For Reham Aly from Egypt, now a graduate student on CMS at the University of Bari, Italy, this was the first visit to the United States and Fermilab. She had been invited to come to work at the Fermilab LHC Physics Center, or LPC, for two months under the Guest and Visitors Program. Another student, Angela Taliercio, an Italian working on her Ph.D. at the University of Louvain, Belgium, also supported by the same program, had visited the LPC in 2018. The rewarding experience she had, she says, made her want to come back. Reham and Angela spent staggered two-month periods at Fermilab, from October to December 2019.
University of Bari Professor Nicola De Filippis, also a distinguished visitor at the LPC, and Fermilab scientist Pushpa Bhat mentor both students. Reham looks for dark matter signatures in the monoHiggs channel with four leptons in the final state (coming from Higgs decays into Z boson pairs) and missing transverse energy, and Angela studies diHiggs production in the four-lepton-plus-two-b-jets decay channel. Both analyses use machine learning techniques such as neural networks and boosted decision trees. With the full LHC Run 2 data set of 137 inverse femtobarns in hand, both analyses are expected to yield physics results that will be reported at conferences and in publications later this year.
For the past decade and a half, the LPC has been a venue for a vibrant and diverse community of researchers from the U.S. and international CMS community. The LPC supports a number of students, postdocs and faculty members at Fermilab, providing them resources to carry out physics analyses, to participate in detector design and production, and participate in software and computing activities. The LPC also excels at providing unique training opportunities, with over 70 events per year! This model is so effective that it is being replicated in the neutrino and cosmic domains. Although most students are from U.S. universities, a number of students come from abroad and are supported through the LPC Guest and Visitors Program, which furthers the community’s diversity of ideas and culture and diversity of physics output. More than half of all CMS publications include direct contributions from the research performed at the LPC.
In addition to working on physics analyses, Reham and Angela worked on testing prototype silicon sensors at the Fermilab SiDet Facility under the supervision of Fermilab scientist Lenny Spiegel. Final versions of these sensors will eventually be used in the construction of outer tracker modules for the high-luminosity upgrade of the CMS tracker. As part of the quality control process for module assembly, Reham and Angela checked the sensors that were received at Fermilab. These basic but critical tests, such as measuring the sensor current as a function of an applied voltage, help ensure that no damage has occurred in shipment and are a part of the sensor quality certification. It is a great training for students in the basic workings of semiconductor detectors. Angela has also worked at SiDet on testing of prototype tracker modules for CMS upgrade.
Angela was back last month at the LPC to assist courses at the annual CMS Data Analysis School. This year the DAS had a record attendance with 70 students and over 100 instructors. Both students plan to come back to the LPC for one or two more month-long visits before they complete their physics analyses using complete LHC Run 2 data sets, which will form the basis for their Ph.D. theses. See you soon, Reham and Angela!
Pushpa Bhat and Lenny Spiegel are Fermilab scientists on the CMS experiment.