Welcome on CMS IPHC's webpages!
The Institut Pluridisciplinaire Hubert Curien (IPHC) Strasbourg group has been involved in the CMS Tracker since the beginning, in 1992. Until 1999, our contribution was dedicated to MicroStrip Gas Chambers (MSCG) for the forward Tracker, having a leading and coordination role in the design, construction and prototype tests. After the choice of a full silicon Tracker in 2000, the group was responsible for the design and production of the front-end hybrids, of the design of the online database, of the online diagnostic system and of the control/command framework for the whole micro-strip Tracker. The group was also in charge of the assembly of a large part of a Tracker endcap and was responsible for the final functionality tests of the Tracker petals. After the installation of the Tracker in late 2006, IPHC has continued to be involved in the Tracker operations and improvements. In particular, we had the responsibility of the firmware for the current (Phase 1) pixel detector installed in 2017, we worked on the simulation of the micro-strip response and we measure its radiation hardness with collision data. From 2007, in order to contribute to the data analysis, Strasbourg hosts a Tier-2 centre for the Worldwide LHC Computing Grid.
Since Run 1, the team has a strong expertise and a longstanding experience in b-tagging and tau-identification, employed in many LHC data analyses. Recently it has contributed to several HL-LHC b-tagging and tau-identification developments, documented in the Phase 2 TDRs. Two members of the team were co-conveners of the b-tagging group (2012-2013, 2015-2017), one member is co-convener of the tau-identification since September 2021.
A summary of recent contributions can be found below.
Higgs boson and Standard Model measurements
The team contributed to the first evidence of the Higgs boson coupling to the top quark established by the CMS Collaboration in the multilepton channel. In addition, we contributed to several Standard Model precision measurements, in particular to searches for tZ flavour changing interactions and first evidence of the tZ process. Since then, the team is further involved in Higgs boson characterization measurements, namely the measurement of the Higgs boson produced in association with a single top quark (tH), and the first search at LHC for CP violation in the tau Yukawa coupling. The team deployed matrix element techniques for the tH and ttH measurements, developed the polarimetric vector method for Higgs CP search, and employs optimal observables characterizing the tau lepton helicities to measure the effective weak mixing angle in Z→ττ decays.
Beyond Standard Model searches
The team is involved, since Run 1, in searches for the supersymmetric superpartner of the top quark (stop), which lead to continuous improvements on the limits on the stop mass. The one-lepton channel analysis, to which the team contributed, based on the data collected in 2016 during Run 2, improved the upper limit of the stop mass by ~400 GeV with respect to Run 1. The team pursues its searches for new physics by looking for Heavy Stable Particles (HSCP) and long lived top quarks (LLP) stemming from supersymmetric particles.
HSCP may arise from Long-lived top squarks forming bound states, R-hadrons, expected to cross the entire tracker. The experimental signature would be a large transverse momentum track, characterized by a low relativistic factor beta (~ 0.3-0.9) inducing a large energy deposit in the tracker (dE/dX) and a large time of flight in the outer layers, mainly in the muon chambers.
Tracker upgrades for HL-LHC
The team is involved in the construction of part of the HL-LHC’s outer tracker TB2S detector (made of double sided microstrips sensors), through the design and construction of the mechanical structure of its wheel, and installation of the pT modules in its ladders. One member of the team is co-convener of the TB2S construction. The Engineering Design Review, including IPHC’s contributions, has successfully been passed in December 2021.
The team contributed to the first realistic demonstration of a silicon tracking module that is capable to reconstruct tracks, down to 2 GeV with sharp turn-ons]], as expected to be used at CMS HL-LHC’s first trigger level. The data acquisition of these test beams carried out at DESY relied on the DAQ developments made at IPHC for the CMS Phase-1 Pixel detector. The team carried out these test beams and analyzed the data. The team pursues nowadays campaigns at IPHC’s Cyrcé beamline to further test the 2S modules together with the DAQ.