Measurement of the analyzing power of proton-carbon elastic scattering in the CNI region at RHIC

The single transverse spin asymmetry, A_N, of the p-carbon elastic scattering process in the Coulomb Nuclear Interference (CNI) region was measured using an ultra thin carbon target and polarized proton beam in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). In 2004, data were collected to calibrate the p-carbon process at two RHIC energies (24 GeV, 100 GeV). A_N was obtained as a function of momentum transfer -t. The results were fit with theoretical models which allow us to assess the contribution from a hadronic spin flip amplitude.Comment: Contribution to the proceedings of the 16th International Spin Physics Symposium, spin2004 (Trieste

Magneto-Optical Studies of Exciton Effects in Layer-Type Semiconductors

Both experimental and theoretical works were performed with particular reference to a layer-type semiconductor, GaSe, for a coherent treatment of the exciton-like and the oscillatory Landau-like spectra appearing in a form of their combination in semiconductors in magnetic fields. The interband magneto-absorption and the Faraday rotation were measured in pulsed magnetic fields up to ～200 kOe at low temperatures. The theoretical analysis was based mainly on the exact solution for an extremely anisotropic semiconductor in the magnetic field of arbitrary intensity. The exciton effects are discussed in terms of the energy spectrum, the spectral intensity, and the spectral width by the use of the band parameters deduced from the experimental results

Optical Conductivity and Electronic Structure of CeRu4Sb12 under High Pressure

Optical conductivity [s(w)] of Ce-filled skutterudite CeRu4Sb12 has been measured at high pressure to 8 GPa and at low temperature, to probe the pressure evolution of its electronic structures. At ambient pressure, a mid-infrared peak at 0.1 eV was formed in s(w) at low temperature, and the spectral weight below 0.1 eV was strongly suppressed, due to a hybridization of the f electron and conduction electron states. With increasing external pressure, the mid-infrared peak shifts to higher energy, and the spectral weight below the peak was further depleted. The obtained spectral data are analyzed in comparison with band calculation result and other reported physical properties. It is shown that the electronic structure of CeRu4Sb12 becomes similar to that of a narrow-gap semiconductor under external pressure.Comment: 8 pages, 9 figure

Thermodynamic evidence for field-angle dependent Majorana gap in a Kitaev spin liquid

The exactly-solvable Kitaev model of two-dimensional honeycome magnet leads to a quantum spin liquid (QSL) characterized by Majorana fermions, relevant for fault-tolerant topological quantum computations.In the high-field paramagnetic state of $\alpha$-RuCl$_3$, half-integer quantization of thermal Hall conductivity has been reported as a signature of Majorana fermions, but the bulk nature of this state remains elusive.Here, from high-resolution heat capacity measurements under in-plane field rotation, we find strongly angle-dependent low-energy excitations in the bulk of $\alpha$-RuCl$_3$. The excitation gap has a sextuple node structure, and the gap amplitude increases with field, exactly as expected for itinerant Majorana fermions in the Kitaev model.Our thermodynamic results are fully linked with the transport quantization properties, providing the first demonstration of the bulk-edge correspondence in a Kitaev QSL.Comment: 8 pages, 7 figure

Measuring every particle's size from three-dimensional imaging experiments

Often experimentalists study colloidal suspensions that are nominally monodisperse. In reality these samples have a polydispersity of 4-10%. At the level of an individual particle, the consequences of this polydispersity are unknown as it is difficult to measure an individual particle size from microscopy. We propose a general method to estimate individual particle radii within a moderately concentrated colloidal suspension observed with confocal microscopy. We confirm the validity of our method by numerical simulations of four major systems: random close packing, colloidal gels, nominally monodisperse dense samples, and nominally binary dense samples. We then apply our method to experimental data, and demonstrate the utility of this method with results from four case studies. In the first, we demonstrate that we can recover the full particle size distribution {\it in situ}. In the second, we show that accounting for particle size leads to more accurate structural information in a random close packed sample. In the third, we show that crystal nucleation occurs in locally monodisperse regions. In the fourth, we show that particle mobility in a dense sample is correlated to the local volume fraction.Comment: 7 pages, 5 figure

Status and overview of development of the Silicon Pixel Detector for the PHENIX experiment at the BNL RHIC

We have developed a silicon pixel detector to enhance the physics capabilities of the PHENIX experiment. This detector, consisting of two layers of sensors, will be installed around the beam pipe at the collision point and covers a pseudo-rapidity of | \eta | < 1.2 and an azimuth angle of | \phi | ~ 2{\pi}. The detector uses 200 um thick silicon sensors and readout chips developed for the ALICE experiment. In order to meet the PHENIX DAQ readout requirements, it is necessary to read out 4 readout chips in parallel. The physics goals of PHENIX require that radiation thickness of the detector be minimized. To meet these criteria, the detector has been designed and developed. In this paper, we report the current status of the development, especially the development of the low-mass readout bus and the front-end readout electronics.Comment: 9 pages, 8 figures and 1 table in DOCX (Word 2007); PIXEL 2008 workshop proceedings, will be published in the Proceedings Section of JINST(Journal of Instrumentation

Energetic electron precipitation associated with pulsating aurora: EISCAT and Van Allen Probe observations

Pulsating auroras show quasi-periodic intensity modulations caused by the precipitation of energetic electrons of the order of tens of keV. It is expected theoretically that not only these electrons but also sub-relativistic/relativistic electrons precipitate simultaneously into the ionosphere owing to whistler-mode wave–particle interactions. The height-resolved electron density profile was observed with the European Incoherent Scatter (EISCAT) Tromsø VHF radar on 17 November 2012. Electron density enhancements were clearly identified at altitudes >68 km in association with the pulsating aurora, suggesting precipitation of electrons with a broadband energy range from ~10 keV up to at least 200 keV. The riometer and network of subionospheric radio wave observations also showed the energetic electron precipitations during this period. During this period, the footprint of the Van Allen Probe-A satellite was very close to Tromsø and the satellite observed rising tone emissions of the lower-band chorus (LBC) waves near the equatorial plane. Considering the observed LBC waves and electrons, we conducted a computer simulation of the wave–particle interactions. This showed simultaneous precipitation of electrons at both tens of keV and a few hundred keV, which is consistent with the energy spectrum estimated by the inversion method using the EISCAT observations. This result revealed that electrons with a wide energy range simultaneously precipitate into the ionosphere in association with the pulsating aurora, providing the evidence that pulsating auroras are caused by whistler chorus waves. We suggest that scattering by propagating whistler simultaneously causes both the precipitations of sub-relativistic electrons and the pulsating aurora