H. Reithler

We report the observation of five events in which a missing transverse energy larger than 40 GeV is associated with a narrow hadronic jet and of two similar events with a neutral electromagnetic cluster (either one or more closely spaced photons). We cannot find an explanation for such events in terms of backgrounds or within the expectations of the Standard Model.

A sample of 52 Intermediate Vector Boson decays in the (vee) channel is described. They were produced at the CERN SPS Collider for an integrated luminosity of 0.136 pb−1. Both production and decay properties fit well with expectations from the Standard Model of weak interactions. An improved value for the W mass is given and compared with the previously published value for the Z0 mass.

With a segmented total absorption calorimeter of large acceptance, we have measured the total transverse energy spectrum for pp̄ collisions at s12 = 540 GeV up to ΣET= 130 GeV in the pseudo-rapidity range |η|< 1.5. Using two different algorithms, we have looked for localized depositions of transverse energy (jets). For ΣET > 40 GeV, the fraction of events with two jets increases with ΣET; this event structure is dominant for ΣET > 100 GeV. We measure the inclusive jet cross section up to ET(jet) = 60 GeV and the two-jets mass distribution to 120 GeV/c2. The measured cross sections are compatible with the predictions of hard scattering models based on QCD.

We present a detailed study of hadronic jets obtained in a data sample taken in the UA1 detector with a localized transverse energy trigger. We discuss the average shape of jets in terms of energy and charged particle content, and compare this to data generated in Monte Carlo programs. We further extend the previously reported inclusive jet cross section to the region of ET = 100 GeV. A comparison with theoretical models of cross sections for events with more than two jets is also given.

The two-jet cross section measured in the UA1 apparatus at the CERN pp Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x1 and x2. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x2 and x2, as expected in vector gluon theories (QCD). The differential cross section in x1 and x2 is consistent with factorization and provides a measurement of the proton structure function F(x) = G(x) + 49[Q(x) + Q(x)] at values of the four-momentum transfer squared, -t̂ ≈ 2000 GeV2. Over the range x = 0.10−0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (−9.5x).

Track information from the central detector in the UA1 experiment at the CERN proton-antiproton collider (√s = 540 GeV) is used to determine the charged particle multiplicity distribution for the pseudorapidity range ∣η∣ < 1.3. The mean value for this multiplicity per unit of η is 3.9 ± 0.3 for events having at least one track in this range. Data from the central electromagnetic and hadron calorimeters are used to examine the correlation between the transverse energy measured in the collisions and the multiplicity in the central region.

Muon-neutrino and -antineutrino scattering off electrons was detected in a 19-ton Al spark chamber, exposed to the wide-band $\ensuremath{\nu}$ ($\overline{\ensuremath{\nu}}$) beam from the CERN proton synchrotron. The background was determined experimentally. 11 (10) genuine ${\ensuremath{\nu}}_{{\ensuremath{\mu}}^{\ensuremath{-}}}$ (${\overline{\ensuremath{\nu}}}_{{\ensuremath{\mu}}^{\ensuremath{-}}}$) $e$ scattering events were found. The respective cross sections are $(1.1\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}42}({E}_{\ensuremath{\nu}}/\mathrm{GeV})$ ${\mathrm{cm}}^{2}$ and $(2.2\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}42}({E}_{\ensuremath{\nu}}/\mathrm{GeV})$ ${\mathrm{cm}}^{2}$. The analysis excludes a pure $V\ensuremath{-}A$ interaction, and makes a pure $V$ or $A$ theory improbable. The data agree well with the Salam-Weinberg model and ${{sin}^{2}\ensuremath{\theta}}_{\mathrm{W}}=0.35\ifmmode\pm\else\textpm\fi{}0.08$.

Received 21 November 1966DOI:https://doi.org/10.1103/PhysRevLett.18.20©1967 American Physical Society

The angular distribution of isolated π0,s, produced by νμ′s and νμ′s in the Aachen-Padova spark chamber, shows a peak in the forward direction which is not explicable by resonance production. A similar effect is seen in the acoplanarity distribution of the decay photons, which shows an excess of nearly coplanar events. A control sample containing a recoil proton shows no such peaks and is well reproduced by a resonance model. The observed effects are consistent with neutral current (NC) induced coherent single π0 production off the entire Al27 nucleus. The coherent cross sections are σν=(29±10)×10−40 cm2/nucleus and σν=(25±7)×10−40 cm2/nucleus. They determine the isovector axial NC coupling constant ß=0.93±0.12. No η0 mesons were observed, which limits the corresponding isoscalar coupling constant to δ<0.7 (with 90% confidence).

The large area muon detector for the UA1-experiment at the CERN pp-collider consists of simple and robust 4 m × 6 drift chamber modules, which are constructed of extruded aluminium profiles. Electrical field calculations show that a saturated drift velocity can be achieved up to a drift length of 7 cm with only three additional field shaping electrodes and an optimized tube profile. The field calculations as well as results about the spatial resolution of such a drift tube are presented. The coordinate along the wire can be determined from the time difference of the pulses at both ends of the tube.

The high-luminosity LHC (HL-LHC) upgrade is setting now a new challenge for particle detector technologies. The increase in luminosity will produce a particle background in the gas-based muon detectors that is ten times higher than under conditions at the LHC. The detailed knowledge of the detector performance in the presence of such a high background is crucial for an optimized design and efficient operation after the HL-LHC upgrade. A precise understanding of possible aging effects of detector materials and gases is of extreme importance. To cope with these challenging requirements, a new Gamma Irradiation Facility (GIF++) was designed and built at the CERN SPS North Area as successor of the Gamma Irradiation Facility (GIF) during the Long Shutdown 1 (LS1) period. It features an intense source of 662 keV photons with adjustable intensity, to simulate continuous background over large areas, and, combined with a high energy muon beam, to measure detector performance in the presence of the background. The new GIF++ facility has been operational since spring 2015. In addition to describing the facility and its infrastructure, the goal of this work is to provide an extensive characterization of the GIF++ photon field with different configurations of the absorption filters in both the upstream and downstream irradiation areas. Moreover, the measured results are benchmarked with Geant4 simulations to enhance the knowledge of the radiation field. The absorbed dose in air in the facility may reach up to 2.2 Gy/h directly in front of the irradiator. Of special interest is the low-energy photon component that develops due to the multiple scattering of photons within the irradiator and from the concrete walls of the bunker.

Operation of large-area muon detectors at the future Large Hadron Collider (LHC) will be characterized by large sustained hit rates over the whole area, reaching the range of kHzcm−2. We describe a dedicated test zone built at CERN to test the performance and the aging of the muon chambers currently under development. A radioactive source delivers photons causing the sustained rate of random hits, while a narrow beam of high-energy muons is used to directly calibrate the detector performance. A system of remotely controlled lead filters serves to vary the rate of photons over four orders of magnitude, to allow the study of performance as a function of rate.

Inclusive fragmentation of jets into charged particles has been studied in the UA1 experiment at the CERN Super Proton Synchrotron (SPS) pp̄ Collider at s = 540 GeV for jets having a transverse energy above 30 GeV. The observed fragmentation function is very similar to that seen in e+e−jets and is therefore indicative of similar hadronization processes for gluons and quarks. Scaling with the energy of the jet is valid to a good approximation, although slight deviations are suggested by the data. The average transverse momentum with respect to the jet axis for jets with ET > 30 GeV is 600 MeV/c for particles having z > 0.1 and increases slowly with the jet energy.

A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$, recorded with the CMS detector. The coupling strength with respect to the standard model value, $Y_\mathrm{t}$, is determined from kinematic distributions in $\mathrm{t\bar{t}}$ final states containing ee, $μμ$, or e$μ$ pairs. Variations of the Yukawa coupling strength lead to modified distributions for $\mathrm{t\bar{t}}$ production. In particular, the distributions of the mass of the $\mathrm{t\bar{t}}$ system and the rapidity difference of the top quark and antiquark are sensitive to the value of $Y_\mathrm{t}$. The measurement yields a best fit value of $Y_\mathrm{t} =$ 1.16 $^{+0.24}_{-0.35}$, bounding $Y_\mathrm{t}$ $\lt$ 1.54 at a 95% confidence level.

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.

We report on measurements of correlated $$b\bar b$$ production in $$p\bar p$$ collisions at $$\sqrt s = 630GeV$$ , using dimuon data to tag both theb and $$\bar b$$ quarks. Starting from an inclusive dimuon sample we obtain improved cross-sections for single inclusive beauty production and confirm our earlier results on $$B^0 - \bar B^0$$ mixing. From a study of $$b\bar b$$ correlations we derive explicit cross-sections for semi-differential $$b\bar b$$ production. We compare the measured cross-sections and correlations to $$\mathcal{O}\left( {\alpha _s^3 } \right)$$ QCD predictions and find good quantitative agreement. From the measured angular distributions we establish a size-able contribution from higher order QCD processes with a significance of about seven standard deviations. A large nonperturbative contribution to these higher order corrections is excluded.

Muonless single neutral pion production, by muon-neutrinos and antineutrinos, has been observed in a multiplate aluminum spark chamber. In order to test parity conservation the observed production rate by neutrinos has been compared with that by antineutrinos, scaled up with the well-known ratio of νμ to νμ-fluxes. These rates differ by a factor of 2, their difference being 4.3 standard deviations away from zero. This is strong evidence against a parity conserving semileptonic neutral current, e.g. pure vector or axial vector theories.

A search for multifractal structures, in analogy with multifractal theories, is performed on UA1 minimum bias events. A downward concave multifractal spectral function,f(α) (where α is the Lipschitz-Hölder exponent), indicates that there are self-similar cascading processes, governing the evolution from the quark to the hadron level, in the final states of hadronic interactions.f(α) is an accurate measure of the bin to bin fluctuations of any observable. It is shown that the most sensitive comparison between data and the Monte Carlo models, GENCL and PYTHIA 4.8 can be made usingf(α). It is found that these models do not fully reproduce the behaviour of the data.

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 recent advent of functional magnetic resonance imaging (fMRI) as a readily accessible neuroimaging method has led to exciting new insights into the functioning of the human motor system. However, technical complications related to the fMRI scanner environment often limit the ability to measure the desired behavioral data reflecting the subjects’ movements. In order to perform kinematic registrations of predefined complex two-dimensional movement patterns while scanning, a new MR-compatible setup has been developed. The method presented here allows the recording of detailed pen tracing data during concurrent functional image acquisition. Essentially, temporally high resolved resistance measurements are used to keep track of the covered distance across time, as applied here to the tracing of various mazes. In this way, the current setup adds the close monitoring of continuous tracing movements to the spectrum of behavioral data which can be successfully obtained in an fMRI setting.

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$γγ$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvertζ_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvertζ_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.

Single recoil protons have been detected in a multiplate Al spark chamber exposed to the 2-GeV wide-band neutrino beam from the CERN proton synchrotron. Neutron-induced protons were suppressed by suitable geometrical and kinematical cuts. After correction for remaining neutron background (110\ifmmode\pm\else\textpm\fi{}15 events) and single-pion contribution (45\ifmmode\pm\else\textpm\fi{}6 events), the final sample contains 62\ifmmode\pm\else\textpm\fi{}19 genuine neutrino-induced single protons. This yields an effective ratio of neutral-current (NC) to charged-current (CC) events of ${R}_{N}=(15\ifmmode\pm\else\textpm\fi{}5)%$, in the range $0.2&lt;\ensuremath{-}{q}^{2}&lt;1.0$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. This number is due to a mixture of elastic neutrino scatterings off protons and neutrons. From the probability ${f}_{\mathrm{np}}$ for a recoil neutron to give an accepted proton, one derives a model-independent combination of the NC/CC ratios ${R}_{p}+{f}_{\mathrm{np}}{R}_{n}$, with ${f}_{\mathrm{np}}=0.31\ifmmode\pm\else\textpm\fi{}0.04$. This favors axial-vector-isovector-dominant NC coupling constants and is consistent with the Weinberg-Salam model with ${{sin}^{2}\ensuremath{\theta}}_{W}={0.29}_{\ensuremath{-}0.11}^{+0.21}$. In terms of this model, this corresponds to ${R}_{p}=(10\ifmmode\pm\else\textpm\fi{}3)%$ and ${R}_{n}=({15}_{\ensuremath{-}5}^{+3})%$.

The UA1 Collaboration has recently improved its measurement of the beauty production cross-section by including explicit measurements of bb correlations. Using these data we have determined the strong coupling constant αs. The comparison of the measured cross-section for 2-body final states with O(αs3) QCD predictions yields a measurement of αs(20 GeV) = 0.145−0.010 exp −0.016 th+0.012 +0.013, corresponding to αs(Mz) = 0.113−0.006 exp −0.009 th+0.007 +0.008. This is the first theoretically well-defined measurement of αs from a purely hadronic production process. Evaluating αs from cross-sections at different Q2-values we find that the running of αs is needed for internal consistency of the UA1 data.

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 Die Streuung von Myon‐Neutrinos an Elektronen ist ein sensitiver Test der neuen Eichtheorien. Die Messung der Myon‐Neutrino und Antineutrino‐Streuraten an Elektronen ermöglicht es, die Fülle der Modellvarianten einzuschränken.

The total punchthrough probability of showers produced by negatively charged pions of momenta 30, 40, 50, 75, 100, 200 and 300 GeV/c, has been measured in the RD5 experiment at CERN using a toroidal spectrometer. The range of the measurement extends to 5.3 m of equivalent iron. Our results have been obtained by two different analysis methods and are compared with the resutls of a previous experiment.

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. The return yoke consists of five dodecagonal three-layered barrel wheels and four end-cap disks at each end comprised of steel blocks up to 620 mm thick, which serve as the absorber plates of the muon detection system. Accurate characterization of the magnetic field everywhere in the CMS detector is required. To measure the field in and around the steel a system of 22 flux-loops and 82 3-D Hall probe B-sensors is installed on the return yoke blocks. Fast discharges of the solenoid (190 s time-constant) made during the CMS magnet surface commissioning test at the solenoid central fields of 2.64, 3.16, 3.69 and 4.01 T were used to induce voltages in the flux-loops. The voltages are measured on-line and integrated off-line to obtain the magnetic flux in the steel yoke close to the muon chambers at full excitations of the solenoid. The Hall probe B-sensors installed on the steel-air interfaces give supplementary information on the components of magnetic field and permit to estimate the remanent field in steel to be added to the magnetic flux density obtained by the voltages integration. A TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. The results of the measurements and calculations are presented, compared and discussed.

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 experiments at the planned 14 TeV proton-proton collider LHC will need a good identification and measurement of muons with energies of up to about 800 GeV. The production of electromagnetic secondaries by muons of energy from 10 to 300 GeV has been measured at the RD5 experiment at CERN using various detector types proposed for LHC experiments. It is demonstrated that the detectors can recognize the presence of individual hits from em secondaries, and that the muon measurement would be seriously compromised if these hits are not suppressed.

The ratio of the structure function ${F}_{2}^{A}(x)$ of a nucleus $A$ to that of deuterium ${F}_{2}^{\mathrm{D}}(x)$ is computed for $A=\mathrm{F}\mathrm{e},\mathrm{ }\mathrm{Al}, ^{12}\mathrm{C}, \mathrm{and} ^{4}\mathrm{He}$. The difference between scattering off free and bound nucleons is explained by a fraction $g$ of the valence quarks of nuclear matter moving effectively in bags of doubled size (e.g., $\ensuremath{\alpha}$'s). The difference between European Muon Collaboration and SLAC data is attributed to the different effective quark mass, which is close to zero at $\ensuremath{-}{q}^{2}=100$ Ge${\mathrm{V}}^{2}$, but 140\ifmmode\pm\else\textpm\fi{}25 MeV, at $〈\ensuremath{-}{q}^{2}〉=3$ Ge${\mathrm{V}}^{2}$. A cluster probability of $g=15%(10%)$ fits the Fe (Al) data quite well.

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.

Magnet Cycles and Stability Periods of the CMS Experiment are studied with the Alignment Link System data recorded along the 2008–2013 years of operation. The motions of the mechanical structures due to the magnetic field forces are studied and the mechanical stability of the detector during the physics data taking periods is verified.

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.

The $A$ dependence of the nuclear effect, as recently measured by Arnold et al., has been calculated from the probability of forming $&gt;3q$ clusters, by use of the space-time wave function of valence quarks, and the assumption that nuclei are in hexagonal or cubic dense packing. A fair fit to the $x$ distributions of $\frac{{\ensuremath{\sigma}}_{A}}{{\ensuremath{\sigma}}_{\mathrm{D}}}$ is obtained, if we apply the valence quarks' average Fermi momentum and mass from our previous determinations.

A study of the time required for the CMS detector to reach structural equilibrium once the magnetic field is ramped to its operational value of 3.8 T is presented. In addition, the results from a stability monitoring at 3.8 T over an eight-month period are given.

A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016-2018, corresponding to an integrated luminosity of 117 fb$^{-1}$. The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H $\to$ SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10-100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass ($\approx$15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions $\mathcal{B}$(H $\to$ SS) $\lt$ 20% for proper decay lengths of 10-50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.

A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13\TeV is presented. The transverse momenta of jets within $\lvert\eta\rvert \lt$ 4.7 reach down to 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background.

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 drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. A dedicated Velocity Drift Chamber (VDC) with 1-L volume has been built at the III. Phys. Institute A, RWTH Aachen, in order to monitor the drift velocity of all CMS barrel muon Drift Tube chambers. A system of six VDCs was installed at CMS and has been running since January 2011. We present the VDC monitoring system, its principle of operation, and measurements performed.

The central feature of the CMS Link alignment system is a network of Amorphous Silicon Position Detectors distributed throughout the muon spectrometer that are connected by multiple laser lines. The data collected during the years from 2008 to 2015 is presented confirming an outstanding performance of the photo sensors during more than seven years of operation. Details of the photo sensor readout of the laser signals are presented. The mechanical motions of the CMS detector are monitored using these photosensors and good agreement with distance sensors is obtained.

We present a concept of a muon detector well suited for an experiment at the LHC. The muon traverses four chambers, each consisting of ten layers of drift tubes which measure the track segments in two projections, and of two layers of a resistive plate chamber (RPC) which provide locally the time of arrival of the particle. For the muon momentum determination, each track segment is measured with an accuracy of 0.1 mm. First laboratory measurements with a small prototype have been performed.

Abstract Die Entdeckung schwacher neutraler Ströme vor zehn Jahren war eine glanzvolle Bestätigung der elektroschwachen Theorie. Die Vereinheitlichung der Kopplungskonstanten und die direkte Beobachtung des Quants der schwachen Kraft blieben aber ungeprüft. Dieser Nachweis ist in diesem Jahr zwei Experimentalphysiker‐Gruppen am Proton‐Antiproton‐Speicherring des CERN gelungen.

We present results on an intensive study of a muon detector prototype designed for an experiment at the LHC. The chamber has eight layers of drift tubes measuring one projection of a muon track, and was tested with cosmic and beam muons and in a magnetic field. Single hit detection efficiencies of 99.9% for all gas mixtures and single hit resolutions of 190 μm for the preferred gas mixture of Ar/CO2 80% / 20% were achieved. In a magnetic field of 3 T the single hit resolution with this gas mixture decreased by 10%.

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

An aluminium spark chamber of 19 tons fiducial weight was exposed to the CERN neutrino beam. Possible cases of (ν̄)μ e scattering were selected by requiring an isolated shower at an angle < 5° to the indirection with an energy between 0.2 and 2 GeV, and satisfying the kinematics of elastic neutrino scattering off electron. In 508 (607) k-pictures of ν (ν̄)-film there were 25 (19) of such candidates found. Background gammas come mainly from neutral current induced π 0 production; less important is inverse β-decay. The background was determined experimentally in three consistent ways. After background substraction, a signal of 13.2 ± 5.3 ν μe- events and 16.1 ± 4.5 ν̄μe- events was left. After normalization for the fluxes used, the comparison of those rates diverges by 3 standard deviations from the V-A prediction. The total cross sections turn out to be 2.4 ±1.2 for ν μe- and 5.4 ±1.7 for ν̄μe-, in units of 10-42·Eν cm2. They are in rather good agreement with the Salam-Weinberg theory.

The momentum and angular distributions of punchthrough muons have been measured after a 10 λ calorimeter using an iron toroid magnet with 1.5 T as spectrometer. The calorimeter was inside a variable magnetic field of 0 to 3 T. The incident momentum of the π− beam ranged from 20 to 300 GeV/c. Measurements were also done at some beam momenta for π+, K+ and p. The results are compared with Monte Carlo predictions. A parameterization for the momentum spectrum of punchthrough muons was derived from the data.

This document presents an overview of the induced photocurrents in the Amorphous Silicon Position Detectors used in the network of diode lasers and photo sensors of the CMS Link alignment system recorded during its eleven years of operation. After a description of the sensors characteristics, the layout of the sensors network is discussed. The sensors are distributed throughout the muon spectrometer and connected by laser lines. The data used correspond to readout information obtained during some of the physics runs from 2008 to 2018.

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapidity-dependent difference ($\Delta v_2$) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, $v_2$) between $\mathrm{D}^0$ ($\mathrm{\bar{u}c}$) and $\overline{\mathrm{D}}^0$ ($\mathrm{u\bar{c}}$) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of $\Delta v_2$. The rapidity-averaged value is found to be $\langle\Delta v_2 \rangle =$ 0.001 $\pm$ 0.001 (stat) $\pm$ 0.003 (syst) in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the $\mathrm{D}^0$ and $\overline{\mathrm{D}}^0$ mesons $v_2$ and triangular flow coefficient ($v_3$) as functions of rapidity, transverse momentum ($p_\mathrm{T}$), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt $\mathrm{D}^0$ meson $v_2$ values is observed, while the $v_3$ is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry.