| 1. |
- Acharya, B., et al.
(författare)
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Effective-field-theory predictions of the muon-deuteron capture rate
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- We quantify the theoretical uncertainties of chiral effective-field-theory predictions of the muon-deuteron capture rate. Theoretical error estimates of this low-energy process are important for a reliable interpretation of forthcoming experimental results by the MuSun Collaboration. Specifically, we estimate the three dominant sources of uncertainties that impact theoretical calculations of this rate: those resulting from uncertainties in the pool of fit data used to constrain the coupling constants in the nuclear interaction, those due to the truncation of the effective field theory, and those due to uncertainties in the axial radius of the nucleon. For the capture rate into the S01 channel, we find an uncertainty of approximately 4.6s-1 due to the truncation in the effective field theory and an uncertainty of 3.9s-1 due to the uncertainty in the axial radius of the nucleon, both of which are similar in size to the targeted experimental precision of a few percent.
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| 2. |
- Bedaque, P., et al.
(författare)
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Quark mass variation constraints from Big Bang nucleosynthesis
- 2011
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 83:4
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Tidskriftsartikel (refereegranskat)abstract
- We study the impact on the primordial abundances of light elements created by a variation of the quark masses at the time of Big Bang nucleosynthesis (BBN). In order to navigate through the particle and nuclear physics required to connect quark masses to binding energies and reaction rates in a model-independent way, we use lattice QCD data and a hierarchy of effective field theories. We find that the measured 4He abundances put a bound of -1%≲δmq/mq≲0.7% on a possible variation of quark masses. The effect of quark mass variations on the deuterium abundances can be largely compensated by changes of the baryon-to-photon ratio η. Including bounds on the variation of η coming from WMAP results and adding some additional assumptions further narrows the range of allowed values of δmq/mq.
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| 3. |
- Bogner, S. K., et al.
(författare)
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Density matrix expansion for low-momentum interactions
- 2009
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Ingår i: European Physical Journal A. - 1434-601X .- 1434-6001. ; 39:2, s. 219-241
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Tidskriftsartikel (refereegranskat)abstract
- A first step toward a universal nuclear energy density functional based on low-momentum interactions is taken using the density matrix expansion (DME) of Negele and Vautherin. The DME is adapted for non-local momentum space potentials and generalized to include local three-body interactions. Different prescriptions for the three-body DME are compared. Exploratory results are given at the Hartree-Fock level, along with a roadmap for systematic improvements within an effective action framework for the Kohn-Sham density functional theory.
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| 4. |
- Braaten, E., et al.
(författare)
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Efimov physics in Li-6 atoms
- 2010
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 81:1
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Tidskriftsartikel (refereegranskat)abstract
- A new narrow three-atom loss resonance associated with an Efimov trimer crossing the three-atom threshold has recently been discovered in a many-body system of ultracold Li-6 atoms in the three lowest hyperfine spin states at a magnetic field near 895 G. O'Hara and coworkers have used measurements of the three-body recombination rate in this region to determine the complex three-body parameter associated with Efimov physics. Using this parameter as the input, we calculate the universal predictions for the spectrum of Efimov states and for the three-body recombination rate in the universal region above 600 G where all three scattering lengths are large. We predict an atom-dimer loss resonance at 672 +/- 2G associated with an Efimov trimer disappearing through an atom-dimer threshold. We also predict an interference minimum in the three-body recombination rate at 759 +/- 1G where the three-spin mixture may be sufficiently stable to allow experimental study of the many-body system.
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| 5. |
- Braaten, E., et al.
(författare)
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Exact relations for a strongly interacting fermi gas from the operator product expansion
- 2008
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 100:20
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Tidskriftsartikel (refereegranskat)abstract
- The momentum distribution in a Fermi gas with two spin states and a large scattering length has a tail that falls off like 1/k(4) at large momentum k, as pointed out by Tan. He used novel methods to derive exact relations between the coefficient of the tail in the momentum distribution and various other properties of the system. We present simple derivations of these relations using the operator product expansion for quantum fields. We identify the coefficient as the integral over space of the expectation value of a local operator that measures the density of pairs.
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| 6. |
- Braaten, E., et al.
(författare)
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Renormalization in the three-body problem with resonant p-wave interactions
- 2012
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Resonant p-wave interactions can be described by a minimal zero-range model defined by a truncated effective range expansion so that the only two-body interaction parameters are the inverse scattering volume 1/a(p) and the p-wave effective range r(p). This minimal model can be formulated as a local quantum field theory with a p-wave interaction between atom fields and a molecular field. In the two-atom sector, the model is renormalizable, but it has unphysical behavior at high energies because there are negative-probability states with momentum scale r(p). In the sector with three atoms, two of which are identical, renormalization in some parity and angular momentum channels involves an ultraviolet limit cycle, indicating asymptotic discrete scale invariance. The Efimov effect occurs in the unitary limit a(p)(-1/3),r(p) -> 0, but this limit is unphysical because there are low-energy states with negative probability. The minimal model can be of physical relevance only at energies small compared to the energy scale set by r(p) where the effects of negative-probability states are suppressed.
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| 7. |
- Braaten, E., et al.
(författare)
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Short-Time Operator Product Expansion for rf Spectroscopy of a Strongly Interacting Fermi Gas
- 2010
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 104:22
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Tidskriftsartikel (refereegranskat)abstract
- Universal relations that hold for any state provide powerful constraints on systems consisting of fermions with two spin states interacting with a large scattering length. In radio-frequency (rf) spectroscopy, the mean shift in the rf frequency and the large-frequency tail of the rf transition rate are proportional to the contact, which measures the density of pairs with small separations. We show that these universal relations can be derived and extended by using the short-time operator product expansion of quantum field theory. This is a general method for identifying aspects of many-body physics that are controlled by few-body physics.
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| 8. |
- Braaten, Eric, et al.
(författare)
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Universal Relations for Identical Bosons from Three-Body Physics
- 2011
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 106:15, s. 153005-
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Tidskriftsartikel (refereegranskat)abstract
- Systems consisting of identical bosons with a large scattering length satisfy universal relations determined by 2-body physics that are similar to those for fermions with two spin states. They require the momentum distribution to have a large-momentum 1/k4 tail and the radio-frequency transition rate to have a high-frequency 1/ω3/2 tail, both of which are proportional to the 2-body contact. Identical bosons also satisfy additional universal relations that are determined by 3-body physics and involve the 3-body contact, which measures the probability of 3 particles being very close together. The coefficients of the 3-body contact in the 1/k5 tail of the momentum distribution and in the 1/ω2 tail of the radio-frequency transition rate are log-periodic functions of k and ω that depend on the Efimov parameter.
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| 9. |
- Deltuva, A., et al.
(författare)
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Universality in Four-Body Scattering
- 2011
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 51:2-4, s. 235-247
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Tidskriftsartikel (refereegranskat)abstract
- The four-body system is studied in the limit of large two-body scattering length by solving momentum-space integral equations for the transition operators or, alternatively, configuration-space equations for wave function. A number of universal results for atom-trimer and dimer-dimer scattering observables are found. We furthermore address the question whether the universal four-body systems contain additional states besides the known two S-wave states.
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| 10. |
- Drut, J. E., et al.
(författare)
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Exact-exchange density functional theory for neutron drops
- 2011
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:1
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Tidskriftsartikel (refereegranskat)abstract
- We compute the ground-state properties of finite systems of neutrons in an external harmonic trap, interacting via the Minnesota potential, using the "exact-exchange" form of orbital-dependent density functional theory. We compare our results with Hartree-Fock calculations and find very close agreement. Within the context of the interaction studied, we conclude that this simple orbital-dependent functional brings conventional nuclear density functional theory to the level of Hartree-Fock in an ab initio fashion. Our work is a first step toward higher order ab initio nuclear functionals based on realistic nucleon-nucleon interactions.
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| 11. |
- Drut, J. E., et al.
(författare)
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Toward ab initio density functional theory for nuclei
- 2010
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Ingår i: Progress in Particle and Nuclear Physics. - 0146-6410. ; 64:1, s. 120-168
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Tidskriftsartikel (refereegranskat)abstract
- We survey approaches to non-relativistic density functional theory (DFT) for nuclei using progress toward ob initio DFT for Coulomb systems as a guide. Ab initio DFT starts with a microscopic Hamiltonian and is naturally formulated using orbital-based functionals, which generalize the conventional 'local density plus gradients' form. The orbitals satisfy single-particle equations with multiplicative (local) potentials. The DFT functionals can be developed starting from internucleon forces using wavefunction-based methods or by Legendre transform via effective actions. We describe known and unresolved issues for applying these formulations to the nuclear many-body problem and discuss how ab initio approaches can help improve empirical energy density functionals. (C) 2009 Elsevier B.V. All rights reserved.
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| 12. |
- Hagen, G., et al.
(författare)
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Efimov Physics Around the Neutron-Rich Ca-60 Isotope
- 2013
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 111:13
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Tidskriftsartikel (refereegranskat)abstract
- We calculate the neutron-Ca-60 S-wave scattering phase shifts using state of the art coupled-cluster theory combined with modern ab initio interactions derived from chiral effective theory. Effects of three-nucleon forces are included schematically as density dependent nucleon-nucleon interactions. This information is combined with halo effective field theory in order to investigate the Ca-60-neutron-neutron system. We predict correlations between different three-body observables and the two-neutron separation energy of Ca-62. This provides evidence of Efimov physics along the calcium isotope chain. Experimental key observables that facilitate a test of our findings are discussed.
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| 13. |
- Hagen, P., et al.
(författare)
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Charge form factors of two-neutron halo nuclei in halo EFT
- 2013
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 49:9, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- We set up a formalism to calculate the charge form factors of two-neutron halo nuclei with S-wave neutron-core interactions in the framework of the halo effective field theory. The method is applied to some known and suspected halo nuclei. In particular, we calculate the form factors and charge radii relative to the core to leading order in the halo EFT and compare to experiments where they are available. Moreover, we investigate the general dependence of the charge radius on the core mass and the one-and two-neutron separation energies.
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| 14. |
- Hammer, H. W., et al.
(författare)
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Efimov physics in atom-dimer scattering of Li-6 atoms
- 2010
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 82:2
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Tidskriftsartikel (refereegranskat)abstract
- Li-6 atoms in the three lowest hyperfine states display universal properties when the S-wave scattering length between each pair of states is large. Recent experiments reported four pronounced features arising from Efimov physics in the atom-dimer relaxation rate, namely two resonances and two local minima. We use the universal effective-field theory to calculate the atom-dimer relaxation rate at zero temperature. Our results describe the four features qualitatively and imply there is a hidden local minimum. In the vicinity of the resonance at 685 G, we perform a finite temperature calculation which improves the agreement of theory and experiment. We conclude that finite temperature effects cannot be neglected in the analysis of the experimental data.
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| 15. |
- Hammer, H. W., et al.
(författare)
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Pion-mass dependence of three-nucleon observables
- 2007
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Ingår i: European Physical Journal A. - 1434-601X .- 1434-6001. ; 32:3, s. 335-347
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Tidskriftsartikel (refereegranskat)abstract
- We use an effective field theory (EFT) which contains only short-range interactions to study the dependence of a variety of three-nucleon observables on the pion mass. The pion-mass dependence of input quantities in our "pionless" EFT is obtained from a recent chiral EFT calculation. To the order we work at, these quantities are the S-1(0) scattering length and effective range, the deuteron binding energy, the S-3(1) effective range, and the binding energy of one three-nucleon bound state. The chiral EFT input we use has the inverse S-3(1) and S-1(0) scattering lengths vanishing at m(pi)(crit) stop = 197.8577 MeV. At this "critical" pion mass, the triton has infinitely many excited states with an accumulation point at the three-nucleon threshold. We compute the binding energies of these states up to next-to-next-to-leading order in the pionless EFT and study the convergence pattern of the EFT in the vicinity of the critical pion mass. Furthermore, we use the pionless EFT to predict how doublet and quartet nd scattering lengths depend on m(pi) in the region between the physical pion mass and m(pi) = m(pi)(crit) stop .
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| 16. |
- Jaikumar, P., et al.
(författare)
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Muon production in low-energy electron-nucleon and electron-nucleus scattering
- 2007
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 2470-0010 .- 2470-0029. ; 76:11
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Tidskriftsartikel (refereegranskat)abstract
- Recently, muon production in electron-proton scattering has been suggested as a possible candidate reaction for the identification of lepton-flavor violation due to physics beyond the standard model. Here we point out that the standard-model processes e(-)p ->mu(-)p (nu) over bar (mu)nu(e) and e(-)p -> e(-)n mu(+)nu(mu) can cloud potential beyond-the-standard-model signals in ep collisions. We find that standard-model ep ->mu X cross sections exceed those from lepton-flavor-violating operators by several orders of magnitude. We also discuss the possibility of using a nuclear target to enhance the ep ->mu X signal.
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| 17. |
- Ji, C., et al.
(författare)
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The three-boson system at next-to-leading order in an effective field theory for systems with a large scattering length
- 2012
-
Ingår i: Annals of Physics. - : Elsevier BV. - 0003-4916 .- 1096-035X. ; 327:7, s. 1803-1824
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Tidskriftsartikel (refereegranskat)abstract
- We analyze how corrections linear in the effective range, r(0), affect quantities in the three-body sector within an effective field theory for short-range interactions. We demonstrate that observables can be obtained straightforwardly using a perturbative expansion in powers of r(0). In particular, we show that two linear-in-r(0) counterterms are needed for renormalization at this order if scattering-length-dependent observables are considered. We exemplify the implications of this result using various three-body observables. Analytical results for the running of the next-to-leading-order portion of the three-body force in this effective field theory are provided. Expressions which incorporate O(r(0)) corrections and relate the positions of features observed in three-atom recombination near a Feshbach resonance are presented.
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| 18. |
- Mishra, Chinmay, et al.
(författare)
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Two-pion exchange as a leading-order contribution in chiral effective field theory
- 2022
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Ingår i: Physical Review C. - 2469-9993 .- 2469-9985. ; 106:2
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Tidskriftsartikel (refereegranskat)abstract
- Pion exchange is the central ingredient to nucleon-nucleon interactions used in nuclear structure calculations, and one-pion exchange (OPE) enters at leading order in chiral effective field theory. In the 2S+1LJ=1S0 partial wave, however, OPE and a contact term needed for proper renormalization fail to produce the qualitative, and quantitative, features of the scattering phase shifts. Cutoff variation also revealed a surprisingly low breakdown momentum Λb≈330 MeV in this partial wave. Here we show that potentials consisting of OPE, two-pion exchange (TPE), and a single contact address these problems and yield accurate and renormalization group (RG) invariant phase shifts in the S01 partial wave. We demonstrate that a leading-order potential with TPE can be systematically improved by adding a contact quadratic in momenta. For momentum cutoffs Λ 500 MeV, the removal of relevant physics from TPE loops needs to be compensated by additional contacts to keep RG invariance. Inclusion of the Δ isobar degree of freedom in the potential does not change the strong contributions of TPE.
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| 19. |
- Platter, Lucas, 1976, et al.
(författare)
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Deuteron matrix elements in chiral effective theory at leading order
- 2006
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 641:2, s. 164-170
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Tidskriftsartikel (refereegranskat)abstract
- We consider matrix elements of two-nucleon operators that arise in chiral effective theories of the two-nucleon system. Generically, the short-distance piece of these operators scales as 1/r(n), with r the relative separation of the two nucleons. We show that, when evaluated between the leading-order wave functions obtained in this effective theory, these two-nucleon operators are independent of the cutoff used to renormalize the two-body problem for n=1 and 2. However, for n >= 3 general arguments about the short-distance behavior of the leading-order deuteron wave function show that the matrix element will diverge. (c) 2006 Elsevier B.V. All rights reserved.
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| 20. |
- Platter, Lucas, 1976
(författare)
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Low-Energy Universality in Atomic and Nuclear Physics
- 2009
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Ingår i: Few-Body Systems. - 1432-5411 .- 0177-7963. ; 46:3, s. 139-171
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Tidskriftsartikel (refereegranskat)abstract
- An effective field theory developed for systems interacting through short-range interactions can be applied to systems of cold atoms with a large scattering length and to nucleons at low energies. It is therefore the ideal tool to analyze the universal properties associated with the Efimov effect in three- and four-body systems. In this progress report, we will discuss recent results obtained within this framework and report on progress regarding the inclusion of higher order corrections associated with the finite range of the underlying interaction.
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| 21. |
- Platter, Lucas, 1976, et al.
(författare)
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On the correlation between the binding energies of the triton and the alpha-particle
- 2005
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 607:3-4, s. 254-258
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Tidskriftsartikel (refereegranskat)abstract
- We consider the correlation between the binding energies of the triton and the alpha-particle which is empirically observed in calculations employing different phenomenological nucleon-nucleon interactions. Using an effective quantum mechanics approach for short-range interactions with large scattering length \a\ much greater than l, where l is the natural low-energy length scale, we construct the effective interaction potential at leading order in l/\a\. In order to renormalize the four-nucleon system, it is sufficient to include a SU(4)-symmetric one-parameter three-nucleon interaction in addition to the S-wave nucleon-nucleon interactions. The absence of a four-nucleon force at this order explains the empirically observed correlation between the binding energies of the triton and the a-particle. We calculate this correlation and obtain a prediction for the a-particle binding energy. Corrections to our results are suppressed by l/\a\. (C) 2004 Elsevier B.V. All rights reserved.
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| 22. |
- Platter, Lucas, 1976, et al.
(författare)
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Quasiparticle properties in effective field theory
- 2003
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Ingår i: Nuclear Physics A. - 0375-9474. ; 714:1-2, s. 250-264
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Tidskriftsartikel (refereegranskat)abstract
- The quasiparticle concept is an important tool for the description of many-body systems. We study the quasiparticle properties for dilute Fermi systems with short-ranged, repulsive interactions using effective field theory. We calculate the proper self-energy contributions at order (k(F)/Lambda)(3), where A is the short-distance scale that sets the size of the effective range parameters and k(F) the Fermi momentum. The quasiparticle energy, width, and effective mass to O((k(F)/Lambda)(3)) are derived from the calculated self-energy. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 23. |
- Platter, Lucas, 1976, et al.
(författare)
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Scaling functions applied to three-body recombination of Cs-133 atoms
- 2008
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 78:6
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the implications of Efimov physics in the recently measured recombination rate of Cs-133 atoms. By employing previously calculated results for the energy dependence of the recombination rate of He-4 atoms, we obtain three independent scaling functions that are capable of describing the recombination rates over a large energy range for identical bosons with large scattering length. We benchmark these and previously obtained scaling functions by successfully comparing their predictions with full atom-dimer phase shift calculations with artificial He-4 potentials yielding large scattering lengths. Exploiting universality, we finally use these functions to determine the three-body recombination rate of Cs-133 atoms with large positive scattering length, compare our results to experimental data obtained by Kraemer at Innsbruck and find excellent agreement.
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| 24. |
- Platter, Lucas, 1976
(författare)
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Three-nucleon system at next-to-next-to-leading order
- 2006
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 74:3
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Tidskriftsartikel (refereegranskat)abstract
- We calculate higher order corrections for the three-nucleon system up to next-to-next-to-leading within an effective field theory with contact interactions alone. We employ a subtraction formalism previously developed and for which it has been shown that no new three-body force counterterm is needed for complete renormalization up to this order. We give results for the neutron-deuteron phaseshifts and the triton binding energy. Our results are in very good agreement with experimental results and calculations using realistic nucleon-nucleon potentials.
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| 25. |
- Platter, Lucas, 1976, et al.
(författare)
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Universal properties of the Four-Boson system in two dimensions
- 2004
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Ingår i: Few-Body Systems. - 1432-5411 .- 0177-7963. ; 35:3-4, s. 169-174
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Tidskriftsartikel (refereegranskat)abstract
- We consider the nonrelativistic four-boson system in two dimensions interacting via a short-range attractive potential. For a weakly attractive potential with one shallow two-body bound state with binding energy B-2, the binding energies B-N of shallow N-body bound states are universal and thus do not depend on the details of the interaction potential. We compute the four-body binding energies in an effective quantum mechanics approach. There are exactly two bound states: the ground state with B-4((0)) = 197.33(1)B-2 and one excited state with B-4((1)) = 25.5 (1)B-2. We compare our results to recent predictions for N-body bound states with large N much greater than 1.
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