A
bstract
In this paper we discuss the possibility of measuring the anomalous magnetic and electric dipole moments of the
τ
lepton. The method consists in studying the spin precession induced by the ...strong effective magnetic field inside channels of a bent crystal with a dedicated setup at the CERN Large Hadron Collider.
A
bstract
In this paper we revisit the idea of measuring the magnetic dipole moments of the charm baryons and, in particular, of
Λ
c
+
by studying the spin precession induced by the strong effective ...magnetic field inside the channels of a bent crystal. We present a detailed sensitivity study showing the feasibility of such an experiment at the LHC in the coming years.
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
Λ
c
+
magnetic ...moment and show that the measurements of the magnetic moments of other charmed baryons, such as
Ξ
c
, 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
Λ
c
+
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
Λ
c
baryons as a function of crystal orientation. We found a special orientation of the crystal that gives the opportunity to measure the
Λ
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.
We investigate effects of CP symmetry violation in the decay of a scalar particle
X
(the Higgs boson) into two off-mass-shell
Z
bosons both decaying into a fermion–antifermion pair,
. The most ...general form of the amplitude of the transition
X
→
Z
1
*
Z
2
*, wherein the boson
X
may not have definite CP parity, is considered. The applicability limits of the narrow-
Z
-width approximation used in obtaining differential widths of the decay under consideration are determined. Various observables connected with the structure of the amplitude of the decay
X
→
Z
1
*
Z
2
* are studied. These observables are analyzed in the Standard Model as well as in models conceding indefinite CP parity of the Higgs boson. An experimental measurement of angular and invariant mass distributions of the decay
at the LHC can give information about the CP properties of the Higgs boson and its interaction with the
Z
boson.
An important problem in the particle physics is interaction of the Higgs boson with the fermions. It is in the processes, which involve \(h f f \) interaction, the manifestations of \(CP\) violation ...are possible. This in turn can be helpful in solving the problem of the dominance of matter over antimatter in the Universe. In this connection, in the present paper, the effect of longitudinal polarization of leptons and quarks produced in the decay of the Higgs boson is investigated and calculated. We consider the case in which the Higgs boson interacts with fermions via a mixture of scalar and pseudoscalar couplings. Under this assumption, the longitudinal polarization can acquire non-zero values due to imaginary part of loop corrections to tree-level amplitudes. This polarization is a direct signature of the \(CP\) violation in the Higgs sector. Effects of the longitudinal polarization of \(\tau\) leptons on the energy distribution of the pions in the two-step Higgs-boson decay \(h \to \tau^- \tau^+ \to \pi^- \nu_\tau \pi^+ \bar{\nu}_\tau\) are also studied, and the energy asymmetry with corresponding moments are calculated.
The production of lepton pairs in the Higgs boson decay \(h \to \ell^+ \ell^- \gamma\) is studied. The emphasis is put on the structure of the Higgs boson interaction with the fermions. This ...interaction is chosen as a mixture of the scalar and pseudo-scalar couplings, and, in addition, it is supposed to be non-Hermitian. We study prediction of this model for the observables in the \(h \to \ell^+ \ell^- \gamma\) decay for the \(e^+ e^-\), \(\mu^+ \mu^-\) and \(\tau^+ \tau^-\) pairs. The differential decay width and lepton forward-backward asymmetry are calculated as functions of the dilepton invariant mass for several sets of \(h f \bar{f}\) coupling constants. The influence of non-Hermitian \(h f \bar{f}\) interaction on the forward-backward asymmetry is studied, and large influence of a possible non-Hermiticity of the Higgs interaction with the top quarks on forward-backward asymmetry for \(e^+ e^-\) and \(\mu^+ \mu^-\) pairs is stressed.
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