Searches for Physics Beyond the Standard Model at Colliders

All experimental measurements of particle physics today are beautifully described by the Standard Model. However, there are good reasons to believe that new physics may be just around the corner at the TeV energy scale. This energy range is currently probed by the Tevatron and HERA accelerators and selected results of searches for physics beyond the Standard Model are presented here. No signals for new physics have been found and limits are placed on the allowed parameter space for a variety of different particles.Comment: Proceedings for 2007 Europhysics Conference on High Energy Physics, Manchester, July 200

Acoustically enhanced remediation, Phase 2: Technology scaling

Weiss Associates is conducting the following three phase program investigating the in-situ application of acoustically enhanced remediation (AER) of contaminated unconsolidated soil and ground water under both saturated and unsaturated conditions: Phase I-- laboratory scale parametric investigation; Phase II--technology Scaling; and Phase III--large scale field tests. AER addresses the need for NAPL (either lighter or denser than water: LNAPL or DNAPL, respectively) in high and low permeability sediments, and the remediation of other types of subsurface contaminants (e.g., metals, radionuclides) in low permeability soils. This program has been placed in the U.S. Department of Energy`s (DOE`s) DNAPL product. Phase I indicated that AER could be used to effectively remediate NAPL in high permeability soil, and that removal of NAPL from low permeability soil could be increased since the water flux through these soils was significantly increased. Phase II, Technology Scaling, the subject of this paper, focused on (1) evaluating the characteristics of an AER field deployment system, (2) developing DNAPL flow and transport performance data under acoustic excitation, (3) predicting the effect of acoustic remediation in three-dimensional unconsolidated hydrogeologic conditions, (4) conducting an engineering analysis of acoustical sources, and (5) identifying candidate field site(s) for large-scale field testing of the technology

Regularity of higher codimension area minimizing integral currents

This lecture notes are an expanded version of the course given at the ERC-School on Geometric Measure Theory and Real Analysis, held in Pisa, September 30th - October 30th 2013. The lectures aim to explain the main steps of a new proof of the partial regularity of area minimizing integer rectifiable currents in higher codimension, due originally to F. Almgren, which is contained in a series of papers in collaboration with C. De Lellis (University of Zurich).Comment: This text will appear in "Geometric Measure Theory and Real Analysis", pp. 131--192, Proceedings of the ERC school in Pisa (2013), L. Ambrosio Ed., Edizioni SNS (CRM Series

On Solving the Coronal Heating Problem

This article assesses the current state of understanding of coronal heating, outlines the key elements of a comprehensive strategy for solving the problem, and warns of obstacles that must be overcome along the way.Comment: Accepted by Solar Physics; Published by Solar Physic

LEMUR: Large European Module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission

Understanding the solar outer atmosphere requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1" and 0.3"), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 17 and 127 nm. The LEMUR slit covers 280" on the Sun with 0.14" per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km/s or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission.Comment: 35 pages, 14 figures. To appear on Experimental Astronom

A global fit to determine the pseudoscalar mixing angle and the gluonium content of the eta' meson

We update the values of the eta-eta' mixing angle and of the eta' gluonium content by fitting our measurement R_phi = BR(phi to eta' gamma)/ BR(phi to eta gamma) together with several vector meson radiative decays to pseudoscalars (V to P gamma), pseudoscalar mesons radiative decays to vectors (P to V gamma) and the eta' to gamma gamma, pi^0 to gamma gamma widths. From the fit we extract a gluonium fraction of Z^2_G = 0.12 +- 0.04, the pseudoscalar mixing angle psi_P = (40.4 +- 0.6) degree and the phi-omega mixing angle psi_V = (3.32 +- 0.09) degree. Z^2_G and psi_P are fairly consistent with those previously published. We also evaluate the impact on the eta' gluonium content determination of future experimental improvements of the eta' branching ratios and decay width.Comment: 13 pages, 7 figures to submit to JHE

Doubling the mobility of InAs/InGaAs selective area grown nanowires

Selective area growth (SAG) of nanowires and networks promise a route toward scalable electronics, photonics, and quantum devices based on III-V semiconductor materials. The potential of high-mobility SAG nanowires however is not yet fully realised, since interfacial roughness, misfit dislocations at the nanowire/substrate interface and nonuniform composition due to material intermixing all scatter electrons. Here, we explore SAG of highly lattice-mismatched InAs nanowires on insulating GaAs(001) substrates and address these key challenges. Atomically smooth nanowire/substrate interfaces are achieved with the use of atomic hydrogen (a-H) as an alternative to conventional thermal annealing for the native oxide removal. The problem of high lattice mismatch is addressed through an InxGa1-xAs buffer layer introduced between the InAs transport channel and the GaAs substrate. The Ga-In material intermixing observed in both the buffer layer and the channel is inhibited via careful tuning of the growth temperature. Performing scanning transmission electron microscopy and x-ray diffraction analysis along with low-temperature transport measurements we show that optimized In-rich buffer layers promote high-quality InAs transport channels with the field-effect electron mobility over 10 000 cm2 V-1 s-1. This is twice as high as for nonoptimized samples and among the highest reported for InAs selective area grown nanostructures.The project was supported by Microsoft Quantum, the European Research Council (ERC) under Grant No. 716655 (HEMs-DAM), and the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant No. 722176. The authors acknowledge Dr. Keita Ohtani for technical support and fruitful discussions. D.V.B. is grateful to Dr. Juan-Carlos Estrada Saldaña for careful reading of the manuscript. The authors thank Francesco Montalenti, Marco Albani and Leo Miglio for scientific discussions. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. The HAADF-STEM microscopy was conducted in the Laboratorio de Microscopias Avanzadas at Instituto de Nanociencia de Aragon-Universidad de Zaragoza. M.C.S. has received funding from the European Unionâs Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 754510 (PROBIST). The funding agency is Consejo Superior de Investigaciones Científicas (CSIC) and the project reference is “Research Platform on Quantum Technologies PTI-001”

What is the Nature of EUV Waves? First STEREO 3D Observations and Comparison with Theoretical Models

One of the major discoveries of the Extreme ultraviolet Imaging Telescope (EIT) on SOHO were intensity enhancements propagating over a large fraction of the solar surface. The physical origin(s) of the so-called `EIT' waves is still strongly debated. They are considered to be either wave (primarily fast-mode MHD waves) or non-wave (pseudo-wave) interpretations. The difficulty in understanding the nature of EUV waves lies with the limitations of the EIT observations which have been used almost exclusively for their study. Their limitations are largely overcome by the SECCHI/EUVI observations on-board the STEREO mission. The EUVI telescopes provide high cadence, simultaneous multi-temperature coverage, and two well-separated viewpoints. We present here the first detailed analysis of an EUV wave observed by the EUVI disk imagers on December 07, 2007 when the STEREO spacecraft separation was $\approx 45^\circ$. Both a small flare and a CME were associated with the wave cadence, and single temperature and viewpoint coverage. These limitations are largely overcome by the SECCHI/EUVI observations on-board the STEREO mission. The EUVI telescopes provide high cadence, simultaneous multi-temperature coverage, and two well-separated viewpoints. Our findings give significant support for a fast-mode interpretation of EUV waves and indicate that they are probably triggered by the rapid expansion of the loops associated with the CME.Comment: Solar Physics, 2009, Special STEREO Issue, in pres

Observation of an Excited Bc+ State

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

Study of the process e+e- -> omega pi0 in the phi-meson mass region with the KLOE detector

We have studied the e+e- -> omegapi0 cross section in the sqrt(s) interval 1000-1030 MeV using the pi+pi-pi0pi0 and pi0pi0gamma final states with a sample of ~600 pb^-1 collected with the KLOE detector at DAFNE. By fitting the observed interference pattern around M_phi for both final states, we extract the ratio of the decay widths Gamma(omega->pi0gamma)/Gamma(omega->pi+pi-pi0) = 0.0897 +- 0.0016 and derive the branching fractions BR(omega -> pi+pi-pi0)= (90.24 +- 0.19)%, BR(omega -> pi0gamma) = (8.09 +- 0.14)%. The parameters describing the e+e- -> omegapi0 reaction around M_\phi are also used to extract the branching fraction for the OZI and G-parity violating phi -> omegapi0 decay: BR(phi->omegapi0) = (4.4 +- 0.6)x10^-5.Comment: 12 Pages, 4 figures, submitted to Physics Letter