News Article

IU-CEEM nuclear physics group discovers new neutrino process

August 3, 2017 

The COHERENT experiment, running on the Spallation Neutron Source (SNS)  at Oak Ridge National Lab, recently announced the discovery of a new type of neutrino interaction called "coherent elastic  neutrino-nucleus scattering." In this process (abbreviated "CEvNS") a  neutrino collides with a nucleus transferring enough energy to the nucleus so  that it may be detected.  Because the  neutrino has a small mass and the nucleus is heavy, the energy of the recoiling  nucleus is very small -- imagine a ping-pong ball (neutrino) hitting a bowling  ball (nucleus). CEvNS, predicted to  exist in 1974, has eluded discovery until now because of the challenging  technology required to produce enough neutrinos and to detect the low energy  nucleus. The recent result came from data collected over 1.5 years with a 15kg  cesium iodide (CsI) crystal located in a well-shielded basement corridor of the  SNS. The CsI detector is capable of  detecting the very low energy nuclear recoils and the detector location has a  very high flux of neutrinos from the SNS neutron source but a low rate of  radiation background that may mask the CEvNS signal.

The IU scientists involved are in the experimental  nuclear physics neutrino  group led by Prof. Rex Tayloe along with Mike Snow; postdocs Ivan  Tolstukhin and Tyler Thornton; graduate students Matthew Heath, Jacob  Zettlemoyer, Daniel Winney, Ben Suh; undergraduate and Cox research scholar Maria  Del Valle Coello; and technical staff Walt Fox, Gerard Visser, and John  Vandewerp.

Their effort on the project started with measurements of  the background in the SNS area using the SciBath neutral particle detector that  helped determine that the experimental area had the low background rates  required. After those intial  measurements, they deployed a 25kg liquid argon "CENNS-10" detector  to double check the initial discovery with a different detector  technology. These subsequent  measurements will utilize the CEvNS process to investigate possible defects in  the standard model of particle physics and to search for the dark matter.