Coherency in Neutrino-Nucleus Elastic Scattering ( A el ) Vivek - PowerPoint PPT Presentation

Coherency in Neutrino-Nucleus Elastic Scattering ( ν A el ) Vivek Sharma On behalf of TEXONO Collaboration Institute of Physics, Academia Sinica, Taiwan Outline Introduction and Motivation. ● TEXONO Facilities. ● ν A el at KSNL. ● Background and Threshold. ● Sensitivity of Experiment. ● Coherency in ν A el scattering ● Status and Summary. ● Thursday, 12 Sep. 2019

Coherent Neutrino-Nucleus Scattering A neutrino interacts with a nucleus of neutron number “N” via exchange of Z - Boson. ν + N ν + N Cross-Section of ν A el : Where G F is fermi constant, E ν is incident neutrino energy, Z(N) is Atomic(Neutron) number of nuclei and q is three momentum transfer. ε = 1 – 4Sin 2 Θ W = 0.045, gives N 2 dependence Importance: Requirements: ✓ Important role in Supernova Explosions. ➢ High Neutrino Flux. ✓ Test of fundamental SM-electroweak ➢ Lower Threshold. interaction. ➢ Better Resolution. ✓ In study of Beyond Standard Model Physics. ➢ Quenching Factor. ✓ Probe transition of Quantum Mechanical ➢ Background Understanding. Coherency in electro-weak process. ➢ Better Shielding from Gamma, ✓ Potential use in Reactor monitoring Neutrons etc.. as a portable device. ➢ Sufficient Source On/Off ✓ ν A el Scattering is important to study the Statistics. irreducible background for Dark Matter Search.

TEXONO Collaboration ● TEXONO (T aiwan EX periment O n N eutrin O) Experiment is located at Kuo-Sheng Nuclear Power Plant -II on northern shore of Taiwan. ● Theme: Low Energy Neutrino Physics and Dark Matter Searches. ● Collaboration with Turkey, China and India. ● The reactor power of 2.9 GW gives 6.35 × 10 12 cm -2 s -1 electron anti- neutrinos at a distance of 28 m. ● Collaboration with CDEX Underground Dark-Matter Experiment, China.

Kuo-Sheng Reactor Laboratory (KSNL) Reactor neutrino Neutrino Flux ~6.35 x 10 12 cm -2 s -1 28 m from core#1 @ 2.9 GW ~30 mwe overburden Detectors and Shielding Control lab

Neutrino Properties and Interaction at KSNL Quality Mass Detector Requirements ν -e Scattering SM [PRD10] & NSI/BSM [PRD10,PRD12,PRD15,PRD17] � 200 kg CsI(Tl) Magnetic Moments [PRL03,PRD05,PRD07] � 1 kg HPGe ν N Coherent Scattering [Current Theme;PRD16] Neutrino Milli-charge � sub-keV O(kg) ULEGe / PCGe [PRD14] ! Dark Matter Searches @ KSNL [PRD09,PRL13,AP14] � sub-keV O(kg) ULEGe/PCGe ! CDEX Program@CJPL [PRD13,PRD14,PRD14;PRD16,PRD17] ! Theory Program

Hardware and Thresholds p- PCGe [500g – 1 kg] p + n + (~1mm Li diffused) 900 g n- PCGe [500 g] n + p + (~0.5 µm Boron implanted) 500 g Generation Mass Pulsar FWHM Threshold (g) (eV ee ) (eV ee ) G1 500 130 500 G2 900 100 300 G3 1430 soon soon

G3 Detector Advantages of G-3 Electro-cooled HPGe Detectors: ➢ No liquid Nitrogen required. ➢ Controlled microphonic noise. ➢ Customised achievable temperature. Side View Top View Cooler Electrically Refrigerated HPGe Detector

Nuclear Recoil, ν A el Rate and Quenching Maximum Nuclear Recoil corresponding to Reactor Neutrino Maximum Neutrino Energy for Germanium Maximum nuclear recoil depends on mass of target nuclei and Averaged recoil energy for Germanium target incident neutrino energy TRIM is used for Quenching factor for Expected ν A el differential rate in various detectors at Kuo- Sheng Neutrino Laboratory Germanium target

ν A el at KSNL with Reactor neutrino.. Threshold 300 eV 200 eV 150 eV 100 eV Differential 0.8 cpkkd 8.3 cpkkd 27.3 cpkkd 109.5 cpkkd Integral 0.04 cpkd 0.47 cpkd 1.6 cpkd 6.4 cpkd

Threshold and Background at KSNL Current Status and Future Goal to Probe ν A el as predicted in Standard Model .. Achieved Target

Coherency in ν A el Scattering Form-Factor: ■ Gives an idea about coherency within the nucleons. ■ Used for study of Nuclear Structure. ■ Complete Coherence at low Energy. ■ ν A el measures the neutron distribution. Form-Factor is Fourier transformation of Charge distribution in the nucleus: Helm Model Form-Factor: G.Duda et.al, JCAP04(2007)012

Coherency in ν A el Scattering The finite phase of net combined amplitude vector can define degree ● of coherency. Combined amplitude can be defined as: ● where The cross-section comprise (N + Z) 2 terms. ● In total cross-section , average phase mis- ● alignment angle follows: Degree of coherency described as : ● ( α ) = Phys. Rev. D 93, 113006 (2016)

Contour for Degree of coherency Reactor and solar neutrino seems to probe ν A el in region with higher degree of coherency Lower mass nuclei are better choice for higher degree of coherency Provides minimal uncertainty region @T min = 0

Coherency and Relative cross-section.. In case of T min = 0 The relative change in cross- section can be given as: In case of Monoenergetic Source: Lower Detector threshold Higher Degree of coherency

Continued.. Xe 0.98 0.96 α 0.99 0.98 0.97 Ge Expected Coherency increases 0.995 0.99 0.985 0.98 Ar 2 10 Integral with lower threshold detectors. Reactor ν e ) -1 10 day -1 Light target are better for 1 Counts (kg high degree of coherency even 1 − 10 with high detector threshold. − 2 10 3 − 10 0 0.5 1 1.5 2 2.5 3 3.5 T (keV ) thrd nr Different neutrino sources are important in probing different coherency regions. Averaged degree of coherency also depends on the detector threshold

Status of ν A el Scattering @KSNL

Summary ● Study of ν A el interaction has importance in order to study the electroweak interaction in SM, Astrophysics and Irreducible background in Dark Matter searches. ● ν A el can be probed by several experiments in the near future with different neutrino sources. ● Studies for ν A el from different neutrino sources probe transitions of QM Coherency in Electroweak process. ● Probe to BSM using ν A el interaction with low energy neutrinos is less vulnerable to uncertainties in coherency and Form-Factor. ● Ultra low energy threshold 300 eV is achieved and 150 eV is expected from future detector. ● Expecting advances for different Targets and Sources .

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