9,475 research outputs found
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ring systems, in which one of the Fe (III) ions has been replaced by a dopant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 MartĂn. Escuela de Ciencia y TecnologĂa. Centro Internacional de Estudios Avanzados; Argentina. TĂĽbingen University; Alemania. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
Jet Production with Polarized Beams at Next-to-Leading Order
Jet production cross-sections in polarized proton-proton and electron-proton
collisions are studied to next-to-leading order accuracy. Phenomenological
results are presented for RHIC and HERA kinematics.Comment: 3 pages, 4 figures, talk given at the DIS99 Workshop, Zeuthen,
Germany, April 19-23, 199
Two-loop virtual corrections to Higgs pair production
We present the two-loop virtual corrections to Standard Model Higgs boson
pair production via gluon fusion in the heavy top quark limit. Based
on this result, we evaluate the corresponding cross section at the LHC at 14
TeV in the next-to-next-to-leading order soft-virtual approximation. We find an
inclusive K-factor of about 2.4, resulting in an increase close to 23% with
respect to the previous available calculation at next-to-leading order. As
expected, we observe a considerable reduction in the renormalization and
factorization scale dependence
Next-to-Next-to-Leading Order QCD Corrections to Higgs Boson Pair Production
We present the Higgs boson pair production cross section at
next-to-next-to-leading order in QCD within the large top-mass approximation.
Numerical results for the LHC are provided, finding an increase of O(20%) with
respect to the previous order prediction and a substantial reduction in the
scale dependence. We normalize our results using the full top- and bottom-mass
dependence at leading order.Comment: Proceedings of 'Loops & Legs 2014', Weimar (Germany), April/May 201
- …