Search

Following HERA, the LHeC represents a new ep/eA collider of much increased luminosity and energies. Using the LHC, with Ep between 1 and 7TeV, complemented by an electron ring or linac, with Ee possibly up to 140 GeV, a new range of DIS opens up and precise investigations of the proton structure and new phenomena at TeV energies become possible. A brief summary is given on machine and physics considerations as were presented at DIS08, towards a Conceptual Design Report by the end of 2009.

The precise determination of the luminosity in a collider is of crucial importance for any physics cross sections measurement since it directly translates to the precision of the cross section determination. In a muon collider high intensity beams are necessary to achieve the target luminosity, and due to the muon decay they generate very high fluxes of particles that arrive to the detector. Ad-hoc shielding structure has been designed to mitigate the effect of the beam-induced background on the detector located in the backward and forward regions. Therefore, the instrumentation for the measurement of the luminosity can not be placed, as in the LHC experiments, in these regions. In this paper an alternative way to determine such a fundamental parameter is proposed, taking inspiration from flavour factories such as Belle2 and BESIII, where the luminosity is measured by counting $e^+$ $e^-$ $\rightarrow$ $e^+$ $e^-$ Bhabha events, whose cross section is theoretically known with high precision. At muon collider the large angle muon Bhabha ($\mu^+$ $\mu^-$ $\rightarrow$ $\mu^+$ $\mu^-$) events are used, and here the first results on the precision obtained at 1.5 TeV center of mass energy by using full detector simulation, taking into account the beam-induced background effects, are presented.

The first mention of the impedance concept appeared on November 1966 in the CERN internal report "Longitudinal instability of a coasting beam above transition, due to the action of lumped discontinuities" by V.G. Vaccaro. This was the beginning of many studies, which took place over the last five decades, and today, impedances and wake fields continue to be an important field of activity, as concerns theory, simulation, bench and beam-based measurements. Building a reliable impedance or wake field model of a machine is the first necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider), etc. Beam collective instabilities, and their mitigation, cover a wide range of effects in particle accelerators and they have been the subjects of intense research. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. With the increasing power of our computers this becomes easier but the need to continue and develop theories remains, to have a better understanding of the interplays between all these effects: the subject of impedance and beam instabilities in particle accelerators is far from being exhausted, as testified by the many new instability and stabilizing mechanisms which have been recently explained or discovered. Furthermore, in the context of the studies for possible future accelerators, some uncharted territories remain such as, for instance, the collective instabilities during the necessary ionization cooling for a muon collider., 24 pages, 23 figures, to be published in JINST (special Issue: ICFA Beam Dynamics Newsletter No. 82)

We present cross-section expectations for various processes and collider options, for benchmark scenarios of the Inert Doublet Model, a Two Higgs Doublet Model with a dark matter candidate. The proposed scenarios are consistent with current dark matter constraints, including the most recent bounds from the XENON1T experiment and relic density, as well as with known collider and low-energy limits. These benchmarks, chosen in earlier work for studies at $e^+e^-$ colliders, exhibit a variety of kinematic features that should be explored at current and future runs of the LHC. We provide cross sections for all relevant production processes at 13 TeV, 27 TeV and 100 TeV proton collider, as well as for a possible 10 TeV and 30 TeV muon collider., 44 pages, 11 figures; v2: corresponds to published journal version (slight style differences)

We study the complementarity of the proposed multi-TeV muon colliders and the near-future gravitational wave (GW) detectors to the first order electroweak phase transition (FOEWPT), taking the real scalar extended Standard Model as the representative model. A detailed collider simulation shows the FOEWPT parameter space can be greatly probed via the the vector boson fusion production of the singlet, and its subsequent decay to the di-Higgs or di-boson channels. Especially, almost all the parameter space yielding detectable GW signals can be probed by the muon colliders. Therefore, if we could detect stochastic GWs in the future, a muon collider could provide a hopeful crosscheck to identify their origin. On the other hand, there is considerable parameter space that escapes GW detections but is within the reach of the muon colliders. The precision measurements of Higgs couplings could also probe the FOEWPT parameter space efficiently., 15 pages + references, 5 figures. Accepted by JHEP

A high energy muon collider can provide new and complementary discovery potential to the LHC or future hadron colliders. Leptoquarks are a motivated class of exotic new physics models, with distinct production channels at hadron and lepton machines. We study a vector leptoquark model at a muon collider with $\sqrt{s} = 3, 14$ TeV within a set of both UV and phenomenologically motivated flavor scenarios. We compute which production mechanism has the greatest reach for various values of the leptoquark mass and the coupling between leptoquark and Standard Model fermions. We find that we can probe leptoquark masses up to an order of magnitude beyond $\sqrt{s}$ with perturbative couplings. Additionally, we can also probe regions of parameter space unavailable to flavor experiments. In particular, all of the parameter space of interest to explain recent low-energy anomalies in B meson decays would be covered even by a $\sqrt{s} = 3$ TeV collider., Comment: 21+11 pages, 16 figures

An electron-muon collider with an asymmetric collision profile targeting multi-ab$^{-1}$ integrated luminosity is proposed. This novel collider, operating at collisions energies of e.g. 20-200 GeV, 50-1000 GeV and 100-3000 GeV, would be able to probe charged lepton flavor violation and measure Higgs boson properties precisely. The collision of an electron and muon beam leads to less physics background compared with either an electron-electron or a muon-muon collider, since electron-muon interactions proceed mostly through higher order vector boson fusion and vector boson scattering processes. The asymmetric collision profile results in collision products that are boosted towards the electron beam side, which can be exploited to reduce beam-induced background from the muon beam to a large extent. With this in mind, one can imagine a lepton collider complex, starting from colliding order 10 GeV electron and muon beams for the first time in history and to probe charged lepton flavor violation, then to be upgraded to a collider with 50-100 GeV electron and 1-3 TeV muon beams to measure Higgs properties and search for new physics, and finally to be transformed to a TeV scale muon muon collider. The cost should vary from order 100 millions to a few billion dollars, corresponding to different stages, which make the funding situation more practical., Comment: 4 pages, 4 figures

The Muon Collider is a possible option for the next generation of high energy collider machines. It would permit to achieve the energy frontier in lepton collisions, without occurring in significant synchrotron radiation losses as in electrons rings.Among the technological challenges in the realization of such a machine, the treatment of the beam-induced background is one of the most critical issues for the detectors.Beams with intensity of the order of $10^{12}$ muons per bunch are necessary to obtain the desired luminosity, therefore the muons decay rate is very high. Beam decay products and subsequent particles from secondary interactions with the machine elements can reach the interaction point, limiting the physical performance of the detector. A study of the beam-induced background is presented together with possible strategies for its reduction. Preliminary results on the reconstruction of a benchmark process, $\mu^+\mu^-\to H\nu\bar{\nu}\to b \bar{b}\nu\bar{\nu}$, including the beam-induced background are illustrated as demonstration of physics measurements feasibility in this harsh environment.

A muon collider would be both a precision and a powerful discovery machine, because it can offer collisions of point-like particles at very high energies, strongly exceeding the energy reach of other lepton colliders. It can even match the discovery of a proton collider with much higher energy, since the muon collision energy is fully available at constituent level unlike for the protons. However, the need for high luminosity faces technical challenges which arise from the short muon lifetime at rest and the difficulty of producing large numbers of muons in bunches with small emittance. Addressing these challenges requires the development of innovative concepts and demanding technologies. In view of the potential importance of muon colliders for the future of high-energy physics it is timely to start an R&D; programme now. A high-energy muon collider is receiving renewed attention as a possible frontier-exploration machine. Daniel Schulte, Nadia Pastrone and Ken Long describe the possible paths ahead.

Measuring the shape of the Higgs boson potential is of paramount importance and will be a challenging task at current as well as future colliders. While the expectations for the measurement of the trilinear Higgs self-coupling are rather promising, an accurate measurement of the quartic self-coupling interaction is presently considered extremely challenging even at a future 100 TeV proton-proton collider. In this work we explore the sensitivity that a muon collider with a center of mass energy in the multi-TeV range, and luminosities of the order of 10^35cm^-2s^-1, as presently under discussion, might provide thanks to a rather large three Higgs-boson production and to a limited background. By performing a first and simple analysis, we find a clear indication that a muon collider could provide a determination of the quartic Higgs self-coupling that is significantly better than what is currently considered attainable at other future colliders., Table 3 and figs.14-18 added. Matches version published on JHEP

High-energy lepton colliders with a centre-of-mass energy in the multi-TeV range are currently considered among the most challenging and far-reaching future accelerator projects. Studies performed so far have mostly focused on the reach for new phenomena in lepton-antilepton annihilation channels. In this work we observe that starting from collider energies of a few TeV, electroweak (EW) vector boson fusion/scattering (VBF) at lepton colliders becomes the dominant production mode for all Standard Model processes relevant to studying the EW sector. In many cases we find that this also holds for new physics. We quantify the size and the growth of VBF cross sections with collider energy for a number of SM and new physics processes. By considering luminosity scenarios achievable at a muon collider, we conclude that such a machine would effectively be a "high-luminosity weak boson collider," and subsequently offer a wide range of opportunities to precisely measure EW and Higgs coupling as well as to discover new particles., Comment: 58 pages, 17 figures, 9 tables. A contribution to Snowmass 2021

The Weakly Interacting Massive Particle (WIMP) paradigm is one of the most compelling scenarios for particle dark matter (DM). We show in this paper that a high energy muon collider can make decisive statements about the WIMP DM, and this should serve as one of its main physics driver cases. We demonstrate this by employing the DM as the lightest member of an electroweak (EW) multiplet, which is a simple, yet one of the most challenging WIMP scenarios given its minimal collider signature and high thermal target mass scale of 1 TeV$-$23 TeV. We perform a first study of the reach of high energy muon colliders, focusing on the simple, inclusive and conservative signals with large missing mass, through the mono-photon, VBF di-muon and a novel mono-muon channel. Using these inclusive signals, it is possible to cover the thermal targets of doublet and triplet with a 10 TeV muon collider. Higher energies, 14 TeV$-$75 TeV, would ensure a $5 \sigma$ reach above the thermal targets for the higher EW multiplets. We also estimate the reach of a search for disappearing tracks, demonstrating the potential significant enhancement of the sensitivity., Comment: v1: 33 pages, 16 figures, 3 tables; v2: minor updates, matches PRD published version; v3: doublet disappearing track numerical results corrected, conclusions improves; also matches PRD errata

A monitoring system for intense (up to 105 neutrons/(cm2 s)) neutron fluxes with energies as high as 15 MeV has been developed for long-term operation in strong magnetic and radiation fields of collider experiments. The system is used to monitor the radiation shielding efficiency, estimate the radiation degradation of active elements of experimental setups, and perform additional independent monitoring of the accelerator luminosity. The system has been tested and put into operation at the Compact Muon Solenoid (CMS) experimental setup of the Large Hadron Collider (LHC).

It is proposed to place the arcs of an SLC-type facility inside the tunnel of a Future Circular Collider (FCC). Accelerated by a linear accelerator (linac), electron and positron beams would traverse the bending arcs in opposite directions and collide at centre-of-mass energies considerably exceeding those attainable at circular e+e− colliders. The proposed SLC-type facility would have the same luminosity as a conventional two-linace e+e−collider. Using an optical free-electron laser, the facility could be converted into a γγ collider. A superconducting L-band linac at the proposed facility may form a part of the injector chain for a 100-TeV proton collider in the FCC tunnel. The whole accelerator complex would serve as a source of e+e−, γγ, pp and ep interactions. The L-band linac could also be used to produce high-intensity neutrino, kaon and muon beams for fixed-target experiments, as well as X-ray free-electron laser (XFEL) photons for applications in material science and medicine.

In this study, main parameters of Super proton-proton Collider (SppC) based lepton-proton colliders are estimated. For electron beam parameters, highest energy International Linear Collider (ILC) and Plasma Wake Field Accelerator-Linear Collider (PWFA-LC) options are taken into account. For muon beams, 1.5 TeV and 3 TeV center of mass energy Muon Collider parameters are used. In addition, ultimate $\mu$p collider which assumes construction of additional 50 TeV muon ring in the SppC tunnel is considered as well. It is shown that $L_{ep}$ $\sim$ $10^{32}$ $cm^{-2}s^{-1}$ can be achieved with moderate upgrade of the SppC proton beam parameters. Physics search potential of proposed lepton-proton colliders is illustrated by considering small Bjorken x region as an example of SM physics and resonant production of color octet leptons as an example of BSM physics., Comment: 11 pages, 3 figures, 8 tables

We study for the first time the collider reach on the derivative Higgs portal, the leading effective interaction that couples a pseudo Nambu-Goldstone boson (pNGB) scalar Dark Matter to the Standard Model. We focus on Dark Matter pair production through an off-shell Higgs boson, which is analyzed in the vector boson fusion channel. A variety of future high-energy lepton colliders as well as hadron colliders are considered, including CLIC, a muon collider, the High-Luminosity and High-Energy versions of the LHC, and FCC-hh. Implications on the parameter space of pNGB Dark Matter are discussed. In addition, we give improved and extended results for the collider reach on the marginal Higgs portal, under the assumption that the new scalars escape the detector, as motivated by a variety of beyond the Standard Model scenarios., 12 pages + appendices and references, 10 figures; v2: minor revisions and a few additions, including extra references; v3: new figure comparing VBF reach to parameter regions compatible with first-order EW phase transition (Figure 9), additional references. This version is more up to date than the published one

Muon Collider is a promising option for the next generation high-energy collider, possessing very low radiation losses due to synchrotron radiation. Treatment of the beam-induced background is one of the most critical issues in such a machine. Since the muon beams must be very intense to reach high luminosity, the muons decay products and subsequent particles from secondary interactions with the environment can reach the interaction point, limiting the physical performance of the detector. This talk presents a reconstruction strategy for a benchmark process, H->bb-bar, in the presence of the beam-induced background.

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 100 TeV 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., 29 pages, 17 figures

International audience; After measuring in 2012 a relatively large value of the neutrino mixing angle $\theta_{13}$, the door is now open to observe for the first time a possible CP violation in the leptonic sector.The measured value of $\theta_{13}$ privileges the 2nd oscillation maximum for the discovery of CP violation instead of the usually used 1st oscillation maximum.The sensitivity at this 2nd oscillation maximum is about three times higher than for the 1st oscillation maximum inducing a lower sensitivity to systematic errors.Going to the 2nd oscillation maximum necessitates a very intense neutrino beam with the appropriate energy.The world's most intense pulsed spallation neutron facility, the European Spallation Source, will have a proton linac with 5 MW power and 2 GeV energy.This linac, under construction, also has the potential to become the proton driver of the world's most intense neutrino beam with very high probability to discover a neutrino CP violation.The physics performance of this neutrino Super Beam in conjunction with a megaton underground Water Cherenkov detector installed at a distance of about 500~km from ESS, has been evaluated.In addition, the choice of such detector will extent the physics program to proton--decay, atmospheric neutrinos and astrophysics searches.The ESS proton linac upgrades, the accumulator ring needed for proton pulse compression, the target station and the physics potential are described. In addition to neutrinos, this facility will also produce at the same time a copious number of muons which could be used by a muon collider.The ESS neutron facility will be fully ready by 2025 at which moment the upgrades for the neutrino facility could start.

A superconducting (SC) linac allows a few orders of magnitude larger average beam current than a normal conducting linac, therefore the powerful beam is expected to lead to outstanding discoveries in various scientific fields, such as high luminosity accelerators and high brilliance light source. However, the high construction and operation costs of the SC linac is a critical issue for realizing large scale facilities. To resolve this problem, we propose a continuous wave (cw) operation of an SC linac shared by electron/positron beams for effective multipurpose utilization. A high current positron source is required for high-energy physics projects: a linear electron-positron collider and a muon collider, while high-current and high-quality electron beams are expected to realize the high brilliant x-ray light sources. As an example, we discuss the injector of the International Linear Collider, an x-ray free-electron laser, and an energy-recovery linac light source. We found a feasible solution of a basic design for the proposed multibeam operation despite the high-quality beam requirements and complicated operation: control of mixed beams without pulsed magnets, and heat load in the cavity, high stability of beam energy, and operation at high average current.

The measurements of the top quark flavor changing neutral current interactions are one of the most important goals of the top quark physics program in the present and the future collider experiments. These measurements provide direct information on non-standard interactions of the top quark. Within the framework of new physics beyond the Standard Model, these interactions can be defined by an effective Lagrangian. In this study, we have investigated the potential of the future $\mu p$ colliders on the top quark flavor changing neutral current interactions through the subprocesses $\gamma q \rightarrow t \rightarrow W b$ where $q=u,c$. These subprocesses have been produced through the main reaction $\mu p \rightarrow \mu \gamma p \rightarrow \mu W b X $ at the LHC$-\mu p$, the FCC$-\mu p$ and the SPPC-$\mu p$. For the main reaction, the total cross sections have been calculated as a function of the anomalous $ tq\gamma $ couplings. In addition, sensitivities on BR($t \rightarrow q \gamma$) at $95\%$ Confidence Level have been calculated. We obtain that the best constraints on BR($t \rightarrow q \gamma$) are at the order of 10$^{-7}$ which is four orders of magnitude better than the LHC's experimental results., Comment: 13 pages 8 figures and 4 tables

Over the past two decades there has been significant progress in developing the concepts and technologies needed to produce, capture, accelerate and collide high intensity beams of muons. At present, a high-luminosity multi-TeV muon collider presents an attractive and very cost-effective option for the next generation lepton-lepton collider, which can allow to fully explore the energy frontier of high energy particle physics in the era following the LHC discoveries. Of growing interest is also a low-energy μ+μ- collider – Higgs factory - at the center of mass energy $\sqrt{s}$=125 GeV that will produce copious number of Higgs particles and explore their properties in greater detail. Synergetic to the collider is the neutrino factory concept that is based on racetrack type muon-decay ring production of the neutrinos. Below we briefly review the concepts and feasibility of the muon accelerator facilities for particle physics research, discuss the status of the corresponding accelerator R&D, and outline directions of the future work.

The Muon Telescope Detector (MTD) is a newly installed detector in the STAR experiment. It provides an excellent opportunity to study heavy quarkonium physics using the dimuon channel in heavy ion collisions. In this paper, we report the muon identification performance for the MTD using proton-proton collisions at s =500 GeV with various methods. The result using the Likelihood Ratio method shows that the muon identification efficiency can reach up to ∼90% for muons with transverse momenta greater than 3 GeV/c and the significance of the J / ψ signal is improved by a factor of 2 compared to using the basic selection.

A new international study has just been launched to design a hadron collider with a centre-of-mass energy of the order of 100 TeV in a new 80–100 km tunnel as a long-term goal. The design study includes a 90–350 GeV lepton collider, seen as a potential intermediate step, and an ep option. This paper reports on the overall parameters and preliminary optics designs with special emphasis on the Interaction Regions and the constraints arising for having to host both the lepton and the hadron colliders. Preliminary hardware specifications, as magnetic field, gradient, lengths and aperture are also presented.

The effect of the photon emission (bremsstrahlung) in the cross section of the process of direct production of the Higgs boson in the future high luminosity electron and muon colliders is calculated. It was found that cross section at the top of the Higgs boson resonance peak is reduced by factor 0.347 for the electron collider and 0.548 for the muon collider. Machine spread of the centre of the mass energy of 4.2MeV (equal to the Higgs width) would reduce peak cross section further, by factor 0.170 and 0.256 (QED and energy spread) for electron and muon beams respectively. Possible uncertainties in the resummed QED calculations are discussed. Numerical results for the lineshape cross section including QED and many values of the machine energy spread are provided., 18 pages, 7 figures; added new references

A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf) test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to $SF_6$ and $O_2$ were measured., 15 pp

We report here a systematic quantitative study on generation and characteristics of an active muon source driven by the interaction of an electron beam within the energy range of 1 to 10 GeV from laser wakefield acceleration (LWFA) with a tungsten target, using Monte Carlo simulations. The 10GeV electron beam, achievable in near future, from LWFA using femtosecond multi-PW lasers is employed to drive the bright source of muon pairs in a compact setup. We show that a highly directional and intense source of short-pulsed GeV muon pairs having peak brightness 5x10^17 pairs/s/cm^2/sr and sub-100-ps duration could be produced using a quasi-monoenergetic 10-fs, 10-GeV electron bunch with 1-mrad divergence and 100-pC charge. The muon pairs are emitted from a point-like source with well-defined position and timing, and the source has size and geometric emittance about 1 mm and 40 microns, respectively. Such muon sources can greatly benefit applications in muon radiography, studies on anomalous dipole moment and rare decays of muons, neutrino oscillations, and an injector of a future compact muon collider., Comment: 10 pages, 8 figures

We discuss the technical feasibility, key machine parameters and major challenges of a 14 TeV c.m.e. muon-muon collider in the LHC tunnel. The luminosity of the collider is evaluated for three alternative muon sources - the PS synchrotron, one of a type developed by the US Muon Accelerator Program (MAP) and a low-emittance option based on resonant muon pair production. Project affordability is also discussed., Comment: 11 p. Version accepted by publisher

A new scheme to produce very low emittance muon beams using a positron beam of about 45~GeV interacting on electrons on target is presented. One of the innovative topics to be investigated is the behaviour of the positron beam stored in a low emittance ring with a thin target, that is directly inserted in the ring chamber to produce muons. Muons can be immediately collected at the exit of the target and transported to two $\mu^+$ and $\mu^-$ accumulator rings and then accelerated and injected in muon collider rings. We focus in this paper on the simulation of the e$^+$ beam interacting with the target, the effect of the target on the 6-D phase space and the optimization of the e$^+$ ring design to maximize the energy acceptance. We will investigate the performance of this scheme, ring plus target system, comparing different multi-turn simulations. The source is considered for use in a multi-TeV collider in ref.[1], Comment: accepted for publication in Physical Review Accelerators and Beams

This article reviews the current status of the nuSTORM facility and shows how it can be utilized to perform the next step on the path toward the realization of a μ+μ−collider. This review includes the physics motivation behind nuSTORM, a detailed description of the facility and the neutrino beams it can produce, and a summary of the short-baseline neutrino oscillation physics program that can be carried out at the facility. The basic idea for nuSTORM (the production of neutrino beams from the decay of muons in a racetrack-like decay ring) was discussed in the literature more than 30 years ago in the context of searching for noninteracting (sterile) neutrinos. However, only in the past 5 years has the concept been fully developed, motivated in large part by the facility's unmatched reach in addressing the evolving data on oscillations involving sterile neutrinos. Finally, this article reviews the basics of the μ+μ−collider concept and describes how nuSTORM provides a platform to test advanced concepts for six-dimensional muon ionization cooling.

One of the possible next steps for high-energy physics research relies on a high-energy hadron or muon collider. The energy of a circular collider is limited by the strength of bending dipoles, and its maximum luminosity is determined by the strength of final focus quadrupoles. For this reason, the high-energy physics and accelerator communities have shown much interest in higher-field and higher-gradient superconducting accelerator magnets. The maximum field of NbTi magnets used in all present high-energy machines, including the LHC, is limited to ∼10 T at 1.9 K. Fields above 10 T became possible with the use of Nb3Sn superconductors. Nb3Sn accelerator magnets can provide operating fields up to ∼15 T and can significantly increase the coil temperature margin. Accelerator magnets with operating fields above 15 T require high-temperature superconductors. This review discusses the status and main results of Nb3Sn accelerator magnet research and development and work toward 20-T magnets.

In the Large High Altitude Air Shower Observatory project, 1221 muon detectors will be built to discriminate cosmic gamma rays from nuclei and between cosmic ray species with energies in 10 13 – 10 18 eV . The muon detector has been designed to meet the physical requirements, according to which two muon detector prototypes have been built at the Yangbajing Cosmic Ray Observatory at the end of 2012 and in October 2014, respectively. The first one has been stably operated for more than 2 years. The performances of the two detectors have been evaluated, especially for position dependence and punch-through effect. In this paper, the design and the performances of the prototype muon detectors are presented.

Six dimensional cooling of large emittance µ + and µ− beams is required in order to obtain the desired luminosity for a muon collider. In our previous study, we demonstrated that a 6D “Garren” ring cooler using both dipoles and solenoids in four 90 0 achromatic arcs can give substantial cooling in all six phase space dimensions. In this paper, we describe the injection/extraction requirements of this four-sided ring. We also present the performance of an achromat-based 6D “Garren” snake cooler. The achromatic design permits the design to easily switch between a closed ring and a snaking geometry on injection or extraction from the ring.

The conceptual design of a compact source of GeV-class muons is presented, based on a plasma based electron–gamma collider. Evaluations of muon flux, spectra and brilliance are presented, carried out with ad-hoc Monte Carlo simulations of the electron–gamma collisions. These are analyzed in the context of a large spread of the invariant mass in the e–gamma interaction, due to the typical characteristics of plasma self-injected GeV electron beams, carrying large bunch charges with huge energy spread. The availability of a compact point-like muon source, triggerable at nsec level, may open a completely new scenario in the muon radiography application field.

The Large Hadron Collider (LHC), located at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, is the largest particle accelerator in the world. With this extraordinary machine, physics at the TeV scale is within human reach. It is a 27 km double ring located 100 m underground.

A muon experimental facility, known as the Muon Science Establishment (MUSE), is one of the user facilities at the Japan Proton Accelerator Research Complex, along with those for neutrons, hadrons, and neutrinos. The MUSE facility is integrated into the Materials and Life Science Facility building in which a high-energy proton beam that is shared with a neutron experiment facility delivers a variety of muon beams for research covering diverse scientific fields. In this review, we present the current status of MUSE, which is still in the process of being developed into its fully fledged form.

High energy particle colliders have been in the forefront of particle physics for more than three decades. At present the near term US, European and international strategies of the particle physics community are centered on full exploitation of the physics potential of the Large Hadron Collider (LHC) through its high-luminosity upgrade (HL-LHC). The future of the world-wide HEP community critically depends on the feasibility of possible post-LHC colliders. The concept of the feasibility is complex and includes at least three factors: feasibility of energy, feasibility of luminosity and feasibility of cost. Here we overview all current options for post-LHC colliders from such perspective (ILC, CLIC, Muon Collider, plasma colliders, CEPC, FCC, HE-LHC) and discuss major challenges and accelerator R&D required to demonstrate feasibility of an energy frontier accelerator facility following the LHC. We conclude by taking a look into ultimate energy reach accelerators based on plasmas and crystals, and discussion on the perspectives for the far future of the accelerator-based particle physics.

The Paul Scherrer Institut in Switzerland operates the high intensity proton accelerator facility HIPA. A 590 MeV kinetic energy proton beam of presently up to 2.4 mA is sent to target stations producing pions, muons and neutrons for fundamental and applied physics. The beam power of 1.4 MW provides the world's highest intensities of low momentum muons which can be stopped in low mass targets. Rates of surface muons of up to about $10^8$/s are being provided to various unique precision particle physics experiments. Two feasibility studies are ongoing to considerably improve the available muon beams. The high intensity muon beamline, HiMB, could deliver on the order of $10^{10}$/s surface muons and the stopped muon cooler, muCool, aims at a gain factor of $10^{10}$ in phase space quality while sacrificing only less than 3 orders of magnitude in intensity for low energy $\mu^+$. These beams will allow a new generation of precision physics experiments with stopped muons and muonium atoms., Comment: Presented at the Seventh Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 20-24, 2016

The production of triple Higgs (H+H-H0), (H+H-h0) and pairwise charged Higgs boson (H+H-) is studied in the context of future linear colliders within the two-Higgs-doublet model (2HDM) type II. The aim is to compare sources of charged Higgs pair through the above processes, that is, double and triple Higgs production. Cross sections are calculated at the leading order in 2HDM type II and Minimal Supersymmetric Standard Model (MSSM). Several orders of magnitude (~104) enhancement are observed in 2HDM compared to MSSM, while no sizable enhancement is seen in muon collider versus electron-positron collider. The analysis is based on a heavy charged Higgs with mass above 500 GeV. It is found that double charged Higgs production cross section (being the same in 2HDM and MSSM) is few femtobarns, while the triple Higgs production cannot exceed a fraction of femtobarn within the parameter space under study.

We report the timing and spatial resolution from the Muon Telescope Detector (MTD) installed in the STAR experiment at RHIC. Cosmic ray muons traversing the STAR detector have an average transverse momentum of 6 GeV/c. Due to their very small multiple scattering, these cosmic muons provide an ideal tool to calibrate the detectors and measure their timing and spatial resolution. The values obtained were ~100 ps and ~1-2 cm, respectively. These values are comparable to those obtained from cosmic-ray bench tests and test beams., Comment: 15 pages, 10 figures

A potential future muon collider requires high field solenoids ( 30 T) for the final cooling stage; the Magnet Division at Brookhaven National Laboratory is undertaking the task of demonstrating feasibility using high-temperature superconductors (HTS). The aim is to construct an all-HTS dual-coil system capable of delivering more than 20 T. Recently, a new record for an all-HTS solenoid has been established with a field of 15 T on-axis. In coil tests, it was noticed that during a fast energy extraction, the current in the solenoids decays faster in comparison to the expected exponential decay. This paper describes the effect and shows how it can be simulated using commercial finite element code. The faster current decay helps to lower the integral current density squared with time by about 10% and is therefore beneficial for quench protection.

The proposed muon collider requires very high field solenoids in the range of 30-50 T. The use of High Temperature Superconductors (HTS) operating at low temperature (~ 4 K) is essential for achieving such high fields in a superconducting magnet. As a part of this program, we have built and successfully tested a 25 mm aperture HTS insert generating 16 T peak field (the highest field ever achieved in an all-HTS magnet), a 100 mm aperture HTS midsert generating 9 T peak field, and designed an outsert with a conventional Low Temperature Superconductor (LTS) to provide additional field. In addition to presenting the test results and progress made in support technologies, we will also discuss a number of challenges associated with the high field HTS magnets. Finally, we present a set of strategies to overcome some of those challenges.

Just over a year ago scientists investigating data from the Large Hadron Collider confirmed the discovery of the Higgs Boson - the holy grail of the Standard Model of particle physics that underpins scientists' understanding of the fundamental workings of our universe. Exactly what sort of collider should come next is a matter of debate. Options for a successor range in size and feasibility, but a central question is what the machine should be colliding. The LHC collides opposing beams of either protons or lead nuclei, which are made up of neutrons. Making a decision about what kind of collider to build depends on what you expect to find. The Higgs Boson was discovered to have a mass of 125GeV (gigaelectronvolts), well within the 1TeV (teraelectronvolt) collision energy scope of proposed lepton colliders. But if new physics beyond the Standard Model such as supersymmetry and string theory exists, as many theorists expect, collision energies beyond the refitted LHC's 14TeV are widely considered essential. The most technologically mature option is the International Linear Collider (ILC) - an electron-positron collider with an initial collision energy of 500GeV and the potential to upgrade to 1TeV. The technology is well established, with a smaller version running at the DESY research centre in Hamburg.

The Large Hadron Collider (LHC) is the largest particle accelerator ever built. The transverse energy density of the nominal beam is 1000 times higher than what was previously achieved in proton storage rings. Tiny fractions of the stored beam suffice to quench a super-conducting LHC magnet (i.e., a situation where part of the magnet exits the superconducting state) or even to destroy parts of the accelerator. The energy in the two LHC beams is sufficient to melt almost one ton of copper.

The idea of converting an electron linear collider into a photon–photon collider through the addition of high power lasers was put forward in the early 1980s. Progress in the field of high average power, short pulse lasers has brought the state of the art within striking range of what would be required to realize a photon collider. In parallel, the necessary modifications to the detector and accelerator to enable a photon collider have been laid out. The basic concept of the photon collider, the requirements for the laser, and the detector and accelerator impact are reviewed in this article.

The Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, is the most powerful particle accelerator in the world. Its aim is to study the physics of elementary particles at the highest energies accessible to accelerators. It is believed that the Higgs boson (a last particle predicted by the Standard Model that is yet to be found) and the lightest particles of the Minimal Supersymmetric Model should be accessible at the LHC energies. These lectures give a short overview of the physics program and the technological challenges this collider faces.

High energy particle colliders have been in the forefront of particle physics for more than three decades. At present the near term US, European and international strategies of the particle physics community are centered on full exploitation of the physics potential of the Large Hadron Collider (LHC) through its high-luminosity upgrade (HL-LHC). A number of next generation collider facilities have been proposed and are currently under consideration for the medium- and far-future of the accelerator-based high energy physics. In this paper we offer a uniform approach to evaluation of various accelerators based on the feasibility of their energy reach, performance reach and cost range. We briefly review such post-LHC options as linear e+e- colliders in Japan (ILC) or at CERN (CLIC), muon collider, and circular lepton or hadron colliders in China (CepC/SppC) and Europe (FCC). We conclude with a look into ultimate energy reach accelerators based on plasmas and crystals, and some perspectives for the far future of accelerator-based particle physics., 8 pp. The European Physical Society Conference on High Energy Physics, 22-29 July 2015, Vienna, Austria

The Compact Muon Solenoid (CMS) experiment in the Large Hadron Collider (LHC) at CERN has been the tool to performing ground-breaking research in high energy physics. The CMS detector has been built over the last two decades by an international collaboration of scientists from all over the world. Two years after its operation, the two experiments ATLAS and CMS have announced in 2012 the discovery of the Higgs boson, a long awaited particle responsible to give elementary particles their respective masses.After the first 3 years of operation at moderate luminosity, the LHC is entering a new phase of high luminosity and energy regimes, which will put stringent requirements on the detectors.The CMS experiment has planned a rigorous plan of upgrade of its different components to cope with the harsh conditions imposed by the new regime. One of the subsystem of CMS detector that will require upgrade is the muon system. This latter detects muon particles, which are the signature of most of the interesting physics channels we are looking for at the LHC.The Qatar team, together with an international team of scientists, has proposed the Gas Electron Multiplier (GEM) as the future detecting element of the upgrade of the muon system.We have conducted an extensive simulation program to assess the GEM detector and optimize it for the future upgrade.During this project, various simulations have been conducted to predict the efficiency and time resolution of the GEM. The simulations, which have been conducted using ANSYS, computational fluid dynamics software, focus on producing the electric field maps inside the detector. In addition, the resulting electron avalanche was simulated based on the solution of the Boltzmann equation. A signal was then generated to study the gain, resolution, and other parameters. During this work, several conditions were simulated in order to reach the optimum conditions under which the GEM would be most effective. These simulations had to be conducted using a supercomputing facility since their range surpasses the regular computing powers of personal computers. Using Raad, the cluster at Texas A&M University at Qatar, helped widen the scope of the simulations to approach a realistic situation that would occur within the CMS.Furthermore, as part of its next upgrade, a novel detector, the Fast Timing Micropattern (FTM) detector is being considered as a possible beneficial addition to the CMS. Initial investigations of the FTM detector have shown a considerable improvement in the time resolution that is proportional to the number of layers. In addition, the use of resistive WELL techniques solves the problem of spark occurrences and discharges that such detectors experience with high electric fields. It also differs from the GEM in the sense that the gain is extracted at every multiplication stage rather than at the very last level of the detector where the readout plane exists. The FTM detector could be cost-efficient in its assembly process. Simulations are being further extended in order to evaluate the FTM's performance and optimize its gain and other resulting parameters.