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  1. Collider searches for long-lived particles beyond the Standard Model

    Lee, Lawrence ; Ohm, Christian ; Soffer, Abner ; ... - Progress in Particle and Nuclear Physics
    Despite decades of attempts to reveal its flaws, the Standard Model of particle physics (SM) has withstood all experimental tests and its predictions are in excellent agreement with data. Since the theory was formulated, experiments have provided little guidance regarding the explanations of phenomena not described by the SM, such as the baryon asymmetry of the universe and dark matter. Nor do we have satisfying understanding of the aesthetic and theoretical problems of the model, despite years of searching for new processes and particles proposed to solve them. Such particles can evade being discovered by the comprehensive search programs atmore » collider experiments if the analysis selections and the algorithms used to reconstruct the detector data are not matched to the characteristics of the particles, e.g. if they have long enough lifetimes. As interest in searches for such long-lived particles at colliders grows rapidly, we present a review of this area of research in this article. The broad range of theoretical motivations for particles with long lifetimes and the experimental strategies and methods employed to search for them are described. Results from decades of searches are reviewed, as are opportunities for the next generation of searches both at existing and proposed future experiments.« less

  2. Adiabatic plasma lens experiments at SPARC

    Rosenzweig, J. B. ; Filippi, F. ; Zigler, A. ; ... - Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

  3. Front End for a neutrino factory or muon collider

    Neuffer, David ; Snopok, Pavel ; Alexahin, Yuri - Journal of Instrumentation
    A neutrino factory or muon collider requires the capture and cooling of a large number of muons. Scenarios for capture, bunching, phase-energy rotation and initial cooling of μ’s produced from a proton source target have been developed, initially for neutrino factory scenarios. They require a drift section from the target, a bunching section and a Φ-δE rotation section leading into the cooling channel. Important concerns are rf limitations within the focusing magnetic fields and large losses in the transport. The currently preferred cooling channel design is an “HFOFO Snake” configuration that cools both μ+ and μ- transversely and longitudinally. Finally,more » the status of the design is presented and variations are discussed.« less

  4. Higher-twist corrections to gluon TMD factorization

    Balitsky, I. ; Tarasov, A. - Journal of High Energy Physics (Online)
    Here, we calculate power corrections to TMD factorization for particle production by gluon-gluon fusion and in hadron-hadron collisions.

  5. Probing the Higgs with angular observables at future e+e– colliders

    Liu, Zhen - International Journal of Modern Physics A
    In this paper, 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– → ZHℓ+ℓ–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 √s = 240 GeV and 5 (30) ab–1 integrated luminosity. We then determine the projected sensitivity to a rangemore » 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. Finally, we also discuss the possibility of using ZZ-fusion at e+e– machines at different energies to probe new operators.« less

  6. Development of a 15 T Nb3Sn accelerator dipole demonstrator at Fermilab

    Novitski, I. ; Andreev, N. ; Barzi, E. ; ... - IEEE Transactions on Applied Superconductivity
    Here, a 100 TeV scale Hadron Collider (HC) with a nominal operation field of at least 15 T is being considered for the post-LHC era, which requires using the Nb3Sn technology. Practical demonstration of this field level in an accelerator-quality magnet and substantial reduction of the magnet costs are the key conditions for realization of such a machine. FNAL has started the development of a 15 T Nb3Sn dipole demonstrator for a 100 TeV scale HC. The magnet design is based on 4-layer shell type coils, graded between the inner and outer layers to maximize the performance and reduce themore » cost. The experience gained during the Nb3Sn magnet R&D is applied to different aspects of the magnet design. This paper describes the magnetic and structural designs and parameters of the 15 T Nb3Sn dipole and the steps towards the demonstration model fabrication.« less

  7. Single electron yields from semileptonic charm and bottom hadron decays in Au+Au collisions at s N N = 200 GeV

    Adare, A. ; Aidala, C. ; Ajitanand, N. N. ; ... - Physical Review C
    We measured open heavy flavor production in minimum bias Au + Au collisions at √s(NN) = 200 GeV via the yields of electrons from semileptonic decays of charm and bottom hadrons, using the PHENIX Collaboration at the Relativistic Heavy Ion Collider. In the past, heavy flavor electron measurements indicated substantial modification in the momentum distribution of the parent heavy quarks owing to the quark-gluon plasma created in these collisions. For the first time, using the PHENIX silicon vertex detector to measure precision displaced tracking, the relative contributions from charm and bottom hadrons to these electrons as a function of transversemore » momentum are measured in Au + Au collisions. Here, we compare the fraction of electrons from bottom hadrons to previously published results extracted from electron-hadron correlations in p + p collisions at √s(NN) = 200 GeV and find the fractions to be similar within the large uncertainties on both measurements for p(T) > 4 GeV/c. We use the bottom electron fractions in Au + Au and p + p along with the previously measured heavy flavor electron R(AA) to calculate the R(AA) for electrons from charm and bottom hadron decays separately. Finally, we find that electrons from bottom hadron decays are less suppressed than those from charm for the region 3 < p(T) < 4 GeV/c.« less

  8. Probing triple-Higgs productions via 4 b 2 γ decay channel at a 100 TeV hadron collider

    Chen, Chien-Yi ; Yan, Qi-Shu ; Zhao, Xiaoran ; ... - Physical Review D
    We report that the quartic self-coupling of the Standard Model Higgs boson can only be measured by observing the triple-Higgs production process, but it is challenging for the LHC Run 2 or International Linear Collider (ILC) at a few TeV because of its extremely small production rate. In this paper, we present a detailed Monte Carlo simulation study of the triple-Higgs production through gluon fusion at a 100 TeV hadron collider and explore the feasibility of observing this production mode. We focus on the decay channel HHH →$$b\bar{b}$$$$b\bar{b}$$γγ, investigating detector effects and optimizing the kinematic cuts to discriminate the signalmore » from the backgrounds. Our study shows that, in order to observe the Standard Model triple-Higgs signal, the integrated luminosity of a 100 TeV hadron collider should be greater than 1.8×104 ab₋1. We also explore the dependence of the cross section upon the trilinear (λ3) and quartic (λ4) self-couplings of the Higgs. Ultimately, we find that, through a search in the triple-Higgs production, the parameters λ3 and λ4 can be restricted to the ranges [₋1,5] and [₋20,30], respectively. We also examine how new physics can change the production rate of triple-Higgs events. For example, in the singlet extension of the Standard Model, we find that the triple-Higgs production rate can be increased by a factor of O(10).« less

  9. Heavy color-octet particles at the LHC

    Chen, Chien-Yi ; Freitas, Ayres ; Han, Tao ; ... - Journal of High Energy Physics (Online)
    Many new-physics models, especially those with a color-triplet top-quark partner, contain a heavy color-octet state. The “naturalness” argument for a light Higgs boson requires that the color-octet state be not much heavier than a TeV, and thus it can be pair-produced with large cross sections at high-energy hadron colliders. It may decay preferentially to a top quark plus a top partner, which subsequently decays to a top quark plus a color-singlet state. This singlet can serve as a WIMP dark-matter candidate. Such decay chains lead to a spectacular signal of four top quarks plus missing energy. We pursue a generalmore » categorization of the color-octet states and their decay products according to their spin and gauge quantum numbers. Here, we review the current bounds on the new states at the LHC and study the expected discovery reach at the 8-TeV and 14-TeV runs. We also present the production rates at a future 100-TeV hadron collider, where the cross sections will be many orders of magnitude greater than at the 14-TeV LHC. Furthermore, we explore the extent to which one can determine the color octet’s mass, spin, and chiral couplings. Finally, we propose a test to determine whether the fermionic color octet is a Majorana particle.« less

  10. Non-planar master integrals for the production of two off-shell vector bosons in collisions of massless partons

    Caola, Fabrizio ; Henn, Johannes M. ; Melnikov, Kirill ; ... - Journal of High Energy Physics (Online)
    We present the calculation of all non-planar master integrals that are needed to describe production of two off-shell vector bosons in collisions of two massless partons through NNLO in perturbative QCD. The integrals are computed analytically using differential equations in external kinematic variables and expressed in terms of Goncharov polylogarithms. These results provide the last missing ingredient needed for the computation of two-loop amplitudes that describe the production of two gauge bosons with different invariant masses in hadron collisions.
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