Publications

2020

2021

1. PLA

   Nuclear predictions for H spectroscopy without nuclear errors

   C. P. Burgess, P. Hayman, Markus Rummel, and László Zalavári

   Abs arXiv Bibtex

   Nuclear-structure effects often provide an irreducible theory error that prevents using precision atomic measurements to test fundamental theory. We apply newly developed effective field theory tools to Hydrogen atoms, and use them to show that (to the accuracy of present measurements) all nuclear finite-size effects (e.g. the charge radius, Friar moments, nuclear polarizabilities, recoil corrections, Zemach moments etc.) only enter into atomic energies through exactly two parameters, independent of any nuclear-modeling uncertainties. Since precise measurements are available for more than two atomic levels in Hydrogen, this observation allows the use of precision atomic measurements to eliminate the theory error associated with nuclear matrix elements. We apply this reasoning to the seven atomic measurements whose experimental accuracy is smaller than 10 kHz to provide predictions for nuclear-size effects whose theoretical accuracy is not subject to nuclear-modeling uncertainties and so are much smaller than 1 kHz. Furthermore, the accuracy of these predictions can improve as atomic measurements improve, allowing precision fundamental tests to become possible well below the ‘irreducible’ error floor of nuclear theory.

   @article{burgess_nuclear_2021,
     title = {Nuclear predictions for {H} spectroscopy without nuclear errors},
     abbr = {{P}{L}{A}},
     volume = {390},
     copyright = {All rights reserved},
     issn = {0375-9601},
     url = {http://www.sciencedirect.com/science/article/pii/S0375960120309725},
     doi = {10.1016/j.physleta.2020.127105},
     language = {en},
     urldate = {2020-12-29},
     journaltitle = {Physics Letters A},
     author = {Burgess, C. P. and Hayman, P. and Rummel, Markus and Zalavári, László},
     month = feb,
     keywords = {Atomic spectra, Effective field theory, Model-independent nuclear-size effect predictions, Renormalization},
     pages = {127105},
     date = {2021},
     arxiv = {2008.09719}
   }

2. AOP

   Precision nuclear-spin effects in atoms: EFT methods for reducing theory errors

   L. Zalavari, C. P. Burgess, P. Hayman, and M. Rummel

   Annals of Physics 2021

   Abs arXiv Bibtex

   We use effective field theory to compute the influence of nuclear structure on precision calculations of atomic energy levels. As usual, the EFT’s effective couplings correspond to the various nuclear properties (such as the charge radius, nuclear polarizabilities, Friar and Zemach moments etc.) that dominate its low-energy electromagnetic influence on its surroundings. By extending to spinning nuclei the arguments developed for spinless ones in Burgess, et al. (2018), we use the EFT to show – to any fixed order in Zα (where Z is the atomic number and α the fine-structure constant) and the ratio of nuclear to atomic size – that nuclear properties actually contribute to electronic energies through fewer parameters than the number of these effective nuclear couplings naively suggests. Our result is derived using a position-space method for matching effective parameters to nuclear properties in the EFT, that more efficiently exploits the simplicity of the small-nucleus limit in atomic systems. By showing that precision calculations of atomic spectra depend on fewer nuclear uncertainties than naively expected, this observation allows the construction of many nucleus-independent combinations of atomic energy differences whose measurement can be used to test fundamental physics (such as the predictions of QED) because their theoretical uncertainties are not limited by the accuracy of nuclear calculations. We provide several simple examples of such nucleus-free predictions for Hydrogen-like atoms.

   @article{zalavari_precision_2021,
     title = {Precision nuclear-spin effects in atoms: {EFT} methods for reducing theory errors},
     abbr = {{A}{O}{P}},
     volume = {429},
     copyright = {All rights reserved},
     issn = {0003-4916},
     shorttitle = {Precision nuclear-spin effects in atoms},
     url = {https://www.sciencedirect.com/science/article/pii/S0003491621000695},
     doi = {10.1016/j.aop.2021.168463},
     language = {en},
     urldate = {2021-04-30},
     journal = {Annals of Physics},
     author = {Zalavari, L. and Burgess, C. P. and Hayman, P. and Rummel, M.},
     month = jun,
     year = {2021},
     pages = {168463},
     keywords = {Atomic spectra, Effective field theory, Model-independent nuclear-size effect predictions, Renormalization},
     arxiv = {2008.09718}
   }

2019

1. Frontiers

   Point-Particle Catalysis

   Peter Hayman, and Cliff P. Burgess

   Abs arXiv Bibtex

   We use the point-particle effective field theory (PPEFT) framework to describe particle-conversion mediated by a flavour-changing coupling to a point-particle. We do this for a toy model of two non-relativistic scalars coupled to the same point-particle, on which there is a flavour-violating coupling. It is found that the point-particle couplings all must be renormalized with respect to a radial cut-off near the origin, and it is an invariant of the flow of the flavour-changing coupling that is directly related to particle-changing cross-sections. At the same time, we find an interesting dependence of those cross-sections on the ratio k_out/k_in of the outgoing and incoming momenta, which can lead to a 1/k_in enhancement in certain regimes. We further connect this model to the case of a single-particle non-self-adjoint (absorptive) PPEFT, as well as to a PPEFT of a single particle coupled to a two-state nucleus. These results could be relevant for future calculations of any more complicated reactions, such as nucleus-induced electron-muon conversions, monopole catalysis of baryon number violation, as well as nuclear transfer reactions.

   @article{hayman_point-particle_2019,
     abbr = {Frontiers},
     arxiv = {1905.00103},
     title = {Point-Particle Catalysis},
     volume = {7},
     issn = {2296-424X},
     url = {https://www.frontiersin.org/articles/10.3389/fphy.2019.00167/full?&utm_source=Email_to_authors_&utm_medium=Email&utm_content=T1_11.5e1_author&utm_campaign=Email_publication&field=&journalName=Frontiers_in_Physics&id=469321},
     doi = {10.3389/fphy.2019.00167},
     journaltitle = {Front. Phys.},
     author = {Hayman, Peter and Burgess, Cliff P.},
     urldate = {2019-11-06},
     date = {2019},
     keywords = {Effective Field Theories, Catalysis, Flavour violation, High energy physics - theory, Nuclear theory},
     file = {Full Text PDF:/home/peter/Nextcloud/Zotero/storage/93M9GIC3/Hayman and Burgess - 2019 - Point-Particle Catalysis.pdf:application/pdf},
     selected = true
   }

2018

1. PRA

   Reduced theoretical error for ⁴He⁺ spectroscopy

   C. P. Burgess, P. Hayman, Markus Rummel, and László Zalavári

   Abs arXiv Bibtex

   We apply point-particle effective field theory to electronic and muonic 4He+ ions, and use it to identify linear combinations of spectroscopic measurements for which the theoretical uncertainties are much smaller than for any particular energy levels. The error is reduced because these combinations are independent of all short-range physics effects up to a given order in the expansion in the small parameters R/aB and Zα (where R and aB are the ion’s nuclear and Bohr radii). In particular, the theory error is not limited by the precision with which nuclear matrix elements can be computed, or compromised, by the existence of any novel short-range interactions, should these exist. These combinations of 4He measurements therefore provide particularly precise tests of quantum electrodynamics. The restriction to 4He arises because our analysis assumes a spherically symmetric nucleus, but the argument used is more general and extendable to both nuclei with spin, and to higher orders in R/aB and Zα.

   @article{burgess_reduced_2018,
     abbr = {{P}{R}{A}},
     arxiv = {1708.09768},
     title = {Reduced theoretical error for \textsuperscript{4}{He}\textsuperscript{+} spectroscopy},
     volume = {98},
     url = {https://link.aps.org/doi/10.1103/PhysRevA.98.052510},
     doi = {10.1103/PhysRevA.98.052510},
     pages = {052510},
     number = {5},
     publisher = aps,
     journaltitle = {Phys. Rev. A},
     author = {Burgess, C. P. and Hayman, P. and Rummel, Markus and Zalavári, László},
     urldate = {2019-03-28},
     date = {2018-11-19},
     selected = true
   }

2017

1. JHEP

   Point-particle effective field theory III: relativistic fermions and the Dirac equation

   C. P. Burgess, Peter Hayman, Markus Rummel, and László Zalavári

   Abs arXiv Bibtex

   We formulate point-particle effective field theory (PPEFT) for relativistic spin-half fermions interacting with a massive, charged finite-sized source using a first-quantized effective field theory for the heavy compact object and a second-quantized language for the lighter fermion with which it interacts. This description shows how to determine the near-source boundary condition for the Dirac field in terms of the relevant physical properties of the source, and reduces to the standard choices in the limit of a point source. Using a first-quantized effective description is appropriate when the compact object is sufficiently heavy, and is simpler than (though equivalent to) the effective theory that treats the compact source in a second-quantized way. As an application we use the PPEFT to parameterize the leading energy shift for the bound energy levels due to finite-sized source effects in a model-independent way, allowing these effects to be fit in precision measurements. Besides capturing finite-source-size effects, the PPEFT treatment also efficiently captures how other short-distance source interactions can shift bound-state energy levels, such as due to vacuum polarization (through the Uehling potential) or strong interactions for Coulomb bound states of hadrons, or any hypothetical new short-range forces sourced by nuclei.

   @article{burgess_point-particle_2017-2,
     abbr = {{J}{H}{E}{P}},
     arxiv = {1706.01063},
     title = {Point-particle effective field theory {III}: relativistic fermions and the Dirac equation},
     volume = {2017},
     issn = {1029-8479},
     url = {https://doi.org/10.1007/JHEP09(2017)007},
     publisher = springer,
     doi = {10.1007/JHEP09(2017)007},
     shorttitle = {Point-particle effective field theory {III}},
     pages = {7},
     number = {9},
     journaltitle = {J. High Energ. Phys.},
     author = {Burgess, C. P. and Hayman, Peter and Rummel, Markus and Zalavári, László},
     urldate = {2019-03-28},
     date = {2017-09-04},
     langid = {english},
     keywords = {Effective Field Theories, Nonperturbative Effects, Renormalization Group},
     file = {Springer Full Text PDF:/home/peter/Nextcloud/Zotero/storage/BW5NILTQ/Burgess et al. - 2017 - Point-particle effective field theory III relativ.pdf:application/pdf}
   }

2. JHEP

   Point-particle effective field theory II: relativistic effects and Coulomb/inverse-square competition

   C. P. Burgess, Peter Hayman, Markus Rummel, Matt Williams, and László Zalavári

   Abs arXiv Bibtex

   We apply point-particle effective field theory (PPEFT) to compute the leading shifts due to finite-sized source effects in the Coulomb bound energy levels of a relativistic spinless charged particle. This is the analogue for spinless electrons of calculating the contribution of the charge-radius of the source to these levels, and our calculation disagrees with standard calculations in several ways. Most notably we find there are two effective interactions with the same dimension that contribute to leading order in the nuclear size, one of which captures the standard charge-radius contribution. The other effective operator is a contact interaction whose leading contribution to δE arises linearly (rather than quadratically) in the small length scale, ϵ, characterizing the finite-size effects, and is suppressed by (Zα)5. We argue that standard calculations miss the contributions of this second operator because they err in their choice of boundary conditions at the source for the wave-function of the orbiting particle. PPEFT predicts how this boundary condition depends on the source’s charge radius, as well as on the orbiting particle’s mass. Its contribution turns out to be crucial if the charge radius satisfies ϵ ≲ (Zα)2 a B , where a B is the Bohr radius, because then relativistic effects become important for the boundary condition. We show how the problem is equivalent to solving the Schrödinger equation with competing Coulomb, inverse-square and delta-function potentials, which we solve explicitly. A similar enhancement is not predicted for the hyperfine structure, due to its spin-dependence. We show how the charge-radius effectively runs due to classical renormalization effects, and why the resulting RG flow is central to predicting the size of the energy shifts (and is responsible for its being linear in the source size). We discuss how this flow is relevant to systems having much larger-than-geometric cross sections, such as those with large scattering lengths and perhaps also catalysis of reactions through scattering with monopoles. Experimental observation of these effects would require more precise measurement of energy levels for mesonic atoms than are now possible.

   @article{burgess_point-particle_2017-1,
     abbr = {{J}{H}{E}{P}},
     arxiv = {1612.07334},
     title = {Point-particle effective field theory {II}: relativistic effects and Coulomb/inverse-square competition},
     volume = {2017},
     issn = {1029-8479},
     url = {https://doi.org/10.1007/JHEP07(2017)072},
     doi = {10.1007/JHEP07(2017)072},
     shorttitle = {Point-particle effective field theory {II}},
     pages = {72},
     number = {7},
     journaltitle = {J. High Energ. Phys.},
     author = {Burgess, C. P. and Hayman, Peter and Rummel, Markus and Williams, Matt and Zalavári, László},
     urldate = {2019-03-28},
     date = {2017-07-14},
     langid = {english},
     keywords = {Effective Field Theories, Nonperturbative Effects, Renormalization Group},
     file = {Springer Full Text PDF:/home/peter/Nextcloud/Zotero/storage/KIY8YZ5Z/Burgess et al. - 2017 - Point-particle effective field theory II relativi.pdf:application/pdf}
   }

3. Nucl.Instr.Meth.A

   A time projection chamber with GEM-based readout

   David Attié, et al.

   Abs arXiv Bibtex

   For the International Large Detector concept at the planned International Linear Collider, the use of time projection chambers (TPC) with micro-pattern gas detector readout as the main tracking detector is investigated. In this paper, results from a prototype TPC, placed in a 1T solenoidal field and read out with three independent Gas Electron Multiplier (GEM) based readout modules, are reported. The TPC was exposed to a 6GeV electron beam at the DESY II synchrotron. The efficiency for reconstructing hits, the measurement of the drift velocity, the space point resolution and the control of field inhomogeneities are presented.

   @article{attie_time_2017,
     title = {A time projection chamber with {GEM}-based readout},
     arxiv = {1604.00935},
     abbr = {{Nucl.}{Instr.}{Meth.}{A}},
     volume = {856},
     issn = {0168-9002},
     url = {http://www.sciencedirect.com/science/article/pii/S0168900216311226},
     doi = {10.1016/j.nima.2016.11.002},
     pages = {109--118},
     journaltitle = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
     author = {Attié, David and Behnke, Ties and Bellerive, Alain and Bezshyyko, Oleg and Bhattacharya, Deb Sankar and Bhattacharya, Purba and Bhattacharya, Sudeb and Caiazza, Stefano and Colas, Paul and Lentdecker, Gilles De and Dehmelt, Klaus and Desch, Klaus and Diener, Ralf and Dixit, Madhu and Fleck, Ivor and Fujii, Keisuke and Fusayasu, Takahiro and Ganjour, Serguei and Gao, Yuanning and Gros, Philippe and Hayman, Peter and Hedberg, Vincent and Ikematsu, Katsumasa and Jönsson, Leif and Kaminski, Jochen and Kato, Yukihiro and Kawada, Shin-ichi and Killenberg, Martin and Kleinwort, Claus and Kobayashi, Makoto and Krylov, Vladyslav and Li, Bo and Li, Yulan and Lundberg, Björn and Lupberger, Michael and Majumdar, Nayana and Matsuda, Takeshi and Mehdiyev, Rashid and Mjörnmark, Ulf and Müller, Felix and Münnich, Astrid and Mukhopadhyay, Supratik and Ogawa, Tomohisa and Oskarsson, Anders and Österman, Lennart and Peterson, Daniel and Riallot, Marc and Rosemann, Christoph and Roth, Stefan and Schade, Peter and Schäfer, Oliver and Settles, Ronald Dean and Shirazi, Amir Noori and Smirnova, Oxana and Sugiyama, Akira and Takahashi, Tohru and Tian, Junping and Timmermans, Jan and Titov, Maksym and Tsionou, Dimitra and Vauth, Annika and Wang, Wenxin and Watanabe, Takashi and Werthenbach, Ulrich and Yang, Yifan and Yang, Zhenwei and Yonamine, Ryo and Zenker, Klaus and Zhang, Fan},
     urldate = {2019-03-28},
     date = {2017-06-01},
     keywords = {Gas electron multipliers ({GEM}), International Large Detector ({ILD}), International Linear Collider ({ILC}), Micropattern gaseous detectors ({MPGD}), Time projection chambers ({TPC})},
     file = {ScienceDirect Full Text PDF:/home/peter/Nextcloud/Zotero/storage/TPR3PEPG/Attié et al. - 2017 - A time projection chamber with GEM-based readout.pdf:application/pdf;ScienceDirect Snapshot:/home/peter/Nextcloud/Zotero/storage/6M4DSLWS/S0168900216311226.html:text/html}
   }

4. JHEP

   Point-particle effective field theory I: classical renormalization and the inverse-square potential

   C.P. Burgess, Peter Hayman, M. Williams, and László Zalavári

   Abs arXiv Bibtex

   Singular potentials (the inverse-square potential, for example) arise in many situations and their quantum treatment leads to well-known ambiguities in choosing boundary conditions for the wave-function at the position of the potential’s singularity. These ambiguities are usually resolved by developing a self-adjoint extension of the original prob-lem; a non-unique procedure that leaves undetermined which extension should apply in specific physical systems. We take the guesswork out of this picture by using techniques of effective field theory to derive the required boundary conditions at the origin in terms of the effective point-particle action describing the physics of the source. In this picture ambiguities in boundary conditions boil down to the allowed choices for the source action, but casting them in terms of an action provides a physical criterion for their determination. The resulting extension is self-adjoint if the source action is real (and involves no new degrees of freedom), and not otherwise (as can also happen for reasonable systems). We show how this effective-field picture provides a simple framework for understanding well-known renormalization effects that arise in these systems, including how renormalization-group techniques can resum non-perturbative interactions that often arise, particularly for non-relativistic applications. In particular we argue why the low-energy effective theory tends to produce a universal RG flow of this type and describe how this can lead to the phenomenon of reaction catalysis, in which physical quantities (like scattering cross sections) can sometimes be surprisingly large compared to the underlying scales of the source in question. We comment in passing on the possible relevance of these observations to the phenomenon of the catalysis of baryon-number violation by scattering from magnetic monopoles.

   @article{burgess_point-particle_2017,
     abbr = {{J}{H}{E}{P}},
     arxiv = {1612.07313},
     title = {Point-particle effective field theory I: classical renormalization and the inverse-square potential},
     volume = {2017},
     issn = {1029-8479},
     url = {https://doi.org/10.1007/JHEP04(2017)106},
     doi = {10.1007/JHEP04(2017)106},
     shorttitle = {Point-particle effective field theory I},
     pages = {106},
     number = {4},
     journaltitle = {J. High Energ. Phys.},
     author = {Burgess, C.P. and Hayman, Peter and Williams, M. and Zalavári, László},
     urldate = {2019-03-28},
     date = {2017-04-19},
     langid = {english},
     keywords = {Nonperturbative Effects, Renormalization Group, Effective field theories},
     file = {Springer Full Text PDF:/home/peter/Nextcloud/Zotero/storage/IAGILVN8/Burgess et al. - 2017 - Point-particle effective field theory I classical.pdf:application/pdf}
   }

2016

1. JCAP

   Magnon inflation: slow roll with steep potentials

   Peter Adshead, Diego Blas, C. P. Burgess, Peter Hayman, and Subodh P. Patil

   Abs arXiv Bibtex

   We find multi-scalar effective field theories (EFTs) that can achieve a slow inflationary roll despite having a scalar potential that does not satisfy 𝒢ab ∂a V ∂b V ≪ V2/Mp2 (where 𝒢ab is the target-space metric). They evade the usual slow-roll conditions on V because their kinetic energies are dominated by single-derivative terms rather than the usual two-derivative terms. Single derivatives dominate during slow roll and so do not require a breakdown of the usual derivative expansion that underpins calculational control in much of cosmology. The presence of such terms requires some sort of UV Lorentz-symmetry breaking during inflation (besides the usual cosmological breaking). Chromo-natural inflation provides one particular example of a UV theory that can generate the multi-field single-derivative terms we consider, and we argue that the EFT we find indeed captures the slow-roll conditions for its background evolution. We also show that our EFT can be understood as a multi-field generalization of the single-field Cuscuton models. The multi-field case introduces a new feature, however: the scalar kinetic terms define a target-space 2-form, ℱab, whose antisymmetry gives new ways for slow roll to be achieved.

   @article{adshead_magnon_2016,
     abbr = {{J}{C}{A}{P}},
     arxiv = {1604.06048},
     title = {Magnon inflation: slow roll with steep potentials},
     volume = {2016},
     issn = {1475-7516},
     url = {https://doi.org/10.1088%2F1475-7516%2F2016%2F11%2F009},
     doi = {10.1088/1475-7516/2016/11/009},
     shorttitle = {Magnon inflation},
     pages = {009--009},
     number = {11},
     journaltitle = {J. Cosmol. Astropart. Phys.},
     author = {Adshead, Peter and Blas, Diego and Burgess, C. P. and Hayman, Peter and Patil, Subodh P.},
     urldate = {2019-03-28},
     date = {2016-11},
     langid = {english},
     file = {IOP Full Text PDF:/home/peter/Nextcloud/Zotero/storage/TPYRMJFZ/Adshead et al. - 2016 - Magnon inflation slow roll with steep potentials.pdf:application/pdf},
     selected = true
   }

2. JCAP

   Goldilocks models of higher-dimensional inflation (including modulus stabilization)

   C. P. Burgess, Jared J. H. Enns, Peter Hayman, and Subodh P. Patil

   Abs arXiv Bibtex

   We explore the mechanics of inflation within simplified extra-dimensional models involving an inflaton interacting with the Einstein-Maxwell system in two extra dimensions. The models are Goldilocks-like inasmuch as they are just complicated enough to include a mechanism to stabilize the extra-dimensional size (or modulus), yet simple enough to solve explicitly the full extra-dimensional field equations using only simple tools. The solutions are not restricted to the effective 4D regime with H ≪ mKK (the latter referring to the characteristic mass splitting of the Kaluza-Klein excitations) because the full extra-dimensional Einstein equations are solved. This allows an exploration of inflationary physics in a controlled calculational regime away from the usual four-dimensional lamp-post. The inclusion of modulus stabilization is important because experience with string models teaches that this is usually what makes models fail: stabilization energies easily dominate the shallow potentials required by slow roll and so open up directions to evolve that are steeper than those of the putative inflationary direction. We explore (numerically and analytically) three representative kinds of inflationary scenarios within this simple setup. In one the radion is trapped in an inflaton-dependent local minimum whose non-zero energy drives inflation. Inflation ends as this energy relaxes to zero when the inflaton finds its own minimum. The other two involve power-law scaling solutions during inflation. One of these is a dynamical attractor whose features are relatively insensitive to initial conditions but whose slow-roll parameters cannot be arbitrarily small; the other is not an attractor but can roll much more slowly, until eventually transitioning to the attractor. The scaling solutions can satisfy H \textgreater mKK, but when they do standard 4D fluctuation calculations need not apply. When in a 4D regime the solutions predict η ≃ 0 and so r ≃ 0.11 when ns ≃ 0.96 and so are ruled out if tensor modes remain unseen. Assessment of general parameters is difficult until a full 6D fluctuation calculation is done.

   @article{burgess_goldilocks_2016,
     abbr = {{J}{C}{A}{P}},
     arxiv = {1605.03297},
     title = {Goldilocks models of higher-dimensional inflation (including modulus stabilization)},
     volume = {2016},
     issn = {1475-7516},
     url = {https://doi.org/10.1088%2F1475-7516%2F2016%2F08%2F045},
     doi = {10.1088/1475-7516/2016/08/045},
     pages = {045--045},
     number = {8},
     journaltitle = {J. Cosmol. Astropart. Phys.},
     author = {Burgess, C. P. and Enns, Jared J. H. and Hayman, Peter and Patil, Subodh P.},
     urldate = {2019-03-28},
     date = {2016-08},
     langid = {english},
     file = {IOP Full Text PDF:/home/peter/Nextcloud/Zotero/storage/8IIY6VIY/Burgess et al. - 2016 - Goldilocks models of higher-dimensional inflation .pdf:application/pdf}
   }