Narrow Results

From several neutrino oscillation experiments, we understand now that neutrinos have mass. However, we really do not know what mechanism is responsible for producing this neutrino mass. Current or planned neutrino experiments utilize neutrino beams and long-baseline detectors to explore flavor mixing but do not address the question of the origin of neutrino mass. In order to begin answering that question, neutrino interactions need to be explored at much higher energies. This paper outlines a program to explore neutrinos and their interactions with various particles through a series of experiments involving colliding neutrino beams.

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 nonstandard 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 $\gamma q\to t\to Wb$, where $q=u,c$. These subprocesses have been produced through the main reaction $\mu p\to \mu \gamma p\to \mu WbX$ 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 $\mathrm{\text{BR}}(t\to q\gamma )$ at 95% Confidence Level have been calculated. We obtain that the best constraints on $\mathrm{\text{BR}}(t\to q\gamma )$ are at the order of $10^{-7}$ which is four orders of magnitude better than the LHC’s experimental results.

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 1GeV 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 ${\mu }^{+}{\mu }^{-}$ 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 10GeV via the massless $\gamma \gamma$-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 3TeV and 10TeV muon colliders. Our numerical results suggest that the multi-TeV muon collider may be more sensitive to ALPs with the mass of 35–400GeV than LHC, and can provide the possibility to search for ALPs with masses greater than 3TeV. In addition, we also discuss the effect of narrow width approximation on the ALP search sensitivity.

The RFOFO ring is considered to be one of the most promising six-dimensional cooling channels proposed for the future muon collider. It has a number of advantages over other cooling channels, but it also has certain drawbacks. The injection and extraction issue as well as the absorber overheating are its main problems. In this article the simulations of a possible solution to these problems, the RFOFO helix, commonly referred to as the Guggenheim channel, are studied in detail. The details of the tracking studies of both the idealized and realistic lattices are presented and compared to the performance of the underlying RFOFO cooling ring design.

The idea of a muon collider has been developed since the 70s. In these projects, muons are produced at targets at low or intermediate energies. Then, after reducing the emittance, they should accelerate very quickly, since the lifetime is very short (${\tau }_{\mu }=2\mu$s in the rest frame). Here, we want to propose the option of the collider, where the muons can be obtained on the hadron collider at high energy using a focusing bent crystals.

A brief review is given of the development of linacs, cyclotrons, synchrotrons (also accumulators) and FFAG accelerators for a variety of high power hadron beam applications.

Muon Cooling is discussed, showing its importance both for a future Neutrino Factory and the Muon Collider. The physics cases are introduced and a comparison of the two facilities is done, which illustrates similarities and differences. R&D programs, with special emphasis on the presently starting cooling experiment MICE, are discussed.

A brief review is given of the development of linacs, cyclotrons, synchrotrons (also accumulators) and FFAG accelerators for a variety of high power hadron beam applications.

Parameters are given of muon colliders with center of mass energies of 1.5 and 3 TeV. Pion production is from protons on a mercury target. Capture, decay, and phase rotation yields bunch trains of both muon signs. Six dimensional cooling reduces the emittances until the trains are merged into single bunches, one of each sign. Further cooling in 6 dimensions is then applied, followed by final transverse cooling in 50 T solenoids. After acceleration the muons enter the collider ring. Ongoing R&D is discussed.

Muon Colliders [1] need intense, very short, proton bunches. The requirements are presented and a number of possible bunching systems discussed. The best solution uses a small super-conducting buncher ring with 6 bunches that are taken though separate transports and combined on the target.

An accelerator complex that can produce ultra-intense beams of muons presents many opportunities to explore new physics. This facility is unique in that it can present a physics program that can be staged and thus move forward incrementally, addressing exciting new physics at each step. An intense cooled low-energy muon source can be used to perform extraordinarily precise lepton flavor violating experiments and these same muons can be accelerated to be used in a Neutrino Factory or energy-frontier Muon Collider. In this paper I will give an introduction to muon accelerator facilities and their physics capabilities and then will discuss some of the limiting technologies that must be developed in order to make these concepts a reality.