First Look at the Physics Case of TLEP (1308.6176v3)

Abstract: The discovery by the ATLAS and CMS experiments of a new boson with mass around 125 GeV and with measured properties compatible with those of a Standard-Model Higgs boson, coupled with the absence of discoveries of phenomena beyond the Standard Model at the TeV scale, has triggered interest in ideas for future Higgs factories. A new circular e+e- collider hosted in a 80 to 100 km tunnel, TLEP, is among the most attractive solutions proposed so far. It has a clean experimental environment, produces high luminosity for top-quark, Higgs boson, W and Z studies, accommodates multiple detectors, and can reach energies up to the t-tbar threshold and beyond. It will enable measurements of the Higgs boson properties and of Electroweak Symmetry-Breaking (EWSB) parameters with unequalled precision, offering exploration of physics beyond the Standard Model in the multi-TeV range. Moreover, being the natural precursor of the VHE-LHC, a 100 TeV hadron machine in the same tunnel, it builds up a long-term vision for particle physics. Altogether, the combination of TLEP and the VHE-LHC offers, for a great cost effectiveness, the best precision and the best search reach of all options presently on the market. This paper presents a first appraisal of the salient features of the TLEP physics potential, to serve as a baseline for a more extensive design study.

• The paper establishes TLEP's potential as a high-luminosity Higgs factory achieving per-mil precision in measuring electroweak parameters.
• It details a methodology that exploits multiple collision energies from the Z pole to the top-antitop threshold, ensuring cleaner signals with reduced background effects.
• The analysis outlines a future integration with VHE-LHC to probe multi-TeV energy scales and uncover physics beyond the Standard Model.

Insightful Overview of the TLEP Physics Case

The document titled "First Look at the Physics Case of TLEP" evaluates the scientific potential of a proposed new circular electron-positron collider, the TLEP, envisaged to be constructed in an 80 to 100 km tunnel. This initiative reflects the physics community's ongoing interest in facilitating in-depth studies of the Higgs boson properties through high precision experiments, building upon the knowledge acquired from the ATLAS and CMS experiments at the LHC. The primary objective of TLEP, as discussed in the paper, is to function as a Higgs factory offering substantial statistical data collections under conditions less susceptible to hadronic backgrounds and beamstrahlung effects customary to linear colliders.

Key Technical and Experimental Features

The paper underscores TLEP's capability to offer high luminosity collisions at multiple interaction points over a broad spectrum of center-of-mass energies, ranging from the Z pole to beyond the top-antitop threshold. The collider is designed to support studies of the Higgs boson, top-quark, W and Z bosons, thus enabling a robust exploration of electroweak symmetry breaking parameters. The physics goals involve precision measurements that could translate into sensitivity for beyond Standard Model (BSM) physics at multi-TeV energy scales. The pivotal distinguishing feature is its long-term vision by accommodating the Very High Energy LHC (VHE-LHC), a subsequent hadron collider capable of reaching energies up to 100 TeV, in the same infrastructure.

Salient Physics Improvements and Implications

The technical advancements underlying TLEP imply a transformative leap in precision measurements of fundamental parameters such as the Higgs boson couplings, W mass, Z boson width, and electroweak mixing angles. These enhancements stem largely from the collider's high luminosity and clean experimental environment. The document anticipates achieving a per-mil level precision in measurements, which is necessary to discern potential new physics signals that may perturb the Higgs boson coupling predictions and deviate electroweak precision observables slightly from standard theory expectations.

From a theoretical perspective, these refinements in measurements offer a unique opportunity to verify or challenge the completeness of the Standard Model, addressing current anomalies and paving pathways towards novel theoretical constructs that align or expand beyond present paradigms. Furthermore, TLEP's data would provide complementary insights alongside the high-energy discoveries anticipated from LHC and its successors, balancing the collider physics quest between precision low-energy probes and brute force discovery reach at unprecedented scales.

Speculative Future Developments

Looking ahead, the coupling of TLEP with VHE-LHC outlines a promising and versatile road map for particle physics in the mid 21st century. While TLEP offers a bridge for high-precision studies, the VHE-LHC component can potentially unlock new territories by probing energy scales unreachable by current accelerators, thus opening the prospect for direct detection of new physics candidates. Given these prospects, the FCC (Future Circular Collider) vision, incorporating TLEP and VHE-LHC, could serve as a cornerstone for future collider experiments, enhancing both precision and discovery science realms, reflecting its cost-effectiveness and alignment with strategic scientific goals on the timeline stretching beyond 2050.

In conclusion, the paper cogently conveys TLEP's potential not only as a powerful Higgs factory but also as a catalyst for future technological advancements and discoveries within and beyond the present scope of high-energy particle physics.