Search

Dark matter research, aimed at unraveling astrophysical enigmas, faces the challenge of lacking concrete evidence connecting dark matter with the observable universe in both experimental and theoretical particle physics. Our study investigates a simplified extension to the Standard Model (SM) where SM fermion interacts with a hypothetical vector dark matter (DM) particle in high-energy collisions, mediated by a proposed massive spin-1 particle, Z ′ . We specifically explore vector DM pair production through fermion annihilation in this mediator, focusing on a near-resonance condition ( m χ ∼ M Z ′ / 2 ). This includes examining monophoton production, a SM signal, as a result of initial-state radiation. We also calibrate the coupling constants between DM and SM particles relative to Planck satellite thermal relic density data, particularly near a resonance where traditional models anticipate more relic density suppression. Our findings, consistent with expected relic density at resonance regimes, suggest mass ranges and coupling constants for these DM particles that align with collider and astrophysical limits, to be validated in CLIC and LHC settings. [ABSTRACT FROM AUTHOR]

Objectives: We provide a brief overview of collider bias and its implications for criminological research. Methods: Owing to the nature of the topics studied, as well as the common data sources used to carry out much of this research, work in the field may often become vulnerable to a specific methodological problem known as collider bias. Collider bias occurs when exposure variables and outcomes independently cause a third variable, and this variable is included in statistical models. Colliders represent somewhat of a paradox in that there is scholarship discussing the issue, yet it has managed to remain a relatively cryptic threat compared to other sources of bias. Results: We argue that, far from being an obscure concern, colliders almost certainly have pervasive impact in criminal justice and criminology. Conclusion: We close by offering a general set of strategies for addressing the challenges posed by collider bias. While there is no panacea, there are better practices, many of which are underutilized in the disciplines that study crime and its attendant topics. [ABSTRACT FROM AUTHOR]

Research Summary: Collider bias can cause spurious correlations when researchers condition on a variable that is caused by—or shares a common cause with—both the outcome and the exposure variable. Despite its threat to inference, empirical research in strategy and management has largely overlooked the issue of collider bias. We distinguish colliders from other threats to identification and estimation and illustrate its importance with replications of published work suggesting that having a woman CEO reduces the career outcomes (compensation and representation) of other women executives. After accounting for collider bias, we find no evidence that women CEOs damage the career outcomes of other women in their organizations. We close by providing generalizable approaches to identify and mitigate the risk of collider bias in applied research. Managerial Summary: Collider bias is a type of statistical problem that can generate misleading results in empirical research. Although research in strategy and management has given substantial attention to other types of statistical problems, the issue of collider bias has not received sufficient scrutiny. We illustrate this point with replications of published work suggesting that having a woman CEO reduces the career outcomes of other women executives. After accounting for collider bias, we find no evidence that women CEOs damage the career outcomes of other women in their organizations. We provide advice for detecting and addressing collider bias in empirical research. [ABSTRACT FROM AUTHOR]

Throughout the second half of the 20th century, clinicians noted that although African-American neonates were more likely than White neonates to weigh less than 2,500 g at birth (low birth weight), among low–birth-weight infants African Americans were more likely than Whites to survive. However, when born at normal weight, African-American infants were substantially less likely to survive. The observation generated much physiological speculation, and several clever mathematical manipulations were devised to "uncross the mortality curves." With the development and dissemination of directed acyclic graphs in the early 2000s, methodologists focusing on perinatal epidemiology showed graphically, in an early use of directed acyclic graphs, that birth weight was a "collider" and that controlling for birth weight, whether by regression, stratification, or restriction, introduced confounding of the race-mortality association by all unmeasured common causes of birth weight and mortality. These investigations showed that the crossing curves could be explained as an artifact of a conceptually flawed analysis. These results have applicability beyond perinatal epidemiology, including applicability to the "obesity paradox." [ABSTRACT FROM AUTHOR]

Lepton flavor universality exists in the Standard Model, and hence any observation of the violation of this universality will be a hint for new physics. Recent experimental searches for processes violating this symmetry have attracted much attention among theorists and experimentalists alike. In recent years, such hints have been observed in flavor changing neutral current weak processes such as b → s l l and charged current weak processes such as b → c l ν processes by collider experiments like Belle, Belle II, BaBar, LHCb, ATLAS, and CMS collaborations, where b , s , c are the bottom, strange, and charm quarks, respectively, and l , ν stand for lepton and the corresponding lepton neutrino, respectively. This article is a review of some of the interesting anomalies observed in the B-sector and includes decays of B s mesons. [ABSTRACT FROM AUTHOR]

High-energy colliders provide direct access to the energy frontier, allowing to search for new physics at scales as high as the machine’s center-of-mass energy, perform precision measurements of the Standard Model (SM) parameters, including those related to the flavor sector, and determine the Higgs boson properties and their connection to electroweak symmetry breaking. Each proposed future collider option has its own specific science goals and capabilities, depending on the designed running energy (energies) amongst other parameters. In this paper, an overview of the discovery potential of future circular and linear colliders is presented. Results from searches for beyond the Standard Model (BSM) phenomena at proton–proton, proton–electron, electron–positron, and muon–antimuon colliders are summarized.

Highly granular pixel detectors allow for increasingly precise measurements of charged particle tracks. Next-generation detectors require that pixel sizes will be further reduced, leading to unprecedented data rates exceeding those foreseen at the High- Luminosity Large Hadron Collider. Signal processing that handles data incoming at a rate of $\mathcal{O}$ (40 MHz) and intelligently reduces the data within the pixelated region of the detector at rate will enhance physics performance at high luminosity and enable physics analyses that are not currently possible. Using the shape of charge clusters deposited in an array of small pixels, the physical properties of the traversing particle can be extracted with locally customized neural networks. In this first demonstration, we present a neural network that can be embedded into the on-sensor readout and filter out hits from low momentum tracks, reducing the detector’s data volume by 57.1%–75.7%. The network is designed and simulated as a custom readout integrated circuit with 28 nm CMOS technology and is expected to operate at less than 300 $\mu W$ with an area of less than 0.2 mm ^2 . The temporal development of charge clusters is investigated to demonstrate possible future performance gains, and there is also a discussion of future algorithmic and technological improvements that could enhance efficiency, data reduction, and power per area.

Lepton flavor universality exists in the Standard Model, and hence any observation of the violation of this universality will be a hint for new physics. Recent experimental searches for processes violating this symmetry have attracted much attention among theorists and experimentalists alike. In recent years, such hints have been observed in flavor changing neutral current weak processes such as b→sll and charged current weak processes such as b→clν processes by collider experiments like Belle, Belle II, BaBar, LHCb, ATLAS, and CMS collaborations, where b,s,c are the bottom, strange, and charm quarks, respectively, and l,ν stand for lepton and the corresponding lepton neutrino, respectively. This article is a review of some of the interesting anomalies observed in the B-sector and includes decays of Bs mesons.

The small collision systems like p+p and p+A collisions have shown new features like A+A collisions in the relativistic regime. These new aspects in small systems which have altered our research and understanding on the two-particle correlation measurements have been provided. Additionally, a critical observation of the fluctuation measurements provides new ways to infer such novel happening in the small collision systems. The ongoing and future endeavors towards the new measurements are also discussed. [ABSTRACT FROM AUTHOR]

We lay out a comprehensive physics case for a future high-energy muon collider, exploring a range of collision energies (from 1 to 100 TeV) and luminosities. We highlight the advantages of such a collider over proposed alternatives. We show how one can leverage both the point-like nature of the muons themselves as well as the cloud of electroweak radiation that surrounds the beam to blur the dichotomy between energy and precision in the search for new physics. The physics case is buttressed by a range of studies with applications to electroweak symmetry breaking, dark matter, and the naturalness of the weak scale. Furthermore, we make sharp connections with complementary experiments that are probing new physics effects using electric dipole moments, flavor violation, and gravitational waves. An extensive appendix provides cross section predictions as a function of the center-of-mass energy for many canonical simplified models. [ABSTRACT FROM AUTHOR]

For over half a century, high-energy particle accelerators have been a major enabling technology for particle and nuclear physics research as well as sources of X-rays for photon science research in material science, chemistry and biology. Particle accelerators for energy and intensity Frontier research in particle and nuclear physics continuously push the accelerator community to invent ways to increase the energy and improve the performance of accelerators, reduce their cost, and make them more power efficient. The accelerator community has demonstrated imagination and creativity in developing a plethora of future accelerator ideas and proposals. The technical maturity of the proposed facilities ranges from shovel-ready to those that are still largely conceptual. At this time, over 100 contributed papers have been submitted to the Accelerator Frontier of the US particle physics decadal community planning exercise known as Snowmass’2021. These papers cover a broad spectrum of topics: beam physics and accelerator education, accelerators for neutrinos, colliders for Electroweak/Higgs studies and multi-TeV energies, accelerators for Physics Beyond Colliders and rare processes, advanced accelerator concepts, and accelerator technology for Radio Frequency cavities (RF), magnets, targets and sources. This paper provides an overview of the present state of accelerators for particle physics and gives a brief description of some of the major facilities that have been proposed, their perceived advantages and some of the remaining challenges.

Insight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented.

In this report we summarize the many dark matter searches currently being pursued through four complementary approaches: direct detection, indirect detection, collider experiments, and astrophysical probes. The essential features of broad classes of experiments are described, each with their own strengths and weaknesses. The complementarity of the different dark matter searches is discussed qualitatively and illustrated quantitatively in two simple theoretical frameworks. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program drawing from all four approaches.

The existence of the Higgs boson was postulated more than 50 years ago, without any indication of its mass. The quest that followed, with several generations of particle physics experiments, culminated with the recent discovery of a new particle with a mass of 125 GeV. At least another half-century will be needed to map the properties of this particle with sufficient precision to understand its deepest origin.

In this report we summarize the many dark matter searches currently being pursued through four complementary approaches: direct detection, indirect detection, collider experiments, and astrophysical probes. The essential features of broad classes of experiments are described, each with their own strengths and weaknesses. The complementarity of the different dark matter searches is discussed qualitatively and illustrated quantitatively in two simple theoretical frameworks. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program drawing from all four approaches.

A strongly coupled Quark–Gluon Plasma (sQGP) is created in the high-energy heavy-ion collisions at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC). Our present understanding of sQGP as a very good liquid with astonishingly low viscosity is reviewed. With the arrival of the interesting results from LHC in high-energy p + p and p + A , a new endeavor to characterize the transition from these small systems to heavy ions (A + A) is now in place, since even the small systems showed prominent similarities to heavy ions in the rising multiplicity domains. An outlook of future possibilities for better measurements is also made at the end of this brief review. [ABSTRACT FROM AUTHOR]

Covariate adjustment is integral to the validity of observational studies assessing causal effects. It is common practice to adjust for as many variables as possible in observational studies in the hopes of reducing confounding by other variables. However, indiscriminate adjustment for variables using standard regression models may actually lead to biased estimates. In this paper, we differentiate between confounders, mediators, colliders, and effect modifiers. We will discuss that while confounders should be adjusted for in the analysis, one should be wary of adjusting for colliders. Mediators should not be adjusted for when examining the total effect of an exposure on an outcome. Automated statistical programs should not be used to decide which variables to include in causal models. Using a case scenario in cardiology, we will demonstrate how to identify confounders, colliders, mediators and effect modifiers and the implications of adjustment or non-adjustment for each of them. [ABSTRACT FROM AUTHOR]

Causal directed acyclic graphs (cDAGs) have become popular tools for researchers to better examine biases related to causal questions. DAGs comprise a series of arrows connecting nodes that represent variables and in doing so can demonstrate the causal relation between different variables. cDAGs can provide researchers with a blueprint of the exposure and outcome relation and the other variables that play a role in that causal question. cDAGs can be helpful in the design and interpretation of observational studies in pulmonary, critical care, sleep, and cardiovascular medicine. They can also help clinicians and researchers to better identify the structure of different biases that can affect the validity of observational studies. Most of the available literature on cDAGs and their function use language that might be unfamiliar to clinicians. This article explains cDAG terminology and the principles behind how they work. We use cDAGs and clinical examples that are mostly focused in the area of pulmonary medicine to describe the structure of confounding, selection bias, overadjustment bias, and detection bias. These principles are then applied to a more complex published case study on the use of statins and COPD mortality. We also introduce readers to other resources for a more in-depth discussion of causal inference principles. [ABSTRACT FROM AUTHOR]

The Glashow resonance is a rapid enhancement of the cross-section for scattering of electron antineutrinos on electrons at the W − boson production threshold due to the s -channel contribution. This resonance is being searched for at large volume neutrino detectors in which the reaction ν ̄ e e − → W − to be initiated by cosmic ray antineutrinos of energies about 6.3 PeV. The relatively small neutrino flux reaching the Earth together with the necessity of analyzing ultra-high-energy final states make such searches challenging. We argue here that the Glashow resonance may contribute to the process e + e − → W + W − . By extending the method of the effective (equivalent) particles to the neutral leptons, we relate the distribution of the effective neutrinos in the electron to the total cross-section for e + e − → W + W − . Our approach gives a good fit to the existing experimental data measured at the collider LEP at CERN and allows one to interpret these measurements as an observation of the Glashow resonance. We also discuss an advantage of future electron–positron colliders for probing the resonance. [ABSTRACT FROM AUTHOR]

Crystals were used at Fermilab accelerators for slow extraction and halo collimation in the Tevatron collider, and for channeling radiation generation experiments at the FAST electron linac facility. Here we overview past experience and major outcomes of these studies and discuss opportunities for new crystal acceleration R&D program. [ABSTRACT FROM AUTHOR]

The future of the world-wide HEP community critically depends on the feasibility of the concepts for the post-LHC Higgs factories and energy frontier future colliders. Here we overview the accelerator options based on traditional technologies and consider the need for plasma colliders, particularly, muon crystal circular colliders. We briefly address the ultimate energy reach of such accelerators, their advantages, disadvantages and limits in the view of perspectives for the far future of the accelerator-based particle physics and outline possible directions of R&D to address the most critical issues. [ABSTRACT FROM AUTHOR]

Grand Unified Theories (GUTs) are one of the most interesting high-energy completions of the Standard Model, because they provide a rich, powerful and elegant group-theoretical framework able to resolve a variety of problems remaining in our current understanding of particle physics. They usually act as motivators for many low energy BSM theories, such as left-right symmetric or supersymmetric models, and they serve to fill the gap between the experimentally reachable low energies and the physics in the ultraviolet. In recent years, however, they have fallen slightly from the spotlight, in favor of “simplified” models with more specific phenomenological predictions. The aim of this review is to summarize the state of the art on GUTs and argue for their importance in modern physics. Recent advances in experiments permit to test the predictions of GUTs at different energy scales. First, as GUTs can play a role in the inflationary dynamics of the early Universe, their imprints could be found in the CMB observations by the Planck satellite. Remarkably enough, GUTs could manifest themselves also in terrestrial tests; several planned experiments aim to probe the proton stability and to establish order of magnitude higher bounds on its lifetime. Moreover, the predictions of specific GUT models could be tested even at the LHC thanks to its high energy reach, via searches for exotic states or additional contributions to flavor anomalies.

The top-quark mass is a parameter of paramount importance in particle physics, playing a crucial role in the electroweak precision tests and in the stability of the Standard Model vacuum. I will discuss the main strategies to extract the top-quark mass at the LHC and the interpretation of the measurements in terms of well-posed top-mass definitions, taking particular care about renormalon ambiguities, progress in Monte Carlo event generators for top physics and theoretical uncertainties.

A linear electron-positron collider operating at TeV-scale energies will provide high precision measurements and allow, for example, precision studies of the Higgs boson as well as searches for physics beyond the standard model. A future linear collider should produce collisions at high energy, with high luminosity and with a good wall plug to beam power transfer efficiency. The luminosity per power consumed is a key metric that can be used to compare linear collider concepts. The plasma wakefield accelerator has demonstrated high-gradient, highefficiency acceleration of an electron beam and is therefore a promising technology for a future linear collider. We will go through the opportunities of using plasma wakefield acceleration technology for a collider, as well as a few of the collider-specific challenges that must be addressed in order for a highenergy, high luminosity-per-power plasma wakefield collider to become a reality. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'. [ABSTRACT FROM AUTHOR]

Abstract Background Child maltreatment research involves modeling complex relationships between multiple interrelated variables. Directed acyclic graphs (DAGs) are one tool child maltreatment researchers can use to think through relationships among the variables operative in a causal research question and to make decisions about the optimal analytic strategy to minimize potential sources of bias. Objective The purpose of this paper is to highlight the utility of DAGs for child maltreatment research and to provide a practical resource to facilitate and support the use of DAGs in child maltreatment research. Results We first provide an overview of DAG terminology and concepts relevant to child maltreatment research. We describe DAG construction and define specific types of variables within the context of DAGs including confounders, mediators, and colliders, detailing the manner in which each type of variable can be used to inform study design and analysis. We then describe four specific scenarios in which DAGs may yield valuable insights for child maltreatment research: (1) identifying covariates to include in multivariable models to adjust for confounding; (2) identifying unintended effects of adjusting for a mediator; (3) identifying unintended effects of adjusting for multiple types of maltreatment; and (4) identifying potential selection bias in data specific to children involved in the child welfare system. Conclusions Overall, DAGs have the potential to help strengthen and advance the child maltreatment research and practice agenda by increasing transparency about assumptions, illuminating potential sources of bias, and enhancing the interpretability of results for translation to evidence-based practice. [ABSTRACT FROM AUTHOR]

Mendelian randomization (MR) has been used to estimate the causal effect of body mass index (BMI) on particular traits thought to be affected by BMI. However, BMI may also be a modifiable, causal risk factor for outcomes where there is no prior reason to suggest that a causal effect exists. We performed a MR phenome-wide association study (MR-pheWAS) to search for the causal effects of BMI in UK Biobank (n = 334 968), using the PHESANT open-source phenome scan tool. A subset of identified associations were followed up with a formal two-stage instrumental variable analysis in UK Biobank, to estimate the causal effect of BMI on these phenotypes. Of the 22 922 tests performed, our MR-pheWAS identified 587 associations below a stringent P value threshold corresponding to a 5% estimated false discovery rate. These included many previously identified causal effects, for instance, an adverse effect of higher BMI on risk of diabetes and hypertension. We also identified several novel effects, including protective effects of higher BMI on a set of psychosocial traits, identified initially in our preliminary MR-pheWAS in circa 115,000 UK Biobank participants and replicated in a different subset of circa 223,000 UK Biobank participants. Our comprehensive MR-pheWAS identified potential causal effects of BMI on a large and diverse set of phenotypes. This included both previously identified causal effects, and novel effects such as a protective effect of higher BMI on feelings of nervousness. [ABSTRACT FROM AUTHOR]

Cuprate superconductors entered into operation at the CERN LHC, the largest particle accelerator, in 2008, as part of the current leads system, a mere 20 years after the discovery by A. Mueller and G. Bednorz. The utilization of HTS for accelerator magnets faces exceptionally demanding, as yet unresolved, challenges. However, the forthcoming generation of accelerators, necessitating high magnetic field strengths (above 15 T) and emphasizing sustainability by reducing energy consumption, presents a distinct opportunity for cuprate superconductors to emerge as the fundamental framework for all future large accelerators in high-energy physics. [ABSTRACT FROM AUTHOR]

Colliders, among the most successful tools of particle physics, have revealed much about matter. This review describes how colliders contribute to the search for particle dark matter, focusing on the highest-energy collider currently in operation, the Large Hadron Collider (LHC) at CERN. In the absence of hints about the character of interactions between dark matter and standard matter, this review emphasizes what could be observed in the near future, presents the main experimental challenges, and discusses how collider searches fit into the broader field of dark matter searches. Finally, it highlights a few areas to watch for the future LHC program. [ABSTRACT FROM AUTHOR]

Knowing brain connectivity is of great importance both in basic research and for clinical applications. We are proposing a method to infer directed connectivity from zero-lag covariances of neuronal activity recorded at multiple sites. This allows us to identify causal relations that are reflected in neuronal population activity. To derive our strategy, we assume a generic linear model of interacting continuous variables, the components of which represent the activity of local neuronal populations. The suggested method for inferring connectivity from recorded signals exploits the fact that the covariance matrix derived from the observed activity contains information about the existence, the direction and the sign of connections. Assuming a sparsely coupled network, we disambiguate the underlying causal structure via L1-minimization, which is known to prefer sparse solutions. In general, this method is suited to infer effective connectivity from resting state data of various types. We show that our method is applicable over a broad range of structural parameters regarding network size and connection probability of the network. We also explored parameters affecting its activity dynamics, like the eigenvalue spectrum. Also, based on the simulation of suitable Ornstein-Uhlenbeck processes to model BOLD dynamics, we show that with our method it is possible to estimate directed connectivity from zero-lag covariances derived from such signals. In this study, we consider measurement noise and unobserved nodes as additional confounding factors. Furthermore, we investigate the amount of data required for a reliable estimate. Additionally, we apply the proposed method on full-brain resting-state fast fMRI datasets. The resulting network exhibits a tendency for close-by areas being connected as well as inter-hemispheric connections between corresponding areas. In addition, we found that a surprisingly large fraction of more than one third of all identified connections were of inhibitory nature. [ABSTRACT FROM AUTHOR]

In this paper we will give an introduction to the Circular Electron Positron Collider (CEPC). The scientific background, physics goal, the collider design requirements and the conceptual design principle of the CEPC are described. On the CEPC accelerator, the optimization of parameter designs for the CEPC with different energies, machine lengths, single ring and crab-waist collision partial double ring, advanced partial double ring and fully partial double ring options, etc. have been discussed systematically, and compared. The CEPC accelerator baseline and alternative designs have been proposed based on the luminosity potential in relation with the design goals. The CEPC sub-systems, such as the collider main ring, booster, electron positron injector, etc. have also been introduced. The detector and the MAchine-Detector Interface (MDI) design have been briefly mentioned. Finally, the optimization design of the Super Proton-Proton Collider (SppC), its energy and luminosity potentials, in the same tunnel of the CEPC are also discussed. The CEPC-SppC Progress Report (2015-2016) has been published. [ABSTRACT FROM AUTHOR]