10/31/2018

Extraction of partonic unpolarized TMDs and Sivers function 

Filippo Delcarro, University of Pavia
11:00 AM Wednesday, Knudsen 4-134

A recent extraction of the Sivers function from azimuthal asymmetries in semi-inclusive deep inelastic scattering (SIDIS) will be presented. This analysis takes into account contributions of transverse momentum dependent (TMD) evolution and features a parametrization of unpolarized TMDs determined directly from data. Then, also an overview of a global extraction of TMDs from unpolarized SIDIS, Drell-Yan and Z boson production data will be given. Finally, a comparison of these studies with results obtained from other collaborations will be discussed, together with future outlooks for the phenomenological analysis of TMDs.

10/17/2018

Nucleon 3D/spin structure: towards the precision era

Miguel G. Echevarria, INFN/Pavia
12:00 PM Wednesday, Knudsen 4-134

I will first review the formalism of transverse-momentum-dependent factorization, mainly from the effective field theory points of view, which gives access to transverse-momentum-dependent functions (TMDs). Then, I will summarize the current status of higher-order perturbative QCD calculations of TMD evolution/resummation. Finally, I will present new results for the QED corrections to the evolution of TMDs.

08/10/2018

The (spin) structure of the nucleon beyond the Parton Model

Marc Schlegel, New Mexico State University
12:00 PM Friday, Knudsen 4-134

I will provide a brief review on the structure of the nucleon. In particular, I will discuss methods to access the nucleon structure beyond the parton model. This gives more detailed information on the 3-d structure as well as dynamics of partons in the nucleon. One generalization of the collinear parton model is Transverse Momentum Dependent (TMD) factorization. I will focus on gluon TMD distributions that may be constraint by data taken at the LHC. Another way to get more insight into the nucleon structure is to study transverse spin effects. I will present some examples to illustrate these effects.

06/01/2018

Probing TeV physics with precision calculations of nucleon structure using lattice QCD

Rajan Gupta, Los Alamos National Laboratory
12:15 PM Friday, Knudsen 4-134

This talk will present a number of high precision results on matrix elements of quark bilinear operators between nucleon states using lattice QCD. From these, we extract a number of exciting quantities, at the intersection of nuclear and particle physics. We show that the axial charge g_A, a fundamental parameter encapsulating the weak interaction of nucleons, is calculated with a few percent accuracy. Results for the scalar and tensor charges, g_S and g_T, which combined with precision neutron decay distribution probe novel scalar and tensor interactions at the TeV scale. Vector form factors are probed in electron scattering, while axial vector form factors are used in the calculation of the cross-section of neutrinos on nuclear targets. These energy dependent cross-sections are needed to determine the neutrino flux, an important systematic in neutrino oscillation experiments. Finally we will present results for flavor diagonal charges that provide the contribution of the quark spin to the nucleon spin, the quark EDM to the neutron EDM, and needed to determine the cross-section of dark matter with nuclear targets.

04/05/2018

Resummation of the D-parameter

Andrew Larkoski, Reed College
1:30 PM Thursday, Knudsen 4-134

The D-parameter is among the oldest and most experimentally well-studied hadronic event shape observables in electron-positron collisions.  Despite this, there does not exist a prediction for the D-parameter from perturbative QCD which captures all logarithmic corrections to any formal accuracy. In this talk, I will discuss our approach to this problem and its resolution, which utilizes recent advances in the field of jet substructure.

03/01/2018

Mini-jet Clusters and Mini-Dijet Clusters in High-Energy pp Collisions

Cheuk-Yin Wong, Oak Ridge National Lab
1:30 PM Thursday, Knudsen 4-134

Mini-jets and mini-dijets provide useful information on multiple parton interactions in the low-pT region. We attempt to develop a clustering algorithm to identify minijets by using the k-means clustering method, with a cluster-number selection principle. Upon testing the algorithm using minimum-bias events generated by PYTHIA, for pp collision at sqrt{s}=200 GeV, we find that multiple mini-jet-like and mini-dijet-like clusters of low pT hadrons occur in high multiplicity events. However similar clustering properties are also present for particles produced randomly in a finite pseudo-rapidity and azimuthal angle space. The ability to identify mini-jets and mini-dijets may need to depend on the additional independent assessment of the dominance of the parton-parton hard-scattering process in the low-pT region.

02/08/2018

From the QCD phase diagram to jet quenching in heavy ion collisions

Jasmine Brewer, MIT
1:30 PM Thursday, Knudsen 4-134

In this talk, I will discuss a new observable for mapping the QCD phase diagram at RHIC, and a model for understanding the effects of dynamics in the quark gluon plasma on jet energy loss. In the first part of this talk, I will demonstrate that at RHIC energies around 20 GeV the non-trivial dependence of baryon density on rapidity can give rise to fluctuation measures which are non-monotonic in rapidity. I will propose an observable that exaggerates the signature of criticality in the rapidity dependence, and show that this kind of "rapidity scan" provides complementary signatures of criticality to those from the beam energy scan. In the second part of this talk, I will demonstrate that velocities and velocity gradients in the medium have a large effect on energy loss in a holographic model of jets. I will show that including the effects of velocities and velocity gradients in a reasonable model of the medium increases the stopping distance of high energy jets by as much as a factor of two.

01/08/2018

Probe Quark-Gluon-Plasma with Heavy Quarks in sPHENIX Experiment at Relativistic Heavy Ion Collider

Ming Liu, Los Alamos National Laboratory
1:00 PM Monday, Knudsen 4-134

The 2015 US Nuclear Physics Long Range Plan calls for a state-of-the-art jet and upsilon detector at RHIC, called sPHENIX, to study the microscopic nature of the QGP, complementing similar studies at the CERN LHC. The sPHENIX detector will provide precision vertexing, tracking and full calorimetry over pseudo-rapidity |eta| < 1.1 and full azimuth at the full RHIC collision rate, delivering unprecedented data sets for jet and upsilon measurements at RHIC. This will enable the three pillars of the sPHENIX physics program, i.e., 1) studies of jet structure modifications, 2) measurements of heavy-flavor tagged jet production and 3) precision upsilon spectroscopy. In this talk I will present an overview of the sPHENIX heavy flavor physics program, from detector design, expected construction and running schedule and planned physics program.