DOI 10.1393/ncc/i2019-19177-7
Colloquia: IFAE 2018
IL NUOVO CIMENTO 42 C (2019) 177
Resul s om he CUORE expe imen
A. Campani(1)(9),D.Q.Adams(2),C.Alduino(2),K.Al onso(3),
F. T. A ignone III(2), O. Azzolini(4),G.Ba i(5),F.Bellini(6)(7),
G. Bena o(8),A.Be sani(9),M.Biassoni(10), A. B anca(11)(12),
C. B o e io(10)(13), C. Bucci(14), A. Camina a(9), L. Canonica(14)(15),
X. G. Cao(16), S. Capelli(10)(13),L.Cappelli(8)(14)(17), L. Ca dani(7),
P. Ca ni i(10)(13),N.Casali(7), L. Cassina(10)(13),D.Chiesa(10)(13),
N. Cho (2), M. Clemenza(10)(13), S. Copello(14)(18),C.Cosmelli(6)(7),
O. C emonesi(10),R.J.C eswick(2),J.S.Cushman(19),A.D’Addabbo(14),
D. D’Aguanno(14)(20),I.Da inei(7),C.J.Da is(19), S. Dell’o o(21),
M. M. Deninno(5), S. Di Domizio(1)(9),V.Domp
`
e(14)(18),A.D obizhe (8)(17),
D. Q. Fang(16), M. Fa e zani(10)(13),E.Fe i(10)(13),F.Fe oni(6)(7),
E. Fio ini(10)(13),M.A.F anceschi(22),S.J.F eedman(8)(17),
B. K. Fujikawa(17),A.Giache o(10)(13), L. Gi oni(10)(13),A.Giuliani(23),
L. Glads one(15),P.Go la(14),C.Go i(10)(13),T.D.Gu ie ez(24),
K. Han(25),K.M.Heege (19), R. Hennings-Yeomansi(8)(17), R. G. Huang(8),
H. Z. Huang(3),J.Johns on(15), G. Keppel(4), Yu. G. Kolomensky(8)(17),
A. Lede (15),C.Ligi(22),Y.G.Ma(16),L.Ma ini(8)(17), M. Ma inez(6)(7)(26),
R. H. Ma uyama(19),Y.Mei(17),N.Moggi(5)(27), S. Mo gan i(7),
S. S. Nago ny(14)(18), T. Napoli ano(22), M. Nas asi(10)(13),C.Nones(28),
E. B. No man(29)(30),V.No a i(23), A. Nuccio i(10)(13),I.Nu ini(14)(18),
T. O’Donnell(21),J.L.Ouelle (15),C.E.Paglia one(14)(20),
M. Palla icini(1)(9),V.Palmie i(4),L.Pa a ina(14), M. Pa an(10)(13),
G. Pessina(10),C.Pi a(4),S.Pozzi(10)(13),E.P e i ali(10),A.Puiu(10)(13),
F. Reindl(7),C.Rosen eld(2),C.Rusconi(2)(14), M. Sakai(3),
S. Sangio gio(29),D.San one(14)(31),B.Schmid (17),N.D.Scielzo(29),
V. Singh(8),M.Sis i(9)(13), D. Spelle (19), L. Ta a ello(11),
F. Te ano a(9)(13),C.Tomei(7),M.Vigna i(7), S. L. Wagaa achchi(8)(17),
B. S. Wang(29)(30), H. W. Wang(16), B. Welli e (17),J.Wilson(2),
K. Wilson(2),L.A.Winslow(15),T.Wise(19)(32), L. Zano i(10)(13),
G. Q. Zhang(16), S. Zimme mann(33)andS. Zucchelli(5)(27)
(1)Dipa imen o di Fisica, Uni e si `a di Geno a - Geno a I-16146, I aly
(2)Depa men o Physics and As onomy, Uni e si y o Sou h Ca olina
Columbia, SC 29208, USA
(3)Depa men o Physics and As onomy, Uni e si y o Cali o nia
Los Angeles, CA 90095, USA
(4)INFN, Labo a o i Nazionali di Legna o - Legna o (Pado a) I-35020, I aly
(5)INFN, Sezione di Bologna - Bologna I-40127, I aly
(6)Dipa imen o di Fisica, Sapienza Uni e si `a di Roma - Roma I-00185, I aly
(7)INFN, Sezione di Roma - Roma I-00185, I aly
(8)Depa men o Physics, Uni e si y o Cali o nia - Be keley, CA 94720, USA
(9)INFN, Sezione di Geno a - Geno a I-16146, I aly
(10)INFN, Sezione di Milano Bicocca - Milano I-20126, I aly
(11)INFN, Sezione di Pado a - Pado a I-35131, I aly
(12)Dipa imen o di Fisica e As onomia, Uni e si `a di Pado a - I-35131 Pado a, I aly
(13)Dipa imen o di Fisica, Uni e si `a di Milano-Bicocca - Milano I-20126, I aly
C ea i e Commons A ibu ion 4.0 License (h p://c ea i ecommons.o g/licenses/by/4.0) 1
2A. CAMPANI e al.
(14)INFN, Labo a o i Nazionali del G an Sasso - Asse gi (L’Aquila) I-67100, I aly
(15)Massachuse s Ins i u e o Technology - Camb idge, MA 02139, USA
(16)Shanghai Ins i u e o Applied Physics, Chinese Academy o Sciences
Shanghai 201800, China
(17)Nuclea Science Di ision, Law ence Be keley Na ional Labo a o y
Be keley, CA 94720, USA
(18)INFN, G an Sasso Science Ins i u e - L’Aquila I-67100, I aly
(19)W igh Labo a o y, Depa men o Physics, Yale Uni e si y - New Ha en,
CT 06520, USA
(20)Dipa imen o di Ingegne ia Ci ile e Meccanica, Uni e si `a degli S udi di Cassino e del
Lazio Me idionale - Cassino I-03043, I aly
(21)Cen e o Neu ino Physics, Vi ginia Poly echnic Ins i u e and S a e Uni e si y
Blacksbu g, VA 24061, USA
(22)INFN, Labo a o i Nazionali di F asca i - F asca i (Roma) I-00044, I aly
(23)CSNSM, Uni . Pa is-Sud, CNRS/IN2P3, Uni e si ´e Pa is-Saclay - F-91405 O say,
F ance
(24)Physics Depa men , Cali o nia Poly echnic S a e Uni e si y
San Luis Obispo, CA 93407, USA
(25)INPAC and School o Physics and As onomy, Shanghai Jiao Tong Uni e si y; Shanghai
Labo a o y o Pa icle Physics and Cosmology - Shanghai 200240, China
(26)Labo a o io de Fisica Nuclea y As opa iculas, Uni e sidad de Za agoza
Za agoza 50009, Spain
(27)Dipa imen o di Fisica e As onomia, Alma Ma e S udio um, Uni e si `adiBologna
Bologna I-40127, I aly
(28)Se ice de Physique des Pa icules, CEA/Saclay - F-91191 Gi -su -Y e e, F ance
(29)Law ence Li e mo e Na ional Labo a o y - Li e mo e, CA 94550, USA
(30)Depa men o Nuclea Enginee ing, Uni e si y o Cali o nia - Be keley, CA 94720, USA
(31)Dipa imen o di Scienze Fisiche e Chimiche, Uni e si `a dell’Aquila
L’Aquila I-67100, I aly
(32)Depa men o Physics, Uni e si y o Wisconsin - Madison, WI 53706, USA
(33)Enginee ing Di ision, Law ence Be keley Na ional Labo a o y - Be keley, CA 94720, USA
ecei ed 31 Janua y 2019
Summa y. — Neu inoless double be a decay (0νββ) is a a e, second-o de nuclea
ansi ion ha occu s only i neu inos a e massi e Majo ana pa icles o h ough
new physics beyond S anda d Model. This p ocess explici ly iola es he lep on
numbe (L) by wo uni s and, he e o e, he obse a ion o 0νββ would demon-
s a e ha Lis no a symme y o na u e. Combined wi h fla ou mixing and
cosmological measu emen s, i can p o ide unique con ain s on neu ino mass scale
and es ablish whe he neu inos a e Di ac o Majo ana pa icles. The C yogenic
Unde g ound Obse a o y o Ra e E en s (CUORE) is an expe imen loca ed a
he LNGS sea ching o 0νββ decay o 130 Te. CUORE exploi s he bolome ic ech-
nique o each high esolu ion a ound he Q- alue (2527.5 keV). I consis s o an
a ay o 988 na u al TeO2cubic c ys als g ouped in o 19 owe s. Wi h a o al ac i e
mass o 742 kg (∼206 kg o 130Te), CUORE is ope a ed a e y low empe a u e wi h
anew3He/4He e ige a o . Da a aking s a ed a he beginning o 2017. A e a
b ie in oduc ion on he de ec o and he way da a analysis is pe o med, I desc ibe
CUORE fi s esul s o he sea ch o he 0νββ decay ha we e published in Ma ch
2018.
RESULTS FROM THE CUORE EXPERIMENT 3
Fig. 1. – Rende ing o he CUORE c yos a .
1. – In oduc ion
Neu inoless double be a decay ep esen s one o he mos powe ul ways o p obe
expe imen ally he exis ence o lep on fla ou iola ion and de e mine missing neu ino
p ope ies. The decay a e can be exp essed as Γ0νββ =G0ν|M0ν|2mββ
me, whe e mββ is
|i=1,2,3U2
ei mi|i he 0νββ decay is media ed by ligh Majo ana neu ino exchange.
A measu emen o he decay a e gi es he possibili y o cons ain he alue o he
effec i e Majo ana mass. I i occu s, he 0νββ decay will ha e a obus expe imen al
signa u e: a sha p peak a he Q- alue o he decay in he summed ene gy spec um
o he final s a e elec ons. To maximize he sensi i i y [1] an expe imen mus ha e a
la ge sou ce mass (in CUORE ∼742 kg), a e y low back ound a e nea Qββ (ou goal
is 0.01 coun s/keV/kg/y ) and a good ene gy esolu ion (CUORE aims a 5 keV). Also
he choice o he iso ope has a s ong impac : among candida es o 0νββ,130Te has he
highes na u al abundance (34.17%) and la ge Qββ o (2527.515 ±0.013) keV.
The C yogenic Unde g ound Obse a o y o Ra e E en s (CUORE) [2] applies he
inno a i e bolome ic echnique a an unp eceden scale o he sea ch o he 0νββ decay
o ellu ium iso opes. Loca ed a he Labo a o i Nazionali del G an Sasso, CUORE
is composed o a segmen ed a ay o 988 TeO2de ec o s a anged in o 19 owe s and
ope a ed a ex emely low empe a u es. The o al ac i e mass o 742 kg, 130Te is 206 kg.
2. – CUORE de ec o
A bolome e is a sensi i e calo ime e ha measu es he ene gy deposi ed a e a
pa icle in e ac ion hanks o he inc ease in he base empe a u e o he medium. Each
bolome e in CUORE has h ee p ima y componen s: an ene gy abso be ( he c ys al
i sel ), a empe a u e senso (a neu on- ansmu a ion–doped ge manium he mis o ),
ha con e s he empe a u e ise in o a ol age pulse, and a weak he mal link o he
coppe ame ha ac s bo h as he s uc u al suppo and he he mal ba h o es o e
he e e ence empe a u e. Measu ing he signal ampli ude we can find he amoun o
ene gy eleased in he p ocess. A he ope a ing empe a u e o 10 mK, he ypical hea
capaci y co esponds o ΔT/ΔE∼100 μK/MeV and a ol age inc ease o ∼1V.
CUORE owe s a e a anged in a close-packed a ay and he mally connec ed o he
mixing chambe o a 3He/4He e ige a o [3] as shown in fig. 1. P ecooling o main-
ain he dilu ion cycle is ealized by fi e wo-s age (∼40 K and ∼4 K) pulse ube c y-
ocoole s, whe eas he base empe a u e is eached h ough he 3He/4He mix u e. The
4A. CAMPANI e al.
ope a ing empe a u e is a comp omise be ween maximizing he mal gain and op imiz-
ing he signal bandwid h. The dimensions, expe imen al olume and mass (∼1m
3and
∼15 ons, espec i ely), make CUORE c yos a he la ges and mos powe ul c yogen-
ee dilu ion c yos a in ope a ion. I s ealiza ion ollowed s ic expe imen al equi e-
men s, such as mechanical insula ion and ex emely low le els o adioac i i y o he
ma e ials used. In o de o supp ess ex e nal γ- ay backg ound, neu ons and en i-
onmen al con ibu ions wo lead shields a e in eg a ed in o he c yogenic olume and
wo ex e nal shields su ound he de ec o . Thanks o he analysis o CUORE-0 [4]
da a and he adio assay o he ma e ials used o CUORE de ec o , i was possi-
ble o iden i y he main backg ound sou ces [5] in he egion o in e es and o make
a Mon e Ca lo simula ion o find an es ima e o he backg ound index. Alpha de-
cays om he su ace o he coppe ame gi e he main con ibu ion, he o al B.I.
is [1.00 ±0.03 (s a .)+0.23
−0.10 (sys .)]10−2coun s/keV/kg/y .
3. – Analysis echniques and fi s CUORE esul s
The fi s esul on 0νββ o 130Te was ob ained wi h wo da ase s, he fi s including
May and June acquisi ion, he las made o Augus and Sep embe da a. Bo h da ase s
include ini ial and final calib a ion phases, used o iden i y he de ec o esponse o
signals o known ene gy and o check i i is s able o e he pe iod conside ed. We use
da a collec ed be ween calib a ions o he 0νββ decay sea ch. A single e en is made o
a 10 s window (3 s be o e and 7 a e he igge ): he p e igge gi es a measu emen o
he bolome e empe a u e be o e he in e ac ion. We also analyze wa e o ms ha do
no con ain isible pulses o moni o and model ou de ec o noise beha iou .
A o al o 984 o 988 channels a e wo king p ope ly and we ound an o e all a e age
e en a e o ∼50 mHz in calib a ion da a and ∼6 mHz in physics da a. The exposu e
o he wo da ase is 86.3 kg ·y o TeO2and 24.0 kg ·y o 130Te. Da a analysis
p oceeds h ough se e al s eps. Fi s , he ampli ude o each pulse is es ima ed, by means
o a fil e ha maximizes he SNR. The signal ampli ude is s abilized agains he mal
d i s and calib a ion coefficien s a e de e mined using 6 γlines om 232Th. Then da a
a e blinded: we p oduce an a ificial peak a Qββ and he fi p ocedu e o measu e
Γ0νββ is fixed wi hou knowing he eal spec um in he ROI. As we expec any 0νββ
decay e en o elease he whole ene gy in he same c ys al in which i ook place (88%
p obabili y), we emo e all e en s ha occu ed in diffe en bolome e s wi hin 10 ms.
The de ec o esponse unc ion is de e mined using high s a is ics 208Tl 2615 keV γline
om calib a ion da a and includes h ee Gaussian componen s. The ene ge ic esolu ion
(FWHM) is (8.3±0.4) keV o he fi s da ase and (7.4±0.7) keV o he second one.
Fig. 2. – Ene gy spec a o phsyics (blue) and calib a ion ( ed) da a. The calib a ion spec um
is no malized o he physics da a a he 2615 keV line. Figu e aken om e . [6].
RESULTS FROM THE CUORE EXPERIMENT 5
Fig. 3. – Bo om: bes -fi model (solid blue line) o e laid on he spec um o 0νββ decay
candida es. The e ical band is cen e ed a Qββ. Top: no malized esiduals. Figu e aken
om e . [6].
Calib a ion and unblinded phsysics spec a a e shown in fig. 2. The fi model o he ROI
(2465–2575 keV) includes he 0νββ decay peak, a peak o he 60Co coinciden gamma
ays (1173 and 1332 keV) and a fla backg ound. The obse ed backg ound index in
he ROI is (0.014 ±0.002) coun s/keV/kg/y , in line wi h ou expec a ions. The 155
candida e e en s oge he wi h he esul o he fi a e shown in fig. 3.
The bes fi Γ0νββ is (−1.0+0.4
−0.3(s a .) ±0.1 (sys .)) 10−25 y −1. We conclude ha
he e is no e idence o he 0νββ decay and se a limi on he 130Te hal -li e τ0ν
1/2>
1.3·1025 y (90% C.L.) [6]. Combining he fi s CUORE esul wi h he es ima es
ob ained om i s wo p edecesso s, CUORE-0 and Cuo icino, we place he mos s ingen
limi o da e on he hal -li e o 130Te o he 0νββ decay: τ0ν
1/2>1.5·1025 y (90% C.L.).
In e p e ing his esul in he amewo k in which 0νββ is media ed by ligh Majo ana
neu ino exchange, we can ansla e i in o a limi on he effec i e Majo ana mass:
mββ <(140–400) meV.
In conclusion, CUORE is he fi s on-scale c yogenic de ec o o he sea ch o
0νββ. The success ul ope a ion pa es he way o he use o la ge-mass bolome e a ays
o a e-e en sea ches. E en i u he op imiza ion is needed, he esul s we gained wi h
wo da ase s show ha ou pu poses a e wi hin he each o 5 yea s da a aking.
REFERENCES
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[2] A usa D. R., A ignone F. T. III, Azzolini O. e al.,Ad . High Ene gy Phys.,2015
(2015) 879871.
[3] Ligi C. e al.,J. Low Temp. Phys.,184 (2016) 190.
[4] CUORE Collabo a ion (Al onso K. e al.),Phys. Re . Le .,115 (2015) 10.
[5] Alduino C., Al onso K., A usa D. R. e al.,Eu . Phys. J. C,77 (2017) 543.
[6] CUORE Collabo a ion (Alduino C. e al.),Phys. Re . Le .,120 (2018) 13.