Consistency of the standard model effective field theory
- PDF / 1,083,040 Bytes
- 52 Pages / 595.276 x 841.89 pts (A4) Page_size
- 105 Downloads / 201 Views
Springer
Received: September 7, Revised: November 19, Accepted: November 20, Published: December 4,
2019 2019 2019 2019
Grant N. Remmen and Nicholas L. Rodd Center for Theoretical Physics and Department of Physics, University of California, Berkeley, CA 94720, U.S.A. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
E-mail: [email protected], [email protected] Abstract: We derive bounds on couplings in the standard model effective field theory (SMEFT) as a consequence of causality and the analytic structure of scattering amplitudes. In the SMEFT, there are 64 independent operators at mass dimension eight that are quartic in bosons (either Higgs or gauge fields) and that contain four derivatives and/or field strengths, including both CP-conserving and CP-violating operators. Using analytic dispersion relation arguments for two-to-two bosonic scattering amplitudes, we derive 27 independent bounds on the sign or magnitude of the couplings. We show that these bounds also follow as a consequence of causality of signal propagation in nonvacuum SM backgrounds. These bounds come in two qualitative forms: i) positivity of (various linear combinations of) couplings of CP-even operators and ii) upper bounds on the magnitude of CP-odd operators in terms of (products of) CP-even couplings. We exhibit various classes of example completions, which all satisfy our EFT bounds. These bounds have consequences for current and future particle physics experiments, as part of the observable parameter space is inconsistent with causality and analyticity. To demonstrate the impact of our bounds, we consider applications both to SMEFT constraints derived at colliders and to limits on the neutron electric dipole moment, highlighting the connection between such searches suggested by infrared consistency. Keywords: Beyond Standard Model, Effective Field Theories, CP violation ArXiv ePrint: 1908.09845
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP12(2019)032
JHEP12(2019)032
Consistency of the standard model effective field theory
Contents 1 Introduction
1
2 Infrared consistency
4 8 8 13
4 Bounds 4.1 Single field strength quartics 4.1.1 SU(3) 4.1.2 SU(2) 4.1.3 U(1) 4.2 Field strength cross-quartics 4.3 Higgs quartics 4.4 Higgs/field strength cross-quartics
15 15 18 18 18 19 20 22
5 UV 5.1 5.2 5.3 5.4
23 23 26 27 29
completions One-loop completions of gauge field operators Born-Infeld CP-violating terms and completing the square Tree-level completions of (DH)4 operators
6 Phenomenological consequences 6.1 Anomalous quartic gauge-boson couplings 6.2 Neutron EDM
31 32 38
7 Conclusions
40
A Group theory definitions
41
1
Introduction
We are currently entering a unique era in particle physics. With the discovery of the Higgs boson [1, 2], the Large Hadron Collider (LHC) has completed the detection of all of the fundamental constituents of the standard model (SM). The absence as of yet of detections of supersymmetric (SUSY) partner states [3] — and the possible daw
Data Loading...
