Higher-order recoil corrections in Helium and Helium-like ions

Transcription

1 Higher-order recoil corrections in Helium and Helium-like ions Vojtěch Patkóš Department of Chemical Physics and Optics Charles University in Prague 19th May 2017

2 Motivation Motivation Hydrogenic systems such as H, He + or µh are being considered for low-energy tests of the Standard model and for determination of fundamental constants Comparison of accurate experimental values for transition frequencies with theoretical predictions gives us information about the extent to which energy levels can by predicted by the Standard model Any discrepancy would be signal of new physics or incorrect values of physical constants

3 Motivation One can reverse the problem and use the comparison of experimental values with theoretical predictions to extract values of fundamental constants Example of this is using the measurement of anomalous magnetic moment of bound electron in H-like carbon ions with high precision theoretical predictions for determination of electron mass This method improves the accuracy for determination of electron mass by two orders of magnitude

4 Motivation Another example is comparison of the Lamb shift in muonic hydrogen with electronic one This provides us with significantly different values of proton charge radius r 2 p eh = (45) fm r 2 p µh = (4) fm

5 Motivation Existence of interactions that are not accounted for? Lack of universality in lepton-hadron interaction? Incorrect values of physical constants?

6 Motivation Recent results indicates that value of Rydberg constant is incorrect and previous hydrogen measurements were not as accurate as claimed and same holds for determination of r p from proton scattering This still requires further confirmation Another experiment aimed in resolving the proton radius puzzle is the direct comparison of the e p to µ p scattering cross section

7 Motivation Present electronic and muonic hydrogen theory allows accurate determination of the proton charge radius from measured transition frequencies, and the comparison between electronic and muonic results stands as a low-energy test of the Standard Model Purpose of our calculations is to bring the high accuracy achieved for hydrogenic levels to few-electron atomic and molecular systems and in particular for helium and helium-like ions

8 Motivation Contribution of the nuclear finite size effect to energy levels is δ fs E = 2πZα φ 2 (0) rch 2 3 = C r ch 2 Determination of the nuclear charge radius comes from r 2 ch = E exp E theo C For 2 3 S 2 3 P transition in 4 He δ fs E 3.5 MHz. To obtain r ch with accuracy of few parts in 10 3 one has to calculate the transition energies on 10 khz level.

9 Method Case of hydrogen Dirac equation (with infinite nuclear mass) One-loop self-energy and vacuum polarization E = α π (Zα)4 [ A 40 + (Zα) A 50 + (Zα) 2 (A 62 ln 2 (Zα) 2 + A 61 ln(zα) 2 + A 60 + Two-loop correction E = ( ) α 2 [ (Zα) 4 B 40 + (Zα) B 50 + (Zα) 2 (B 63 ln 3 (Zα) 2 π +B 62 ln 2 (Zα) 2 + +B 61 ln(zα) 2 + B 60 Recoil corrections

10 Method Case of helium Calculation of relativistic corrections to energy levels of atomic systems is usually acomplished by using many-electron Dirac-Coulomb Hamiltonian with possible inclusion of Breit interaction between electrons Such a Hamiltonian can not be rigorously derived from QED and thus gives incomplete treatment of relativistic and QED effects Electron self-energy and vacuum polarization can be included in the DC Hamiltonian, although only in approximate way

11 Method NRQED Alternative approach called Non-relativistic Quantum electrodynamics relies on expansion of energy levels in powers of the fine structure constant E(α) = E (2) + E (4) + E (5) + E (6) + E (7) +, E (n) m α n All expansion terms are expressed in terms of expectation values of some effective Hamiltonian with nonrelativistic wave function

12 Method Every term is then expanded in powers of the electron-to-nucleus mass ratio m/m E (n) = E (n) + m ( m ) 2 M δ ME (n) + O M E (2) is a nonrelativistic energy corresponding to the Hamiltonian H (2) = ( ) 2 p a 2m Zα + α + 2 P I r a ai r ab 2M a>b b

13 Method E (4) is leading relativistic correction, H (4) = a [ p 4 a E (4) = H (4) 8 m 3 + πz α 2 m 2 δ3 (r ai ) + Z α 4 m 2 σ a r ] ai p a { π α r 3 ai α ( δ ij 2 m 2 pi a + r ab i r j ) ab p j r b ab + m 2 δ3 (r ab ) r 3 a<b ab 2π α 3 m 2 σ a σ b δ 3 (r ab ) + α σa i σ j ( b 4 m 2 rab 3 δ ij 3 r ab i r j ) ab rab 2 α [ ( ) + 2 σa 4 m 2 rab 3 r ab p b σ b r ab p a + ( )] } σ b r ab p b σ a r ab p a

14 Method E (5) stands for the leading QED correction, [ 164 E (5) = ] ] α 2 ln α 3 m 2 δ3 (r 12 ) [ ] 19 4α Z ln(zα) 2 3 m 2 δ3 (r 1 ) + δ 3 (r 2 ) 14 ( ) 1 3 mα5 4 π P 1 (mα r 12 ) 3 2 α [ 2(H 3 π m 2 p a (H (2) E (2) (2) E (2) ] ) ) ln (Zα) 2 p b m a b

15 Method Higher-order term E (6) consists of two parts, E (6) = H (6) + H (4) 1 (E (2) H (2) ) H(4) Here H (6) = i=1..11 Both parts contain singular operators like r 3 12, r 4 12 etc H i

16 Method It is necessary to perform regularization in order to isolate singular parts of all terms. These singularities eventually cancel each other Particular regularization scheme we choose is dimensional regularization d = 3 d = 3 2ɛ All the singularities 1 ɛ then cancel each other

17 Method After simplification the terms are expressed in terms of operators Q 1, Q 2,, Q 55 which are suitable for numeric calculation Q 1 = 4πδ 3 (r 1 ) Q 2 = 4πδ 3 (r 12 ) Q 3 = 4πδ 3 (r 1 )/r 2 Q 4 = 4πδ 3 (r 1 ) p 2 2 Q 5 = 4πδ 3 (r 12 )/r 1 Q 6 = 4π p δ 3 (r 12 ) p, p = ( p 1 p 2 )/2 Q 7 = 1/r 12 Q 8 = 1/r

18 Numerical calculation For the Helium wave function we use expansion in the bases set of exponential functions of the Korobov type, φ( 3 S) = φ( 3 P) = φ( 1 S) = φ( 1 P) = N [ v i e α i r 1 β i r 2 γ i r (r 1 r 2 ) ] i=1 N [ v i r1 e α i r 1 β i r 2 γ i r (r 1 r 2 ) ] i=1 N [ v i e α i r 1 β i r 2 γ i r + (r 1 r 2 ) ] i=1 N [ v i r1 e α i r 1 β i r 2 γ i r + (r 1 r 2 ) ] i=1

19 Numerical calculation The calculation of matrix elements of the nonrelativistic Hamiltonian is based on the single master integral, 1 16π 2 d 3 r 1 d 3 r 2 e αr 1 βr 2 γr r 1 r 2 r = 1 (α + β)(β + γ)(γ + α) The integrals with any additional powers of r i in the numerator can be obtained by differentiation with respect to the corresponding parameter α, β or γ

20 Results Results Theoretical contributions to the centroid ionization energy of 1 1 S state in 4 He, in MHz. (m/m) 0 (m/m) 1 (m/m) 2 (m/m) 3 Sum α α α α α (36.) 71. (36.) NS 29.7 (1) 29.7 (1) Total (36.) K. Pachucki, V. Patkóš, V. A. Yerokhin: Testing fundamental interactions on the helium atom, sent to Phys. Rev. A

21 Results Comparison of the theoretical predictions for various transitions in 4 He with the experimental results, in MHz. Theory Experiment 1 1 S (36) (6) 1 1 S 2 1 S (36) (48) 2 3 S 3 3 D (1.3) (56) 2 1 S 2 1 P (2.3) (183) 2 1 P D (0.4) (268) 2 3 P D (0.7) (28) 2 3 P 2 3 S (2.0) (2) 2 3 S 2 1 P (1.4) (5) 2 1 S 2 3 S (0.8) (18)

22 Results 3 He 4 He isotope shift of the 2 3 S 2 3 P centroid transition energy in khz (m/m) 1 (m/m) 2 (m/m) 3 Sum α α α α α (0.9) 0.0 (0.9) NPOL EMIX Total (0.9) δr 2 ch (Florence 2012, 23 P 2 3 S) = (3) fm 2 δr 2 ch (Shiner 1995, 23 P 2 3 S) = (3) fm 2 δr 2 ch (Amsterdam 2011, 21 S 2 3 S) = (11) fm 2 V. Patkóš, V. A. Yerokhin and K. Pachucki, Phys. Rev. A 95, (2017) V. Patkóš, V. A. Yerokhin and K. Pachucki, Phys. Rev. A 94, (2016)

23 Results Conclusions By calculating the higher-order terms E (6) and E (7) we will achieve the same accuracy of theoretical calculations for helium as in the hydrogenic case Such an accuracy will enable us to get absolute nuclear charge radius and in general to carry out low-energy tests of Standard model and its extensions The next step is to calculate contribution of the leading term in E (7) contribution Further application is to calculate leading E (6) contribution for Lithium atom

24 Results Collaborators Krzysztof Pachucki, University of Warsaw Vladimir A. Yerokhin, St. Petersburg Technical university Jaroslav Zamastil, Charles University in Prague