Regular joint theory/experimental seminars are at 4:10pm on Tuesday afternoons. They are usually listed in the overall department compendium linked to the physics department home page. At times, this list is not accurate or is not up to date, so it is always best to use the HEFTI seminar and visitor schedule.
We also have a HEFTI Joint Theory seminar series. These seminars are currently scheduled at 1:30 pm, Mondays. They are normally more theoretical in nature than the joint seminars. Sometimes they are also properly announced on the seminars link located on the physics department home page. However, the best place to check is the unified schedule: HEFTI seminar and visitor schedule.
We also have an LHC lunch seminar/discussion once a week. These are Tuesdays at 12:30pm. At these meetings we will often have an invited speaker. On other occasions, the lunches will be devoted to discussing a paper or two from the recent literature. Research projects being pursued by members of the HEFTI group are often discussed. Some meetings are used for joint brain storming of the theory and experimental groups or possibly joint discussions between the cosmology and high energy groups. These are also usually placed on the unified schedule: HEFTI seminar and visitor schedule.
Some of us also attend seminars at LBL/Berkeley and SLAC/Stanford. For schedule and times of these seminars go to the Physics Links page.