Jeremi Niedziela

Abstract In this work, we consider the case of a strongly coupled dark/hidden sector, which extends the Standard Model (SM) by adding an additional non-Abelian gauge group. These extensions generally contain matter fields, much like the SM quarks, and gauge fields similar to the SM gluons. We focus on the exploration of such sectors where the dark particles are produced at the LHC through a portal and undergo rapid hadronization within the dark sector before decaying back, at least in part and potentially with sizeable lifetimes, to SM particles, giving a range of possibly spectacular signatures such as emerging or semi-visible jets. Other, non-QCD-like scenarios leading to soft unclustered energy patterns or glueballs are also discussed. After a review of the theory, existing benchmarks and constraints, this work addresses how to build consistent benchmarks from the underlying physical parameters and present new developments for the pythia Hidden Valley module, along with jet substructure studies. Finally, a series of improved search strategies is presented in order to pave the way for a better exploration of the dark showers at the LHC.

This document summarises proposed searches for new physics accessible in the heavy-ion mode at the CERN Large Hadron Collider (LHC), both through hadronic and ultraperipheral $\gamma\gamma$ interactions, and that have a competitive or, even, unique discovery potential compared to standard proton-proton collision studies. Illustrative examples include searches for new particles -- such as axion-like pseudoscalars, radions, magnetic monopoles, new long-lived particles, dark photons, and sexaquarks as dark matter candidates -- as well as new interactions, such as non-linear or non-commutative QED extensions. We argue that such interesting possibilities constitute a well-justified scientific motivation, complementing standard quark-gluon-plasma physics studies, to continue running with ions at the LHC after the Run-4, i.e. beyond 2030, including light and intermediate-mass ion species, accumulating nucleon-nucleon integrated luminosities in the accessible fb$^{-1}$ range per month.

A bstract The production of dark matter particles from confining dark sectors may lead to many novel experimental signatures. Depending on the details of the theory, dark quark production in proton-proton collisions could result in semivisible jets of particles: collimated sprays of dark hadrons of which only some are detectable by particle collider experiments. The experimental signature is characterised by the presence of reconstructed missing momentum collinear with the visible components of the jets. This complex topology is sensitive to detector inefficiencies and mis-reconstruction that generate artificial missing momentum. With this work, we propose a signal-agnostic strategy to reject ordinary jets and identify semivisible jets via anomaly detection techniques. A deep neural autoencoder network with jet substructure variables as input proves highly useful for analyzing anomalous jets. The study focuses on the semivisible jet signature; however, the technique can apply to any new physics model that predicts signatures with anomalous jets from non-SM particles.

A search is presented for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of 13 TeV. The data were collected with the CMS detector during the period from 2015 through 2018, and correspond to a total integrated luminosity of 140 fb$^{-1}$. This search targets pairs of long-lived particles with mean proper decay lengths between 0.1 and 100 mm, each of which decays into at least two quarks that hadronize to jets, resulting in a final state with two displaced vertices. No significant excess of events with two displaced vertices is observed. In the context of $R$-parity violating supersymmetry models, the pair production of long-lived neutralinos, gluinos, and top squarks is excluded at 95% confidence level for cross sections larger than 0.08 fb, masses between 800 and 3000 GeV, and mean proper decay lengths between 1 and 25 mm.

A template fitting technique for reconstructing the amplitude of signals produced by the lead tungstate crystals of the CMS electromagnetic calorimeter is described. This novel approach is designed to suppress the contribution to the signal of the increased number of out-of-time interactions per beam crossing following the reduction of the accelerator bunch spacing from 50 to 25 ns at the start of Run 2 of the LHC. Execution of the algorithm is sufficiently fast for it to be employed in the CMS high-level trigger. It is also used in the offline event reconstruction. Results obtained from simulations and from Run 2 collision data (2015–2018) demonstrate a substantial improvement in the energy resolution of the calorimeter over a range of energies extending from a few GeV to several tens of GeV.

A bstract We investigate the discovery potential for long-lived particles produced in association with a top-antitop quark pair at the (High-Luminosity) LHC. Compared to inclusive searches for a displaced vertex, top-associated signals offer new trigger options and an extra handle to suppress background. We design a search strategy for a displaced di-muon vertex in the tracking detectors, in association with a reconstructed top-antitop pair. For axion-like particles with masses above the di-muon threshold, we find that the (High-Luminosity) LHC can probe effective top-quark couplings as small as | c tt |/ f a = 0 . 03 (0 . 002)/TeV and proper decay lengths as long as 20 (300) m, assuming a cross section of 1 fb, with data corresponding to an integrated luminosity of 150 fb − 1 (3 ab − 1 ). Our predictions suggest that searches for top-associated displaced di-muons will explore new terrain in the current sensitivity gap between searches for prompt di-muons and missing energy.

ALICE (A Large Ion Collider Experiment) is the detector system at the LHC (Large Hadron Collider) optimized for the study of heavy-ion collisions at interaction rates up to 50 kHz and data rates beyond 1 TB/s. Its main aim is to study the behavior of strongly interacting matter and the quark gluon plasma. ALICE is preparing a major upgrade and starting from 2021, it will collect data with several upgraded sub-detectors (TPC, ITS, Muon Tracker and Chamber, TRD and TOF). The ALICE DAQ read-out system will be upgraded as well, with a new read-out link called GBT (GigaBit Transceiver) with a max. speed of 4.48 Gb/s and a new PCIe gen.3 ×16, interface card called CRU (Common Read-out Unit). Several test beams have been scheduled for the test and characterization of the prototypes or parts of new detectors. The test beams usually last for a short period of one or two weeks and it is therefore very important to use a stable read-out system to optimize the data taking period and be able to collect as much statistics as possible. The ALICE DAQ and CRU teams proposed a data acquisition chain based on the current ALICE DAQ framework in order to provide a reliable read-out system. The new GBT link, transferring data from the front-end electronics, will be directly connected to the C-RORC, the current read-out PCIe card used in the ALICE experiment. The ALICE DATE software is a stable solution in production since more than 10 years. Moreover, most of the ALICE detector developers are already familiar with the software and its different analysis tools. This setup will allow the detector team to focus on the test of their detectors and electronics, without worrying about the stability of the data acquisition system. An additional development has been carried on with a C-RORC-based Detector Data Generator (DDG). The DDG has been designed to be a realistic data source for the GBT. It generates simulated events in a continuous mode and sends them to the DAQ system through the optical fibers, at a maximum of 4.48 Gb/s per GBT link. This hardware tool will be used to test and verify the correct behavior of the new DAQ readout card, CRU, once it will become available to the developers. Indeed the CRU team will not have a real detector electronics to perform communication and performance tests, so it is vital during the test and commissioning phase to have a data generator able to simulate the FEE behavior. This contribution will describe the firmware and software features of the proposed read-out system and it will explain how the read-out chain will be used in the future tests and how it can help the development of the new ALICE DAQ software.

Successful implementation of a beam-based alignment algorithm, tailored to different types of quadrupoles at RHIC, provides significant benefits to machine operations for heavy ions and polarized protons. This algorithm was used to calibrate beam position monitor centers relative to interaction region quadrupoles to maximize aperture. This approach was also used to determine the optimal or bit through transition jump quadrupoles to minimize orbit changes during the transition jump for heavy ion acceleration. This paper provides background discussion and results from first measurements during the RHIC 2005 run.

We investigate the discovery potential for long-lived particles produced in association with a top-antitop quark pair at the (High-Luminosity) LHC. Compared to inclusive searches for a displaced vertex, top-associated signals offer new trigger options and an extra handle to suppress background. We design a search strategy for a displaced di-muon vertex in the tracking detectors, in association with a reconstructed top-antitop pair. For axion-like particles with masses above the di-muon threshold, we find that the (High-Luminosity) LHC can probe effective top-quark couplings as small as $|c_{tt}|/f_a = 0.03(0.002)/$TeV and proper decay lengths as long as $20(300)$ m, assuming a cross section of $1$ fb, with data corresponding to an integrated luminosity of 150 fb$^{-1}$ (3 ab$^{-1}$). Our predictions suggest that searches for top-associated displaced di-muons will explore new terrain in the current sensitivity gap between searches for prompt di-muons and missing energy.

The shape of the baryon-(anti)baryon femtoscopic correlation function is influenced by the size of the emission source, strong and Coulomb interactions and Quantum Statistics. Another factor introducing additional correlation structures is related to the residual correlations, which are related to the fact that baryons may come from decays of heavier particles. The correlation function of a given pair of baryons (for example p p ) is closely connected with correlation functions of other particles (such as p Λ ). Analysing correlation functions of multiple baryon pairs simultaneously can further constrain measured strong scattering parameters. A newly developed fitting procedure allowing for a combined fit of several correlation functions is presented. The procedure was applied to 2.76 TeV and 5.02 TeV Pb-Pb data measured by ALICE. The analysis was performed for all combinations of (anti)protons and (anti)lambdas for different collision centralities. Measured strong interaction parameters for p Λ , ΛΛ and heavier baryon-antibaryon (b b ) pairs are shown and possible underlying physical processes are discussed.

Accurate alignment of the electron and ion beams in the RHIC electron cooling solenoids is crucial for well-optimized cooling. Because of the greatly differing rigidities of the electron and ion beams, to achieve the specified alignment accuracy it is required that transverse magnetic fields resulting from imperfections in solenoid fabrication be down by five orders of magnitude relative to the pure solenoid fields. Shimming the solenoid field to this accuracy might be accomplished by survey techniques prior to operation with beam, or by methods of beam-based alignment. We report on the details of a method of beam-based alignment, as well as the results of preliminary measurements with the ion beam at RHIC.

A Large Ion Collider Experiment (ALICE) is one of the four big experiments running at the Large Hadron Collider (LHC), which focuses on the study of the Quark-Gluon Plasma (QGP) being produced in heavy-ion collisions. The ALICE Event Visualisation Environment (AliEve) is a tool providing an interactive 3D model of the detector's geometry and a graphical representation of the data. Together with the online reconstruction module, it provides important quality monitoring of the recorded data. As a consequence it has been used in the ALICE Run Control Centre during all stages of Run 2. Static screenshots from the online visualisation are published on the public website - ALICE LIVE. Dedicated converters have been developed to provide geometry and data for external projects. An example of such project is the Total Event Display (TEV) - a visualisation tool recently developed by the CERN Media Lab based on the Unity game engine. It can be easily deployed on any platform, including web and mobile platforms. Another external project is More Than ALICE - an augmented reality application for visitors, overlaying detector descriptions and event visualisations on the camera's picture. For the future Run 3 both AliEve and TEV will be adapted to fit the ALICE O2 project. Several changes are required due to the new data formats, especially so-called Compressed Time Frames.

Centralization of information pertaining to accelerators can benefit accelerator operation and development. Further, retention and the changeable nature of information present challenges to accelerator operation, particularly in instances of turnover. MediaWiki is free, server-based software licensed under the GNU general public license that uses PHP to render data stored in a MySQL database as interactive web documents, and is designed to produce a collaborative document known as a wiki. The MediaWiki engine was implemented at BNL, and this paper describes the first year of use by the operations, controls, and RF groups at the collider- accelerator department, including code modifications, common practices, and use as a training tool.

and 8 stripline beam position monitors (BPMs) per accelerator. An SVD-based algorithm was used to compute the applied corrections. For Run-10, the response matrix was provided by W. W. MacKay. The response matrix R relates corrector angles to beam displacements at BPMs.

A Large Ion Collider Experiment (ALICE) is the heavy-ion detector designed to study the physics of strongly interacting matter and the quark-gluon plasma at the CERN Large Hadron Collider (LHC). The online Data Quality Monitoring (DQM) plays an essential role in the experiment operation by providing shifters with immediate feedback on the data being recorded in order to quickly identify and overcome problems.

The ALICE experiment is a complex hardware and software device, monitored and operated with a control system based on WinCC OA. ALICE is composed of 19 detectors and installed in a cavern along the LHC at CERN; each detector is a logical set of modular elements, assembled in a hierarchical model called Finite State Machine. A 3-D model of the ALICE detector has been realized, where all elements of the FSM are represented in their relative location, giving an immediate overview of the status of the detector. For its simplicity, it can be a useful tool for the training of operators. The development is done using WinCC OA integrated with the JCOP fw3DViewer, based on the AliRoot geometry settings. Extraction and conversion of geometry data from AliRoot requires the usage of conversion libraries, which are currently being implemented. A preliminary version of ALICE 3-D is now deployed on the operator panel in the ALICE Run Control Centre. In the next future, the 3-D panel will be available on a big touch screen in the ALICE Visits Centre, providing visitors with the unique experience of navigating the experiment from both inside and out.

In modern High Energy Physics (HEP) experiments visualization of experimental data has a key role in many activities and tasks across the whole data chain: from detector development to monitoring, from event generation to reconstruction of physics objects, from detector simulation to data analysis, and all the way to outreach and education. In this paper, the definition, status, and evolution of data visualization for HEP experiments will be presented. Suggestions for the upgrade of data visualization tools and techniques in current experiments will be outlined, along with guidelines for future experiments. This paper expands on the summary content published in the HSF \emph{Roadmap} Community White Paper~\cite{HSF-CWP-2017-01}

A measurement of light-by-light scattering, γγ → γγ, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported.The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 µb -1 recorded by the CMS experiment at the LHC.Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy E T > 2 GeV, pseudorapidity | η |< 2.4, diphoton invariant mass m γγ > 5 GeV, diphoton transverse momentum p T < 1 GeV, and diphoton acoplanarity below 0.01.After all selection criteria are applied, 14 events are observed, compared to expectations of 11.1 ± 1.1 (th) events for the signal and 4.0 ± 1.2 (stat) for the background processes.The significance of the light-by-light signal hypothesis against the background-only hypothesis is 4.1 standard deviations.The measured fiducial light-by-light scattering cross section, σ f id (γγ → γγ) = 120 ± 46 (stat) ± 29 (syst) ± 4 (th) nb is consistent with the Standard Model prediction.The present results allow also to place new competitive limits, reported for the first time, on the production of pseudoscalar axion-like particles, produced in the process γγ → a → γγ, over the mass range m a = 5 -50 GeV.

In modern High Energy Physics (HEP) experiments visualization of experimental data has a key role in many activities and tasks across the whole data chain: from detector development to monitoring, from event generation to reconstruction of physics objects, from detector simulation to data analysis, and all the way to outreach and education. In this paper, the definition, status, and evolution of data visualization for HEP experiments will be presented. Suggestions for the upgrade of data visualization tools and techniques in current experiments will be outlined, along with guidelines for future experiments. This paper expands on the summary content published in the HSF \emph{Roadmap} Community White Paper~\cite{HSF-CWP-2017-01}