multi-TeV Collider Research Articles

The new physics case for beam-dump experiments with accelerated muon beams

As the field examines a future muon collider as a possible successor to the LHC, we must consider how to fully utilize not only the high-energy particle collisions, but also any lower-energy staging facilities necessary in the R&D process. An economical and efficient possibility is to use the accelerated muon beam from either the full experiment or from cooling and acceleration tests in beam-dump experiments. Beam-dump experiments are complementary to the main collider as they achieve sensitivity to very small couplings with minimal instrumentation. We demonstrate the utility of muon beam-dump experiments for new physics searches at energies from 10 GeV to 5 TeV. We find that, even at low energies like those accessible at staging or demonstrator facilities, it is possible to probe new regions of parameter space for a variety of generic BSM models, including muonphilic, leptophilic, Lμ − Lτ, and dark photon scenarios. Such experiments could therefore provide opportunities for discovery of new physics well before the completion of the full multi-TeV collider.

Low emittance muon accelerator studies with production from positrons on target

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]

The experimental program for high pressure gas filled radio frequency cavities for muon cooling channels

An intense beam of muons is needed to provide a luminosity on the order of 1034 cm−2s−1 for a multi-TeV collider. Because muons produced by colliding a multi-MW proton beam with a target made of carbon or mercury have a large phase space, significant six dimensional cooling is required. Through ionization cooling—the only cooling method that works within the lifetime of the muon—and emittance exchange, the desired emittances for a Higgs Factory or higher energy collider are attainable. A cooling channel utilizing gas filled radio frequency cavities has been designed to deliver the requisite cool muon beam. Technology development of these RF cavities has progressed from breakdown studies, through beam tests, to dielectric loaded and reentrant cavity designs. The results of these experiments are summarized.

Static beam-based alignment for the Ring-To-Main-Linac of the Compact Linear Collider

The Compact Linear Collider (CLIC) is a future multi-TeV collider for the post-Large Hadron Collider era. It features high-gradient acceleration and ultra-low emittance to achieve its ambitious goals of high collision energy and peak luminosity. Beam-based alignment (BBA) techniques are mandatory for CLIC to preserve the ultra-low emittances from the damping rings to the interaction point. In this paper, a detailed study of BBA techniques has been carried out for the entire 27 km long ``Ring-To-Main-Linac'' (RTML) section of the CLIC, to correct realistic static errors such as element position offsets, angle, magnetic strength and dynamic magnetic centre shifts. The correction strategy is proved to be very effective and leads to a relaxation of the pre-alignment tolerances for the component installation in the tunnel. This is the first time such a large scale and complex lattice has been corrected to match the design budgets. The techniques proposed could be applied to similarly sized facilities, such as the International Linear Collider, where a similar RTML section is used, or free-electron lasers, which, being equipped with linacs and bunch compressors, present challenges similar to those of the CLIC RTML. Moreover, a new technique is investigated for the emittance tuning procedure: the direct measurement of the interactions between the beams and a set of a few consecutive laser wires. The speed of this technique can be faster comparing to the traditional techniques based on emittance reconstructed from beam size measurements at several positions.

Study of the production of a newZ′boson and its decay into Majorana neutrinos inppcollisions ats=14 TeVand ine+e−collisions ats=3 TeV

In the theoretical framework of the left-right symmetric model with the seesaw mechanism, we first report on the possibility of observing the decay of a new neutral gauge boson ${Z}^{\ensuremath{'}}$ into a pair of heavy right-handed Majorana neutrinos ${N}_{e}$ at the future CERN LHC, in the ATLAS detector. We then study the ${Z}^{\ensuremath{'}}\ensuremath{\rightarrow}{N}_{e}{N}_{e}$ process at a possible next-generation ${e}^{+}{e}^{\ensuremath{-}}$ multi-TeV collider, such as CLIC, and we show that an accurate measurement of ${m}_{{Z}^{\ensuremath{'}}}$ and ${m}_{{N}_{e}}$ can be performed with a resonance scan.

HIGGS FACTORY μ+μ- COLLIDER AND THE SCALAR ELECTROWEAK SECTOR

We describe the concept of a Higgs factory μ+μ- collider and the process that will measure the particle width, particle spectrum, and normal and rare decay branching fractions. Such a factory would be able to distinguish between the standard, minimal supersymmetric, and nonminimal supersymmetric models. A μ+μ- collider with appropriate luminosity and energy spread will provide the Higgs factory. We describe the current design of such a collider and the higher energy multi-TeV collider development as well.

Comparison of high-dose dosimetry systems for radiation damage studies in collider detectors and accelerators

Measurements of absorbed dose in accelerator tunnels around primary beam areas are carried out on a routine basis at CERN. Dosimetric surveillance of high-energy particle accelerators has a great importance for the assessment of the radiation induced damage to materials and components used in high-level radiation areas. Standard dosimeters used at CERN for this purpose are polymer-alanine dosimeters (PAD) and radiophotoluminescent glass dosimeters (RPL). Ethanol-chlorobenzene dosimeters (ECB) for high-dose dosimetry, developed at the Ruder Boskovic Institute (RBI), have several interesting properties making their use in future multi-TeV colliders and detectors promising. These and RPL dosimeters were compared using the CERN alanine dosimetry as the reference system and 60Co gamma rays as the reference radiation. A very good agreement between the ECB and PAD was obtained for 60Co gamma irradiation whereas RPL overestimated the dose by about 15%. In mixed accelerator radiation fields the combination of the three dosimeters opens the possibility to estimate the total dose and the quality of the principal radiations contributing to the total radiation field.

Consequences of new-heavy-particle exchange in e+e--->W+W-

In this paper we present an analysis of the contribution of new possible neutral current and heavy neutrino exchange for the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{W}^{+}{W}^{\ensuremath{-}}$. The unitarity behavior is discussed for some extended models. Multi-TeV colliders are shown to be sensitive to new heavy neutrino masses at energies well below their mass thresholds

Superheavy toponium production at multi-TeV colliders

We discuss the possible existence of the superheavy toponium bound via Higgs-boson exchange. The production cross section of such a superheavy toponium becomes rather large in multi-TeV regions owing to the strong Higgs-top quark interaction.

LHC, SSC and the universe

The geometric mean of the Planck mass and the 2.7 K background temperature — numerically equal to about a TeV — is the maximum mass that any cosmologically stable perturbatively coupled elementary particle can have or else the density of the universe exceeds its critical value. Thus, the TeV scale is cosmologically significant for reasons unrelated to the scale of electroweak symmetry breaking; it would persist even if the masses of the W and Z vanished. This implies that the TeV scale emerges cosmologically in many extensions of the standard model involving new particles and forces. We derive, for example, upper limits of order of a few TeV to the mass of the lightest supersymmetric particle LSP as well as to the masses of new U′(1) gauge bosons and their associated stable electroweak singlets that can occur in superstring theories. Any dark matter candidate that is perturbatively coupled must also weigh less than a few TeV. Thus, cosmology implies that all these particles should be accessible to multi-TeV colliders. In particular, the dominant dark component of the universe and its charged electroweak partners could be discovered in such machines. These ideas suggest a cosmological argument for a desert commencing near a TeV. They have implications for unified and superstring models. For example, new U′(1)'s accompanied by stable electroweak singlets have to be lighter than a few TeV; they therefore must commute with family rotations or else be in conflict with the K LK S mass difference.

Ultraheavy quarkonium and its production in multi-TeV hadron colliders

Based on the standard model with two Higgs-doublets, we study physics of ultraheavy quarkonia which are composed of superheavy (such as 4-th generation) quarks. Owing to the strong Higgs-boson exchange force over the gluon exchange force, the situation of the mass levels of such quarkonia becomes drastically different from the ordinary qaurkonia like\(c\bar c\) or\(b\bar b\). The hyperfine splitting becomes larger than the fine splitting. The production rate of such quarkonia increases largely in multi-TeV colliders. Feasibility for observing such quarkonia is discussed.

Production of ultraheavyS-state bound statesη Q (0− +) andψ(1−−) in multi-TeV collider energies

We study the Higgs-boson exchange interaction in ultraheavys-state bound statesηQ(0− +) and ψ(1−−) composed of ultraheavy quarksQ. Owing to the strong Higgs-ultraheavy quark interaction, the production of such bound states is hugely enhanced in multi-TeV collider energies over the case of bound states via gluon exchange alone.

Signatures for isoscalar weak vector bosons at pp and p [formula omitted] colliders

In a wide class of composite models of quarks, leptons and W-bosons the existence of isoscalar weak vector bosons Y or Y L is predicted. They either couple to the weak hypercharge current j μ Y or its left-handed part j Y μL = j Y L and have a mass in the few hundred GeV range. The signatures of such particles at future hadron-hadron colliders is studied by means of an effective lagrangian incorporating vector dominance. Quantities relevant for detecting and studying isoscalar weak vector bosons turn out to be sensitive to the mixing strength λ Y of the Y- or Y L-boson with the photon. The Y or Y L are expected to be produced abundantly at multi-TeV colliders. The Tevatron collider will be able to see a Y L-boson if its mass is ⩽400 GeV.

Heavy-lepton production via vector-boson fusion.

We investigate the production of a possible pair of sequential heavy charged leptons (M-italic/sub L-italic/--200--800 GeV) at p-italicp-italic multi-TeV colliders via vector-boson fusion. The results are compared with the usual Drell-Yan mechanism and with the two-photon process. For very heavy leptons the fusion of W-italic's provides a contribution that is, at high energies, larger than the Drell-Yan mechanism.