Ricochet† Using Low Temperature Bolometers for Coherent Neutrino
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Ricochet† Using Low Temperature Bolometers for Coherent Neutrino Scattering †An experiment in three courses Joseph A. Formaggio Outline (I) First Course: Science Motivation (II) Second Course: The Ricochet Detector (III) Last Course: Ricochet & Chooz Outline (I) First Course: Science Motivation (II) Second Course: The Ricochet Detector (III) Last Course: Ricochet & Chooz Yet, some of their Make-and/or- properties may also Break eventually lead to it’s unraveling. Neutrinos helped The Super-Kamiokande detector in Japan, which helped establish neutrino confirm the validity of mass (a violation of the Standard Model) what we call “the Standard Model” Image from Gargamelle neutrino experiment, which helped confirm the electroweak model Inverse Beta Decay: How Neutrinos + Interact ⌫¯e + p n + e ! Poltergeist Cd The fact that it took 20 years to Gd + γ detect the first neutrino is a Li } testament to the difficulty of the task. We will focus on neutrino energies EMBARGOED UNTIL 2:00 PM US ET THURSDAY, 3 AUGUST 2017 associated with nuclear reactors Coherent Neutrino Scattering: (2-20 MeV) for this discussion. ⌫ + A ⌫ + A ! There are two primary ways which one can use to detect neutrinos: inverse beta decay and coherent elastic neutrino nuclear scattering (CEνNS). COHERENT Fig. 2. COHERENT detectors populating the “neutrino alley” at the SNS (34). Locations in this basement corridor profit from more than 19 m of continuous shielding against beam-related neutrons, and a modest 8 m.w.e. overburden able to reduce cosmic-ray induced backgrounds, while 11 2 sustaining an instantaneous neutrino flux as high as 1.7 × 10 νµ / cm s. First release: 3 August 2017 www.sciencemag.org (Page numbers not final at time of first release) 8 What’s So Special About Coherence? ν ν Incoming Neutrino Outgoing Neutrino Neutrons Protons Nucleon Size (<< 1 fm) One can think of the energy (really, momentum) the neutrino imparts on its target as a way to probe the nucleus. The higher the imparted momentum, the finer the probe. Non-Coherent Interactions e- ν Incoming Neutrino Outgoing Neutrino Neutrons Protons Nucleon Size (<< 1 fm) In this case, the probe momentum is such that it singles out a single neutron or proton. Coherent Interactions ν ν Nucleus Size (> 1 fm) However, if the exchange momentum is small enough, the probe just sees the entire nucleus, and no single proton or neutron is singled out. Result: Interaction probability (cross-section) scales as the number of nucleons squared. Fundamental Coherent Interactions Coherent scattering has been proposed and schemed as a means of detecting neutrinos for many decades. Despite being proposed 40+ years ago, this process has yet to be observed. Fundamental Coherent Interactions Coupling term (tiny) Cross-section (probability of interacting) Coherence effect Neutrino energy Coherent scattering has been proposed and schemed as a means of detecting neutrinos for many decades. Despite being proposed 40+ years ago, this process has yet to be observed. Fundamental Coherent Interactions Coupling term (tiny) Cross-section (probability of interacting) Coherence effect Neutrino energy Coherent scattering has been proposed and schemed as a means of detecting neutrinos for many decades. Despite being proposed 40+ years ago, this process has yet to be observed.WAIT! That’s no longer true! EMBARGOED UNTIL 2:00 PM US ET THURSDAY, 3 AUGUST 2017 Discovery! As of August 3rd, 2017, a first detection of coherent neutrino scattering has been reported by COHERENT! The process does indeed take place. Only 16 kg-years to get ~7 sigma! Fig. 3. Observation of Coherent Elastic Neutrino-Nucleus Scattering. Shown are residual differences (datapoints) between CsI[Na] signals in the 12 µs following POT triggers, and those in a 12-µs window before, as a function of their (A) energy (number of photoelectrons detected), and of (B) event arrival time (onset of scintillation). Steady-state environmental backgrounds contribute to both groups of signals equally, vanishing in the subtraction. Error bars are statistical. These residuals are shown for 153.5 live-days of SNS Coherent neutrino detection from inactivity (“Beam OFF”) and 308.1 live-days of neutrino production (“Beam ON”), over which 7.48 GWhr of 23 EMBARGOED UNTIL 2:00 PM US ET THURSDAY, 3 AUGUST 2017 energy (~1.76 × 10 protons) was delivered to the mercury target. Approximately 1.17 photoelectrons are reactors remains a goal for future expected per keV of cesium or iodine nuclear recoil energy (34). Characteristic excesses closely following the experiments. Standard Model CEνNS prediction (histograms) are observed for periods of neutrino production only, with a rate correlated to instantaneous beam power (fig. S14). Fig. 2. COHERENT detectors populating the “neutrino alley” at the SNS (34). Locations in this basement corridor profit from more than 19 m of continuous shielding against beam-related neutrons, and a modest 8 m.w.e. overburden able to reduce cosmic-ray induced backgrounds, whileFirst release: 3 August 2017 www.sciencemag.org (Page numbers not final at time of first release) 9 11 2 sustaining an instantaneous neutrino flux as high as 1.7 × 10 νµ / cm s. First release: 3 August 2017 www.sciencemag.org (Page numbers not final at time of first release) 8 ν ν Opening New Doors ν ν Opening New Doors Step 1: Confirm Standard Model prediction Statistics needed: ~ O(1) ν ν Opening New Doors Step 1: Step n+1: Confirm Standard Model Measure Weinberg angle at prediction low Q2 Non-standard interactions Sterile neutrinos Neutrino magnetic moments Reactor monitoring Statistics needed: Statistics needed: ~ O(1) >>O(100) Possible Science Reach *J. Billard Ricochet: sensitivity to µν J. Billard and B. Kavanagh, in preparation • Scientific Drivers: Threshold: 0.1 keV ×10−9 ] 0.3 B 90% C.L. contours µ Preliminary • Better understanding of fundamental [ ν neutrino interactions. µ • Understanding the physics of 0.2 supernova explosions. Back. Tot. = 1.4 /kg/day 5% signal syst. TEXONO (data?) 20% (betas) back. syst. (arXiv:1506.08377) • Direct probe into nuclear (neutron) 1000 kg.year Ge exposure structure of nuclei. 0.1 APV (q = 2.4 MeV) Ricochet • New physics (sterile neutrinos, magnetic moment, weak mixing Ricochet + APV 0 angle). 0.05 0.1 0.15 0.2 0.25 0.3 2 6 sin θw • New possibilities looking for axion and dark forces (arXiv:1504.07237). • Technology Drivers: • Leveraging technology of neutrino and dark matter detectors. Possible Science Reach *J. Billard Ricochet:Ricochet: sensitivitysensitivity toto µµνν J.J. Billard and B. Kavanagh, inin preparationpreparation Threshold: 0.01 keV • Scientific Drivers: −9 Threshold: 0.1 keV ×10 −9 ] ×10 ] 0.3 B 0.3 B 90% C.L. contours µ Preliminary 90% C.L. contours µ Preliminary [ • Better understanding of fundamental [ ν ν µ neutrino interactions. µ • Understanding the physics of 0.20.2 supernova explosions. Back.Back. Tot. Tot. = = 1.4 1.4 /kg/day /kg/day 5%5% signal signal syst. syst. TEXONO (data?) 20%20% (betas) (betas) back. back. syst. syst. (arXiv:1506.08377) • Direct probe into nuclear (neutron) 10001000 kg.year kg.year Ge Ge exposure exposure structure of nuclei. 0.10.1 APVAPV (q (q = = 2.4 2.4 MeV)MeV) Ricochet • New physics (sterile neutrinos, Ricochet magnetic moment, weak mixing RicochetRicochet + + APV APV 0 angle). 00.05 0.1 0.15 0.2 0.25 0.3 0.05 0.1 0.15 0.2 0.25 2 0.3 sin2 67 sin θθww • New possibilities looking for axion and dark forces (arXiv:1504.07237). • Technology Drivers: • Leveraging technology of neutrino and dark matter detectors. The Case for Sterile Neutrinos •A number of recent (and not so recent) • All suggestive, but no “smoking results seem to indicate the possibility gun” accepted by the of sterile neutrinosThe†. Reactor Anomaly (RAA) community at the moment. ? ? ? Atm. oscillation Solar oscillation Phys. Rev. D 83, 073006 (2011) 3σ anomaly Reactor Anomaly † The initial inception of RicochetTh. Lasserre was –toHEP search 2017 for sterile neutrinos, discussed over coffee. Genuine Neutrino “Application” Monitoring of Heavy Water • When applied to nuclear Reactors reactors, it is possible to monitor arXiv:1403.7065v1 the activity of the reactor core activity and fuel composition with a relatively compact device. Heavy Water Reactor in Arak, Iran • Possibility of first genuine applied technology for neutrino physics. • There have been spin-offs from the technology developed for neutrinos. But here we discuss actually using neutrinos as part of that technology. Monitoring of Spent Fuel arXiv:1606.06309v1 Outline (I) First Course: Science Motivation (II) Second Course: The Ricochet Detector (III) Last Course: Ricochet & Chooz Different Approaches to Detection “Heat” Phonons (meV/ph) 100% energy Ionization Scintillation (10 eV/e-) (1 keV/Ɣ) 10% of energy few % of energy “Charge” “Light” Where Phonon Ricochet Technology is Used CUORE CMB, Infrared detection Dark matter 0νββ • To go to lower neutrino energies, lower threshold are required. Phonon readout is a promising technology already used in many other experiments. • Ricochet uses phonon readout to reach low threshold, with eventual goal of reaching 10 eV recoil threshold. Cryogenic Bolometers Cryogenic Bolometers Technology for large NumberCalorimetry of Pixels no filter for events far(ECHO, from endpointHOLMES & NuMECS) Ω needs large number of counts Ω needs large number of pixels needs ~ 1010 counts for m ~ 10 eV ~ 1013 counts for m ~ sub 1 eV Temperature rise in cryogenic bolometers proportional to energy deposition & capacitance. Since capacitance drops as T3 in insulators/