7,101 research outputs found
T-odd effects in photon-jet production at the Tevatron
No full textThe angular distribution in photon-jet production in p (p) over bar -> gamma jet X is studied within a generalized factorization scheme taking into account the transverse momentum of the partons in the initial hadrons. Within this scheme an anomalously large cos2 phi asymmetry observed in the Drell-Yan process could be attributed to the T-odd, spin and transverse momentum dependent parton distribution function h(1)(perpendicular to q) (x, p(perpendicular to)(2)). This same function is expected to produce a cos 2 phi asymmetry in the photon-jet production cross section. We give the expression for this particular azimuthal asymmetry, which is estimated to be smaller than the Drell-Yan asymmetry but still of considerable size for Tevatron kinematics. This offers a new possibility to study T-odd effects at the Tevatron. (C) 2008 Elsevier B.V. All rights reserved
How Tight is Hadamard's Bound?
No full textFor a real square matrix , Hadamard's inequality gives an
upper bound for the determinant of . This upper bound is sharp if
and only if the rows of are orthogonal. In this paper we study
how much we can expect that overshoots the determinant of ,
when the rows of are chosen randomly on the surface of the
sphere. This gives an indication of the ``wasted effort'' in some
modular algorithms
Extracting Boer-Mulders functions from p+D Drell-Yan processes
No full textWe extract the Boer- Mulders functions of valence and sea quarks in the proton from unpolarized p + D Drell- Yan data measured by the FNAL E866 Collaboration. Using these Boer- Mulders functions, we calculate the cos2 phi asymmetries in unpolarized pp Drell- Yan processes, both for the FNAL E866/ NuSea and the BNL Relativistic Heavy Ion Collider experiments. We also estimate the cos2 phi asymmetries in the unpolarized p (P) over bar Drell- Yan processes at GSI.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)37ARTICLE5null7
Fast Deterministic Computation of Determinants of Dense Matrices
No full textIn this paper we consider deterministic computation of the exact
determinant of a dense matrix of integers. We present a new
algorithm with worst case complexity ,
where is the dimension of the matrix
and is a bound on the entries in , but with average expected
complexity , assuming some
plausible properties about
the distribution of . We will also describe a practical version
of the algorithm and include timing data to compare this algorithm
with existing ones. Our result does not depend on ``fast'' integer or
matrix techniques
Boer–Mulders function of the pion and pretzelosity distribution of the proton in the polarized pion-proton Drell–Yan process at COMPASS
No full textAbstract We present a phenomenological analysis of the q T -weighted transverse spin dependent azimuthal asymmetry recently measured by the COMPASS Collaboration in polarized pion-proton Drell–Yan process. In the kinematical regimes explored by experiments, we consider the leading-twist contributions from the Boer–Mulders distribution functions h 1 ⊥ ( x , k T 2 ) of both the pion and the proton, the transversity distribution h 1 ( x , k T 2 ) and the pretzelosity distribution h 1 T ⊥ ( x , k T 2 ) of the proton, with the unpolarized transverse-momentum-dependent distribution function f 1 ( x , k T 2 ) of the proton being also involved in the calculation. By comparing the data reported by the COMPASS Collaboration with theoretical calculated results, we find that the COMPASS measurements represent the first experimental evidence of the Boer–Mulders effect in polarized Drell–Yan process. We also test the universality between proton and pion Boer–Mulders functions
Sivers, Boer-Mulders and worm-gear distributions at next-to-leading order
No full textWe compute the Sivers, Boer-Mulders, worm-gear (T and L) transverse momentum
dependent distributions in terms of twist-two and twist-three collinear
distributions in the small-b limit up to next-to-leading order (NLO) in
perturbation theory.Comment: 26 pages, 1 figur
Breakwaters under construction exposed to oblique waves
No full textDuring the construction of breakwaters contractors often encounter undesired reshaping of exposed core material. This reshaping is comparable to the deformation process of berm breakwaters in which the outer profile reshapes into a more stable s-curve. In the case of oblique waves this deformation is enhanced by a longshore transport of stones leading to even more loss of material and damage. Throughout the years few formulas were derived for both processes which describe the behaviour of berm breakwaters as well as gravel beaches reasonably well. These formulas however turned out to be inadequate when it comes to describing the behaviour of core material. In particular the influence of the wide grading of quarry run, commonly used as core material, is to a large extent unknown and generally not described in the available relations. To investigate this influence of the stone grading on both the two-dimensional deformation and longshore transport new physical model tests were carried out in the wave basin at Delft University of Technology. In total 12 tests were executed in which two different gradings, three different angles of wave attack and two different wave spectra were tested. Data collected from the tests included wave and profile measurements together with the displacements of stones, originating from two colour beams which were applied in the middle of the trunk. These data along with visual observations eventually led to a conceptual model describing stone movements in both transverse and longshore direction. Using Matlab three-dimensional profile and erosion models were generated from which the different profile parameters were determined. With respect to the distance from origin, for each test an exponential relation was derived to describe the stone displacements. After determination of the area of uniform transport these exponential relations were used to calculate the total longshore transport by means of extrapolation and multiple integrations. Subsequently all parameters found were compared to the formulas currently available for both processes. Regarding the deformation parameters the test results produced the best fit with the formulas derived in [MERLI 2009]. Still on several occasions a deviant relation was found concerning the influence of wave obliquity. In addition, the formulas became less accurate for the narrow grading used in the tests, which fell outside the range tested by Merli. However, for the crest height of the deformed profile test results deviated completely from the available formula as no influence was found whatsoever for all tested parameters. Here the deviation was contributed to a higher instability of the part above the initial deformation, partly due to the steepness of the slope. On the subject of the longshore transport clear trends were found describing the influence of the varying parameters. Both a higher wave load and wider grading lead to an increase of the longshore transport. For the wider grading, however, this increase gave a rather distorted image, as not all fractions in the mixture were transported evenly. Due to segregation the coarsest fractions were mostly transported in the transverse direction while the finer fractions were transported further away in the longitudinal direction. Alternatively, computation of the longshore volume transport proved to be more representative. Regarding the effect of wave obliquity an increase in angle of wave attack of 30 to 45 degrees was accompanied by a decrease in longshore transport; though this decrease was less than already available formulas indicated. However despite the fact that it describes a completely different trend concerning this particular influence, the best fit was found after multiplying the relation derived by [ALIKHANI 1996] with a factor 100.Hydraulic EngineeringCivil Engineering and Geoscience
Sivers and Boer-Mulders observables from lattice QCD
No full textWe present a first calculation of transverse momentum-dependent nucleon observables in dynamical lattice QCD employing nonlocal operators with staple-shaped, “process-dependent” Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and, in particular, to access nonuniversal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm-gear function g[subscript 1T]. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an n[subscript f]=2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV
Sivers and Boer-Mulders distributions in boost-invariant longitudinal position space
No full textThe boost invariant longitudinal position space variable , the Fourier conjugate to skewness , unravels the longitudinal impact parameter information in a proton. Here, we investigate skewness sensitivity of T-odd leading twist GTMDs considering a momentum transfer to longitudinal as well as transverse direction and present a detailed study of the spin-transverse momentum correlation through Sivers and Boer-Mulders Wigner Distributions in boost invariant longitudinal position space. The -space distributions of T-odd sector show oscillatory patterns sensitive to square of the total momentum transfer , analogous to the diffraction scattering of wave in Optics. An additional effect on the diffraction pattern is reported caused by interference between transverse momentum transfer \bfd to the transverse momentum \bfp of quarks.15 Pages, 7 figure
The odour of white bread
No full textVolatile constituents of white bread were investigated. Different methods were used for isolating and concentrating components to avoid artefacts as far as possible. Especially good was enlarged vapour analysis. Ninety-four components were identified, including hydrocarbons, alcohols, aldehydes, ketones, acids, esters as well as nitrogen, sulphur and miscellaneous compounds. The concentration of the main components in the vapour above white bread was determined by direct vapour analysis. The odour threshold values of these components in aqueous solution were determined, and the odour values calculated as the ratio of concentration to odour threshold value to estimate their contribution to the total odour. The Maillard reaction of the cysteine/cystine-ribose system was investigated in a search for components which can be expected in heat-processed food products, and to find out whether during this reaction compounds possessing bread-like odours were formed. Forty-five components were identified, including thiophenes, thiazoles, thiols, pyrazines, pyrroles, amines, furans, aldehydes, ketones and miscellaneous compounds. Possible pathways for the formation of 2-acylthiazoles and of 3-methyl, and 5-methyl substituted 2-formylthiophenes are proposed
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