EFFECTIVE FIELD THEORY FOR LATTICE NUCLEI

Transcription

1 EFFECTIVE FIELD THEORY FOR LATTICE NUCLEI Francesco Pederiva Physics Deparment Unversity of Trento INFN-TIFPA, Trento Institue for Fundamental Physics and Applications LISC, Interdisciplinary Laboratory for Computational Science International School of Nuclear Physics, 36th Course, Nuclei in the Laboratory and in the Cosmos Erice, September 16-24, 2014

2 Collaboration Jerusalem, Israel N Barnea, D Gazit J Kirscher Trento, Italy L Contessi Orsay, France U van Kolck ANL, USA A Lovato

3 PUNCHLINES This talk is about nuclei that do not exist neither in the laboratory nor in the cosmos, but only in our minds (and possibly in our computers) We want to understand if it is possible to infer some systematics and some general behaviors of nuclear physics in a regime where the pion mass is unphysical, but such that unquenched Lattice QCD simulations are possible Extrapolation to the physical case is very tricky and is not the main aim of this work at the moment Image from M Savage website (UW/INT)

4 Lattice QCD QCD is the fundamental theory for nuclear physics It is formulated in terms of quarks and gluons At low energy QCD is non-perturbative lattice simulations (LQCD) Neutron and proton masses are predictions Same for pion masses LQCD - The Single Baryon Case Xui-Lei Ren et al, PRD (2013) L Alvarez-Ruso et al, ArXiv hep-ph: (2013)

5 Lattice QCD QCD is the fundamental theory for nuclear physics It is formulated in terms of quarks and gluons At low energy QCD is non-perturbative lattice simulations (LQCD) Neutron and proton masses are predictions Same for pion masses LQCD - The Single Baryon Case Xui-Lei Ren et al, PRD (2013) L Alvarez-Ruso et al, ArXiv hep-ph: (2013)

6 Lattice QCD QCD is the fundamental theory for nuclear physics It is formulated in terms of quarks and gluons At low energy QCD is non-perturbative lattice simulations (LQCD) Neutron and proton masses are predictions Same for pion masses LQCD - The Single Baryon Case Xui-Lei Ren et al, PRD (2013) L Alvarez-Ruso et al, ArXiv hep-ph: (2013)

7 LQCD - Multi Baryon Configurations Deuteron (10) and dineutron (27) simulations Triton simulations with different lattice sizes ( , , ) LQCD simulations with SU f (3) symmetry Large pion mass m pi = 800MeV Results with smaller m π are already available NPLQCD Collaboration, PRD (2013)

8 LQCD - Few-Body Baryon Spectra 2-body system - Deutron, dineutron, 3-body system - 3 He, triton 4-body system - 4 He NPLQCD Collaboration, PRD (2013)

9 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

10 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

11 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

12 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

13 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

14 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

15 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

16 Effective Field Theory EFT in Nuclear Physics At this point LQCD simulations for A 2 nuclei are still far away from the physical value of the pion mass Currently no reliable and/or usable NN interactions can be derived from lattice simulations Contemporary nuclear theory is based on Effective Field Theory phenomenology Quark and Gluon degrees of freedom are replaced by baryons and mesons L QCD (q, G) L Nucl (N, π, ) The L Nucl (N, π, ) is constructed to retain QCD symmetries L Nucl (N, π, ) is an expansion in low momentum Q Contains all terms compatible with QCD up to a given order The low-energy coupling constants (LECs) are explicit function of the cutoff Λ

17 Effective Field Theory potentials Low Energy Constants There are 2 free parameters in LO, 7 at NLO, NNN and NNNN forces come in naturally at orders N2LO and N3LO The NNN force contains 2 free parameters ( ) 2 ga (σ V = 1 q)(σ 2 q) 2f π q 2 + m 2 τ 1 τ 2 π + C S + C T σ 1 σ 2 + V NLO + V N2LO + D R Entem and R Machleidt, PRC 68, (R) (2003) Epelbaum et al, EPJA 19, 401 (2004), NPA 747, 362 (2005)

18 Effective Field Theory potentials Low Energy Constants There are 2 free parameters in LO, 7 at NLO, NNN and NNNN forces come in naturally at orders N2LO and N3LO The NNN force contains 2 free parameters ( ) 2 ga (σ V = 1 q)(σ 2 q) 2f π q 2 + m 2 τ 1 τ 2 π + C S + C T σ 1 σ 2 + V NLO + V N2LO + D R Entem and R Machleidt, PRC 68, (R) (2003) Epelbaum et al, EPJA 19, 401 (2004), NPA 747, 362 (2005)

19 EFT for Lattice Nuclei Energy Scales Nucleon mass M n, and the difference with the mass of the baryon δm = M M n The pion mass m π, pion exchange momentum q π = m π / hc, and energy E π = h2 q 2 π M n = m π M n m π Nuclear binding energy B/A Scale Nature LQCD@m π =500MeV LQCD@m π =800MeV M n 940 MeV 1300 MeV 1600 MeV δm 300 MeV 300 MeV 180 MeV m π 140 MeV 500 MeV 800 MeV E π 20 MeV 200 MeV 400 MeV B/A 10 MeV 15 Mev 25 MeV Conclusions For the nature case L L EFT (N, π) For lattice nuclei at m π 400MeV, E π B/A In this case π/eft is the natural theory L L EFT (N)

20 The nucleon mass difference Nucleon mass - n,p mass L Alvarez-Ruso et al, ArXiv hep-ph: (2013)

21 π/eft for Lattice Nuclei We write all possible terms in the Lagrangian L ordered by the number of derivatives: ( L = N i 0 + ) N a 1 N NN N a 2 N σn N σn 2M a 3 N τn N τn a 4 N στn N στn + d 1 N τn N τnn N Higher order terms include more derivatives Naively, the order goes as the number of derivatives The 3-body term appears at LO to avoid the Thomas collapse Due to Fermi symmetry the number of terms can be cut by half The coefficients depend on the cutoff Λ Some further wishes (to be explained later) The potential needs to be local Avoid 3-body spin-isospin operators

22 π/eft for Lattice Nuclei We write all possible terms in the Lagrangian L ordered by the number of derivatives: ( L = N i 0 + ) N a 1 N NN N a 2 N σn N σn 2M a 3 N τn N τn a 4 N στn N στn + d 1 N τn N τnn N Higher order terms include more derivatives Naively, the order goes as the number of derivatives The 3-body term appears at LO to avoid the Thomas collapse Due to Fermi symmetry the number of terms can be cut by half The coefficients depend on the cutoff Λ Some further wishes (to be explained later) The potential needs to be local Avoid 3-body spin-isospin operators

23 At LO the π/eft potential takes the form π/eft Potential at NLO V 2b LO = a 1 + a 2 σ 1 σ 2 + a 3 τ 1 τ 2 + a 4 (σ 1 σ 2 )(τ 1 τ 2 ) The leading order also contains a 3-body term of the form V 3b LO = D 1τ 1 τ 2 At NLO the π/eft potential takes the form VNLO 2b = b 1 q 2 + b 2 q 2 σ 1 σ 2 + b 3 q 2 τ 1 τ 2 + b 4 q 2 (σ 1 σ 2 )(τ 1 τ 2 ) + b 5 k 2 + b 6 k 2 σ 1 σ 2 + b 7 k 2 τ 1 τ 2 + b 8 k 2 (σ 1 σ 2 )(τ 1 τ 2 ) + b 9 i 1 2 (σ 1 + σ 2 )(k q) + b 10 τ 1 τ 2 i 1 2 (σ 1 + σ 2 )(k q) + b 11 (σ 1 q)(σ 2 q) + b 12 τ 1 τ 2 (σ 1 q)(σ 2 q) + b 13 (σ 1 k)(σ 2 k) + b 14 τ 1 τ 2 (σ 1 k)(σ 2 k) The incoming particle have relative momentum p, the outgoing p The momentum transfer q = p p, and k = (p + p) Nonlocalities are associated with k The power counting changes for a shallow s-wave dimer J Kirscher, H W Griesshammer, D Shukla, H M Hofman, arxiv: A Gezerlis, I Tews, E Epelbaum, S Gandolfi, K Hebeler, A Nogga, A Schwenk, PRL 111, (2013)

24 At LO the π/eft potential takes the form π/eft Potential at NLO V 2b LO = a 1 + a 2 σ 1 σ 2 + a 3 τ 1 τ 2 + a 4 (σ 1 σ 2 )(τ 1 τ 2 ) The leading order also contains a 3-body term of the form V 3b LO = D 1τ 1 τ 2 At NLO the π/eft potential takes the form VNLO 2b = b 1 q 2 + b 2 q 2 σ 1 σ 2 + b 3 q 2 τ 1 τ 2 + b 4 q 2 (σ 1 σ 2 )(τ 1 τ 2 ) + b 5 k 2 + b 6 k 2 σ 1 σ 2 + b 7 k 2 τ 1 τ 2 + b 8 k 2 (σ 1 σ 2 )(τ 1 τ 2 ) + b 9 i 1 2 (σ 1 + σ 2 )(k q) + b 10 τ 1 τ 2 i 1 2 (σ 1 + σ 2 )(k q) + b 11 (σ 1 q)(σ 2 q) + b 12 τ 1 τ 2 (σ 1 q)(σ 2 q) + b 13 (σ 1 k)(σ 2 k) + b 14 τ 1 τ 2 (σ 1 k)(σ 2 k) The incoming particle have relative momentum p, the outgoing p The momentum transfer q = p p, and k = (p + p) Nonlocalities are associated with k The power counting changes for a shallow s-wave dimer J Kirscher, H W Griesshammer, D Shukla, H M Hofman, arxiv: A Gezerlis, I Tews, E Epelbaum, S Gandolfi, K Hebeler, A Nogga, A Schwenk, PRL 111, (2013)

25 At LO the π/eft potential takes the form π/eft Potential at NLO V 2b LO = a 1 + a 2 σ 1 σ 2 + a 3 τ 1 τ 2 + a 4 (σ 1 σ 2 )(τ 1 τ 2 ) The leading order also contains a 3-body term of the form V 3b LO = D 1τ 1 τ 2 At NLO the π/eft potential takes the form VNLO 2b = b 1 q 2 + b 2 q 2 σ 1 σ 2 + b 3 q 2 τ 1 τ 2 + b 4 q 2 (σ 1 σ 2 )(τ 1 τ 2 ) + b 5 k 2 + b 6 k 2 σ 1 σ 2 + b 7 k 2 τ 1 τ 2 + b 8 k 2 (σ 1 σ 2 )(τ 1 τ 2 ) + b 9 i 1 2 (σ 1 + σ 2 )(k q) + b 10 τ 1 τ 2 i 1 2 (σ 1 + σ 2 )(k q) + b 11 (σ 1 q)(σ 2 q) + b 12 τ 1 τ 2 (σ 1 q)(σ 2 q) + b 13 (σ 1 k)(σ 2 k) + b 14 τ 1 τ 2 (σ 1 k)(σ 2 k) The incoming particle have relative momentum p, the outgoing p The momentum transfer q = p p, and k = (p + p) Nonlocalities are associated with k The power counting changes for a shallow s-wave dimer J Kirscher, H W Griesshammer, D Shukla, H M Hofman, arxiv: A Gezerlis, I Tews, E Epelbaum, S Gandolfi, K Hebeler, A Nogga, A Schwenk, PRL 111, (2013)

26 Due to antisymmetrization of the nuclear wave function VLO 2b = CLO 1 + C LO 2 σ 1 σ 2 The leading order also contains a 3-body term of the form V 3b LO = DLO 1 τ 1 τ 2 Using the freedom to choose these parameters we set V 2b NLO = CNLO 1 q 2 + C NLO 2 q 2 σ 1 σ 2 + C NLO 3 q 2 τ 1 τ 2 + C NLO 4 q 2 (σ 1 σ 2 )(τ 1 τ 2 ) + C NLO 5 i 1 2 (σ 1 + σ 2 )(k q) + C NLO 6 (σ 1 q)(σ 2 q) + C NLO 7 τ 1 τ 2 (σ 1 q)(σ 2 q) The antisymmetric potential V NLO contains 1 LO 2-body: 2 parameters 2 LO 3-body: 1 parameter 3 NLO: 7 parameters At the moment we consider only LO

27 We introduce a Gaussian cutoff in q F Λ (q) = Coordinate space ( ) 3 4π e q2 /Λ 2 = F Λ (r) = e Λ2 r 2 /4 The potential matrix elements can be evaluated now Λ V(r, r ) = N r dkdqv(k, q)f Λ (q) r = N V( i y, i x ) e Λ2 x 2 /4 δ(y) where x = 1 2 (r + r ) ; y = 1 2 (r r) The LO potential contains no momentum dependence therefore V 2b LO (r) = ( C LO 1 + C LO 2 σ 1 σ 2 ) e Λ2 r 2 /4 With our choice of parameterization also V NLO is local The 3-body term takes the form V 3b LO = DLO 1 τ 1 τ 2 e Λ2 (r r2 23 )

28 The Hamiltonian At leading order the coordinate space Hamiltonian is H = i h 2 ( 2 i + 2M n i<j C LO 1 + D LO 1 (Λ) ( ) Λ τ i τ j e 2 (r 2 ik +r2 jk ) i<j<k cyc ) (Λ) + CLO 2 (Λ) σ i σ j e Λ2 r 2 ij In the 3-body term the notation cyc stands for cyclic permutation of particles (ijk) We use four methods 1 Numerov, A = 2 2 The Effective Interaction Hypershperical Harmonics (EIHH) method, 6 A 3 3 (Refined) Resonating Group Model (RRGM) for N 12 4 The Auxiliary Field Diffusion Monte-Carlo (AFDMC) method, A 2

29 Auxiliary Field Diffusion Monte Carlo In order to extend the prediction to heavier mass nuclei we employ a QMC algorithm, namely AFDMC The Fermion ground state of the Hamiltonian is computed by means of imaginary time projection with constraints to avoid the sign problem R, S 0 A lim τ R, S e ( H E 0 )τ R S R S Ψ A population of points R, S in the coordinate/spin space evolved in imaginary time H is a modified Hamiltonian defined on a set of artificial boundary conditions imposed to obtain a finite overlap with an antisymmetric function

30 Auxiliary Field Diffusion Monte Carlo The propagator contains operators that span a multicomponent wavefunction with order 4 A components This is the approach used in GFMC calculations In AFDMC we make use of a basis set in which the single particle wavefunctions take the form ( ) αi ϕ(r i, s i ) = φ β n (r i ) i Linearization of the operators is achieved through the Hubbard-Stratonovitch transform As an example, the propagator corresponding to ˆV = v σ σ (r 12 )σ 1 σ 2 is: e ˆV τ = 1 π dx1 e x2 1 2 e x 1 τvσ σ(r 12 )σ 1 dx 2 e x2 2 2 e x 2 τvσ σ(r 12 )σ 2

31 Auxiliary Field Diffusion Monte Carlo PRO: Very favorable scaling (A 3 instead of 4 A ) No problem in computing nuclei up to A = 90 CON: Limited freedom on the choice of the trial functions some possible ambiguities in the results No upper bound property No easy way to include spin-orbit and three body forces in the propagator for finite nuclei (no problems in pure neutron systems instead)

32 The Experimental data There are 4 input parameters in our model: 1 The nucleon mass M n 2 LECs: C LO 1 (Λ), CLO 2 (Λ), DLO 1 (Λ) Table : Masses [MeV] particle LQCD Nature π 8059 ± n ± p ± Table : Binding energies [MeV] nuclei LQCD Nature D -195 ± nn -159 ± 38-3 H -539 ± He -539 ± He ± NPLQCD Collaboration, PRD (2013)

33 The Experimental data There are 4 input parameters in our model: 1 The nucleon mass M n 2 LECs: C LO 1 (Λ), CLO 2 (Λ), DLO 1 (Λ) Table : Masses [MeV] particle LQCD Nature π 8059 ± n ± p ± Table : Binding energies [MeV] nuclei LQCD Nature D -195 ± nn -159 ± 38-3 H -539 ± He -539 ± He ± NPLQCD Collaboration, PRD (2013)

34 The 2-body LECs The 2-body potential is diagonal in the S, T basis VS,T LO(r; Λ) = S, T VLO (r; Λ) S, T { = C LO 1 (Λ) + [2S(S + 1) 3]CLO 2 (Λ) } F Λ (r) C LO ST (Λ)F Λ(r) C LO ST (Λ) are fitted to the D, nn BE We expect to get C S=1,T=0 LO [MeV] Λ [fm 1 ] a s 1/ m N B For LQCD@m π = 800MeV a LO S=0,T=1 = 14 ± 020 fm a LO S=1,T=0 = 12 ± 020 fm

35 The 2-body LECs The 2-body potential is diagonal in the S, T basis VS,T LO(r; Λ) = S, T VLO (r; Λ) S, T { = C LO 1 (Λ) + [2S(S + 1) 3]CLO 2 (Λ) } F Λ (r) C LO ST (Λ)F Λ(r) C LO ST (Λ) are fitted to the D, nn BE We expect to get C S=1,T=0 LO [MeV] Λ [fm 1 ] a s 1/ m N B For LQCD@m π = 800MeV a LO S=0,T=1 = 14 ± 020 fm a LO S=1,T=0 = 12 ± 020 fm

36 The 2-body LECs The 2-body potential is diagonal in the S, T basis VS,T LO(r; Λ) = S, T VLO (r; Λ) S, T { = C LO 1 (Λ) + [2S(S + 1) 3]CLO 2 (Λ) } F Λ (r) C LO ST (Λ)F Λ(r) C LO ST (Λ) are fitted to the D, nn BE We expect to get C S=1,T=0 LO [MeV] Λ [fm 1 ] a s 1/ m N B For LQCD@m π = 800MeV a LO S=0,T=1 = 14 ± 020 fm a LO S=1,T=0 = 12 ± 020 fm

37 Calibration of D 1 4 He binding energy without NNN force Λ EIHH AFDMC [fm 1 ] [MeV] [MeV] LQCD -1070±242 The span in the binding energies is reflected in the parameters We shall use only the central values

38 Calibration of D 1 4 He binding energy without NNN force 3 He Binding Energy [MeV] Λ EIHH AFDMC [fm 1 ] [MeV] [MeV] LQCD -1070±242 Λ = 2 fm 1 The span in the binding energies is reflected in the parameters We shall use only the central values D LO 1 [MeV]

39 Calibration of D 1 4 He binding energy without NNN force Λ EIHH AFDMC [fm 1 ] [MeV] [MeV] LQCD -1070±242 D 1 LO [MeV] He Binding Energy [MeV] Λ = 2 fm Λ [fm 1 ] The span in the binding energies is reflected in the parameters We shall use only the central values D LO 1 [MeV]

40 Few Predictions The binding energy of 4 He Λ EIHH AFDMC [fm 1 ] [MeV] [MeV] (1) -877(1) (1) -933(2) (3) -992(2) (12) -1103(2) LQCD -1070±242 The computed 4 He energy is within the LQCD simulations uncertainty It has residual cutoff dependence The radii of D, 3 He, 4 He exhibit strong cutoff dependence These issues might be artifacts of our local formalism 4 He - Binding energy AFDMC EIHH Λ [fm 1 ]

41 Few Predictions The binding energy of 4 He Λ EIHH AFDMC [fm 1 ] [MeV] [MeV] (1) -877(1) (1) -933(2) (3) -992(2) (12) -1103(2) LQCD -1070±242 The computed 4 He energy is within the LQCD simulations uncertainty It has residual cutoff dependence The radii of D, 3 He, 4 He exhibit strong cutoff dependence These issues might be artifacts of our local formalism 4 He - Binding energy Radius [fm] AFDMC EIHH Λ [fm 1 ] D 3 He 4 He Λ [fm ]

42 The Tjon line(?) He Binding Energy [MeV] Λ = 2 fm He Binding Energy [MeV] Conclusion The EFT error due to uncertainty in the binding energy of 3 He is roughly as large as the 4 He measurment error

43 The Tjon line(?) He Binding Energy [MeV] Λ = 2 fm He Binding Energy [MeV] Conclusion The EFT error due to uncertainty in the binding energy of 3 He is roughly as large as the 4 He measurment error

44 Few more predictions Binding energies of the Light nuclei nuclei LQCD EFT Λ = 2 fm 1 D -195 ± nn -159 ± H, 3 He -539 ± n, 3 p unbound 4 He ± He J π = (?) 5 He Li -121(3)

45 » Å Î Saturation Energy on the Lattice ÄÇ ÄÉ Æ ØÙÖ Æ ØÙÖ 4 ÈÖ Ð Ñ Ò ÖÝ ÈÖ Ð Ñ Ò ÖÝ

46 Even more predictions We were able to perform calculations of 16 O AFDMC calculations are non-trivial, especially at large Λ due to the large cancelations in the attractive (2-body) and repulsive (3-body) components in the potential Table : Binding energies of 16 O from FDMC calculations (MeV) Λ (fm 1 ) m π (MeV) (3) 3349(6) 324(1) 305(1) (4) 1080(4) 1058(8) 100(1) (2) 569(6) 48(1) 45(2) Comments The three-body force used here has no isospin dependence (should be equivalent, but there might be some redundance) As it stands, 16 O is unbound with respect to breakup in 4( 4 He) However, at m π = 805MeV the difference BE( 4 He) BE( 16 O)/4 can be as small as 14MeV There are still convergence issues (in the cutoff Λ), and the problems needs to be explored more in detail

47 Even more predictions We were able to perform calculations of 16 O AFDMC calculations are non-trivial, especially at large Λ due to the large cancelations in the attractive (2-body) and repulsive (3-body) components in the potential Table : Binding energies of 16 O from FDMC calculations (MeV) Λ (fm 1 ) m π (MeV) (3) 3349(6) 324(1) 305(1) (4) 1080(4) 1058(8) 100(1) (2) 569(6) 48(1) 45(2) Comments The three-body force used here has no isospin dependence (should be equivalent, but there might be some redundance) As it stands, 16 O is unbound with respect to breakup in 4( 4 He) However, at m π = 805MeV the difference BE( 4 He) BE( 16 O)/4 can be as small as 14MeV There are still convergence issues (in the cutoff Λ), and the problems needs to be explored more in detail

48 Summary of AFDMC results for m π =805 MeV Binding energy [MeV] λ = 2 fm 1 λ = 4 fm 1 λ = 6 fm 1 λ = 8 fm Number of nucleons

49 Summary of AFDMC results for m π =510 MeV Binding energy [MeV] λ = 2 fm 1 λ = 4 fm 1 λ = 6 fm 1 λ = 8 fm Number of nucleons

50 Summary of AFDMC results for m π =140 MeV Binding energy [MeV] λ = 2 fm 1 λ = 4 fm 1 λ = 6 fm 1 λ = 8 fm Number of nucleons

51 Summary and Conclusions 1 Lattice QCD simulations of few-nucleon systems open up a new front in nuclear physics 2 π/eft is the appropriate theory to study these Lattice Nuclei, down to rather small pion masses 3 Fitted to recent LQCD data we found that π/eft@lo reproduces the 4 He binding energy for m π = 805MeV and m π = 510MeV nucleons 4 The np, nn scattering lengths for this system are about a factor of 2 too small in comparison with recent NPLQCD calculations 5 At LO we see probelms with the calculated nuclear radii 6 More LQCD data are avilable to go behyond LO

52 Ongoing work Begin the journey to include NLO in calculations More LQCD data at different m π to understand the systematics of some properties (eg evolution of the LEC s, BEs, saturation, ) Larger (A = 40) calculations, and better wavefunctions in AFDMC (eg from RRG to check the cluster structyre in 16 O) Redo the calculations using a recently developed QMC algorithm in momentum space: systematic comparison of non-local and local formulation (effect of regulators?) as a function of the mass