We propose to test for short baseline neutrino oscillations, implied by the
recent reevaluation of the reactor antineutrino flux and by anomalous results
from the gallium solar neutrino detectors. The test will consist of producing a
75 kCi 144Ce - 144Pr antineutrino source to be deployed in the Kamioka Liquid
Scintillator Anti-Neutrino Detector (KamLAND). KamLAND's 13m diameter target
volume provides a suitable environment to measure energy and position
dependence of the detected neutrino flux. A characteristic oscillation pattern
would be visible for a baseline of about 10 m or less, providing a very clean
signal of neutrino disappearance into a yet-unknown, "sterile" state. Such a
measurement will be free of any reactor-related uncertainties. After 1.5 years
of data taking the Reactor Antineutrino Anomaly parameter space will be tested
at > 95% C.L.Comment: White paper prepared for Snowmass-2013; slightly different author
  lis

Banks, T.

Berger, B. E.

Cribier, M.

Decowski, P.

Detwiler, J. A.

Durero, M.

Dwyer, D.

Efremenko, Y.

Enomoto, S.

Fischer, V.

Fujikawa, B. K.

Gaffiot, J.

Gando, A.

Gando, Y.

Gelis, V. M.

Hayashida, S.

Ikeda, H.

Inoue, K.

Ishidoshiro, K.

Ishikawa, H.

Karwowski, H. J.

Koga, M.

Kolomensky, Yu. G.

Kornoukhov, V. N.

Kozlov, A.

Lasserre, T.

Learned, J. G.

Letourneau, A.

Lhuillier, D.

Maricic, J.

Markoff, D. M.

Matsuda, R.

Matsuda, S.

Matsuno, S.

Mention, G.

Milincic, R.

Mitsui, T.

Motoki, D.

Nakamura, K.

ODonnell, T.

Oki, Y.

Otani, M.

Saldikov, I. S.

Scola, L.

Shimizu, I.

Shirai, J.

Suekane, F.

Suzuki, A.

Takemoto, Y.

Tamae, K.

Tikhomirov, G. V.

Ueshima, K.

Veyssiere, Ch.

Vivier, M.

Watanabe, H.

Xu, B. D.

Yamada, S.

Yamauchi, Y.

Yoshida, H.

Yoshida, S.

English

arXiv

We propose to test for short baseline neutrino oscillations, implied by the
recent reevaluation of the reactor antineutrino flux and by anomalous results
from the gallium solar neutrino detectors. The test will consist of producing a
75 kCi 144Ce - 144Pr antineutrino source to be deployed in the Kamioka Liquid
Scintillator Anti-Neutrino Detector (KamLAND). KamLAND's 13m diameter target
volume provides a suitable environment to measure energy and position
dependence of the detected neutrino flux. A characteristic oscillation pattern
would be visible for a baseline of about 10 m or less, providing a very clean
signal of neutrino disappearance into a yet-unknown, "sterile" state. Such a
measurement will be free of any reactor-related uncertainties. After 1.5 years
of data taking the Reactor Antineutrino Anomaly parameter space will be tested
at &gt; 95% C.L

Gando, A

Gando, Y

Hayashida, S

Ikeda, H

Inoue, K

Ishidoshiro, K

Ishikawa, H

Koga, M

Matsuda, R

Matsuda, S

Mitsui, T

Motoki, D

Nakamura, K

Oki, Y

Otani, M

Shimizu, I

Shirai, J

Suekane, F

Suzuki, A

Takemoto, Y

Tamae, K

Ueshima, K

Watanabe, H

Xu, BD

Yamada, S

Yamauchi, Y

Yoshida, H

Banks, T

Berger, BE

Cribier, M

Decowski, P

Detwiler, JA

Durero, M

Dwyer, D

Efremenko, Y

Enomoto, S

Fischer, V

Fujikawa, BK

Gaffiot, J

Gelis, VM

Karwowski, HJ

Kolomensky, Yu G

Kozlov, A

Kornoukhov, VN

Lasserre, T

Learned, JG

Letourneau, A

Lhuillier, D

Maricic, J

Markoff, DM

Matsuno, S

Mention, G

Milincic, R

ODonnell, T

Saldikov, IS

Scola, L

Tikhomirov, GV

Veyssiere, Ch

Vivier, M

Yoshida, S

eScholarship - University of California

UC BerkeleyUC Berkeley Previously Published WorksTitleWhite paper: CeLAND - Investigation of the reactor antineutrino anomaly with an intense 144Ce-144Pr antineutrino source in KamLANDPermalinkhttps://escholarship.org/uc/item/1jz5v143AuthorsGando, AGando, YHayashida, Set al.Publication Date2013-09-26 Peer reviewedeScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaWhite paper:CeLAND - Investigation of the reactor antineutrino anomaly withan intense 144Ce - 144Pr antineutrino source in KamLANDA. Gando, Y. Gando, S. Hayashida, H. Ikeda, K. Inoue, K. Ishidoshiro, H. Ishikawa, M.Koga, R. Matsuda, S. Matsuda, T. Mitsui,D. Motoki, K. Nakamura, Y. Oki, M. Otani, I.Shimizu, J. Shirai, F. Suekane, A. Suzuki, Y. Takemoto, K. Tamae, K. Ueshima, H.Watanabe, B.D. Xu, S. Yamada,Y. Yamauchi, H. YoshidaResearch Center for Neutrino Science, Tohoku University, Sendai 980-8578, JapanB. E. BergerColorado State University, Fort Collins, CO 80523-1875, USAM. Cribier1, 2, M. Durero1, V. Fischer1, J. Gaffiot2, T. Lasserre1,2, A. Letourneau1, D.Lhuillier1, G. Mention1, L. Scola1, Ch. Veyssire1 and M. Vivier11Commissariat lnergie atomique et aux nergies alternatives, Centre de Saclay, IRFU,91191 Gif-sur-Yvette, France2Astroparticules et Cosmologie APC, 10 rue Alice Domon et Lonie Duquet, 75205 Pariscedex 13, FranceA. KozlovKavli Institute for the Physics and Mathematics of the Universe (WPI), University ofTokyo, Kashiwa 277-8583, JapanT. Banks2, D. Dwyer1, B. K. Fujikawa1, Yu. G. Kolomensky1,2, T. ODonnell2 1LawrenceBerkeley National Laboratory, Berkeley, CA 94720, USA2University of California, Berkeley, CA 94704, USAPatrick DecowskiNikhef and the University of Amsterdam, Science Park 105 1098 XG, Amsterdam, theNetherlandsD. M. MarkoffNorth Carolina Central University, Durham, NC 27707, USAS. YoshidaGraduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, JapanV.N. Kornoukhov1, T. V.M. Gelis3, G.V. Tikhomirov2, I.S. Saldikov2 1 Russian FederationState Scientific Center of Theoretical and Experimental Physics Institute, 117218 Moscow,Russia2Scientific and Research Nuclear University, Moscow engineering and Physics Institute,Russia3 Russian Academy of Sciences A.N. Frumkin Institute of Physical chemistry andElectrochemistry, RussiaJ. G. Learned, J. Maricic, S. Matsuno, R. MilincicUniversity of Hawaii at Manoa, Honolulu, HI 96822, USA1arXiv:1309.6805v2  [hep-ex]  12 Oct 2013H. J. KarwowskiUniversity of North Carolina, Chapel Hill, NC 27599, USAY. EfremenkoUniversity of Tennessee, Knoxville, TN 37996, USAJ. A. Detwiler, S. EnomotoUniversity of Washington, Seattle, WA 98195, USAAbstractWe propose to test for short baseline neutrino oscillations, implied by the recentreevaluation of the reactor antineutrino flux and by anomalous results from the galliumsolar neutrino detectors. The test will consist of producing a 75 kCi 144Ce - 144Prantineutrino source to be deployed in the Kamioka Liquid Scintillator Anti-NeutrinoDetector (KamLAND). KamLANDs 13 m diameter target volume provides a suitableenvironment to measure energy and position dependence of the detected neutrino flux.A characteristic oscillation pattern would be visible for a baseline of about 10 m orless, providing a very clean signal of neutrino disappearance into a yet-unknown, sterilestate. Such a measurement will be free of any reactor-related uncertainties. After 1.5years of data taking the Reactor Antineutrino Anomaly parameter space will be testedat > 95% C.L.1 IntroductionAn intriguing, nearly 3σ indication of neutrino disappearance at baselines of less than100 m has been recently revealed [1], as can be seen in Figure 1. The indication ap-peared as a result of reanalysis of the global reactor antineutrino experimental datausing the updated calculation of the reactor neutrino flux. A possible physical explana-tion for this effect, commonly called the Reactor Antineutrino Anomaly (RAA), may bethe existence of yet-undiscovered mixing between the electron antineutrino and a new,4th neutrino flavor that is “sterile”, i.e., does not interact through the Standard Modelweak interactions. To be compatible with the observed deficit, this sterile neutrinowould need to have a mass splitting |∆m2new| ≥ 0.1 eV2. The RAA, in combinationwith further complementary hints from gallium solar neutrino experiments [2], as wellas the LSND and MiniBooNE experiments [3], create a compelling case to search fora sterile (4th) neutrino flavor and measure its mass. If detected, the presence of a 4th-generation sterile neutrino would impact the extraction of the neutrino mixing angleθ13 from the reactor neutrino data, as well as future measurements of the CP-violatingphase in the leptonic sector.2 Testing the Reactor Antineutrino AnomalyA decisive test for the existence of the fourth neutrino flavor, as indicated by theRAA and gallium anomaly, can be achieved with an intense radioactive neutrino orantineutrino source deployed near a massive liquid scintillator detector. For neutrinos,monochromatic neutrino sources such as 51Cr or 37Ar can be used: the neutrino detec-tion is realized through neutrino-electron scattering (ν + e−). Such measurements are2[]Figure 1: Graph showing the ratio of the observed to the expected rate, from the recent re-actor neutrino flux calculations without neutrino oscillations, for all reactor neutrino exper-iments at various baselines. The dashed line corresponds to the classic 3 neutrino oscillationscenario, while the solid line corresponds to the 3+1 model (3 active neutrinos + 1 sterileneutrino).quite challenging. In addition to the small ν + e− cross-section, there are numerousbackgrounds to this method including solar neutrinos and the decays of natural or cos-mogenically induced radioactivity. To overcome these challenges, radioactive sourcesof 10 MCi or more are needed. The antineutrino sources benefit from the inverse betadecay (IBD) reaction with the characteristic prompt e+ annihilation, followed by de-layed neutron capture: such delayed-coincidence signature is an effective backgroundsuppression tool. We intend to use a 75 kCi 144Ce - 144Pr antineutrino source thatproduces two consecutive beta decays. The 144Ce - 144Pr antineutrino generator wasfirst proposed in 2011 [4]. 144Ce, which has a half-life of 285 days, β− decays into a144Pr daughter, which subsequently β− decays to the stable 144Nd with a Q-value of2.996 MeV. A simplified decay scheme is shown in Figure 2. The 144Pr decay producesantineutrinos with energy above the inverse beta decay threshold of 1.8 MeV. Giventhe short half-life of 144Pr (17.3 minutes), the 144Pr is always in equilibrium with 144Ceand the antineutrino flux depends solely on the decay rate of 144Ce. The 144Ce source,in the form of CeO2, will be produced at the Mayak reprocessing plant in Russia from2-3 year old spent nuclear fuel. The 144Ce fraction in CeO2 is 0.5% three years afterthe last irradiation of the fuel inside the reactor core.The fourth neutrino flavor will reveal itself in the oscillatory pattern of the distance-dependent flux from a pure antineutrino source. The oscillation length should beapproximately matched by the source-detector distance. Based on the implications ofRAA, the best fit for the |∆m2new| ∼ 1 eV2 corresponds to the oscillatory length of3Figure 2: 144Ce beta decays slowly with emission of low energy antineutrino below theIBD threshold. This decay is almost immediately followed by the beta decay of 144Pr withemission of antineutrino of energy up to 2.996 MeV. Antineutrinos in the high energy end of144Pr decay spectrum, with energy above 1.8 MeV, can engage in IBD in LS. The dominantbackground is 2.185 MeV gamma produced with a branching fraction of 0.7%.roughly 1 meter.There are three candidate detectors in the world that are well suited for this source-based search for sterile neutrinos: KamLAND, SNO+, and Borexino. This project,dubbed CeLAND, proposes to deploy a 75 kCi 144Ce source into KamLAND [5]. Kam-LAND is a 1 kton liquid scintillator detector that has been in operation since 2002.The target liquid scintillator is contained in the 13 m diameter balloon. The compact-ness of the source (∼20 g and 13 cm in diameter and height), combined with possible3-16 m long baselines, as well as the good energy and vertex position resolution ofKamLAND, will provide a distance- and energy-dependent oscillation signature. Inthe proposed configuration, CeLAND will provide a definitive test of the existence ofthe fourth neutrino.The 144Ce source will be placed in the KamLAND Outer Detector (OD) region,close to the outside surface of the stainless steel sphere that encloses the KamLANDInner Detector (ID), at the approximate distance of 9.5 m from the detector center.The source with the shielding will be placed in a cylindrical structure vessel called thesock, supported from the top of the OD. Figure 3 shows approximate location of thesource inside the KamLAND OD detector. Figure 4 shows preliminary sock designthat will hold the source. The deployment in the OD will probe baseline range from3 m (closest part of the target LS filled balloon) up to 16 m (the opposite side of thetarget LS filled balloon), expanding the sterile neutrino mixing parameter space thatcan be probed. Deployment in the OD will enable CeLAND to run in parallel with4KamLAND-Zen (the 136Xe ββ0ν search [6]). In this configuration, CeLAND will beable to probe the RAA parameter space with > 95% C.L. The 144Ce source run in theOD will last 1.5 years.Figure 3: Schematic representation of the KamLAND detector and approximate location ofthe cerium source inside the OD. The location is easily accessible through a wide hatch onthe top of the OD.Design and construction of adequate tungsten shielding for a 75 kCi radioactivesource will be essential to background reduction as well as for safe transport fromMayak in Russia to Kamioka mine in Japan. Various transport scenarios are underinvestigation. The shielding serves a dual purpose: reduce the radiation from the 144Cesource to the safe level for transportation, handling, and human presence; and suppressbeta and gamma backgrounds in the target LS during the source run in KamLAND.The deployment in the OD takes additional advantage of shielding from 11.5 mm thickwall of stainless steel that encloses the ID. The 2.5 m thick layer of mineral oil insidethe ID that surrounds the balloon containing target LS, provides further shieldingfrom the 144Ce source beta and gamma emissions. In addition, shielding made of adense tungsten alloy will be designed for biological protection and suppression of the144Pr 2.185 MeV gamma radiation that is a dangerous background for neutron captureon hydrogen. Preliminary estimates show that 16 cm thick tungsten shield will besufficient to provide both biological protection and background suppression.Precise determination of the absolute activity of a 75 kCi radioactive source at 1-1.5% level as in [2] will further enhance the sensitivity of the measurement. A calorime-ter will be built in order to measure the absolute activity of the source.5Figure 4: The preliminary sock design to contain the cerium source with shielding insideKamLAND OD. The source will be located at the bottom of the cylindrical sock, at approx-imate distance of 9.5 m from the detector center.3 Sensitivity and prospectsIn one and half year of data taking CeLAND will probe the majority of the phase spacecovered by the RAA at > 95% C.L. Figure 5 shows the sensitivity to short baselineoscillations after 6 and 18 months of data taking in the OD. While the shape onlyanalysis can probe the region where the current best fit solution is located, inclusionof the rate analysis, (assuming 1.5% absolute source activity uncertainty) significantlyincreases the coverage of the region of interest, indicated by the RAA. Even with just6 months of data, significant limit in the area of interest can be placed.At the end of the 144Ce source run in the OD after 18 months, the sensitivity in-creases significantly as can be seen in the Figure 5. 95% C.L. non-oscillation hypothesisexclusion is achieved for the mixing angles as low as sin2 2θnew ∼ 0.05 in the regionof interest and for high values of ∆m2new. Excellent sensitivity to the parameter spacewith small ∆m2new ∼ 0.1 eV2 is achieved due to relatively long baseline applied. It isevident from the plots that the accurate measurement of the absolute activity of the144Ce source is essential.Thanks to the energy and vertex information of the 144Ce - 144Pr antineutrinospectrum, and KamLANDs large size, CeLAND has an excellent sensitivity comparedto other similar proposed experiments [7], as can be seen in Figure 6.The CeLAND experiment provides an effective, fast, and inexpensive way to searchfor sterile neutrinos at the short baseline, covering the RAA phase space completely atthe 95% C.L. It is complementary to proposed searches with reactor- and accelerator-produced neutrinos. If CeLAND demonstrates the existence of sterile neutrinos, itwould be one of the most significant discoveries of physics beyond the Standard Model.The measurement could also potentially influence the precision determination of θ13,and consequently impact prospects for the measurement of CP-violation in the lepton6Figure 5: Sensitivity of the measurement to exclude the non-oscillation after (left) 6 monthsand (right) 18 months of data taking in the KamLAND OD is shown. 75 kCi 144Ce source,located 9.5 m from the detector center is assumed. Statistical sample with fiducial volumecut at 6 m radius is used. The light and dark gray area show 90% C.L. and 95% C.L. limitsof RAA. The dashed line corresponds to the 95% C.L. non-oscillation exclusion with energyspectrum shape analysis only. The solid line corresponds to the 95% C.L. non-oscillationhypothesis exclusion with both absolute event rate and event energy spectrum shape analysis.The inclusion of the rate information significantly improves the sensitivity, in particular inthe large ∆m2new region.Figure 6: Sensitivity limits of several proposed source experiments. CeLANDs combinedshape and rate sensitivity exceeds other similar proposed experiments [7].sector. A null measurement will definitively put to rest sterile neutrino interpretationsof the existing neutrino anomalies.7References[1] G. Mention, M. Fechner, Th. Lasserre, Th. A. Mueller, D. Lhuillier, M. Cribier,A. Letourneau, Phys.Rev.D83:073006 (2011)[2] P. Anselmann et al. (GALLEX), Phys. Lett. B342, 440 (1995); W. Hampel et al.(GALLEX), Phys. Lett. B420, 114 (1998); F. Kaether et al. Phys. Lett. B685, 47(2010); J. N. Abdurashitov et al. (SAGE), Phys. Rev. Lett. 77, 4708 (1996); J. N.Abdurashitov et al. (SAGE), Phys. Rev. C59, 2246 (1999); J. N. Abdurashitovet al., Phys. Rev. C73, 045805 (2006); J. N. Abdurashitov et al. (SAGE), Phys.Rev. C80, 015807 (2009).[3] A. A. Aguilar-Arevalo et al., Phys. Rev. Lett. 98 (2007) 231801.; A. A. Aguilar-Arevalo et al., Phys. Rev. Lett. 102 (2009) 101802[4] M. Cribier, M. Fechner, Th. Lasserre et al., ArXiv: 1107.2335, Phys. Rev. Lett.107, 201801 (2011)[5] KamLAND Collaboration, Phys. Rev. Lett. 100, 221803 (2008)[6] KamLAND-Zen Collaboration, Phys. Rev. Lett. 110, 062502 (2013)[7] T. Lasserre, arXiv:1209.5090, Nucl. Phys. B Proc. Suppl. 00 (2012) 168

White paper: CeLAND - Investigation of the reactor antineutrino anomaly with an intense 144Ce-144Pr antineutrino source in KamLAND

White paper: CeLAND - Investigation of the reactor antineutrino anomaly
  with an intense 144Ce-144Pr antineutrino source in KamLAND

White paper: CeLAND - Investigation of the reactor antineutrino anomaly with an intense 144Ce-144Pr antineutrino source in KamLAND

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