the biochemistry of 136 xe david nygren university of texas at arlington 15 december 2014paris tpc -...

Paris TPC - 2014 1

The Biochemistry of 136Xe

David NygrenUniversity of Texas at Arlington

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Paris TPC - 2014

• decay: Rare transition between same A nuclei– Energetically allowed for some even-even nuclei

• (Z,A) → (Z+2,A) + e-1 + n1 + e-

2 + n2

• (Z,A) → (Z+2,A) + e-1 + e-

2

• (Z,A) → (Z+2,A) + e-1 + e-

2 + c

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Two Types of Double Beta Decay

If this process is observed:Neutrino mass ≠ 0

Neutrino = Anti-neutrino!Lepton number is not conserved!

Neutrinoless double beta decay lifetime

Neutrino effective

mass

A known standard model process and an important calibration tool

Z

0

2

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Two Types of Double Beta Decay

If this process is observed:Neutrino mass ≠ 0

Neutrino = Anti-neutrino!Lepton number is not conserved!

Neutrinoless double beta decay lifetime

Neutrino effective

mass

A known standard model process and an important calibration tool

Z

0

2

?

4

The neutrino effective mass mν

• Decay rate ≈ mν2

• Effective mass mν depends on phases:

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Normal

Inverted

Even a null result will constrain the mass spectrum

possibilities!

A mbb limit of ~20 meV would exclude

Majorana neutrinos in an inverted hierarchy.

bb Sensitivity (mixing parameters from arXiv:1106.6028)

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50 meVOr ~ 1027 yr

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The traditional search for neutrino-less decay:

Measure the energy spectrum of the two electrons…Not yet sufficient to reject backgrounds!

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Energy resolution needed:δE/E < 1% FWHM

Historically, there are > 100 experimentallimits on T1/2 of the0nbb decay.Here are the recordsexpressed as limits on<mbb> using one setof nuclear matrix elements (RQRPA ofSimkovic et al. 2009.)

During the last decade the complexity and cost of experimentshas increased verydramatically. The slope constant is now leveling off.

bb trends (updated Elliott/Vogel plot by Vogel)


Heidlelberg-Moscow

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EXO result

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T0n > 1.6 x 1025 ymbb < 140-380 meV120.7 days79.4 kg 136Xe

In tension with H-M result, but caveat of matrix elements. EXO result combined with KamLAND -ZEN rules out H-M claim

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Sensitivity, Background and Exposure

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Various Levels of Confidence in a Result

• Preponderance of the evidence: – Correct peak energy with no 2-ν contamination– Single-site energy deposit– Proper detector distributions (spatial, temporal)– Rate scales with isotope fraction

• Beyond a reasonable doubt: – Observe the daughter atom– Observe the two-electron nature of the event– Measure kinematic dist. (energy sharing, opening angle)– Observe the excited state decay

• Smoking Guns:– See the process consistently in several isotopes – A background-free positive result with enriched isotope– See no peak with depleted isotope – no other changes to detector

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Next Time will be different

• More than a dozen technical/isotopic approaches have been pursued seriously in the past.

• The discovery class experiments will be very costly in resources and time, and very few in number.----------------------------------------------------------------------

• How does a “discovery class” experiment differ from a background-limited technique that can only set a limit?

• Should a background-free requirement be imposed?

• “Eternity is a very long time, especially towards the end” – Woody Allen

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Next Time will be different

• More than a dozen technical/isotopic approaches have been pursued seriously in the past.

• The discovery class experiments will be very costly in resources and time, and very few in number.----------------------------------------------------------------------

• How does a “discovery class” experiment differ from a background-limited technique that can only set a limit?

• Should a background-free requirement be imposed?

• “Eternity is a very long time, especially towards the end” – Woody Allen

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Perspective

Before embarking on any major new project, the NLDBD community should refocus effort on improvements in technique, to evade the quagmire of background contamination.

Where might this focus fall?

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Perspective

Before embarking on any major new project, the NLDBD community should refocus effort on improvements in technique, to evade the quagmire of background contamination.

Where might this focus fall?Identification of the daughter atom

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Identify the barium daughter by optical spectroscopy

(M.Moe PRC44 (1991) 931)

Ba+ system best studied(Neuhauser, Hohenstatt,Toshek, Dehmelt 1980)

Single ions can be detectedfrom a photon rate of 107/s

2P1/2

4D3/2

2S1/2

493nm

650nm

metastable 80s

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Identify the barium daughter by optical spectroscopy

(M.Moe PRC44 (1991) 931)

Ba+ system best studied(Neuhauser, Hohenstatt,Toshek, Dehmelt 1980)

Single ions can be detectedfrom a photon rate of 107/s

Triplet state is quenchedin dense gas!

Can excite with blue, look only for red

Do this in 3-D?Move ion to trap?

2P1/2

4D3/2

2S1/2

493nm

650nm

metastable 80s

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Xenon’s daughter: Ba++ • In the DBD decay of 136Xe, barium daughter will be strongly ionized by

the nascent electrons emerging from the nucleus;

• Partial neutralization occurs by electron capture from neutral xenon atoms ( first ionization potential is 12.14 eV);

• Process stops at Ba++ because second ionization potential of Ba++ is 10.04 eV. It can’t take another electron from neutral xenon.

• Ba++ is the expected outcome in pure xenon;

• For the Ba+ spectroscopy to work, one and only one other electron must come from somewhere: charge exchange,…chemistry?

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Might there be another way?

• Perhaps. Let’s exploit modern biochemistry.

• My idea: The technique of Single Molecule Fluorescent Imaging may be adaptable here.

• SMFI: The transformation of a non-fluorescent precursor into a robust and persistent fluorescent state by capture and chelation of doubly ionized alkaline earth elements, such as Ca++

• Maybe Ba++ too! Ca and Ba are congeners15 December 2014

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Might there be another way?

• Perhaps. Let’s exploit modern biochemistry.

• My idea: The technique of Single Molecule Fluorescent Imaging may be adaptable here.

• SMFI: The transformation of a non-fluorescent precursor into a robust and persistent fluorescent state by capture and chelation of doubly ionized alkaline earth elements, such as Ca++

• Maybe Ba++ too! Ca and Ba are congeners!15 December 2014

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Conformal changes in Fluo-3

15 December 2014

Once Ca++ is captured by Fluo-3, its responsiveness to external excitation increases by a factor of 60 -80. Two-photon excitation with IR is also possible

This might work well for Barium too since barium and calcium are congeners. Fluorophores also exist for for Pb++, Hg++, Cu…

2014 Nobel Prize in Chemistry awarded to three physicists for developing SMFI

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Conformal changes in Fluo-3

15 December 2014

Once Ca++ is captured by Fluo-3, its responsiveness to external excitation increases by a factor of 60 -80. Two-photon excitation with IR is also possible

This might work well for Barium too since barium and calcium are congeners. Fluorophores also exist for for Pb++, Hg++, Cu…

2014 Nobel Prize in Chemistry awarded to three physicists for developing SMFI

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A TPC with biochemistry?

• One can imagine the TPC cathode surface is coated with untransformed fluorophores waiting to respond strongly after capture of one Ba++.

• The Ba++ ion is now fixed to the cathode surface

• One can imagine that the cathode surface is a dielectric belt that transports at a few mm/s the latent image to a line imager.ge of the event, and also the needed energy resolution, a la NEXT

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Information content

• Ionization electrons liberated by the decay electrons provide a 3-D image of the event, and the needed energy resolution, a la NEXT

• This information establishes the domain of possible ion locations to the projected area on the cathode plane.

• Only the one molecule that has captured the barium ion fluoresces brightly under excitation

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Neutrino Experiment - Xenon TPCAsymmetric TPC with “Separated functions”

Transparent -HV cathode

Energy plane Electroluminescent plane

ions

Energy & primary scintillation signals recorded here, with PMTs

Field cage: teflon

EL signal created here

Tracking performed here, with

“SiPMT” array

Virtual Fiducial surface

Operating pressure: 10 -15 bars

electrons

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Topological signature

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NEXT - DBDM. Energy resolution

NEXT-DBDM obtains energy resolution: δE/E = 1.04% FWHM at 667 keV Cs-137 peak ( 0.53% @ Qbb, if not limited by systematics)

No tracking. Hard fiducial cut imposed to select only events in the center.

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NEXT Platform and Pb Castle at LSC

65 t of Pb sheets from OPERA disassembled bricks received as a loan (for all the duration of NEXT) by INFN

Pb bricks (mainly of standard form) produced by Tecnibusa(5% loss)

Three deliveries•7 July•11 August•29 September

Cleaning and assembly made by NEXT

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Perspective

• The field of NLDBD is entering a new era: “Maybe not big enough to succeed,

but too expensive to fail”• Failure: a background-dominated result• The need for a genuine advance is imperative.• Single molecule fluorescent imaging is a novel

idea and may open a new pathway to success.– While highly speculative, it serves both as an

imagination stretcher and a springboard.15 December 2014

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Summary

• The discovery of neutrino-less double beta decay would be a major discovery of new physics beyond the Standard Model.– Backgrounds have been present in all sensitive results – Neutrino mass sets sensitivity goal to span inverted hierarchy

• Discovery class experiments will be very costly ! • The need for a genuine advance is imperative.

– Single molecule fluorescent imaging of Ba++ exploiting biochemistry techniques appears possible, and may be practical and efficient

• A new technique to identify the appearance in space and time of Ba++ in 136Xe NLDBD may be a genuine breakthrough!

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Summary

• The discovery of neutrino-less double beta decay would be a major discovery of new physics beyond the Standard Model.– Backgrounds have been present in all sensitive results – Neutrino mass sets sensitivity goal to span inverted hierarchy

• Discovery class experiments will be very costly ! • The need for a genuine advance is imperative.

– Single molecule fluorescent imaging of Ba++ exploiting biochemistry techniques appears possible, and may be practical and efficient

• A new technique to identify the appearance in space and time of Ba++ in 136Xe NLDBD may be a genuine breakthrough!

Thank you for your attention

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Backup slides

15 December 2014

Experimental Parameters

• W – molecular weight of source• f – isotopic abundance• x – number of bb isotopes per molecule• e – detector efficiency• G0n – decay phase space

• |M0n| - matrix element• b – background in counts/keV-kg-y• DE – energy window in keV• M – mass of source in kg• T – counting time in years


Isotope √(W/(G0n|M0n|2)) x107

Ge 2.4(QRPA) 4.7(SM)

TeO2 1.9(QRPA) 3.1(SM)

Xe 2.4(QRPA) 3.3(SM)

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The Experimental ChallengesMaximize Rate/Minimize Background

Large Mass (~ 1 ton)Large Q value, fast bb(0n)

Good source radiopurityDemonstrated technology

Ease of operationHigh isotopic abundance

Easy enrichmentSmall volume, source = detector

Good energy resolutionSlow bb(2n) rate

Identify daughter in real time Event reconstruction

Nuclear theory

b = background/keVΔE = Energy ROIM = active isotopic masstlive = graduate students

Heidelberg-Moscow claimhas remained a point of

contention

~70 kg-years of data13 years

The “feature” at 2039 keV is arguably present.

Data analysis criticizedfor ex post facto massage

NIM

A52

2, 3

71 (2

004)

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Great Number of Proposed Experiments

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• Calorimeter– Semi-conductors– Bolometers– Crystals/nanoparticles immersed in scintillator

• Tracking – Liquid or gas TPCs– Thin source with wire chamber or scintillator

Splitting the window, or in the case of high-event rates, fitting the spectrum.


Energy scale for Xe

Figure from Mike Moe

Fig. from SNO+

42

Energy resolution

the biochemistry of 136 xe david nygren university of texas at arlington 15 december 2014paris tpc -...

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