P. Bortignon

We investigate the consequences of anharmonic terms in the vibrational spectrum of giant dipole resonances for the double Coulomb excitation of such modes in relativistic heavy-ion collisions. It is found that apparent discrepancies between the results of two separate experiments can be put in harmony assuming minor departures from the harmonic limit because of the special features of the reaction mechanism.

With the accumulation of large collision datasets at a center-of-mass energy of 13 TeV, the LHC experiments can search for rare processes, where the extraction of signal events from the copious Standard Model backgrounds poses an enormous challenge. Multivariate techniques promise to achieve the best sensitivities by isolating events with higher signal-to-background ratios. Using the search for Higgs bosons decaying to two muons in the CMS experiment as an example, we describe the use of Boosted Decision Trees coupled with automated categorization for optimal event classification, bringing an increase in sensitivity equivalent to 50% more data.

Secondary science education is vital, not only for students considering careers in science and technology-based fields, but for everyone. Its methodology teaches us how to extract information from the world around us and to find pertinent solutions to complex problems. Unfortunately, current curricula often end at the physics of the beginning of the twentieth century, only touching on relativity and quantum mechanics. Yet, we have come far since then and current advances, including the discovery of the Higgs boson and gravitational waves, present exciting concepts that can ignite the interest of students, while still teaching them the fundamentals of physics. This chapter attempts to address this century-long gap in science education. It begins with a recap of the history of the atom which, for centuries, was considered the fundamental building block of matter. We then describe how exploring the details of the atom led us to realise that our understanding of physics at those dimensions required a rethink. From there, we describe our journey down the subatomic rabbit hole, discovering, organising, and re-organising the microscopic world of elementary particles until arriving at an understanding that is central to today’s research, the Standard Model. From there, we present the shortcomings of that model and pose questions we are striving to answer. We hope this chapter will spark the interest of science teachers, so that they too can pass the excitement of this research on to their students, the discoverers and inventors of tomorrow.

After the Long Shutdown 1 (LS1) LHC will run at a center of mass energy of 13 TeV, providing CMS with proton collisions at an expected luminosity which is almost double the LHC design value of 1034cm−2s−1, and almost three times the peak luminosity reached during Run1 of 7.7·1033cm−2s−1. The higher luminosity and center of mass energy of the LHC will raise the Level 1 (L1) muon trigger rate by almost a factor six for a given muon transverse momentum pT threshold. It is therefore necessary to increase the muon (pT) threshold to keep the trigger rate below 100 kHz, the maximum sustainable rate for the CMS detectors. An increase of the L1 trigger thresholds implies a lowering of the efficiency in detecting signals from new physics. The CMS muon trigger is upgraded using custom designed AMC boards, with more powerful FPGAs and larger memories. The upgraded CMS muon trigger system implements pattern recognition and MVA (Boosted Decision Tree) regression techniques in the trigger boards for muon pT assignment, drastically reducing the trigger rate and improving the trigger efficiency. The upgraded system design exploits the redundancy of the CMS muon detectors at a very early stage merging different muon detector information already at L1. The pileup subtracted information from the upgraded calorimeter trigger allows to require isolated muons already in the L1 algorithms. The upgrade trigger is also designed to include inputs from GEM, the phase 2 muon detector upgrade in the very high pseudorapidity region.

The non-linearity in the space-drift time relation of the DT drift cell, as a function of the track angle, has been measured using cosmic ray data. The improvement obtained in the track reconstruction precision is presented.

The latest results of the measurement of the Higgs boson decaying to bottom quark pair are presented in this proceedings. The analyses are performed using data collected with the CMS experiment in 2016 and 2017 at the LHC from pp collisions at centre-of-mass energies of 13 TeV.