Nab experiment: progress update Dinko Po cani c, for the Nab - PowerPoint PPT Presentation

Nab experiment: progress update Dinko Poˇ cani´ c, for the Nab Collaboration University of Virginia FnPB PRAC Review 15 December 2010 D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 1 / 27

n-decay program at FnPB The FnPB neutron decay program at SNS ◮ Nab : a precise measurement of ◦ a , the electron-neutrino correlation in neutron decay, and ◦ b , the Fierz interference term, never before measured in n decay. ◮ Polarized program (abBA/PANDA): precise measurements of ◦ A , the electron asymmetry in neutron decay, ◦ B , the neutrino asymmetry in neutron decay, ◦ C , the proton asymmetry in neutron decay; also ◦ independent measurements of a and b . δ v / v ≤ 10 − 3 , δ b ≤ 3 × 10 − 3 . Typical goal uncertainties: and D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 2 / 27

Motivation, goals Neutron Decay Parameters (SM) dw ≃ k e E e (E 0 − E e ) 2 dE e dΩ e dΩ ν � k e · � � � � � k ν + b m k e k ν � � × 1 + a + � � σ n � · A + B + . . . E e E ν E e E e E ν where: A = − 2 | λ | 2 + Re( λ ) a = 1 − | λ | 2 1 + 3 | λ | 2 1 + 3 | λ | 2 B = 2 | λ | 2 − Re( λ ) λ = G A ( with τ n ⇒ CKM V ud ) 1 + 3 | λ | 2 G V also: C = κ (A + B) where κ ≃ 0 . 275 . D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 3 / 27

Motivation, goals Goals of the Nab experiment ◮ Measure the electron-neutrino parameter a in neutron decay ∆a ≃ 10 − 3 with accuracy of a − 0 . 1054 ± 0 . 0055 Byrne et al ’02 current results: − 0 . 1017 ± 0 . 0051 Stratowa et al ’78 − 0 . 091 ± 0 . 039 Grigorev et al ’68 ◮ Measure the Fierz interference term b in neutron decay ∆b ≃ 3 × 10 − 3 with accuracy of current results: none D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 4 / 27

CKM matrix: V ud Status of A and λ in n decay Average: A =�-0.1186(9) Bopp-86 Uncertainty of the average Yeroz-97 scaled up by factor 2 . 3 × Global fit χ 2 / dof = 28 / 5 ! Liaud-97 Statistical probability for this Abele-02 χ 2 is 5 × 10 − 5 . H. Abele, private communication (2009). Pattie-09 R.W. Pattie, et al., PRL 102 , 012301 (2009). H. Abele et al., PRL 88 , 211801 (2002). P. Liaud et al., NP A 612, 53 (1997). B. Yerozolimsky et al., PL B 412 , 240 (1997). Abele-09 P. Bopp et al., PRL 56 , 919 (1986). -0.13 -0.12 -0.11 -0.10 Beta Asymmetry A D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 5 / 27

CKM matrix: V ud Status of A and λ in n decay (cont’d) Nab goal value of ∆ a : ⇒ ∆ λ ≃ 3 . 5 × 10 − 4 i.e., an order of magn. improvement. ∆ λ ≃ 0 . 27 ∆ a ≃ 0 . 24 ∆ A λ a A D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 6 / 27

Beyond V ud n-decay Correlation Parameters Beyond V ud ◮ Beta decay parameters constrain L-R symmetric, SUSY extensions to the SM. [ Reviews: Herczeg, Prog. Part. Nucl. Phys. 46 , 413 (2001), N. Severijns, M. Beck, O. Naviliat-ˇ Cunˇ ci´ c, Rev. Mod. Phys. 78 , 991 (2006), Ramsey-Musolf, Su, Phys. Rep. 456 , 1 (2008)] ◮ Fierz int. term, never measured for the n , along with B , offers a sensitive test of non-( V − A ) terms in the weak Lagrangian ( S , T ). [ S. Profumo, M. J. Ramsey-Musolf, S. Tulin, PRD 75 , 075017 (2007)] ◮ Measurement of the electron-energy dependence of a and A can separately confirm CVC and absence of SCC. [ Gardner, Zhang, PRL 86 , 5666 (2001), Gardner, hep-ph/0312124] ◮ A connection exists between non-SM (e.g., S , T ) terms in d → ue ¯ ν and limits on ν masses. [ Ito + Pr´ ezaeu, PRL 94 (2005)] D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 7 / 27

Beyond V ud non- V − A interaction terms Updated limits for RH S and T currents n decay 0.15 0.15 2 2 Δχ C.L. Δχ C.L. “present�limits” “ future�limits ” (68%�C.L.) 2.30 68.3% 2.30 68.3% (68%�C.L.) 0.10 0.10 4.61 90% 4.61 90% 6.17 95.4% 6.17 95.4% 0.05 0.,05 neutrino neutrino�mass mass (68%�C.L.) (68%�C.L.) R T / L A 0.00 R T / L A 0.00 -0.05 -0.,05 muon�decay muon�decay “90%�C.L.” “ 90%�C.L. ” -0.10 -0.10 neutron and nuclear�decays neutrino�mass neutron�and�nuclear�decays neutrino�mass (survey,�95%�C.L.) (68%�C.L.) (survey,�95%�C.L.) (68%�C.L.) -0.15 -0.15 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 R S / L V R / L S V Present limits ( n decay data) Projected limits; Grey contours: (SM values at origin of plot.) β compilation [Sev-06] Improvement from more precise a = − 0 . 1030(1); using b ≡ 0. [G. Konrad, W. Heil, S. Baeßler, D. Poˇ cani´ c, F. Gl¨ uck, arXiv 1007.3027.] D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 8 / 27

Beyond V ud non- V − A interaction terms Limits for LH S and T currents n decay 0.3 0.04 2 Δχ C.L. muon�decay “ present�limits ” 0.04 “ future�limits ” 2.30 68.3% (68%�C.L.) “ 90%�C.L. ” 0.2 (68%�C.L.) 4.61 90% neutron�and 0.02 6.17 95.4% nuclear�decays 0.1 (survey,�68%�C.L.) 2 Δχ C.L. L T / L A 0.0 L T / L A 0.00 2.30 68.3% 4.61 90% neutron�and -0.1 -0.02 95.4% nuclear�decays 6.17 (survey,�68%�C.L.) -0.2 superallowed superallowed + + +������������+ nuclear�decays 0 → 0 decays -0.04 nuclear�decays 0 → 0 decays 107 (68%�C.L.) 107 ( (���In),�90%�C.L.) P ( (���In),�90%�C.L.) P (68%�C.L.) -0.3 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 -0.04 -0.02 0.00 0.02 0.04 L S / L V L S / L V Present limits ( n decay data) Projected limits assuming (SM values at origin of plot.) a = − 0 . 1030(1) ; b = 0 ± 0 . 003 [G. Konrad, W. Heil, S. Baeßler, D. Poˇ cani´ c, F. Gl¨ uck, arXiv 1007.3027.] D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 9 / 27

Beyond V ud non- V − A interaction terms Right-handed W bosons Adding RH gives non-zero δ = m 2 1 / m 2 2 , ζ : W 1 = W L cos ζ + W R sin ζ , and W 2 = − W L sin ζ + W R cos ζ . Mass�m��[GeV] Mass�m��[GeV] 2 Mass�ratio δ 2 Δχ Δχ 2 μ decays Δχ C.L. μ decays 250 Mass�ratio δ C.L. C.L. 0.10 0.05 (90%�C.L.) (90%�C.L.) + + 2.30 68.3% + + 2.30 68.3% 2.30 68.3% 0 → 0 0 → 0 decays decays 90% 4.61 4.61 90% 90% 4.61 2 2 (68%�C.L.) 0.08 (68%�C.L.) 0.04 400 6.17 95.4% 95.4% 6.17 95.4% 6.17 300 μ decays “ future�limit ” (68%�C.L.) 0.06 0.03 μ decays (68%�C.L.) (68%�C.L.) 350 500 lepton 0.04 400 0.02 scattering lepton 600 (90%�C.L.) “ present scattering 450 limits ” (90%�C.L.) 500 700 550 0.02 (68%�C.L.) 0.01 800 DØ�(95%�C.L.) 600 900 DØ�(95%�C.L.) 1000 0.00 0.00 -0.2 -0.1 0.0 0.1 -0.10 -0.05 0.00 0.05 Mixing�angle ζ Mixing�angle ζ Present limits Projected limits [G. Konrad, W. Heil, S. Baeßler, D. Poˇ cani´ c, F. Gl¨ uck, arXiv 1007.3027.] D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 10 / 27

Beyond V ud Fierz interference term The Fierz interference term b b can be estimated from nuclear beta decays: C S C V C T C A b F = b GT = | C S | 2 + | C V | 2 | C T | 2 + | C A | 2 These terms vanish for pure ν ( R ) coupling. b � = 0 only for S , T coupling to ν ( L ) . (leptoquarks?) From 0 + → 0 + decays [Towner + Hardy ’98] : | b F | ≃ | C S | | C V | ≤ 0 . 0077 (90 % c . l . ) From analysis of GT decays [Deutsch + Quin, ’95] : b GT = − 0 . 0056(51) ≃ C T (small F T from π e 2 γ !?) | C A | ⇒ a ∼ 10 − 3 measurement of b n is very interesting! D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 11 / 27

Beyond V ud Second class currents Correlation Parameters with Recoil Correction [Gardner, Zhang, PRL 86 , 5666 (2001), Gardner, hep-ph/0312124] Most general form of hardonic weak current consistent with (V-A): � p(p p ) | J µ | n(p n , P) � = f 1 (q 2 ) γ µ − if 2 (q 2 ) q µ + f 3 (q 2 ) � q µ + g 1 (q 2 ) γ µ γ 5 u p (p p ) ¯ M n M n − ig 2 (q 2 ) σ µν γ 5 q ν + g 3 (q 2 ) � γ 5 q µ u n (p n , P) M n M n a , A , B ⇒ λ = g 1 τ n ∝ (f 1 ) 2 + 3(g 1 ) 2 while f 1 However, f 2 (weak magnetism) and SCC’s ( g 2 , g 3 ), remain unresolved in beta decays (best tested in A=12 system). With recoil corrections, Gardner and Zhang find: a(E e ) = func (f 2 ) while A(E e ) = func (f 2 , g 2 ) D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 12 / 27

Beyond V ud Second class currents 0.004 0.002 0 (1) (1) and A -0.002 a -0.004 -0.006 -0.008 0.4 0.5 0.6 0.7 0.8 0.9 x D. Poˇ cani´ c (UVa) Nab progress update 15 Dec ’10 13 / 27