P. Schleper

We present an analysis of the neutrino event sample recorded in the Fréjus experiment. This sample which corresponds to the 1.56 kt yr final sensitivity of the experiment is compared to the predictions of a Monte Carlo neutrino simulation program. It is based on a recent calculation of the atmospheric neutrino flux at the Fréjus latitude which takes into account muon polarization effects. The comparison is performed on the distributions of the visible energy, the zenith angle and the neutrino flavor. Good agreement is obtained between the data and the simulation within statistics.

We present results on calibration runs performed with pions at the CERN SPS for different modules of the H 1 liquid argon calorimeter which consists of an electromagnetic section with lead absorbers and a hadronic section with steel absorbers. The data cover an energy range from 3.7 to 205 GeV. Detailed comparisons of the data and simulation with GHEISHA 8 in the framework of GEANT 3.14 are presented. The measured pion induced shower profiles are well described by the simulation. The total signal of pions on an energy scale determined from electron measurements is reproduced to better than 3% in various module configurations. After application of weighting functions, determined from Monte Carlo data and needed to achieve compensation, the reconstructed measured energies agree with simulation to about 3%. The energies of hadronic showers are reconstructed with a resolution of about 50%√E ⨸ 2%. This result is achieved by inclusion of signals from an iron streamer tube tail catcher behind the liquid argon stacks.

Results on J/ψ production in ep interactions in the H1 experiment at HERA are presented. The J/ψ mesons are produced by almost real photons (Q2 ≈ 0) and detected via their leptonic decays. The data have been taken in 1994 and correspond to an integrated luminosity of 2.7 pb−1. The γp cross section for elastic J/ψ production is observed to increase strongly with the center of mass energy. The cross section for diffractive J/ψ production with proton dissociation is found to be of similar magnitude as the elastic cross section. Distributions of transverse momentum and decay angle are studied and found to be in accord with a diffractive production mechanism. For inelastic J/ψ production the total γp cross section, the distribution of transverse momenta, and the elasticity of the J/ψ are compared to NLO QCD calculations in a colour singlet model and agreement is found. Diffractive ψ′ production has been observed and a first estimate of the ratio to J/ψ production in the HERA energy regime is given.

The present study is based on a sample of 407 775 single muons and 12 559 muon bundles with zenith angles smaller than 60°, observed in the 12.3m×6m×6m Fréjus proton-decay detector, at a depth of 4850 hg/cm2. The variation of the vertical muon intensity with depth is given. Using a maximum-likelihood method, the muon lateral distribution of underground bundles is investigated as a function of muon multiplicity and zenith angle. The same method yields the true multiplicity distribution at the site depth, corrected for all detection effects.Received 5 May 1989DOI:https://doi.org/10.1103/PhysRevD.40.2163©1989 American Physical Society

The characteristics, trigger and monitoring systems, data acquisition as well as the performance of the Fréjus nucleon decay detector are presented.

The fully contained events recorded in the Fréjus detector are used to search for (B-L)-violating nucleon decay and di-nucleon decay processes. No signal is found for a sensitivity of 2.0 kiloton year. The lower limits on the partial lifetime for the various nucleon decay modes range from 5.4×1030 yr for p→μ−π+K+ to 1.0×1032 yr for pn→e+n. We also quote limits on neutron and di-neutron decay into three and two neutrinos respectively.

From the analysis of the fully contained events recorded in the underground Fréjus detector, a lower limit of 1.2×108s at 90% CL is derived for the free neutron-antineutron oscillation time.

Muons and multimuons detected in the Fréjus underground nucleon decay detector between February 1984 and January 1986 have been analyzed. No excess events are observed in the direction of Cygnus X-3, which yields a 90% confidence level upper flux limit of 0.8 × 10−12 cm−2 s−1, for an average rock overburden of 5000 hg cm−2 corresponding to energies ⪆ 3 TeV. Using the 4.79 h periodicity of Cygnus X-3, no signal is found in any phase interval.

At the CMS experiment, a growing reliance on the fast Monte Carlo application (FastSim) will accompany the high luminosity and detector granularity expected in Phase 2. The FastSim chain is roughly 10 times faster than the application based on the Geant4 detector simulation and full reconstruction referred to as FullSim. However, this advantage comes at the price of decreased accuracy in some of the final analysis observables. In this contribution, a machine learning-based technique to refine those observables is presented. We employ a regression neural network trained with a sophisticated combination of multiple loss functions to provide post-hoc corrections to samples produced by the FastSim chain. The results show considerably improved agreement with the FullSim output and an improvement in correlations among output observables and external parameters. This technique is a promising replacement for existing correction factors, providing higher accuracy and thus contributing to the wider usage of FastSim.

With the Fréjus 900 ton calorimeter (550 ton fiducial), a search for nucleon decay events into anti-neutrino plus meson has been performed. No signal is found for a sensitivity of 1.3 kiloton × year. Lower lifetime limits for various decay modes range from 0.9 to 2.9 1031 years (at 90% C.L.).

The positions of the silicon modules of the CMS tracker will be known to O(100 μm) from survey measurements, mounting precision and the hardware alignment system. However, in order to fully exploit the capabilities of the tracker, these positions need to be known to a precision of a few μm. Only a track-based alignment procedure can reach this required precision. Such an alignment procedure is a major challenge given that about 50000 geometry constants need to be measured. Making use of the novel χ2 minimization program Millepede II an alignment strategy has been developed in which all detector components are aligned simultaneously and all correlations between their position parameters taken into account. Different simulated data, such as Z0 decays and muons originated in air showers were used for the study. Additionally information about the mechanical structure of the tracker, and initial position uncertainties have been used as input for the alignment procedure. A proof of concept of this alignment strategy is demonstrated using simulated data.

Lower limits on the nucleon lifetime in channels containing at least one positron or muon are given. The analysis is based on 4 years of data taking with the Fréjus detector. Various approaches to determine the background from atmospheric neutrinos are discussed and two different nuclear models are used in event simulations. The limits obtained range from 1031 years forp→e + K *0 to 1.5·1032 years forp→e + K *0 to 1.5·1032 years forp→µ + γ.

The positions of the silicon modules of the CMS tracker will be known to 0(100 μm) from survey measurements, mounting precision and the hardware alignment system. However, in order to fully exploit the capabilities of the tracker, these positions need to be known to a precision of a few μm. Only a track-based alignment procedure can reach this required precision. Such an alignment procedure is a major challenge given that about 50.000 geometry constants need to be measured. Making use of the novel χ2 minimization program Millepede II an alignment strategy has been developed in which all detector components are aligned simultaneously and all correlations between their position parameters taken into account. Tracks from different sources such as Z0 decays and cosmic ray muons, plus information about the mechanical structure of the tracker, and initial position uncertainties have been used as input for the alignment procedure. A proof of concept of this alignment strategy is demonstrated using simulated data.

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is $99.95\pm0.05\,\%$, while the intrinsic spatial resolutions are $4.80\pm0.25\,\mu \mathrm{m}$ and $7.99\pm0.21\,\mu \mathrm{m}$ along the $100\,\mu \mathrm{m}$ and $150\,\mu \mathrm{m}$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.

The Alignment of the CMS tracker will require to determine about 10 5 alignment parameters. The MILLEPEDE program, a linear least-squares algorithm, is a promising c andidate for this task, having been used successfully for alignment in several experiments. However, due to the inversion of a large matrix of linear equations, MILLEPEDE in its original form was limited to problems with about 10 4 parameters. A new version of the program, MILLEPEDE II, provides an iterative method to determine the solution of the matrix, which should work for systems with 10 5 parameters, if the matrix is sparse. This method is tested within the CMS object oriented reconstruction framework (ORCA). Its precision and CPU needs are studied and compared to the inversion method, using alignment scenarios of the CMS tracker with currently up to 12000 parameters.

An efficient administration of computing centres requires sophisticated tools for the monitoring of the local computing infrastructure. The enormous flood of information from different monitoring sources retards the identification of problems and complicates the local administration unnecessarily. The meta-monitoring system "HappyFace" offers elegant mechanisms to collect, process and evaluate all relevant information and to condense it into a simple rating visualisation, reflecting the current status of a computing centre. In this paper, we give an overview of the HappyFace architecture and selected modules.

At the CMS experiment, a growing reliance on the fast Monte Carlo application (FastSim) will accompany the high luminosity and detector granularity expected in Phase 2. The FastSim chain is roughly 10 times faster than the application based on the GEANT4 detector simulation and full reconstruction referred to as FullSim. However, this advantage comes at the price of decreased accuracy in some of the final analysis observables. In this contribution, a machine learning-based technique to refine those observables is presented. We employ a regression neural network trained with a sophisticated combination of multiple loss functions to provide post-hoc corrections to samples produced by the FastSim chain. The results show considerably improved agreement with the FullSim output and an improvement in correlations among output observables and external parameters. This technique is a promising replacement for existing correction factors, providing higher accuracy and thus contributing to the wider usage of FastSim.

Novel techniques are indispensable to process the flood of data from the new generation of radio telescopes. In particular, the classification of astronomical sources in images is challenging. Morphological classification of radio galaxies could be automated with deep learning models that require large sets of labelled training data. Here, we demonstrate the use of generative models, specifically Wasserstein GANs (wGAN), to generate artificial data for different classes of radio galaxies. Subsequently, we augment the training data with images from our wGAN. We find that a simple fully-connected neural network for classification can be improved significantly by including generated images into the training set.

We present an experimental estimate of the background due to atmospheric neutrino interactions in the Fréjus underground nucleon decay experiment. The data of a CERN neutrino experiment of the Aachen-Padova collaboration are re-analyzed for this purpose. The large statistics available, some 60 kt yr of equivalent sensitivity, allows for a detailed topological study of most nucleon decay channels with a charged lepton.

Abstract As a result of the high luminosity phase of the SLHC, for CMS a tracking system with very high granularity is mandatory and the sensors will have to withstand an extreme radiation environment of up to 10 16  part/ 2 . On this basis, a new geometry with silicon short strip sensors (strixels) is proposed. To understand their performances, test geometries are developed whose parameters can be verified and optimized using simulation of semiconductor structures. We have used the TCAD-ISE (SYNOPSYS package) software in order to simulate the main electrical parameters of different strip geometries, for p-in-n-type wafers.

While the tracking detectors of the ATLAS and CMS experiments have shown excellent performance in Run 1 of LHC data taking, and are expected to continue to do so during LHC operation at design luminosity, both experiments will have to exchange their tracking systems when the LHC is upgraded to the high-luminosity LHC (HL-LHC) around the year 2024. The new tracking systems need to operate in an environment in which both the hit densities and the radiation damage will be about an order of magnitude higher than today. In addition, the new trackers need to contribute to the first level trigger in order to maintain a high data-taking efficiency for the interesting processes. Novel detector technologies have to be developed to meet these very challenging goals. The German groups active in the upgrades of the ATLAS and CMS tracking systems have formed a collaborative "Project on Enabling Technologies for Silicon Microstrip Tracking Detectors at the HL-LHC" (PETTL), which was supported by the Helmholtz Alliance "Physics at the Terascale" during the years 2013 and 2014. The aim of the project was to share experience and to work together on key areas of mutual interest during the R&D phase of these upgrades. The project concentrated on five areas, namely exchange of experience, radiation hardness of silicon sensors, low mass system design, automated precision assembly procedures, and irradiations. This report summarizes the main achievements.

Recent developments in soft hadronic interactions are reviewed. Emphasis it put on measurements of the proton structure at low x, photon structure, diffraction and exclusive processes such as vector-meson production and their interpretation in approaches to QCD dynamics like BFKL or CCFM.

In these simulation studies an energy weighting method is applied to the signals of the CMS hadronic calorimeter readout with a longitudinal segmentation for a possible future upgrade. Tabulated weighting factors are used to compensate for the different response of hadronic and electromagnetic energy depositions of simulated pion showers in the hadronic calorimeter. The weighting improves the relative energy resolution: $$ (\sigma _E /E)^2 = \left[ {((92.2 \pm 0.6)\% /\sqrt E )^2 + ((6.5 \pm 0.1)\% )^2 } \right] $$ (before weighting), $$ (\sigma _{E,weight} /E)^2 = \left[ {((85.4 \pm 0.5)\% /\sqrt E )^2 + ((4.4 \pm 0.1)\% )^2 } \right] $$ (after weighting), where E in the square root has units of GeV.

In this thesis, pairs of top quarks produced in proton-proton collisions at a center-of-mass energy of 7 TeV and decaying in the muon+jets channel tt → (bμν)(bqq′) are analyzed using data that were recorded by the CMS detector in the year 2010 and correspond to an integrated luminosity of 35.9 pb−1. A sample of 78 events is selected by requiring exactly one isolated muon and at least four jets, two of them being identified as jets from the decay of b quarks. Given these selection criteria, the expected fraction of tt events is 94%. The trijet mass, M3, and the dijet mass, M2, are reconstructed, taking into account the b-tagging information. M3 and M2 are estimators of the masses of hadronically decaying top quarks and the corresponding W bosons, respectively. Templates for M2 and for the event-wise mass difference ∆M32 = M3 − M2 are parametrized as linear functions of the top quark mass, mt, and the jet energy scale (JES). Based on the precise knowledge of the W boson mass, M2 provides a strong handle on the energy scale of jets from light quarks. The reconstructed M2 and ∆M32 in data are compared to the template functions from simulation in a combined likelihood fit. The overall JES in the selected sample is found to be 1.048 ± 0.040 (stat) ±0.015 (syst) relative to the simulated JES and the measured mt is 167.8 ± 7.1 (stat+JES) ±3.1 (syst) GeV. This is one of the first measurements of mt at the Large Hadron Collider. Furthermore, the JES measurement is an important input for the commissioning of the CMS experiment for the upcoming measurements with more data in the near future. Kurzfassung In der vorliegenden Arbeit werden Ereignisse mit Top-Quark-Paaren analysiert, die in ProtonProton-Kollisionen bei einer Schwerpunktsenergie von 7 TeV erzeugt wurden und im Myon+JetsKanal tt → (bμν)(bqq′) zerfallen. Der verwendete Datensatz wurde im Jahr 2010 vom CMSDetektor aufgezeichnet und entspricht einer integrierten Luminositat von 35.9 pb−1. Insgesamt 78 Ereignisse werden selektiert, die ein isoliertes hoch-energetisches Myon sowie mindestens vier Jets aufweisen, wobei verlangt wird, dass zwei der Jets dem Zerfall eines b-Quarks zugewiesen werden konnen. Der erwartete Anteil von tt-Ereignissen nach diesen Selektionskriterien ist 94%. Dreijetund Zweijet-Massen, M3 bzw. M2, werden unter Berucksichtigung der Zuordnung von Jets zu b-Quarks rekonstruiert. M3 und M2 dienen als Schatzer fur die Massen von hadronisch zerfallenden Top-Quarks bzw. der zugehorigen W-Bosonen. Zusatzlich wird die Massendifferenz ∆M32 = M3−M2 in jedem Ereignis als Observable verwendet. Die Formen der erwarteten Verteilungen von M2 und ∆M32 werden als lineare Funktionen der Top-Quark-Masse, mt, sowie der Jetenergieskala (JES) parametrisiert. Dank der prazisen Kenntnis der Masse des W-Boson erlaubt die M2-Verteilung eine Messung der Energieskala von Jets leichter Quarks. Die in den Daten gefundenen Werte von M2 und ∆M32 werden mit den erwarteten Verteilungen verglichen. Eine gemeinsame Maximum-Likelihood-Messung ergibt eine mittlere JES von 1.048±0.040 (stat) ±0.015 (syst) relativ zu der simulierten JES fur die gewahlten Ereignisse sowie mt = 167.8 ± 7.1 (stat+JES) ±3.1 (syst) GeV. Dies ist eine der ersten Messungen von mt am Large Hadron Collider. Daruber hinaus ist das Ergebnis der JES-Messung eine wichtige Information fur die Vorbereitung des CMS-Experiments auf die kommenden Messungen mit mehr Daten in der nachsten Zeit.

In case of the discovery of supersymmetry at the LHC, the goal will be to identify the underlying theory, its fundamental parameters, and the masses of SUSY particles. We followed here the approach to reconstruct the decay chains in SUSY events under the assumption of common intermediate masses. These masses cannot be extracted from each event because of the unmeasured LSP momenta in case of R-parity conservation. But an ensemble of events can be over-constrained, if the decay chains are long enough, such that enough mass constraints are available. Here, we present a new method combining a) a SUSY mass scan, b) a kinematic fitting based on a genetic algorithm for decay chain reconstruction, and c) the usage of angular decay information to suppress the background from other SUSY processes. Taking into account the full combinatorial background and experimental resolutions in the most difficult case of the fully hadronic decay mode, we demonstrate, within one SUSY scenario, that this method can be used to derive a probability map of the SUSY parameter space.

Machine learning techniques that perform morphological classification of astronomical sources often suffer from a scarcity of labelled training data. Here, we focus on the case of supervised deep learning models for the morphological classification of radio galaxies, which is particularly topical for the forthcoming large radio surveys. We demonstrate the use of generative models, specifically Wasserstein GANs (wGANs), to generate data for different classes of radio galaxies. Further, we study the impact of augmenting the training data with images from our wGAN on three different classification architectures. We find that this technique makes it possible to improve models for the morphological classification of radio galaxies. A simple Fully Connected Neural Network (FCN) benefits most from including generated images into the training set, with a considerable improvement of its classification accuracy. In addition, we find it is more difficult to improve complex classifiers. The classification performance of a Convolutional Neural Network (CNN) can be improved slightly. However, this is not the case for a Vision Transformer (ViT).

Searches for physics beyond the Standard Model are reported from electron-proton collisions at a center of mass energy of 318 GeV. Results on a completely model independent search for deviations from Standard Model predictions at large transverse momenta are reported as well as generic searches for contact interactions, leptoquarks and excited fermions from the H1 and ZEUS experiments.

The CMS experiment at the Large Hadron Collider at CERN is in the last phase of its construction. The harsh radiation environment at LHC will put strong demands in radiation hardness to the innermost parts of the detector. To assess the performance of irradiated silicon microstrip detector modules, a testbeam was conducted at the Testbeam 22 facility of the DESY research center. The primary objective was the signal-to-noise measurement of fully irradiated CMS Tracker modules to ensure their functionality up to 10 years of LHC operation. The paper briefly summarises the basic setup at the facility and the hardware and software used to collect and analyse the data. Some interesting subsidiary results are shown, which confirm the expected behaviour of the detector with respect to the signal-to-noise performance over the active detector area and for different electron energies. The main focus of the paper are the results of the signal-to-noise over reverse bias voltage measurements for CMS Tracker Modules which were exposed to different radiation doses.

The electron-proton collider HERA is a unique tool for the discovery of particles and interactions beyond the Standard Model. Results from the two experiments, H1 and ZEUS, are reported which have been obtained from data collected within the first two years of operation. Excited electrons, neutrinos and quarks, leptoquarks, leptogluons, squarks in a class of supersymmetric models, and also the search for contact interactions are covered.