The prospect of charm quark magnetic moment determination
A. S. Fomin, S. Barsuk, A. Yu. Korchin, E. Kou, V. A. Kovalchuk, M. Liul, A. Natochii, E. Niel, P. Robbe, A. Stocchi
Abstract
Abstract In this paper, we discuss the theoretical framework and the experimental measurements of the magnetic moment of the charmed baryons. We first review the theoretical predictions of the $$\varLambda _c^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>Λ</mml:mi><mml:mi>c</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math> magnetic moment and show that the measurements of the magnetic moments of other charmed baryons, such as $$\varXi _{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>Ξ</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math> , allow to perform detailed spectroscopy studies. The magnetic moment of the charm quark can be determined using radiative charmonium decay, which can be compared to the $$\varLambda _c^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>Λ</mml:mi><mml:mi>c</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math> magnetic moment within theoretical models. The present results show a tension with majority of theoretical predictions. The magnetic moment of the charmed baryons could potentially be measured directly, using bent-crystal experiments at LHC. The possibility to measure precisely the magnetic moments of charmed 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 $$\varLambda _c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>Λ</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math> baryons as a function of crystal orientation. We found a special orientation of the crystal that gives the opportunity to measure the $$\varLambda _c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>Λ</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math> 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.