how much does a neutrino weigh ? - slac national ...€¦ · how much does a neutrino weigh ?...

How much does aHow much does aneutrino weigh ?neutrino weigh ?

OutlineOutline••Survey of neutrino physicsSurvey of neutrino physics••What is double beta decay and What is double beta decay and

why is it interesting ?why is it interesting ?••Present limitsPresent limits••Description of the EXO experimentDescription of the EXO experiment

Stanford 22 Oct 02 How much does a neutrino weigh ? 2

Z.Djurcic, A.Piepke Physics Dept, University of AlabamaP.Vogel Physics Dept CaltechR.deVoe IBM Almaden and Stanford Phys. Dept.M.Moe Physics Dept UC IrvineD. Akimov, M.Danilov, A.Dolgolenko, O.Zeldovich ITEP MoscowJ-L.Vuilleumier Physics Dept University of NeuchatelG.Bower, M.Breidenbach, R.Conley, C.Hall, A.Odian, C.Prescott,

P.Rowson, K.Skarpaas, K.Wamba SLACE.Conti, G.G., T.Koffas, S.Waldman,

J.Wodin Physics Dept Stanford UniversityP.Picchi Physics Dept University of TorinoG.Giannini Physics Dept University of Trieste

EEnriched nriched XXenon enon OObservatorybservatoryfor double beta decayfor double beta decay


MeVeHpp e 42.02 +++→+ + ν

ννee are abundant byare abundant by--products of products of nuclear fusion in the sunnuclear fusion in the sun

MeVHpep e 44.12 ++→++ − ν

MeVHepH 49.532 ++→+ γ

MeVpHeHe 86.12233 ++→+ α MeVBeHe 59.173 ++→+ γα eepHe να ++→+ +3

MeVLieBe e 8617.077 +++→+ − νγ MeVBpBe 14.087 ++→+ γ

MeVpLi 35.177 ++→+ αα MeVeBeB e 6.1488 +++→ + ν

MeVBe 38 ++→ αα

““pp” 99.75%pp” 99.75%

86%86% ““hephep” 2.4*10” 2.4*10--55

““77BeBe”” 99.89%99.89%

““pep” 0.25%pep” 0.25%

0.11%0.11%

14%14%

““88BB”” 0.11%0.11%


L=10L=1088kmkm

3 types of experiments 3 types of experiments detecting solar neutrinosdetecting solar neutrinos

••Chlorine: Chlorine: 3737Cl+Cl+ννee==3737Ar+eAr+e--

1 exp running >30 yrs (US)1 exp running >30 yrs (US)

••Gallium: Gallium: 7171Ga+Ga+ννee==7171Ge+eGe+e--

3 exp (Russia, Italy) 3 exp (Russia, Italy)

••CerenkovCerenkov: : ee--++ννee==ee--++ννee3 exp (Japan, Canada)3 exp (Japan, Canada)


Conclusion:Conclusion:

•• We detect ns ! : We detect ns ! : nuclearnuclearfusion powers the sunfusion powers the sun

•• The sun is still shiningThe sun is still shining(this is not trivial: it (this is not trivial: it takes ~ 1Myr for atakes ~ 1Myr for aphoton to emerge photon to emerge

from the sun)from the sun)

The sun imaged with neutrinos The sun imaged with neutrinos (courtesy (courtesy R.SvobodaR.Svoboda and the SK and the SK collabcollab.).)

2002 Physics Nobel Prize

2002 Physics Nobel Prize

to Ray Davis

to Ray Davis


Conclusion’:Conclusion’:

We do not see We do not see enough enough ννs !s !

• do we understand• do we understandthe sun well the sun well enough ?enough ?

• are • are ννs playing s playing tricks ?tricks ?

““It starts to be really interesting ! It would be nice if all tIt starts to be really interesting ! It would be nice if all this will endhis will endwith something unexpected from the point of view of particle pwith something unexpected from the point of view of particle physics.hysics.Unfortunately it will not be easy to demonstrate this, even if nUnfortunately it will not be easy to demonstrate this, even if natureature

works this way…” works this way…” B.PontecorvoB.Pontecorvo, 1972, 1972

•• do we understanddo we understandthe sun wellthe sun wellenough ?enough ?

•• are are ννs s playingplayingtricks ?tricks ?


More hints: Atmospheric NeutrinosMore hints: Atmospheric Neutrinos

νν detectordetector

pp

ππππ

ππ

ννµµ

µµ

ee

ννµµ

ννee

1010--20km20km

atmosphereatmosphere

At low energy (~At low energy (~GeVGeV) expect) expect

eNN νν µ

2≅


Atmospheric Neutrinos: Ratio of RatiosAtmospheric Neutrinos: Ratio of Ratios


EarthEarth

DownDown--going going ννL~20 kmL~20 km

UpUp--going going ννL~13000 kmL~13000 km

Is there a way to tell if the effect is due to Is there a way to tell if the effect is due to neutrino properties ?neutrino properties ?

νν detectordetector


Up goingUp going Down goingDown going

Indeed around 1 Indeed around 1 GeVGeVthe the ννµµ flux dependsflux depends

on the angle !!on the angle !!

At higher and lower At higher and lower energies the angularenergies the angularbehavior is consistentbehavior is consistent

with oscillationswith oscillations


What is produced and What is produced and detected isdetected is

If mIf mνν is nonis non--zerozero then leptons could behave like quarksthen leptons could behave like quarksthe weak interaction the weak interaction eigenstateeigenstate is a superpositionis a superposition

of mass of mass eigenstateseigenstatesjν

∑=j

ljlj U νν is a unitaryis a unitarymatrix (like the CKMmatrix (like the CKMmatrix for quarks) matrix for quarks)

33×jlU

What propagates is the mass What propagates is the mass eigenstateeigenstate lν

)0()0()( )2/()( 2

lLEmi

lLptEi

ljii eet ννν −−− ≅=

Flight pathFlight path

AssumingAssuming

iiii mpmEE >>>>=jν


jljj l

LEmiljl

LEmi

lljj UeUeU ll

′′′

−− ∑∑∑ ≅≅ ννν *)2/()2/( 22

……that is neutrinos “acquire” components from otherthat is neutrinos “acquire” components from otherflavors as they propagateflavors as they propagate

We can define a “transition probability” We can define a “transition probability”

2)2/(* 2

),( ∑ −′′ =→

l

LEmiljljjj

leUULP νν

……a periodic functiona periodic functionof the baseline of the baseline LL


For 2 flavors this simplifies:For 2 flavors this simplifies:

−

=θθθθ

cossinsincos

U

ELmLP e

222 3.1sin2sin),( ∆

=→ θνν µ

Only one mixing parameter Only one mixing parameter θθ

22

21 mm −[eV[eV22]] [km][km]

[[MeVMeV]]

Neutrino oscillations Neutrino oscillations 0≠νm


More terrestrial experimentsMore terrestrial experimentsacquiring data:acquiring data:

KamLAND, MINOS, CNGS,…KamLAND, MINOS, CNGS,…

The oscillation The oscillation phenomenon discoveredphenomenon discovered

with atmospheric with atmospheric ννs starts tos starts toemerge also in longemerge also in long--baselinebaseline

terrestrial experimentsterrestrial experiments


There is strong evidence for There is strong evidence for neutrino oscillationsneutrino oscillations

→→ Neutrino masses Neutrino masses ≠≠ 0 !0 !


Very different mass patterns are possible:

ν1

ν2

ν3

ν1

ν2

ν3

00M

ν

Mν

Degenerate …or… hierarchical ?Degenerate …or… hierarchical ?(even more complicated if LSND is right)(even more complicated if LSND is right)

∆Msolar

∆Matmospheric

∆Msolar

∆Matmospheric


Mνe< 2.2 eV 95%CLfrom 3H decay in β spectrometer

At this level measurements sensitive to atomic/moleculareffects…very difficult measurements

lower limit fromoscillations

The sensitivity on the massThe sensitivity on the massof other neutrinos is not of other neutrinos is not

particularly usefulparticularly useful

Kinematics measurementsKinematics measurements


Possible Possible systematicssystematics::••dE/dxdE/dx in sourcein source••detector resolutiondetector resolution••final state corrections final state corrections from atomic and from atomic and molecular physicsmolecular physics

Other problem:Other problem:mostmost of the eventsof the eventsin the spectrum in the spectrum are not useful !are not useful !

Study the spectralStudy the spectralshape near theshape near the

ββ endpoint of tritiumendpoint of tritium


A n

ew s

pect

romet

er: KA

TRIN

A n

ew s

pect

romet

er: KA

TRIN

Expected sensitivity 0.4 eV2

8m……assuming assuming systematicssystematics can be understoodcan be understood


There are two varieties of ββ decay

2ν mode: a conventional2nd order process in nuclear physics

0ν mode: a hypothetical process can happen only if: Mν ≠ 0

ν = ν Sinc

e heli

city

has t

o “f

lip”


Neutinoless double beta decay is not the only possible lepton non-conserving process:

∆L = 2 ββ ββ decaydecay∆L = 0, ∆Lf =1 Flavor oscillationsFlavor oscillations

µµ →→ eeγγ∆L = 2, ∆Lf =1 µµ-- + + ZZA A →→ ee+ + + + Z+2Z+2AA

Using oscillation data and the unitarity of the Maki-Nakagawa-Sakata matrix, one can derive estimated

rates for these processes: ββ and oscillations are most sensitive to lepton

non-conservation


Interesting to note that the idea of doubleInteresting to note that the idea of double--beta decay beta decay is almost as old as neutrinos themselves:is almost as old as neutrinos themselves:

The possibility of neutrinosThe possibility of neutrinos--less decay was less decay was first discussed in 1937first discussed in 1937

••G. G. RacahRacah, , NuovoNuovo CimentoCimento 14 (1937) 32214 (1937) 322••E. E. MajoranaMajorana, , NuovoNuovo CimentoCimento 14 (1937) 17114 (1937) 171

Even earlier the study of nuclear structure led to Even earlier the study of nuclear structure led to the conclusion that the 2 neutrino mode would have the conclusion that the 2 neutrino mode would have

half lives in excess of 10half lives in excess of 102020 yearsyears••M.GoeppertM.Goeppert--Mayer, Phys. Rev. 48 (1935) 512Mayer, Phys. Rev. 48 (1935) 512


ββ ββ always a second order process: only detectable always a second order process: only detectable if first order if first order ββ decay is energetically forbiddendecay is energetically forbidden

2νββ has been observed in a number of cases

0νββ has never been observed


5.63.367150Nd→150Sm8.92.479136Xe→136Ba34.52.533130Te→130Xe5.642.228124Sn→124Te7.52.802116Cd→116Sn11.82.013110Pd→110Cd9.63.034100Mo→100Ru2.83.35096Zr→96Mo9.22.99582Se→82Kr7.82.04076Ge→76Se0.1874.27148Ca→48Ti

Candidate Q Candidate Q AbundAbund..((MeVMeV) (%)) (%)

Double beta decayDouble beta decaycandidates with candidates with

Q > 2 Q > 2 MeVMeV


−−+ ++′→ eeNN AZ

AZ 2

++− ++′→ eeNN AZ

AZ 2

+−

− +′→+ eNeN AZ

AZ 2

NeeN AZ

AZ ′→++ −

−−2

Note that along with the double Note that along with the double ββ-- decaydecay

there is also a there is also a ββ++ mode that in practice would appear mode that in practice would appear as a single or double electron captureas a single or double electron capture

All these processes are phaseAll these processes are phase--space suppressedspace suppressedrespect respect to the to the ββ-- casecase and are usually not consideredand are usually not considered


Mechanisms other than finite Majoranamasses can be responsible for ββ0ν decay

• Neutrino Exchangelight νs: our main focusheavy νs

• Majorons• SUSY particles• Leptoquark exchange• Violation of Lorentz Invariance• Violation of the equivalence principle

ββ0ν ββ0ν alwaysalways implies new physicsimplies new physics


( )12

02

0002/1

2 ,

−

−= νββνββνββνββ

FV

AGTee M

ggMZEGTm

If 0νββ is due to light ν Majorana masses

eem effective effective MajoranaMajorana massmass

FM GTM can be calculated withincan be calculated withinparticular nuclear modelsparticular nuclear models

νββ0G a known a known phasespacephasespace factorfactor

andand

νββ02/1T

is the quantity to is the quantity to be measuredbe measured


ν mass from kinematics measurements

ν mass from ββ0ν decay(ε = ±1 if CP is conserved)

=

3

2

1

3,2,1,

3,2,1,

3,2,1,

ννν

ννν

τττ

µµµ

τ

µ

UUUUUUUUU eeee

∑=

=3

1

22,

iiie mUmβ

∑=

=3

1

2,

iiiieee mUm ε

Cancellations are possible…Cancellations are possible…


So, if one discovers neutrinoSo, if one discovers neutrino--less doubleless double--beta beta decay, at the same time:decay, at the same time:

•• one new parameter of the NMS matrix, involvingone new parameter of the NMS matrix, involvingmasses (and not mass differences) masses (and not mass differences) becomes knownbecomes known

••The The MajoranaMajorana nature of neutrinos is ascertainednature of neutrinos is ascertained

……but…but…If one does NOT observe neutrinoIf one does NOT observe neutrino--less doubleless double--betabetadecay nothing is learnt on neutrino masses (or theirdecay nothing is learnt on neutrino masses (or their

Majorana/DiracMajorana/Dirac nature)nature)


Nuclear matrix elements calculationsNuclear matrix elements calculations• |M2ν| - has stronger dependence on

intermediate states• |M0ν| - all multipoles contribute

- ν propagator results in long range potential

Thus |M2ν| calc., which can be compared to experiment, are not a good guide to |M0ν|

There are no experimental tests of |M0ν|

There is probably an uncertainty of a factor “a few”There is probably an uncertainty of a factor “a few”


Half lives in Half lives in 10102626 yr units for yr units for <m<mνν> = 50 > = 50 meVmeV according according to different nuclear matrix element calculationsto different nuclear matrix element calculations

(from (from S.ElliottS.Elliott & & P.VogelP.Vogel hephep--ph/0202264)ph/0202264)

a) deformed nucleus, deformation not taken into account


0νββ decay canbe separated

from other modesusing kinematics

0νββ

2νββ

χββχ Majoron, the Goldstoneboson of lepton symm

breaking


The “background” 2The “background” 2νν double beta decay has double beta decay has been observed in many isotopes been observed in many isotopes

(from (from S.ElliottS.Elliott & & P.VogelP.Vogel hephep--ph/0202264)ph/0202264)

†Results disagree, error is spread of results(1,2,3)Geochemical experiments


Candidate Detector Present <m> (eV)nucleus type (kg yr) T1/2

0νββ (yr) QRPA NSM

48Ca 9.5*1021 (76%CL)76Ge Ge diode* ~30 1.9*1025 (90%CL) 0.35 1.0 82Se 2.7*1022 (68%CL) 100Mo 5.2*1022 (68%CL)116Cd 7.0*1022 (90%CL)130Te TeO2 cryo ~1 1.4*1023 (90%CL) 1.1 2.6136Xe Xe TPC ~8 4.4*1023 (90%CL) 1.8 5.2150Nd 1.2*1021 (90%CL)

Present Limits for 0Present Limits for 0νν double beta decaydouble beta decay


There is a clear opportunity to make an important discovery if one pushes the <m> sensitivity to the

0.01 - 1 eV region

Can the sensitivity be pushed this far ?Can the sensitivity be pushed this far ?


Main experimental problems

1 Very large fiducial mass (tons)(except for Te) need isotopic enrichment

2 Reduce and control backgrounds in qualitatively new ways bkgnd for Ge ~0.3 ev/kg yr FWHM

For no For no bkgndbkgndFor a For a bkgndbkgnd scaling scaling

like like NtNt1 is essential1 is essential

1 without 2 is a waste1 without 2 is a waste

NtTm /1/1 02/1 ∝∝ νββ

ν

( ) 4/102/1 /1/1 NtTm ∝∝ νββ

ν


XeXe is ideal for a large experimentis ideal for a large experiment••No need to grow crystalsNo need to grow crystals••Can be reCan be re--purified during the experimentpurified during the experiment••No long lived No long lived XeXe isotopes to activateisotopes to activate••Can be easily transferred from one detector to Can be easily transferred from one detector to

another if new technologies become availableanother if new technologies become available••Noble gas: Noble gas: easy(ereasy(er) to purify) to purify••136136Xe enrichment easier and safer:Xe enrichment easier and safer:

-- noble gas (no chemistry involved)noble gas (no chemistry involved)-- centrifuge feed rate in gram/s, all mass usefulcentrifuge feed rate in gram/s, all mass useful-- centrifuge efficiency centrifuge efficiency ∝∝ ∆∆mm. For . For XeXe 4.7 4.7 amuamu

••129129Xe is a Xe is a hyperpolarizablehyperpolarizable nucleus, under studynucleus, under studyfor NMR tomography… a joint enrichmentfor NMR tomography… a joint enrichmentprogram ?program ?


XeXe offers a qualitatively new tool against background:offers a qualitatively new tool against background:136136Xe Xe 136136BaBa++++ ee-- ee-- final state can be identified final state can be identified

using optical spectroscopyusing optical spectroscopy ((M.MoeM.Moe PRC44 (1991) 931)PRC44 (1991) 931)

BaBa++ system best studiedsystem best studied((NeuhauserNeuhauser, , HohenstattHohenstatt,,ToshekToshek, , DehmeltDehmelt 1980)1980)Very specific signatureVery specific signature

“shelving”“shelving”Single ions can be detectedSingle ions can be detectedfrom a photon rate of 10from a photon rate of 1077/s/s

••Important additionalImportant additionalconstraintconstraint

••Huge backgroundHuge backgroundreductionreduction

22PP1/21/2

44DD3/23/2

22SS1/21/2

493nm493nm650nm650nm

metastablemetastable 47s47s


The The BaBa--tagging, added to a conventional tagging, added to a conventional XeXe TPC rejectionTPC rejectionpower provides the tools to develop a backgroundpower provides the tools to develop a background--freefree

nextnext--generation bb experimentgeneration bb experiment

Energy resolution is still an allEnergy resolution is still an all--important parameter to important parameter to disentangle the disentangle the 0νββ0νββ mode from mode from 2νββ2νββ

Assume an “asymptotic” Assume an “asymptotic” fiducialfiducial mass of mass of 10 tons of 10 tons of 136136Xe at 90%Xe at 90%

A somewhat natural scale:A somewhat natural scale:•• World production of World production of XeXe is ~30 ton/yris ~30 ton/yr•• Detector sizeDetector size•• 22∗∗101033 size increase: good match to the size increase: good match to the

1010--22 eVeV mass regionmass region

Mainly going inMainly going inlight bulbs andlight bulbs and

satellite propulsionsatellite propulsion


Two detector options under considerationTwo detector options under consideration

High Pressure gas TPCHigh Pressure gas TPC••20 20 atmatm, 35 m, 35 m33 modules, modules,

4.2 ton/module, 2 modules4.2 ton/module, 2 modules••XeXe enclosed in a nonenclosed in a non--structural structural

bagbag•• ββ range ~5cm: can resolve range ~5cm: can resolve

2 blobs2 blobs••2.5m e2.5m e--drift at ~250kVdrift at ~250kV••Readout Readout XeXe scintillation withscintillation with

WLSB (T0)WLSB (T0)••Additive gas: quenching and Additive gas: quenching and

BaBa++ ++ BaBa+ + neutralizationneutralization••Steer lasers or drift Steer lasers or drift BaBa--ion to ion to

detection regiondetection region

Liquid Liquid XeXe chamberchamber••Very small detector (3mVery small detector (3m33 for for

10tons)10tons)••Need good E resolutionNeed good E resolution••Position info but blobs not resolvedPosition info but blobs not resolved••Readout Readout XeXe scintillationscintillation••Can extract Can extract BaBa from hifrom hi--density density XeXe••Spectroscopy at low pressure:Spectroscopy at low pressure:

136136Ba (7.8% Ba (7.8% nat’lnat’l) different ) different signature from natural signature from natural BaBa(71.7% (71.7% 138138Ba)Ba)

••No quencher needed, neutralization No quencher needed, neutralization done outside the done outside the XeXe


Conceptual scheme of a high pressure Conceptual scheme of a high pressure XeXe gas TPC with laser tagginggas TPC with laser tagging


Some tradeoffs of a Some tradeoffs of a LXeLXe optionoptionDisadvantages:Disadvantages:

••No information from trackingNo information from tracking••Cannot “bring laser Cannot “bring laser

to the event”to the event”

Advantages:•No high pressure•Table top•Ba can be analyzed at low density•Ba++ neutralization easier

Advantages:Advantages:••No high pressureNo high pressure••Table topTable top••BaBa can be analyzed at low densitycan be analyzed at low density••BaBa++++ neutralization easierneutralization easier

Unknowns:Unknowns:••Is energy resolution sufficient ?Is energy resolution sufficient ?••BaBa extraction with good efficiencyextraction with good efficiency

••Tip is triggered by Tip is triggered by LXeLXe readoutreadout••Biased Biased –– to grab and + to releaseto grab and + to release••Special care to ensure Special care to ensure BaBa releaserelease

••XeXe ice tip coatingice tip coating••Hot Ta tipHot Ta tip••Atomic Force Microscope tipAtomic Force Microscope tip

••BaBa analyzed in a low pressure analyzed in a low pressure spectroscopy cellspectroscopy cell


R&D in progressR&D in progress

••Single ion Single ion BaBa++ tagging at different residual tagging at different residual XeXe pressures pressures ••LXeLXe energy resolutionenergy resolution••XeXe purification for long epurification for long e-- lifetime and lifetime and radioimpuritiesradioimpurities••BaBa ion lifetime and grabbing from ion lifetime and grabbing from LXeLXe••Procurement/qualification of low background materialsProcurement/qualification of low background materials••Isotopic enrichment of Isotopic enrichment of 136136XeXe••Construction/operation of 100Construction/operation of 100--200 kg 200 kg

136136Xe prototype detectorXe prototype detector


Single ion Single ion BaBa++ spectroscopy in residual spectroscopy in residual XeXePP--state state collisionalcollisional broadeningbroadening

••Ion traps usually work in UHV with em field used to trap ionsIon traps usually work in UHV with em field used to trap ions••Buffer gases (usually He) are also used in trapping and coolingBuffer gases (usually He) are also used in trapping and cooling••BaBa+ + natural natural linewidthlinewidth = 20MHz, expect 100 GHz FWHM at 20 = 20MHz, expect 100 GHz FWHM at 20 atmatm••Scaling checks well with neutral Scaling checks well with neutral BaBa in in ArAr [PRA46 (1992) 2642][PRA46 (1992) 2642]

(~1GHz @ 0.5 (~1GHz @ 0.5 atmatm))

Is the D state still Is the D state still metastablemetastable ??••MetastableMetastable D state (47 s ) in vacuum important for shelvingD state (47 s ) in vacuum important for shelving••Neutral Neutral BaBa has 240ms D state in vacuum that retains same has 240ms D state in vacuum that retains same

lifetime in 0.5 lifetime in 0.5 atmatm ArAr

Are Are BaBa++ ions stableions stable••Lifetime in vacuum: years, same in Lifetime in vacuum: years, same in ultrapureultrapure HeHe


Test UHV/high pressure ion trapTest UHV/high pressure ion trap

RF RF quadrupolequadrupole trap trap loaded in UHV from loaded in UHV from

a a BaBa dispenserdispenserand eand e--beam ionizerbeam ionizer

XeXe can be injected can be injected while observing while observing

the ionsthe ions


EXO spectroscopy labEXO spectroscopy lab

Blue and red lasersBlue and red laserswith diagnosticswith diagnostics

Ion trapIon trap


~RF applied~RF applied BaBa ovenoven

laser, laser, BaBa ionizerionizerand detectionand detectionlineline--ofof--sightsightthrough thesethrough these

gapsgaps


CCD image of an ion in the trapCCD image of an ion in the trap

traptrapedgeedge


Using a PMT one can observe the signal Using a PMT one can observe the signal resonance for a single ionresonance for a single ion


Indeed we are talking about single ions: one can load the trapIndeed we are talking about single ions: one can load the trapwith multiple ions and then observe the signal intensity as ionswith multiple ions and then observe the signal intensity as ions

are dropped one by one…are dropped one by one…

Zero ion backgroundZero ion background

Now sta

rting t

o

Now sta

rting t

o

experi

ment sa

me

experi

ment sa

me

thing

in

thing

in XeXeatm

ospher

e

atmosp

here


Pancake shaped 1liter Pancake shaped 1liter LXeLXe ionization chamber to test energy resolutionionization chamber to test energy resolutionGood acceptance to scintillation light AND ionizationGood acceptance to scintillation light AND ionization

Reconstruct energy Reconstruct energy as linear combination as linear combination of ionization and of ionization and scintillation signalsscintillation signals

There are There are indications indications that correlations that correlations between the two between the two variables help variables help improving resolutionimproving resolution[[J.SeguinotJ.Seguinot et al. et al. NIM A 354 (1995) 280]NIM A 354 (1995) 280]


1liter test 1liter test chamberchamber

OxysorbOxysorb

XeXe storagestorage

XeXe dumpdump

CryostatCryostat(missing here)(missing here)

1liter 1liter LXeLXe pancake chamber setup at Stanfordpancake chamber setup at Stanford


1 kV/cm

Found a clear (Found a clear (anti)correlationanti)correlation between ionization and scintillationbetween ionization and scintillation

~570 ~570 keVkeV


The best resolution is obtained by a linear combination of theThe best resolution is obtained by a linear combination of thescintillation and ionization signalsscintillation and ionization signals

ionization onlyionization only


Compilation of resolutionCompilation of resolutiondata in data in LXeLXe

This can be used to improve the resolution in This can be used to improve the resolution in LXeLXeand separate the 2and separate the 2νν from the 0from the 0νν modesmodes

……important not onlyimportant not onlyfor EXO but alsofor EXO but also

for industrial/medicalfor industrial/medicalapplicationsapplications

where the high densitywhere the high densityof of LXeLXe make it a make it a desirable mediumdesirable medium

this workthis work


thin

source

thin

source

Th recoils out

Th recoils outIon grabbing test uses a Ion grabbing test uses a

222222Ra source to simulate Ra source to simulate BaBa

Atom Ionization potentialAtom Ionization potentialI (I (eVeV) II) II

SrSr 5.695 11.0305.695 11.030BaBa 5.2117 10.0045.2117 10.004Ra 5.279 10.147Ra 5.279 10.147

BaBa and Ra hav

e

and Ra hav

e

similar chemistry

similar chemistry

Pa produced in a cyclotronPa produced in a cyclotron230230Th + p Th + p →→ 230230Pa + 3nPa + 3n

230230Pa (17.4d)Pa (17.4d)

214214Po (164ms)Po (164ms)

230230U (20.8d)U (20.8d)

222222Ra (38s)Ra (38s)

210210Pb (22yr)Pb (22yr)

226226Th (30.5min)Th (30.5min)

218218Rn (35ms)Rn (35ms)

230230Th (8*10Th (8*1044yr)yr)

91.6%91.6%8.4%8.4% ββ

5.99MeV5.99MeV

6.45MeV6.45MeV

6.68MeV6.68MeV

7.26MeV7.26MeV

7.83MeV7.83MeV

ECECαα

αα

αα

αα

αα

collect on the tipcollect on the tip

very

spe

cific

sign

atur

eve

ry s

pecific

sign

atur

e


First Ra ions being grabbedFirst Ra ions being grabbeddetected from their decaysdetected from their decays

in an in an αα countercounter


Isotopic enrichment for a gaseous substance like Isotopic enrichment for a gaseous substance like XeXe is is most economically achieved by ultracentrifugationmost economically achieved by ultracentrifugation

136136Xe being the heaviestXe being the heaviestXeXe isotope is particularlyisotope is particularly

easy to separate.easy to separate.

This separation step thatThis separation step thatrejects the light fraction is rejects the light fraction is

also very effective in removingalso very effective in removing8585Kr (TKr (T1/21/2=10.7 yr) that is=10.7 yr) that is

constantly produced by fissionconstantly produced by fissionin nuclear reactors.in nuclear reactors.


Russia has enoughRussia has enoughproduction capacityproduction capacityto process 100 ton to process 100 ton

XeXe and extract and extract 10 ton 10 ton 136136Xe in a Xe in a

finite timefinite time


First 100 kg test production completed in Apr ’02 funded by StanFirst 100 kg test production completed in Apr ’02 funded by Stanford,ford,SLAC and U of Alabama. SLAC and U of Alabama. This is already the largest nonThis is already the largest non--fissilefissile

isotope enrichment program ever entertained !isotope enrichment program ever entertained !Another 100 kg run started in early Oct, funded by Another 100 kg run started in early Oct, funded by DoEDoE

Isotope Isotope NatlNatl XeXe Enriched Enriched XeXe124 0.11 0.000124 0.11 0.000126 0.12 0.000126 0.12 0.000128 3.58 0.000128 3.58 0.000129 27.32 0.005129 27.32 0.005130 5.20 0.001130 5.20 0.001131 21.39 0.007131 21.39 0.007132 24.35 0.079132 24.35 0.079134 9.95 10.381134 9.95 10.381136 7.97 89.527136 7.97 89.527

In natural sample In natural sample 8484Kr/Xe measured to be (4.4Kr/Xe measured to be (4.4±±1.5)1.5)∗∗1010--7 7 (as expected)(as expected)In enriched sample cannot detect Kr: In enriched sample cannot detect Kr: 8484Kr/Xe <3.4Kr/Xe <3.4∗∗1010--77at 90%CLat 90%CL

More sensitive measurements to be done on a better mass spectromMore sensitive measurements to be done on a better mass spectrometereter


A 100A 100--200 kg prototype detector is slated to be installed200 kg prototype detector is slated to be installedat at DoE’sDoE’s Waste Isolation Pilot Plant (WIPP), Carlsbad NMWaste Isolation Pilot Plant (WIPP), Carlsbad NM


A salt mine where to store the military radioactive waste…A salt mine where to store the military radioactive waste……and perform low background physics experiments…and perform low background physics experiments


EXOEXO--prototype lab at WIPPprototype lab at WIPP


ConclusionsConclusions

Isotope Isotope DetDet mass Enrich. mass Enrich. EffEff. . MeasurMeasur. Background T. Background T1/21/20νββ0νββ <<mmνν> (> (eVeV))

(kg) (%) (%) time (yr) (kg) (%) (%) time (yr) (yr) QRPA NSM(yr) QRPA NSM

136136XeXe** 1000 80 70 5 0 + 1.8 events 1000 80 70 5 0 + 1.8 events 8.3*108.3*1026 26 0.051 0.140.051 0.14136136XeXe**** 10000 80 70 10 0 + 5.5 events 10000 80 70 10 0 + 5.5 events 1.3*101.3*1028 28 0.013 0.0370.013 0.037

Assuming that the Assuming that the XeXe chamber + chamber + BaBa tagging reduce to 0 all tagging reduce to 0 all radioactive background...radioactive background...

** σσ(E)/E = 2.8% (E)/E = 2.8% R.LuescherR.Luescher et al. Phys. et al. Phys. LettLett. B434 (1998) 407. B434 (1998) 407**** σσ(E)/E = 2.0% Modest improvement on the above.(E)/E = 2.0% Modest improvement on the above.

The The meVmeV region is within reach !region is within reach !


The SNO detector recently started to produce dataThe SNO detector recently started to produce data

SNO: 1kton DSNO: 1kton D22OO

−− +→+ ee xx νν−− +→+ ee ee νν

−++→+ eppHe2ν

sensitive to sensitive to ννee onlyonly

SuperKSuperK::

sensitive to a sensitive to a ννe e ,,ννx x mixmix

99.044.5)(13.169.3)( ,

±=

±=

eνφ

νφ τµ -1-26 scm10× It appears like someIt appears like someννee change flavor !change flavor !


Should you believe in:Should you believe in:

by a s

ubset

of the

by a s

ubset

of the

Heide

lberg

Heide

lberg--

Moscow

Moscow

collab

oratio

n

collab

oratio

n

nono

…see details inC.A.Aalseth Mod. Phys. Lett. A17 (2002) 1475 F.Feruglio et al. hep-ph/0201291


Paper’s bottom line is TPaper’s bottom line is T1/2 1/2 = [0.8 = [0.8 –– 18.3] 18.3] ·· 10102525 yr at 95% CLyr at 95% CLbest value is best value is TT1/2 1/2 = = 1.5 1.5 ·· 101025 25 yr corresponding to 0.39 yr corresponding to 0.39 eVeV

Allegedly this is a 2 to 3 sigma effect depending on the analysiAllegedly this is a 2 to 3 sigma effect depending on the analysiss

First consideration: First consideration: the data used is the same that was earlier interpreted asthe data used is the same that was earlier interpreted as

an upper limit Tan upper limit T1/2 1/2 > 1.9 > 1.9 ·· 10102525 eVeV at 90% CLat 90% CL

It is unclear why, there is no discussion about which of theIt is unclear why, there is no discussion about which of thetwo conclusions we should believe.two conclusions we should believe.

Anyway it is quite clear that the result of the experimentAnyway it is quite clear that the result of the experimentdepends strongly on the analysis performed, certainly notdepends strongly on the analysis performed, certainly not

good for what would be a momentous discovery !good for what would be a momentous discovery !


The evidence comes from the search of a peak in the The evidence comes from the search of a peak in the energy spectrum observed in a set of low activity energy spectrum observed in a set of low activity GeGe

detectors inside the detectors inside the GranGran SassoSasso Lab.Lab.This is essentially the only handle one has in a full absorptionThis is essentially the only handle one has in a full absorptioncalorimetric detector. The very high energy resolution ofcalorimetric detector. The very high energy resolution of

GeGe makes the experiment possible.makes the experiment possible.


Some of theSome of the γγ background can be removed by pulse shape analysis:background can be removed by pulse shape analysis:

γγ’’s generally Compton scatter producing ionization in more than ons generally Compton scatter producing ionization in more than one e site, so the signal from the drifted electrons is slowersite, so the signal from the drifted electrons is slower

Electrons from Electrons from ββββ decay stop immediately, depositing all their decay stop immediately, depositing all their energy at one site: faster pulseenergy at one site: faster pulse


2010.72010.7

2016.72016.7 2052.92052.9

2021.82021.8

The fit to the “signal” peak at 2039.006 The fit to the “signal” peak at 2039.006 keVkeV is done is done AFTERAFTER the the subtraction of 4 peaks that are claimed to be subtraction of 4 peaks that are claimed to be UNDERSTOODUNDERSTOOD

background from background from IDENTIFIEDIDENTIFIED lines of lines of 214214BiBiWithout this subtraction the significance of the 2039 peak is evWithout this subtraction the significance of the 2039 peak is evenenless than 2 sigma, as it is evident by just staring at the spectless than 2 sigma, as it is evident by just staring at the spectrumrum

But then, what about the other peaks ! There are more that arBut then, what about the other peaks ! There are more that are e not understood ! And anyway why the resolution is not the samnot understood ! And anyway why the resolution is not the samee

for ALL of the alleged for ALL of the alleged 214214Bi peaks ?Bi peaks ?


But there is more: one can look (as But there is more: one can look (as THEYTHEY should have done) at theshould have done) at thefull spectrum from 100 full spectrum from 100 keVkeV to 2700 to 2700 keVkeV published by the published by the

HeidelbergHeidelberg--Moscow Collaboration in Moscow Collaboration in H.V.KlapdorH.V.Klapdor--KleingrothausKleingrothaus et al., et al., EurEur. Phys. J. A12 (2001) 147. Phys. J. A12 (2001) 147

In the full spectrum the authors identify In the full spectrum the authors identify 214214Bi peaks atBi peaks at609.3 609.3 keVkeV, 1764.5 , 1764.5 keVkeV and 2204.2 and 2204.2 keVkeV. They nicely bracket. They nicely bracket

the interesting range of the spectrum.the interesting range of the spectrum.

The intensity inferred from the reference peaks does not agreeThe intensity inferred from the reference peaks does not agreewith the peaks found around the 2039 structure…with the peaks found around the 2039 structure…

how much does a neutrino weigh ? - slac national ...€¦ · how much does a neutrino weigh ?...

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