Radiation experience with the CMS pixel detector

The CMS pixel detector is the innermost component of the CMS tracker occupying the region around the centre of CMS, where the LHC beams are crossed, between 4.3 cm and 30 cm in radius and 46.5 cm along the beam axis. It operates in a high-occupancy and high-radiation environment created by particle collisions. Studies of radiation damage effects to the sensors were performed throughout the first running period of the LHC . Leakage current, depletion voltage, pixel readout thresholds, and hit finding efficiencies were monitored as functions of the increasing particle fluence. The methods and results of these measurements will be described together with their implications to detector operation as well as to performance parameters in offline hit reconstruction

Alignment of the CMS Tracking-Detector with First 2015 Cosmic-Ray and Collision Data

The performance of the CMS tracking-detector alignment with the first 2015 cosmic-ray data and proton-proton collision data at 13 TeV center-of-mass energy with the magnetic field at 0 T and 3.8 T is presented

Nuclear interaction study around beam pipe region in the Tracker system at CMS with 13 TeV data

Analysis is presented to study the material in the Tracker system with nuclear interactions from proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to an integrated luminosity of 7.3 pb−1 at a centre-of-mass energy of 13 TeV collected at 3.8 Tesla magnetic field. With reconstructed nuclear interactions we observe the structure of the material, including beam pipe, in the Tracker system

Nagyenergiás fizikai kutatások és fejlesztések a CERN-i LHC gyorsító CMS és a Brookhaven-i RHIC gyorsító PHENIX detektornál = High energy physics research and development at the LHC CMS (LERN) and RHIC PHENIX (BHL) detectors

Az OTKA által támogatott kutatás két területre bontható. I. A BNL RHIC gyorsítójának PHENIX kísérletében a mérésekben és a kísérleti adatok analízisében való részvétel: Csoportunk a PHENIX kollaboráció tagjaként dolgozott, munkája beépült a PHENIX kísérlet közös eredményeibe. Néhány területen a csoport hozzájárulása különösen jelentős volt. Igy kiemelendő a jet-elnyomás jelenségének vizsgálata különböző energiájú nehézion ütközésekben illetve az elektreomágneses kaloriméterrel kapcsolatos szimulációs és kalibrációs tevékenység. II. Részvétel a CERN-i LHC CMS kísérletének építésében, ezen belül a barrel müon kamrák helyzetmeghatározó rendszerének fejlesztése és létrehozása: a pályázati időszak alatt megépítésre került a teljes rendszer, amely lehetővé teszi a CMS barrel müon spektrométerét alkotó 250 nagyméretű driftkamra helyzetének meghatározását szubmilliméteres pontossággal. | The research activity supported by the OTKA fund can be divided in two groups. I. Participation in the measurements and the physics analysis of the PHENIX experiment at the RHIC accelerator in BNL (USA): our group worked in close collaboration with other members of the experiment so its work was integrated in the common results of the whole collaboration. In some areas, however, the contribution was particularly significant. Two areas can be emphasized, the investigation of jet suppression in heavy ion collisions at different energies and the simulation and calibration of the electromagnetic calorimeter. II. Participation in the construction of the CMS experiment to be installed at the LHC accelerator (CERN, Switzerland), development and construction of the barrel muon position monitoring system: the full system has been completed during the period of the OTKA-support. It allowes us to determine the positions of 250 large-scale drift-chambers forming the barrel muon spectrometer with submillimeter accuracy

Search for new phenomena in events with high jet multiplicity and low missing transverse momentum in proton–proton collisions at

A dedicated search is presented for new phenomena in inclusive 8- and 10-jet final states with low missing transverse momentum, with and without identification of jets originating from b quarks. The analysis is based on data from proton–proton collisions corresponding to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC at √s = 8 TeV. The dominant multijet background expectations are obtained from low jet multiplicity control samples. Data agree well with the standard model background predictions, and limits are set in several benchmark models. Colorons (axigluons) with masses between 0.6 and 0.75 (up to 1.15) TeV are excluded at 95% confidence level. Similar exclusion limits for gluinos in R-parity violating supersymmetric scenarios are from 0.6 up to 1.1 TeV. These results comprise the first experimental probe of the coloron and axigluon models in multijet final states. © 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY licenseL

Simulation of the dynamic inefficiency of the CMS pixel detector

The Pixel Detector is the innermost part of the CMS Tracker. It therefore has to prevail in the harshest environment in terms of particle fluence and radiation. There are several mechanisms that may decrease the efficiency of the detector. These are mainly caused by data acquisition (DAQ) problems and/or Single Event Upsets (SEU). Any remaining efficiency loss is referred to as the dynamic inefficiency. It is caused by various mechanisms inside the Readout Chip (ROC) and depends strongly on the data occupancy. In the 2012 data, at high values of instantaneous luminosity the inefficiency reached 2% (in the region closest to the interaction point) which is not negligible. In the 2015 run higher instantaneous luminosity is expected, which will result in lower efficiencies; therefore this effect needs to be understood and simulated. A data- driven method has been developed to simulate dynamic inefficiency, which has been shown to successfully simulate the effects