Muon Collider Collaboration Research Articles

Single axion-like particles production in the γγ channel at high energy muon colliders

Axion-like particles (ALPs), which are pseudo-scalar particles, appear in various new physics models with the spontaneous global symmetry breaking. The difference between ALPs and axion models is that for the former both masses and couplings of ALPs are free parameters. It appears that the ALPs with masses above 1[Formula: see text]GeV are beyond the reach of low-energy accelerators, existing cosmological and astrophysical constraints, while high-energy colliders provide unique possibilities to explore such particles. With the establishment of the International Muon Collider Collaboration, muon colliders have been widely concerned. In general, ALPs are mainly produced at muon colliders through the [Formula: see text] annihilation and electroweak vector-boson-fusion (VBF) processes. In this paper, we study the prospect of the production of heavy ALPs with mass greater than 10[Formula: see text]GeV via the massless [Formula: see text]-fusion process at the multi-TeV muon collider. Focusing on the couplings of ALPs to the Standard Model gauge bosons, we obtain the excluding and discovering capabilities for ALPs at the 3[Formula: see text]TeV and 10[Formula: see text]TeV muon colliders. Our numerical results suggest that the multi-TeV muon collider may be more sensitive to ALPs with the mass of 35–400[Formula: see text]GeV than LHC, and can provide the possibility to search for ALPs with masses greater than 3[Formula: see text]TeV. In addition, we also discuss the effect of narrow width approximation on the ALP search sensitivity.

The Contribution of Photon, Z Boson, Higgs, Radion and Unparticle to the Process in Randall-Sundrum model

The process is studied from unparticle physics perspective in Randall-Sundrum model. We calculated and evaluated the cross sections independently for photon (γ), Z boson (Z), vector unparticle (Uμ), Higgs (h), radion ( ), scalar unparticle (U) exchange. Numerical calculations showed that the contribution of unparticle exchange dominates in a very high energy region. While γ and Z contribute mainly in the lower region, h and contribution is negligible in comparison with the other exchanges. The results are plotted in the energy ranges available in the present designs of accelerators and near future high energy frontier muon colliders as shown by International Muon Collider Collaboration articles.
 Keywords: Muon production, unparticle physics, collisions, muon colliders, Randall-Sundrum model.

Detector design for a multi-TeV muon collider

The design of a feasible multi-TeV muon collider facility is the mandate of the International Muon Collider Collaboration based at CERN and is considered with great interest along the presently on-going US Snowmass 2021 process. The physics potential of such a novel future collider is overwhelming, ranging from precision measurements to direct searches for new Physics. Despite the machine-design challenges, it gives access to the uncharted territory of leptonic collisions at a center-of-mass energy of 10 TeV or higher with an instantaneous luminosity up to a few 1035 cm−2 s−1. The experiment design, the detector technology choices, and the event reconstruction tools are strongly affected by the presence of the beam-induced background, generated by the interactions of the muon decay products with the machine elements. Full simulation studies at s=1.5 TeV and 3 TeV, adopting the CLIC experiment technologies, represent the starting point to optimize the detector design and propose future dedicated R&D.

Prospects of a future multi-TeV muon collider

A multi-TeV muon collider is a discovery machine and an invaluable tool for many new standard model precision measurements such as the shape of the Higgs boson potential. The update of the European Strategy for Particle Physics recognized the unique opportunity of a muon collider to reach the energy frontier, despite the challenges to produce intense collimated muon beams. The options of a collider at 3 TeV and a collider at 10 TeV or above are the main focus of the forming International Muon Collider Collaboration as well as of the discussion panels at the ongoing US Snowmass process.

Progress on Design and Construction of a MuCool Coupling Solenoid Magnet

The MuCool program undertaken by the US Neutrino Factory and Muon Collider Collaboration is to study the behavior of muon ionization cooling channel components. A single superconducting coupling solenoid magnet is necessary to pursue the research and development work on the performance of high gradient, large size RF cavities immersed in magnetic field, which is one of the main challenges in the practical realization of ionization cooling of muons. The MuCool coupling magnet is to be built using commercial copper based niobium titanium conductors and cooled by two cryo-coolers with each cooling capacity of 1.5 W at 4.2 K. The solenoid magnet will be powered by using a single 300 A power supply through a single pair of binary leads that are designed to carry a maximum current of 210 A. The magnet is to be passively protected by cold diodes and resistors across sections of the coil and by quench back from the 6061 Al mandrel in order to lower the quench voltage and the hot spot temperature. The magnet is currently under construction. This paper presents the updated design and fabrication progress on the MuCool coupling magnet.

Review of U.S. Neutrino Factory Studies

We summarize the status of the two U.S. feasibility studies carried out by the Neutrino Factory and Muon Collider Collaboration (NFMCC) along with recent improvements to Neutrino Factory design developed during the American Physical Society (APS) Neutrino Physics Study. Suggested accelerator topics for the International Scoping Study (ISS) are also indicated.

A free-jet Hg target operating in a high magnetic field intersecting a high-power proton beam

A proof-of-principal experiment to investigate the interaction of a proton beam, high magnetic field, and high- Z target is planned to take place at CERN in early 2007. This experiment is part of the Muon Collider Collaboration, with participants from Brookhaven National Laboratory, Princeton University, Massachusetts Institute Of Technology, European Organization for Nuclear Research-CERN, Rutherford Appleton Laboratory, and Oak Ridge National Laboratory. An unconstrained mercury jet target system that interacts with a high power (1 MW) proton beam in a high magnetic field (15 T) is being designed. The Hg jet diameter is 1-cm with a velocity up to 20 m/s. A laser optical diagnostic system will be incorporated into the target design to permit observation of the dispersal of the jet resulting from interaction with a 24 GeV proton beam with up to 20×10 12 ppp. The target system includes instruments for sensing mercury vapor, temperature, flow rate, and sump tank level, and the means to position the jet relative to the magnetic axis of a solenoid and the proton beam. The design considerations for the system include all issues dealing with safely handling approximately 23 l of Hg, transporting the target system and the mercury to CERN, decommissioning the experiment, and returning the mildly activated equipment and Hg to the US.

Review of North American Neutrino Factory R&D

We report here on the R&D programme of the U.S. Neutrino Factory and Muon Collider Collaboration. Our effort includes work on targetry, muon ionization cooling, simulation work and development of superconducting RF cavities. In addition, we are involved in the international effort towards a muon ionization cooling experiment (MICE). Recent activities in all these areas will be described.

An R&D program for targetry and capture at a neutrino factory and muon collider source

The need for intense muon beams for muon colliders and for neutrino factories based on muon storage rings leads to a concept of 1–4 MW proton beams incident on a moving target that is inside a 20-T solenoid magnet, with a mercury jet as a preferred example. Novel technical issues for such a system include disruption of the mercury jet by the proton beam and distortion of the jet on entering the solenoid, as well as more conventional issues of materials lifetime and handling of activated materials in an intense radiation environment. As part of the R&D program of the Neutrino Factory and Muon Collider Collaboration, an R&D effort related to targetry is being performed within the context of experiment E951 at Brookhaven National Laboratory, first results of which are reported here.

Technical design aspects of Feasibility Study-II

Feasibility Study-II examined a high-performance Neutrino Factory providing 1×10 20 neutrinos per year aimed at a long-baseline detector. The Study was sponsored jointly by BNL and the Neutrino Factory and Muon Collider Collaboration and is based on a 1 MW proton driver operating at 24 GeV , i.e., an upgraded version of the AGS accelerator. Compared with the earlier FNAL-sponsored study (Feasibility Study-I), there is a sixfold improvement in performance. Here we describe details of the implementation of Study-II concepts and discuss their efficacy. Alternative approaches that will be pursued in follow-on R&D activities are also described briefly.

Conceptual design of pion-capture magnets of up to 15 cm bore and 20 T peak field

For the Neutrino Factory and Muon Collider Collaboration, BNL has considered solenoidal magnet systems of several types to capture pions generated by bombarding a mercury jet with multi-GeV protons. The magnet systems generate up to 20 T, uniform to 5% throughout a cylindrical volume 0.15 m in diameter and 0.6 m long. Axially downstream the Held ramps gradually downward by a factor of sixteen, while the bore increases fourfold. The steady-state system needed for an accelerator has many superconducting coils and a radiation-resistant insert of mineral-insulated hollow conductor. Less costly, pulsed systems suffice to study pion capture and the effect of a magnetic field on a jet hit by a proton beam. BNL has explored three types of magnets, each with its principal coils precooled by liquid nitrogen. One type employs two sets of coils energized sequentially. Charged in 23 s by a power supply of 5 MVA, the 14-ton outer set generates 10 T and stores 28 NU, from which, in 1/3 s, to charge a half-ton inner coil that adds 12 1/2 T to the 7 1/2 T remaining from the outer set. An alternative design uses 25 MVA to energize, in 1.4 s, a single 3-ton set of coils. The third type bows to budgetary constraints and is more modest in size and performance. A magnet of 2-3 tons generates 10-11 T with only 2 MVA, in a bore big enough (11 cm) to accommodate the jet. It foregoes the field ramp that improves pion retention.

Neutrino factory and muon collider collaboration R&D program

The Neutrino Factory and Muon Collider Collaboration (MC) comprises some 140 scientists and engineers located at U.S. National Laboratories and Universities, and at a number of non-U.S. research institutions. In the past year, the MC R&D program has shifted its focus mainly toward the design issues related to the development of a Neutrino Factory based on a muon storage ring. In this paper the status of the R&D activities is described, and future plans are outlined.

A feasibility study of a neutrino source based on a muon storage ring

We present the results of a study commissioned by the Fermilab Director on the feasibility of an intense neutrino source, based on a muon storage ring. Muon colliders have been discussed as an alternate route to very high-energy lepton colliders. As a by-product, such a collider would produce very intense neutrino beams because of the decaying muons circulating in the storage ring. In a dedicated storage ring, these neutrino beams could be produced in long straight sections which would point towards long, medium or short baseline detectors, opening up a whole new class of neutrino physics experiments because of the enormous neutrino flux that, in principle, could be achieved in such a facility as compared to more standard fixed target sources. Intense pion sources in combination with powerful emittance cooling strategies for the comparatively large muon emittance are necessary to make this type of neutrino source as well as a muon collider, feasible for a possible future high energy physics facility. The Neutrino Factory and Muon Collider collaboration studies the different subsystems being required and presently focuses on the layout of a neutrino source based on a 50GeV Muon Storage Ring.