PoS(ICHEP2018)114 https://pos.sissa.it/ ∗† [email protected] Speaker. on behalf of the TEXONO Collaboration The existence of physics beyond the standardobservation model of has been neutrino concretely flavor established based oscillationsintrinsic on and the properties, it including has the absolute open mass, manyhierarchy Majorana questions of or about the Dirac the neutrino. and neutrino’s diverse Germanium the applications relative (Ge) mass in ionization fundamental detectors research withONO are their Collaboration novel unique has candidates been features for pursuing and such theand a research light search. program on WIMP The low Dark TEX- energy Matter neutrinotory with interactions (KSNL) Ge-ionization in detectors Taiwan and at in thepresent the highlights Kuo-Sheng China the Neutrino Jinping potentials of Underground Labora- Ge-detectors Laboratory for (CJPL)interactions, the in light studies WIMP, China. of sterile active magnetic We neutrino moment electromagnetic and neutrino-nucleus coherent scattering. † ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). The 39th International Conference on High4-11 Energy July, Physics 2018 (ICHEP2018) Seoul, Korea Institute of Physics, Academia Sinica, TaipeiE-mail: 11529, Taiwan Lakhwinder Singh Test of Beyond-Standard-Model Scenarios with Low Threshold Germanium Detectors PoS(ICHEP2018)114 B µ 10 − 10 × 2.6 Lakhwinder Singh < ν µ and at 90% CL is derived from nucleus coherent scattering 12 B − − µ 11 10 many-body theory also provides − × 10 × initio ] at low energy regime due to 1/T and 2.1 - 6 [ < ab 7.4 ν ν q < q ν µ 1 ] with their low intrinsic radioactivity background, 1 e) scattering is a most sensitive process to study neutrino are limited due to low statistics and high background in sub- − ν ν µ and ]. The upper limits of 7 ν q ] and neutrino milli-charge 5 [ ν 80 eV [ µ ]. 4 ≥ , 3 induce differential cross sections. This , ν 2 q and ν The electromagnetic properties of neutrino is an interesting venue to look for new physics The elastic neutrino-electron ( The standard model (SM) of particle physics describes the all known particles and their inter- Germanium (Ge) ionization detectors [ It is now well established that about one-quarter of the energy density in the Universe is com- -dependence of the differential rate, respectively. When energy transfer in neutrino scattering µ 2 starts to overlap with atomic scales,adopted atomic the effects Multi-Configuration play significant Relativistic rolesthe Random-Phase to Approximation the cross theory, sections. to We calculate 1/T the better description for theat structure photon of Ge energy atoms asare well derived as using photo-absorption PCGe (point data contact ofC.L. Ge-detector) Ge The 124.2(70.3) crystal upper kg-days bounds of ON on (OFF)keV data region. at Our 90% best experimental upper bounds beyond the SM. The massive neutrinosdipole acquire moments, non-vanishing anapole tiny moments charge radii (requirements squared, parity (require magnetic violation both in parity addition), andcorrections. and time-reversal electric The violation dipole current in mo- experimental addition)orders limits through of on magnitude electroweak larger some radiative than electromagnetic the properties SM predictions, of this neutrino is are a hint for new physics beyond the SM. excellent energy resolution, and sub-keV thresholdthe are the SM, best including candidates to the study neutrinowith physics electromagnetic beyond reactor properties, neutrinos, neutrino WIMPphenomena and [ searches, and other exotic particle physics 2. Electromagnetic Properties of Neutrino magnetic moments action (ignoring gravity) to a remarkable degreecompleted of the precision. set The of discovery particles of predicted the by Higgsthat SM. Boson However, SM has there are does still not several big address, questionsnon-zero such remain neutrino as masses the and observed mixing, matter-antimatterof and asymmetry the the in existence existence the of of Universe, dark neutrino the matter.beyond masses the Experimental and verification SM, mixing which have provided hasboth the triggered theoretical first and intensive experimental direct studies framework. evidence of of nontrivial physics electromagnetic properties in posed of . ItsWeakly non-gravitational Interacting interactions Massive with Particles normal (WIMP) matterof are is direct still detection a unknown. experiments generic are class pursuing the of intensive cold research dark programs towards matter. sensitivity to A number Test of Beyond-Standard-Model Scenarios with Germanium Detectors 1. Introduction 570.7(127.8) kg-days of ON (OFF) with 12 keV threshold data. 3. Searches PoS(ICHEP2018)114 are and sa ν aee µ g (a). This 2 2 10 XMASS-1 ) as a function α Majorana Lakhwinder Singh / ] improved limits 0 RG Stars 4 α Xenon100 10 ) 2 , due to pole structure in ]. The constraints on tran- ν 8 1 (keV/c v µ Edelweiss-2018 (b) M HB star TEXONO (b). These constraints on 1 − 2 10 Sun 2 0. −

10

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] '/ [ log

α α → 1 ) and vector super-WIMP ( 2 q aee 2 . The upper bounds on coupling constant ) are derived from data taken with low-background g sa 3 ν µ (a) and Fig. 1 10 GeV. Based on data taken with CDEX-10 experiment (10 kg Majorana = 0.3 GeV/cm 10 < χ ρ χ ) 2 PANDAX CDMS LUX (keV/c s (a) M 1 nucleus coherent scattering, WIMP and super-WIMP searches. Data taking and

− Solar Neutrino Solar CoGent-2011 Xenon100 CDEX-2017 (a) Limits on the coupling of pseudoscalar super-WIMP with electron as function of mass from EDELWEISS-2018 at various mass are shown in Fig. TEXONO Ge-detectors with sub-keV threshold have been used to study neutrino properties and interac- Sterile neutrinos are singlets in the SM gauge groups, and they are described via their mass Bosonic super-WIMP is well-motivated class of dark matter with coupling smaller than the ) and active-sterile mixing amplitude. Their masses, mixing angles and couplings are un- 1 − α 12 13 10 11 sa 10 − − − − /

0

ae 10 10 10 10 g tions, neutrino more stringent than the current direct upper limits of active neutrinos known. They are inundergo addition radiative viable decays candidates via of mixingone dark with of matter. the the golden active The modes SM massive totic neutrino. sterile look scattering for neutrino process This keV-scale can sterile for process neutrino. a isdifferential It non-relativistic cross considered is sterile section as recently at neutrino identified energy has that transfer a inelas- about pronounced half enhancement of in itssition the mass, magnetic moment as of illustrated sterile in neutrino Fig. and ( low-threshold PCGe detectors at KSNL, as shown in Fig. differential cross section at half of its mass where (m 4. Dark Matter Search weak scale. These particles aretion experimentally or very interesting excitation due of to andeposit their electron energy absorption equivalent in via to ioniza- the their target-atomenergy rest resolution of device mass, the like which detector. PGe-detectors manifest havelow-background advantages Bosonic as and to super-WIMP a study low-threshold would photo-peak. such data class from Therefore, ofCL KNSL DM. a on with Using good the PGe the coupling detectors, constant improved of limits pseudo-scalar at ( 90% are derived for mass WIMP. Figure 1: various benchmark experiments atcoupling 90% from different C.L. astrophysical sources (b) as The well as 90% other C. benchmark experiments. L. bounds on vector bosonic dark matter of particle mass are derived withDM the assumption with that local the DM bosonic density DMα constitutes all of the galactic feature would manifest itself as peaks in the measurable energy spectra [ Test of Beyond-Standard-Model Scenarios with Germanium Detectors light WIMP mass region m p-type point contact Ge-detector array immersed in liquid nitrogen) at CJPL [ PoS(ICHEP2018)114 ]. 5 (2015) 10 ]. (2007) 33 Phys. 75 , Phys. Lett. (2018) s Þ , is m 21 3 (21) ð − 120 Lakhwinder Singh 1601.07257 v; [ 1405.7168 3 [ d Nucl. Instrum. Meth. Þ GeV cm 093012 (2016) Phys. Rev. D , ~ v 10.0 , ð 4 4 . ( eV ) 10 0 93, = 1 MeV. For comparison, vf sa Þ ν 5.0 Excluded Region Excluded were analyzed. The ¼ m (b) Int. J. Mod. Phys. A ; v ρ s , Phys. Rev. Lett. . A dark matter analysis m dT , ð σ 2.0 keV, germanium detectors (2016) 093012 [30,37] d 6(a) (2014) 011301 10 max 93 keV v 1.0 Search of neutrino magnetic moments 90 0 ≤ ) and germanium atoms through the T 3 Z T − s PROPERTIES 0.5 m s 3 10 ≤ A A = 7.1 keV and E ρ A 10

12 13 14 15

− − − − ¼ Limits on light weakly interacting massive

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Full LP EP B m

PHYSICAL REVIEW D ν eV s

sa 10 10 10 10 ) ( µ µ v ¼ 0.2 . The event rate per unit mass on a target of 100  Phys. Rev. D is the mass of the germanium atom and is depicted in Fig. Phys. Rev. D , History and Prospects , dT dR 3 A 0.1 [38] with m  4 6 8 m − 4 V. BOUNDS ON STERILE NEUTRINO 1 sa 10 100 ν 0.01

10 10 10 Characterization and Performance of Germanium

µ

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keV Mb dT d The local dark matter density of A data sample of 139.3 kg-days with a 500 g n-type point 2 are more sensitive to the nonrelativisticthey sterile yield neutrinos bigger for differentialexhibit cross rich, sections unique in structure general (canwith and be fine resolved resolutions). by detectors measured spectra after[29,30,37] standard background suppression is applied tomodels on the the data, sterile neutrino using as conventional cold dark astrophysical matter. where contact germanium detector taken at the Kuo-Sheng Reactor Neutrino Laboratory (KSNL) searching for the atomic ionization interaction of Eq. adopted germanium is given by denotes theMaxwellian mass velocity distribution of sterile neutrino. The normalized where neutrino magnetic moments ofconsidered. active In neutrinos other were words, the transitionarising magnetic moment from theindistinguishable from sterile-to-active those from neutrino activeas neutrino conversion we mixings, is canneutrinos take in the a zero relativisticalso mass process. limit compare In for the thekeV sterile ultrarelativistic same and and sterile figure, active we nonrelativisticconsidered, neutrinos: 7.1- In this low-recoil regime being ]. , 3 T at 90% C.L. from KSNL data. 093012-7 − day data of the cdex-10 experiment eV. 10 sa MeV [27] 5.0 ]. 10.0 ν × 1 ¼ collaboration, H. T. Wong et al., ]. µ s 100 ]. ¼ … v ν ¼ 5.0 collaboration, H. Jiang et al., E 1411.0574 2.0 . [ T s ]. between 1 to ]. m T 1.0 2.0 keV eV, which is outside 1311.5294 keV and [ Atomic ionization by sterile-to-active neutrino conversion and constraints on dark Constraining neutrino electromagnetic properties by germanium detectors Constraints on millicharged neutrinos via analysis of data from atomic ionizations Atomic ionization of germanium by neutrinos from an ab initio approach 1411.4802 T 1 50 [ . For Full FEA . 0.5 5 7 (a) Full keV ∼ 1.0 OLLABORATION 3 ¼ T Taiwan EXperiment On NeutrinO with selected T s Full LPA EPA 1 MeV 1 MeV 10 sa m (2015) 013005 1608.00306 ν OLLABORATION ]. [ s s μ s 0.2 hep-ex/0605006 1802.09016 0.5 [ [ v E E 91 (a) The differential scattering cross section of nonrelativistic sterile neutrinos and germanium (2014) 159 (2016) 67 4(a) with . [Note that the two-body peak for the 0.1 sa ν 8 4 6 4 1 μ 0.2 (20) 10

100

10 10 10 matter sterile neutrinos with germanium detectors 241301 Detectors with sub-keV Sensitivities for Neutrino and Dark Matter Experiments with a high-purity germanium detector at the kuo-sheng nuclear power station with germanium detectors at sub-kev sensitivities A836 Rev. D particles from the first 102.8 kg B 731 1830014 012001 0.01

sa

keV Mb dT d 2 [8] J.-W. Chen et al., the results of LPA (longitudinal photon approximation)shown, and and equivalent (b) photon Exclusion approximation curve (EPA) are of also analysis are continuing at KSNL, complementedaxion-like by dark the CDEX matter experiment searches. atsuppress CJPL the Intensive on sub-keV WIMP R&D background. and programs are being pursued to understandReferences and [1] TEXONO collaboration, A. K. Soma et al., [6] J.-W. Chen et al., [2] H. T. Wong, [3] J.-W. Chen et al., [4]CDEXC [5]TEXONOC Figure 2: atoms through the transition magnetic moment [7] J.-W. Chen et al., Test of Beyond-Standard-Model Scenarios with Germanium Detectors 0.1 6 7 4 5 keV case happens at 1 MeV are given in Fig. 0.01 . 10 10 10 10

0.001

7 1

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d keV Mb

¼ dT ¼ Results for an ultrarelativistic 7.1-keV sterile neutrino of 2 s s transition magnetic moment E the plot range of Fig. (solid line). For comparison, themation results (dashed of line) free and electron the approxi- nonrelativistic case with Notice that these twohave been curves shown are in almost the upper identical panel to of what Fig. 2 of Ref. magnetic moment (dotted line) are also shown. FIG. 5.sterile The neutrinos differential and scattering cross germanium section atoms of through relativistic the transition predicted by Eq. m FIG. 4. The differential scattering cross section of nonrelativistic sterile neutrinos ( ATOMIC IONIZATION BY STERILE-TO-ACTIVE 10 keV, the FEAbelow agrees 1 keV, with the the FEAthe slightly MCRRPA MCRRPA overshoots result; result and by for differs about from a factor of 2 at