Neutron Electric Dipole Moment: from theory to experiment

1 Aug 2022, 08:40 → 5 Aug 2022, 19:00 Europe/Rome

Aula Leonardi (ECT*)

Andrea Shindler (Michigan State University, East Lansing/US), Andreas Athenodorou (The Cyprus Institute, Larnaca/GR & University of Pisa, Pisa/I), Maria Paola Lombardo (INFN - LNF)

Neutron Electric Dipole Moment (nEDM) could point towards Beyond The Standard Model Physics. This makes it an interesting and timely quantity to investigate. Several experiments measuring the nEDM are now in the process of upgrading their apparati in order to reach higher accuracy than before. At the same time recent advances in Lattice Gauge Theories, as well as the increase in computational power can make the extraction of the nEDM, induced by CP-breaking operators in the QCD lagrangian, possible for physical pion masses. Hence we invite scientists working on nEDM with research areas covering experiment, phenomenology and lattice gauge theories to present their work in order to build a common ground. Talks will be followed by moderated discussions giving the participants the opportunity to understand the recent challenges, set up new collaborations and synergies as well as establish connections between theory and experiment.

           

ECT_Poster.pdf

Monday 1 August

Registration

1 Andreas Athenodorou - Welcome

Neutron Electric Dipole Moment.pptx

2 The nEDM @ Spallation Neutron Source experiment: our novel approach and other physics reach

Speaker: Prof. Kent Leung (Montclair State University)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Kent_Leung.pdf

3 Theta Dependence of QCD and QCD-like Theories

Speaker: Prof. Massimo D' Elia (University of Pisa)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Massimo_D'Elia.pdf

11:30 Coffee Time

4 Neutron electric dipole moment using lattice QCD

We present results on the neutron electric dipole moment |𝑑⃗𝑁| using an ensemble of 𝑁𝑓=2+1+1 twisted mass clover-improved fermions with lattice spacing of 𝑎≃0.08 fm and physical pion mass (𝑚𝜋≃139 MeV). We compute the 𝐶𝑃-odd electromagnetic form factor 𝐹3(𝑄2→0) by expanding the action to leading order in 𝜃. This gives rise to correlation functions that involve the topological charge, for which we employ a fermionic definition by means of spectral projectors. We find a value of
|𝑑⃗𝑁|=0.0009(24) 𝜃 𝑒⋅fm.

Speaker: Prof. Constantia Alexandrou (University of Cyprus)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Constantia_Alexandrou.pdf

13:00 Lunch Buffet

5 The LANL nEDM Experiment

Speaker: Prof. Takeyasu Ito (Los Alamos National Laboratory)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Takeyasu_Ito.pdf

16:00 Coffee Time

Discussion time: Discussion

Tuesday 2 August

6 Cosmological implications of the Neutron Electric Dipole Moment

Speaker: Prof. Laura Covi (Georg-August-Universität Göttingen)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Laura_Covi.pdf

7 Topology in SU(N) gauge theories

Speaker: Dr Michael Teper (University of Oxford)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Michael_Teper.pdf

11:30 Coffee Time

8 Cluster decomposition, the index theorem, and the strong CP problem

Speaker: Dr Carlos Tamarit (Technische Universität München)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Carlos_Tamarit.pdf

13:00 Lunch

9 EDMs and Baryogenesis

Speaker: Prof. Michael Ramsey-Musolf (University of Massachusetts)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Michael_J_Ramsey_Musolf.pdf

16:00 Coffee time

Discussion time

Wednesday 3 August

10 The most stringent limit on the nEDM and future improvements at PSI

As widely known, the discovery of an electric dipole moment (EDM) of the neutron would manifest the invariance time reversal and violate the combined symmetry of charge and parity (CP). At current experimental sensitivities an univocal signature of new physics, either induced by the QCD Theta-term or some beyond Standard Model mechanism.
I will present the most stringent limit on the neutron EDM,
|d_n |<1.8×10^(-26) ecm [4], from an experiment performed at the Paul Scherrer Institute by an international collaboration deploying Ramsey’s method of separated oscillating magnetic fields on stored ultra cold neutrons. I will motivate and discuss the most salient feature of the experiment, a 199Hg co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes.
In a second part, I will present the design of the new instrument, n2EDM, currently mounted at PSI, which will further increase the sensitivity to about 1×10^(-27) ecm [5].

References

[1] A.D. Sakharov. JETP Lett. 5, 24(1967)
[2] C.L. Bennett, D. Larson, J. L. Weiland, et al., ApJS 208, 20 (2013)
[3] D.E. Morrissey and M.J. Ramsey-Musolf, New J. Phys. 14, 125003 (2012)
[4] C. Abel et al., PRL124, 081803 (2020)
[5] N.J. Ayres et al., EPJC81, 512 (2021)

Speaker: Dr Philipp Schmidt-Wellenburg (Paul Scherrer Institute)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Schmidt-Wellenburg_Philipp.pptx

11 BeamEDM – A beam experiment to search for the neutron electric dipole moment

Speaker: Prof. Florian Piegsa (University of Bern)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Florian_Piegsa.pdf

11:30 Coffee time

12 Fermion correlations and absence of CP violation in the strong interactions

Speaker: Prof. Bjorn Garbrecht (Technical University Munich)

Trento22.pdf

13:00 Lunch time

13 Calculation of neutron EDMs on the lattice

Speaker: Dr Boram Yoon (Los Alamos National Laboratory)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Boram_Yoon.pdf

16:00 Coffee time

Discussion time: Discussion

Thursday 4 August

14 Aspects of strong CP violation

In this talk, I will explore consequences of the QCD θ-term in our Universe as well as in the Multiverse. First, I discuss the bounds set by element generation in the Big Bang on the value of θ. Then, I present precision results on various couplings of the axion to matter and also discuss a recent proposal of enhanced axiproduction via the ∆(1232) resonance.

Speaker: Prof. Ulf Meißner (University of Bonn)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Ulf_Meissner.pdf

15 Estimating CP-violating nucleon matrix elements from CP-conserving ones

Speaker: Andre Walker-Loud (Lawrence Berkeley National Laboratory)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Andreas_Walker_Loud.pdf

11:30 Coffee time

16 Neutron Electric Dipole Moment from the Theta Term with Overlap Fermions

We report our calculation of the neutron electric dipole moment (EDM) induced by the theta term. We use overlap fermions on three 2+1-flavor RBC/UKQCD domain wall lattices with pion mass ranging from ~300 to ~500 MeV. The use of lattice chiral fermions guarantees a correct chiral limit even at finite lattice spacings and enables us to reliably extrapolate our result from heavy pion masses to the physical point. Furthermore, by utilizing the partially-quenched chiral extrapolation formula, several valence pion points are added to better constrain the chiral extrapolation. With the help of the cluster decomposition error reduction (CDER) technique and a large amount of statistics accumulated, the statistical uncertainty is effectively controlled. We also carefully check the systematic uncertainties from the two-state fits, the momentum extrapolation, the chiral extrapolation and the CDER technique.

Speaker: Dr Keh-Fei Liu (University of Kentucky)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Keh_Fei_Liu.pdf

13:00 Lunch

17 Neutron electric dipole moment from QCD?

In this talk I will present a dynamical solution of the strong CP problem and discuss its consequences for the existence of a non-vanishing electric dipole moment of the neutron.

Speaker: Gerrit Schierholz (DESY)

ectEDM.pdf

15:30 Coffee time

18 Disentangling physics beyond the Standard Model with EDMs

Speaker: Dr Emanuele Mereghetti (Los Alamos National Laboratory)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Mereghetti_Emanuele.pdf

Discussion time: Discussion

Friday 5 August

19 QCD Theta term contribution to nEDM with Stabilized Wilson Fermion on the lattice

Speaker: Dr Jangho Kim (Forschungszentrum Juelich)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Jangho_Kim.pdf

20 Updates on the PanEDM experiment and future outlook

Speaker: Skyler Degenkolb (Universität Heidelberg)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Skyler_Degenkolb.pdf

11:00 Coffee time

21 The Peccei-Quinn axion and QCD topology

The Peccei-Quinn axion provides a simple solution to the strong-CP problem and is also a possible source of Dark Matter, being thus one of the most well-motivated extension of the Standard Model.

The simple relation between the axion mass and the QCD topological susceptibility allows, once the behavior of the latter quantity as a function of the temperature is known, to put useful bounds on the axion scale through the misalignment mechanism, which in principle could also be probed by forthcoming experiments such as IAXO.

The numerical non-perturbative computation of the temperature-behavior of the QCD topological susceptibility from lattice simulations is however an highly non-trivial task, being it plagued by serious computational problems, and many different strategies to overcome them have been proposed in the recent literature to this end.

In this talk, after reviewing the main physical aspects of axion physics and of QCD topology, I will give an overview about the current status of lattice determinations of the QCD topological susceptibility at high temperatures and I will discuss possible future research directions.

Speaker: Dr Claudio Bonanno (INFN Sezione di Firenze)

Neutron_Electric_Dipole_Moment_from_theory_to_experiment_Claudion_Bonanno.pdf

Andrea Shindler: Concluding Remarks

shindler_summary.pdf

13:00 Lunch