119231041
Higgs boson production in association with a photon via weak boson fusion
We present next-to-leading order QCD corrections to Higgs production in association with a photon via weak boson fusion at a hadron collider. Utilizing the fully flexible parton level Monte-Carlo program VBFNLO, we find small overall corrections, while the shape of some distributions is sensitive to radiative contributions in certain regions of phase-space. Residual scale uncertainties at next-to-leading order are at the few-percent level. Being perturbatively well under control and exhibiting kinematic features that allow to distinguish it from potential backgrounds, this process can serve as a valuable source of information on the $Hb\bar{b}$ Yukawa coupling.
54521266
LONGITUDINAL GLUON POLARIZATION IN RHIC DOUBLE-SPIN ASYMMETRIES.
The longitudinally polarized gluon density is probed sensitively in hard collisions of polarized protons under the condition that the dominant dynamics are perturbative and of leading twist origin. First data have recently been presented by PHENIX on the double-spin asymmetry A{sub LL}{sup {pi}} for {pi}{sup 0} production at moderate transverse momentum p {perpendicular} {approx_equal} 1 {divided_by} 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p{perpendicular} produces an asymmetry that is basically positive definite in this kinematic range, i.e. A{sub LL}{sup {pi}} {approx}> {Omicron}(-10{sup -3}).
11547130
Longitudinally polarized photoproduction of inclusive hadrons at fixed-target experiments
Abstract.We present a detailed phenomenological study of spin-dependent single-inclusive high- pT hadron photoproduction with particular emphasis on the kinematics relevant for the Compass and Hermes fixed-target experiments. We carefully examine the theoretical uncertainties associated with the only moderate transverse momenta accessible in such measurements and analyze the sensitivity of the relevant spin asymmetries to the gluon polarization in the nucleon as well as to the completely unknown parton content of circularly polarized photons.
17273425
Longitudinally polarized photoproduction of inclusive hadrons beyond the leading order
We present a complete next-to-leading order QCD calculation for single-inclusive large-pT hadron production in longitudinally polarized lepton-nucleon collisions, consistently including ``direct'' and ``resolved'' photon contributions. This process could be studied experimentally at a future polarized lepton-proton collider like eRHIC at BNL. We examine the sensitivity of such measurements to the so far completely unknown parton content of circularly polarized photons.
119280529
Gluons and the quark sea at high energies: distributions, polarization, tomography
This report is based on a ten-week program on Gluons and the quark sea at high-energies, which took place at the Institute for Nuclear Theory (INT) in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics (QCD). This report is organized around the following four major themes: (i) the spin and flavor structure of the proton, (ii) three dimensional structure of nucleons and nuclei in momentum and configuration space, (iii) QCD matter in nuclei, and (iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.
116950712
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report
This Report summarizes the proceedings of the 2013 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections and (2) the comparison of those cross sections with LHC data from Run 1, and projections for future measurements in Run 2.
119295352
QCD at nonzero chemical potential: Recent progress on the lattice
We summarise recent progress in simulating QCD at nonzero baryon density using complex Langevin dynamics. After a brief outline of the main idea, we discuss gauge cooling as a means to control the evolution. Subsequently we present a status report for heavy dense QCD and its phase structure, full QCD with staggered quarks, and full QCD with Wilson quarks, both directly and using the hopping parameter expansion to all orders.
119208157
Wilson fermions at fine lattice spacings: scale setting, pion form factors and (g-2)_mu
We present an update on our on-going project to compute hadronic observables for Nf=2 flavours of O(a) improved Wilson fermions at small lattice spacings. The procedure to determine the lattice scale via the mass of the Omega baryon is described. Furthermore we present preliminary results for the pion form factor computed using twisted boundary conditions, and report on the implementation of a novel approach to determine the contribution of the hadronic vacuum polarisation to the anomalous magnetic moment of the muon.
118107777
A high-statistics study of the nucleon EM form factors, axial charge and quark momentum fraction
We present updated results for the nucleon axial charge and electromagnetic (EM) form factors, which include a significant increase in statistics for all ensembles (up to 4000 measurements), as well as the addition of ensembles with pion masses down to $m_\pi\sim195$ MeV. We also present results for the average quark momentum fraction. The new data allows us to perform a thorough study of the systematic effects encountered in the lattice extraction. We concentrate on systematic effects due to excited-state contaminations for each of the quantities, which we check using several different time separations between the operators at the source and sink through a comparison of plateau fits and the summed operator insertion method (which provides a mechanism to suppress the excited-state contamination). We confirm our earlier finding that a reliable extraction of the axial charge must be based on a method which eliminates excited-state contaminations. Similar conclusions apply to our EM form factor calculations . The measurements are calculated using the CLS ensembles with non-perturbatively O(a) improved Wilson fermions in $N_f=2$ QCD.
118356945
Excited state systematics in extracting nucleon electromagnetic form factors
We present updated preliminary results for the nucleon electromagnetic form factors for nonperturbatively O(a) improved Wilson fermions in N f = 2 QCD measured on the CLS ensembles. The use of the summed operator insertion method allows us to suppress the influence of excited states in our measurements. A study of the effect that excited state contaminations have on the Q2 dependence of the extracted nucleon form factors may then be made through comparisons of the summation method to standard plateau fits, as well as to excited state fits.
118474947
Lattice QCD Studies of the Leading Order Hadronic Contribution to the Muon g 2
The anomalous magnetic moment of the muon, g 2, is one of the most promising observables to identify hints for physics beyond the Standard Model. QCD contributions are currently responsible for the largest fraction of the overall theoretical uncertainty in g 2. The possibility to determine these hadronic contributions from first principles through lattice QCD calculations has triggered a number of recent studies. Recent proposals to improve the accuracy of lattice determinations are reported. We present an update of our studies of the leading-order hadronic contribution to g 2 with improved Wilson fermions.