The planned Nab/abBA/PANDA spectrometer Stefan Bae ler The - PowerPoint PPT Presentation

The planned Nab/abBA/PANDA spectrometer Stefan Bae β ler

The Spallation Neutron Source SNS in Oak Ridge, TN Linear H - accelerator Accumulator ring (buncher) Target Target Guide Hall

Usage of neutrons @ SNS 7 - Engineering 11A - Powder 9 – Diffractometer Diffractometer VISION IDT CFI Funded Commission 2007 Commission 2008 C i i 2008 6 - SANS 12 - Single Crystal Commission 2007 Diffractometer Commission 2009 5 - Cold Neutron 13 - Fundamental Chopper Physics Beamline Spectrometer Commission 2008 Commission 2007 4B - Liquids Reflectometer 14B - Hybrid Commission 2006 Spectrometer Commission 2011 4A - Magnetism Reflectometer C Commission 2006 i i 2006 15 – Spin Echo 3 - High Pressure 17 - High Resolution Diffractometer Chopper Spectrometer Commission 2008 18 - Wide Angle 18 Wide Angle Commission 2008 Chopper Spectrometer 1B - Disordered Mat’ls 2 - Backscattering Commission 2007 Commission 2010 Spectrometer Commission 2006

Performance of FNPB beamline Wrap-around neutrons 1 F = ´ 9 ⋅ 4 10 @ 1.4 MW Measured (@1 MW) neutron capture flux at FNPB beam exit: c 2 cm s

Neutron beta decay    n e - p + n  e

Beta Decay in the Standard Model  e - Fermi’s golden rule:  I I  2 2    decay probability f H i ≠ 60 Co  i f weak   Parity Violation found by Wu et al, 1956 60 Co e - G G V V          5 5 H F ud p 1 γ γ γ n e γ γ γ ν h.c. weak μ μ 5 e 2 1. Quark mixing 1 Quark mixing 2. 2 Nucleon structure Nucleon structure 3. 3 Helicity Helicity effects … of elementary ν μ - μ fermions: – p / E , g V = G F · V ud ·1 2 2  V V 95% 95% ud … of elementary anti- g A = G F · V ud · λ d u fermions: + p / E   No nuclear structure effects s c c e e e - (for neutrons)  p b t e

Observables in Neutron Beta Decay    Jackson et al., PR 106, 517 (1957):  e n e - Observables in Neutron beta decay, as a function of p p generally possible coupling constants (assuming only generally possible coupling constants (assuming only n Lorentz-Invariance)    e            dw 2      p p p p b m   2 2          2 G G F V V 1 3 1 3 2 2 E E            d dw E E 1 3 1 3 1 1 a e e b e e   u d e dE  e E E E  e  e e Fierz interference term b  0          p p p p p p p p          e e e e + + A A B B D D       n E E E E       e e 2       R Re Beta-Asymmetry   A 2 2   1 3 2   1  Neutrino-Electron-Correlation a 2 2    1 3    2   2    1  2 2    G V 1 3 E Neutron lifetime n F u d e 

The Standard Model Parameters V ud and λ Fermi-Decay:   1 p e - ν e e - ν e  A = 0   S = 0, m S = 0 2   g V = G F · V ud n   1 e - ν e p e - ν e A = 0    S = 1, m S = 0 2   Gamow-Teller-Decay: y g A = G F · V ud · λ ν e e - p A = -1 S = 1, m S = 1 , S   p      e dw 1 A cos p ,   (after D. Dubbers, Prog. Part. Nucl. Phys. 26, 173 (1991) e n E   e Two unknown parameters, g A and g V , need to be determined in 2 experiments       1 2 2   g 3 g 885 s 1. Neutron-Lifetime: n V A n    g 2       A A 2 0.1 2. Beta-Asymmetry:   g 2 1 3 V

Neutron Lifetime Measurements Decrease of Neutron Counts N with storage time t : N ( t ) = N (0)exp{-t/ τ eff } 1/ τ eff = 1/ τ β +1/ τ wall losses 895 Spivak 88 Byrne 96 890 Nesvizh.92 Nico 05 me [s] Arzumanov PDG2010 PDG2010 Neutron lifetim 00 Mampe 89 885 Serebrov 08 Pichlmaier 10 880 Mampe 93 Serebrov 05 Serebrov 10 875 1988 1992 1996 2000 2004 2008 2012 Experiment publication Many new attempts mostly with UCN in magnetic bottles: Ezhov et al (ILL PNPI Gatchina) Many new attempts, mostly with UCN in magnetic bottles: Ezhov et al. (ILL, PNPI Gatchina), Arzumanov et al. (Kurchatov Inst., ILL), Liu et al. (Indiana), Paul et al. (TUM), Huffman et al. (NIST, NCSU), Nico et al. (NIST), Zimmer et al., (ILL) are (at least) under construction.

The Beta Asymmetry e - p + -1.255 n   e Yerozolimski -1.26 Liaud Electron Detector (Plastic Scintillator) ( ) -1.265 1 265 PDG2010 PDG2010 PERKEO I λ Mostovoi -1.27 Decay Electrons Decay Electrons UCNA -1.275 PERKEO II PERKEO II, prelim Polarized Neutrons -1.28 1985 1990 1995 2000 2005 2010 Publication year Ongoing funded experiments: Ongoing funded experiments: UCNA (NCSU, LANL), PERKEO III Split Pair Magnet PERKEO II Magnetic Field (Heidelberg), PERC (Europe)

Use of coupling constants in Primordial Nucleosynthesis Before Phase Transition: p p p e - ν e e - W ± W ± W ± Equilibrium n n ν e n e + ν e n + e + ↔ p + ν e n + ν e ↔ p + e - n ↔ p + e - + ν e After Phase Transition (some minutes After Phase Transition (some minutes after Big Bang): n + p → d + γ d + d → 3 He + n → t + p ….. d + 3 He → 4 He + p d + He → He + p Then the Primordial Nucleosynthesis stops, as there are no stable nuclei with A = 5, 8, and as the free neutrons die out. h f di Stronger coupling constants in n ↔ p reactions ⇒ Phase transition later ⇒ nucleon density lower after phase transition ⇒ less 4 He, more d

Search for Standard Model Parameters 0.980 Kaons +Unitarity [PDG 2010] 0.975 ft(0 + → 0 + ) [Hardy09] ft(0 + → 0 + ) [Liang09 – DD-ME2] PIBETA [Pocanic04] ft(0 + → 0 + ) [Liang09 – PKO1] V ud 0.970 PDG 2010] 010] 0.965 A [UCNA 20 λ [P 0 960 0.960 -1.290 -1.280 -1.270 -1.260 λ = g A / g V A [PERKEO II, prel.]

Unitarity and superallowed nuclear decays V. Telegdi, 1977: V Telegdi 1977: I would like to say that the theory of β -decay is the theory of the decay of the neutron. I have always thought that nuclear β -decay experiments were only done faute de mieux : … If you do not know how to do the one experiment, you take the average of twenty. 2 2 2 µ = Ft g G V V F ud 1 2 µ V ( ( ) ) ud 2 +D +D V 2 2 G G 1 1 Ft Ft F R 2 2 2 = - - V V 1 1 V V V V ud u s ub (Dubbers average) Dubbers, Schmidt, RMP (2011), in press Liang et al., PRC 79, 064316 (2009)

Possible Tests of the Standard Model Multiple determinations (nuclear physics, other correlation coefficients) overconstrain problem, enable: 1. Search for Right-handed Currents (leptons are righthanded): W R ? 1 S h f Ri ht h d d C t (l t i hth d d) W ? 2. Search for Scalar and Tensor interactions (neutrinos have opposite handedness to electrons – 4 new coupling constants possible): Leptoquarks? Charged Higgs Bosons? Supersymmetry? 3. Test of the Unitarity of the Cabbibo-Kobayashi-Maskawa-Matrix: Extra Z bosons? Supersymmetry? 4 th quark generation?       d' V V V d ud u s ub             2 2  V V 95% 95%   s' V V V s ud       d u cd cs cb       2 b' V V V b  V 5%       us td td tb s c c 2 2 2 2  + + = + V V V 1 ? V 0.000015 ub u d us ub b t

Determination of the Coupling Constants Fermi-Decay:   1 p e - ν e e - ν e  a = 1   2   g V = G F · V ud n   1 e - ν e p e - ν e a = 1    2   Gamow-Teller-Decay: y g A = G F · V ud · λ ν e e - p a = -1  v      dw 1 a cos p , p    e  c  e Two unknown parameters, g A and g V , need to be determined in 2 experiments       1 2 2   g 3 g 885 s 1. Neutron-Lifetime: n V A n   2 1 g     a ~ 0.1 A 2b. Neutrino-Electron-Correlation a :   2 1 3 g V

Idea of the cos θ e ν spectrometer Nab @ SNS e - e Kinematics: p  • Energy Conservation:    E E E  e n e,max e     p p • Momentum Conservation • Momentum Conservation     dw 1 a E e cos   e  e     2 2 2 p p p 2 p p cos      p e e e e Proton phase space (Dalitz plot) Proton phase space (Dalitz plot) Probability (arb. units) Probability (arb. units) 1.5 1 5 E e = 1.25 700 keV cos θ e ν = 1 236 keV 1 1 [MeV 2 /c 2 ] Edges:     2   2 0.75 p p p 75 keV  p e min, max Slope: Slope: 2 [ cos θ e ν = 0 0.5   p p p      2 1 a e cos p cos θ e ν = -1    e p 450 keV E   e 0.25 0 0 0.2 0.4 0.6 0.8 Alternative approaches: a SPECT (Mainz, ILL), aCORN (Tulane, NIST) E e [MeV]