Exploiting common-mode signals in the ALICE TPC to search for magnetic Monopoles

The magnetic monopole is a hypothetical elementary particle, beyond the Standard Model, with only one magnetic pole. It was first introduced by Paul Dirac in order to explain the quantization of electric charge. Predictions within Grand Unified Theories suggest that they are far too massive to be produced in any foreseeable accelerator. However, there are models where monopoles could appear in a mass range accessible to the LHC, with ionization equivalent ≈ 4700 minimum-ionizing particles (MIPs). The Time Projection Chamber (TPC) is the main tracking and particle identification detector of ALICE. In order to cope with the increased interaction rates of up to 50 kHz in PbPb collisions expected beyond 2020, the previously employed gated multi-wire proportional chambers have been replaced by GEM-based (Gas Electron Multiplier) readout chambers which allow for continuous readout. Due to capacitive coupling of the GEM system to the readout pads, discharging and charging of the GEM electrode induces a correlated common-mode signal with opposite polarity on all anode pads facing the GEM system in which the original signal is detected. Monopoles are expected to induce very large common-mode signals. In this contribution, a method that exploits these signals to potentially detect magnetic monopoles will be discussed.