General CPT-even dimension-five nonminimal couplings between fermions and photons yielding EDM and MDM

Araujo, Jonas B.; Casana, R.; Ferreira, Manoel M.

doi:10.1016/j.physletb.2016.06.070

Cited by 33 publications

(22 citation statements)

References 118 publications

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“…The continuous investigation of SME in flat spacetime has deepened into the non-minimal (power-counting nonrenormalizable) sector [6], and recently even stepped into the region of interacting LV perturbations [7]. In curved spacetime, the LV studies encompass not only pure gravity sector [8], but also matter-gravity couplings, where * Electronic address: blueseacat@126.com certain LV effects may be countershaded by the extremely weak g-factor [9].…”

Section: Introductionmentioning

confidence: 99%

The CPT-violating effects on neutrons’ gravitational bound state

Xiao

Shao

2020

J. Phys. G: Nucl. Part. Phys.

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In this paper, the CPT-violating (CPTV) spin interactions on neutron's gravitational bound state are studied. The helicity-dependent phase evolution due to σ • b and σ • ˆ p couplings is transparently demonstrated with analytical solutions. The consequent phenomena include not only spin precession and the azimuthal angle θ− and φ−dependent probability variation, but also transition-frequency shifts between different gravitational bound states. The θ and φ time-dependences due to the Earth motion may lead to sidereal variation of the probability profile, a clear signal of Lorentz violation. We also utilize the gravitational transition frequencies measured precisely in the qBounce experiment [26] to obtain the rough bound | b| < 6.9×10 −21 GeV. Incorporating known systematic errors or using polarized neutron beams may lead to more robust and tighter constraints.

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Section: Introductionmentioning

confidence: 99%

The CPT-violating effects on neutrons’ gravitational bound state

Xiao

Shao

2020

J. Phys. G: Nucl. Part. Phys.

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“…For over fifteen years, various experimental tests within particle physics and gravity have been carried out producing a high number of constraints on CPT and Lorentz violation [24]. In particular, Lorentz-violating nonminimal models have also been proposed to look for unusual electromagnetic interactions between fermions and photons [25][26][27][28][29] and altered interactions in the electroweak sector [30].…”

Section: Introductionmentioning

confidence: 99%

Vacuum Cherenkov radiation for Lorentz-violating fermions

Schreck

2017

Phys. Rev. D

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The current work focuses on the process of vacuum Cherenkov radiation for Lorentzviolating fermions that are described by the minimal Standard-Model Extension (SME). To date, most considerations of this important hypothetical process have been restricted to Lorentz-violating photons, as the necessary theoretical tools for the SME fermion sector have not been available. With their development in a very recent paper, we are now in a position to compute the decay rates based on a modified Dirac theory. Two realizations of the Cherenkov process are studied. In the first scenario, the spin projection of the incoming fermion is assumed to be conserved, and in the second, the spin projection is allowed to flip. The first type of process is shown to be still forbidden for the dimensionful a and b coefficients where there are strong indications that it is energetically disallowed for the H coefficients, as well. However, it is rendered possible for the dimensionless c, d, e, f , and g coefficients. For large initial fermion energies, the decay rates for the c and d coefficients were found to grow linearly with momentum and to be linearly suppressed by the smallness of the Lorentz-violating coefficient where for the e, f , and g coefficients this suppression is even quadratic. The decay rates vanish in the vicinity of the threshold, as expected. The decay including a fermion spin flip plays a role for the spin-nondegenerate operators and it was found to occur for the dimensionful b and H coefficients as well as for the dimensionless d and g. The characteristics of this process differ much from the properties of the spin-conserving one, e.g., there is no threshold. Based on experimental data of ultra-high-energy cosmic rays, new constraints on Lorentz violation in the quark sector are obtained from the thresholds. However, it does not seem to be possible to derive bounds from the spin-flip decays. This work reveals the usefulness of the quantum field theoretic methods recently developed to study the phenomenology of high-energy fermions within the framework of the SME.

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“…An interesting discussion concerning the overlapping of some bounds with others in the literature is found in Ref. 9. For a discussion on the sidereal variations, to which the LV parameters are subject, see Refs.…”

Section: The Full Nonrelativistic Hamiltonian Ismentioning

confidence: 97%

“…In this work, a new class of dimension-five nonminimal couplings is proposed and examined with respect to the possible generation of an EDM and magnetic dipole moment (MDM), 9 having the hermiticity as the main criterion to be observed.…”

Section: 7mentioning

confidence: 99%

General Electromagnetic Nonminimal Couplings in the Dirac Equation

Araujo¹,

Casana²,

Ferreira³

2017

CPT and Lorentz Symmetry

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We examine a new class of CPT-even and dimension-five nonminimal interactions between fermions and photons, deprived of higher-order derivatives, yielding electric dipole moment and magnetic dipole moment in the context of the Dirac equation. These couplings are Lorentz-violating nonminimal structures, composed of a rank-2 tensor, the electromagnetic tensor, and gamma matrices, being addressed in its axial and non-axial hermitian versions. We use the electron's anomalous magnetic and electric dipole moment measurements to reach upper bounds of 1 part in 10 11 and 10 16 GeV −1 .The Standard Model (SM) structure allows for C, P, and T violations (and combinations) as long as CPT symmetry is preserved. Among the most important tests for physics beyond the SM is the search for the electric dipole moment (EDM) of particles in connection with the strong CP problem.1,2 The EDM nonrelativistic interaction term has the form d(σ · E), with E, σ and d as the electric field, the spin operator, and the EDM modulus, respectively. This interaction violates both P and T symmetries, P (σ ·E) → −(σ ·E), T (σ·E) → −(σ·E), but preserves C and CPT symmetries. Lorentz-violating nonminimal couplings in the context of the Dirac equation that engender EDM at tree level can be stringently constrained by EDM data.3-5 Theories endowed with Lorentz violation are a possible route for physics beyond SM that has been intensively studied in the latest years, mainly in the context of the Standard-Model Extension (SME). 6,7Connections between LV theories and EDM physics have been addressed in Ref. 8. In this work, a new class of dimension-five nonminimal couplings is proposed and examined with respect to the possible generation of an EDM and magnetic dipole moment (MDM), 9 having the hermiticity as the main criterion to be observed.

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General CPT-even dimension-five nonminimal couplings between fermions and photons yielding EDM and MDM

Cited by 33 publications

References 118 publications

The CPT-violating effects on neutrons’ gravitational bound state

The CPT-violating effects on neutrons’ gravitational bound state

Vacuum Cherenkov radiation for Lorentz-violating fermions

General Electromagnetic Nonminimal Couplings in the Dirac Equation

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