Observation of tW production in the single-lepton channel in pp collisions at root s=13 TeV

A measurement of the cross section of the associated production of a single top quark and a W boson in final states with a muon or electron and jets in proton-proton collisions at root s = 13 TeV is presented. The data correspond to an integrated luminosity of 36 fb(-1) collected with the CMS detector at the CERN LHC in 2016. A boosted decision tree is used to separate the tW signal from the dominant t (t) over bar background, whilst the subleading W+jets and multijet backgrounds are constrained using data-based estimates. This result is the first observation of the tW process in final states containing a muon or electron and jets, with a significance exceeding 5 standard deviations. The cross section is determined to be 89 +/- 4 (stat) +/- 12 (syst) pb, consistent with the standard model.Peer reviewe

Primary Vertex Reconstruction for Upgrade at LHCb

The aim of the LHCb experiment is the study of beauty and charm hadron decays with the main focus on CP violating phenomena and searches for physics beyond the Standard Model through rare decays. At the present, the second data taking period is ongoing, which is called Run II. After 2018 during the long shutdown, the replacement of signicant parts of the LHCb detector is planned. One of main changes is upgrade of the present software and hardware trigger to a more rapid full software trigger. Primary Vertex (PV) is a basis for the further tracking and it is sensitive to the LHC running conditions, which are going to change for the Upgrade. In particular, the center-of-mass collision energy should reach the maximum value of 14 TeV. As a result the quality of the reconstruction has to be studied and the reconstruction algorithms have to be optimized

Measurements and estimates of the radiation levels in the CMS Experimental Cavern using Medipix and RAMSES monitors, and the FLUKA Monte Carlo code

Highlights of the work performed for the BRIL project which include FLUKA simulations, background measurements and investigations, and benchmarking activities. Activation simulations with a simple fix for the well known silver isomer problem in FLUKA were performed for the tracker bulkhead region and compared with measurements of the residual dose rates taken in (E)YETS 17/18. Measurements from the RAMSES monitors are compared with FLUKA predictions for the mixed radiation field. Using non-standard FLUKA output, timing information for simulated particles arriving at ME4/2 have been produced with an extensive simulation run. First analysis has been performed, demonstrating how the information can be used to help determine the source of background and support future shielding studies. Changes in the year to year RAMSES readings are investigated to understand the effect of various shielding elements added. Lastly, the Medipix based neutron camera was investigated to obtain the neutron flux

Fast Beam Condition Monitor of the CMS experiment at the HL-LHC

To achieve the challenging target of $1\%$ precision on luminosity determination at the high-luminosity LHC (HL-LHC) with an instantaneous luminosity of up to $7.5 \times \rm 10^{34} cm^{-2} s^{-1}$, the CMS experiment will employ multiple luminometers with orthogonal systematics. A key component of the proposed system is a stand-alone luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent from the central trigger and data acquisition services and able to operate at all times at 40 MHz providing bunch-by-bunch luminosity measurement with 1 s time granularity. FBCM is foreseen to be placed inside the cold volume of the Tracker as it utilizes silicon-pad sensors exploiting the zero-counting algorithm for luminosity measurement. FBCM will also provide timing information with a few ns precision enabling the measurement of beam induced background. We report on the optimisation of the design and the expected performance of FBCM

Upgraded CMS Fast Beam Condition Monitor for LHC Run 3 Online Luminosity and Beam Induced Background Measurements

The fast Beam Condition Monitor (BCM1F) for the CMS experiment at the LHC was upgraded for precision luminosity measurement in the demanding conditions foreseen for LHC Run 3. BCM1F has been rebuilt with new silicon diodes, produced on the CMS Phase 2 Outer Tracker PS silicon wafers. The mechanical structure was adapted to include a 3D printed titanium circuit for active cooling of BCM1F sensors. The assembly and qualification of the detector quadrants were followed by the integration with Pixel Luminosity Telescope and Beam Conditions Monitor for Losses on a common carbon fibre carriage. This carriage was installed inside the CMS behind the Pixel detector, 1.9 m from the Interaction Point. BCM1F will provide a real-time luminosity measurement as well as a measurement of the beam-induced background, by exploiting the arrival time information of the hits with a sub-bunch crossing precision. Moreover, regular beam overlap scans at CMS were introduced during Run 2, enabling an independent and non-destructive transverse profile measurement for LHC Operators. The paper describes the improved BCM1F detector design, its commissioning and performance during the beginning of Run 3 operation

Primary Vertex Reconstruction for Upgrade at LHCb

in preparatio

BRIL LS2 Activity: PLT & BCM1f Integration

Integration of first PLT+BCM1f quadrant

Beam-beam interaction-induced bias to precision luminosity measurement

The mutual electromagnetic interaction between counter-rotating bunches crossing at the interaction points (IPs) of a particle collider has been studied since the dawn of the storage-ring era. It can result in a significant bias to absolute-luminosity calibrations determined by the van der Meer (vdM) method. Numerical models developed to study such beam—beam-induced biases at a single IP of the Large Hadron Collider (LHC) have been recently extended to better account for actual operating conditions, such as head-on collisions at non-scanning IPs during vdM scans, or scans performed during physics data-taking using higher-brightness beams than used during vdM-calibration sessions.As part of a long-term effort aimed at quantifying the beam-beam bias to luminosity-related observables in hadron colliders, in this paper we compare results from a dedicated beam-beam experiment performed at the LHC in 2022 to the predictions of the numerical model. We also report some preliminary observations about the impact of the beam-beam interaction on the instantaneous luminosity during physics operation, and investigate beam-beam contributions to the apparent non-linearity and overall stability of experimental luminometers during physics data taking