# Harvard ATLAS Group Harvard ATLAS group, led by Profs. Melissa Franklin, John Huth, and Masahiro Morii, conduct a broad research program using the high-energy proton-proton collisions created by the Large Hadron Collider. The group has been responsible for the initial construction and the later upgrade of the ATLAS end-cap muon spectrometer, and continues to play a leading role in its trigger and the data-acquisition systems. The group members take on many challenging data-analysis projects, including precision measurements of the Standard Model processes, studies of the properties of the Higgs boson, and searches for new particles predicted by new theories beyond the Standard Model. In anticipation of the LHC's luminosity upgrade, the group is contributing to the upgrade of the ATLAS Inner Tracker. ## Faculty [### Melissa Franklin ](/people/melissa-franklin) Mallinckrodt Professor of Physics ![franklin_sm.png](/sites/g/files/omnuum1766/files/styles/hwp_4_5__690x865/public/lppc/files/franklin_sm.png?itok=zO5glLs2) [### John Huth ](/people/john-huth) Donner Professor of Science ![huth_sm.png](/sites/g/files/omnuum1766/files/styles/hwp_4_5__690x865/public/lppc/files/huth_sm.png?itok=toQdVtDU) [### Masahiro Morii ](/people/masahiro-morii) Donner Professor of Science ![morii_sm.png](/sites/g/files/omnuum1766/files/styles/hwp_4_5__690x865/public/lppc/files/morii_sm.png?h=ced7abb8&itok=kXbIcqEj) ## Postdoctoral Fellows [### Simone Francescato ](/people/simone-francescato-0) ## Graduate Students [### Arthur Alves ](/people/arthur-alves) [### Laura Bruce ](/people/laura-bruce) [### Santiago Cane ](/people/santiago-cane) [### Aidan Chambers ](/people/aidan-chambers) [### Ismail Elmengad ](/people/ismail-elmengad) [### Michael Farrington ](/people/michael-farrington) [### Sam Ferraro ](/people/sam-ferraro) [samuel\_ferraro@g.harvard.edu](mailto:samuel_ferraro@g.harvard.edu) [### Tate Flicker ](/people/tate-flicker) [### Jerry Ling ](/people/jiahong-jerry-ling) [### Alexis Mulski ](/people/alexis-mulski) ## Ongoing Detector Projects ### New Small Wheel (NSW) data-acquisition (DAQ) system expand\_more People involved and a short explanation of the project. ### New Small Wheel (NSW) trigger expand\_more People involved and a short explanation of the project. ### Inner Tracker (ITk) upgrade expand\_more **PI:** Masahiro Morii **Students and postdocs:** Kees Benkendorfer, Laura Bruce, Michael Farrington The ATLAS Inner Tracker (ITk) upgrade aims to replace the current inner tracking system of ATLAS with a new all-silicon detector. We are targeting installation in ~2030, in time for the high-luminosity upgrade of the LHC (HL-LHC). The new detector will have finer granularity than the current inner tracker, which will be necessary to distinguish tracks in the high-pileup, high-multiplicity environment of the HL-LHC. The design, intended to minimize the amount of non-sensing material in the system, pushes the state of the art of particle detector construction, thereby presenting many challenges and opportunities for students to learn. ITk is divided into two subsystems: silicon strips, and silicon pixels. The Harvard group is focused on the silicon strips. Our group has recently contributed to detector integration at CERN, the detector control system (DCS), and the data acquisition (DAQ) software. The team's hardware work is conducted in a cleanroom at CERN, and the software work is done remotely. ![Laura and Kees standing in front of three ITk staves](/sites/g/files/omnuum1766/files/styles/hwp_1_1__720x720_scale/public/2024-11/IMG_1625.jpeg?itok=fCZzDU7P) ## Ongoing Physics Analyses ### Measurement of Standard Model WVZ production expand\_more People involved and a short explanation of the physics. ### Search for long-lived particles with dE/dx and time-of-flight expand\_more PI: Melissa Franklin. Graduate students: Alexis Mulski, Ismail Elmengad ### Search for long-lived particles with secondary vertices and muons expand\_more People involved and a short explanation of the physics. ### Search for di-b-jet resonances with a trigger-level analysis expand\_more People involved and a short explanation of the physics. ### Measurement of ttZ production and EFT interpretation expand\_more **PI:** Masahiro Morii **Students and postdocs:** Kees Benkendorfer, Knut Zoch The existence of BSM physics at high scales can affect physical observations at lower scales --- an example is the existence of the *W* boson, which mediates beta decay even though it is too heavy to be produced directly by the energy of nuclear transitions. If we frame the Standard Model (SM) as a low-energy effective theory that lacks a full description of physics at higher energies, we can systematically categorize most possible effects of higher-scale physics on the production rates of SM particles through a framework called Standard Model Effective Field Theory (SMEFT). A large and growing program is underway to measure SMEFT parameters at the LHC. One process that is highly sensitive to many EFT parameters is *ttZ* --- the production of a top-antitop pair in association with a *Z* boson. This is a naturally high-energy process, which makes it very sensitive to effects from high-scale particles. We aim to enhance the EFT sensitivity even further by performing measurements in a regime where the tops recoil off of the *Z* and are highly boosted. This analysis will be the first measurement of *ttZ* production at 13.6 TeV, and in addition to the EFT interpretation, we aim to provide useful differential observables to be used for Monte Carlo developments. ## Recent Publications Selected ATLAS publications our group members have produced. Sort Title Journal citation Publication date arXiv reference Search for top-philic heavy resonances in pp collisions at sqrt(s) = 13 TeV with the ATLAS detector Eur. Phys. J. C 84:157 February 2024 arXiv:2304.01678 [hep-ex] Search for heavy, long-lived, charged particles with large ionisation energy loss in pp collisions at √s = 13 TeV using the ATLAS experiment and the full Run 2 dataset JHEP 06(2023)158 June 2023 arXiv:2205.06013 [hep-ex] Observation of four-top-quark production in the multilepton final state with the ATLAS detector Eur. Phys. J. C 83:496 June 2023 arXiv:2303.15061 [hep-ex] Measurement of Higgs boson decay into b-quarks in associated production with a top-quark pair in pp collisions at √s = 13 TeV with the ATLAS detector JHEP 06(2022)097 June 2022 arXiv:2111.06712 [hep-ex] Measurement of the tttt production cross section in pp collisions at √s = 13 TeV with the ATLAS detector JHEP 11(2021)118 November 2021 arXiv:2106.11683 [hep-ex] Search for Displaced Leptons in √s = 13 TeV pp Collisions with the ATLAS Detector Phys. Rev. Lett. 127:051802 July 2021 arXiv:2011.07812 [hep-ex] A search for the decays of stopped long-lived particles at √s = 13 TeV with the ATLAS detector JHEP 07(2021)173 July 2021 arXiv:2104.03050 [hep-ex] ## Resources For ATLAS Students [ Getting Started at CERN arrow\_circle\_right ](https://docs.google.com/document/d/1X3D83bDrsoyOY7mvHXB3IdSlE7I4tsRpo2BF2DxpRgk/edit?usp=sharing) [ Travel Policy arrow\_circle\_right ](https://osp.finance.harvard.edu/sponsored-travel-guidance)