Lit3R: Retrieve–Relate–Read for Evidence-Grounded Question Answering over Scientific Literature

Akira Ise, Kotaro Kumagai, Yuta Yamaguchi, Hisanori Ozaki, Yukio Uematsu, Ikuya Yamada


Abstract
We describe tus-nlp’s Lit3R (Retrieve–Relate–Read) system for LitTraceQA, a shared task for literature-grounded question answering that requires systems to retrieve relevant papers, identify supporting evidence, and generate answers. Lit3R combines off-the-shelf retrieval, reranking, and large language model (LLM) components without task-specific training. The retriever iteratively combines BM25-based sparse and dense retrieval, cross-encoder reranking, and LLM-based verification, and complements retrieval based on the question with paper-to-paper expansion. The reader first identifies supporting evidence within individual papers and then synthesizes evidence across papers to produce the final answer and evidence trace. On the official test set, our system ranked 4th on the leaderboard. Our code is available at https://github.com/tus-ist-nlp/littraceqa.
Anthology ID:
2026.groundlm-1.89
Volume:
Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Yimu Wang, Yee Man Choi, Di Wu, Siqi Ouyang, Mozhgan Nasr Azadani, Yi R. (May) Fung
Venues:
GroundLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1205–1213
Language:
URL:
https://aclanthology.org/2026.groundlm-1.89/
DOI:
Bibkey:
Cite (ACL):
Akira Ise, Kotaro Kumagai, Yuta Yamaguchi, Hisanori Ozaki, Yukio Uematsu, and Ikuya Yamada. 2026. Lit3R: Retrieve–Relate–Read for Evidence-Grounded Question Answering over Scientific Literature. In Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026), pages 1205–1213, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Lit3R: Retrieve–Relate–Read for Evidence-Grounded Question Answering over Scientific Literature (Ise et al., GroundLM 2026)
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PDF:
https://aclanthology.org/2026.groundlm-1.89.pdf