International Journal of Modern Physics A

Ten years after its discovery at the Tevatron collider, we still know little about the top quark. Its large mass suggests it may play a key role in the mechanism of Electroweak Symmetry Breaking (EWSB), or open a window of sensitivity to new physics related to EWSB and preferentially coupled to it. To determine whether this is the case, precision measurements of top quark properties are necessary. The high statistics samples being collected by the Tevatron experiments during Run II start to incisively probe the top quark sector. This report summarizes the experimental status of the top quark, focusing in particular on the recent measurements from the Tevatron Run II.

The measurements of electroweak sector of the Standard Model are presented, including most recent results from LEP, Tevatron and HERA colliders. The robustness of the Standard Model is illustrated with the precision measurements, the electroweak fits and the comparisons to the results obtained from low energy experiments. The status of the measurements of the W boson properties and rare production processes involving weak bosons at colliders is examined, together with the measurements of the electroweak parameters in ep collisions.

The present status of searches for the Higgs boson(s) and new phenomena is reviewed. The focus is on analyses and results from the current runs of the HERA and Tevatron experiments. The LEP experiments have released their final combined MSSM Higgs results for this conference. Also included are results from sensitivity studies of the LHC experiments and lepton flavour violating searches from the B factories, KEKB and PEP-II.

Recent progress in both the experimental and theoretical explorations of electroweak symmetry breaking is surveyed.

The hierarchy problem is one of the main motivations for building the CERN Large Hadron Collider (LHC). The prospects for the ATLAS and CMS experiments to understand this problem are discussed, with emphasis on early studies with the first LHC data. The longer-term potential for constraining the parameters of the underlying new theory is also addressed.

This paper is a very short report on the status of the Large Hadron Collider(LHC) and its four experiments at the end of August 2005.

Type I string theory provides a D-brane world description of our universe and leads to two new scenaria for physics beyond the Standard Model: low string scale and split supersymmetry. Lowering the string scale in the TeV region provides a theoretical framework for solving the mass hierarchy problem and unifying all interactions. The apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the submillimeter region, and transverse to a braneworld where we must be confined. I review the main properties of this scenario and its implications for observations at both particle colliders, and in non-accelerator gravity experiments. I also present a concrete realization of split supersymmetry which guarantees gauge coupling unification at the conventional scale M_GUT ≃ 2 × 10¹⁶GeV.

Experimental status of CP violation in B mesons is summarized and the measurements are compared with the Standard Model expectations.

Measurements of the angles and sides of the unitarity triangle and of the rates of rare B meson decays are crucial for the precise determination of Standard Model parameters and are sensitive to the presence of new physics particles in the loop diagrams. In this paper the recent measurements performed in this area by BABAR and Belle will be presented. The direct measurement of the angle α is for the first time as precise as the indirect determination. The precision of the |V_ub| determination has improved significantly with respect to previous measurement. New limits on B → τν decays are presented, as well as updated measurements on b → s radiative transitions and a new observation of b → dγ transition made by Belle.

The charm quark has unique properties that make it a very important probe of many facets of the Standard Model. New experimental information on charm decays is becoming available from dedicated experiments at charm factories, and through charm physics programs at the b-factories and hadron machines. In parallel, theorists are working on matrix element calculations based on unquenched lattice QCD, that can be validated by experimental measurements and affect our ultimate knowledge of the quark mixing parameters. Recent predictions are compared with corresponding experimental data and good agreement is found. Charm decays can also provide unique new physics signatures; the status of present searches is reviewed. Finally, charm data relevant for improving beauty decay measurements are presented.

Recent experimental results on quarkonium physics are reviewed. In particular, the new observed particles since last one or two years, such as X(1835), X(3872), X(3940), Y(3940) and Y(4260) are discussed, the latest data on double charmonium production, heavy hadron spectroscopy and quarkonia decays are presented.

I summarize the theoretical progress in the determination of the CKM elements since Lepton-Photon 2003 and present the status of the elements and parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. One finds |V_us| = 0.2227 ± 0.0017 from K and τ decays and |V_cb| = (41.6 ± 0.5) · 10^-3 from inclusive semileptonic B decays. The unitarity triangle can now be determined from tree-level quantities alone and the result agrees well with the global fit including flavour-changing neutral current (FCNC) processes, which are sensitive to new physics. From the global fit one finds the three CKM angles θ₁₂ = 12.9° ± 0.1°, θ₂₃ = 2.38° ± 0.03° and θ₁₃ = 0.223° ± 0.007° in the standard PDG convention. The CP phase equals at 1σ CL and at 2σ CL. A major progress are first results from fully unquenched lattice QCD computations for the hadronic quantities entering the UT fit. I further present the calculation of three-loop QCD corrections to the charm contribution in decays, which removes the last relevant theoretical uncertainty from the system. Finally I discuss mixing-induced CP asymmetries in penguin decays, whose naive average is below its Standard Model value by 3σ.

We review the status of rare decays and CP violation in extensions of the Standard Model. We analyze the determination of the unitarity triangle and the model-independent constraints on new physics that can be derived from this analysis. We find stringent bounds on new contributions to and mixing, pointing either to models of minimal flavour violation or to models with new sources of flavour and CP violation in b → s transitions. We discuss the status of the universal unitarity triangle in minimal flavour violation, and study rare decays in this class of models. We then turn to supersymmetric models with nontrivial mixing between second and third generation squarks, discuss the present constraints on this mixing and analyze the possible effects on CP violation in b → s nonleptonic decays and on mixing. We conclude presenting an outlook on Lepton-Photon 2009.

Data from the first three years of running at RHIC are reviewed and put into context with data obtained previously at the AGS and SPS and with the physics question of creation of a quark-gluon plasma in high energy heavy ion collisions. Also some very recent and still preliminary data from run are included.

The status of the search for pentaquark baryon states is reviewed in light of new results from the first two dedicated experiments from CLAS at Jefferson Lab and of new analyses from several labs on the Θ⁺(1540). Evidence for and against the heavier pentaquark states, the Ξ(1862) and the observed at CERN and at HERA, respectively, are also discussed. I conclude that the evidence against the latter two heavier pentaquark baryons is rapidly increasing making their existence highly questionable. I also conclude that the evidence for the Θ⁺ state has significantly eroded with the recent CLAS results, but still leaves room for a state with an intrinsic width of Γ < 0.5 MeV. New evidence in support of a low mass pentaquark state from various experiments will be discussed as well.

A brief review of key recent developments and ongoing projects in perturbative QCD theory, with emphasis on conceptual advances that have the potential for impact on LHC studies. Topics covered include: twistors and new recursive calculational techniques; automation of one-loop predictions; developments concerning NNLO calculations; the status of Monte Carlo event generators and progress in matching to fixed order; analytical resummation including the push to NNLL, automation and gap between jets processes; and progress in the understanding of saturation at small x.

QCD is the accepted (that is, the effective) theory of the strong interaction; studies at colliders are no longer designed to establish this. Such studies can now be divided into two categories. The first involves the identification of observables which can be both measured and predicted at the level of a few percent. Such studies parallel those of the electroweak sector over the past fifteen years, and deviations from expectations would be a sign of new physics. These observables provide a firm "place to stand" from which to extend our understanding. This links to the second category of study, where one deliberately moves to regions in which the usual theoretical tools fail; here new approximations in QCD are developed to increase our portfolio of understood processes, and hence our sensitivity to new physics. Recent progress in both these aspects of QCD at colliders is discussed.

The idea of diffractive processes with a hard scale involved, to resolve the underlying parton dynamics, was published 1985 and experimentally verified 1988. Today hard diffraction is an active research field with high-quality data and new theoretical models. The trend from Regge-based pomeron models to QCD-based parton level models has given insights on QCD dynamics involving perturbative gluon exchange mechanisms, including the predicted BFKL-dynamics, as well as novel ideas on non-perturbative colour fields and their interactions. Extrapolations to the LHC include the interesting possibility of diffractive Higgs production.

We first deal with the muon anomalous magnetic moment which is found to differ from the standard model prediction by 2.7 σ. A new proposal will aim at reducing the error by a factor 2. The main part of the paper then deals with the spin structure of the nucleon which can be studied in terms of quark and gluon helicity distributions, quark transversity distributions and generalized parton distributions. The main recent results are first indications that the total gluon spin in the nucleon might be small and a first measurement of the Collins fragmentation function which is needed to extract transversity distributions from semi-inclusive DIS data.

This talk begins with some history and basic facts about string theory and its connections with strong interactions. Comparisons of stacks of Dirichlet branes with curved backgrounds produced by them are used to motivate the AdS/CFT correspondence between superconformal gauge theory and string theory on a product of Anti-de Sitter space and a compact manifold. The ensuing duality between semi-classical spinning strings and long gauge theory operators is briefly reviewed. Strongly coupled thermal SYM theory is explored via a black hole in 5-dimensional AdS space, which leads to explicit results for its entropy and shear viscosity. A conjectured universal lower bound on the viscosity to entropy density ratio, and its possible relation to recent results from RHIC, are discussed. Finally, some available results on string duals of confining gauge theories are briefly reviewed.

Recent results from the atmospheric neutrino measurements are discussed. The best constraint oscillation parameters of Δm²=2.5×10^-3eV² and sin²2θ=1.0 was obtained by a new treatment of the atmospheric neutrino data. An evidence for the ν_τ appearance in the atmospheric neutrino events was shown by statistical methods. The long baseline oscillation experiment using man-made neutrinos has confirmed the atmospheric neutrino oscillation and obtained consistent parameter regions. The prospects for future accelerator experiments are presented.

Over the last several years, experiments have conclusively demonstrated that neutrinos are massive and that they mix. There is now direct evidence for ν_es from the Sun transforming into other active flavors while en route to the Earth. The disappearance of reactor , predicted under the assumption of neutrino oscillation, has also been observed. In this paper, recent results from solar and reactor neutrino experiments and their implications are reviewed. In addition, some of the future experimental endeavors in solar and reactor neutrinos are presented.

Neutrino oscillation searches at short baseline (defined as ≲ 1 km) have investigated oscillations with Δm² ≳ 0.1eV². One positive signal, from the LSND collaboration, exists and is being tested by the MiniBooNE experiment. Neutrino cross-section measurements are being made, which will be important for reducing systematic errors in present and future oscillation measurements.

The discovery by many different experiments of the flavour oscillation of neutrinos from different sources proved clearly that neutrinos have non-vanishing masses in contrast to their current description within the Standard Model of particle physics. However, the neutrino mass scale, which is – in addition to particle physics – very important for cosmology and astrophysics, cannot be resolved by oscillation experiments. Although there are a few ways to determine the absolute neutrino mass scale, the only model-independent method is the investigation of the electron energy spectrum of a β decay near its endpoint. The tritium β decay experiments at Mainz and Troitsk using tritium have recently been finished and have given upper limits on the neutrino mass scale of about 2 eV/c². The bolometric experiments using ¹⁸⁷Re have finished the first round of prototype experiments yielding a sensitivity on the neutrino mass of 15 eV/c². The new Karlsruhe Tritium Neutrino Experiment (KATRIN) will enhance the sensitivity on the neutrino mass by an ultra-precise measurement of the tritium β decay spectrum by another order of magnitude down to 0.2 eV/c² by using a very strong windowless gaseous molecular tritium source and a huge ultra-high resolution electrostatic spectrometer of MAC-E-Filter type. The recent achievements in test experiments show, that this very challenging experiment is feasible.

The present status of experiments searching for neutrinoless double-beta decay (ββ(0ν)) is reviewed and the results of the most sensitive experiments discussed. Phenomenological aspects of ββ(0ν) are introduced and most relevant aspects for neutrino physics discussed. Given the observation of neutrino oscillations and the present knowledge of neutrino masses and mixing parameters, a possibility to observe ββ(0ν) at a neutrino mass scale m_ν ≈10-50 meV could actually exist. The achievement of the required experimental sensitivity is a real challenge faced by a number of new proposed projects. A review of the most relevant of them is given.

The present status of neutrino oscillation parameters are summarised. The sensitivity of the future planned and proposed experiments are discussed.

The Neutrino Telescopes NT-200 in Lake Baikal, Russia and AMANDA at the South Pole, Antarctica have now opened the field of High Energy Neutrino Astronomy. Several other Neutrino telescopes are in the process of being constructed or very near realization. Several thousands of atmospheric neutrinos have been observed with energies up to several 100 TeV but so far no evidence for extraterrestrial neutrinos has been found.

More than 90% of matter in the Universe could be composed of heavy particles, which were non-relativistic, or 'cold', when they froze-out from the primordial soup. I will review current searches for these hypothetical particles, both via interactions with nuclei in deep underground detectors, and via the observation of their annihilation products in the Sun, galactic halo and galactic center.

The present status of our knowledge about the dark matter and dark energy is reviewed. Particular emphasis is put on the bounds on the content of cold and hot dark matter from cosmological observations are discussed in some detail. I also review current bounds on the physical properties of dark energy, mainly its equation of state and effective speed of sound.

One of the most striking astrophysical phenomena today is the existence of cosmic ray particles with energies in excess of 10²⁰ eV. While their presence has been confirmed by a number of experiments, it is not clear where and how these particles are accelerated to these energies and how they travel astronomical distances without substantial energy loss. We are entering an exciting new era in cosmic ray physics, with instruments now producing data of unprecedented quality and quantity to tackle the many open questions. This paper reviews the current experimental status of cosmic ray physics and summarizes recent results on the energy spectrum and arrival directions of ultra-high-energy cosmic rays.

Recent results on the particle detector R&D for new accelerators are reviewed. Different approaches for the muon systems, hadronic and electromagnetic calorimeters, particle identification devices, and central trackers are discussed. Main emphasis is made on the detectors for the International Linear Collider and Super B-factory. A detailed description of a novel photodetector, a so called Silicon Photomultiplier, and its applications in scintillator detectors is presented.

This article summarizes the physics at future linear colliders. It will be shown that in all studied physics scenarios a 1 TeV linear collider in addition to the LHC will enhance our knowledge significantly and helps to reconstruct the model of new physics nature has chosen.

Research & development for future accelerators are reviewed. First, I discuss colliding hadron beams, in particular upgrades to the Large Hadron Collider (LHC). This is followed by an overview of new concepts and technologies for lepton ring colliders, with examples taken from VEPP-2000, DAFNE-2, and Super-KEKB. I then turn to recent progress and studies for the multi-TeV Compact Linear Collider (CLIC). Some generic linear-collider research, centered at the KEK Accelerator Test Facility, is described next. Subsequently, I survey the neutrino factory R&D performed in the framework of the US feasibility study IIa, and I also comment on a novel scheme for producing monochromatic neutrinos from an electron-capture beta beam. Finally, I present innovative ideas for a high-energy muon collider and I consider recent experimental progress on laser and plasma acceleration.

Lepton Photon 2005 told the saga of the Standard Model which is still exhilarating because it leaves all questions of consequence unanswered.

Our understanding of ordinary matter is remarkably accurate and complete, but it is based on principles that are very strange and unfamiliar. As I'll explain, we've come to understand matter to be a Music of the Void, in a remarkably literal sense. Just as we physicists finalized that wonderful understanding, towards the end of the twentieth century, astronomers gave us back our humility, by informing us that ordinary matter – what we, and chemists and biologists, and astronomers themselves, have been studying all these centuries constitutes only about 5% of the mass of the universe as a whole. I'll describe some of our promising attempts to rise to this challenge by improving, rather than merely complicating, our description of the world.