Polarized Fragmentation Functions

In this talk I present a review on the theoretical status of polarized fragmentation functions and the prospects for conceivable future semi-inclusive deep-inelastic scattering and proton-proton collision experiments to measure them.Comment: Talk at the Electron Polarized Ion Collider Workshop (EPIC99), at IUCF, Bloomington, IA, April 1999, 15 pp, 6 fig

Thermodynamics and Spin Tunneling Dynamics in Ferric Wheels with Excess Spin

We study theoretically the thermodynamic properties and spin dynamics of a class of magnetic rings closely related to ferric wheels, antiferromagnetic ring systems, in which one of the Fe (III) ions has been replaced by a dopant ion to create an excess spin. Using a coherent-state spin path integral formalism, we derive an effective action for the system in the presence of a magnetic field. We calculate the functional dependence of the magnetization and tunnel splitting on the magnetic field and show that the parameters of the spin Hamiltonian can be inferred from the magnetization curve. We study the spin dynamics in these systems and show that quantum tunneling of the Neel vector also results in tunneling of the total magnetization. Hence, the spin correlation function shows a signature of Neel vector tunneling, and electron spin resonance (ESR) techniques or AC susceptibility measurements can be used to measure both the tunneling and the decoherence rate. We compare our results with exact diagonalization studies on small ring systems. Our results can be easily generalized to a wide class of nanomagnets, such as ferritin.Comment: 15 pages, 5 figure

Transversely polarized Drell-Yan asymmetry AT T at NLO

We present the first fully differential next-To-leading order QCD calculation for lepton production in transversely polarized hadronic collisions, p↑p↑→±X, where the lepton arises from the decay of an electroweak gauge boson. The calculation is implemented in the Monte-Carlo like code che that already includes the unpolarized and longitudinally polarized cross sections and may be readily used to perform a comparison to experimental data and to extract information on the related parton distributions. We analyze the perturbative stability of the cross-section and double spin asymmetry ATT at RHIC kinematics. We find that the QCD corrections are non-negligible even at the level of asymmetries and that they strongly depend on the lepton kinematics. Furthermore, we present two scenarios for transversely polarized parton distributions, based on the de Florian-Sassot-Stratmann-Vogelsang (DSSV) set of longitudinally parton densities and fully evolved to NLO accuracy, that can be used for the evaluation of different observables involving transverse polarization.Fil: de Florian, Daniel Enrique. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología. Centro Internacional de Estudios Avanzados; Argentina. Tübingen University; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Higgs Boson Pair Production at Next-to-Next-to-Leading Order in QCD

We compute the next-to-next-to-leading order QCD corrections for Standard Model Higgs boson pair production inclusive cross section at hadron colliders within the large top-mass approximation. We provide numerical results for the LHC, finding that the corrections are large, resulting in an increase of ${\cal O}(20$ with respect to the next-to-leading order result at c.m. energy $\sqrt{s_H}=14\,\text{TeV}$. We observe a substantial reduction in the scale dependence, with overlap between the current and previous order prediction. All our results are normalized using the full top- and bottom-mass dependence at leading order. We also provide analytical expressions for the K factors as a function of $s_H$

Peer advice in a tax-evasion experiment

We examine peer effects in a tax-evasion experiment where subjects receive either advice or compliance data from participants with either above-median or below-median compliance rates in a control treatment. Both types of information on peer behavior yield significantly lower compliance rates than in the control group without any kind of information about peers. Receiving advice or compliance data from the pool of low-compliance participants yields the lowest compliance rates. We show that advice has a slightly bigger impact than observing the compliance of others and that subjects focus on payoff maximization rather than on tax morale when giving advice.Tax evasion, advice, experiments, social influence, peer effects

Jet production in Polarized DIS at NNLO

We present the NNLO calculation for single-inclusive jet production in polarized DIS $\vec{e}\vec{p} \rightarrow {\rm jet} +X$. We perform the computation based on the Projection-to-Born method by combining our recent NLO result for di-jet production in polarized DIS along with the NNLO coefficients for the inclusive cross section. In this way, we achieve NNLO accuracy in a fully exclusive way for single-jet observables, the first time for a polarized cross section. We study the perturbative stability and phenomenological consequences of the QCD corrections for Electron Ion Collider kinematics.Comment: 5 pages, 3 figure