Measurement of D^{*\pm} meson production and determination of F_2^{ccbar} at low Q2 in deep-inelastic scattering at HERA

Inclusive production of D ∗ mesons in deep-inelastic ep scattering at HERA is studied in the range 51.25 GeV and |η(D ∗)|<1.8. The data sample corresponds to an integrated luminosity of 348 pb−1 collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F2cc to the proton structure function F 2 is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers

A global analysis of diffractive events at HERA

We extract diffractive parton distribution functions (DPDFs) and diffractive structure functions from the most recent H1 and ZEUS diffractive DIS data obtained by various methods. We consider Pomeron as an object with parton distribution function, evolving according to the next-to-leading order (NLO) DGLAP equations within the framework of the `Fixed Flavour Number Scheme' (FFNS). Having performed a global fit analysis, we achieve a very good description of all available measurements by introducing a new set of quark distribution form for the Pomeron. We predict longitudinal and charm proton diffractive structure function as well. Our results are compared with other analysis from the literature.Comment: 28 Pages, 15 Figures, 3 Table

A precision measurement of the inclusive ep scattering cross section at HERA

A measurement of the inclusive deep inelastic neutral current e + p scattering cross section is reported in the region of four-momentum transfer squared, 12&isin;GeV 2&le;Q 2&le;150&isin;GeV 2, and Bjorken x, 2&times;10 -4&le;x&le;0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E e =27.6 GeV and E p =920 GeV, respectively. The data are combined with previously published data, taken at E p =820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data. &copy; 2009 Springer-Verlag/ Societ&agrave; Italiana di Fisica

Realizing the business benefits of enterprise IT

The development and implementation of IT/IS systems inherently requires a deep understanding of user requirements. However, experience shows that a key barrier to the success of an IT/IS system, is the manner by which it is adopted by end users. As such, this viewpoint article presents an overview of those typical enterprise IT user traits as experience by the author. These traits are placed in the context of the steps that need to be taken in terms of a lifecycle approach to business systems implementation. Thus, the paper describes those drivers which inhibit the adoption of enterprise IT/IS projects from a user expectation point of view. By outlining key benefits of such systems, the author presents a 6-stage approach to benefits realisation, known as the acronym, ASSIST. By applying such an approach, the management of business process change and delivery of IT/IS should be more achievable, by addressing the specific needs and expectations of different types of users, as identified in the text of the article. In doing so, the definition of those key IT/IS benefits as outlined in the ASSIST phase approach described is therefore a useful addition to existing project management and business analysis tools and techniques, that can be utilised by enterprise IT system delivery managers as well as Senior IT/IS managemen

The complex Grothendieck for 2x2 matrices

We show that the complex Grothendieck constant for 2x2 matrices is 1

Ecological Consequences of Lost Anadromous Forage Fish in Freshwater Ecosystems

Beginning in the early 1600s, dam construction in New England obstructed anadromous fish access to spawning grounds during migration. As a result, anadromous forage fish populations have declined, which has impacted freshwater, marine, and terrestrial ecosystems. To determine the impacts of dams on anadromous forage fish and freshwater ecosystems, I used historical and current data to estimate population changes in alewives (Alosa pseudoharengus) from 1600-1900. A significant reduction in spawning habitat occurred in New England as a result of 1,642 dams constructed between 1600 and 1900, resulting in 14.8% and 16.6% lake and stream habitat remaining by 1900, respectively. In eight New England watersheds, this translates to an estimated cumulative annual loss of 30 B juvenile alewives available as freshwater forage and 538 M year 1, 2 and 3 alewives available as marine forage. The cumulative annual lost number of adult return spawners was conservatively 17 M fish, or 3,642 metric tons. Lost marine-derived nutrients from adult return spawners were 11 T phosphorus, 64 T nitrogen, and 410 T carbon. A comparison of predator fish growth and condition in alewife and non-alewife lakes showed that white perch (Morone Americana) and yellow perch (Perca flavescens) have higher condition in early summer in lakes with alewives. Predator growth rates (length-at-age) were significantly higher in early life stages (ages 1 and 2) when alewives were present, but significantly lower in late life stages (ages 3 and older). Results indicate a greater maximum length obtained by mature fish when alewives are absent, and an earlier age and length at maturity when alewives are present. These results indicate significant ecosystem impacts of lost anadromous forage fish, with bottom-up trophic effects across multiple time scales and biological processes. An ecosystem-based management approach should be used by inland and marine aquatic managers, and ecosystem connectivity and trophic interactions should be considered when managing migratory fish and prioritizing restoration goals