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Beta decay experiments with separated fragmented beams Oscar Naviliat-Cuncic National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy Michigan State University Scope and Outline Discuss recent measurements and

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Beta decay experiments with separated fragmented beams

Oscar Naviliat-Cuncic

National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy Michigan State University

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ACFI-FRIB Workshop, Oct. 23-25, 2014 2

Michigan State University National Science Foundation

Scope and Outline

  • Discuss recent measurements and future plans for

experiments in beta decay using separated fragmented beams.

  • 1. Spectrum shape measurement in 6He and 20F decays
  • 2. Correlation measurements with polarized beams
  • 3. Summary
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ACFI-FRIB Workshop, Oct. 23-25, 2014 3

Michigan State University National Science Foundation

Context

  • The specificity of rare isotopes beams produced by

fragmentation (NSCL/FRIB) are often considered in terms of their exoticity or their production yields.

  • We consider here separated fragmented beams to explore

their potential to eliminate some instrumental effects for the measurement of beta spectrum shapes.

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Measurement of the spectrum shape in 6He decay

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ACFI-FRIB Workshop, Oct. 23-25, 2014 5

Michigan State University National Science Foundation

Constraints on Tensor Couplings

  • During the past 20 years, experiments with

traps have had no impact in improving constraints on tensor couplings in nuclear beta decay.

  • Assuming LHn, the most precise parameter to search for contributions of

tensor couplings is the Fierz term (or the contribution of the Fierz term to

  • ther correlation coefficients).
  • At the light of LHC results, the precision requirement for new experiments

corresponds to Db < 10-3

ONC and M. Gonzalez-Alonso, Ann. Phys. (Berlin) 525 (2013) 600

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ACFI-FRIB Workshop, Oct. 23-25, 2014 6

Michigan State University National Science Foundation

Sensitivity to Fierz term in 6He decay

Db (‰)

For 108 collected events

a.u.

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ACFI-FRIB Workshop, Oct. 23-25, 2014 7

Michigan State University National Science Foundation

Weak Magnetism

  • Any attempt to reach Db < 0.01 from the measurement of the

shape of the beta spectrum, will first see the contribution of the Weak Magnetism form factor, which is signed by an additional linear term in the beta spectrum.

  • For 6He decay, the contribution of the Weak Magnetism

form factor to the linear term is estimated to produce a slope +0.66 %/MeV(1) (has never been measured).

  • A first step toward a measurement of the spectrum shape in

6He consists to tests CVC.

(1) F. Calaprice and B.R. Holstein, NPA 273 (1976) 301

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ACFI-FRIB Workshop, Oct. 23-25, 2014 8

Michigan State University National Science Foundation

General principle

Range of b particles Choose your Favorite isotope Single detector

  • Well localized (and clean) source
  • 4p solid angle and 100% detection efficiency
  • Detection of b particles without backscattering, out-scattering,
  • r energy loss in dead-layers.

How close can we get to such conditions with separated implanted ions produced by fragmentation?

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ACFI-FRIB Workshop, Oct. 23-25, 2014 9

Michigan State University National Science Foundation

NSCL Coupled Cyclotron Facility

  • Dp/p = 1%
  • Dx×Dy = 1.5×2 mm2
  • No traces of 8Li or 9Li

contamination

Production target (Be) Primary beam: 18O 150 MeV/A Wedge (Al)

Extraction: 1.2×105 6He/s

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ACFI-FRIB Workshop, Oct. 23-25, 2014 10

Michigan State University National Science Foundation

Pile-up

Beam purity and profile

Vary degrader thickness by rotation Range distribution in Al degrader Beam energy at implantation detector

(operating the detector at lower gain)

  • No traces of 8Li or 9Li.
  • Tail is due to induced reactions in the

detector

CsI-run040-segs:0

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ACFI-FRIB Workshop, Oct. 23-25, 2014 11

Michigan State University National Science Foundation

Setup

CsI(Na) or NaI(Tl) Al degrader

6He

6He

  • 46 MeV/nucleon

after degrader

  • CsI(Na) (2"×2"×5")
  • NaI(Tl) (Ø3"×3")
  • 2 small CsI(Na) and

NaI(Tl) detectors (Ø1"×1") g detectors for background identification

  • Implant 6He ions in detectors.
  • The range of 3.5 MeV electrons in CsI is

6 mm.

  • Requires 40-50 MeV/A ions
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ACFI-FRIB Workshop, Oct. 23-25, 2014 12

Michigan State University National Science Foundation

Measuring sequence

Decay spectrum Implantation

2.5 s 10-15 s (3/4 of background level due to ambient background)

Decay NaI

NaI-run182-segs:0,1-Ew:500-2500

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ACFI-FRIB Workshop, Oct. 23-25, 2014 13

Michigan State University National Science Foundation

Theoretical corrections

Za2

(Sirlin’87)

Z 2a3

(could be neglected)

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ACFI-FRIB Workshop, Oct. 23-25, 2014 14

Michigan State University National Science Foundation

MC simulations

Calculate spectrum of the energy absorbed in the detector. including the effect of escaping bremsstrahlung radiation.

  • X. Huyan

Generated Absorbed

Standard Livermore Penelope

  • G4 EM packages
  • EGSnrc

The differences in the comparison between codes/ packages/ implementations have been observed to be < 5×10-4 /MeV. Imp-0 Imp-1 CsI(Na)

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ACFI-FRIB Workshop, Oct. 23-25, 2014 15

Michigan State University National Science Foundation

Background

CsI-run145-segs:0,1,2-Ew:0500-7000

Time (s×100)

CsI-run145-segs:0,1,2-Tw:0300-0400 CsI-run145-segs:0,1,2-Tw:1100-1200 CsI-run145-segs:0,1,2

Analysis in progress

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ACFI-FRIB Workshop, Oct. 23-25, 2014 16

Michigan State University National Science Foundation

Instrumental effects

Property NaI(Tl) CsI(Na) Effect Signal decay time 230 ns 630 ns Pile-up Average Z 32 54 Bremsstrahlung Composition Na, I Cs, I Induced reactions

Comparison of detector properties

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Measurement of the spectrum shape in 20F decay

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ACFI-FRIB Workshop, Oct. 23-25, 2014 18

Michigan State University National Science Foundation

Spectrum shape in 20F decay

  • The measurement of the WM form factor in 20F provides the most

sensitive test of the strong form of CVC.

  • Measure the beta spectrum shape in coincidence with the subsequent g
  • ray. (P. Voytas et al.)

Implantation detector CsI(Na) array

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Correlation measurements with polarized beams

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ACFI-FRIB Workshop, Oct. 23-25, 2014 20

Michigan State University National Science Foundation

Context

  • N. Severijns and O.Naviliat-Cuncic,

Annu.Rev.Nucl.Part.Sci. 61 (2011) 23

  • Measurements of the longitudinal

polarization of beta particles from pure F and pure GT transitions provide the most stringent constraints on tensor couplings.

  • Relative measurements with

polarized nuclei offer enhanced sensitivity to the mass scale of RHC.

  • Potential candidates: 21N and 37K
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ACFI-FRIB Workshop, Oct. 23-25, 2014 21

Michigan State University National Science Foundation

37K production

Bρ 3,4= 2.50310 Tm Bρ 1,2= 2.65770Tm 957 mg/cm2 Wedge 957 mg/cm2

Courtesy: Chandana Sumithrarachchi (adapted)

  • Production rate 1.3×105 pps/pnA
  • dp/p = 0.5%

40Ca, 140 MeV/A

(50 pnA max)

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ACFI-FRIB Workshop, Oct. 23-25, 2014 22

Michigan State University National Science Foundation

37K thermalization

Courtesy: Chandana Sumithrarachchi (adapted)

Alkali ion-source ANL gas catcher (He) To low energy area Ion Extraction system

37K

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ACFI-FRIB Workshop, Oct. 23-25, 2014 23

Michigan State University National Science Foundation

Transport efficiencies and rates

Out of gas catcher (pps) Transport to RFQ RFQ transmission Transport BECOLA Extracted (pps) Demonstrated 4×104 0.72 0.80 0.1 2×103 Projected 105 0.70 0.75 0.5 2.6×104 BECOLA

Polarization in BECOLA by collinear optical pumping

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ACFI-FRIB Workshop, Oct. 23-25, 2014 24

Michigan State University National Science Foundation

Double arm positron polarimeter

(Side view) (Top view)

Time resolved spectroscopy of Ps decay

J

beta polarimeter

b

nucelar spin

q

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ACFI-FRIB Workshop, Oct. 23-25, 2014 25

Michigan State University National Science Foundation

Polarimetry improvements

Parameter Factor Analyzing power 1.7 Depolarization in matter 2.0 g detection efficiency 4.0 Nuclear polarization 2.0 Total (sensitivity) 13

Projected improvements relative to LLN/ ETH/ PSI Ps polarimeter

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ACFI-FRIB Workshop, Oct. 23-25, 2014 26

Michigan State University National Science Foundation

Summary 1

  • Hadronic contributions (WM) should manifest on the way to

a precision measurement of b. This provides a sensitive test to any experimental technique.

  • We have explored the use of implanted ions from

fragmentation reactions at NSCL and have performed a high statistics measurement of the 6He beta energy spectrum.

  • The first shot [108 net events in 2 days] indicates that beam

induced activation is ~3 times smaller than ambient background.

  • Data analysis is under way
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ACFI-FRIB Workshop, Oct. 23-25, 2014 27

Michigan State University National Science Foundation

Summary 2

  • We are building a positron polarimeter with a factor of ~10

improved sensitivity.

  • The polarimeter will be installed at the low energy beam

line BECOLA and will enable measurements of beta longitudinal polarizations from polarized nuclei.

  • The first phase will consist of “energy integrated

measurements” of beta longitudinal polarizations.

  • …
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ACFI-FRIB Workshop, Oct. 23-25, 2014 28

Michigan State University National Science Foundation

Differential longitudinal polarization

RL0(E) in 21Na decay J=0.4 0.8 1.0 J

beta polarimeter

b

nucelar spin

q

Never measured in nuclear decays

For muon decay see R. Prieels et al. 1408.1472

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ACFI-FRIB Workshop, Oct. 23-25, 2014 29

Michigan State University National Science Foundation

People

  • V. Bader1, D. Bazin1, S. Beceiro-Novo1, M. Bowry1, W. Buhro1, A.

Gade1, M. Hughes1, X. Huyan1, S. Liddick1, K. Minamisono1, O. Naviliat-Cuncic1, S. Noji1, S. Paulauskas1, A. Simon1, P. Voytas2, D. Weisshaar1

1 NSCL/Michigan State University, MI, USA 2 Wittenberg University, OH, USA