CMS experiment (Dr.Demetris Loukas, Dr.G.Daskalakis, Dr.A.Kyriakis, Dr.G.Anagnostou, Mr.P.Asenov, Mrs.L.Paspalaki, Mr.Kazas)
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CMS is one of the two general-purpose experiments currently collecting and analysing data at the large hadron collider (LHC) at CERN.
The demokritos CMS group currently consists of 4 academics members of staff, 0 postdoctoral researchers, 1 engineer and 2 Ph.D. students.
We have been heavily involved in the construction and operation of the preshower detector. We are currently contributing to the upgrade of the CMS silicon tracker.
Our physics analyses are currently focused on searches for new particles.
Detector Development for the CMS Experiment
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The Preshower Detector
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The Preshower is the first part of the CMS endcap electromagnetic calorimeter, as seen by the particles. It is composed of 2 layers of lead absorbers followed by silicon sensors of a total surface of 17 m2 the biggest ever built. The use of the silicon strip sensors improves the spatial accuracy of the incidence position of electromagnetic showers. Our group has been involved in the following tasks:
– Design of the silicon sensors for the Preshower
– Development of prototype VLSI readout chip in submicron technology for the Preshower sensors
– Responsibility for the design and construction of one quarter (1000 modules) of the Preshower modules (sensors + electronics + mechanics)
– Co-coordination with CERN of the production in Greece of the entire number (5200) of the hybrid circuits housing the front end electronics of the CMS Preshower detector
(5200) of the hybrid circuits housing the front end electronics of the CMS
The Upgrade of CMS Tracker detector
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The CMS detector needs to be substantially upgraded during LS3 in order to exploit the increase in luminosity provided by the HL-LHC.
The increase in radiation levels requires improved radiation hardness, while the larger pileup and associated increase in particle density requires higher detector granularity to reduce occupancy, increased bandwidth to accomodate higher data rates, and improved trigger capability to keep the trigger rate at an acceptable level while not compromising physics potential.
The Phase-2 tracker will consist of an Inner Tracker (IT) based on silicon pixel modules and and Outer Tracker (OT) made from silicon modules with strip and macro-pixel sensors.
The tasks for our group are:
– Sensor quality control
– Process quality control
– Test beams
Analysis of CMS Data
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– Studies of Properties of the top quark (link)
Measurement of the cross-section of top quark pairs with additional jets.
– Searches for high mass resonances in the di-electron final state (link)
Many models designed to address the shortcomings of the SM predict such resonances at the TeV scale.
– Searches for Heavy Top Partners and Dark Matter @ the LHC (link)
A new generic search method for final states with 2 invisible particles applied to dark matter searches @ the LHC as well as searches for heavy top partners.
– Search for supersymmetric particles (link)
Final states with high-pT photons and significant missing energy emerge naturally from models of supersymmetry (SUSY) broken via gauge mediation.
Search for Supersymmetry in Events with photons and significant missing energy
The Standard Model (SM) of particle physics is the theory describing three of the four known fundamental forces. Although the Standard Model is believed to be self-consistent and has
demonstrated a huge success in providing experimental predictions, it leaves some phenomena such as netrino oscillation and the existence of dark matter unexplained.
Supersymmetry (SUSY) is a well-known beyond the standard model extension where every SM Particle has a superpartner. These superpartners would be new and undiscovered particles. The search of SUSY relies on the correct identification and reconstruction of final states that are described by a SUSY model. T5gg is a such a model that has two photons jets, and missing transverse energy coming from the undetected particle in the final state.
The search for this finals state was performed for data from proton- proton collisions that collected by the CMS detector in 2015 and 2016 at the center of mass energy of 13 TeV. This search will continue for data that are collected in 2017 and 2018.