15684588
Observing strongly interacting vector boson systems at the CERN Large Hadron Collider
We explore the potential of the CERN Large Hadron Collider to access a strongly interacting electroweak symmetry breaking sector via weak boson scattering with W{sup +}W{sup -}jj, ZZjj, and W{sup {+-}}Zjj final states. As examples of models with scalar or vector resonances we concentrate on a scenario with a heavy Higgs boson and on a warped Higgsless Kaluza-Klein model of narrow spin-one resonances. The signal and the most prominent background processes are evaluated using exact tree-level matrix elements including full off-shell and finite width effects for final states with two tagging jets and four leptons. Using double forward jet-tagging techniques, we derive dedicated cuts on the observable jets and charged leptons to suppress standard model backgrounds. We demonstrate that the LHC has substantial sensitivity to strong interactions in the electroweak symmetry breaking sector.
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.
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.
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.
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.
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.
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.
119193746
Computing the Adler function from the vacuum polarization function
We use a lattice determination of the hadronic vacuum polarization tensor to study the associated Ward identities and compute the Adler function. The vacuum polarization tensor is computed from a combination of point-split and local vector currents, using two flavours of O($a$)-improved Wilson fermions. Partially twisted boundary conditions are employed to obtain a fine momentum resolution. The modifications of the Ward identities by lattice artifacts and by the use of twisted boundary conditions are monitored. We determine the Adler function from the derivative of the vacuum polarization function over a large region of momentum transfer $q^2$. As a first account of systematic effects, a continuum limit scaling analysis is performed in the large $q^2$ regime.
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.
119285776
Study of the anomalous magnetic moment of the muon computed from the Adler function
We compute the Adler function on the lattice from vacuum polarization data with twisted boundary conditions using numerical derivatives. The study is based on CLS ensembles with two flavours of $O(a)$ improved Wilson fermions. We extrapolate the lattice data for the Adler function to the continuum limit and to the physical pion mass and analyze its dependence on the momentum transfer. We discuss the application of this method to the extraction of the $u,d$ contribution to $a_\mu^{\mathrm{HLO}}$.