G. Pásżtor

At the Large Hadron Collider (LHC), absolute luminosity calibrations obtained by the van der Meer (vdM) method are affected by the mutual electromagnetic interaction of the two beams. The colliding bunches experience relative orbit shifts, as well as optical distortions akin to the dynamic-$\beta$ effect, that both depend on the transverse beam separation and must therefore be corrected for when deriving the absolute luminosity scale. In the vdM regime, the beam-beam parameter is small enough that the orbit shift can be calculated analytically. The dynamic-$\beta$ corrections to the luminometer calibrations, however, had until the end of Run 2 been estimated in the linear approximation only. In this report, the influence of beam-beam effects on the vdM-based luminosity scale is quantified, together with the associated systematic uncertainties, by means of simulations that fully take into account the non-linearity of the beam-beam force, as well as the resulting non-Gaussian distortions of the transverse beam distributions. Two independent multiparticle simulations, one limited to the weak-strong approximation and one that models strong-strong effects in a self-consistent manner, are found in excellent agreement; both predict a percent-level shift of the absolute pp-luminosity values with respect to those assumed until recently in the physics publications of the LHC experiments. These results also provide guidance regarding further studies aimed at reducing the beam-beam-related systematic uncertainty on beam-beam corrections to absolute luminosity calibrations by the van der Meer method.

Optimum conditions for the glycolysis of polyurethane flexible foams and elastomers are reported. The crude, two-phase liquid reaction mixture was separated and the upper phase was used as the polyol component of an industrial adhesive mixture. During glycolysis the formation of carbon dioxide was recognized and quantified. On the basis of this new finding a novel reaction mechanism is proposed for the glycolysis of polyurethanes.

The high-luminosity upgrade of the LHC brings unprecedented requirements for real-time and precision bunch-by-bunch online luminosity measurement and beam-induced background monitoring. A key component of the CMS Beam Radiation, Instrumentation and Luminosity system is a stand-alone luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent from the CMS central trigger and data acquisition services and able to operate at all times with a triggerless readout. FBCM utilizes a dedicated front-end application-specific integrated circuit (ASIC) to amplify the signals from CO$_2$-cooled silicon-pad sensors with a timing resolution of a few nanoseconds, which enables the measurement of the beam-induced background. FBCM uses a modular design with two half-disks of twelve modules at each end of CMS, with four service modules placed close to the outer edge to reduce radiation-induced aging. The electronics system design adapts several components from the CMS Tracker for power, control and read-out functionalities. The dedicated FBCM23 ASIC contains six channels and adjustable shaping time to optimize the noise with regards to sensor leakage current. Each ASIC channel outputs a single binary high-speed asynchronous signal carrying time-of-arrival and time-over-threshold information. The chip output signal is digitized, encoded and sent via a radiation-hard gigabit transceiver and an optical link to the back-end electronics for analysis. This paper reports on the updated design of the FBCM detector and the ongoing testing program.

Abstract The high-luminosity upgrade of the LHC brings unprecedented requirements for real-time and precision bunch-by-bunch online luminosity measurement and beam-induced background monitoring. A key component of the CMS Beam Radiation, Instrumentation and Luminosity system is a stand-alone luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent from the CMS central trigger and data acquisition services and able to operate at all times with a triggerless readout. FBCM utilizes a dedicated front-end application-specific integrated circuit (ASIC) to amplify the signals from CO 2 -cooled silicon-pad sensors with a timing resolution of a few nanoseconds, which enables the measurement of the beam-induced background. FBCM uses a modular design with two half-disks of twelve modules at each end of CMS, with four service modules placed close to the outer edge to reduce radiation-induced aging. The electronics system design adapts several components from the CMS Tracker for power, control and read-out functionalities. The dedicated FBCM23 ASIC contains six channels and adjustable shaping time to optimize the noise with regards to sensor leakage current. Each ASIC channel outputs a single binary high-speed asynchronous signal carrying time-of-arrival and time-over-threshold information. The chip output signal is digitized, encoded, and sent via a radiation-hard gigabit transceiver and an optical link to the back-end electronics for analysis. This paper reports on the updated design of the FBCM detector and the ongoing testing program.

Arrays of thin scintillating tiles with embedded wavelength shifting fibre readout have been installed in the OPAL endcaps to improve trigger performance, time resolution and hermeticity for experiments at LEP II. The arrays were required to have high single-particle detection efficiency, uniform response, low noise and good time resolution. Limited space for the detector, and a strong magnetic field in the endcap region, resulted in a need for high light output per unit thickness of scintillator, and remote readout. In addition, because of limited space for readout cables, a high light yield per embedded fibre was required. This paper describes the design and construction of a tile array that satisfies these requirements. A light yield of 14 photoelectrons per minimum ionizing particle and a time resolution of 3 ns were obtained during 1997 LEP operation.

The Pixel Luminosity Telescope is a silicon pixel detector dedicated to luminosity measurement at the CMS experiment at the LHC. It is located approximately 1.75 m from the interaction point and arranged into 16 "telescopes", with eight telescopes installed around the beam pipe at either end of the detector and each telescope composed of three individual silicon sensor planes. The per-bunch instantaneous luminosity is measured by counting events where all three planes in the telescope register a hit, using a special readout at the full LHC bunch-crossing rate of 40 MHz. The full pixel information is read out at a lower rate and can be used to determine calibrations, corrections, and systematic uncertainties for the online and offline measurements. This paper details the commissioning, operational history, and performance of the detector during Run 2 (2015-18) of the LHC, as well as preparations for Run 3, which will begin in 2022.

These two data sets provide the coefficients of the parameterisation of the (L/L₀)_Opt luminosity-bias factor as a function of the normalized nominal separation, for horizontal and vertical vdM scans, respectively. The data sets are part of a paper with title "Impact of Beam-Beam Effects on Absolute Luminosity Calibrations at the CERN Large Hadron Collider" and are referred thereby as Table 10 and Table 11.

Although ecologists have been aware for almost 20 years that population densities may evolve in a chaotic way, the evidence for chaos in natural populations is rather poor. The lack of convincing evidence may have its origin in the difficulty of estimating the effect of external environmental noise, but it may also reflect natural regulation processes. In this paper we present a metapopulation-dynamical model, in which the nearest neighbor local population fragments interact by applying a threshold condition. Namely, each local population follows its own temporal evolution until a critical population density is reached, which initiates dispersal (migration) events to the neighbors. The type of interaction is common to self-organized critical cellular automaton models. Depending on the threshold level, the global behavior of our model can be characterized either by noisy dynamics with many degrees of freedom, by a periodical evolution, or by an evolution towards a fixed point. Low dimensional collective chaos does not occur. Moreover, self-organized criticality with power law distributions emerges if the interaction between the neighboring local populations is strong enough.

Correlations among hadrons with the same electric charge produced in Z0 decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized factorial cumulants up to fourth order are used to measure genuine particle correlations as a function of the size of phase space domains in rapidity, azimuthal angle and transverse momentum. Both all-charge and like-sign particle combinations show strong positive genuine correlations. One-dimensional cumulants initially increase rapidly with decreasing size of the phase space cells but saturate quickly. In contrast, cumulants in two- and three-dimensional domains continue to increase. The strong rise of the cumulants for all-charge multiplets is increasingly driven by that of like-sign multiplets. This points to the likely influence of Bose–Einstein correlations. Some of the recently proposed algorithms to simulate Bose–Einstein effects, implemented in the Monte Carlo model Pythia, are found to reproduce reasonably well the measured second- and higher-order correlations between particles with the same charge as well as those in all-charge particle multiplets.

for the CMS CollaborationThe high-luminosity upgrade of the Large Hadron Collider (HL-LHC) will provide a unique opportunity to extend the physics reach of the CMS experiment by achieving unprecedented precision in the study of Standard Model (SM) processes and by increasing its discovery potential for physics beyond the SM to higher energy scales and rarer processes.The HL-LHC, however, will also bring experimental and instrumental challenges with its harsh environment: high radiation levels, high number of particle collisions per bunch crossing (pileup of 140-200), and extreme final state particle multiplicities.The CMS Collaboration has embarked on an ambitious upgrade program to improve the spatial granularity and timing resolution, to extend the coverage of precision detectors to higher absolute pseudorapidities ( ), to increase the data rate that can be recorded, while using more robust and more radiation hard technologies.In this paper, the main features of the CMS Phase-2 upgrade are reviewed.New high-granularity detectors will be installed: a silicon pixel and strip tracker with larger coverage (| | < 4), an imaging endcap calorimeter (1.5 < | | < 3), an extended muon system in the forward region (| | < 2.8) including Gas Electron Multiplier detectors.The timing precision will also be significantly enhanced by dedicated timing detectors with 30-50 ps resolution (| | < 3), supplemented by improved timing information from muon detectors and calorimeters with upgraded electronics.Fully reconstructed tracks with transverse momentum of T > 2 GeV and particle-flow at the level-1 hardware trigger will enable more efficient online event selection, with an increased level-1 rate (750 kHz) and latency (12.5 s).Trigger objects will be available at 40 MHz for monitoring and restricted data analysis through a Scouting System.The high-level trigger with a heterogeneous architecture will provide a 7.5 kHz output rate to benefit from the increased luminosity.

These two data sets provide the coefficients of the parameterisation of the (L/L₀)_Opt luminosity-bias factor as a function of the normalized nominal separation, for horizontal and vertical vdM scans, respectively. The data sets are part of a paper with title "Impact of Beam-Beam Effects on Absolute Luminosity Calibrations at the CERN Large Hadron Collider" and are referred thereby as Table 10 and Table 11.

This document summarises the talks and discussions happened during the VBSCan Mid-Term Scientific Meeting workshop. The VBSCan COST action is dedicated to the coordinated study of vector boson scattering (VBS) from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV - 1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV-scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence.

This document summarises the talks and discussions happened during the VBSCan Mid-Term Scientific Meeting workshop. The VBSCan COST action is dedicated to the coordinated study of vector boson scattering (VBS) from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

This document specifies the functionality which will be required of the final Front End Drivers (FEDs) for the Tracker, and explains the motivation behind each of these requirements. Furthermore, it lists all the input/output signals which these FEDs must deal with. Also discussed is the issue of what subset of this functionality will be in the first version of the final FED (FF1), which will be used for rod/petal testing in 2002. Not addressed in this document are details of the implementation. This will be described in a separate ‘FED Specifications’ document.

Electron and photon triggers covering transverse energies from 5 GeV to several TeV are essential for signal selection in a wide variety of ATLAS physics analyses to study Standard Model processes and to search for new phenomena. Final states including leptons and photons had, for example, an important role in the discovery and measurement of the Higgs particle. Dedicated triggers are also used to collect data for calibration, efficiency and fake rate measurements. The ATLAS trigger system is divided in a hardware-based (Level 1) and a software based High-Level Trigger (HLT), both of which were upgraded during the long shutdown of the LHC in preparation for data taking in 2015. The increasing luminosity and more challenging pile-up conditions as well as the higher center-of-mass energy demanded the optimisation of the trigger selections at each level, to control the rates and keep efficiencies high. To improve the performance, multivariate analysis techniques were introduced at the HLT. The evolution of the ATLAS electron and photon triggers and their performance is presented, including initial results from the early days of the LHC Run 2 operation.

The CERN LHC delivered 25/fb of proton-proton collision data in 2011-2012 at sqrt{s} = 7 - 8 TeV centre-of-mass energy to the ATLAS detector. These Run 1 data were used to discover the Higgs boson and measure its properties as well as to perform numerous other tests of the Standard Model via precision measurements and searches for New Physics. In preparation for the Run 2 data taking at sqrt{s} = 13 TeV, the collaboration embarked on an upgrade program during the long LHC machine shutdown in 2013-2015. The early 2015 data set was then used to promptly recommission the apparatus allowing the first physics results to appear already in the summer of 2015. After briefly reviewing the upgrade and the improved performance of the detector, this paper concentrates on the final Run~1 results on Higgs, W and Z boson, electroweak multi-boson and top quark production as well as on searches for supersymmetry and other new phenomena.

In this report we summarize the work performed at Snowmass 2001 on the physics of extra dimensions. We divide these analyses into the following classes: searches for extra dimensional phenomena, identification of specific new physics scenarios, studies of black hole production and non-commutative QED.

Searches for pair-produced charginos neutralinos and scalar fermions decaying via R-parity violating λ, λ′ and λ′′ couplings with the OPAL detector at LEP are presented at [Formula: see text]. Partial updates using data up to the highest energies of LEP, [Formula: see text], are also given.

If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV-1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV-scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence.

The latest results on searches for supersymmetry, extra dimensions and exotic phenomena from the LEP collaborations are presented. No significant signal-like excess is observed in the data. The results are interpreted in various models and robust constraints are placed.

The discovery potential of the CMS detector for the MSSM neutral and charged Higgs bosons at the LHC is presented based on studies with full detector simulation and event reconstruction of the principal discovery channels.

In this Snowmass contribution we present a comprehensive status update on the progress and plans for the proposed CODEX-b detector, intended to search for long-lived particles beyond the Standard Model. We review the physics case for the proposal and present recent progress on optimization strategies for the detector and shielding design, as well as the development of new fast and full simulation frameworks. A summary of the technical design for a smaller demonstrator detector (CODEX-$\beta$) for the upcoming Run~3 of the LHC is also discussed, alongside the road towards realization of the full experiment at the High-Luminosity LHC.

Data collected by the OPAL detector at LEP up to the highest energies of 209 GeV are analyzed to search for evidence of supersymmetric (SUSY) particle production. Chargino pair-production (e+e−→ χ 1 χ − 1 ) and neutralino associated production (e +e−→ χ0 1 χ 0 2 ) are considered in models where supersymmetry breaking is mediated by gravitational interactions from the hidden sector to the visible sector of the Standard Model and SUSY particles. R-parity conservation is assumed. The focus of the searches is on topologies arising when scalar fermions are heavy and the lightest neutralino is the lightest SUSY particle (LSP). Searches for topologies predicted by gauge-mediated SUSY breaking (GMSB) models are also discussed. In these models the LSP is the gravitino and the phenomenology is driven by the nature of the next-to-lightest SUSY particle (NLSP) which is either the lightest neutralino, stau or mass degenerate sleptons. As the NLSP decay length is effectively unconstrained, all possible values are considered and results independent of the NLSP lifetime are presented for all relevant final states including direct NLSP pair-production and NLSP production via cascade decays of heavier SUSY particles. None of the searches shows evidence for SUSY particle production. Cross-section limits are presented at the 95% confidence level both for direct NLSP production and, for the first time, also for cascade decays, providing the most general, almost model independent results. These are then interpreted in the framework of minimal theoretical models. Large areas of the accessible parameter space are excluded. In the super-gravity inspired Constrained MSSM (CMSSM) we derive the following limits for m0 > 500 GeV, A0 = 0 and ∆M > 5 GeV on the lightest gaugino masses: mχ± 1 > 101 GeV, mχ0 1 > 40 GeV and mχ0 2 > 78 GeV, independent of tanβ . In the minimal GMSB model, the NLSP masses are constrained to be mχ0 1 > 53.5 GeV, mτ1 > 87.4 GeV and m > 91.9 GeV in the neutralino, stau and slepton co-NLSP scenarios, respectively.

Precision measurements provide a critical test of the consistency and limits of validity of the Standard Model (SM) and could point toward New Physics and constrain the parameters of the extensions of the SM. The ultimate aim is to measure directly the electroweak mixing angle ($\theta_\mathrm{W}$) and the mass of the $W$ boson ($m_W$) with a precision that is competitive with the global fit uncertainties. To achieve an excellent understanding of experimental and parton distribution function uncertainties affecting the determination of $\sin^2\theta_\mathrm{W}$ and $m_W$, a rich program of $Z$ and $W$ boson studies are performed, including the measurements of differential production cross-sections as a function of various kinematic variables (like the transverse boson momenta, rapidity and additional jet variables), the $Z\rightarrow\ell^+\ell^-$ angular coefficients and forward - backward asymmetry as well as the $W$ boson production charge asymmetry. Recent results using the LHC Run 1 and Run 2 data are summarised in this article from the ATLAS and CMS collaborations.

Latest results from the LEP Collaboration on searches for neutral Higgs bosons predicted by the Standard Model and its minimal supersymmetric extension, the MSSM, are summarized.

A selection of recent results on searches for phenomena beyond the Standard Model is presented from the LEP Collaborations, based on the data collected up to the highest centre-of-mass energies of 209 GeV.

The CMS collaboration is constructing the largest silicon tracker ever built with an active silicon area of 200 m^2 to provide robust charged particle tracking and vertex reconstruction within the 4T magnetic field of the CMS Solenoid. The design of the detector, the status of the construction and the performance of the substructures are reviewed.

Data collected by the OPAL detector at LEP up to the highest energies of 209 GeV are analyzed to search for evidence of supersymmetric (SUSY) particle production. Chargino pair-production and neutralino associated production are considered in models where supersymmetry breaking is mediated by gravitational interactions. The focus of the searches is on topologies arising when scalar fermions are heavy and the lightest neutralino is the lightest SUSY particle (LSP). Searches for topologies predicted by gauge-mediated SUSY breaking (GMSB) models are also discussed. In these models the LSP is the gravitino and the phenomenology is driven by the nature of the next-to-lightest SUSY particle (NLSP) which is either the lightest neutralino, stau or mass degenerate sleptons. As the NLSP decay length is effectively unconstrained, all possible values are considered and results independent of the NLSP lifetime are presented for all relevant final states including direct NLSP pair-production and NLSP production via cascade decays of heavier SUSY particles. None of the searches shows evidence for SUSY particle production. Cross-section limits are presented at the 95% confidence level both for direct NLSP production and, for the first time, also for cascade decays. These are then interpreted in the framework of minimal theoretical models. Large areas of the accessible parameter space are excluded and constraints on the mass of the SUSY particles are derived.

The high-luminosity upgrade of the LHC (HL-LHC) is foreseen to reach an instantaneous luminosity a factor of five to seven times the nominal LHC design value.The resulting, unprecedented requirements for background monitoring and luminosity measurement create the need for new high-precision instrumentation at CMS, using radiation-hard detector technologies.This contribution presents the strategy for bunch-by-bunch online luminosity measurement based on various detector technologies.A main component of the system is the tracker endcap pixel detector (TEPX) with an additional 75 kHz of dedicated triggers for online measurement of luminosity and beam-induced background.Real-time implementations of algorithms such as pixel cluster counting on an FPGA are explored for online processing of the resulting data.The potential of the exploitation of the outer tracker, the hadron forward calorimeter and muon trigger objects is also discussed.

A study of Z boson pair production in e + e - annihilation using the OPAL detector at LEP is reported . The ZZ production cross-section is measured, limits on anomalous ZZ γ and ZZZ couplings are derived, and constraints on models of low scale quantum gravity in extra spatial dimensions are set.

A study of Z boson pair production in e+e- annihilation using the OPAL detector at LEP is reported. The ZZ production cross-section is measured, limits on anomalous ZZgamma and ZZZ couplings are derived, and constraints on models of low scale quantum gravity in extra spatial dimensions are set.

LBNL-49222 Exploring New Physics Through Contact Interactions in Lepton Pair Production at a Linear Collider Gabriella P´ sztor ∗ a CERN, CH-1211 Geneva 23, Switzerland Maxim Perelstein † Theory Group, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA (Dated: July 10, 2004) If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV − 1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV- scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence. arXiv:hep-ph/0111471 v2 4 Dec 2001 I. INTRODUCTION All known solutions to the gauge hierarchy problem of the Standard Model (SM) require the appearance of new particles at energy scales around 1 TeV. It is not guaranteed, however, that these new particles can be produced directly at the proposed 500 GeV linear collider (LC). Only for supersymmetric theories are there strong arguments that at least some superpartners should be kinematically accessible at such a collider [1]. In the case of composite Higgs models and models with extra dimensions, the situation is far less certain. It is possible that all the new states predicted in these theories are too heavy and cannot appear in the final state at a 500 GeV LC. In fact, for models with large extra dimensions [2], current experimental constraints most likely rule out the possibility that string Regge excitations could be lighter than 500 GeV. In this case, the only direct effect of extra dimensions would be the enhanced rate of events with missing energy due to graviton emission. These events, however, provide only very limited amount of information about the fundamental theory. Moreover, this signature could be mimicked by gravitino emission processes in certain supersymmetric models, so one would need additional handles to disentangle the underlying physics [3]. In this situation, it is important to look for indirect effects of new physics, that is, the effects of new heavy particles appearing as virtual states. For example, processes such as Bhabha scattering or other lepton pair production, e + e − → e + e − , µ + µ − , τ + τ − could receive an additional contribution from the exchange of a heavy state X. Because such additional con- tributions come from short-distance physics and do not possess poles in the accessible range of any kinematic variables, they are referred to as contact interactions. By carefully examining the total cross section and angular distribution of these processes, it should be possible to not only find deviations from the Standard Model, but also gain some information about the nature of the state X, such as its spin and couplings. In this report, we will assume that the cross section of process (1) was found to deviate from the Standard Model prediction. We will then consider several possible explanations for this deviation, such as models with lepton substructure, models with TeV-scale strings, and models in which gauge fields can propagate in the extra dimensions. Our main goal is to determine how well one can discriminate between these possibilities, given the measurement of the total cross section and angular distributions of the final-state particles. II. MODELS WITH CONTACT INTERACTIONS The unpolarised cross section formula for Bhabha scattering can be written in the form dσ u (|A LL | 2 + |A RR | 2 ) + 2t 2 |A RL,s | 2 + 2s 2 |A RL,t | 2 , d cos θ 2s ∗ Gabriella.Pasztor@cern.ch; † meperelstein@lbl.gov On leave of absence from KFKI RMKI, Budapest, Hungary.

Searches for Higgs bosons at the e+e− collider LEP at centre-of-mass energies above the Z0 resonance are reviewed. No evidence for Higgs boson production has been found so far. Preliminary results obtained by the four LEP experiments, ALEPH, DELPHI, L3 and OPAL, are presented.