I am an Assistant Professor in the College of Information and Computer Sciences (CICS) at the University of Massachusetts Amherst, affiliated with the Center for Intelligent Information Retrieval (CIIR). My research focuses on designing and evaluating statistical and machine learning models with applications to (interactive) information access systems, including search engines, recommender systems, and question answering. I am currently focusing on Neural Information Retrieval and Conversational Search.

Prior to UMass, I was a Researcher at Microsoft, working on a wide range of problems related to search engines. I received my Ph.D. in 2019 from UMass under the direction of W. Bruce Croft. I am the recipient of the CICS Outstanding Dissertation Award for my Ph.D. thesis on weakly supervised neural information retrieval. I obtained my M.Sc. and B.Sc. degrees from the University of Tehran.

I am an active member of the information retrieval (IR) community and regularly publish at the major IR venues, such as SIGIR, WSDM, WWW, CIKM, ICTIR, and ECIR. A brief description of my past and current research is presented below.

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NEW: We released MIMICS, a large-scale data collection for search clarification. [paper] [data]

NEW: We released Macaw, an open-source platform for conversational information seeking research. [paper] [GitHub Repo]

Prospective Ph.D. Students: I will be hiring multiple Ph.D. students to join the CIIR in Fall 2021. If you are interested in working with me, please apply to our graduate program and list me as a potential advisor. Feel free to send me an email once you submit your application.


My research interests include various aspects of information retrieval, recommender systems, and text mining. My major contributions and current research focus include:

Neural Information Retrieval: Following our initial study on distributed representations for information retrieval (ICTIR16a, ICTIR16b, CIKM16), we have developed multiple neural network models for the fundamental IR tasks. They include relevance-based word embedding (SIGIR17a), context-aware query representation (WWW17), and semi-structured document representation (WSDM18). We have also invented the first learning to rank model that can retrieve (as opposed to re-rank) documents from large-scale collections, called standalone neural ranking model (CIKM18a).

Weak Supervision for IR: We have developed a student-teacher learning model for training machine learning IR models with no labeled data, called weak supervision. We have empirically shown the effectiveness of weak supervision in various IR tasks, including ad-hoc retrieval (SIGIR17b), representation learning (SIGIR17a), and query performance prediction (SIGIR18a). We have also theoretically study weak supervision for information retrieval (ICTIR18). Check out our SIGIR 2018 workshop on learning from limited or noisy data (LND4IR).

Conversational Information Seeking: I have recently focused on conversational search and recommendation with a focus on mixed-initiative interactions, such as asking clarifying questions. We have designed and implemented an extensible platform for conversational information seeking research, called Macaw (see the GitHub repository). We have developed models for generating and selecting clarifying questions (WWW20, SIGIR20a), models for utilizing user response to clarifying questions (SIGIR20b), and offline evaluation methodologies for asking clarifying questions in conversational systems (SIGIR19a). Related to conversational search, we have implemented a unified search framework for mobile devices (SIGIR18b, CIKM18b).

IR Meets RecSys: I have made efforts on bridging the gap between the IR and RecSys communities. We have modeled query expansion as collaborative filtering (CIKM16), proposed content-based recommendation models using IR techniques (RecSys17, IRJ18), and designed a joint search and recommendation model (DESIRES18, WSDM20). I co-organized the ACM Recommender Systems Challenge in 2018 on music playlist generation and continuation, which can be seen as a RecSys or IR task (RecSys18). Check out our visions on music recommendation (IJMIR18) and the overview of ACM RecSys Challenge 2018 (TIST19).


In Fall 2018, I taught CS646, the Information Retrieval course (PhD-level), at UMass Amherst. The course webpage is available here.

Invited Talks

  • (Invited Talk) LTI Colloquium, Carnegie Mellon University, Virtual Event, Oct. 2, 2020 Link
  • (Invited Talk) Amazon Alexa, Virtual Event, Apr. 24, 2020
  • (Invited Talk) University of Massachusetts, Amherst, MA, Mar. 9, 2020 Link
  • (Invited Talk) Radboud University, Nijmegen, The Netherlands, Feb. 25, 2020
  • (Invited Talk) University of Amsterdam, The Netherlands, Feb. 24, 2020 Link
  • (Keynote Speaker & Panelist) ConvERSe Workshop at WSDM, Houston, TX, Feb. 7, 2020 Link
  • (Invited Talk) Dagstuhl Conversational Search Seminar, Wadern, Germany, Nov. 14, 2019
  • (Invited Talk) Allen Institute for Artificial Intelligence (AI2), Seattle, WA, Jun. 20, 2019
  • (Invited Talk) Microsoft Research, Redmond, WA, Jun. 6, 2019
  • (Invited Talk) University of Tehran, Tehran, Iran, Apr. 9, 2019
  • (Invited Talk) Purdue University, West Lafayette, IN, Mar. 27-28, 2019
  • (Invited Talk) University of Illinois, Chicago, IL, Mar. 19, 2019
  • (Invited Talk) University of Texas, Austin, TX, Mar. 12, 2019
  • (Invited Talk) University of North Texas, Denton, TX, Mar. 8, 2019
  • (Invited Talk) Yale University, New Haven, CT, Feb. 28, 2019 Link
  • (Invited Talk) University of Maryland, College Park, MD, Feb. 20-21, 2019 Link
  • (Invited Talk) University of Pittsburgh, PA, Feb. 4-5, 2019 Link
  • (Invited Talk) UMass Data Science Talk, Amherst, MA, Oct. 24, 2018 Link
  • (Invited Talk) Microsoft Research, Redmond, WA, Sep. 18, 2018
  • (Invited Talk) Google Research, Mountain View, CA, Mar. 21, 2018
  • (Invited Talk) Amazon’s A9, Palo Alto, CA, Mar. 19, 2018 (with Bruce Croft and Qingyao Ai)
  • (Invited Talk) Yale University, New Haven, CT, Mar. 2, 2018 Link

Selected Recent Publications

Academic Services

  • Organizer / Chair:
  • Guest Editor:
    • ACM Transactions on Information Systems: Special Issue on Conversational Search and Recommendation
  • Senior Program Committee:
    • SIGIR 2020
    • The Web Conference (WWW) 2021
  • Program Committee:
    • SIGIR 2018 – 2019
    • The Web Conference (WWW) 2018 – 2020
    • WSDM 2018 – 2020
    • RecSys 2018 – 2020
    • CIKM 2017 – 2020
    • ICTIR 2019 – 2020
    • ICLR 2020
    • NAACL 2019
    • ECIR 2019 (short papers)
    • DESIRES 2020
    • Workshops: NLI @ ACL 2020 – PodRecs @ RecSys 2020 – SCAI @ IJCAI 2019 – EARS @ SIGIR 2018 – KG4IR @ SIGIR 2017, 2018 – NeuIR @ SIGIR 2017 – LEARNER @ ICTIR 2017 – RecSysChallenge @ RecSys 2017
  • Journal Reviewer:
    • TOIS
    • IRJ
    • IP&M
    • TKDE
    • TWEB
    • TIIS
    • JASIST
    • Inf. Syst.
  • ACM SIGIR Student Liaison (representing North and South Americas) 2017 – 2019