The discovery of the Higgs particle at 125 GeV is demanding a detailed knowledge of the properties of this fundamental component of the Standard Model. To that aim various proposals of electron and muon colliders have been put forward for precision studies of the partial widths of the various decay channels. It is shown that in the case of a Higgs factory through a muon collider, sizeable radiative effects - of order of 50% - must be carefully taken into account for a precise measurement of the leptonic and total widths of the Higgs particle. Similar effects do not apply in the case of Higgs production in electron-positron colliders.
We describe a class of models of electroweak symmetry breaking that involves strong dynamics and top quark condensation. A new scheme based upon a seesaw mechanism appears particularly promising. Various implications for the first-stage muon collider are discussed.
Muon colliders might greatly extend the energy frontier of collider physics. One can contemplate circular colliders with center-of-mass energies in excess of 10 TeV. Some physics issues that might be relevant at such a machine are discussed.
High luminosity muon-muon colliders would provide a powerful new probe of Higgs boson physics through $s$-channel resonance production. We discuss the prospects for detection of Higgs bosons and precision measurements of their masses and widths at such a machine.
Signatures for sleptons, which have been extensively studied for the Next Linear Collider, are reexamined taking into account some of the different features of a First Muon Collider.
The muon-proton ($μp$) collider is an interesting option of the muon collider. Here we discuss the physics potential of the $μp$ collider; especially, leptoquarks and contact interactions. We calculate the sensitivity reach for the second generation leptoquarks and leptogluons, $R$-parity violating squarks, and $μq$ contact interactions for the $μp$ colliders of various energies and luminosities.
We discuss the model independent parameterization for a strongly interacting electroweak sector. Phenomenological studies are made to probe such a sector for future colliders such as the LHC, $e^+e^-$ Linear collider and a muon collider.
We analyze allowed region of muon anomalous magnetic moment (muon $g-2$), satisfying lepton flavor violations, $Z$ boson decays, and collider physics, in a framework of multi-charged particles. Then we explore the typical size of the muon $g-2$, and discuss which modes dominantly affect muon $g-2$.
We study the discovery potential for heavy axion-like particles (ALPs) and the perspectives for determining their coupling properties at a muon collider. Focusing on their couplings to the Standard Model (SM) gauge bosons $γ, Z, W^\pm$, we show that a high-energy muon collider can substantially extend the mass coverage, essentially reaching the kinematic limit of the collider energy. The unique kinematics allow for non-ambiguous determination of the individual coupling strengths. The associated production via $μ^+μ^-$ annihilation and the VBF processes with the tagged outgoing muons can be uti…
This contribution describes precision width measurements that could be done at a muon collider for very narrow resonances as the Higgs or a possible pseudogoldstone boson, or for almost degenerate resonances as the A0 and H0 in the MSSM for large values of tanβ.
Muon colliders are expected to naturally have a small spread in beam energy making them an ideal place to study the excitation curve. We present the parameter determinations that are possible from measuring the total cross section near threshold at a $μ^+μ^-$ collider.
Conceptual design studies are underway for muon colliders and other high-current muon storage rings that have the potential to become the first true ``neutrino factories''. Muon decays in long straight sections of the storage rings would produce precisely characterized beams of electron and muon type neutrinos of unprecedented intensity. This article reviews the prospects for these facilities to greatly extend our capabilities for neutrino experiments, largely emphasizing the physics of neutrino interactions.
We have investigated the production potential of the spin-1/2 excited muons, predicted by the preonic models, at the four SPPC (Super Proton-Proton Collider)-based muon-proton colliders in different center-of-mass energies. For the signal process μp\rightarrowμ^{\star}X\rightarrowμγX, the production cross-section and the decay width values of the excited muons have been calculated. The pseudorapidity and transverse momentum distributions of the final state particles of muons and photons have been obtained to be determine the kinematical cuts best suited for discovery of the excited muons. By a…
We show that new physics explanations of the muon $g-2$ anomaly by the contributions of new leptons mediated by the standard model Higgs boson necessarily lead to large rates for $μ^+ μ^- \to hh$ and $μ^+ μ^- \to hhh$ irrespectively of details of the model or the scale of new physics. For new leptons with the same quantum numbers as the standard model leptons, cross sections are expected to be about 240 ab for $μ^+ μ^- \to hh$ independently of the center of mass energy, $\sqrt{s}$, and about 2.7 ab for $μ^+ μ^- \to hhh$ for $\sqrt{s} = 1$ TeV and growing quadratically with $\sqrt{s}$. Predicti…
We discuss the physics potential of the $μp$ collider; especially, leptoquarks, leptogluons, R-parity violating squarks, contact interactions, and large extra dimensions. We calculate the sensitivity reach for these new physics at $μp$ colliders of various energies and luminosities.
We study the excited muon production at the FCC based muon-hadron colliders. We give the excited muon decay widths and production cross section. We deal with the $μp\rightarrowμ^{\star}q\rightarrowμγq$ process and we plot the transverse momentum, rapidity and invariant mass distributions of final state particles to get the discovery cuts. By using discovery cuts, we get the mass limits for excited muons. It is shown that the discovery limits on the mass of $μ^{\star}$ are 2.2 TeV, 5.9 TeV and 7.5 TeV for $\mu63$-FCC, $\mu750$-FCC and $\mu1500$-FCC, respectively.
Pseudoscalar and charged Higgs bosons production in the processes $μ^+ μ^-\to P^0_i Z^0$, $μ^+μ^- \to H^{\pm}W^{\mp}$ within the models with several Higgs doublets and singlets is considered.
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 …
We explore the sensitivity of directly testing the muon-Higgs coupling at a high-energy muon collider. This is strongly motivated if there exists new physics that is not aligned with the Standard Model Yukawa interactions which are responsible for the fermion mass generation. We illustrate a few such examples for physics beyond the Standard Model. With the accidentally small value of the muon Yukawa coupling and its subtle role in the high-energy production of multiple (vector and Higgs) bosons, we show that it is possible to measure the muon-Higgs coupling to an accuracy of ten percent for a …
After an extremely brief overview of the discovery reach for Z' bosons, we will discuss the physics of Kaluza-Klein(KK) excitations of the Standard Model gauge bosons that can be explored by a high energy muon collider in the era after the LHC and TeV Linear Collider. We demonstrate that the muon collider is a necessary ingredient in the unraveling the properties of such KK states and, perhaps, proving their existence.
The eventual prospect of muon colliders reaching several TeV encourages us to consider the experimental opportunities presented by very copious stores of muons, approaching $10^{21}$ per year. I summarize and comment upon some highlights of the Fermilab Workshop on Physics at the First Muon Collider and at the Front End of a Muon Collider. Topics include various varieties of $μμ$ colliders, $μp$ colliders, and applications of the intense neutrino beams that can be generated in muon storage rings.
The prospects of detecting neutral Higgs bosons in the minimal supersymmetric model via their decays into muon pairs at the LHC are investigated. The CMS detector performance is adopted for a realistic study of observability. It is found that the muon pair decay mode might provide a very promising channel to search for the neutral Higgs bosons of minimal supersymmetry. This channel will allow precise mass reconstruction for neutral Higgs bosons.
We study a possibility of a measurement of muon Yukawa couplings in s-channel Higgs boson production at a muon collider with transversely polarized beams. We investigate sensitivity to the relative size of the CP-odd and CP-even muon Yukawa couplings. Provided the event rate observed justify the operation of the $μ^+μ^-$ Higgs boson factory, we have found that polarization degree 40% is sufficient to resolve the CP nature of a single resonance as well as disentangle it from two overlapping CP conserving resonances.
We calculate Higgs production cross sections at a muon collider in the Two Higgs Doublet Model of type II. The most interesting productions channels are mu^- mu^+ --> h^0 Z^0, H^0 Z^0, H^- H^+, A^0 Z^0 and H^{-/+} W^{+/-}. The last channel is compared with the production processes p pbar --> H^{-/+} W^{+/-} X and p p --> H^{-/+} W^{+/-} X at the Tevatron and LHC energies, respectively, for large values of tan(beta).
The beam energy spread is a major issue in future attempts to study the $t\overline{t}$ threshold at $e^+e^-$ colliders. Muon colliders are expected to naturally have narrow band beams making them an ideal place to study the excitation curve. We present the parameter determinations that are possible from measuring the total cross section near threshold at a $μ^+μ^-$ collider.
We review the role of a muon collider in the study of Higgs bosons via production in the s-channel. Very precise measurements of a Standard Model-like Higgs boson mass and total width can be performed, and may lead to a discrimination between a Standard Model Higgs boson and the light Higgs boson of the minimal supersymmetric theory. The heavier Higgs bosons from a supersymmetric theory or an exotic Higgs sector can be studied in the s-channel. A muon collider may play a crucial role in separating the overlapping signals for two heavy nearly degenerate Higgs bosons, and may play an important r…
Muon colliders offer special opportunities to discover and study new physics. With the high intensity source of muons at the front end, orders of magnitude improvements would be realized in searches for rare muon processes, in deep inelastic muon and neutrino scattering experiments, and in long-baseline neutrino oscillation experiments. At a 100 to 500 GeV muon collider, neutral Higgs boson (or techni-particle) masses, widths and couplings could be precisely measured via s-channel production. Also, threshold cross-section studies of W+ W-, t t-bar, Zh and supersymmetric particle pairs would pr…
We propose a muon-proton collider with asymmetrical multi-TeV beam energies and integrated luminosities of $0.1-1$ ab$^{-1}$. With its large center-of-mass energies and yet small Standard Model background, such a machine can not only improve electroweak precision measurements but also probe new physics beyond the Standard Model to an unprecedented level. We study its potential in measuring the Higgs properties, probing the R-parity-violating Supersymmetry, as well as testing heavy new physics in the muon $g-2$ anomaly. We find that for these physics cases the muon-proton collider can perform b…
Current muon anomalous magnetic moment data have challenged the SM, and seems to open a window to new Physics. Since the difference between SM and experimental predictions is approximately $2.6σ$. In the framework of the General Two Higgs Doublet Model (2HDM), we calculate the muon anomalous magnetic moment to get lower and upper bounds for the Flavor Changing Yukawa couplings (FC) in the leptonic sector. We also obtain lower bounds for the mass of the Pseudoscalar Higgs ($m_{A^ 0}$, as a function of the parameters of the model.
Muon colliders are an exciting possibility for reaching the highest energies possible on the shortest timescale. They potentially combine the greatest strengths of $e^+e^-$ and $pp$ colliders by bridging the energy versus precision dichotomy. In this paper we study the sensitivity of Higgs properties that can be achieved with a future 3 or 10 TeV muon collider from single Higgs production. The results presented here represent the first comprehensive picture for the precision achievable including backgrounds and using fast detector simulation with Delphes. Additionally, we compare the results o…
I review possible explanations of the muon g-2 anomaly in models with extended Higgs and matter sectors, focusing on extensions of the standard model and the two Higgs doublet model with vectorlike leptons. Predictions of these models, namely the modifications of muon Yukawa and gauge couplings, that can be searched for at the LHC and future colliders, are summarized. I also discuss striking predictions for di-Higgs and tri-Higgs signals at a muon collider that can be tested even at very low energies. Furthermore, I briefly comment on other interesting features and signatures of models with ex…
We discuss the potential for making precision measurements of $M_W$ and $M_T$ at a muon collider and the motivations for each measurement. A comparison is made with the precision measurements expected at other facilities. The measurement of the top quark decay width is also discussed.
There are serious discussions for building a muon collider with $μ^{+}μ^{-}$ collisions at c.o.m. energies up to 4 TeV. We point out that the bileptonic gauge bosons predicted in some extensions of the Standard Model would be readily discernable from the backward scattering cross-section, for bilepton masses up to a substantial fraction of the c.o.m. energy.
In a previous publication, we showed that a high energy muon collider can make decisive statements about the electroweak (WIMP) Dark Matter (DM), reaching a DM mass which could give the observed thermal relic abundance. In this document, we report new studies of the spin-$0$ minimal WIMP DM at high energy muon colliders, and update our results on the fermionic spin-$1/2$ case. We find that, by combining multiple inclusive missing mass search channels, it is possible to fully cover the thermal targets of fermionic and scalar doublets, and Dirac triplet, with a 10 TeV muon collider. Higher energ…
We study the experimental constraints from electron and muon $g-2$ factors on the Higgs masses and Yukawa couplings in the $T'$ model, and thereby show that the discrepancy between the standard model prediction and experimental value of muon anomalous $g-2$ factor can be easily accommodated.
We study the Higgs boson mass and the muon anomalous magnetic moment (the muon $g-2$) in a supersymmetric standard model with vector-like generations. The infrared physics of the model is governed by strong renormalization-group effects of the gauge couplings. That leads to sizable extra Yukawa couplings of Higgs doublets between the second and vector-like generations in both quark and lepton sectors. It is found with this property that there exist wide parameter regions where the Higgs boson mass and the muon $g-2$ are simultaneously explained.
One very light neutral Higgs scalar with mass, say, below 40-50 GeV is still allowed in the non-supersymmetric 2HDM (Model II), while the remaining particles of the Higgs sector in this model have to be heavier. The possibility of testing such a scenario at Muon Colliders is discussed.
We discuss the physics of Kaluza-Klein excitations of the Standard Model gauge bosons that can be explored by a high energy muon collider in the era after the LHC and TeV Linear Collider. We demonstrate that the muon collider is a necessary ingredient in the unraveling the properties of such states and, perhaps, proving their existence. The possibility of observing the resonances associated with the excited KK graviton states of the Randall-Sundrum model is also discussed.
A muon collider would be a powerful probe of flavor violation in new physics. There is a strong complementary case for collider measurements and precision low-energy probes of lepton flavor violation (as well as CP violation). We illustrate this by studying the collider reach in a supersymmetric scenario with flavor-violating slepton mixing. We find that the collider could discover sleptons and measure the slepton and neutralino masses with high precision, enabling event reconstruction that could cleanly separate flavor-violating new physics signals from Standard Model backgrounds. The discove…
Higgs resonance signals and backgrounds at the First Muon Collider are discussed. Effects due to beam polarization and background angular distributions (forward-backward charge asymmetries) are examined. The utility of those features for improving precision measurements and narrow resonance ``discovery'' scans is described.
One of the useful features of muon colliders is the naturally narrow spread in beam energies. Measurements of threshold cross sections then become a prime candidate for precision measurements of particle masses, widths, and couplings as well as determining particle spin. We describe the potential for measuring cross sections near threshold in supersymmetric theories.
In supersymmetric models with R-parity violating interactions, sneutrinos may be produced as $s$-channel resonances at $μ^+ μ^-$ colliders. We demonstrate that, for R-parity violating couplings as low as $10^{-4}$, sneutrinos can be discovered and their couplings measured to high accuracy. The excellent beam energy resolution of muon colliders is found to be especially useful for studying such resonances in certain cases.
The top quark will be extensively studied at future muon colliders. The threshold cross section can be measured precisely, and the small beam energy spread is especially effective at making the measurement useful. We report on all the activities of the top quark working group, including talks on top quark physics at other future colliders.
I discuss high mass signatures of technicolor that would be observable at a very high energy muon collider. Most intriguing is the spectrum of spin-one technihadrons, rho_T, omega_T and A_{1T}, which may extend to 100 TeV and beyond in a walking technicolor theory.
Current experimental data from the $g-2$ muon factor, seems to show the necessity of physics beyond the Standard Model (SM), since the difference between SM and experimental predictions is 2.6$σ$. In the framework of the General Two Higgs Doublet Model (2HDM), we calculate the muon anomalous magnetic moment to get lower and upper bounds for the Flavour Changing (FC) Yukawa couplings in the leptonic sector. We also obtain lower bounds for the mass of the pseudoscalar Higgs ($m_{A^0}$) as a function of the parameters of the model.
We investigate the effects of R-parity-violating $LL\bar E$ and $LQ\bar D$ operators on the production of fermion pairs at a $μ^+ μ^-$ collider with high energy and luminosity. We show that comparison of angular distributions leads to useful discovery limits for the R-parity-violating couplings, especially if the exchanged sfermions turn out to be heavy. Products of these couplings can also be probed well beyond present experimental limits, especially for the second and third generations. Finally, we compare results at a muon collider with those obtainable from an $e^+ e^-$ linear collider wit…
We investigate the production of Higgs bosons in neutral- and charged-current interactions at a future Muon-Ion Collider (MuIC) with emphasis on $H^0 \to c\overline{c}$ decay. In particular, we focus on the leading production mechanisms and explore the impact of a range of Parton Distribution Function (PDF) scenarios, with emphasis on the role of heavy intrinsic quark flavor. We emphasize estimates of non-resonant di-charm background production and explore the impact of this background on a possible future measurement of $H^0 \to c\overline{c}$ at a future Muon-Ion Collider facility.
The potential of muon colliders to address fundamental physics issues is explored, with emphasis on understanding the nature of electroweak symmetry breaking. The $s$-channel production of Higgs bosons, unique to a muon collider, along with precision measurements of W^+W^-, t\bar t, and Zh thresholds would determine the properties of Higgs bosons and test electroweak radiative corrections. At the high energy frontier, a 4 TeV muon collider is ideally suited to study either the production of supersymmetric scalar particles or a strongly interacting WW sector.
