On Glauber modes in Soft-Collinear Effective Theory

Gluon interactions involving spectator partons in collisions at hadronic machines are investigated. We find a class of examples in which a mode, called Glauber gluons, must be introduced to the effective theory for consistency.Comment: 19 pages, three figures. Uses JHEP3.cl

Population genetic structure in European lobsters: implications for connectivity, diversity and hatchery stocking

The European lobster Homarus gammarus is a marine crustacean prized for seafood, but populations across its range are threatened by fishery overexploitation. The species’ larval stages are planktonic, suggesting considerable dispersal among populations. The potential threats of overexploitation and erosion of population structure due to hatchery releases or inadvertent introductions make it important to understand the genetic structuring of populations across multiple geographic scales. Here we assess lobster population structure at a fine scale in Cornwall, southwestern UK, where a hatchery-stocking operation introduces cultured individuals into the wild stock, and at a broader European level, in order to compare the spatial scale of hatchery releases with that of population connectivity. Microsatellite genotypes of 24 individuals from each of 13 locations in Cornwall showed no fine-scale population structure across distances of up to ~230 km. Significant differentiation and isolation by distance were detected at a broader scale, using 300 additional individuals comprising a further 15 European samples. Signals of genetic heterogeneity were evident between an Atlantic cluster and samples from Sweden. Connectivity within the Atlantic and Swedish clusters was high, although evidence for isolation by distance and a transitional zone within the eastern North Sea suggested that direct gene exchange between these stocks is limited and fits a stepping-stone model. We conclude that hatchery-reared lobsters should not be released where broodstock are distantly sourced but, using Cornwall as a case study, microsatellites revealed no evidence that the normal release of hatchery stock exceeds the geographic scale of natural connectivity.European Social FundWorshipful Company of FishmongersBBSRCThis research was supported by Lobster Grower 2, a 3 yr project funded by Innovate-UK (TS/ N006097/1) and BBSRC (BB/N013891/1) under an AgriTech Catalyst Industrial Stage Award. We are also greatly appreciative of the studentship funding provided by the European Social Fund and of the grant awarded by the Fishmonger’s Company, UK, both of which made the work possible

An effective theory for jet propagation in dense QCD matter: jet broadening and medium-induced bremsstrahlung

Two effects, jet broadening and gluon bremsstrahlung induced by the propagation of a highly energetic quark in dense QCD matter, are reconsidered from effective theory point of view. We modify the standard Soft Collinear Effective Theory (SCET) Lagrangian to include Glauber modes, which are needed to implement the interactions between the medium and the collinear fields. We derive the Feynman rules for this Lagrangian and show that it is invariant under soft and collinear gauge transformations. We find that the newly constructed theory SCET$_{\rm G}$ recovers exactly the general result for the transverse momentum broadening of jets. In the limit where the radiated gluons are significantly less energetic than the parent quark, we obtain a jet energy-loss kernel identical to the one discussed in the reaction operator approach to parton propagation in matter. In the framework of SCET$_{\rm G}$ we present results for the fully-differential bremsstrahlung spectrum for both the incoherent and the Landau-Pomeranchunk-Migdal suppressed regimes beyond the soft-gluon approximation. Gauge invariance of the physics results is demonstrated explicitly by performing the calculations in both the light-cone and covariant $R_{\xi}$ gauges. We also show how the process-dependent medium-induced radiative corrections factorize from the jet production cross section on the example of the quark jets considered here.Comment: 52 pages, 15 pdf figures, as published in JHE

The Soft-Collinear Bootstrap: N=4 Yang-Mills Amplitudes at Six and Seven Loops

Infrared divergences in scattering amplitudes arise when a loop momentum $\ell$ becomes collinear with a massless external momentum $p$. In gauge theories, it is known that the L-loop logarithm of a planar amplitude has much softer infrared singularities than the L-loop amplitude itself. We argue that planar amplitudes in N=4 super-Yang-Mills theory enjoy softer than expected behavior as $\ell \parallel p$ already at the level of the integrand. Moreover, we conjecture that the four-point integrand can be uniquely determined, to any loop-order, by imposing the correct soft-behavior of the logarithm together with dual conformal invariance and dihedral symmetry. We use these simple criteria to determine explicit formulae for the four-point integrand through seven-loops, finding perfect agreement with previously known results through five-loops. As an input to this calculation we enumerate all four-point dual conformally invariant (DCI) integrands through seven-loops, an analysis which is aided by several graph-theoretic theorems we prove about general DCI integrands at arbitrary loop-order. The six- and seven-loop amplitudes receive non-zero contributions from 229 and 1873 individual DCI diagrams respectively.Comment: 27 pages, 48 figures, detailed results including PDF and Mathematica files available at http://goo.gl/qIKe8 v2: minor corrections v3: figure 7 corrected, Lemma 2 remove

Parton Fragmentation within an Identified Jet at NNLL

The fragmentation of a light parton i to a jet containing a light energetic hadron h, where the momentum fraction of this hadron as well as the invariant mass of the jet is measured, is described by "fragmenting jet functions". We calculate the one-loop matching coefficients J_{ij} that relate the fragmenting jet functions G_i^h to the standard, unpolarized fragmentation functions D_j^h for quark and gluon jets. We perform this calculation using various IR regulators and show explicitly how the IR divergences cancel in the matching. We derive the relationship between the coefficients J_{ij} and the quark and gluon jet functions. This provides a cross-check of our results. As an application we study the process e+ e- to X pi+ on the Upsilon(4S) resonance where we measure the momentum fraction of the pi+ and restrict to the dijet limit by imposing a cut on thrust T. In our analysis we sum the logarithms of tau=1-T in the cross section to next-to-next-to-leading-logarithmic accuracy (NNLL). We find that including contributions up to NNLL (or NLO) can have a large impact on extracting fragmentation functions from e+ e- to dijet + h.Comment: expanded introduction, typos fixed, journal versio

Finite temperature calculations for the bulk properties of strange star using a many-body approach

We have considered a hot strange star matter, just after the collapse of a supernova, as a composition of strange, up and down quarks to calculate the bulk properties of this system at finite temperature with the density dependent bag constant. To parameterize the density dependent bag constant, we use our results for the lowest order constrained variational (LOCV) calculations of asymmetric nuclear matter. Our calculations for the structure properties of the strange star at different temperatures indicate that its maximum mass decreases by increasing the temperature. We have also compared our results with those of a fixed value of the bag constant. It can be seen that the density dependent bag constant leads to higher values of the maximum mass and radius for the strange star.Comment: 21 pages, 2 tables, 12 figures Astrophys. (2011) accepte

Delayed gastric emptying and reduced postprandial small bowel water content of equicaloric whole meal bread versus rice meals in healthy subjects: novel MRI insights

BACKGROUND/OBJECTIVES: Postprandial bloating is a common symptom in patients with functional gastrointestinal (GI) diseases. Whole meal bread (WMB) often aggravates such symptoms though the mechanisms are unclear. We used magnetic resonance imaging (MRI) to monitor the intragastric fate of a WMB meal (11% bran) compared to a rice pudding (RP) meal. SUBJECTS/METHODS: 12 healthy volunteers completed this randomised crossover study. They fasted overnight and after an initial MRI scan consumed a glass of orange juice with a 2267 kJ WMB or an equicaloric RP meal. Subjects underwent serial MRI scans every 45 min up to 270 min to assess gastric volumes and small bowel water content and completed a GI symptom questionnaire. RESULTS: The MRI intragastric appearance of the two meals was markedly different. The WMB meal formed a homogeneous dark bolus with brighter liquid signal surrounding it. The RP meal separated into an upper, liquid layer and a lower particulate layer allowing more rapid emptying of the liquid compared to solid phase (sieving). The WMB meal had longer gastric half emptying times (132±8 min) compared to the RP meal (104±7 min), P<0.008. The WMB meal was associated with markedly reduced MRI-visible small bowel free mobile water content compared to the RP meal, P<0.0001. CONCLUSIONS: WMB bread forms a homogeneous bolus in the stomach which inhibits gastric sieving and hence empties slower than the equicaloric rice meal. These properties may explain why wheat causes postprandial bloating and could be exploited to design foods which prolong satiation

An NIH intramural percubator as a model of academic-industry partnerships: from the beginning of life through the valley of death

In 2009 the NIH publicly announced five strategic goals for the institutes that included the critical need to translate research discoveries into public benefit at an accelerated pace, with a commitment to find novel ways to engage academic investigators in the process. The emphasis on moving scientific advancements from the laboratory to the clinic is an opportune time to discuss how the NIH intramural program in Bethesda, the largest biomedical research center in the world, can participate in this endeavor. Proposed here for consideration is a percolator-incubator program, a 'percubator' designed to enable NIH intramural investigators to develop new medical interventions as quickly and efficiently as possible

Form Factors in N=4 Super Yang-Mills and Periodic Wilson Loops

We calculate form factors of half-BPS operators in N=4 super Yang-Mills theory at tree level and one loop using novel applications of recursion relations and unitarity. In particular, we determine the expression of the one-loop form factors with two scalars and an arbitrary number of positive-helicity gluons. These quantities resemble closely the MHV scattering amplitudes, including holomorphicity of the tree-level form factor, and the expansion in terms of two-mass easy box functions of the one-loop result. Next, we compare our result for these form factors to the calculation of a particular periodic Wilson loop at one loop, finding agreement. This suggests a novel duality relating form factors to periodic Wilson loops.Comment: 26 pages, 10 figures. v2: typos fixed, comments adde

MAXIPOL: a balloon-borne experiment for measuring the polarization anisotropy of the cosmic microwave background radiation

We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure the E-mode polarization anisotropy of the cosmic microwave background radiation (CMB) on angular scales of 10 arcmin to 2 degrees. MAXIPOL is the first CMB experiment to collect data with a polarimeter that utilizes a rotating half-wave plate and fixed wire-grid polarizer. We present the instrument design, elaborate on the polarimeter strategy and show the instrument performance during flight with some time domain data. Our primary data set was collected during a 26 hour turnaround flight that was launched from the National Scientific Ballooning Facility in Ft. Sumner, New Mexico in May 2003. During this flight five regions of the sky were mapped. Data analysis is in progress