An induced annual modulation signature in COSINE-100 data by DAMA/LIBRA’s analysis method
Govinda Adhikari, N. Carlin, J. J. Choi, S. Choi, A. C. Ezeribe, L. E. França, C. Ha, I. S. Hahn, Sophia J. Hollick, Eunju Jeon, J. H. Jo, Han Wool Joo, W. G. Kang, M. Kauer, Bong-Ho Kim, H. J. Kim, Jinyoung Kim, K.W. Kim, SungHyun Kim, S.K. Kim, Won Kyung Kim, Y.D. Kim, Y. H. Kim, Y. J. Ko, Doo Hyok Lee, Eun Kyung Lee, Hyunseok Lee, H. S. Lee, Hye Young Lee, In Soo Lee, Jaison Lee, Jooyoung Lee, M. H. Lee, Seo Hyun Lee, Seung Mok Lee, Y.-J. Lee, D. S. Leonard, B. B. Manzato, R. Maruyama, Robert J. Neal, J. A. Nikkel, S. L. Olsen, Byung Ju Park, Reina H. Maruyama, Hyeonseo Park, Kang-Soon Park, Se Dong Park, R. L. C. Pitta, H. Prihtiadi, S. Ra, C. Rott, Keon Ah Shin, A. Scarff, N.J.C. Spooner, W. G. Thompson, L. Yang, Gyun Ho Yu, A. Scarff, N.J.C. Spooner, W. G. Thompson, L. Yang, Gyun Ho Yu
Abstract
The DAMA/LIBRA collaboration has reported the observation of an annual modulation in the event rate that has been attributed to dark matter interactions over the last two decades. However, even though tremendous efforts to detect similar dark matter interactions were pursued, no definitive evidence has been observed to corroborate the DAMA/LIBRA signal. Many studies assuming various dark matter models have attempted to reconcile DAMA/LIBRA's modulation signals and null results from other experiments, however no clear conclusion can be drawn. Apart from the dark matter hypothesis, several studies have examined the possibility that the modulation is induced by variations in detector's environment or their specific analysis methods. In particular, a recent study presents a possible cause of the annual modulation from an analysis method adopted by the DAMA/LIBRA experiment in which the observed annual modulation could be reproduced by a slowly varying time-dependent background. Here, we study the COSINE-100 data using an analysis method similar to the one adopted by the DAMA/LIBRA experiment and observe a significant annual modulation, however the modulation phase is almost opposite to that of the DAMA/LIBRA data. Assuming the same background composition for COSINE-100 and DAMA/LIBRA, simulated experiments for the DAMA/LIBRA without dark matter signals also provide significant annual modulation with an amplitude similar to DAMA/LIBRA with opposite phase. Even though this observation does not directly explain the DAMA/LIBRA results directly, this interesting phenomenon motivates more profound studies of the time-dependent DAMA/LIBRA background data.