oscillator pumped by a fiber-amplified DBR diode laser

A singly-resonant continuous-wave optical parametric oscillator (cw-OPO) pumped by a fiber-amplified diode laser is described. Tuning of the pump source allowed the OPO output to be tuned continuously, without mode-hops, over 110 GHz in 29 ms. Discontinuous pump tuning over 20 nm in the region of 3.4 µm was also obtained. The rapid and continuous idler tuning was demonstrated by the measurement of a methane absorption spectrum. We believe this to be the first example of a singly-resonant OPO pumped by a fiber-amplified diode laser and the mode-hop free tuning range to be the highest reported for a cw-OPO

Shape resonances in extraordinary transmission

The paper focuses on the extraordinary transmission phenomenon, an example of plasmonics. In a periodic arrangement of sub-wavelength holes in a metal film the transmitted fraction of the incident light exceeds the open air fraction of the film for certain colours. This enhanced transmission has been attributed to a resonant excitation of surface plasmons set up by the periodicity of the array. But by merely changing the shape of the sub-wavelength holes from circular to rectangular can affect the extraordinary transmission

Role of shape and localized resonances in extraordinary transmission through periodic arrays of subwavelength holes: Experiment and theory

The effect of the aspect ratio of rectangular holes on the transmissivity of periodic arrays of subwavelength holes in optically thick metal films is investigated. The transmissivity is found to be highly dependent on the aspect ratio of the holes. Moreover, the wavelengths of maximum transmissivity show a monotonous shift as a function of the aspect ratio of the holes. We attribute the enhanced transmission of the periodic arrays to an interplay of surface plasmons at the surface of the metal and shape resonances (also known as localized modes) inside the holes. The importance of the shape resonances was confirmed by a comparison of transmission through periodic hole arrays and through randomly distributed holes. Dispersion curves of periodic and random hole arrays confirmed the existence of shape resonance as well. We suggest that the localized modes effectively act as waveguides and increase the coupling efficiency of surface plasmons between both sides of the film, which results in a higher transmissivity. The shift of the maxima of the transmissivity may in part be explained by the spectral position of the localized modes in the individual holes. Finally measurements on similar patterns in Ni and Ag revealed that the occurrence of shape resonances is independent of the material of the film

The Effect of Shadowing on Initial Conditions, Transverse Energy and Hard Probes in Ultrarelativistic Heavy Ion Collisions

The effect of shadowing on the early state of ultrarelativistic heavy ion collisions is investigated along with transverse energy and hard process production, specifically Drell-Yan, $J/\psi$, and $\Upsilon$ production. We choose several parton distributions and parameterizations of nuclear shadowing, as well as the spatial dependence of shadowing, to study the influence of shadowing on relevant observables. Results are presented for Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV and Pb+Pb collisions at $\sqrt{s_{NN}} = 5.5$ TeV.Comment: Submitted to Phys. Rev.

Shadowing Effects on Vector Boson Production

We explore how nuclear modifications to the nucleon structure functions, shadowing, affect massive gauge boson production in heavy ion collisions at different impact parameters. We calculate the dependence of $Z^0$, $W^+$ and $W^-$ production on rapidity and impact parameter to next-to-leading order in Pb+Pb collisions at 5.5 TeV/nucleon to study quark shadowing at high $Q^2$. We also compare our Pb+Pb results to the $pp$ rapidity distributions at 14 TeV.Comment: 25 pages ReVTeX, 12 .eps figures, NLO included, version accepted for publication in Physical Review

Heavy Quark Photoproduction in Ultra-peripheral Heavy Ion Collisions

Heavy quarks are copiously produced in ultra-peripheral heavy ion collisions. In the strong electromagnetic fields, c c-bar and b b-bar are produced by photonuclear and two-photon interactions; hadroproduction can occur in grazing interactions. We present the total cross sections, quark transverse momentum and rapidity distributions, as well as the Q Q-bar invariant mass spectra from the three production channels. We consider AA and pA collisions at the Relativistic Heavy Ion Collider and Large Hadron Collider. We discuss techniques for separating the three processes and describe how the AA to pA production ratios might be measured accurately enough to study nuclear shadowing.Comment: Minor changes to satisfy referees and typo fixes; 52 pages including 17 figure

J/ψJ/\psi production in PHENIX

Heavy quarkonia production is expected to be sensitive to the formation of a quark gluon plasma (QGP). The PHENIX experiment has measured $J/\psi$ production at $\sqrt{s_{NN}}=$~200 GeV in Au+Au and Cu+Cu collisions, as well as in reference p+p and d+Au runs. $J/\psi$'s were measured both at mid ($|y|<0.35$) and forward ($1.2<|y|<2.2$) rapidity. In this letter, we present the A+A preliminary results and compare them to normal cold nuclear matter expectations derived from PHENIX d+Au and p+p measurements as well as to theoretical models including various effects (color screening, recombination, sequential melting...).Comment: 5 pages, 7 figures. To appear in the proceedings of Hot Quarks 2006: Workshop for Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May 200

On the solutions of the Schrodinger equation with some molecular potentials: wave function ansatz

Making an ansatz to the wave function, the exact solutions of the $D$% -dimensional radial Schrodinger equation with some molecular potentials like pseudoharmonic and modified Kratzer potentials are obtained. The restriction on the parameters of the given potential, $\delta$ and $\eta$ are also given, where $\eta$ depends on a linear combination of the angular momentum quantum number $\ell$ and the spatial dimensions $D$ and $\delta$ is a parameter in the ansatz to the wave function. On inserting D=3, we find that the bound state eigensolutions recover their standard analytical forms in literature.Comment: 14 page

On angry leaders and agreeable followers: How leaders' emotions and followers' personalities shape motivation and team performance.

Do followers perform better when their leader expresses anger or when their leader expresses happiness? We propose that this depends on the follower’s level of agreeableness. Anger is associated with hostility and conflict—states that are at odds with agreeable individuals’ goals. Happiness facilitates affiliation and positive relations—states that are in line with agreeable individuals’ goals. Accordingly, the two studies we conducted showed that agreeableness moderates the effects of a leader’s emotional displays. In a scenario study, participants with lower levels of agreeableness responded more favorably to an angry leader, whereas participants with higher levels of agreeableness responded more favorably to a neutral leader. In an experiment involving four-person teams, teams composed of participants with lower average levels of agreeableness performed better when their leader expressed anger, whereas teams composed of participants with higher average levels of agreeableness performed better when their leader expressed happiness. Team performance was mediated by experienced workload, which was highest among agreeable followers with an angry leader. Besides having important practical implications, the findings shed new light on the fundamental question of how emotional expressions regulate social behavior

The calibration of the Sudbury Neutrino Observatory using uniformly distributed radioactive sources

The production and analysis of distributed sources of 24Na and 222Rn in the Sudbury Neutrino Observatory (SNO) are described. These unique sources provided accurate calibrations of the response to neutrons, produced through photodisintegration of the deuterons in the heavy water target, and to low energy betas and gammas. The application of these sources in determining the neutron detection efficiency and response of the 3He proportional counter array, and the characteristics of background Cherenkov light from trace amounts of natural radioactivity is described.Comment: 24 pages, 13 figure