Narrow Results

We review recent theoretical progress in evaluating higher order QCD corrections to Higgs boson differential distributions at hadron–hadron colliders.

This review starts with a brief introduction to the charged Higgs boson (H^±) in the Minimal Supersymmetric Standard Model (MSSM). It then discusses the prospects of a relatively light H^± boson search via top quark decay at Tevatron/LHC, and finally a heavy H^± boson search at LHC. The viable channels for H^± search are identified in both the cases, with particular emphasis on the H^±→τν decay channel. The effects of NLO QCD correction in the SM as well as the MSSM are discussed briefly.

The CMD-3 detector has been taking data since December 2010 at the VEPP-2000 electron–positron collider. The collected data sample corresponds to about 60 inverse picobarn of integrated luminosity in the c.m. energy range from 0.32 GeV to 2.0 GeV. Preliminary results of the analysis of various hadronic cross-sections, in particular, $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$, ${\pi }^{+}{\pi }^{-}{\pi }^0$, $K_L{K}_S$, $K^{+}{K}^{-}$, $\eta \gamma$, 3$({\pi }^{+}{\pi }^{-})$, $2({\pi }^{+}{\pi }^{-}{\pi }^0)$, $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$, $K^{+}{K}^{-}\eta$, $K^{+}{K}^{-}{\pi }^0$, $\eta {\pi }^{+}{\pi }^{-}$, $\omega {\pi }^{+}{\pi }^{-}$ and $\omega \to {\pi }^0{e}^{+}{e}^{-}$ are presented. The processes with multi-hadron final states have several intermediate states which have to be taken into account to correctly describe the angular and invariant mass distributions, as well as cross-section energy dependence.

The Super Tau-Charm Facility (STCF) is a proposed dual-ring electron–positron collider in China, designed to operate at a center-of-mass energy (CME) range of 2–7GeV with symmetric beam energies. The collider aims for a luminosity exceeding $5\times 10^{34}{\mathrm{\text{cm}}}^{-2}{\mathrm{\text{s}}}^{-1}$ at the beam energy of 2.0GeV. This work presents the preliminary lattice design for the STCF collider ring, specifically optimized for the 2.0GeV beam energy. To improve the nonlinear dynamics performance, the optimization of lattice is carried out by adjusting the strengths of sextupole and octupole magnets following the tuning of phase advances.

In this paper, a nondestructive cavity-based scheme is proposed to achieve high-resolution bunch length measurement in the Super Tau-Charm Facility (STCF) transport line. By extracting the TM010 and TM020 mode signals excited by the beam within a single pillbox cavity, a beam spectrum can be obtained to deduce the Root-Mean-Square (RMS) bunch length. This scheme is more spatially compact compared to the traditional method using double cavities. In this study, the basic principles of the cavity-based bunch length measurement method are explained, the monitor layout is introduced, and the design methods for the cavity and electronics are described. A prototype cavity was machined. Offline tests demonstrate that the eigenmodes in the cavity meet the design requirements and can be used for the bunch length measurements. Based on the online signal characteristics of the Cavity Beam Position Monitors (CBPMs) and the beam parameters of the STCF, the performance of this measurement method is evaluated. For picosecond-level bunches in the STCF transport line, this scheme can provide a bunch length measurement resolution of 233.5 fs at 1.5 nC.

This contributions summarizes some of the developments in tests and measurements of the electroweak sector of the standard model. Recent experimental results and their implications are emphasized.

I summarize our recent works on using differential observables to explore the physics potential of future $e^{+}{e}^{-}$ colliders in the framework of Higgs effective field theory. This proceeding is based upon Refs. 1 and 2. We study angular observables in the $e^{+}{e}^{-}\to ZH{\ell }^{+}{\ell }^{-}b\bar{b}$ channel at future circular $e^{+}{e}^{-}$ colliders such as CEPC and FCC-ee. Taking into account the impact of realistic cut acceptance and detector effects, we forecast the precision of six angular asymmetries at CEPC (FCC-ee) with center-of-mass energy $\sqrt{s}=240$ GeV and 5 (30) ab${}^{-1}$ integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for the Higgsstrahlung process in the dimension-6 Higgs EFT. Our results show that angular observables provide complementary sensitivity to rate measurements when constraining various tensor structures arising from new physics. We further find that angular asymmetries provide a novel means of constraining the “blind spot” in indirect limits on supersymmetric scalar top partners. We also discuss the possibility of using $ZZ$-fusion at $e^{+}{e}^{-}$ machines at different energies to probe new operators.

Advancements in fast timing particle detectors have opened up new possibilities to design $4\pi$ collider detectors that fully reconstruct and separate event vertices and individual particles in the time domain. The applications of these techniques are considered for the physics at CEPC.

The many ways in which machine and deep learning are transforming the analysis and simulation of data in particle physics are reviewed. The main methods based on boosted decision trees and various types of neural networks are introduced, and cutting-edge applications in the experimental and theoretical/phenomenological domains are highlighted. After describing the challenges in the application of these novel analysis techniques, the review concludes by discussing the interactions between physics and machine learning as a two-way street enriching both disciplines and helping to meet the present and future challenges of data-intensive science at the energy and intensity frontiers.

The possibility to obtain the transversely polarized electron/positron beams at the $2\times 45$ GeV CEPC collider basing on the radiative self-polarization of particles in the main rings is under consideration. In addition, we consider one of the options for obtaining longitudinal polarization of electrons at CEPC.

Perturbative and nonperturbative terms of the cross-sections of ultraperipheral production of lepton pairs in ion collisions are taken into account. It is shown that production of low-mass $e^{+}{e}^{-}$ pairs is strongly enhanced (compared to perturbative estimates) due to the nonperturbative Sommerfeld–Gamow–Sakharov (SGS) factor. Coulomb attraction of the nonrelativistic components of those pairs leads to the finite value of their mass distribution at lowest masses. Their annihilation can result in an increased intensity of 511 keV photons. It can be recorded at the NICA collider and is especially crucial in astrophysical implications regarding the 511 keV line emitted from the Galactic center. The analogous effect can be observed in lepton pairs production at LHC. Energy spectra of lepton pairs created in ultraperipheral nuclear collisions and their transverse momenta are calculated.

The tetrad representation theorem, due to Spirtes, Glymour, and Scheines (1993), gives a graphical condition necessary and sufficient for the vanishing of an individual tetrad difference in a recursive path model with uncorrelated errors. In this paper, we generalize their result from individual tetrad differences to sets of tetrad differences of a certain form, and we simplify their proof. The generalization allows tighter constraints to be placed on the set of models compatible with given data and thereby facilitates the search for parsimonious models for large data sets.

This article describes the beginnings of the Superconducting Super Collider (SSC). The narrative starts in the early 1980s with the discussion of the process that led to the recommendation by the US high energy physics community to initiate work on a multi-TeV hadron collider. The article then describes the formation in 1984 of the Central Design Group (CDG) charged with directing and coordinating the SSC R&D and subsequent activities which led in early 1987 to the SSC endorsement by President Reagan. The last part of the article deals with the site selection process, steps leading to the initial Congressional appropriation of the SSC construction funds and the creation of the management structure for the SSC Laboratory.

We review the basic methods for cooling charged particle beams in storage rings and accelerators. Applications of cooled beams are discussed.

It is generally accepted that the birth of the Large Hadron Collider (LHC) was in the Lausanne Workshop in 1984 [1], where machine builders and experimentalists first got together to discuss the next big project for CERN. In reality, the seeds were sown much earlier, with the construction of the Intersecting Storage Rings at CERN, followed by the proton–antiproton colliders at CERN and at Fermilab. In this article I try to give a historical perspective on how the LHC came to be, as well as my own account of some of the political, technical and financial challenges that had to be met in order to make it a reality.

The application of superconductivity to the large magnets required for charged particle spectroscopy in high energy physics experiments, and for plasma containment in fusion experiments, has resulted in a spectacular leap in the efficiency of these devices. First applied in the late 1960s, the technology has progressed to meet increasingly demanding goals of the experiments and has stimulated important development of the associated conductors. In this article we describe briefly the basic requirements that determine the design of the different types of magnets. This is followed by descriptions of examples of representative working and projected magnets, as well as essential auxiliary equipment. An overview is provided of ongoing development that may impact on the design of future magnets.

After an introduction, the projected performances are presented for muon colliders with a range of energies from 126 GeV (the Higgs mass) to 6 TeV. Estimates of potential wall power consumption are also given. It is noted that a merit factor, the number of simultaneously operated detectors times the luminosity divided by the power consumption, rises rapidly above 1.5 TeV. At 6 TeV it is projected to be almost two orders of magnitude higher than that for an e⁺e^- linear collider. The reason for this is discussed. The physics potential of these machines is then outlined, including the 126 GeV collider's unique ability to measure the Higgs width, and the potential for a high energy machine's study of any structure seen in a hadron collider. The design and simulations of the different components are then reviewed, followed by a discussion of the supporting experiments and technology R&D.

Particle acceleration in plasma creates a possibility of exceptionally high accelerating gradients and appears to be a very attractive option for future linear electron–positron and/or $\gamma$–$\gamma$ colliders. These high accelerating gradients have already been demonstrated in a number of experiments. However, a linear collider requires exceptionally high beam brightness which still needs to be demonstrated. In this article we discuss major phenomena which limit the beam brightness of accelerated beam and, consequently, the collider luminosity.

As the special machines that can accelerate charged particle beams to high energy by using electromagnetic fields, particle accelerators have been widely applied in scientific research and various areas of society. The development of particle accelerators in China started in the early 1950s. After a brief review of the history of accelerators, this article describes in the following sections: particle colliders, heavy-ion accelerators, high-intensity proton accelerators, accelerator-based light sources, pulsed power accelerators, small scale accelerators, accelerators for applications, accelerator technology development and advanced accelerator concepts. The prospects of particle accelerators in China are also presented.

The potential of muon beams for high energy physics applications is described along with the challenges of producing high quality muon beams. Two proposed approaches for delivering high intensity muon beams, a proton driver source and a positron driver source, are described and compared. The proton driver concepts are based on the studies from the Muon Accelerator Program (MAP). The MAP effort focused on a path to deliver muon-based facilities, ranging from neutrino factories to muon colliders, that could span research needs at both the intensity and energy frontiers. The Low EMittance Muon Accelerator (LEMMA) concept, which uses a positron-driven source, provides an attractive path to very high energy lepton colliders with improved particle backgrounds. The recent study of a 14-TeV muon collider in the LHC tunnel, which could leverage the existing CERN injectors and infrastructure and provide physics reach comparable to the 100TeV FCC-hh, at lower cost and with cleaner physics conditions, is also discussed. The present status of the design and R&D efforts towards each of these sources is described. A summary of important R&D required to establish a facility path for each concept is also presented.