N. Leonardo

The CMS detector will be upgraded for the HL-LHC to include a MIP Timing Detector (MTD). The MTD will consist of barrel and endcap timing layers, BTL and ETL respectively, providing precision timing of charged particles. The BTL sensors are based on LYSO:Ce scintillation crystals coupled to SiPMs with TOFHIR2 ASICs for the front-end readout. A resolution of 30-60 ps for MIP signals at a rate of 2.5 Mhit/s per channel is expected along the HL-LHC lifetime. We present an overview of the TOFHIR2 requirements and design, simulation results and measurements with TOFHIR2 ASICs. The measurements of TOFHIR2 associated to sensor modules were performed in different test setups using internal test pulses or blue and UV laser pulses emulating the signals expected in the experiment. The measurements show a time resolution of 24 ps initially during Beginning of Operation (BoO) and 58 ps at End of Operation (EoO) conditions, matching well the BTL requirements. We also showed that the time resolution is stable up to the highest expected MIP rate. Extensive radiation tests were performed, both with x-rays and heavy ions, showing that TOFHIR2 is not affected by the radiation environment during the experiment lifetime.

We review the results on the bottomonium system from the CMS experiment at the Large Hadron Collider. Measurements have been carried out at different center-of-mass energies in proton collisions and in collisions involving heavy ions. These include precision measurements of cross sections and polarizations, shedding light on hadroproduction mechanisms, and the observation of quarkonium sequential suppression, a notable indication of quark-gluon plasma formation. The observation of the production of bottomonium pairs is also reported along with searches for new states. We close with a brief outlook of the future physics program.

The Event Builder and Level 3 systems constitute critical components of the DAQ in the Collider Detector at Fermilab experiment. These systems are responsible for collecting data fragments from the Front End electronics, assembling the data into complete event records, reconstructing the events and forming the final trigger decision. With Tevatron Run IIa in progress, the systems have been running successfully at high throughput rates, the design utilizing scalable architecture and distributed event processing to meet the requirements. Brief descriptions of current performance in Run IIa and possible upgrade for Run IIb are presented.

The search for and study of flavor oscillations in the neutral BsBs meson system is an experimentally challenging task. It constitutes a flagship analysis of the Tevatron physics program. In this dissertation, they develop an analysis of the time-dependent Bs flavor oscillations using data collected with the CDF detector. The data samples are formed of both fully and partially reconstructed B meson decays: Bs → Dsπ(ππ) and Bs → Dslv. A likelihood fitting framework is implemented and appropriate models and techniques developed for describing the mass, proper decay time, and flavor tagging characteristics of the data samples. The analysis is extended to samples of B+ and B0 mesons, which are further used for algorithm calibration and method validation. The B mesons lifetimes are extracted. The measurement of the B0 oscillation frequency yields Δmd = 0.522 ± 0.017 ps-1. The search for Bs oscillations is performed using an amplitude method based on a frequency scanning procedure. Applying a combination of lepton and jet charge flavor tagging algorithms, with a total tagging power ϵ'D2 of 1.6%, to a data sample of 355 pb-1, a sensitivity of 13.0 ps-1 is achieved. They develop a preliminary same side kaon tagging algorithm, which is found to provide a superior tagging power of about 4.0% for the Bs meson species. A study of the dilution systematic uncertainties is not reported. From its application as is to the Bs samples the sensitivity is significantly increased to about 18 ps-1 and a hint of a signal is seen at about 175. ps-1. They demonstrate that the extension of the analysis to the increasing data samples with the inclusion of the same side tagging algorithm is capable of providing an observation of Bs mixing beyond the standard model expectation. They show also that the improved knowledge of Δms has a considerable impact on constraining the CKM matrix elements.

The decays Bs0→μ+μ− and B0→μ+μ− are highly suppressed in the standard model constituting sensitive probes of new physics. We present the results of a search for these rare decays in proton-proton collisions using the full data sample collected by the CMS experiment during LHC Run I. Through a fit to the dimuon invariant-mass spectrum, an excess of events with respect to the background is observed, compatible with the Bs0(B0) signal with a significance of 4.3 (2.0) standard deviations (σ). The measured branching fractions are B(Bs0→μ+μ−)=(3.0−0.9+1.0)×10−9 and B(B0→μ+μ−)=(3.5−1.8+2.1)×10−10. The combination of the CMS and LHCb results, using their full Run I data samples, yield an event excess compatible with the Bs0(B0) signal with a significance in excess of 6σ(3σ). The ongoing and projected accelerator and detector upgrades will allow to establish and to carry out precision measurements of both rare decays, and explore novel observables with further sensitivity to new physics effects.

Quarkonium hadroproduction is not satisfactorily understood.Measurements performed at the unprecedented LHC energies, and benefiting from large yields and extended kinematic reach, are anticipated to facilitate crucial improvements to the current understanding.This article presents the initial LHC quarkonium results, based on the data collected by the CMS experiment in the first year LHC pp and PbPb runs.