# Graduate Student Lunch Club

The CTP Lunch Club meets most Fridays at 12:30 (provided that there are sufficient speakers).

**About the Seminar**

The seminars are designed for graduate students and should be accessible to all students. First year students are particularly encouraged to attend so that they may learn about research being performed in the CTP.

Email notification of the club will be sent to the ctp-all, ctp-postdocs and ctp-students email lists as appropriate. If you wish to speak, or have suggestions about speakers and/or possible workshop topics, please contact the organizers: Wenjie Gong, Angus Lowe, Richard Allen, Rachel Stein, Manu Srivastava

Friday, February 3**Stella Schindler**, MIT**Title:** Factorization Enabling Lattice Calculations of TMDs**Abstract:** Transverse momentum distributions (TMDs) encode the three-dimensional momentum structure of quarks and gluons inside hadrons. Global fits to experimental data exhibit large uncertainties for non-perturbative parton momenta, a kinematic region where lattice QCD is typically well-positioned to provide complementary information. Unfortunately, TMD dynamics are dominated by the lightcone, which induces a so-called sign problem, an obstacle to numerics that is NP-hard in the general case. To circumvent this issue, lattice theorists typically project Wilson lines appearing in TMD matrix elements from a lightcone path onto an equal-time slice. We derive a factorization formula connecting the resulting lattice-calculable equal-time distributions (quasi-TMDs) to the TMDs that appear in cross-sections (Collins scheme). This formula holds at leading power to all orders in α_s, for all spins and parton flavors. The factorization establishes that lattice and physical TMDs share the same IR physics, and opens the path towards computing gluon TMDs.