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We report our recent studies on the finite density QCD obtained from lattice QCD simulation with clover-improved Wilson fermions of two flavor and RG-improved gauge action. We approach the subject from two paths, i.e., the imaginary and chemical potentials.
Elastic {pi}N scattering and the reaction {pi}{sup +}p{yields}K{sup +}{Sigma}{sup +} are described simultaneously in a unitary coupled-channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t- and u- channel exchanges that drive the meson-baryon interaction in the different channels. Angular distributions, polarizations, and spin-rotation parameters are compared with available experimental data. The pole structure of the amplitudes is extracted from the analytic continuation.
We present our studies of Lambda-Nucleon ({Lambda}N) interaction by using lattice QCD. The equal-time Nambu-Bethe-Salpeter (NBS) amplitude of the lowest energy scattering state of a proton-{Lambda} system is calculated from lattice QCD. In this report, two different types of gauge configurations are employed: (i) Quenched QCD configurations at {beta} = 5.7 (a = 0.1416(9) fm) on a 32{sup 3}x48 lattice, whose spatial volume is (4.5 fm){sup 3}.(ii)2+1 flavor full QCD configurations generated by the PACS-CS collaboration at {beta} = 1.9 (a = 0.0907(13) fm) on a 32{sup 3}x64 lattice, whose spatial volume is (2.90 fm){sup 3}. The spin-singlet central potential is calculated from the NBS wave function for the spin J = 0 state, whereas the spin-triplet central potential as well as the tensor potential are deduced simultaneously from the NBS wave function for the spin J = 1 state by dividing it into the S-wave and the D-wave components.
We study the s-wave KN interactions in the isospin I = 0, 1 channels and associated exotic state {Theta}{sup +} from 2+1 flavor full lattice QCD simulation for relatively heavy quark mass corresponding to m{sub {pi}} = 871 MeV. The s-wave KN potentials are obtained from the Bethe-Salpeter amplitudes. Potentials in both channels reveal short range repulsions: Strength of the repulsion is stronger in the I = 1 potential. The I = 0 potential is found to have attractive well at mid range. The KN scattering phase shifts are calculated and compared with the experimental data.
We report results for charmonium-nucleon potential V{sub cc}-bar{sub N}(r) from lattice QCD, which is calculated from the equal-time Bethe-Salpeter amplitude through the effective Schroedinger equation. Detailed information of the low-energy interaction between the charmonia ({eta}{sub c} and J/{psi}) and the nucleon is indispensable for exploring the formation of charmonium bound to nuclei. Our simulations are carried out at a lattice cutoff of 1/a{approx_equal}2 GeV in a spatial volume of (3fm){sup 3} with the non-perturbatively O(a)-improved Wilson fermions for the light quarks and a relativistic heavy quark action for the charm quark. Although our main results are calculated in quenched lattice calculations, we also present preliminary full QCD results by using 2+1 flavor QCD configurations generated by the PACS-CS Collaboration. We have found that the charmonium-nucleon potential is weakly attractive at short distances and exponentially screened at large distances.
Neutrino scattering experiments have been studying QCD for over 30 years. From the Gargamelle experiments in the early 70's, through the subsequent bubble chamber and electronic detector experiments in the 80's and 90's, neutrino scattering experiments have steadily accumulated increasing statistics and minimized their systematic errors. An example of the more recent studies of QCD with neutrinos is from the TeVatron neutrino beam--the NuTeV {nu}-Fe experiment. The problem the community faces in trying to study QCD with modern neutrino data is that there is no experimentally verified way to scale neutrino-nucleus (for example, Fe) results to the equivalent neutrino-nucleon values making it difficult to combine neutrino nucleus scattering data with charged-lepton nucleus and nucleon scattering data in QCD global fits to extract parton distribution functions. This is particularly crucial since there is now indications that nuclear effects in neutrino nucleus interactions are different than those measured in charged-lepton nucleus scattering. To better understand this situation, the MINER{nu}A neutrino-nucleus scattering experiment at Fermilab, a collaboration of elementary-particle and nuclear physicists, is systematically studying neutrino nuclear effects off of He, C, Fe and Pb for a more thorough A-dependent study of nuclear PDFs and these correction factors.
The E906/SeaQuest experiment will use the 120 GeV proton beam extracted from the Fermilab Main Injector to measure the Drell-Yan cross section in p-p, p-d, and p-A scattering. Data from liquid hydrogen and deuterium targets will be sensitive to the light anti-quark asymmetry, d-bar/u-bar, over a range of parton momentum fraction 0.04<x<0.45. Previous measurements from the E866/NuSea experiment have shown that while there were clear signs of flavor asymmetry at moderate x, the quark sea became flavor symmetric at higher x, suggesting a possible shift in the underlying mechanism generating the sea. Measurements from solid nuclear targets (carbon, calcium, and tungsten) will determine the modification of antiquark distributions in the nucleus. The results, in addition to being complementary to similar measurements performed through deep inelastic scattering, will also be valuable in providing the nuclear corrections necessary to extract nucleon parton distribution functions from neutrino data. The experiment will start in 2011, and will run for two years.
The neutrino-neutrino interactions inside a supernova core give rise to nonlinear collective effects that significantly influence the neutrino flavor conversions inside the star. I shall describe these interactions, the new oscillation phenomena they generate, and their effect on the neutrino fluxes arriving at the earth.
The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Moessbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using {sup 57}Fe-CEMS. An iron oxide phase (Fe{sup 3+}{sub 4}Fe{sup 2+}{sub 1}O{sub 7}), as thick as 31 A, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.
Investigation on the room temperature strain rate sensitivity using depth sensing nanoindentation is carried out on precursor derived HfO{sub 2}/Si-C-N(O) ceramic nanocomposite sintered using pulsed electric current sintering. Using constant load method the strain rate sensitivity values are estimated. Lower strain rate sensitivity of ∼ 3.7 × 10{sup −3} is observed and the limited strain rate sensitivity of these ceramic nanocomposites is explained in terms of cluster model. It is concluded that presence of amorphous Si-C-N(O) clusters are responsible for the limited flowability in these ceramics.
The Streptococcus mutans antigen I/II (AgI/II) is a cell surface-localized protein that adheres to salivary components and extracellular matrix molecules. Here we report the 2.5 {angstrom} resolution crystal structure of the complete C-terminal region of AgI/II. The C-terminal region is comprised of three major domains: C{sub 1}, C{sub 2}, and C{sub 3}. Each domain adopts a DE-variant IgG fold, with two {beta}-sheets whose A and F strands are linked through an intramolecular isopeptide bond. The adherence of the C-terminal AgI/II fragments to the putative tooth surface receptor salivary agglutinin (SAG), as monitored by surface plasmon resonance, indicated that the minimal region of binding was contained within the first and second DE-variant-IgG domains (C{sub 1} and C{sub 2}) of the C terminus. The minimal C-terminal region that could inhibit S. mutans adherence to SAG was also confirmed to be within the C{sub 1} and C{sub 2} domains. Competition experiments demonstrated that the C- and N-terminal regions of AgI/II adhere to distinct sites on SAG. A cleft formed at the intersection between these C{sub 1} and C{sub 2} domains bound glucose molecules from the cryo-protectant solution, revealing a putative binding site for its highly glycosylated receptor SAG. Finally, electron microscopy images confirmed the elongated structure of AgI/II and enabled building a composite tertiary model that encompasses its two distinct binding regions.
Rising interest in molten salt reactors for commercial power production presents an opportunity to evaluate the techniques used to characterize materials of nuclear forensic interest. Since extensive research has been performed to identify and develop signatures of light water reactor (LWR) materials (e.g. uranium ore concentrates and uranium dioxide fuel pellets), we use this as a basis to explore possibilities for molten salt signature development. Through this comparative method, nuclear forensic signatures used today to identify the provenance of nuclear materials found out of regulatory control are adapted to molten salt reactor (MSR) fuel cycle materials. Radiological, elemental composition, isotopic composition, and model age signatures will likely not need large adaptations before being applied to MSR materials but may need to expand to be applicable to both thorium- and uranium-fueled systems. The liquid nature of molten salt fuel may erase signatures related to production and irradiation history that are informative for typical LWR materials. However, it may also lead to opportunities for new signatures, such as cooling rate–controlled morphology. Targets identified for further research include radiological attributes of fuel salts; elemental, chemical, and isotopic analysis of salts with differing production routes; morphological effects of various thermodynamic environments; and relevant fuel cycle radiochronometers. Additionally, the comparative nature of the proposed signatures implies a need for MSR-relevant databases and the production of salt standard reference materials.
We have developed a line-by-line Atmospheric Radiative Transfer for Titan code that includes the most recent laboratory spectroscopic data and haze descriptions relative to Titan's stratosphere. We use this code to model Cassini Composite Infrared Spectrometer data taken during the numerous Titan flybys from 2006 to 2012 at surface-intercepting geometry in the 600-1500 cm{sup -1} range for latitudes from 50 Degree-Sign S to 50 Degree-Sign N. We report variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE). We find indication for a weakening of the temperature gradient with warming of the stratosphere and cooling of the lower mesosphere. In addition, we infer precise concentrations for the trace gases and their main isotopologues and find that the chemical composition in Titan's stratosphere varies significantly with latitude during the 6 years investigated here, with increased mixing ratios toward the northern latitudes. In particular, we monitor and quantify the amplitude of a maximum enhancement of several gases observed at northern latitudes up to 50 Degree-Sign N around mid-2009, at the time of the NSE. We find that this rise is followed by a rapid decrease in chemical inventory in 2010 probably due to a weakening north polar vortex with reduced lateral mixing across the vortex boundary.
We describe the construction of a template set of spectral energy distributions (SEDs) for the estimation of photometric redshifts of luminous red galaxies (LRGs) with a Bayesian template fitting method. By examining the color properties of several publicly available SED sets within a redshift range of 0 < z {approx}< 0.5 and comparing them to Sloan Digital Sky Survey (SDSS) Data Release 7 data, we show that only some of the investigated SEDs approximately match the colors of the LRG data throughout the redshift range, however not at the quantitative level required for precise photometric redshifts. This is because the SEDs of galaxies evolve with time (and redshift) and because at fixed redshift the LRG colors have an intrinsic spread such that they cannot be matched by one SED only. We generate new SEDs by superposing model SEDs of composite stellar populations with a burst model, allowing both components to be reddened by dust, in order to match the data in five different redshift bins. We select a set of SEDs which represents the LRG data in color space within five redshift bins, thus defining our new SED template set for photometric redshift estimates. The results we obtain with the new template set and our Bayesian template fitting photometric redshift code (PhotoZ) are nearly unbiased, with a scatter of {sigma}{sub {Delta}z} = 0.027 (including outliers), a fraction of catastrophic outliers (|z{sub phot} - z{sub spec}|/(1 + z{sub spec}) > 0.15) of {eta} = 0.12%, and a normalized median absolute rest frame deviation (NMAD) of {sigma}{sub NMAD} = 1.48 Multiplication-Sign MAD = 0.017 for non-outliers. We show that templates that optimally describe the brightest galaxies (-24.5 {<=} M{sub R} {<=} -22.7) indeed vary from z = 0.1 to z = 0.5, consistent with aging of the stellar population. Furthermore, we find that templates that optimally describe galaxies at z < 0.1 strongly differ as a function of the absolute magnitude of the galaxies, indicating an increase in star formation activity for less luminous galaxies. Our findings based on the photometry of the SDSS LRGs and our SED template fitting are supported by comparison to the average SDSS LRG spectra in different luminosity and redshift bins.
Here we quantify the regional co-benefits to future air quality on annual to daily mean timescales from implementing mitigation measures to stabilise future climate. Two consistent future emissions pathways are used within the composition-climate model HadGEM3-UKCA: one is a reference pathway of future economic growth and development (REF), whilst the Representative Concentration Pathway 4.5 (RCP4.5) assumes the same development pathway but stabilises anthropogenic radiative forcing at 4.5 W m -2 in 2100. Implementing greenhouse gas mitigation measures in RCP4.5 reduces global mean air pollutant emissions by up to 30% in the 2050s, in addition to mitigating climate. Annual mean surface concentrations of ozone and PM 2.5 decrease by 10-20% from the combined reductions in emissions and climate change. The number of days exceeding the World Health Organization’s (WHO) daily mean air quality standards are reduced by up 47 days for ozone and 15 days for PM 2.5 over different world regions. The air quality co-benefits from mitigation measures are mainly achieved from reductions in anthropogenic emissions, although benefits can be offset due to changes in climate. In terms of anthropogenic climate forcing, while the reduction in global mean effective radiative forcing (ERF) in 2050, relative to the present day, due to enacting carbon dioxide mitigation measures (-0.43 Wm -2 ) is enhanced by decreases in tropospheric ozone (-0.26 Wm -2 ) and methane (-0.2 W m -2 ), it is partially offset by a positive aerosol ERF from reductions in aerosols (+0.35 Wm -2 ). This study demonstrates that policies to mitigate climate change have added co-benefits for global and regional air quality on annual to daily timescales. However, the effectiveness of the greenhouse gas policies in reducing anthropogenic climate forcing is reduced in the near-term due to the combined changes in ozone and aerosols.
This paper explores properties of baryons and finite density baryonic matter in an artificial world in which N{sub c}, the number of colors, is large and the quarks of all species are degenerate and much larger than {Lambda}{sub QCD}. It has long been known that in large N{sub c} quantum chromodynamics (QCD), baryons composed entirely of heavy quarks are accurately described in the mean-field approximation. However, the detailed properties of baryons in the combined large N{sub c} and heavy-quark limits have not been fully explored. Here some basic properties of baryons are computed using a variational approach. At leading order in both the large N{sub c} and heavy-quark expansions the baryon mass is shown to be M{sub baryon}{approx_equal}N{sub c}M{sub Q}(1-0.054 26{alpha}-tilde{sub s}{sup 2}), where {alpha}-tilde{sub s}{identical_to}N{sub c}{alpha}s. The baryon form factor is also computed. Baryonic matter, the analog of nuclear matter in this artificial world, should also be well described in the mean-field approximation. In the special case where all baryons have an identical spin-flavor structure, it is shown that in the formal heavy-quark and large N{sub c} limit interactions between baryons are strictly repulsive at low densities. The energy per baryon is computed in this limit and found to be exponentially small. It is shown that when the restriction to baryons with an identical spin-flavor structure is dropped, a phase of baryonic matter exists with a density of 2N{sub f} times that for the restricted case but with the same energy (where N{sub f} is the number of degenerate flavors). It is shown that this phase is at least metastable.
The cross sections of B{sub c} absorption by {pi} mesons are calculated using a hadronic Lagrangian based on the SU(5) flavor symmetry. Calculated cross sections are found to be in the ranges 2-7 mb and 0.2-2 mb for the processes B{sub c}{sup +}{pi}{yields}DB and B{sub c}{sup +}{pi}{yields}D*B*, respectively, when the monopole form factor is included. These results could be useful in calculating the production rate of B{sub c} mesons in relativistic heavy ion collisions.
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