Viscosity of argon to 5 GPa and 673 K

A rolling-sphere technique has been used to measure shear viscosities of (supercritical) fluid argon in the diamond-anvil cell between the temperatures of 294 and 673 K, up to a maximum pressure of 5 GPa. At these pressures, the viscosities can be fit to a modified free-volume expression. A single correlation between reduced viscosity and reduced residual entropy is shown to give a good account of the current high pressure data, data at lower pressures and those for the sub-critical liquid.     

A mid-infrared scanned-wavelength laser absorption sensor for carbon monoxide and temperature measurements from 900 to 4000 K

Mid-infrared laser absorption sensors based on quantum cascade laser (QCL) technology offer the potential for high-sensitivity, selective, and high-speed measurements of temperature and concentration for species of interest in high-temperature environments, such as those found in combustion devices. A new mid-infrared QCL absorption sensor for carbon monoxide and temperature measurements has been developed near the intensity peak of the CO fundamental band at 4.6 μm, providing orders-of-magnitude greater sensitivity than the overtone bands accessible with telecommunications lasers. The sensor is capable of probing the R(9), R(10), R(17), and R(18) transitions of the CO fundamental ro-vibrational band which are located at frequencies where H₂O and CO₂ spectral interference is minimal. Temperature measurements are made via scanned-wavelength two-line ratio techniques using either the R(9) and R(17) or the R(10) and R(18) line pairs. The high-speed (1–2 kHz) scanned-wavelength sensor is demonstrated in room-temperature gas cell measurements of CO and, to demonstrate the potential of the sensor for high-temperature thermometry, in shock-heated gases containing CO for a very wide range of temperature (950–3500 K) near 1 atm. To our knowledge, these measurements represent the first use of QCL-based absorption sensor for thermometry at elevated combustion-like temperatures. The high-temperature measurements of CO mole fraction and temperature agree with the post-reflected-shock conditions within ±1.5% and ±1.2% (1σ deviation), respectively.     

Constraining new physics with B→K ∗ μ + μ − in the early LHC era

We investigate the observables available in the angular distribution of B→K ^? μ ⁺ μ ^? to identify those suitable for measurements in the first few years of LHC data taking. There are three observables that may be extracted by counting signal events as a function of one or two decay angles and correspond to large features of the full angular distribution in the Standard Model: A _FB, F _L, and S ₅. Two of these are well known in the experimental community; however, we show that measuring S ₅ adds complementary sensitivity to physics beyond the Standard model. Like A _FB, it features a zero-crossing point with reduced hadronic uncertainties at leading order and in the large recoil limit. Due to the high gradient of S ₅ at this point, we find it would be possible for LHCb to measure it to high precision. Current experimental model independent constraints on parameter space are presented and predictions made for the values of the A _FB and S ₅ zero-crossing points. The relative impact of early LHCb measurements of A _FB, F _L, and S ₅ is assessed. These issues are explored with a new model of the decay that can be used with standard simulation tools such as EvtGen.     

Precise measurement of Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and study of K→e ν γ

We present a precise measurement of the ratio R _K =Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and a study of the radiative process K→e ν γ, performed with the KLOE detector. The results are based on data collected at the Frascati e ⁺ e ^? collider DAΦNE for an integrated luminosity of 2.2 fb^?1. We find R _K =(2.493±0.025_stat±0.019_syst)×10^?5, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate dΓ(K→e ν γ)/dE _γ for photon energies 10<E _γ < 250 MeV. Results are compared with predictions from theory.     

New results from the T2K neutrino oscillation experiment

The T2K experiment searches for the appearance of electron neutrinos in a muon neutrino beam. The rate of this process is sensitive to the neutrino mixing parameter θ ₁₃. Recent measurements that $\theta_{13} \ne 0$ imply that ν _μ → ν _e oscillations should be observable. Using all data through May 15, 2012 the T2K experiment has detected 10 candidate ν _e events, with an expected background for θ ₁₃?=?0 of 2.73±0.37 events. This 3.2σ excess of ν _e events is the strongest indication to date for appearance of electron neutrinos in a neutrino oscillation experiment, and for normal mass hierarchy and δ _CP ?=?0 yields $0.059 < \sin^2 2\theta_{13} < 0.164$ at the 68 % C.L.     

How Tc can go above 100 K in the YBCO family

We report the results of the electronic structure calculation of a newly discovered member of the YBCO high-T_c family, i.e., Y₃Ba₅Cu₈O₁₈ (Y358) with T_c>100, based on the full-potential linearized augmented plane waves method (FP-LAPW) of density functional theory in the generalized gradient approximation (GGA). The evolution of the number of hole carriers in different sites of the CuO₂ planes and CuO chains has been investigated in comparison with the other YBCO family members, i.e., Y123, Pr123, Y124, and Y247. The results suggest that pumping hole carriers out of the chains toward the planes enhances the transition temperature. The band structure calculations have been performed for Y358, and the results show similar features with the other family members. Most notably, a van Hove singularity forms near the X point of the Brillouin zone below the Fermi level and within the energy of the buckling phonon mode, for which the interplay is discussed.     

K*0Σ+ Photoproduction from Threshold to 3.0 GeV

The CLAS collaboration and the CBELSA/TAPS collaboration reported the differential cross section data for K*⁰ photoproduction, and found that the t-channel K exchange dominates the production amplitudes at small scattering angles. The measurement of forward-angle parity spin asymmetry for the γ p → K*⁰Σ⁺ reaction, where the theoretical calculations show an unambiguous signal, would establish the role of the κ(800). The γ p → K*⁰Σ⁺ reaction, where the Σ⁺ was identified through missing mass, on a liquid hydrogen target was measured at the LEPS detector in the energy from threshold to 3.0 GeV by using a linearly polarized photon beam at SPring-8. Decay angular distributions in the rest frame of the K ⁺ π ^? system were fit to extract spin-density matrix elements of the K*⁰ decay.     

Interpreting near-side correlations and the RHIC beam energy scan

Recent data from heavy ion collisions at RHIC show strong near-side correlations extending over several units of rapidity. This ridge-like correlation exhibits an abrupt onset with collision centrality. In this talk, I argue that the centrality and beam-energy dependence of these near-angle correlations could provide access to information about the Quark Gluon Plasma phase boundary and the Equation of State of nuclear matter. A beam-energy-scan at RHIC will better reveal the true source of these correlations and should be a high priority at RHIC.