Nuclear Particle Physics and Physics Symposium – Ohannes Kamir Kossian; University of Iowa | Physics and astronomy

Nuclear Particle Physics and Physics Symposium – Ohannes Kamir Kossian;  University of Iowa |  Physics and astronomy

Nuclear Particle Physics and Physics Symposium - Ohannes Kamir Kossian;  Promotional photo for the University of Iowa

Find the Standard Model Higgs boson decaying into two muons, CMS HF M&O, and build a CMS Endcap timing layer for the CMS Phase II upgrade

Ohanas Qamar Kossian; University of Iowa

In the Standard Model (SM) of particle physics, the masses of fermions are determined by the strength of their coupling to the Higgs field. The decay rate of the Higgs boson into the fermion-antifermion pair is expected to be proportional to the fermion mass SM. Only 0.02% of the 125 GeV Higgs bosons decay to μ^+ μ^-, a very small percentage compared to 58.2% for bb ̅ and 6.3% for τ^+ τ^-. However, the small natural Higgs width (~4 MeV) combined with the excellent muon momentum resolution of the CMS will enable us to distinguish expected signal events versus massive amounts of background processes. The main background processes consist of high mass, extra-shell Z bosons that decay to μ^+ μ^- and leptonic decay tt̅. Measuring the cross section H → μ^+ μ^- will provide three unique investigations of the SM Higgs properties. First, it provides the only direct way to measure the strength of the Higgs-Muon Yukawa coupling and compare it to the muon mass.
Moreover, the ratio of the cross sections H→ μ^+ μ^- to H→ τ^+ τ^- will provide constraints on the proportionality of the Higgs couplings to fermions of different generations. The cross section H → μ^+ μ^- will also be of crucial importance for future lepton flavor violating H → μ τ searches.
The CMS collaboration placed a significant upper bound on the Higgs boson production times the H→ μ^+ μ^- branched cross-section at about twice the SM value using LHC collision data collected at √s = 7, 8 and 13 TeV center-of-mass energies.
The proposed search for H→ μ^+ μ^- will use collision events that will be recorded using the CMS detector during operation III. The result will be combined with data collected during Run I at √s = 7 and 8 TeV and Run II at √s = 13 TeV.

The Endcap Timing Layer (ETL) will be a first-generation, all-silicon-based subsystem covering the high eta region of the future CMS timing detector, which will be installed during the CMS Phase II upgrade project. The HL-LHC will operate at an instantaneous luminosity of 5×10^34 cm^(-2) s^(-1), with a projected total integrated luminosity of 3000 fb^(-1) by the end of the decade. To fully exploit these new conditions, the CMS detector will need an entirely new timing detector with higher radiation tolerance and timing capabilities. With this new timing detector, CMS will have the ability to accurately measure the minimum ionizing particle (MIP) production time. This will help solve the problem of simultaneous accumulation of approximately 200 collisions per transit group. The timing detector will consist of two sub-detectors, the barrel timing layer and the end cap timing layer. The ETL department uses Ultra-Fast Silicon Detectors (UFSDs) based on Low Gain Avalanche Detector (LGAD) technology. An automated bridge will be used at Fermilab during the assembly of the ETL modules containing the sensor and first stage for data acquisition. With a relative accuracy of up to 10 micrometers for component placement, the automated gantry will be crucial in achieving the required quality for the approximately 7,000 units planned for assembly. Once the critical components are placed in the unit, each unit will then be mechanically inspected before being transferred to the wiring harness, which proves the electrical connections within the unit. After attaching the wires, the bridge is used again to attach a ceramic cover plate to the sensor side of each module. The cover plate produces robust individual units that can be carried and handled without worrying about damaging the most important components, as well as providing a thermal path for the units.

Being located in the highest radiation zones of the CMS detector, the HF calorimeter is equipped with radiation damage monitoring systems. One such system consists of an LED driver and light distribution systems to monitor the gain and stability of the 4 anode PMTs installed during the HF-Phase I upgrades and a new online fiber radiation monitoring system. The concept of the new LED calibration module is based on a fast LED driver and control circuit located in the mezzanine mounted on the QIE board. The optics mix the light and distribute it to the photodetector. We take LED measurements at high and low intensities to monitor the behavior and stability of the 4-anode PMTs.

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