CKM Unitarity and Neutron Beta Decay Measuring V ud in Neutron Beta - - PowerPoint PPT Presentation

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CKM Unitarity and Neutron Beta Decay Measuring V ud in Neutron Beta - - PowerPoint PPT Presentation

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CKM Unitarity and Neutron Beta Decay Measuring V ud in Neutron Beta Decay Bastian Mrkisch Physik-Department Technische Universitt Mnchen CKM Matrix Element V ud Effective CC Couplings Neutron Lifetime Neutron Decay Corellations Neutron

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SLIDE 1

CKM Unitarity and Neutron Beta Decay

Measuring Vud in Neutron Beta Decay

Bastian Märkisch Physik-Department Technische Universität München CKM Matrix Element Vud Effective CC Couplings Neutron Lifetime Neutron Decay Corellations

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SLIDE 2

Low energy Long lifetime τ = 880.3(1.1) s Only small, precisely known radiative corrections

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Neutron Beta-Decay

Two free parameters within SM (GF from muon decay) Ratio of coupling constants Quark mixing Axial-vector gA und vector gV Cabibbo-Kobayashi-Maskawa matrix element

V A

g g  

ud

V

7 3 4 5

2 2 2 2 1

) 3 1 (

 

 

c m f ud F

e R

V G  

Ee,max = 782 keV Ep,max = 752 eV

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SLIDE 3

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Vud from Neutron Decay

from D. Pocanic arXiv:1704.00192v1

Marciano , Sirlin PRL 96 (2006)

|Vud| = 0.97585 (18)RC(55)τ(146)λ |Vud| = 0.97xxx (18)RC(11)τ(8)λ |Vud| = 0.97xxx (18)RC(2×22)τ(2×40)λ

(new avg lifetime & upcoming PERKEO III result)

Status today: (using PDG 2016 averages) Near future (this year‘s results): aCorn, aSpect?, UCNA, PERKEO III Future prospects: New experiments: Nab, PERC Penelope / HOPE / τSpect / UCNτ / BL3 For comparision: average of 14 nuclei (0+ → 0+): |Vud| = 0.97417 (18)RC(9)NS(6)exp

J.C. Hardy & I. S. Towner, PRC91, 025501 (2015)

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SLIDE 4

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Neutron Classification

Cold neutrons

moderated in thermal bath (e.g. liquid D2) E ~ 3 meV, T ~ 40 K, v ~ 800 m/s, ~ 0.5nm high flux densities: 2·1010 s-1 cm-2 density ~105 cm-³ decay rate of up to 10 6 s-1 per metre (typ. correlation measurements)

Ultracold neutrons (UCN)

E < 300 neV, T ~ 1 mK, v < 7 m/s,  > 60nm reflect from surfaces under any incident angle : storable moderate densities: ~30 cm-3 (typ. neutron lifetime, EDM)

Fermi potential ~ 100 neV Gravity ΔE=mn g Δh ~ 100 neV / m Magnetic field ΔE= μn B ~ 60 neV / Tesla

Vn

Vn < Vcrit Vn > Vcrit

UCN

UCN „bottle“ Material storage and gravity!

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SLIDE 5

Storage experiments with UCN “counting the survivors”

 0 (extrapolation)

) t ( N ) t ( N ln t

  • t

1 τ 1

2 1 1 2

 

m

... τ 1 τ 1 τ 1 τ 1 τ 1

vacuum leak wall β

    

m

 0 (experiment)

eff wall

v μ τ 1  

β

τ 1 τ 1 

m

N(t1), N(t2)

relative measurements absolute measurements

n

τ v n β

τ dt d

 

  

l

e N N n

nβ

“counting the dead”

e,p N0 l

In-beam experiments with cold neutrons

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Measurement of the neutron lifetime τn

UCN

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SLIDE 6

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Gravitrap at ILL

Previous most precise measurement

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SLIDE 7

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Neutron Lifetime Measurements

877.7(7)stat(3)sys 878.5(7)stat(3)sys 887.7(12)stat(19)sys 880.5(7)stat(8)sys New avg? 879.4(8) S=1.9 S=1.9

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SLIDE 8

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.

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SLIDE 9

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

UCN Magneto-gravitational trap

~5500 permanent magnets Operated at LANL Material: C.-Y. Liu EXA2017

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SLIDE 10
  • R. W. Pattie, et al.,

arXiv 1707.01817: 877.7(7)stat(3)sys

UCN Magneto-gravitational trap

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Hallbach array Material: C.-Y. Liu EXA2017

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SLIDE 11

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

More Neutron Lifetime Exp.

TRIGA Mark II

permanent magnet multipole + SC magnet, 8l volume, new UCN source short term goal 2s, long term < 0.3s running at Mainz

HOPE

permanent magnet octupole + SC magnet, 2l volume, new UCN source Goal: 1s -- running at ILL, Grenoble J-PARC TPC Pulsed beam Status: 1% Goal 0.1% NIST BL2: goal 1s BL3: new magnet; goal < 0.3s

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SLIDE 12

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PENeLOPE (TUM)

PENeLOPE aims at a precision of ± 0.1 s Measure protons and neutrons directly from

  • decay. Also fill-and-empty.

proton detector absorber movement mechanism

  • uter pressure

vessel helium vessel storage walls (electropolished) 2.5 m

Magnetic & Gravitational trapping avoids material losses altogether! (HOPE/ILL, Ezhov/ILL, τSpect/Mainz, UCNτ/LANL, PENeLOPE/TUM): store only one spin-direction

PENeLOPE light

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SLIDE 13

Neutron Decay Correlations

Electron pe σe Proton pp Neutrino pν Neutron Spin J

A B

C

Naviliat-Cuncic and Gonzalez-Alonso, Ann. Phys. 525, 8–9, 600–619 (2013) Dubbers and Schmidt, Rev. Mod. Phys (2012)

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SLIDE 14

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Correlation Coefficients

 

 

 

3 2 2 2 2 F ud e e e 5 e e

d 1 1 3 d d d 2 2 p E E E E G V

       

n e e e e n e e e e

1 p p p p p p E E E E E E a A B D m E b

     

                        

Jackson, Treiman, Wyld,

  • Nucl. Phys. 4, 1957

1.2(2.0) 10-4

Typical current relative precision O(10-2 - 10-3) Goal of next generation PERC: O(10-3 - 10-4) for some observables

Electron pe σe Proton pp Neutrino pν Neutron Spin J

A B

C

 PERKEO II PERKEO III / PERC

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SLIDE 15

Determination of  = gA/gV

 = gA/gV

relative change

.0010

  • 0.1184

APDG   .0030 0.9807 BPDG  

.004 0.103 a PDG   

.0026 0.2377 C   

1.1% 0.3% 1.1% 3.9%

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SLIDE 16

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Current Neutron Decay Experiments

PERKEO III A, B, C, b Heidelberg, TU Wien, TU München, ILL aCORN a NIST UCNA / UCNB A, B, b Los Alamos aSpect a Mainz, TU Wien, ILL Nab a, b SNS … and PERC

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SLIDE 17

Experimental asymmetry, polarisation P

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PERKEO: Measuring Beta Asymmetry A

  cos 1 ) , ( A c v E W  

Electron angular distribution: Magnetic field to as quantisation axis

V A

g g  

Within Standard Model: Integration over hemispheres: 2 × 2π detection

Polarised Neutrons Electron

Detector 1 Detector 2

2 1 cos  

A P N N N N A

c v 2 1 exp

   

   

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SLIDE 18

Detector 1 Detector 2 Beamstop electrons Active volume (~2m) B = 150 mT (homogeneous ) B = 90 mT Total length: 8 m ~50.000 decays / sec in the continuous beam

Beam preparation

Mechanical disc chopper Adiabatic Fast Passage Spin Flipper Supermirror Polarizer Velocity Selector

Pulsed Neutron Beam

Duty cycle: ~7%

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Spectrometer PERKEO III

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SLIDE 19

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

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SLIDE 20

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PERKEO III: Calibration Fits

114 full calibrations in (twice per day) Simultaneous Fit: Χ²/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

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SLIDE 21

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Asymmetry Extraction

3

10 9 . 1

   A A

4

10 8 . 4

    

Result (still blinded):

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SLIDE 22

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PERKEO III Error budget

Finally, close to being unblinded (inconsistencies in indep. analyses resolved)

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SLIDE 23

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PDG 2016

  • 1.2723(23)

Electron-Neutroino Correlation „a“: Results soon from aSpect, Mainz Nab goal: competitive with „A“ New UCNA result

New: aCorn, NIST

Goal of Nab, PERC Δλ/λ ~ O(10-4)

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SLIDE 24

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Proton Electron Radiation Channel (PERC)

Cryostat

Active volume in a 8 m long neutron-guide, B0 = 1.5 T: phase space density and statistics Magnetic Filter, B1 = 6T: phase space, systematics (solid angle, backscatter suppression) Source for specialised spectrometers Aims to improve results by an order of magnitude: 10-4. New Observables.

12 2

1

  B B

  • Nucl. Instr. Meth. A 596 (2008) 238 and

arXiv:0709.4440

B0 B1 B2

Magnetic Filter B1

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SLIDE 25

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Beam Site Mephisto, FRM II

FRM-II, Garching

“Empty” new hall Neutron guide: length 40 m, R = 3000 m, m = 2.5 Expected intensity equal to PF1B at ILL (2×1010 s-1cm-2) Only very few neighbours: low ambient background Easy ground level access, Fixed installation Status: All major components of the beam line ready or in production New hall east Reactor „Atomic egg“ Guide hall Reactor Core PERC Intermediate Structure New hall east

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SLIDE 26

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PERC: Neutron Spin Control

O(10-4) precision requires neutron spin control on the same level:

  • polarisation 99.7%: FeSi polarisers – Soldner / Petoukhov et al. (ILL)
  • spin flipper: AFP 100.00%
  • guide in strong magnetic field: only 10-4 depolarization per bounce allowed
  • measurement with 3He spin filters – Soldner et al. (ILL)

Non-magnetic CuTi mirror m=2 preserves spin direction Production quality

(except for the too thin top layer)

Large maximum angle of reflection, high reflectivity Reduces neutron losses in PERC by factor > 2: background! (Mildly) backable (>80°C). Beneficial for vacuum conditions. Hollering (TUM), Rebrova / Schmidt (HD)

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SLIDE 27

27 SPP 1491 Closing Convention - B. Märkisch

Status of the PERC Magnet

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SLIDE 28

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

PERC is a Facility

MAC-E filter (“aSPECT”)

Magnetic spectrometer Electrostatic chopper & p detector R×B spectrometer Electron

  • r proton

detector Wien filter for protons User System Clean source of electrons and protons from neutron decay Scintillator, Silicon, …

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SLIDE 29

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Prospects

Tremendous ongoing efforts to improve Vud from neutron decay Lifetime τ Potential new average (including UCNtau + Gravitrap2 results) τ = 879.4(8) s; S = 1.9 Many new experimental results to be expected: UCNtau, HOPE, tauSpect, PENeLOPE, Gravitrap2 Current Goal: O(0.1s) Ratio of coupling constants λ New (upcoming) results by aCorn, UCNA, PERKEO III, aSpect Next generation Nab a 0.1% PERC A 0.05% Long-term future (next decade): cold beam line ANNI at ESS (more than order of magnitude More statistics in pulsed beam) Aerial view ESS construction site September 2015

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SLIDE 30

PERC (Proton Electron Radiation Channel) at FRM II / MLZ

  • W. Heil
  • U. Schmidt
  • H. Abele
  • E. Jericha
  • O. Zimmer
  • T. Soldner
  • J. Klenke
  • B. Märkisch
  • G. Konrad
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SLIDE 31

Wilhelm und Else Heraeus-Seminar „Particle Physics with Cold and Ultra-Cold Neutrons“

Scientific Organizers: Hartmut Abele, Atominstitut, TU Wien Bastian Märkisch, TU München

Physikzentrum Bad Honnef Wednesday 24th – Friday 26th October 2018

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

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SLIDE 32

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017 from D. Pocanic arXiv:1704.00192v1

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SLIDE 33

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Beam Method: NIST Experiment

  • S. Dewey
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SLIDE 34

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Measurement cycle measures UCN spectral dependence Small final extrapolation 878.5(7)stat(3)sys Result:

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SLIDE 35

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Observables and Statistics

Unpolarised neutrons Correlation a

∆a ~ 5 ∙ 10-3

from proton spectrum Fierz coefficient b

∆b ~ 1 ∙ 10-3

from electron spectrum or β-asymmetry Electron helicity h

Time for 109 events

  • 5 hours (unpolarised)
  • 1 day polarised 98%
  • 2 days polarised 99.7%
  • ×25 for pulsed mode

Polarised neutrons

  • β-asymmetry A

∆A ~ 5 ∙ 10-4

  • Proton asymmetry C

∆C ~ 3 ∙ 10-4 Neutrino asymmetry B ∆B ~ 1 ∙ 10-3

  • Weak magnetism fWM

> 3 σ from β-asymmetry or polarised spectra

Electron Proton Neutrino Neutron Spin

A B C

a

Focus on non-coincident measurements due to high count rates:

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SLIDE 36

Sensitive to scalar and tensor couplings within SM: b = 0 Enters decay rate / spectra and asymmetries:

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017

Fierz Interference Term b

Requirement: Calibration etc. independent of neutron data Reach of existing PERKEO III data Δb ≈ 3×10-2 from asymmetry. Pending approval by the collaboration.

Only 1 out of 4 datasets.

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SLIDE 37

Extra

Bastian Märkisch (TUM) | BEYOND 2018 | 29.11.2017