Los Alamos National Laboratory

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Theoretical Physics Quarterly Progress Reports

Investigating the field of high energy physics through experiments that strengthen our fundamental understanding of matter, energy, space, and time.

Los Alamos HEP Theory Quarterly Report FY2019-Q4

Daniele Alves, Tanmoy Bhattacharya, Michael L. Graesser, Rajan Gupta

The primary areas of activity of the theory group are in physics beyond the Standard Model, cosmology, dark matter, lattice quantum chromodynamics, neutrinos, the fundamentals of quantum field theory and gravity, and particle astrophysics. The questions pursued by this group relate to deep mysteries in our understanding of Nature at the level of the Standard Model and beyond. The main tools we use are quantum field theory and General Relativity. There is also a growing effort in quantum computing, quantum information and quantum algorithms that is funded under the DOE call "Quantum Information Science Enabled Discovery For High Energy Physics" (QuantISED).

Lattice QCD

The Los Alamos Lattice QCD team and their collaborators are carrying out precision studies investigating signatures of new physics at the TeV scale, Novel CP violating operator's contribution to nEDM, elucidating the structure of the nucleon, and neutrino-nucleon interactions. Progress during this quarter on these projects is summarized below.

Nucleon charges and form-factors

The analysis of isovector electric and magnetic form factors from the 2+1+1-flavor clover-on-HISQ calculations was completed and results were submitted for publication. A paper solving the problem of the violation of the partially conserved axial current by the axial form factors was prepared and submitted for publication. The final analysis of a manuscript on axial vector form factors on both 2+1+1-flavor clover-on-HISQ and 2+1-flavor clover-on-clover ensembles was carried out. Analysis of 2+1-flavor clover-on-clover lattice QCD calculations is in final stages and manuscripts describing the results are under preparation.

Relevant References:
Electric and Magnetic Form Factors arXiv:1906.07217
Axial Vector Form Factors from Lattice QCD that Satisfy the PCAC Relation arXiv:1905.06470
FLAG Review arXiv:1902.08191
Physical Review D98 (2018) 094512 arXiv:1806.10604
Physical Review D98 (2018) 091501 arXiv:1808.07597
Physical Review D98 (2018) 034503 arXiv:1806.09006
Physical Review D96 (2017) 114503 arXiv:1705.06834
Physical Review D95:5 (2017) 074508
Physical Review D94:5 (2016) 054508
Physical Review D93:11 (2016) 114506
arXiv:1601.01730
Physical Review D92:9 (2015) 094511
Physical Review D89:9 (2014) 094502
Physical Review D85:5 (2012) 054512

Matrix elements of novel CP violating operators and nEDM

Calculations of the matrix elements of the quark chromo electric dipole moment operator (cEDM) and its mixing with the pseudoscalar operator, and of the Theta and Weinberg terms are on going. Preliminary results using a variance reduction method developed by us show a factor of ten reduction in errors. Investigations of gradient flow method to deal with the divergent renormalization and mixing problem of the cEDM and Weinberg operators are continuing. The status of our results were presented by Boram Yoon at Lattice 2019.

Relevant References:
arXiv:1812.06233
arXiv:1712.08557
arXiv:1701.04132
arXiv:1612.08438
arXiv:1601.02264
Physical Review D92:9 (2015) 114026
Physical Review Letters 112:21 (2015) 212002
arXiv:1502.07325
arXiv:1403.2445
arXiv:1212.4918

Matrix elements of flavor diagonal operators 

The matrix elements of flavor diagonal operators are needed for the analysis of a number of interesting qualities such as the nucleon electric dipole moment, the quark contribution to the nucleon spin, the nucleon sigma term and the strangeness content of the proton, and the interaction of dark matter with nucleons. These matrix elements get contributions from both connected and disconnected diagrams. The latter are computationally challenging to compute with high precision. This quarter, Bhattacharya, Gupta, Park and Yoon continued their analysis of the matrix elements of the scalar operator and their renormalization. These matrix elements are relevant for the sigma terms and dark matter interaction with nucleons.

Relevant References:
Physical Review D98 (2018) 094512 arXiv:1806.10604
Physical Review D98 (2018) 091501 arXiv:1808.07597
arXiv:1611.01193

Transverse Momentum Distribution Functions

New simulations, in collaboration with the Regensburg group, are continuing.

Relevant References:
Physical Review D96 (2017) 094508 arXiv:1706.03406
arXiv:1611.01193
arXiv:1601.05717

QuantISED 

  • Bhattacharya, Gupta and collaborators are developing methods to map continuum field theories onto a discrete space-time lattice with a small finite Hilbert space at each lattice site. They are currently determining whether the O(3) sigma model, represented by various O(3)-symmetric two-qubit Hamiltonian on each lattice site, displays desired properties such as confinement and topology. The long term goal is determine whether the sign problem and formulation of chiral gauge theories that are challenges for classical computers can be addressed by quantum computers. They are also developing algorithms for simulating qubit versions of field theories on quantum computers.
  • Gupta and collaborators are developing quantum algorithms to understand the final states observed in the detector in a neutrino-nucleus interaction and connect it to the neutrino energy. This requires modelling the initial state (dominated by energy and distance scales of the order of the separation between nucleons in the nucleus) and the struck state and then evolve it quantum mechanically and calculate the response functions that encode information about the final states observed in the detectors. They are also exploring different error-mitigation techniques to increase the fidelity of the calculations. Details of the calculations and methodology are given in Ref. [1].
  • Sorborger and collaborators are developing quantum algorithms for studying the foundations of quantum physics. Their algorithms will enable studies of the quantum-classical transition on near-term quantum computers and will extend the array of tools available to physicists for the study of system-environment interactions.
  • Yoon, Bhattacharya, Gupta and collaborators are continuing to work on (1) enhancing lattice QCD calculations with the Machine Learning regression algorithm using the D-Wave quantum annealer, (2) developing a data compression algorithm on D-Wave and apply it to lattice QCD and Large Hadron Collider data, and (3) investigating various applications of the sparse coding implemented on D-Wave as a feature extraction algorithm that improves quantum support vector machine, generative models for lattice QCD Monte Carlo sampling and anomaly detector.

Publications:
Quantum Computing for Neutrino-nucleus Scattering, arXiv:1911.06368 (2019)
A regression algorithm for accelerated lattice QCD that exploits sparse inference on the D-Wave quantum annealer, arXiv:1911.06267 (2019)
Machine-Learning Prediction for Quasi-PDF Matrix Elements, arXiv:1909.10990 (2019)
Physics Review D100 (2019) 054505: Qubit regularization of the O(3) sigma model
Physics Review D100 (2019) 014504: Machine Learning for Lattice QCD
Quantum simulations of one-dimensional quantum systems, R.D. Somma, Quantum Info. Comput. 16, 1125 (2016)

Michael Graesser: Dark Matter and LHC Physics 

Graesser and University of New Mexico graduate student Jacek Osinski are finishing a manuscript on the impact that non-trivial cosmologies in the early history of the Universe may have on scenarios for topological dark matter. He is also investigating the constraints magnetars and other stellar objects may place on axion-like particles or other cosmological relics. He is also exploring hidden sector monopole models for dark matter and their direct detection and astrophysical constraints in collaboration with Ian Shoemaker.

Relevant References:
Physics Letters B749 (2014) 293
arXiv:1311.2028
Physical Review Letters111 (2013) 121802
JHEP 1302(2013) 046
JHEP 1210(2012) 025
Physics Letters B714 (2012) 267
Physics Review D85 (2012) 054512
arXiv:1107.2666
JHEP 1110(2011) 110

Michael Graesser: Neutrinoless double beta decay

Graesser continues his research into the neutrinoless double beta decay process nn-> pp ee. A paper extending previous work to next-to-leading order in the chiral expansion has been published.

Relevant References:
Physical ReviewC100 (2019) no.5, 055504 arXiv:1907.11254
Journal of High Energy Physics12 (2018) 097 arXiv:1806.02780
Physical Review Letters 120:20 (2018) 202001 arXiv:1802.10097
Journal of High Energy Physics12 (2017) 82 arXiv:1708.09390
Journal of High Energy Physics (2017)99
Physics Letters B769 (2017) 460

Daniel S. M. Alves

During the past quarter, Daniele has worked on the following topics:

  • models of sterile neutrinos with BSM matter effects induced by light mediators, to explain the MiniBooNE low energy excess and the distortion in the 8B solar neutrino spectrum. She is currently investigating whether this model might also explain the LSND anomaly;
  • new 40Ar disintegration signatures of light axions and dark photons at CCM, and estimation of CCM sensitivity to uncovered parameter space in this models;
  • axion interactions with monopoles, and possible realization of these interactions in condensed matter systems, such as spin ice;
  • investigation of whether the anomalies in 8Be and 4He transitions can be tested with a new experiment hosted at LANL;
  • preparation of a new paper on future experimental constraints on a pion-phobic QCD axion in the MeV mass window;
  • a new implementation of the renormalization group in EFTs in position space, by generalizing methods of entanglement renormalization and tensor networks from CMP and QIS.

Relevant References:
Journal of High Energy Physics 07 (2018) 92 arXiv:1710.03764