2. Double Beta Decays & Neutrinos2. Double Beta Decays & Neutrinos

　　––Present Status--Present Status--

Hiro Ejiri,

JASRI Spring-8; RCNP Osaka Univ.

April 2003, TIT

ContentsContents

I. Double Beta Decays and Neutrinos.II. ββ ExperimentsIII. Present Status of ββ Experiments

Ge, Mo, NEMO, Ca.IV. Concluding Remarks.

II. . Double Beta Decays and Double Beta Decays andNeutrinosNeutrinos

.

Neutrino masses by Neutrino masses by ββββNeutrino studies in nuclei.Unique opportunity in nucleiRare ββ :yes, but huge β no, in even nuclei with pairing force.

Majorana nature of ν

Absolute mass scale & CP phases <mν> = Σmj |Uej |2 ξ

0.01 ∼ 0.06 eV range,which is quite interesting from recentsolar atmospheric reactor and accelerator neutrinooscillation data.

ββββ schemesschemes 2νββ ∆L=0 M(τστσ) Res.

0νββ ∆L=2 Majorana　 < mν> ＝ Σ mjcjvj

2

Absolute mass　scale CP phase R-Weak Currents

M is crucial

Energy spectra of sum of Energy spectra of sum of ββββ

Energy and Angular CorrelationsEnergy and Angular Correlations

ββββ rate and effective rate and effective νν mass mass

Lepton mixing matrixLepton mixing matrix

Neutrino mass hierarchyNeutrino mass hierarchy

Neutrino masses with LMANeutrino masses with LMA

Effective Effective ββββ Neutrino massesNeutrino masses P.Vogel 2001P.Vogel 2001 Normal and Inverse hierarchy Normal and Inverse hierarchy

..

E. Takasugi All approximately equal mass. <mν> ~ 0.03 eV

ββββ processesprocesses

Two nucleon process.Two nucleon process.Isobar processIsobar processPion Pion processprocess

Nuclear Responses (MNuclear Responses (M0ν0ν) for) for ββ ββ by Double by DoubleCharge Exchange ReactionsCharge Exchange Reactions

100Mo ( 11B, 11Li) 100Ru at RCNP

.

II. II. ββββ Experiments Experiments

ββ ββ nucleinuclei

MostlyMostlyββ−− β β--

decays decays with largeQββ

to get large phasespace ~Qββ

5

Phase space of 0Phase space of 0νββνββ G ~ Q G ~ Qββ55 F(Z) F(Z)

8.001.811.891.751.080.2442.44G0v×10-25

(year-1eV-2)

3.372.482.803.033.002.044.27Q-value(MeV)

150Nd136Xe116Cd100Mo82Se76Ge48CaIsotope

NuclearNuclearresponseresponse

forfor ββββ

T(0νββ) = SN[<mν>2 ]

SN= G |M0ν|2

G ~ Qββ5

ββ ββ nucleinuclei

Qββ ΜeV Α % Detector:Int./Ext

48Ca 4.271 0.19 Scinti. Int.76Ge 2.045 7.8 Semi-con. Int.82Se 2.995 9.2 Track Ext.100Mo 3.034 9.6 Track Ext.116Cd 2.802 7.5 Scin/Sem. Int.130Te 2.533 34.5 Bolom. Int.136Xe 2.479 8.9 Track Int.150Nd 3.367 5.6 Track Ext.

Sensitivity to <Sensitivity to <mmνν>> by by ββββ T0ν = G |Mον|2 |<mν>|2 , G = k(Z) Qββ

5 . N0ν = Nββ t / T0ν > [t ∆E NBG]1/2

Sensitivity S = Sn(nuclear) x Sd(detector)

mν-1 ~ S t 1/4

Sn = M 0ν k(Z) Qββ2.5

Sd = Nββ1/2/[∆E NBG]1/4

Large Sensitivity: Large Q and M0ν

Large Detector with Nββ

Small NBG ~ N(2νββ) + RI, small ∆E

0νββ

BG

SSSC Signal Selection by SpatialSSSC Signal Selection by SpatialCorrelationCorrelation

Localization / Segmentation of detectorLocalization / Segmentation of detector Event selection

β−γ e E0, IC1γ Compton-e γ2γ Cascade γ γ: Μulti e in a large volume

βγ

e

2β

SSTC Signal Selection by Time Correlation

B

A Single site for ββ

2 sites within 30 sec for solar β followed by β

Time correlated pre- and post decay signals, B’ and B’’.Time window T ’ < < 1/all event rate / unit cell detector: High K = 1/∆P ~ 10 6-9 and modest low / purity of S-BG rates : b < 10 –3 Bq / ton reduce by 2 orders of magnitude of natural andcosmogenic RI’s with T B1/2 < 2.5 ( K / b ) 10-10 ~days.

Time coordinate T T’

ΤT’

B’

B

B’’

Β’ Β Β”

.

III. Present Status of III. Present Status of ββββExperimentsExperiments

GeGe, Mo, NEMO, Ca., Mo, NEMO, Ca.

Present Status of Present Status of ββββ for for νν mass massEffective Mass limits　Inclusive ββ 76Ge 　H.M. IGEX , Ge Detectors 0.3-1.3 eV, 130Te Cryogenic Bolometor 1.3-2.5 eV 128Te Geo-chemical 1.2—2.4 eV Exclusive ββ spectroscopic studies. 100Mo ELEGANT, 150Nd, 1.5 – 3 eV　　　NEMO 100Mo 82Se others Sub eV

Depend on nuclear matrix elements, factors 2. Limited by the detector sensitivities of SD~ 0.3-1.5 eV.

76GeGeQQββ ~ 2 ~ 2 MeVMeV, not large, but high energy resolution, not large, but high energy resolution

with with Ge Ge (natural and enriched) detector(natural and enriched) detector

IGEX

BG ~ 0.06 / kg/y/keV ~ 0.2 / kg / y

T > 1.57 1025 y <mν> < 0.33—1.3 eV

1. L.Baudis et al PRL 83 ’99 41. > 5.7 10 25 y 90%CL < 0.19 eV s

2.K-K,et al. Eur.Phys. J. A12 ’01 147 > 1.9 90 < 0.33 eV

3. K-K,et al. KDHK Mod. Phys. Lett. 0.8—18.3 95 0.11—0.56 eV * 16 ’01 2409 1.5 Best 0.39 eV

* M0v + 50% 0.05—0.84 eV should be 0.07—1.1 eVLarge dependence on the analysis method.Large inconsistency among the publications on the same data and among the group menbers, only 4 (KDHK)out of ~20 claim

“yes”.

H.M.Data since 1990 & analyses in 1999, 2001

Spectra of HMSpectra of HM　　７６７６GeGe

Single site PSD spectrumSingle site PSD spectrum

Modern Physics Letters A, Feb. 2002Modern Physics Letters A, Feb. 2002

COMMENT ONCOMMENT ON““EVIDENCE FOREVIDENCE FOR

NEUTRINOLESSNEUTRINOLESS　　DOUBLEDOUBLEBETA DECAYBETA DECAY””

.

Authors from 14 Authors from 14 Lab-UnivLab-Univ’’ss

C. E. Aalseth1, F. T. Avignone III2, A. Barabash3, F. Boehm4, R. L. Brodzinski1, J. I. Collar5,

P. J. Doe6, H. Ejiri7, S. R. Elliott6., E. Fiorini8, R.J.Gaitskell9, G. Gratta10, R. Hazama6, K. Kazkaz6,G. S. King III2, R. T. Kouzes1, H. S. Miley1, M. K.Moe11, A. Morales12, J. Morales12, A. Piepke13, R.G. H. Robertson6, W. Tornow14, P. Vogel4, R. A.Warner1, J. F. Wilkerson6

1PNL 2USC 3ITEP 4Caltech 5U.Chicago 6UW7IIAS-RCNP 8 U.Milano 9Brown U. 10Stanford11Irvine 12U. Zaragoza 13Alabama 14Duke U.

No scientific & basic discussions on data analysis and interpretationNo discussion of how a variation of the size of the chosen analysis

window would affect the significance of the hypothetical peak.

No relative peak strength analysis of all the 214Bi peaks in the region of interest.

There is no presentation of the entire spectrum to compare relative peak strengths

There are three unidentified peaks in the region of analysis that have great

significance than the 2039-keV peak. No discussion of the origin of these peaks.

No discussion of the relative peak strengths before and after the

single-site-event cut. This is needed to elucidate the peaks’origins

No simulation to demonstrate that the analysis correctly finds true peaks or that

it would find no peaks if none existed.

No discussion of how the conclusions depend on different mathematical models.

Previous data 2 of lower limit of 1.9 × 1025 y (90%) in conflict

with the “best value” of the new KDHK of 1.5 × 1025 y.This indicates

a dependence of the results on the analysis model and the BG evaluation.

SummarySummary1.A simple analysis of the 214Bi peaks demonstrates that thepeak finding procedure　used by KDHK produced spuriouspeaks near the ββ(0ν) endpoint.

2. The existence of these claimed peaks is crucial to the KDHK claim of a peak at 2039 keV interpreted as 0νββ.

3.All the peaks claimed in the 2000-2080 keV region may bespurious leaving the entire count rate due to an uniform BG.Alternatively, if all the peaks are real but unidentified, theputative 2039-keV feature may be simply another of thoseunidentified lines.4.These two examples emphasize the importance of addressing allthe items listed in the Introduction.

By failing to address these issues, the KDHK paperdoes not support its claim of evidence for ββ(0ν).

Unique features of MOON for Unique features of MOON for ββββ1. Large Q = 3.034 MeV leads to　 large rate 160 SNU for

<m> = 0.05 eV, 31/y/ton, The large 0νββ signal

well above RI BG .

2. Excited 0+ by γ−γ no 2νββ, RI.

3. ββ angular correlations to identify the mν term .

4. Localization in space and time leads to high selectivity of S with modest purity of b~mBq/t, ppt.

OtoOto Cosmo Observatory Cosmo Observatory

Lab.II Lab.INishitishinoOto

ToOsaka

ELEGANT VI Double beta

decays of 48Ca anddark matters

ELEGANT VDouble beta decaysof 100Mo and dark

matters

100 km south of Osaka, near Int. Airport

New Lab.

ELEGANT V (ELEGANT V (ELEELEctronctron GA GAmmamma NNeutrinoeutrino T Telescopeelescope))Electron and Electron and γγ detectors for detectors for ββ−νββ−ν and DMand DM

Lead and cupper shieldsNaI γ, β track

100MoPM

PL..

PM

EL-III. 76Ge ββGe crystal with NaI.

ΕL V forββ οf 100Μο,116Cd

β-ray energy and timeby plastic scintillators.

γ-ray by NaIDM –nucleus recoil

energy by NaI

EL.VI for 48Caββ andDM by 19F

CaF2 crystal array .

EL. V . left side shield is open.

H. Ejiri, et al.,NIM A302 1991 303

100100Mo Mo 0νββ0νββ by ELEGANT V by ELEGANT V

T0ν > 1.0 (0.55) 1023y 68(90)%CL BG 10-2/keV.kg.y

<mν> < 1.5 (2.1) eV

<gB> < 9 (11) 10-5

ELEGANT V / Oto Lab.

H.Ejiri, N.Kudomi, et al., Phys. Rev. C 63 ’01, 65501

NEMO

..

..

..

ELEGANT IV 48Ca ββ Large Q = 4.27 MeV small 0.187 % I. Ogawa Osaka

48Ca ββ < ~ 6 < ~ 6 eVeV

10-1

1

10

10 2

10 3

2000 3000 4000 5000Energy (keV)

coun

ts/2

0ke

V

C.L.) % (90year 108.1

C.L.) % (68year 106.822

2202/1

×>

×>νββT

V.V. Concluding Concluding RRemarksemarks

.

Concluding remarksConcluding remarks1. ββ is the realistic probe presently able to study a. Majorana ν : Lepton number ∆L=2. b. Absolute mass scale with <mν>=ΣmjcjU2

j in the 0.01~0.05 eV region of interest and CP phase.

2. Present detectors give mass limits of 0.3~1.5 eV, which are limited by sensitivities of 0.3-1 eV.

3. Interesting are future detectors with sensitivity of <mν> 0.01~0.06 eV to get the neutrinomasses, the mass spectrum and CP.

ReferencesReferencesDouble β decays. ELEGANT H.Ejiri, N.Kudomi, et al., Phys. Rev. C 63

2001,65501 Review H.Ejiri, Nucl. Phys.B 91 (2001) 255, ν 2000 proc.

Nuclear responses. Review. H.Ejiri, Phys. Rep. 338 (2000) 265.

MOON ββ and solar ν H.Ejiri,J.Engel, Hazama, P.Krastev, N.Kudomi, R.G.H. G. Robertson, Phys, Rev. Lett.,85 (2000) 2917 Supernova ν Η. Ejiri, J. Engel, and N. Kudomi, Phys. Lett.B, 02.