KDAR Neutrino Measurements with JSNS2 Johnathon Jordan for the JSNS2 Collaboration University of Michigan Poster #482 Proton Beam Linear Accelerator RCS MLF MLF Beam Layout Mercury Target When charged kaons decay at rest, they can produce monoenergetic neu- trinos from the two-body decay: These known-energy kaon de- cay-at-rest (KDAR) neutrinos can be used to make a variety of interesting physics measurements. KDAR Neutrino Proton Neutron KDAR Neutrino Neutrino-induced Nuclear Excitations Neutrino-Nucleon Interactions *Cartoon KDAR Neutrino Basics The MLF Neutrino Source KDAR neutrinos offer a standard candle to benchmark neutrino interac- tion models relevant for future oscilla- tion experiments [1]. Their intermedi- ate energy allows them to probe the transition between neutrino-nucleus and neutrino-nucleon scattering [2]. KDAR neutrinos can also be used for a variety of other measurements [3,4]. The J-PARC Material and Life Science Experimental Facility (MLF) is a spall- ation neutron source in Japan. A high intensity proton beam is accelerated to 3 GeV by the Rapid Cycle Synchrotron (RCS) and delivered to a liquid mercury target in the MLF. In addition to provid- ing a world-class spallation neutron source, the mercury target is also an intense source of decay-at-rest (DAR) neutrinos. The MLF design beam power is 1 MW and the beam power has been steadily increasing (in June beam power has been ~610 kW). The 3 GeV beam energy is high enough for kaons to be produced in the target where they quickly slow down and decay at rest. This fact combined with the high beam intesnity makes the MLF the best place in the world to do physics with KDAR neutrinos. 104 105 106 107 Neutrino Flux (Arb. Units) µ π K −600 −400 −200 0 200 400 600 800 1000 Time (ns) 0 20 Current (A) ×25 Hz Beam Pulses 0 100 200 300 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 Energy (MeV) ν/POT/2 MeV The JSNS2 Experiment Neutrino Flux + Timing θ 2 2 sin 4 − 10 3 − 10 2 − 10 1 − 10 1 ] 4 /c 2 [eV 2 m Δ 2 − 10 1 − 10 1 10 2 10 90%C.L 2 JSNS LSND 99%C.L LSND 90%C.L OPERA(2013) 90%C.L 1 MW x 3 years exposure 1 detector (17 tons ﬁducial) Protons are delivered to the MLF at 25 Hz in two pulses. Neutrinos from kaon decays are produced in time with the beam due to the short kaon lifetime. The low duty factor of the beam re- duces beam-off backgrounds to KDAR neutrino measurements. Most neutrino parents decay at rest in the target and shielding, so the result- ing neutrino ﬂux largely consists of well-understood decay-at-rest compo- nents. Thus, decay-in-ﬂight (DIF) neu- trino backgrounds to KDAR neutrinos are small. The J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source (JSNS2) [5] is a short baseline neutrino oscillation experiment. JSNS2 is de- signed to search for oscillations with ∆m2 ~ 1 eV2 using the double coincidence signature of IDB (prompt positron, delayed neutron capture). JSNS2 has collected 10 days of initial data this month (expected to contain 200-400 KDAR events) and will continue operation in the fall. JSNS2 utilizes a liquid scintillator (LS) neutrino detector consisting of an inner volume ﬁlled with gadolini- um-doped LS and outer buffer and veto regions ﬁlled with undoped LS. Scintillation light is collected by 120 10-inch PMTs including 24 PMTs in the veto region used to reject activity origi- nating outside the detector. There is additional shielding under the detec- tor to reduce environmental gamma backgrounds produced in the concrete hatch the detector sits on. KDAR Signatures in JSNS2 References + Acknowledgements                   Other JSNS2 Posters JSNS2 is most sensitive to KDAR neutri- no charged current interactions. In most events, the expected event sig- nature is a double coincidence be- tween the initial neutrino interacion products and the subsequent muon decay (lifetime ~2.2 μs): In ~20% of interactions, the ﬁnal state is also expected to con