DTUJET--93 Sampling inelastic proton--proton and antiproton--proton collisions according to the two--component Dual Parton Model

A new version of a Monte Carlo Program for hadronic multi-particle production is presented. It is based on the two-component Dual Parton Model which includes the dual topological unitarization of soft and hard cross sections. The model treats both soft (low $p_{\perp}$) and hard (minijet, large $p_{\perp}$) processes in a unified and consistent way. The unified description is important at TeV-energies of hadron colliders, where the hard perturbative cross sections of QCD become large and comparable to the total cross sections.Comment: 20 pages , PHYSZZX, SI-93-

Time-Series Ensemble Photometry and the Search for Variable Stars in the Open Cluster M11

This work presents the first large-scale photometric variability survey of the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over two observing seasons were analyzed (using crowded field and ensemble photometry techniques) to obtain high relative precision photometry. In this study we focus on the detection of candidate member variable stars for follow-up studies. A total of 39 variable stars were detected and can be categorized as follows: 1 irregular (probably pulsating) variable, 6 delta Scuti variables, 14 detached eclipsing binary systems, 17 W UMa variables, and 1 unidentified/candidate variable. While previous proper motion studies allow for cluster membership determination for the brightest stars, we find that membership determination is significantly hampered below V=15,R=15.5 by the large population of field stars overlapping the cluster MS. Of the brightest detected variables that have a high likelihood of cluster membership, we find five systems where further work could help constrain theoretical stellar models, including one potential W UMa member of this young cluster.Comment: 38 pages, 13 figures, accepted for December 2005 AJ, high-resolution version available upon reques

Initial State: Theory Status

I present a brief discussion of the different approaches to the study initial state effects in heavy ion collisions in view of the recent results from Pb+Pb and p+p collisions at the LHC.Comment: 8 pages, 6 figures. Contribution to the proceedings of the XXII International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, QM2011. Annecy, France, 22-28 May 201

Dynamical noncommutativity

The model of dynamical noncommutativity is proposed. The system consists of two interrelated parts. The first of them describes the physical degrees of freedom with coordinates q^1, q^2, the second one corresponds to the noncommutativity r which has a proper dynamics. After quantization the commutator of two physical coordinates is proportional to the function of r. The interesting feature of our model is the dependence of nonlocality on the energy of the system. The more the energy, the more the nonlocality. The lidding contribution is due to the mode of noncommutativity, however, the physical degrees of freedom also contribute in nonlocality in higher orders in \theta.Comment: published versio

Sources, transport and deposition of iron in the global atmosphere

International audienceAtmospheric deposition of iron (Fe) plays an important role in controlling oceanic primary productivity. However, the sources of Fe in the atmosphere are not well understood. In particular, the combustion sources of Fe and the subsequent deposition to the oceans have been accounted for in only few ocean biogeochemical models of the carbon cycle. Here we used a mass-balance method to estimate the emissions of Fe from the combustion of fossil fuels and biomass by accounting for the Fe contents in fuel and the partitioning of Fe during combustion. The emissions of Fe attached to aerosols from combustion sources were estimated by particle size, and their uncertainties were quantified by a Monte Carlo simulation. The emissions of Fe from mineral sources were estimated using the latest soil mineralogical database to date. As a result, the total Fe emissions from combustion averaged for 1960–2007 were estimated to be 5.3 Tg yr−1 (90% confidence of 2.3 to 12.1). Of these emissions, 1, 27 and 72% were emitted in particles 10 μm (PM> 10), respectively, compared to a total Fe emission from mineral dust of 41.0 Tg yr−1 in a log-normal distribution with a mass median diameter of 2.5 μm and a geometric standard deviation of 2. For combustion sources, different temporal trends were found in fine and medium-to-coarse particles, with a notable increase in Fe emissions in PM1 since 2000 due to an increase in Fe emission from motor vehicles (from 0.008 to 0.0103 Tg yr−1 in 2000 and 2007, respectively). These emissions have been introduced in a global 3-D transport model run at a spatial resolution of 0.94° latitude by 1.28° longitude to evaluate our estimation of Fe emissions. The modelled Fe concentrations as monthly means were compared with the monthly (57 sites) or daily (768 sites) measured concentrations at a total of 825 sampling stations. The deviation between modelled and observed Fe concentrations attached to aerosols at the surface was within a factor of 2 at most sampling stations, and the deviation was within a factor of 1.5 at sampling stations dominated by combustion sources. We analysed the relative contribution of combustion sources to total Fe concentrations over different regions of the world. The new mineralogical database led to a modest improvement in the simulation relative to station data even in dust-dominated regions, but could provide useful information on the chemical forms of Fe in dust for coupling with ocean biota models. We estimated a total Fe deposition sink of 8.4 Tg yr−1 over global oceans, 7% of which originated from the combustion sources. Our central estimates of Fe emissions from fossil fuel combustion (mainly from coal) are generally higher than those in previous studies, although they are within the uncertainty range of our estimates. In particular, the higher than previously estimated Fe emission from coal combustion implies a larger atmospheric anthropogenic input of soluble Fe to the northern Atlantic and northern Pacific Oceans, which is expected to enhance the biological carbon pump in those regions

The orbits of the quadruple star system 88 Tau A from PHASES differential astrometry and radial velocity

We have used high precision differential astrometry from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) project and radial velocity measurements covering a time-span of 20 years to determine the orbital parameters of the 88 Tau A system. 88 Tau is a complex hierarchical multiple system comprising a total of six stars; we have studied the brightest 4, consisting of two short-period pairs orbiting each other with an 18-year period. We present the first orbital solution for one of the short-period pairs, and determine the masses of the components and distance to the system to the level of a few percent. In addition, our astrometric measurements allow us to make the first determination of the mutual inclinations of the orbits. We find that the sub-systems are not coplanar.Comment: Corrected Author Ordering; 12 Pages, Accepted for publication in Ap

The Frequency of Binary Stars in the Core of 47 Tucanae

Differential time series photometry has been derived for 46422 main-sequence stars in the core of 47 Tucanae. The observations consisted of near-continuous 160-s exposures alternating between the F555W and F814W filters for 8.3 days in 1999 July with WFPC2 on the Hubble Space Telescope. Using Fourier and other search methods, eleven detached eclipsing binaries and fifteen W UMa stars have been discovered, plus an additional ten contact or near-contact non-eclipsing systems. After correction for non-uniform area coverage of the survey, the observed frequencies of detached eclipsing binaries and W UMa's within 90 arcseconds of the cluster center are 0.022% and 0.031% respectively. The observed detached eclipsing binary frequency, the assumptions of a flat binary distribution with log period and that the eclipsing binaries with periods longer than about 4 days have essentially their primordial periods, imply an overall binary frequency of 13 +/- 6 %. The observed W UMa frequency and the additional assumptions that W UMa's have been brought to contact according to tidal circularization and angular momentum loss theory and that the contact binary lifetime is 10^{9} years, imply an overall binary frequency of 14 +/- 4 %. An additional 71 variables with periods from 0.4 - 10 days have been found which are likely to be BY Draconis stars in binary systems. The radial distribution of these stars is the same as that of the eclipsing binaries and W UMa stars and is more centrally concentrated than average stars, but less so than the blue straggler stars. A distinct subset of six of these stars fall in an unexpected domain of the CMD, comprising what we propose to call red stragglers.Comment: Accepted for publication in the Astrophysical Journal, 65 pages including 26 figure

Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum

We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO2 at the last glacial maximum (LGM). We examine 5 different realisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton physiology at the LGM. Measured changes in carbon-13 and carbon-14, as well as a qualitative reconstruction of the change in ocean carbon export are used to evaluate the results. Overall, we find that while a reduction in ocean ventilation at the LGM is necessary to reproduce carbon-13 and carbon-14 observations, this circulation results in a low net sink for atmospheric CO2. In contrast, while biogeochemical processes contribute little to carbon isotopes, we propose that most of the change in atmospheric CO2 was due to such factors. However, the lesser role for circulation means that when all plausible factors are accounted for, most of the necessary CO2 change remains to be explained. This presents a serious challenge to our understanding of the mechanisms behind changes in the global carbon cycle during the geologic past

Sharpening Low-Energy, Standard-Model Tests via Correlation Coefficients in Neutron Beta-Decay

The correlation coefficients a, A, and B in neutron beta-decay are proportional to the ratio of the axial-vector to vector weak coupling constants, g_A/g_V, to leading recoil order. With the advent of the next generation of neutron decay experiments, the recoil-order corrections to these expressions become experimentally accessible, admitting a plurality of Standard Model (SM) tests. The measurement of both a and A, e.g., allows one to test the conserved-vector-current (CVC) hypothesis and to search for second-class currents (SCC) independently. The anticipated precision of these measurements suggests that the bounds on CVC violation and SCC from studies of nuclear beta-decay can be qualitatively bettered. Departures from SM expectations can be interpreted as evidence for non-V-A currents.Comment: 4 pages, REVTeX, intro. broadened, typos fixed, to appear in PR