Marc Schlegel

Semi-inclusive deep inelastic scattering at small transverse momentum

We study the cross section for one-particle inclusive deep inelastic scattering off the nucleon for low transverse momentum of the detected hadron. We decompose the cross section in terms of structure functions and calculate them at tree level in terms of transverse-momentum-dependent parton distribution and fragmentation functions. Our results are complete in the one-photon exchange approximation at leading and first subleading twist accuracy, with both beam and target polarization.

Generalized parton correlation functions for a spin-0 hadron

The fully unintegrated, off-diagonal quark-quark correlator for a spin-1/2 hadron is parameterized in terms of so-called generalized parton correlation functions. Such objects, in particular, can be considered as mother distributions of generalized parton distributions on the one hand and transverse momentum dependent parton distributions on the other. Therefore, our study provides new, model-independent insights into the recently proposed nontrivial relations between generalized and transverse momentum dependent parton distributions. We find that none of these relations can be promoted to a model-independent status. As a by-product we obtain the first complete classification of generalized parton distributions beyond leading twist. The present paper is a natural extension of our previous corresponding analysis for spin-0 hadrons.

Dilepton production from polarized hadron hadron collisions

In this paper we present a comprehensive formalism for dilepton production from the collision of two polarized spin-

Parameterization of the quark-quark correlator of a spin- 1/2 hadron

\frac{1}{2}

Linearly Polarized Gluons and the Higgs Transverse Momentum Distribution

hadrons by identifying the general angular distribution of the cross section in combination with a complete set of structure functions. The various structure functions are computed in the parton model approximation where we mainly consider the case when the transverse momentum of the dilepton pair is much smaller than its invariant mass. In this kinematical region dilepton production can be described in terms of transverse momentum dependent parton distributions.

Probing gluonic spin-orbit correlations in photon pair production.

Abstract The general parameterization of the quark–quark correlation function for a spin- 1 2 hadron is considered. The presence of the Wilson line ensuring color gauge invariance of the correlator induces structures that were not given explicitly in the existing literature. In particular, the general form of the transverse momentum dependent correlator entering various hard scattering processes is derived. In this case two new time-reversal odd parton distributions appear at the twist-3 level.

Accessing the transverse dynamics and polarization of gluons inside the proton at the LHC

We study how gluons carrying linear polarization inside an unpolarized hadron contribute to the transverse momentum distribution of Higgs bosons produced in hadronic collisions. They modify the distribution produced by unpolarized gluons in a characteristic way that could be used to determine whether the Higgs boson is a scalar or a pseudoscalar particle.

Twist-2 generalized transverse-momentum dependent parton distributions and the spin/orbital structure of the nucleon

We consider photon pair production in hadronic collisions at large mass and small transverse momentum of the pair, assuming that factorization in terms of transverse-momentum dependent parton distributions applies. The unpolarized cross section is found to have azimuthal angular dependencies that are generated by a gluonic version of the Boer-Mulders function. In addition, the single transversely polarized cross section is sensitive to the gluon Sivers function. We present simple numerical estimates for the Boer-Mulders and Sivers effects in diphoton production at RHIC and find that the process would offer unique opportunities for exploring transverse-momentum dependent gluon distributions.

Single-spin asymmetries in inclusive deep inelastic scattering and multiparton correlations in the nucleon

We argue that the study of heavy quarkonia, in particular that of Υ, produced back to back with an isolated photon in pp collisions at the LHC is the best - and currently unique - way to access the distribution of both the transverse momentum and the polarization of the gluon in an unpolarized proton. These encode fundamental information on the dynamics of QCD. We derive analytical expressions for various transverse-momentum distributions that can be measured at the LHC and which allow for a direct extraction of the aforementioned quantities. To assess the feasibility of such measurements, we evaluate the expected yields and the relevant transverse-momentum distributions for different models of the gluon dynamics inside a proton.

Determining the Higgs Spin and Parity in the Diphoton Decay Channel

K. Kanazawa, C. Lorcé, A. Metz, B. Pasquini, M. Schlegel 1 Graduate School of Science and Technology, Niigata University, Ikarashi, Niigata 950-2181, Japan Department of Physics, Barton Hall, Temple University, Philadelphia, PA 19122, USA 3 IPNO, Université Paris-Sud, CNRS/IN2P3, 91406 Orsay, France and IFPA, AGO Department, Université de Liège, Sart-Tilman, 4000 Liège, Belgium Dipartimento di Fisica, Università degli Studi di Pavia, and Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, I-27100 Pavia, Italy Institute for Theoretical Physics, Tübingen University, Auf der Morgenstelle 14, D-72076 Tübingen, Germany