The present research in particle physics has been progressing very quickly in recent decades thanks to the effort of a large and motivated community of experimentalists and theorists. According to an oversimplified scheme, the experimental effort goes along two main lines which we could broadly identify as the 'high-intensity' (or 'high-luminosity') and the 'high-energy' roads. The former includes high-precision and relatively low-energy experiments, aiming at pinning down tiny effects related to the exchange of virtual particles of new physics and giving rise to departures from the predictions of the Standard Model of particles and interactions (SM). We can mention, as not exhaustive examples, neutrino experiments and measurements of CP violation and flavor changing neutral currents (FCNC) in the quark sector and analogous lepton flavor violation (LFV) in the lepton sector. The other line of research has the scope of extending the energy frontier of the collisions, entering the 'terra incognita' of particle physics thanks to the availability of more and more powerful particle accelerators and of complex and performing experimental apparatus, able to stand extremely high collision rates and doses. The operation in recent years of large accelerators such as the SPS Collider and the LEP at CERN, the Tevatron at FERMILAB, and HERA at DESY has allowed particle physicists to gather valuable data, leading to a profound understanding of the Standard Model and a consequent major achievement in our endeavor to understand fundamental interactions and elementary particles at the shortest distances. Namely, we now know that the Standard Model of particle physics correctly describes such fundamental physics up to energies of O(100 GeV).

As deep and outstanding as this achievement may be, we still have good reasons to claim that the Standard Model represents only a layer in our knowledge of fundamental interactions, i.e. new physics has to show up at energies larger than the 100 GeV level. There is both observational and theoretical support for such an important claim. On the observational side, the non-vanishing neutrino masses, the presence of a large amount of non-baryonic Dark Matter and the need to have an efficient dynamical mechanism to give rise to the cosmic matter–antimatter asymmetry (baryogenesis) call for extensions of the Standard Model with new particles and interactions. Theoretically, we blame the SM for not offering an answer to questions that we usually consider as fundamental: (i) the SM fails to give a rationale for the puzzling spectrum of fermion masses and mixings, (ii) it does not achieve a true unification of fundamental interactions since it still has three gauge coupling constants to account for the electroweak and strong interactions and (iii) in the SM the spontaneous breaking of the electroweak symmetry is achieved through the introduction of a fundamental scalar, the Higgs boson, whose mass is not protected by any symmetry against huge radiative corrections leading to a destabilization of the energy scale where the electroweak breaking has to occur (gauge hierarchy problem). This third deficiency of the SM actually provides the main motivation for our firm belief that new physics has to show up at a scale related to the electroweak symmetry breaking, i.e. in the TeV range. Indeed, no matter how one chooses to provide an ultraviolet completion of the SM to allow for the above-mentioned stabilization (dynamical electroweak symmetry breaking à la Technicolor, low-energy supersymmetry, large extra dimensions, 'little Higgs solution', etc), one unavoidably ends up with the presence of new physics signatures at the TeV scale. In some cases, the new physics at the electroweak scale may entail very interesting candidates for Dark Matter or may provide a nice unification of the electroweak and strong gauge couplings at some larger energy scales.

In this spirit, there is general consensus that the present and the next generations of high-energy, high-intensity (luminosity) machines will bring new fundamental discoveries, since the new physics outlined above is expected to be 'just beyond' the energy scale explored so far. We talk therefore of 'physics at the TeV scale', the energy domain that will be soon explored by the proton LHC machine at CERN, and later on by the electron colliders ILC and CLIC. The latter are expected to be the first machines to be conceived, designed, funded and operated as a genuinely worldwide effort. Finally, special attention has to be devoted to the detectors employed with these accelerators. As an example, the requirements on particle detection and on the measurement of their kinematical quantities at the LHC have pushed the various detector techniques to their limits, calling for new solutions and bringing forward a remarkable development of the field.

This invited focus issue of New Journal of Physics aims to provide a survey of the field of 'physics at the TeV scale' courtesy of selected papers from leading experimentalists and theorists directly involved in key aspects of the research. On the eve of the LHC start-up, we hope that this collection will prove to be a useful resource in the hands of a diversified scientific community which is tackling the difficult task of finding the first traces of a new physics that particle physicists have been (desperately) seeking for more than three decades.

Focus on Particle Physics at the TeV Scale Contents

Is SUSY natural?
Keith R Dienes, Michael Lennek, David Sénéchal and Vaibhav Wasnik

Energy measurement at the TeV scale
Richard Wigmans

Innovations in ILC detector design using a particle flow algorithm approach
Stephen R Magill

Tracking at LHC
F Ragusa and L Rolandi

The Large Hadron Collider
Lyndon Evans

Triggering at high luminosity colliders
Hans Peter Beck

TeV physics and the Planck scale
Vernon Barger, Paul Langacker and Gabe Shaughnessy

Physics during the first two years of the LHC
Fabiola Gianotti

Antonio Ereditato, University of Bern, Switzerland
Takaaki Kajita, University of Tokyo, Japan
Antonio Masiero, Università degli Studi di Padova, Italy