Recommendation for Alejandro For LPC Distinguished Researcher
Dear Colleagues,
I am writing to recommend Alejandro Espinosa for the CMS LPC Distinguished Researcher program. Alejandro is a postdoc in my group, focusing on HH→4b and on extending the jet calibration to low pT (~10 GeV). He has been an invaluable asset to our group and is excited about this opportunity.
Alejandro is well qualified for this role: he is already collaborating closely on a physics analysis with members of LPC, has exciting new ideas for expanding the CMS DAS, and has a plan for getting involved in the CMS upgrade that would be a significant benefit to FNAL and the US upgrade project.
Work to date
My group works closely with Jaco Konigsberg (FNAL XXX) on HH→4b analyses. We are currently performing a search for HH→4b production using Run 2 + ('22+'23) data. Alejandro performed the Run 2 analysis and is responsible for the final combination. This paper is expected out later this year and will have a combined limit of ~4 times the SM prediction (more than twice as sensitive as the previous result).
In addition to HH→4b, Alejandro is also working with my student (Aniket Khanal) on reducing jet pT threshold in HH→bbWW*. We have demonstrated that—due to the off-shell W* in the Higgs boson decay—lowering the threshold from the nominal value of 25 GeV to 10 GeV doubles the signal acceptance. Alejandro is responsible for extending the jet calibration below 25 GeV, which is the current threshold for the calibration provided by the CMS POG.
Alejandro is a natural leader. At CMU, we have a large CMS group with four active faculty members supervising over a dozen students engaged in a wide range of analyses. Our group has made a concerted effort to coordinate all analyses around the use of coffea. Alejandro serves as our point person for onboarding students and new postdocs. He has been integral in both shaping the overall software structure and providing ongoing support to our codebase's users.
Alejandro is active on the Coffea, CAT, and REANA Mattermost channels (username: algomez) and has developed several tutorials focused on Coffea. Recently, he led the CMSDAS/HATS jet tutorials [1], where he migrated an older C++/Python-based tutorial to use Coffea. He has also developed a Snakemake/REANA tutorial [2], which he presented at a CAT hackathon.
Plan for LPC DR
Alejandro has ambitious plans for his time at the LPC. On the analysis side, my group will continue collaborating on HH→4b. We are currently planning the analysis with the full Run-3 dataset. Alejandro will continue to play a leading role in this effort.
In addition, he has a compelling idea for extending the analysis to target the low-mHH region using low-pT jets. In the current HH4b analysis, acceptance at low mHH is limited by jet pT thresholds imposed by the trigger. These lower mHH events are especially valuable as this phase space is the most sensitive to the Higgs self-coupling. The current analysis requires that the b-tagged jets from the Higgs satisfy the trigger thresholds. Alejandro's idea is to search for HH→4b + ISR/FSR jet where the additional jet satisfies the trigger criteria. This would allow us to recover events in which the lowest b-jet is below the trigger requirement. A preliminary proof-of-concept study suggests that the acceptance at low mHH can be doubled by lowering the threshold on the softest b-jet to 15 GeV. This proposed work naturally complements both the existing HH→4b analysis and his jet calibration work in HH→bbWW. Constraining the self-coupling is a flagship CMS result where it is important that USCMS and Fermilab have a leading role.
On the educational front, Alejandro has plans for developing his Snakemake/REANA tutorial into a Hands-on Advanced Tutorial Sessions (HATS) on reproducible analysis workflows. This will show students modern programming practices, including continuous integration (CI), extensive use of unit tests, and regular result replication with REANA. These practices make the codebase more robust, the entire team more productive, and provide students with valuable experience transferable beyond HEP.
The other major component of Alejandro's LPC residency will be devoted to HGCAL upgrade work at the Fermilab Cassette Assembly Facility (CAF). Involvement in the HGCAL is a natural fit for Alejandro. CMU serves as a Module Assembly Center (MAC); my group assembles and tests silicon modules for the HGC that are then sent to the Fermilab CAF. Alejandro proposes to work at the Fermilab CAF, collaborating with Zoltan Gecse and Don Lincoln to integrate module testing and commissioning into cassette assembly. Aniket Khanal is developing the testing software to be used at both the MAC and the Fermilab CAF. As mentioned above, Alejandro is already working closely with Aniket on bbWW, so it is natural to extend this collaboration to the upgrade project. Increasing the bandwidth between the MAC and the CAF will be critical to the project's success. Alejandro is perfectly suited for this role. The LPC DR program provides a natural bridge between these assembly centers.
In summary, I believe Alejandro would be an excellent fit for this position. He brings the required experience and enthusiasm, and his current work and proposed program aligns well with the position’s goals. As PI, I would fully support Alejandro in this role with my group's resources and graduate students. This opportunity aligns well with my group’s priorities, and I am confident that Alejandro’s contributions will make a substantial impact.
john