Sindhujha Kumaran M.Sc.

Sindhujha Kumaran M.Sc.
  • October 2018 - March 2022 (Doctoral student)
  • Doctoral thesis: Geoneutrinos and solar neutrinos with the Borexino experiment
  • September 2017 - September 2018 (Master student)
  • Master thesis: Updated geoneutrino measurement with the Borexino detector

Contact:
  • Phone: +49 2461 61 4123
  • E-mail: sindhujha.kumaran_AT_rwth-aachen.de

Education

Geoneutrinos

My work on geoneutrinos focused on the improvement of the "standard" selection cuts in Borexino and performing sensitivity studies. The work is the continuation of my Master's thesis. The improved selection cuts such as sophisticated cosmogenic vetoes and an enlarged fiducial volume increased the exposure of the analysis almost two-fold. Furthermore, I have als0 evaluated most of the non-antineutrino backgrounds, and have improved and performed the final spectral fits in different configurations. This work along with the geological interpretations was published in 2020. This paper, co-written by me, gives a comprehensive overview and serves as a reference for next-generation liquid scintillation detectors.

CNO-cycle solar neutrinos

My work for the observation and the possible measurement of CNO-cycle solar neutrinos involves monitoring the Po-210 rate in Borexino, in order to obtain the Bi-210 rate, the most important background for CNO solar neutrinos. The extraction of the Bi-210 upper limit for the first experimental evidence of CNO neutrinos was published in 2020. I cross-checked the "standard" method using ROOT, as well as co-developed a new and improved method using a Bayesian nested sampling algorithm called MultiNest to perform higher dimensional fits. The analysis has also been further improved and updated for the full Phase-III dataset of Borexino until October 2021, for the CNO analysis that is planned to be submitted for publication in May 2022. My other contributions for the CNO analysis include performing the final multivariate fits, along with the evaluation of the systematic uncertainties associated with the fit parameters.

Directionality of sub-MeV solar neutrinos

In a liquid scintillator detector like Borexino, it is challenging to study the directional properties of neutrino events due to the domination of isotropic scintillation light. However, since Cherenkov photons are emitted much faster with respect to scintillation light, their hit time properties can be exploited for the statistical separation of scintillation and Cherenkov photons. This is performed by correlating the direction of the first few photon hits of events to the well-known position of the Sun and integrating this over a large number of events, through a novel technique called Correlated and Integrated Directionality (CID) . My work for this analysis includes the tuning of the Borexino Monte-Carlo using gamma calibration sources to accommodate the study of Cherenkov photons, optimisation of the data selection cuts, evaluation of systematic uncertainties, and performing stability checks and the final fits. The first ever directional measurement of sub-MeV solar neutrinos using this analysis has been published jointly as a short PRL letter and a long PRD article, and these articles were co-written by me.

Teaching

  • Neutrino Physics tutor, Summer semester 2020, RWTH Aachen University

    • Publications

    Selected events


    Physics outreach

  • Jan 2020: Volunteer for Borexino, Tag der Physik, RWTH Aachen University
  • Jul 2019: Volunteer for Particle Physics, Tag der Neugier, Forschungszentrum Juelich