Neutron Electric Dipole Moment on the Lattice

Abstract

Abstract. For the neutron to have an electric dipole moment (EDM), the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.

The phenomenology of electric dipole moments in models of scalar leptoquarks

“…The contributions from the strange CEDM are usually considered to vanish, once a Peccei-Quinn mechanism is used to solve the strong CP problem [62], but this has not been fully resolved [66]. Contributions from the Weinberg operator appear with large uncertainties, O(100%), based on a combination of QCD sum-rules [67] and naive-dimensionalanalysis, Lattice-QCD calculations are in progress to reduce the uncertainties [68][69][70]. Very little is known about the contributions of the four-quark operators and we use the NDA estimate d n,p = O(Λ χ /(4π) 2 ) Im C (1,8) quqd with an O(100%) uncertainty [49].…”

Preface

“…Talks dedicated to specific topics ranged from the discussion of B-physics anomalies in the flavour sector [40,41] or the determination of α s from different perspectives [55,56], to the status and evolution of QCD codes for high-performance computing [59], this year with special emphasis on the new KNL architecture (Intel) that will play an important role in the next generation of supercomputers. Progress in the calculation of notoriously difficult quantities like the nucleon axial charge [45], the nucleon EDM [51], the muon anomalous magnetic moment [62,63], or the gluonic structure of nuclei [52] has also been reported. Another topic that has drawn a lot of attention recently is the computation of quasi-parton distribution functions; a plenary session trying to assess the impact of lattice results in this field has been presented during the conference [43].…”

Neutron Electric Dipole Moment from Beyond the Standard Model

“…The quark chromo-EDM operator is a quark bilinear, so its ME can be calculated using the Schwinger source method as described in previous proceedings [17,18]. All the calculations presented here were done with Clover fermions on a MILC generated L 3 × T = 24 3 × 64 HISQ ensemble [19,20] with lattice spacing a = 0.1207 (11) fm and pion mass M sea π = 305.3(4) MeV.…”