P. Ronchese

The muon tomography technique, based on multiple Coulomb scattering of cosmic ray muons, has been proposed as a tool to detect the presence of high density objects inside closed volumes. In this paper a new and innovative method is presented to handle the density fluctuations (noise) of reconstructed images, a well known problem of this technique. The effectiveness of our method is evaluated using experimental data obtained with a muon tomography prototype located at the Legnaro National Laboratories (LNL) of the Istituto Nazionale di Fisica Nucleare (INFN). The results reported in this paper, obtained with real cosmic ray data, show that with appropriate image filtering and muon momentum classification, the muon tomography technique can detect high density materials, such as lead, albeit surrounded by light or medium density material, in short times. A comparison with algorithms published in literature is also presented.

The 40 MHz bunched muon beam set up at CERN was used in May 2003 to make a full test of the drift tubes local muon trigger. The main goal of the test was to prove that the integration of the various devices located on a muon chamber was adequately done both on the hardware and software side of the system. Furthermore the test provided complete information about the general performance of the trigger algorithms in terms of efficiency and noise. Data were collected with the default configuration of the trigger devices and with several alternative configurations at various angles of incidence of the beam. Tests on noise suppression and di-muon trigger capability were performed.

Knowing the distribution of the materials in the blast furnace (BF) is believed to be of great interest for BF operation and process optimization. In this paper calibration samples (ferrous pellets and coke) and samples from LKAB’s experimental blast furnace (probe samples, excavation samples and core-drilling samples) were measured by the muon scattering tomography detector to explore the capability of using the muon scattering tomography to image the components in the blast furnace. The experimental results show that it is possible to use this technique to discriminate the ferrous pellets from the coke and it is also shown that the measured linear scattering densities (LSD) linearly correlate with the bulk densities of the measured materials. By applying the Stovall’s model a correlation among the LSD values, the bulk densities and the components of the materials in the probe samples and excavation samples was established. The theoretical analysis indicates that it is potential to use the present muon scattering tomography technique to image the components in various zones of the blast furnace.

A prototype of the CMS Barrel Muon Detector incorporating all the features of the final chambers was built using the mass production assembly procedures and tools. The performance of this prototype was studied in a muon test beam at CERN and the results obtained are presented in this paper.

In October 2001 the first produced CMS Barrel Drift Tube (DT) Muon Chamber was tested at the CERN Gamma Irradiation Facility (GIF) using a muon beam. A Resistive Plate Chamber (RPC) was attached to the top of the DT chamber, and, for the first time, both detectors were operated coupled together. The performance of the DT chamber was studied for several operating conditions, and for gamma rates similar to the ones expected at LHC. In this paper we present the data analysis; the results are considered fully satisfactory.

The drift tube chambers developed for the muon barrel system of the CMS experiment at CERN are large area detectors with 8 measurement points in one direction and 4 in the other; each point has a resolution of about 200 mum. We are using two of such chambers for muon radiography, i.e. the detection and imaging of material with high atomic number Z through the measurement of the multiple scattering of cosmic- ray muons crossing the material itself. The chambers are self- triggered, using the trigger electronics developed for the CMS experiment. Such technique might be applied for example in cargo container inspection searching for high-Z materials. Our apparatus is composed by two chambers with a 7 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> active area. In the gap between the chambers a container and the target material can be placed. Other two drift tube chambers, each with 4 measurement points, interleaved by a thick plane of Fe, give a rough determination of the cosmic muon momentum. We present results on the detection capability and performance of the system.

Two drift tubes (DTs) chambers of the CMS muon barrel system were exposed to a 40 MHz bunched muon beam at the CERN SPS, and for the first time the whole CMS Level-1 DTs-based trigger system chain was tested. Data at different energies and inclination angles of the incident muon beam were collected, as well as data with and without an iron absorber placed between the two chambers, to simulate the electromagnetic shower development in CMS. Special data-taking runs were dedicated to test for the first time the Track Finder system, which reconstructs track trigger candidates by performing a proper matching of the muon segments delivered by the two chambers. The present paper describes the results of these measurements.

Abstract The barrel muon chambers of the CMS detector consist of three sets of four layers of rectangular drift tubes. The performance of several prototypes was measured in a muon beam for various experimental conditions. Special emphasis was given to study performance aspects related to the trigger capability of the chambers.

The drift tubes based CMS barrel muon trigger, which uses self-triggering arrays of drift tubes, is able to perform the identification of the muon parent bunch crossing using a rather sophisticated algorithm. The identification is unique only if the trigger chain is correctly synchronized. Some beam test time was devoted to take data useful to investigate the synchronization of the trigger electronics with the machine clock. Possible alternatives were verified and the dependence on muon track properties was studied.

The barrel region of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider is instrumented with Drift Tube (DT) detectors. This paper describes in full details the calibration of the DT hit reconstruction algorithm. After inter-channel synchronization has been verified through the appropriate hardware procedure, the time pedestals are extracted directly from the distribution of the recorded times. Further corrections for time-of-flight and time of signal propagation are applied as soon as the three-dimensional hit position within the DT chamber is known. The different effects of the time pedestal miscalibration on the two main hit reconstruction algorithms are shown. The drift velocity calibration algorithm is based on the meantimer technique. Different meantimer relations for different track angles and patterns of hit cells are used. This algorithm can also be used to determine the uncertainty on the reconstructed hit position.

The drift chambers in the barrel region of the CMS detector are exposed to magnetic stray fields. To study the performance of the muon reconstruction and the drift time-based muon trigger, prototypes were tested under the expected magnetic field conditions at the H2 test facility at CERN. The results indicate that the overall chamber performance will not be affected. Only the bunch crossing identification capability in the small region near η=1.1, corresponding to the border of the solid angle region covered by the barrel, will be weakened.

Three simplified prototypes of the first-level trigger front-end device for the muon barrel drift chambers of CMS were tested on a chamber prototype. Tests were performed at several incidence angles of a muon beam and with different magnetic field configurations. The recorded drift times were also used to test a full software model reproducing the actual algorithm applied in the final ASIC being produced. The efficiency performance of this software model and of the tested prototype are presented in this paper.

Production of the muon barrel drift chambers called MB3 for the CMS experiment at the LHC has started at Legnaro INFN Labs in 2001. The detectors are fully equipped with the final front-end electronics and high-voltage boards, and test pulse and low-voltage systems. Before being moved to CERN, all chambers are tested and validated. After good noise level and proper high voltage behavior have been ensured, we collect cosmic-ray events triggered by an external scintillator system. We use those data to infer the main parameters of the chambers, namely, detection efficienc y, uniformity in behavior, timing properties (resolution, uniformity, dependence on track angle), and possible shifts of the wires and layers inside the superlayers. The method is particularly efficient in finding pathologies caused by trivial mistakes like, for example, an unconnected electrode, which can be quickly recovered.

Abstract A sample of ASIC prototypes of the first-level trigger front-end device for the muon barrel drift chambers of CMS was tested on a full size chamber prototype. Tests were performed at several incident angles on cosmic rays and at normal incidence using a muon beam. The chamber was irradiated using a 137 C s gamma source to simulate the LHC radiation environment. The performance of the tested prototypes with respect to efficiency, resolution and noise issues is reported.

Abstract The development of the barrel drift chambers for the CMS muon detector at the CERN Large Hadron Collider is supported by a variety of simulation calculations, based on the GARFIELD drift chamber simulation program and the GEANT detector simulation package. This study surveys the results influencing the actual chamber design. The dependence of the drift cell performance on shape and position of the cell electrodes as well as on the mechanical tolerances is shown. The results obtained for space-time relation and spatial resolution are in good agreement to test beam measurements on prototypes.

The CMS muon barrel drift tubes system has been recently fully installed and commissioned in the experiment. The performance and the current status of the detector are briefly presented and discussed.

The latest results of CMS in the area of exotic quarkonium decays will be presented: observation of a peaking structure in $J/\psi\Phi$ mass spectrum in the decay $B^\pm \rightarrow J/\psi \Phi K^\pm$, search for new bottomonium states in $\Upsilon(1\mathrm{S})\pi^+\pi^-$ mass spectrum, measurement of prompt $J/\psi$ pair production.

The phase $\Phi_s$ is the key parameter for the CP-violation of the $B^0_s$-$\bar{B^0_s}$ system. An angular and proper decay time analysis is applied to the $B^0_s \rightarrow J/\psi \Phi$ events. Using a data sample collected by the CMS and ATLAS experiments in LHC Run1, the $B^0_s$ signal candidates are reconstructed and are used to extract the phase $\Phi_s$. We present the latest update on the results in this decay channel.

Measurements of b-hadron and quarkonium production cross sections provide essential information to understand QCD. This talk will show new measurements of double-differential production cross sections vs. transverse momentum pT and rapidity y, at center-of-mass energy √s = 13 TeV, performed by CMS experiment with data collected in 2015. Comparisons with results obtained at √s = 7 TeV will be shown.

There are several motivations to study heavy flavour physics at LHC: advance beauty and charm spectroscopy, test QCD and effective theories, look for indirect evidence or constraints to new physics beyond the standard model, or simply try to have the best as possible description of the environment where direct new physics searches are conducted. In the following most recent results obtained by CMS will be shown. All results are obtained with data collected at a center of mass energy √ s = 7 TeV collected in 2011, with an integrated luminosity L ∼ 5 fb−1, or √s = 8 TeV collected in 2012, with an integrated luminosity L ∼ 20 fb−1. All measurements involve dimuons, most of the times originating from a resonance such as J/ψ or Υ. The presence of two muons in the final state allows maintaining a sustainable trigger rate at the high luminosities provided by LHC; the offline reconstruction of a vertex with the two muon candidates was also common for the involved analyses.

The phase $Φ_s$ is the key parameter for the CP-violation of the $B^0_s$-$\bar{B^0_s}$ system. An angular and proper decay time analysis is applied to the $B^0_s \rightarrow J/ψΦ$ events. Using a data sample collected by the CMS and ATLAS experiments in LHC Run1, the $B^0_s$ signal candidates are reconstructed and are used to extract the phase $Φ_s$. We present the latest update on the results in this decay channel.

Thanks to the excellent tracking and muon identification performance, combined with a flexible trigger system, the CMS experiment at the Large Hadron Collider is conducting a rich and competitive program of measurements in the field of heavy flavor physics. In this talk we review our results on heavy flavour physics, based on a data sample collected by the CMS detector.

The rare decays B s (B 0 ) → µ + µ -are an excellent test of the flavor sector of the Standard Model and provide sensitivity to models with extended Higgs boson sectors.We report on searches for these decays with the CMS experiment using pp collisions at a centre-of-mass energy √ s = 7 TeV collected in 2011.In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions.The resulting upper limits on the branching fractions are B(B 0 s → µ + µ -) < 7.7 × 10 -9 and B(B 0 d → µ + µ -) < 1.8 × 10 -9 at 95% confidence level.

Heavy flavor particles produced in LHC pp collisions at \(\sqrt{s}\) = 7, 8 and 13 TeV constitute an excellent opportunity to test the Standard Model and probe for new physics effects. Recent results by the CMS Collaboration on heavy flavor production and decays are presented.

Measurements of $B^+$ and quarkonium production cross sections provide essential information to understand QCD. This talk will show measurements of double-differential production cross sections vs. transverse momentum $p_T$ and rapidity $y$ at center-of-mass energy of $\sqrt{s}=13$ TeV performed by the CMS experiment. Comparisons with expectations and results obtained at $\sqrt{s}=7$ TeV will be shown.

Measurements of production cross-sections of inclusive $b$-hadrons pairs, bottom mesons and baryons, and quarkonia at LHC will be shown. Recent measurements of branching fractions of bottom baryons, bottom mesons with baryons in the final state, and a new result about a search for intermediate states in meson decay will also be shown.