Lorentz andCPTviolation in top-quark production and decay

Abstract

The prospects are explored for testing Lorentz and CPT symmetry in the top-quark sector. We present the relevant Lagrange density, discuss physical observables, and describe the signals to be sought in experiments. For top-antitop pair production via quark or gluon fusion with subsequent semileptonic or hadronic decays, we obtain the matrix element in the presence of Lorentz violation using the narrow-width approximation. The issue of testing CPT symmetry in the top-quark sector is also addressed. We demonstrate that single-top production and decay is well suited to a search for CPT violation, and we present the matrix elements for single-top production in each of the four tree-level channels. Our results are applicable to searches for Lorentz violation and studies of CPT symmetry in collider experiments, including notably high-statistics top-antitop and single-top production at the Large Hadron Collider.

One-loop correction to the photon velocity in Lorentz-violating QED

“…The conditions (33), and |y| ≪ 1, are valid for this bound. The bound (34) is at 5 orders of magnitude better than the direct collider bound from Tevatron [30] (see also the prospect for a collider bound for LHC [31]). For light quarks this analysis fails; one should consider the case y ≫ 1.…”

“…The formula (31) is valid under the condition |y| ≪ 1, which leads to |c f −c γ | ≪ (m f /150 MeV) 2 . This condition, combined with (31), is satisfied at least for leptons.…”

Top hadrons in Lorentz-violating field theory

“…There are direct measurements of the t −t production cross section [17], with sensitivities to the coefficients of dimension-4 SME operators at the 10 −1 − 10 −2 level. The fact that t quarks do not exist as external states is not an issue for these measurements, because the SME coefficients can affect the physical cross sections not primarily through the kinematics but also directly via the dynamical matrix element for the t −t production process [18]. The other bound arises from radiative corrections.…”

Lorentz and CPT violation in partons

“…Our efforts here to explore spin-independent SME effects in the quark sector extend those in the literature, including studies of single and pair production of t quarks at Fermi National Accelerator Laboratory (Fermilab) and at the LHC [22][23][24], applications of chiral perturbation theory [25][26][27][28][29], estimates of attainable sensitivities from DIS [30][31][32], and related investigations [33,34]. Spin-independent SME coefficients for CPT violation in the quark sector can also be constrained using neutral-meson interferometry [35,36] via oscillations of kaons [37][38][39][40][41] and of D, B d , and B s mesons [42][43][44][45][46][47][48].…”