The prospect of charm quark magnetic moment determination

• Main Authors: Fomin, A. S, Barsuk, S, Korchin, A. Yu, Kovalchuk, V. A, Kou, E, Liul, M, Natochii, A, Niel, E, Robbe, P, Stocchi, A
• Format: Journal Article
• Language: English
• Published: 10-09-2019
• Subjects: Physics - High Energy Physics - Experiment; Physics - High Energy Physics - Phenomenology
• DOI: 10.48550/arxiv.1909.04654

In this paper, we discuss the theoretical framework and the experimental
measurements of the magnetic moment of the charm baryons. The $\Lambda_c^+$
magnetic moment is particularly interesting since it is equal to the magnetic
moment of the charm quark. The measurements of the magnetic moments of other
charm baryons, such as $\Xi_c$, allow to perform detailed spectroscopy studies.
The magnetic moment of the $\Lambda_c$ can be determined using radiative
charmonium decay and the present results show a tension with majority of
theoretical predictions. As recently pointed out, the magnetic moment of the
charm baryons can be directly measured using bent-crystal experiments at LHC.
The possibility of precisely measure the magnetic moments of charm baryons
needs precise measurement of their polarisation and weak decay parameters. In
this paper, we revisit the formalism of the angular analysis needed for these
measurements and make a detailed evaluation of initial polarisation of
deflected $\Lambda_c$ baryons as a function of crystal orientation. We found a
special orientation of the crystal that gives the opportunity to measure the
$\Lambda_c$ dimensionless electric dipole moment almost with the same precision
as its $g$-factor, which is more than an order of magnitude more efficient than
suggested before. In conclusion, we stress the importance to perform precise
measurements of initial polarisation and weak decay parameters of $\Lambda_c$
baryon to effectively compare the direct and from decay measurements of
magnetic moments.