R. Wolf

A search has been made with the upgraded UA2 experiment at the CERN pp Collider at s=630 GeV for multi-jet events with large transverse momentum imbalance in a data sample corresponding to an integrated luminosity of 7.4 pb−1. Under the assumption that the photino is the lightest stable supersymmetric (SUSY) particle, the data have been used to deduce lower limits in a minimal SUSY model for the squark (mq) and the gluino (mg) masses. The 90% CL bounds are mg> 74 GeV independent of mg, mg> 79 GeV independent of mg, and and m> 106 GeV for mq=mq=m.

The UA2 experiment has collected large samples of W and Z events during recent runs at the CERN pp Collider at s = 630 GeV. These samples have been used to perform precise measurements of the masses of the W and Z bosons. After a careful analysis of systematic errors, an improved result is obtained for the mass ratio mwmz. This provides a new value for the weak mixing parameter sin2θw. Furthermore, it can be combined with recent measurements of the Z mass from e+e− colliders to give an absolute measurement of the W mass, leading to the result mw=80.49±0.43 (stat) ± 0.24 (syst) GeV.

Cross-sections for diffractive particle production and pseudorapidity distributions of the decay products of diffractive states are presented. The data were obtained with the UA 5 streamer chamber detector at the CERNpp Collider operated in a new pulsed mode yieldingpp interactions at c.m. energies of 900 and 200 GeV. Data recorded with a special trigger designed to select a sample of events enriched in single-diffractive interactions clearly favour ap t -limited fragmentation of diffractive states. The cross-section for single-diffractive particle production ϊ was found to be 7.8±0.5±1.1 mb at 900 GeV and 4.8±0.5±0.8 mb at 200 GeV (first error statistical, second systematic). From the pseudorapidity distribution of diffractive states we deduce the average number of charged particles to be 6.5±1.0 at 900 GeV and 4.1±1.1 at 200 GeV. Furthermore we report on our estimates for the cross-section of double-diffractive particle production at both Collider energies.

The lead-liquid argon sampling calorimeter of the SLD detector is one of the largest detectors employing cryogenic liquids now in operation. This paper details the design and performance considerations, the mechanical and cryogenic systems, the absorber design and tower segmentation, the data acquisition electronics, and the control systems of the detector. The initial operational performance of the device is discussed. Detailed resolution studies will be presented in a later paper.

Abstract Applications of neural networks to data analyses in natural sciences are complicated by the fact that many inputs are subject to systematic uncertainties. To control the dependence of the neural network function to variations of the input space within these systematic uncertainties, several methods have been proposed. In this work, we propose a new approach of training the neural network by introducing penalties on the variation of the neural network output directly in the loss function. This is achieved at the cost of only a small number of additional hyperparameters. It can also be pursued by treating all systematic variations in the form of statistical weights. The proposed method is demonstrated with a simple example, based on pseudo-experiments, and by a more complex example from high-energy particle physics.

Data analysis in science, e.g., high-energy particle physics, is often subject to an intractable likelihood if the observables and observations span a high-dimensional input space. Typically the problem is solved by reducing the dimensionality using feature engineering and histograms, whereby the latter technique allows to build the likelihood using Poisson statistics. However, in the presence of systematic uncertainties represented by nuisance parameters in the likelihood, the optimal dimensionality reduction with a minimal loss of information about the parameters of interest is not known. This work presents a novel strategy to construct the dimensionality reduction with neural networks for feature engineering and a differential formulation of histograms so that the full workflow can be optimized with the result of the statistical inference, e.g., the variance of a parameter of interest, as objective. We discuss how this approach results in an estimate of the parameters of interest that is close to optimal and the applicability of the technique is demonstrated with a simple example based on pseudo-experiments and a more complex example from high-energy particle physics.

In high-energy particle collisions, the primary collision products usually decay further resulting in tree-like, hierarchical structures with a priori unknown multiplicity. At the stable-particle level all decay products of a collision form permutation invariant sets of final state objects. The analogy to mathematical graphs gives rise to the idea that graph neural networks (GNNs), which naturally resemble these properties, should be best-suited to address many tasks related to high-energy particle physics. In this paper we describe a benchmark test of a typical GNN against neural networks of the well-established deep fully-connected feed-forward architecture. We aim at performing this comparison maximally unbiased in terms of nodes, hidden layers, or trainable parameters of the neural networks under study. As physics case we use the classification of the final state X produced in association with top quark-antiquark pairs in proton-proton collisions at the Large Hadron Collider at CERN, where X stands for a bottom quark-antiquark pair produced either non-resonantly or through the decay of an intermediately produced Z or Higgs boson.

The upgraded UA 2 detector has collected data corresponding to a total integrated luminosity of 7.5 pb−1 from $$\bar pp$$ collisions at a centre of mass energy of 630 GeV during 1988 and 1989. A search has been performed for the production and decay of the top quark (t) or a member of a hypothetical fourth family (b′). No evidence has been found for such processes. Using the expected rates for production and decay branching ratios from the Standard Model, this implies that the top quark mass is greater than 69(71) GeV/c2, and that theb′ mass is greater than 54(57) GeV/c2, at 95(90)% confidence.

The relation between the input and output spaces of neural networks (NNs) is investigated to identify those characteristics of the input space that have a large influence on the output for a given task. For this purpose, the NN function is decomposed into a Taylor expansion in each element of the input space. The Taylor coefficients contain information about the sensitivity of the NN response to the inputs. A metric is introduced that allows for the identification of the characteristics that mostly determine the performance of the NN in solving a given task. Finally, the capability of this metric to analyze the performance of the NN is evaluated based on a task common to data analyses in high-energy particle physics experiments.

Analyzing physics data at LHC experiments is a complicated task involving multiple steps, sharing of expertise, cross checks and comparing different analyses. To maximize physics productivity, the CMS experiment at LHC has developed a collection of analysis tools called the PAT (Physics Analysis Toolkit). A comprehensive training program was designed and setup on using PAT software as an integral key part of the analysis of data from the CMS experiment. This note summarizes the requirements and the considerations that led to establish the PAT training program, the approach taken, the main organizational issues and the experience on its implementation and maintenance. The training and the feedback has proved to be very successful both for participants and the PAT development team.

This book provides a comprehensive overview of the field of Higgs boson physics. It offers the first in-depth review of the complete results in connection with the discovery of the Higgs boson at CERN

The CMS Physics Analysis Toolkit (PAT) is presented. The PAT is a high-level analysis layer enabling the development of common analysis efforts across and within Physics Analysis Groups. It aims at fulfilling the needs of most CMS analyses, providing both ease-of-use for the beginner and flexibility for the advanced user. The main PAT concepts are described in detail and some examples from physics analyses are given.

Since 2009, the CMS experiment at LHC has provided intensive training on the use of Physics Analysis Tools (PAT), a collection of common analysis tools designed to share expertise and maximize productivity in the physics analysis. More than ten one-week courses preceded by prerequisite studies have been organized and the feedback from the participants has been carefully analyzed. This note describes how the training team designs, maintains and improves the course contents based on the feedback, the evolving analysis practices and the software development.

A search for the standard model Higgs boson decaying to tau pairs is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012 at a center-of-mass energy of 7 and 8 TeV respectively. The dataset corresponds to an integrated luminosity of 17 fb 1, split in 4.9 fb 1 of data taken at 7 TeV center-of-mass energy and 12.1 fb1 at 8 TeV. The tau-pair invariant-mass spectrum is studied in five different final states, μτh + X, eτh + X, eμ + X, τhτh + X, and μμ + X. Upper limits with respect to the standard model prediction in the mass range of 110-145 GeV are determined. An observed (expected) 95% confidence level exclusion limit for mH = 125 GeV is found to be 1.63 (1.00) times the standard model cross section.

A search for supersymmetric decays of the Z boson into a pair of scalar electrons or winos (partners of the electron and W boson) has been made with the upgraded UA2 experiment at the CERN pp collider at s= 630GeV. The analysis of the sample of electron pairs, corresponding to an integrated luminosity of 7.4 pb−1, shows no evidence for such exotic decays. The 90% confidence level lower mass limits obtained exclude selectron masses up to e40 GeV/c2 in the case of a light photino, and wino masses up to 45 GeV/c2 in the case of a light scalar neutrino.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Roger Wolf, CMS Collaboration; A tour through the CMS data model. AIP Conf. Proc. 10 December 2012; 1504 (1): 1021–1024. https://doi.org/10.1063/1.4771871 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The principle of gauge symmetries can be motivated by the Lagrangian density of the free Dirac field, which is covariant under.

The theory to describe all fundamental constituents of matter and their interactions is the Standard Model of Particle Physics (SM) Glashow, Nucl. Phys. 22:579–588, 1961, [1], Weinberg, Phys. Rev. Lett. 19:1264–1266, 1967, [2], Salam, Conf. Proc. C680519:367–377, 1968, [3]. It is a Lorentz covariant quantum field theory and as such a multi-particle theory, with operators for particle creation and destruction. It is capable not only of explaining the dynamics of elementary particles but also transitions from one particle into another, particle decays, particle annihilation or the production of new particles out of the quantum vacuum, which corresponds to the energy ground state of the theory.

With the analysis of the coupling structure of the observed particle the search for the SM Higgs boson concluded for the CMS collaboration with the complete and exhaustive analysis of the full LHC run-1 dataset of the years 2011 and 2012. The final lap of this hunt had started with the commissioning of the LHC and the experiments in 2010 and the establishment of all known SM processes with tremendous reliability and precision. The hot phase started in 2011 with the first limits based on the searches in the main SM Higgs boson decay channels, $$H\rightarrow \gamma \gamma $$ , $$H\rightarrow ZZ$$ , $$H\rightarrow WW$$ , $$H\rightarrow \tau \tau $$ and $$H\rightarrow b \bar{b}$$ , in a range of $$100<m_{H}<1000$$ GeV. These days were characterized by a vibrant atmosphere of tension and excitement at CERN, which reached its first and highest peak on 4 July 2012 with the announcement of the discovery of a new particle in both large scale main purpose experiments at the LHC, ATLAS and CMS, in the combination of the bosonic decay channels at ATLAS and all main decay channels at CMS. This discovery was based on roughly half of the dataset that has been collected across the whole timespan of the years 2011 and 2012. It was driven by the bosonic decay channels, while the two main fermionic decay channels, $$H\rightarrow \tau \tau $$ and $$H\rightarrow b\bar{b}$$ , were just around the corner to reach the sensitivity for observing the new particle. The discovery was followed by the evidence that the new particle indeed couples to fermions end of 2013 and a complete analysis of its spin, $$CP$$ properties and coupling structure, as far as possible with the available dataset.

The observations in the main SM Higgs boson decay channels as discussed in Chap. 4 have lead to the following conclusions: (i) the observation in all three bosonic decay channels is consistent with a single particle resonance; (ii) the two bosonic high mass resolution decay channels $$H\rightarrow \gamma \gamma $$ and $$H\rightarrow ZZ$$ , pin this mass to a value of $$m_{H}\approx 125$$ GeV; (iii) there is an evidence that this new particle couples to fermions, with a coupling strength to $$b$$ -quarks and $$\tau $$ -leptons as expected for a SM Higgs boson with the given mass; (iv) this coupling is non/universal across the lepton generations.

The electroweak sector of the SM, as summarized for the first generation of leptons in Eq. ( 2.48 ) has 17 open parameters.

Abstract The Gell‐Mann‐Zweig rule indicates how hadrons can be produced by quarks. This can be formulated in a bootstrap equation. A second equation which is necessary in order to eliminate one variable is found by a simple assumption about the behaviour of the quarks inside of the hadrons. Two models – a pure mesonic and a pure baryonic quark bootstrap – are presented in this paper. This material is a portion of the Ph. D. thesis submitted to the department of physics of the Universität Kaiserslautern. .

Zusammenfassung Sieben Jahre nach der Entdeckung des Higgs‐Bosons am LHC sind seine Eigenschaften weitestgehend gesichert. Es besitzt die Quantenzahlen des Vakuums und zeigt wie erwartet ein einzigartiges Kopplungsverhalten mit allen bekannten Teilchen des Standardmodells, deren Kopplung derzeit am LHC nachweisbar ist. Dieses Kopplungsverhalten konnte mit einer Messgenauigkeit von 10 bis 16 % nachgewiesen werden. Mit zunehmender Datenmenge wird diese Messgenauigkeit in den Bereich weniger Prozent vordringen. Zu den noch offenen Fragen zählen die Selbstwechselwirkung des Higgs‐Teilchens und die Suche nach weiteren Higgs‐Bosonen als Bestandteil einer Theorie jenseits des Standardmodells.

Physik in unserer ZeitVolume 51, Issue 1 p. 48-48 Magazin Von der Quantenfeldtheorie zum Standardmodell Roger Wolf, Roger Wolf KarlsruheSearch for more papers by this author Roger Wolf, Roger Wolf KarlsruheSearch for more papers by this author First published: 03 January 2020 https://doi.org/10.1002/piuz.202070112Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume51, Issue1January 2020Pages 48-48 RelatedInformation

Diffractive open-charm production apart from diffractive dijet production provides an independent way to test QCD factorization in diffraction.In this paper recent results for diffractive D * production at the HERA experiments H1 and ZEUS are summarized.They are based on data collected during the years 1998-2000 and cover the kinematic regimes of deep inelastic scattering and photoproduction.

Es werden Messungen fuer die Produktion diffraktiver D*-Mesonen in tief-inelastischer Streuung (DIS) und Photoproduktion bei HERA vorgestellt. Die Ereignis-Topologie ist durch ep – >eXY vorgegeben, wobei das zentrale System X mindestens ein D*-Meson enthaelt und deutlich durch eine Rapiditaets-Luecke vom fuehrenden System Y des gestreuten Protons getrennt ist. Die analysierten Daten wurden in den Jahren 1999 und 2000 mit dem H1-Detektor aufgenommen und entsprechen einer integrierten Luminositaet von 47.0 pb^{-1}. Die Messungen werden mit Vorhersagen der perturbativen QCD in naechst-fuehrender Ordnung (NLO) verglichen. Diese Vorhersagen basieren auf diffraktiven Parton-Dichtefunktionen, die zuvor durch eine QCD-Analyse der bei H1 gemessenen diffraktiven Strukturfunktion F_{2}^{D(3)} ermittelt wurden. Die Uebereinstimmung der QCD-Vorhersagen mit den gemessenen Wirkungsquerschnitten erweist sich als gut, was die Gueltigkeit der QCD-Faktorisierung in DIS und Photoproduktion unterstuetzt.%%%%Measurements are presented of diffractive D* meson production in deep-inelastic scattering (DIS) and photoproduction at HERA. The event topology is given by ep – >eXY where a central system X contains at least one D* meson and is well separated by a large rapidity gap from a leading low-mass proton remnant system Y. The analyzed data were collected with the H1 detector in the years 1999 and 2000 and correspond to an integrated luminosity of 47.0 pb^{-1}. The measurements are compared to QCD predictions in NLO, based on diffractive parton density functions previously obtained from a QCD analysis of the diffractive structure function F_{2}^{D(3)} at H1. A good agreement is observed in the full kinematic regime, which supports the validity of QCD factorization in DIS and photoproduction.

A racetrack totslisator is described which is capable of processing 300 bets/s from up to 1000 ticket-issuing machines. The system contains minicomputers which provide high-reliability low-cost computing power, capable of supporting the requirements of any racetrack in the United States or Canada. The computers are duplexed. Both computers process every bet and operator action. Either computer can continue processing if the other fails. The software provides extensive error checking of all hardware components. All bets are logged to magnetic tape, which can be used to restart the system in case of a system "blow." The real-time program was written in machine language and a specially developed higher level language. The master file contains 35 000 instructions. A typical program may contain 20 000 words of program and data tables. An off-Hne program is used to generate individual systems, tailored to the requirements of specific racetracks.