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Resultados filtrados por Publicador: Universidade Cornell

Impact of PDF uncertainties at large x on heavy boson production

Brady, L. T.; Accardi, A.; Melnitchouk, W.; Owens, J. F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
239.24152%
We explore the sensitivity of W and Z boson production in hadronic collisions to uncertainties in parton distribution functions (PDFs) at large x arising from uncertainties in nuclear corrections when using deuterium data in global QCD fits. The W and Z differential cross sections show increasing influence of nuclear corrections at high boson rapidities, particularly for the d quark, which is diluted somewhat in the decay lepton rapidity distributions. The effects of PDF uncertainties on heavy W' and Z' bosons beyond the Standard Model become progressively more important for larger boson masses or rapidities, both in p-p collisions at the LHC and in p-pbar scattering at the Tevatron.; Comment: 23 pages, 9 figures; to appear in JHEP

PDF model based on Langevin equation for polydispersed two-phase flows applied to a bluff-body gas-solid flow,

Minier, J. P.; Peirano, E.; Chibbaro, S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/08/2010 Português
Relevância na Pesquisa
239.24152%
The aim of the paper is to discuss the main characteristics of a complete theoretical and numerical model for turbulent polydispersed two-phase flows, pointing out some specific issues. The theoretical details of the model have already been presented [Minier and Peirano, Physics Reports, Vol. 352/1-3, 2001 ]. Consequently, the present work is mainly focused on complementary aspects, that are often overlooked and that require particular attention. In particular, the following points are analysed : the necessity to add an extra term in the equation for the velocity of the fluid seen in the case of twoway coupling, the theoretical and numerical evaluations of particle averages and the fulfilment of the particle mass-continuity constraint. The theoretical model is developed within the PDF formalism. The important-physical choice of the state vector variables is first discussed and the model is then expressed as a stochastic differential equation (SDE) written in continuous time (Langevin equations) for the velocity of the fluid seen. The interests and limitations of Langevin equations, compared to the single-phase case, are reviewed. From the numerical point of view, the model corresponds to an hybrid Eulerian/Lagrangian approach where the fluid and particle phases are simulated by different methods. Important aspects of the Monte Carlo particle/mesh numerical method are emphasised. Finally...

Including heavy quark production in ZEUS-PDF fits

Cooper-Sarkar, A M
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/08/2008 Português
Relevância na Pesquisa
239.24152%
At HERA heavy quarks may contribute up to 30% of the structure function $F_2$. The potential of including heavy-quark data in the ZEUS PDF fits is explored, using $D^*$ double differential cross-sections as well as the inclusive quantities $F_2^{c\bar{c}}$, $F_2^{c\bar{c}}$. The introduction of heavy quarks requires an extension of the DGLAP formalism. The effect of using different heavy flavour number schemes, and different approaches to the running of $\alpha_s$, are compared.; Comment: 4 pages, 4 figures. To be published in the Proceedings of the 16th International Workshop on Deep Inelastic Scattering, DIS2008, London, April 7-11th 2008

Soft-Gluon Resummation and PDF Theory Uncertainties

Sterman, George; Vogelsang, Werner
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/02/2000 Português
Relevância na Pesquisa
239.24152%
Parton distribution functions are determined by the comparison of finite-order calculations with data. We briefly discuss the interplay of higher order corrections and PDF determinations, and the use of soft-gluon resummation in global fits.; Comment: Contribution to the proceedings of the workshop ``Physics at Run II'', Fermilab, 1999; 6 Pages, LaTeX, two figures as eps files

Prospects for measurements of $W^{\pm}$ boson production in association with jets at LHCb, and PDF constraints at large-$x$

Farry, Stephen; Gauld, Rhorry
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/05/2015 Português
Relevância na Pesquisa
239.24152%
The unique forward LHCb acceptance opens the possibility for performing precision Standard Model (SM) processes in a kinematical regime beyond the reach of both ATLAS and CMS experiments. In this article we discuss the feasibility of performing $W^{\pm}j$ measurements with 14 TeV LHCb data. In particular, we find that the leptonic asymmetry at high pseudorapidity, with appropriate cuts on the associated jet, is sensitive to the $d$ quark PDF in a region of Bjorken $x > 0.5$. We also comment on the impact of fiducial and normalised cross section measurements.; Comment: 4.5 pages + references, 5 figures

Strange Quark PDF Uncertainty and its Implications for W/Z Production at the LHC

Kusina, A.; Stavreva, T.; Berge, S.; Olness, F. I.; Schienbein, I.; Kovarik, K.; Jezo, T.; Yu, J. Y.; Park, K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
239.24152%
We investigate the impact of parton distribution functions (PDFs) uncertainties on W/Z production at the LHC, concentrating on the strange quark PDF. Additionally we examine the extent to which precise measurements at the LHC can provide additional information on the proton flavor structure.; Comment: Presented at Light Cone 2012, July 2012, Krakow, Poland, added references

PDF modeling of near-wall turbulent flows: A New model, Weak second-order scheme and a numerical study in a Hybrid configuration

Chibbaro, Sergio; Minier, Jean-Pierre
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/09/2010 Português
Relevância na Pesquisa
239.24152%
In this work, we discuss some points relevant for stochastic modelling of one- and two-phase turbulent flows. In the framework of stochastic modelling, also referred to PDF approach, we propose a new Langevin model including all viscosity effects and thus that is consistent with viscous Navier-Stokes equations. In the second part of the work, we show how to develop a second-order unconditionally stable numerical scheme for the stochastic equations proposed. Accuracy and consistency of the numerical scheme is demonstrated analytically. In the last part of the work, we study the fluid flow in a channel flow with the proposed viscous method. A peculiar approach is chosen: the flow is solved with a Eulerian method and after with the Lagrangian model proposed which uses some of the Eulerian quantities. In this way attention is devoted to the issue of consistency in hybrid Eulerian/Lagrangian methods. It is shown that the coupling is important indeed and that to couple the Lagrangian model to an Eulerian one which is not consistent with the same turbulence physics leads to large errors. This part of the work complements a recent article [Chibbaro and Minier International Journal of Multiphase flows submitted (arXiv:0912.2045)]; Comment: 39 pages...

Multifractal PDF analysis for intermittent systems

Arimitsu, T.; Arimitsu, N.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
239.24152%
The formula for probability density functions (PDFs) has been extended to include PDF for energy dissipation rates in addition to other PDFs such as for velocity fluctuations, velocity derivatives, fluid particle accelerations, energy transfer rates, etc, and it is shown that the formula actually explains various PDFs extracted from direct numerical simulations and experiments performed in a wind tunnel. It is also shown that the formula with appropriate zooming increment corresponding to experimental situation gives a new route to obtain the scaling exponents of velocity structure function, including intermittency exponent, out of PDFs of velocity fluctuations.; Comment: 10 pages, 5 figures