The TWOCRYST experiment

Experimental setup

The need for a double-crystal setup in the LHC stems from the desire to measure the electromagnetic dipole moments of short-lived charmed particles. Due to their short lifetimes, such as $2^{-13}$ s for the $\Lambda_c^+$, inducing measurable spin precession using conventional magnets is not feasible. To solve this issue, a bent crystal with an equivalent of hundreds of Tm is used to induce precession. Bent crystals can deflect charged particles by planar channelling between the atomic plane. In particular, one bent crystal will be used for magnetic precession, while another one will be used to extract a beamlet from the circulating beam.

In the double-crystal arrangement, the first crystal (TCCS: Target Collimator Crystal for Splitting) splits halo particles from the circulating beam onto an in-vacuum target to produce, amongst other products, the $\Lambda_c^+$ particles of interest. Channeling and deflecting these particles by means of a second bent crystal (TCCP: Target Collimator Crystal for Precession) induces spin precession, enabling its measurement with a dedicated detector downstream. The particles exiting the TCCP would than be detected from two 2D detectors, VELO silicon pixel sensor and Fibre tracker recovered from the ATLAS-ALFA experiment.

The entire setup is placed in Insertion Region 3 of the LHC on the Beam 2 pipeline.

Scientific agenda

Here is the scientific agenda. Stay tuned.