Search

We explore the potential of the $e^+ e^-$ colliders to discover dark matter and determine its properties such as mass and the spin. For this purpose we study spin zero and spin one-half cases of dark matter, $D$ which belongs to $SU(2)$ weak doublet and therefore has the charged doublet partner, $D^+$. For the case of scalar dark matter we chose Inert Doublet Model, while for the case of fermion dark matter we suggest the new minimal fermion dark matter model with only three parameters. We choose two benchmarks for the models under study which provide the correct amount of observed DM relic density and consistent with the current DM searches. We focus on the particular process $e^+ e^- \to D^+ D^- \to D D W^+ W^- \to DD(q \bar{q})(\mu^\pm\nu)$ at 500 GeV ILC collider which gives rise to the "di-jet +$\mu$ + missing $E_T$" signature and study it at the level of fast detector simulation, taking into account Bremsstrahlung and ISR effects. We have found that two kinematical observables -- the energy of the muon, $E_\mu$, and the angular distribution of $W$-boson, reconstructed from di-jet, $\cos\theta_{jj}$ are very powerful in determination of DM mass and spin, respectively. In particular we have demonstrated that in case of fermion DM, the masses can be measured with a few percent accuracy already at 500 fb$^{-1}$ integrated luminosity. At the same time, the scalar DM model which has about an order of magnitude lower signal, requires about factor of 40 higher luminosity to reach the same accuracy in the mass measurement. We have found that one can distinguish fermion and scalar DM scenarios with about 2 ab$^{-1}$ total integrated luminosity or less without using the information on the cross sections for benchmarks under study., Comment: Updated with the Electroweak Precision S,T,U oblique parameters analytical and numerical evaluation

I discuss, what really new could give Photon Colliders ($\gamma\gamma$ and $e\gamma$) after LHC and \epe Linear Collider operations.

I discuss the physics potential of photon colliders in the fields which was not discussed in the other reports at Conference. Muon colllider will supplement substantially the photon colliders in the study of problems in gauge boson physics. These colliders provide the best place for study of above problems. Besides, muon colliders will give quite new field in the study of problems in QCD.

I consider the process $\mu^+\mu^-\to e\bar{\nu}W^+$ in the case when the effective mass of the $(e\bar\nu)$ system than the muon mass. In this case the momentum transferred from the initial muon to the $e\bar\nu$ system (the virtual neutrino momentum) can be both time--like and space--like. Since the path of integration over $k^2$ goes through a pole at $k^2=0$, it gives a divergent cross section. In the ideal case of large enough beams this divergence disappears if the finite width $\Gamma$ of the initial muon is taken into account. The obtained cross section corresponds to the flux of equivalent neutrino, which coincides with that of muon (with some energy distribution). In practice, the effect of final size of the muon beam reduces this cross section very strong, and the effect is hardly observable., Comment: 5 pages, no figures; Talk given at 3 Int. Conference on Physics Potential and Development of mumu Colliders, San Francisco, December 13-15, 1995

We discuss the main stages of a physical program for photon linear colliders. We consider the problems in electroweak theory, hadron physics, QCD, and nonlinear QED, as well as new particles and interactions, etc. The discussed stages constitute the parts of an entire ambitious program for linear colliders.

It seems to be very natural that whole program for constructing and exploring of linear colliders (including photon colliders as the substantial part) should be divided by stages according to the increasing beam energy. We discuss the main stages of this program and the set of physical problems for each stage photon colliders.

The main source of e + e − pair at μ + μ − collider is incoherent process μ + μ − → μ + μ − e + e − with cross section about. 10 mb (at muon energy 2 TeV). The corresponding distributions are discussed briefly. These pairs give the dangerous background. The coherent production of e + e − pairs here is negligibly small.

We use the invariance of physical picture under a change of Lagrangian, the reparametrization invariance in the space of Lagrangians and its particular case -- the rephrasing invariance, for analysis of the two-Higgs-doublet extension of the SM. We found that some parameters of theory like tan beta are reparametrization dependent and therefore cannot be fundamental. We use the Z2-symmetry of the Lagrangian, which prevents a phi_1 phi_2 transitions, and the different levels of its violation, soft and hard, to describe a physical content of the model. In general, the broken Z2-symmetry allows for a CP violation in the physical Higgs sector. We argue that the 2HDM with a soft breaking of Z2-symmetry is a natural model in the description of EWSB. To simplify an analysis we choose among different forms of Lagrangian describing the same physical reality a specific one, in which the vacuum expectation values of both Higgs fields are real. A possible CP violation in the Higgs sector is described by using a two-step procedure with the first step identical to a diagonalization of mass matrix for CP-even fields in the CP conserved case. We find very simple necessary and sufficient condition for a CP violation in the Higgs sector. We determine the range of parameters for which CP violation and Flavor Changing Neutral Current effects are naturally small,what corresponds to a small dimensionless mass parameter nu= Re m_{12}^2/(2v1v2). We discuss how for small nu some Higgs bosons can be heavy, with mass up to about 0.6 TeV, without violating of the unitarity constraints. We discuss main features of the large nu case, which corresponds for nu -> infty to a decoupling of heavy Higgs bosons., Comment: 27 pages, extended discussion, references added, one figure, Revtex4

We study possibilities to measure the triple anomalous W-boson couplings to photon in the $e\gamma\to W\nu$ process via its lepton decay channel (with the simplest signature). We found that in the study of the $W$ quadruple momentum $\lambda$ one can limit himself within a small region in phase space. A way to find this region is proposed. The obtained estimates for $\lambda$ at TESLA project are roughly twice better than anticipated for $e+e-$ mode. For $W$ anomalous magnetic momentum the discussed mode gives no improvements as compared $e+e-$ mode.

We describe the status of our effort to realize a first neutrino factory and the progress made in understanding the problems associated with the collection and cooling of muons towards that end. We summarize the physics that can be done with neutrino factories as well as with intense cold beams of muons. The physics potential of muon colliders is reviewed, both as Higgs Factories and compact high energy lepton colliders. The status and timescale of our research and development effort is reviewed as well as the latest designs in cooling channels including the promise of ring coolers in achieving longitudinal and transverse cooling simultaneously. We detail the efforts being made to mount an international cooling experiment to demonstrate the ionization cooling of muons., Comment: 112 pages, Large report

After operations at the LHC and e^+e^- Linear Colliders it may be found that a Standard-Model-like scenario is realized. In this scenario no new particle will be discovered, except a single Higgs boson having partial widths or coupling constants squared with fundamental particles close, within anticipated experimental uncertainty, to those of the SM. Experiments at a Photon Collider can resolve whether the SM model or e.g. the Two Higgs Doublet Model is realized in Nature. For the SM-like version of the 2HDM (II) we study the loop couplings of the Higgs boson with \gamma\gamma and Z \gamma, and also with gluons. The deviation of the two-photon width from its SM value is generally higher than the expected inaccuracy in the measurement of \Gamma_{\gamma \gamma} at a Photon Collider. The result is sensitive to the parameters of the Higgs self interaction., Comment: 9 pages, LaTeX, with figures

Subjects of discussion Different scenarios Higgs window to a New Physics Anomalies in the interactions of gauge and Higgs bosons Some problems with t-quarks and MSSM. Some problems in QCD and hadron physics. By-product: Production of axions, etc. from region of conversion e --> gamma., LaTeX 2e, 9 pages with 6 figures

Subjects of discussion 1. Different scenarios 2. Higgs window to a New Physics 3. Anomalies in the interactions of gauge and Higgs bosons 4. Some problems in QCD and hadron physics. 5. By-product: Production of axions, etc. from region of conversion e→γ.

After operations at the LHC and e^+e^- Linear Colliders it may be found that a Standard-Model-like scenario is realized. In this scenario no new particle will be discovered, except a single Higgs boson having partial widths or coupling constants with fundamental particles, whose squares are close, within anticipated experimental uncertainty, to those of the SM. Experiments at a Photon Collider can resolve whether the SM or e.g. the Two-Higgs-Doublet Model is realized in Nature. For the SM-like realizations of the 2HDM (II) we study the loop couplings of the Higgs boson with \gamma\gamma and Z \gamma, and also with gluons. The deviation of the two-photon width from its SM value is generally higher than the expected inaccuracy in the measurement of \Gamma_{\gamma \gamma} at a Photon Collider. The deviation is sensitive to the parameters of the Higgs self interaction., Comment: 8 pages, aipproc, including figures. Presented at 5th International Linear Collider Workshop (LCWS 2000), Fermilab, Batavia, Illinois, 24-28 Oct 2000, to appear in proceedings

The physical problems for the μp collider which can be constructed in one complex with μ+μ− machine are discussed. It is taken into account that this machine can operate only after basic μ+μ− collider and LHC.

We propose procedures for luminosity monitoring at {mu}p and {mu}{sup +}{mu}{sup -} colliders.

We discuss the potential of photon colliders in the discovery effects of New Physics Beyond the SM.

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($��\to ����_��$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)]., 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beams