First Physics Results from millliQan with LHC Run3 Data

by Giacomo Zecchinelli (Boston University)

Monday 29 Sept 2025, 14:30 → 16:30 Europe/Rome

Aula Conversi (Dipartimento di Fisica-Ed. Marconi)

Searching for dark matter (DM) particles is a central goal of experimental particle physics, since despite the strong astrophysical evidence for its existence, the Standard Model of elementary particles provides no explanation for it.

The MilliQan experiment is an ongoing search for millicharged particles (mCPs), which naturally arise in many extensions of the SM, which provide DM candidates via the introduction of a dark sector. The detector is located just above the CMS experiment at the LHC, where it benefits from both proximity to the interaction point, where mCPs can be produced, and significant shielding from most Standard Model backgrounds. This setup allows MilliQan to probe mCPs in a broad mass range 0.01 GeV - 45 GeV , with sensitivity to charges as low as 10−3 the charge of the electron. To cover this wide parameter space, two complementary detector designs have been realized: a bar detector, featuring long scintillating bars optimized for low-charge, low-mass sensitivity, and a slab detector with wide scintillating slabs designed for higher charges and masses mCPc scenarios.

The bar detector collected data for about two years during the LHC Run3, corresponding to an integrated luminosity of 127 fb−1. In the summer of 2024, the slab detector was fully assembled, and commissioning has since been ongoing. The current status of the experiment will be presented, including results from the 2024 bar detector dataset, as well as recent commissioning studies of the slab detector and its early 2025 data.