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Electrical QC Testing of Pixel Modules in the ATLAS Inner Tracker Upgrade for the HL-LHC
No full textThe upgrade Inner Tracker (ITk) for the ATLAS detector in the HL-LHC era is in its production phase. About 10000 hybrid pixel modules will be produced for the pixel detector in this all-silicon tracker. The electrical performance of these modules during quality control (QC) is assessed on the 3D and planar sensors, the RD53 frontend chip and on the module as a whole. A pixel module consists of 3 or 4 frontend chips. The interplay between the chips is derived from first principle and is evaluated during QC on the testbench. In addition to the typical leakage current measurement and chip calibration and tuning, our QC also tests the novel features of this chip that allows to minimise the radiation length of the detector. These features include the shunt-LDO (SLDO) circuit which enables powering of multiple modules in a serial chain and on-detector data aggregation. The assembly and testing of these modules are performed at about 25 sites worldwide, thus it is of utmost importance to ensure the consistency and uniformity of the testing procedures. For this purpose, we have developed a modular testing suite based on python that is easily installed and automates tasks like interacting with the production database, conducting tests with pre-defined procedures, interpreting the measurements and the creation of a test report
First HGCAL Absorber Plates arrive at CERN
No full textThese key components of the future HGCAL detector were produced and tested in Pakistan, and have now been delivered to the CMS site at the LHC Point 5 in Cessy, France. They will be assembled to create the supporting structure of the sub-detector, into which the HGCAL cassettes will be inserted
Search for long-lived particles using displaced vertices with low-momentum tracks in proton-proton collisions at 13 TeV
No full textA search for long-lived particles using final states including a displaced vertex with low-momentum tracks, large missing transverse momentum, and a jet from initial-state radiation is presented. This search uses proton-proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2017 and 2018, with a total integrated luminosity of 100 fb. This analysis adopts specific supersymmetric (SUSY) coannihilation scenarios as benchmark signal models, characterized by a next-to-lightest SUSY particle (NLSP) with a mass difference of less than 25 GeV relative to the lightest SUSY particle, assumed to be a bino-like neutralino. In the top squark () NLSP model, the NLSP is a long-lived , while in the bino-wino NLSP scenario, the mass-degenerate NLSPs are a wino-like long-lived neutralino and a short-lived chargino. The search excludes top squarks with masses less than 400-1100 GeV and wino-like neutralinos with masses less than 220-550 GeV, depending on the signal parameters, including the mass difference, mass, and lifetime of the long-lived particle. It sets the most stringent limits to date for the and bino-wino NLSP models.A search for long-lived particles using final states including a displaced vertex with low-momentum tracks, large missing transverse momentum, and a jet from initial-state radiation is presented. This search uses proton-proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2017 and 2018, with a total integrated luminosity of 100 fb. This analysis adopts specific supersymmetric (SUSY) coannihilation scenarios as benchmark signal models, characterized by a next-to-lightest SUSY particle (NLSP) with a mass difference of less than 25GeV relative to the lightest SUSY particle, assumed to be a bino-like neutralino. In the top squark () NLSP model, the NLSP is a long-lived , while in the bino-wino NLSP scenario, the mass-degenerate NLSPs are a wino-like long-lived neutralino and a short-lived chargino. The search excludes top squarks with masses less than 4001100 GeV and wino-like neutralinos with masses less than 220550 GeV, depending on the signal parameters, including the mass difference, mass, and lifetime of the long-lived particle. It sets the most stringent limits to date for the and bino-wino NLSP models
The size of the quark-gluon plasma in ultracentral collisions: impact of initial density fluctuations on the average transverse momentum
No full textRecent experiments have shown that the mean transverse momentum of outgoing particles increases as a function of the particle multiplicity in ultracentral nucleus-nucleus collisions at collider energies. This increase was originally predicted on the basis of simulations where the multiplicity increase occurred at constant volume, so that it implied a larger density and temperature. However, recent state-of-the-art simulations have shown that, for some models of initial condition, the volume may vary with the multiplicity in ultracentral collisions. We elucidate this effect by analytically relating the variation of the volume to the radial distribution of the one- and two-point functions of the fluctuating density field. We show that the volume variation is small if the total entropy of the ultracentral collisions scales with the mass number of the colliding isotopes. We argue that probing detailed transverse distributions of initial-state fluctuations through the ultracentral has nontrivial implications for models of nuclear structure and of the pre-equilibrium stages
Yield and performance validation of the Monolithic Stitched Sensor (MOSS), the first wafer-scale prototype for the ALICE ITS3 upgrade
No full textThe ALICE Inner Tracking System upgrade (ITS3) will employ stitched, wafer-scale Monolithic Active Pixel Sensors (MAPS) for the first time in high-energy physics, achieving a material budget of only 0.09%X per layer. Its first stitched prototype, the Monolithic Stitched Sensor (MOSS), underwent serial testing confirming sensor yield compliance with ITS3 requirements. In-beam tests show the device meets the ITS3 efficiency requirement of >99% while maintaining a fake-hit rate below 0.1hits/pixel/s, with performance sustained up to irradiation levels of 4kGy and 1MeVncm. The sensor demonstrates excellent charge-collection properties and linearity between time-over-threshold and deposited energy in the 1.8 - 6.5keV range in response to soft X-ray emissions. This article provides an overview of the validation steps and characterisation results
Associated production of Psi(2S) and Phi in diffractive proton-proton collisions at the LHCb experiment
No full textThe LHCb detector, with its forward rapidity coverage, can probe kinematic regions at low Bjorken-x as low as . This unique capability, combined with excellent momentum resolution, vertex reconstruction, and particle identification, enables precision measurements at low transverse momentum and forward rapidity. Studies of associated production of and in diffractive proton-proton collisions at the LHCb experiment will be discussed. At LHC energies, investigations of diffractive events provide valuable insights into QCD phenomena. These include understanding the characteristics of pomerons and exotic hadronic states, as well as examining low-x gluon distributions and the effects of saturation