Abstract
The electric and magnetic dipole moment of charm and bottom baryons can be measured for the first time by using bent crystal technology at the LHC. The experimental method, proposed in recent years, suffers from limited statistics, which dominates the uncertainty of the measurement. In this work, we present an alternative experimental layout, based on the use of crystal lenses, that improves the trapping efficiency by about a factor 15 (35) for a 2-cm (5-mm) target with respect to the nominal layout, with plain crystal faces. The efficiencies are evaluated taking into account the constraints from the LHC machine, and the technical challenges to realize this novel experimental method are discussed.
Highlights
Searches for permanent electric dipole moments (EDMs) of particles provide stringent constraints on theories of CP violation beyond the Standard Model
The description of charm and bottom baryon EDMs is being developed within the framework of baryon chiral perturbation theory [12,13], while input from lattice QCD is still necessary for the interpretation of the measurement in terms of quark effective operators
Provided that the initial particle direction is parallel to the atomic planes, and the momentum of the particle is below some threshold, determined by the crystal bending radius, the particle is trapped between the atomic planes, and it follows the curved trajectory of the bent crystal according to a probability distribution in a process called channeling [18]
Summary
Searches for permanent electric dipole moments (EDMs) of particles provide stringent constraints on theories of CP violation beyond the Standard Model. While the Lindhard angle depends on the crystal material and the particle energy, and cannot be increased to trap particles in a wider range of directions, the overall geometry of the setup can be composed in such a way that the atomic planes are laid out in different directions, matching the initial angle of more of the produced particles [19,20] The use of crystal lenses for spin precession experiments represents a new application of the bent-crystal channeling technique, which was tested at many accelerators [23,25,26,27,28] and routinely exploited since the 80’s at IHEP for beam delivery to particle physics experiments [29] at intensities up to 1012 proton/s At this intensity, the channeling efficiency reached 85% [30].
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