The beam tests of the CMS High Granularity Calorimeter and Constraints on lepton non-universality using the Higgs sector

by Geliang Liu (Laboratoire Leprince-Ringuet, École Polytechnique, France)

Tuesday 13 Jun 2023, 10:30 → 11:30 Asia/Shanghai

B105 (CHEP)

As part of the Phase-II upgrade of the CMS detector in preparation for the High Luminosity Large Hadron Collider (HL-LHC), the endcap calorimeters will be replaced by the High Granularity Calorimeter (HGCAL). The HGCAL will be the first calorimeter optimized for the particle-flow reconstruction at a colliding-beam experiment, providing 5-D information (space-time-energy) with very fine segmentation in both the longitudinal and transverse directions. The proposed design uses silicon sensors in the electromagnetic section and high-irradiation regions of the hadronic section, while in the low-irradiation region of the hadronic section plastic scintillator tiles equipped with silicon photomultipliers (SiPMs) are used. The performances of the prototype silicon modules were tested with electron and pion beams produced at the CERN SPS-H2 beamline in October 2021 and October 2022. The results from analyzing the beam test data are shown.

According to the standard model (SM), different generations of leptons have identical interactions with other particles (lepton universality), except the Higgs boson, with which the coupling strengths are proportional to the lepton masses. The branching fraction of the Higgs boson decaying to two muons divided by that of the Higgs boson decaying to two tau leptons will be measured to study and constrain the lepton non-universality, using the Run 2 data collected by the CMS detector. In order to control and systematic uncertainties, the trigger-and-probe (TnP) method at the analysis level is introduced, and a validation study with Z boson pair production is shown. The optimal analysis strategy to study the Higgs boson decays is introduced. Current work progress as well as following steps and prospects for the ongoing Run 3 is shown.

个人简介:
Geliang Liu is currently a PhD student at Laboratoire Leprince-Ringuet, École Polytechnique, France. He used to be an undergraduate student at the school of physics, Peking University from 2015 to 2019, and worked on searches for new physics at the BESIII experiment. From 2019 to 2021, he finished high-energy-physics master program at ETH Zürich and École Polytechnique  and worked on searches for a resonance decaying to two Higgs bosons in the bbττ final state in the CMS experiment. As a member of the CMS collaboration, currently he is working on the beam tests for the High Granularity Calorimeter as part of the Phase-II CMS detector upgrade  as well as the physics analysis to constrain lepton non-universality using the Higgs sector.