Fierz Interference in Neutron Decay Leah Broussard Oak Ridge - - PowerPoint PPT Presentation

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Fierz Interference in Neutron Decay Leah Broussard Oak Ridge National Laboratory Beta Decay as a Probe of New Physics November 1-3, 2018 University of Massachusetts Amherst A probe for new physics CKM unitarity Competitive with LHC

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SLIDE 1

Fierz Interference in Neutron Decay

Leah Broussard

Oak Ridge National Laboratory

Beta Decay as a Probe of New Physics November 1-3, 2018 University of Massachusetts Amherst

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SLIDE 2

A probe for new physics

  • CKM unitarity
  • Competitive with LHC limits1
  • LQCD calc gA now 1%2
  • New Δ𝑆

π‘Š calc shifts from unitarity3

  • Beyond Standard Model
  • Scalar, Tensor, Right-handed currents
  • Improved LQCD calcs of gA, gS, gT

4

𝑒′ 𝑑′ 𝑐′ = 𝑾𝒗𝒆 π‘Š

𝑣𝑑

π‘Š

𝑣𝑐

π‘Š

𝑑𝑒

π‘Š

𝑑𝑑

π‘Š

𝑑𝑐

π‘Š

𝑒𝑒

π‘Š

𝑒𝑑

π‘Š

𝑒𝑐

𝑒 𝑑 𝑐

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 2

1Gonzalez-Alonso, Naviliat-Cuncic, and Severijns, arXiv:1803.08732 2Chang et al, Nature 558 (2018) 91-94 3Seng, Gorchtein, Patel, Ramsey-Musolf, arXiv:1807.10197 4Gupta et al, PRD 98 (2018) 034503

|𝑾𝒗𝒆|2 + |π‘Š

𝑣𝑑|2 + |π‘Š 𝑣𝑐|2 = 0.9994(5) (PDG 18)

0.9984(4)

10-5

Hardy and Towner, CIPANP2018

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SLIDE 3

Neutron Ξ²-decay observables

dW ∝ 1 + 𝒃 Τ¦ π‘žπ‘“ βˆ™ Τ¦ π‘žπœ‘ πΉπ‘“πΉπœ‘ + 𝒄 𝑛𝑓 𝐹𝑓 + Τ¦ πœπ‘œ βˆ™ 𝑩 Τ¦ π‘žπ‘“ 𝐹𝑓 + π‘ͺ Τ¦ π‘žπœ‰ πΉπœ‰ + 𝑬 Τ¦ π‘žπ‘“ Γ— Τ¦ π‘žπœ‘ πΉπ‘“πΉπœ‘

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 3

𝑩 = βˆ’2

𝝁2+𝝁 1+3𝝁2

𝒃 =

1βˆ’π2 1+3𝝁2

𝝁 =

𝒉𝑩 𝒉𝑾

Asymmetries: 𝜷meas(𝐹𝑓) =

𝜷(𝐹𝑓) 1+𝒄𝑛𝑓/𝐹𝑓

CKM unitarity: πŠβˆ’1 = 𝑋 ∝ 𝑾𝒗𝒆 2 1 + 3 𝝁 2 Goal: dA/A or da/a β†’ 0.1% and dΟ„ β†’ 0.1 s B (bΞ½), b linear sensitivity to BSM S,T: 𝒄π‘ͺ𝑻𝑡 =

2 1+3𝝁2 𝒉𝑻𝝑𝑻 βˆ’ 12𝝁𝒉𝑼𝝑𝑼

𝒄𝝃

π‘ͺ𝑻𝑡 =

2 1 + 3𝝁2 𝝁𝒉𝑻𝝑𝑻 βˆ’ 4𝒉𝑼𝝑𝑼 1 + 2𝝁 Not yet measured in neutron decay, until…

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SLIDE 4

UCNA collaboration

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 4

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SLIDE 5

UCNA experiment

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 5

2010: 700 nm Mylar 2011-12: 500 nm Mylar 2012-13: 130/180 nm 6F6F

1Brown et al, PRC 97 035505 (2018)

More from Andy Saunders, next

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SLIDE 6

Fierz term from UCNA

  • UCNA: 4Ο€ Ξ² acceptance,

low neutron/ambient backgrounds, energy reconstruction β†’ direct spectral extraction of bn

  • β€œSuper-sum” removes

distortion from A

Ξ£ = 1 2 𝑂(𝐹)1

+𝑂(𝐹)2 βˆ’ + 1

2 𝑂(𝐹)1

βˆ’π‘‚(𝐹)2 +

  • 2010 data set dominant

error: energy calibration

𝒄𝒐 = 0.067 Β± 0.005𝑑𝑒𝑏𝑒 βˆ’0.061

+0.90 𝑑𝑧𝑑

–0.041 <𝒄𝒐< 0.225 (90% CL)

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 6

1Hickerson et al, PRC 96 (2017) 042501

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SLIDE 7

Complementary approaches for b

  • 2 new datasets: 2011-12, 2012-13
  • 2012 improved E reconstruction: b vs octet β†’
  • 2 techniques: spectrum 𝜯 vs asymmetry

𝑩 1+𝒄m

E

  • 𝜯 limited by E calibration, 𝑩𝒏 by statistics
  • Preliminary: 𝒄𝒐 = 𝑦. 𝑦𝑦 Β± 0.03 (blinded)

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 7

blinded

Thanks X. Sun (Caltech) for slide content

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SLIDE 8

Fundamental Neutron Physics at the Spallation Neutron Source

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 8

FNPB program:

𝒐𝒒 β†’ π’†πœΉ

n3He Nab nEDM

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SLIDE 9

Nab Collaboration

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 9

  • R. Alarcona, S. Baesslerb,c (Project Manager), S. Balascutaa, L. BarrΓ³n Palosn, T. Baileym, K. Bassi, N. Birgei, A.

Blosef, D. Borissenkob, J.D. Bowmanc (Co-Spokesperson), L. J. Broussardc, A.T. Bryantb, J. Byrned, J.R. Calarcoc,i, J. Caylori, K. Changb, T. Chuppo, T.V. Ciancioloc, C. Crawfordf, X. Dingb, W. Fanb, W. Farrarb, J. Farr,

  • N. Fomini, E. FrleΕΎb, J. Fryb, M.T. Gerickeg, M. Gervaisf, F. GlΓΌckh, G.L. Greenec,i, R.K. Grzywaczi, V. Gudkovj,
  • J. Hamblene, C. Hayesm , C. Hendruso, T. Itok, A. Jezghanif, H. Lib, M. Makelak, N. Macseyg, R. Mammeig, J.

Martinl, M. Martineza, D.G. Matthewsf, M. McCreaf, P. McGaugheyk, C.D. McLaughlinb, P. Muellerc, D. Perrymani, D. van Pettenb, S.I. PenttilΓ€c (On-site Manager), D. PočaniΔ‡c (Co-Spokesperson), Y. Qianb, G. Randalla, G. Rileyi, C.A. Roysem, K.P. Rykaczewskic, A. Salas-Baccib, S. Samieib, E.M. Scotti, T. Sheltonj, S.K. Sjuek, A. Smithb, E. Smithk, E. Stevensb, J. Wexlerm, R. Whiteheadi, W.S. Wilburnk, A.Youngm, B.Zeckm

Main project funding:

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SLIDE 10

Nab measurement principles

  • Goal: Ξ”a/a~10-3 and Ξ”b~3Γ—10-3
  • 4Ο€ Ξ² acceptance : β€œtear-drop”
  • π‘žπ‘ž

2= π‘žπ‘“ 2 + 2π‘žπ‘“π‘žπœ‘ cos πœ„π‘“πœ‰ + π‘žπœ‰ 2

Bowman, J Res NIST 110 40 (2005) Pocanic et al, NIMA 611 211 (2009) Baessler et al, J Phys G 41 114003 (2014) Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 10

Yield: ∝ 1 + 𝒃

π‘žπ‘“ 𝐹𝑓 cos πœ„π‘“πœ‰

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SLIDE 11

Nab measurement principles

  • Asymmetric spectrometer with long

TOF arm: proton TOF β‡’ momentum

π‘’π‘ž = 𝑀 π‘›π‘ž π‘žπ‘ž = 𝑔 cos πœ„ π‘žπ‘ž

  • Adiabatic field expansion

π‘’π‘ž = π‘›π‘ž π‘žπ‘ž ΰΆ±

𝑨0 𝑀

𝑒𝑨 1 βˆ’ 𝐢 𝑨 𝐢0 sin2 πœ„ + π‘Ÿ π‘Š 𝑨 βˆ’ π‘Š 𝐹0

  • Expand for

small angles

  • For each Ee

fit central 75% to obtain a

  • Edges verify

spectrometer response

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 11

7 m

  • W. Fan, UVA
  • J. Phys: Conf Ser. 876 012005 (2017)
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SLIDE 12

Nab spectrometer installation

Installation crew nominated for ORNL β€œSignificant Event Award”

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 12

gif credit: J. Fry, UVA

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SLIDE 13

Expected statistical uncertainty

  • 1.4 MW routine at SNS
  • Expect 1600 decays/s =

200 p/s in top detector

  • Up to Ξ”a/a~2Γ—10-3 each

run-cycle

  • Require 2 years SNS

running for statistics goal

  • Including 50% duty

factor, 10% background, several systematic runs

Ξ”a/a~7Γ—10-4

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 13

  • D. Pocanic
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SLIDE 14

Nab expected systematics for a

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 14

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SLIDE 15

Systematics for Fierz term b

  • Full Ξ² energy collected, except:
  • Bounce history (deadlayer), bremsstrahlung, detector response…
  • Also backgrounds, edge effects, timing cutoff, proton efficiency…
  • Statistical uncertainty ~3 Γ— 10βˆ’4
  • if gain free parameter β†’ 5 Γ— 10βˆ’4
  • Initial (partial) parametric study of systematics:

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 15

Systematic Requirement Gain Free parameter Offset Β±0.06 keV

  • Max. nonlinearity

Β±0.05 keV Resolution Β±2 keV Energy tail Β±10%

  • H. Li, UVA
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SLIDE 16

Magnetic field

  • Precise (relative) field mapping

required for

βˆ†π‘€ 𝑀 ≀ 2 Γ— 10βˆ’5

  • Locate electron/proton flux tubes

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 16

  • J. Fry, UVA

Bfilter BTOF BDV 𝛿

  • S. Penttila, ORNL

(< 2%)

BTOF Bfilter (1%) BDV Bfilter (1%)

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SLIDE 17

Detector effects

  • Calibration (dE ~ 0.2 keV)
  • Linearity to ~10-4 β†’ radioactive

sources; need high precision calibrated pulser

  • Temperature stability to 0.5 K β†’

sensors, leakage current, pulser gain?

  • Detector response vs. event

energy/hit location; uniformity β†’ collimated radioactive sources; electron-gun studies

  • Cross-talk β†’ radioactive sources,

proton beam (physical); pulsers (electronic)

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 17

  • Si detector: 2 mm thick, 11

cm diameter active area, 100 nm deadlayer, 127 hex pixels

  • 40-50 ns rise times
  • 3 keV @ 30 keV FWHM
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SLIDE 18
  • E. Frlez, UVA

Detector effects

  • dE in tail (ratio ~ 4.4Γ—10-4)
  • Backscattering = sum both detectors

but…

  • Bounce history of electrons β†’

radioactive source studies to benchmark simulations

  • Detector deadlayer uniformity β†’

measure with proton and electron gun

  • Bremsstrahlung needs Γ—10

improvement β†’ characterize in situ with radioactive sources; electron-gun and gamma detector

  • Rate-dependent effects:

backgrounds, accidentals, deadtime

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 18

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SLIDE 19

Detector effects

  • Proton trigger efficiency < 100

ppm/keV (efficiency slope 50%) β†’ proton gun

  • TOF bias <0.3 ns on average

between electrons and protons (from detector response) β†’ collimated fast timing source, electron-gun

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 19

  • 300 V

0 V

Graphic by A. Jezghani, UKY

  • S. Baessler

x position [mm] y position [mm] Weighting potential

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SLIDE 20

45Ca Fierz term

  • Learn high precision calibration
  • Also nice BSM target
  • Source on thin 6F6F foil
  • UCNA spectrometer with UCNB/Nab

detectors

  • 108 events collected

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 20

UCNB Si detectors

45Ca source 207Bi, 139Ce, 113Sn

source insert Goal |b|~10-2

Energy [MeV}

  • L. Hayen, KU Leuven

1Gonzalez-Alonso and Naviliat-Cuncic, PRC 94 (2016) 035503 2Hayen et al, RMP 90 (2018) 015008

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SLIDE 21

Polarized Nab (abBA/PANDA)

Leah Broussard Beta Decay as a Probe of New Physics, November 1-3, 2018 21 Thanks S. Baessler for slide

Only major modification: Addition of a neutron beam polarizer Main uncertainties in previous best experiments: statistics, detector, background, polarization

  • Statistics @ SNS or NIST is sufficient

for a competitive measurement of 𝐡, but could be better

  • Superior detector energy resolution,

good enough time resolution

  • Keep coincidence detection

(electrons and protons) to improve background

  • Polarization measurement seems

manageable (Crossed supermirrors or He-3)

Cold Neutron Beam from left Multipixel Si detectors for decay electrons and protons

Goal: Ξ€ πš¬π‘© 𝑩 ≀ 10βˆ’3, Ξ€ 𝜠π‘ͺ π‘ͺ ≀ 10βˆ’3

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SLIDE 22

Summary

  • UCNA has produced first spectral determination of

–0.041 <𝒄𝒐< 0.225 (90% CL), Ξ”b~0.03 in analysis

  • Nab is now commissioning, aiming for Ξ”a/a~10-3

and Ξ”b~3Γ—10-3

  • Key systematics for a include relative magnetic field

determination and electron energy reconstruction

  • Detection systematics both challenging and an
  • pportunity for other physics targets

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 22

This research was sponsored by the LDRD program [project 8215] of ORNL, managed by UT-Battelle, LLC, and the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, contract DE-AC05-00OR2272.

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SLIDE 23

Nab uncertainty analysis

  • Simple model for parametric studies

π‘’π‘ž =

π‘›π‘ž π‘žπ‘ž Χ¬ 𝑨0 𝑀 𝑒𝑨 1βˆ’πΆ 𝑨

𝐢0 sin2 πœ„+π‘Ÿ π‘Š 𝑨 βˆ’π‘Š0 𝐹0

  • Piecewise quadratic

approximation

  • Compute analytically
  • Neglect π‘Š 𝑨 term

for speed, then apply correction factor

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 23

  • S. Baessler
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SLIDE 24

UCNA measurement principles

  • 𝑋 ∝ 1 +

𝑀 𝑑 𝑄 𝐡(𝐹) cos πœ„

  • Magnetic spectrometer: cos πœ„ = Β±

1 2

  • Measure asymmetry: 2 detectors, 2 spin directions
  • Spin-dependent and detector-dependent efficiencies?
  • Cancel systematics with Super-Ratio

𝑇 𝐹 =

𝑂 𝐹 1

+𝑂 𝐹 2 βˆ’

𝑂 𝐹 1

βˆ’π‘‚ 𝐹 2 +

𝐡𝑇𝑆 =

1βˆ’βˆšπ‘† 1+βˆšπ‘† = 𝑀 𝑑 𝑄 𝐡(𝐹) cos πœ„

Beta Decay as a Probe of New Physics, November 1-3, 2018 Leah Broussard 24