CKM Unitarity and Neutron Beta Decay Measuring V ud in Neutron Beta Decay Bastian Märkisch Physik-Department Technische Universität München CKM Matrix Element V ud Effective CC Couplings Neutron Lifetime Neutron Decay Corellations
Neutron Beta-Decay Low energy E p,max = 752 eV E e,max = 782 keV Long lifetime τ = 880.3(1.1) s 2 R 5 4 1 2 2 f m c G V ( 1 3 ) e F ud 3 7 2 Only small, precisely known radiative corrections Two free parameters within SM ( G F from muon decay) Ratio of coupling constants Quark mixing Axial-vector g A und vector g V Cabibbo-Kobayashi-Maskawa matrix element g A V ud g V Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
V ud from Neutron Decay Marciano , Sirlin PRL 96 (2006) from D. Pocanic arXiv:1704.00192v1 Near future (this year‘s results): Status today: aCorn, aSpect?, UCNA, PERKEO III (using PDG 2016 averages) | V ud | = 0.97xxx (18) RC (2 × 22) τ (2 × 40) λ | V ud | = 0.97585 (18) RC (55) τ (146) λ (new avg lifetime & upcoming PERKEO III result) Future prospects: For comparision: New experiments: Nab, PERC average of 14 nuclei ( 0 + → 0 + ): Penelope / HOPE / τ Spect / UCN τ / BL3 | V ud | = 0.97417 (18) RC (9) NS (6) exp | V ud | = 0.97xxx (18) RC (11) τ (8) λ J.C. Hardy & I. S. Towner, PRC91, 025501 (2015) Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Neutron Classification V n < V crit Cold neutrons moderated in thermal bath (e.g. liquid D 2 ) V n E ~ 3 meV, T ~ 40 K, v ~ 800 m/s, ~ 0.5nm high flux densities: 2·10 10 s -1 cm -2 density ~10 5 cm - ³ V n > V crit decay rate of up to 10 6 s -1 per metre Fermi potential ~ 100 neV (typ. correlation measurements) Gravity ~ 100 neV / m ΔE= m n g Δh Ultracold neutrons (UCN) Magnetic field ~ 60 neV / Tesla E < 300 neV, T ~ 1 mK, v < 7 m/s, > 60nm ΔE= μ n B reflect from surfaces under any incident angle : storable moderate densities: ~30 cm -3 (typ. neutron lifetime, EDM) UCN UCN „ bottle “ Material storage and gravity! Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Measurement of the neutron lifetime τ n Storage experiments with UCN In-beam experiments with cold neutrons “counting the survivors” “counting the dead” 1 1 N ( t ) 1 ln n β τ t - t N ( t ) e,p m 2 1 2 l 1 1 1 1 1 ... τ τ τ τ τ β m wall leak vacuum UCN 0 (experiment) N(t 1 ), N(t 2 ) 1 μ v 0 (extrapolation) eff τ wall N 0 1 1 l d N N τ v 0 n e τ τ n β τ β m dt n absolute measurements relative measurements Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Gravitrap at ILL Previous most precise measurement Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Neutron Lifetime Measurements 887.7(12) stat (19) sys 877.7(7) stat (3) sys 878.5(7) stat (3) sys 880.5(7) stat (8) sys New avg? S=1.9 879.4(8) S=1.9 Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
New Gravitrap II Lifetime measurement by fill-and-empty. Massively larger than previous experiment. Running at ILL, Grenoble. Many systematic studies (coating, losses, temperature) Next: Change from LN temperature to LHe cooling (10K) to reduce wall losses. Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
UCN Magneto-gravitational trap Operated at LANL ~5500 permanent magnets Material: C.-Y. Liu EXA2017 Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
UCN Magneto-gravitational trap R. W. Pattie, et al., Hallbach arXiv 1707.01817: array 877.7(7) stat (3) sys Material: C.-Y. Liu EXA2017 Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
More Neutron Lifetime Exp. TRIGA Mark II HOPE permanent magnet multipole + SC magnet, permanent magnet octupole + SC magnet, 8l volume, new UCN source 2l volume, new UCN source short term goal 2s, long term < 0.3s Goal: 1s -- running at ILL , Grenoble running at Mainz NIST BL2: goal 1s J-PARC TPC BL3: new magnet; goal < 0.3s Pulsed beam Status: 1% Goal 0.1% Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
PENeLOPE (TUM) Magnetic & Gravitational trapping avoids material losses altogether! (HOPE/ILL, Ezhov/ILL, τSpect /Mainz, UCNτ /LANL, PENeLOPE/TUM): store only one spin-direction PENeLOPE aims at a precision of ± 0.1 s Measure protons and neutrons directly from absorber decay. Also fill-and-empty. movement mechanism proton detector 2.5 m outer pressure vessel helium vessel storage walls (electropolished) PENeLOPE light Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Neutron Decay Correlations A Neutron Spin J Electron p e σ e B Neutrino p ν C Proton p p Naviliat-Cuncic and Gonzalez-Alonso, Ann. Phys. 525, 8 – 9, 600 – 619 (2013) Dubbers and Schmidt, Rev. Mod. Phys (2012)
Correlation Coefficients A Neutron Spin J 3 d 1 Jackson, Treiman, Wyld, 2 2 2 2 G V 1 3 p E E E Nucl. Phys. 4, 1957 Electron p e σ e F ud e e 0 e B 5 d E d d 2 2 e e p p m p p p p Neutrino p ν n e e e e 1 a b A B D C E E E E E E E e e n e e Proton p p PERKEO II PERKEO III / PERC Typical current relative precision O(10 -2 - 10 -3 ) Goal of next generation PERC: 1.2(2.0) 10 -4 O(10 -3 - 10 -4 ) for some observables Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Determination of = g A / g V relative change = g A / g V 1.1% A PDG -0.1184 0 .0010 0.3% B PDG 0.9807 0 .0030 1.1% C 0.2377 0 .0026 3.9% a PDG 0.103 0 .004
Current Neutron Decay Experiments PERKEO III A, B, C, b a Spect Heidelberg, a TU Wien, Mainz, TU München, TU Wien, ILL ILL aCORN a NIST UCNA / UCNB Nab A, B, b a, b Los Alamos SNS … and PERC Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
PERKEO: Measuring Beta Asymmetry A Electron angular distribution: v Detector 1 W ( , E ) 1 A cos c Within Standard Model: g A g Electron V Magnetic field to as quantisation axis Polarised Neutrons Integration over hemispheres: 1 cos 2 2 × 2π detection Experimental asymmetry, polarisation P N N A 1 v P A Detector 2 exp 2 c N N Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Spectrometer PERKEO III Detector Total length: 8 m 1 ~50.000 decays / sec in the continuous beam electrons Detector 2 Pulsed Neutron B = 90 B = 150 mT Beam mT (homogeneous ) Active volume Beam preparation (~2m) Beamstop Duty cycle: ~7% Mechanical Velocity Supermirror Adiabatic Fast disc chopper Selector Polarizer Passage Spin Flipper Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
PERKEO III: Pulsed Neutron Beam Sacrifise ~2 orders of magnitude in statistics to address important systematic: background; continuous beam 50.000 s -1 ; pulsed 250 s -1 Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
PERKEO III: Calibration Fits 114 full calibrations in (twice per day) Simultaneous Fit: Χ ²/NDF = 1.0 – 1.3 Free parameters: Non-linearity, gain, PE + norms In addition: Hourly drift measurements ~weekly 2D uniformity scan Green bars indicate fit region Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Asymmetry Extraction Result (still blinded): A 3 1 . 9 10 A 4 4 . 8 10 Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
PERKEO III Error budget Finally, close to being unblinded (inconsistencies in indep. analyses resolved) Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Electron-Neutroino Correlation „a“: Results soon from New: aCorn, NIST aSpect, Mainz Nab goal: competitive with „A“ New UCNA result Goal of Nab, PERC Δλ / λ ~ O(10 -4 ) PDG 2016 -1.2723(23) Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Proton Electron Radiation Channel (PERC) Magnetic Filter B 1 B 1 B 2 Cryostat B 0 Active volume in a 8 m long neutron-guide, B 0 = 1.5 T: phase space density and statistics B Magnetic Filter , B 1 = 6T: phase space, systematics 1 2 12 B 0 (solid angle, backscatter suppression) Source for specialised spectrometers Aims to improve results by an order of magnitude: 10 -4 . New Observables. Nucl. Instr. Meth. A 596 (2008) 238 and arXiv:0709.4440 Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
Beam Site Mephisto, FRM II PERC FRM-II, Garching Reactor New hall east „ Atomic egg“ Guide hall New hall east “Empty” new hall Neutron guide: length 40 m, R = 3000 m, m = 2.5 Expected intensity equal to PF1B at ILL (2 × 10 10 s -1 cm -2 ) Only very few neighbours: low ambient background Intermediate Easy ground level access, Fixed installation Structure Status: All major components of the beam line ready or in production Reactor Core Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017
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