Joseph Lykken

A systematic study is made of theories in which supergravity is spontaneously broken in a "hidden" sector of superfields that interact with ordinary matter only through supergravity. General rules are given for calculating the low-energy effective potential in such theories. This potential is given as the sum of ordinary supersymmetric terms involving a low-energy effective superpotential whose mass terms arise from integrating out the heavy particles associated with grand unification, plus supersymmetry-breaking terms that depend on the details of the hidden sector and the K\"ahler potential only through the values of four small complex mass parameters. The result is not the same as would be obtained by ignoring grand unification and inserting small mass parameters into the superpotential from the beginning. The general results are applied to a class of models with a pair of Higgs doublets.

We consider the novel Kaluza-Klein (KK) scenario where gravity propagates in the $4+n$ dimensional bulk of spacetime, while gauge and matter fields are confined to the 3+1 dimensional world-volume of a brane configuration. For simplicity we assume compactification of the extra $n$ dimensions on a torus with a common scale $R$, and identify the massive KK states in the four-dimensional spacetime. For a given KK level $\vec{n}$ there are one spin-2 state, $(n-1)$ spin-1 states and $n(n-1)/2$ spin-0 states, all mass-degenerate. We construct the effective interactions between these KK states and ordinary matter fields (fermions, gauge bosons and scalars). We find that the spin-1 states decouple and that the spin-0 states only couple through the dilaton mode. We then derive the interacting Lagrangian for the KK states and Standard Model fields, and present the complete Feynman rules. We discuss some low energy phenomenology for these new interactions for the case when 1/R is small compared to the electroweak scale, and the ultraviolet cutoff of the effective KK theory is on the order of 1 TeV.

Recent developments in string duality suggest that the string scale may not be irrevocably tied to the Planck scale. Two explicit but unrealistic examples are described where the ratio of the string scale to the Planck scale is arbitrarily small. Solutions that are more realistic may exist in the intermediate coupling or "truly strong coupling" region of the heterotic string. Weak scale superstrings have dramatic experimental consequences for both collider physics and cosmology.

After an introduction recalling the theoretical motivation for low energy (100 GeV to TeV scale) supersymmetry, this review describes the theory and experimental implications of the soft supersymmetry-breaking Lagrangian of the general minimal supersymmetric standard model (MSSM). Extensions to include neutrino masses and nonminimal theories are also discussed. Topics covered include models of supersymmetry breaking, phenomenological constraints from electroweak symmetry breaking, flavor/CP violation, collider searches, and cosmological constraints including dark matter and implications for baryogenesis and inflation.

The Supersymmetry Les Houches Accord (SLHA) provides a universal set of conventions for conveying spectral and decay information for supersymmetry analysis problems in high energy physics. Here, we propose extensions of the conventions of the first SLHA to include various generalisations: the minimal supersymmetric standard model with violation of CP, R-parity, and flavour, as well as the simplest next-to-minimal model.

MAGIS-100 is a next-generation quantum sensor under construction at Fermilab that aims to explore fundamental physics with atom interferometry over a 100 m baseline. This novel detector will search for ultralight dark matter, test quantum mechanics in new regimes, and serve as a technology pathfinder for future gravitational wave detectors in a previously unexplored frequency band. It combines techniques demonstrated in state-of-the-art 10-meter-scale atom interferometers with the latest technological advances of the world's best atomic clocks. MAGIS-100 will provide a development platform for a future kilometer-scale detector that would be sufficiently sensitive to detect gravitational waves from known sources. Here we present the science case for the MAGIS concept, review the operating principles of the detector, describe the instrument design, and study the detector systematics.

Abstract Numerous astrophysical and cosmological observations are best explained by the existence of dark matter, a mass density which interacts only very weakly with visible, baryonic matter. Searching for the extremely weak signals produced by this dark matter strongly motivate the development of new, ultra-sensitive detector technologies. Paradigmatic advances in the control and readout of massive mechanical systems, in both the classical and quantum regimes, have enabled unprecedented levels of sensitivity. In this white paper, we outline recent ideas in the potential use of a range of solid-state mechanical sensing technologies to aid in the search for dark matter in a number of energy scales and with a variety of coupling mechanisms.

The holographic principle, theorized to be a property of quantum gravity, postulates that the description of a volume of space can be encoded on a lower-dimensional boundary. The anti-de Sitter (AdS)/conformal field theory correspondence or duality1 is the principal example of holography. The Sachdev-Ye-Kitaev (SYK) model of N ≫ 1 Majorana fermions2,3 has features suggesting the existence of a gravitational dual in AdS2, and is a new realization of holography4-6. We invoke the holographic correspondence of the SYK many-body system and gravity to probe the conjectured ER=EPR relation between entanglement and spacetime geometry7,8 through the traversable wormhole mechanism as implemented in the SYK model9,10. A qubit can be used to probe the SYK traversable wormhole dynamics through the corresponding teleportation protocol9. This can be realized as a quantum circuit, equivalent to the gravitational picture in the semiclassical limit of an infinite number of qubits9. Here we use learning techniques to construct a sparsified SYK model that we experimentally realize with 164 two-qubit gates on a nine-qubit circuit and observe the corresponding traversable wormhole dynamics. Despite its approximate nature, the sparsified SYK model preserves key properties of the traversable wormhole physics: perfect size winding11-13, coupling on either side of the wormhole that is consistent with a negative energy shockwave14, a Shapiro time delay15, causal time-order of signals emerging from the wormhole, and scrambling and thermalization dynamics16,17. Our experiment was run on the Google Sycamore processor. By interrogating a two-dimensional gravity dual system, our work represents a step towards a program for studying quantum gravity in the laboratory. Future developments will require improved hardware scalability and performance as well as theoretical developments including higher-dimensional quantum gravity duals18 and other SYK-like models19.

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 ($\pi \to \mu \nu_{\mu}$) 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)].

In a nontrivial background geometry with extra dimensions, gravitational effects will depend on the shape of the Kaluza-Klein excitations of the graviton. We investigate a consistent scenario of this type with two positive tension three-branes separated in a five-dimensional Anti-de Sitter geometry. The graviton is localized on the ``Planck'' brane, while a gapless continuum of additional gravity eigenmodes probe the {\it infinitely} large fifth dimension. Despite the background five-dimensional geometry, an observer confined to either brane sees gravity as essentially four-dimensional up to a position-dependent strong coupling scale, no matter where the brane is located. We apply this scenario to generate the TeV scale as a hierarchically suppressed mass scale. Arbitrarily light gravitational modes appear in this scenario, but with suppressed couplings. Real emission of these modes is observable at future colliders; the effects are similar to those produced by {\it six} large toroidal dimensions.

The existence of maximally supersymmetric solutions to heterotic string theory that are not toroidal compactifications of the ten-dimensional superstring is established. We construct an exact fermionic realization of an $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ supersymmetric string theory in $D\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}8$ with non-simply-laced gauge group $\mathrm{Sp}(20)$. Toroidal compactification to six and four dimensions gives maximally extended supersymmetric theories with reduced rank $(4,12)$ and $(6,14)$, respectively.

We demonstrate that all unitary representations of the N=2 superconformal algebra (for c>3) may be obtained from representations of SO(2,1) current algebra by subtracting and then adding back a free boson. This construction gives insight into the unitary domains for N=2 representations. It may also have a deeper structural significance.

We show that Witten's open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the convential action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.

The discovery of a Higgs particle is possible in a variety of search channels at the LHC. However, the true identity of any putative Higgs boson will, at first, remain ambiguous until one has experimentally excluded other possible assignments of quantum numbers and couplings. We quantify the degree to which one can discriminate a standard model Higgs boson from ``look-alikes'' at, or close to, the moment of discovery at the LHC. We focus on the fully-reconstructible golden decay mode to a pair of $Z$ bosons and a four-lepton final state. Considering both on-shell and off-shell $Z$'s, we show how to utilize the full decay information from the events, including the distributions and correlations of the five relevant angular variables. We demonstrate how the finite phase space acceptance of any LHC detector sculpts the decay distributions, a feature neglected in previous studies. We use likelihood ratios to discriminate a standard model Higgs from look-alikes with other spins or nonstandard parity, $CP$, or form factors. For a resonance mass of $200\text{ }\text{ }\mathrm{GeV}/{c}^{2}$, we achieve a median discrimination significance of $3\ensuremath{\sigma}$ with as few as 19 events, and even better discrimination for the off-shell decays of a $145\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ resonance.

This white paper summarizes the workshop U.S. Cosmic Visions: New Ideas in Dark Matter held at University of Maryland on March 23-25, 2017.

Quantum machine learning could possibly become a valuable alternative to classical machine learning for applications in high energy physics by offering computational speedups. In this study, we employ a support vector machine with a quantum kernel estimator (QSVM-Kernel method) to a recent LHC flagship physics analysis: $t\overline{t}H$ (Higgs boson production in association with a top quark pair). In our quantum simulation study using up to 20 qubits and up to $50\phantom{\rule{0.16em}{0ex}}000$ events, the QSVM-Kernel method performs as well as its classical counterparts in three different platforms from Google Tensorflow Quantum, IBM Quantum, and Amazon Braket. Additionally, using 15 qubits and 100 events, the application of the QSVM-Kernel method on the IBM superconducting quantum hardware approaches the performance of a noiseless quantum simulator. Our study confirms that the QSVM-Kernel method can use the large dimensionality of the quantum Hilbert space to replace the classical feature space in realistic physics data sets.

One of the major objectives of the experimental programs at the Large Hadron Collider (LHC) is the discovery of new physics. This requires the identification of rare signals in immense backgrounds. Using machine learning algorithms greatly enhances our ability to achieve this objective. With the progress of quantum technologies, quantum machine learning could become a powerful tool for data analysis in high energy physics. In this study, using IBM gate-model quantum computing systems, we employ the quantum variational classifier method in two recent LHC flagship physics analyses: (Higgs boson production in association with a top quark pair, probing the Higgs boson couplings to the top quark) and H → μ+μ− (Higgs boson decays to two muons, probing the Higgs boson couplings to second-generation fermions). We have obtained early results with 10 qubits on the IBM quantum simulator and the IBM quantum hardware. With small training samples of 100 events on the quantum simulator, the quantum variational classifier method performs similarly to classical algorithms such as SVM (support vector machine) and BDT (boosted decision tree), which are often employed in LHC physics analyses. On the quantum hardware, the quantum variational classifier method has shown promising discrimination power, comparable to that on the quantum simulator. This study demonstrates that quantum machine learning has the ability to differentiate between signal and background in realistic physics datasets. We foresee the usage of quantum machine learning in future high-luminosity LHC physics analyses, including measurements of the Higgs boson self-couplings and searches for dark matter.

We interpret the new particle at the Large Hadron Collider as a $CP$-even scalar and investigate its electroweak quantum number. Assuming an unbroken custodial invariance as suggested by precision electroweak measurements, only four possibilities are allowed if the scalar decays to pairs of gauge bosons, as exemplified by a dilaton/radion, a nondilatonic electroweak singlet scalar, an electroweak doublet scalar, and electroweak triplet scalars. We show that current LHC data already strongly disfavor both the ``plain-vanilla'' dilatonic and nondilatonic singlet imposters. On the other hand, a generic Higgs doublet gives excellent fits to the measured event rates of the newly observed scalar resonance, while the Standard Model Higgs boson gives a slightly worse overall fit due to the lack of a signal in the $\ensuremath{\tau}\ensuremath{\tau}$ channel. The triplet imposter exhibits some tension with the data. The global fit indicates that the enhancement in the diphoton channel could be attributed to an enhanced partial decay width, while the production rates are consistent with the Standard Model expectations. We emphasize that more precise measurements of the ratio of event rates in the $WW$ over $ZZ$ channels, as well as the event rates in $b\overline{b}$ and $\ensuremath{\tau}\ensuremath{\tau}$ channels, are needed to further distinguish the Higgs doublet from the triplet imposter.

A bstract Using the LHC and Tevatron data, we set upper and lower limits on the total width of the Higgs-like boson. The upper limit is based on the well-motivated assumption that the Higgs coupling to a W or Z pair is not much larger than in the Standard Model. These width limits allow us to convert the rate measurements into ranges for the Higgs couplings to various particles. A corollary of the upper limit on the total width is an upper limit on the branching fraction of exotic Higgs decays. Currently, this limit is 47% at the 95% CL if the electroweak symmetry is broken only by doublets.

The long-standing difference between the experimental measurement and the standard-model prediction for the muon's anomalous magnetic moment, a μ = (g μ − 2)/2, may be explained by the presence of new weakly interacting particles with masses of a few 100 GeV. Particles of this kind can generally be directly produced at the LHC, and thus they may already be constrained by existing data. In this work, we investigate this connection between a μ and the LHC in a model-independent approach, by introducing one or two new fields beyond the standard model with spin and weak isospin up to one. For each case, we identify the preferred parameter space for explaining the discrepancy of a μ and derive bounds using data from LEP and the 8 TeV LHC run. Furthermore, we estimate how these limits could be improved with the 14 TeV LHC. We find that the 8 TeV results already rule out a subset of our simplified models, while almost all viable scenarios can be tested conclusively with 14 TeV data.

We study classically scale invariant models in which the Standard Model Higgs mass term is replaced in the Lagrangian by a Higgs portal coupling to a complex scalar field of a dark sector. We focus on models that are weakly coupled with the quartic scalar couplings nearly vanishing at the Planck scale. The dark sector contains fermions and scalars charged under dark SU(2) × U(1) gauge interactions. Radiative breaking of the dark gauge group triggers electroweak symmetry breaking through the Higgs portal coupling. Requiring both a Higgs boson mass of 125.5 GeV and stability of the Higgs potential up to the Planck scale implies that the radiative breaking of the dark gauge group occurs at the TeV scale. We present a particular model which features a long-range abelian dark force. The dominant dark matter component is neutral dark fermions, with the correct thermal relic abundance, and in reach of future direct detection experiments. The model also has lighter stable dark fermions charged under the dark force, with observable effects on galactic-scale structure. Collider signatures include a dark sector scalar boson with mass ≲ 250 GeV that decays through mixing with the Higgs boson, and can be detected at the LHC. The Higgs boson, as well as the new scalar, may have significant invisible decays into dark sector particles.

We examine the soft supersymmetry breaking parameters that result from various ways of embedding the standard model (SM) on D-branes within the type I string picture, allowing the parameters to have large $\mathrm{CP}$-violating phases. One embedding naturally provides the relations among soft parameters to satisfy the electron and neutron electric dipole moment constraints even with large phases, while with other embeddings large phases are not allowed. The results generally suggest how low energy data might teach us about Planck scale physics.

CPT violation has the potential to explain all three existing neutrino anomalies without enlarging the neutrino sector. CPT violation in the Dirac mass terms of the three neutrino flavors preserves on-shell Lorentz invariance, but generates independent masses for neutrinos and antineutrinos. This specific signature is strongly motivated by braneworld scenarios with extra dimensions, where neutrinos are the natural messengers for Standard Model physics of CPT violation in the bulk. A simple model of maximal CPT violation is sufficient to explain the existing neutrino data quite neatly, while making dramatic predictions for the KamLAND and MiniBooNE experiments. We obtain a promising and economical new mechanism for electroweak baryogenesis.

We extend the study of Higgs boson couplings in the ``golden'' $gg\ensuremath{\rightarrow}H\ensuremath{\rightarrow}Z{Z}^{*}\ensuremath{\rightarrow}4\ensuremath{\ell}$ channel in two important respects. First, we demonstrate the importance of off-shell Higgs boson production ($gg\ensuremath{\rightarrow}{H}^{*}\ensuremath{\rightarrow}ZZ\ensuremath{\rightarrow}4\ensuremath{\ell}$) in determining which operators contribute to the $HZZ$ vertex. Second, we include the five operators of lowest nontrivial dimension, including the ${Z}_{\ensuremath{\mu}}{Z}^{\ensuremath{\mu}}\ensuremath{\square}H$ and $H{Z}_{\ensuremath{\mu}}\ensuremath{\square}{Z}^{\ensuremath{\mu}}$ operators that are often neglected. We point out that the former operator can be severely constrained by the measurement of the off-shell ${H}^{*}\ensuremath{\rightarrow}ZZ$ rate and/or unitarity considerations. We provide analytic expressions for the off-peak cross sections in the presence of these five operators. On shell, the ${Z}_{\ensuremath{\mu}}{Z}^{\ensuremath{\mu}}\ensuremath{\square}H$ operator is indistinguishable from its Standard Model counterpart $H{Z}_{\ensuremath{\mu}}{Z}^{\ensuremath{\mu}}$, while the $H{Z}_{\ensuremath{\mu}}\ensuremath{\square}{Z}^{\ensuremath{\mu}}$ operator can be probed, in particular, by the ${Z}^{*}$ invariant mass distribution.

We study Type I string theory compactified on a T^6/Z_3 orientifold. The low-energy dynamics is most conveniently analyzed in terms of D3-branes. We show that a sector of the theory, which corresponds to placing an odd number of D3-branes at orientifold fixed points, can give rise to an SU(5) gauge theory with three generations of chiral matter fields. The resulting model is not fully realistic, but the relative ease with which an adequate gauge group and matter content can be obtained is promising. The model is also of interest from the point of view of supersymmetry breaking. We show that, for fixed values of the closed string modes, the model breaks supersymmetry due to a conflict between a non-perturbatively generated superpotential and an anomalous U(1) D-term potential.

We obtain three generation SU(3)_c X SU(2)_L X U(1)_Y string models in all of the exactly solvable (0,2) constructions sampled by fermionization. None of these examples, including those that are symmetric abelian orbifolds, rely on the Z_2 X Z_2 orbifold underlying the NAHE basis. We present the first known three generation models for which the hypercharge normalization, k_1, takes values smaller than that obtained from an SU(5) embedding, thus lowering the effective gauge coupling unification scale. All of the models contain fractional electrically charged and vectorlike exotic matter that could survive in the light spectrum.

Any local relativistic quantum field theory of Dirac–Weyl fermions conserves CPT. Here we examine whether a simple nonlocal field theory can violate CPT. We construct a new relativistic field theory of fermions, which we call “homeotic”, which is nonlocal but causal and Lorentz invariant. The free homeotic theory is in fact equivalent to free Dirac theory. We show that a homeotic theory with a suitable nonlocal four-fermion interaction is causal and as a result has a well-defined perturbative S-matrix. By coupling a right-handed homeotic fermion to a left-handed Dirac–Weyl fermion, we obtain a causal theory of CPT-violating neutrino oscillations.

This article reviews the physics case for the ILC. Baseline running at 500 GeV as well as possible upgrades and options are discussed. The opportunities on Standard Model physics, Higgs physics, Supersymmetry and alternative theories beyond the Standard Model are described.

{lg_bullet} What is the universe? How did it begin? {lg_bullet} What are matter and energy? What are space and time? These basic questions have been the subject of scientific theories and experiments throughout human history. The answers have revolutionized the enlightened view of the world, transforming society and advancing civilization. Universal laws and principles govern everyday phenomena, some of them manifesting themselves only at scales of time and distance far beyond everyday experience. Particle physics experiments using particle accelerators transform matter and energy, to reveal the basic workings of the universe. Other experiments exploit naturally occurring particles, such as solar neutrinos or cosmic rays, and astrophysical observations, to provide additional insights.

One or more new heavy resonances may be discovered in experiments at the CERN Large Hadron Collider. In order to determine if such a resonance is the long-awaited Higgs boson, it is essential to pin down its spin, CP, and electroweak quantum numbers. Here we describe how to determine what role a newly-discovered neutral CP -even scalar plays in electroweak symmetry breaking, by measuring its relative decay rates into pairs of electroweak vector bosons: W + W −, ZZ, γγ, and Zγ. With the data-driven assumption that electroweak symmetry breaking respects a remnant custodial symmetry, we perform a general analysis with operators up to dimension five. Remarkably, only three pure cases and one nontrivial mixed case need to be disambiguated, which can always be done if all four decay modes to electroweak vector bosons can be observed or constrained. We exhibit interesting special cases of Higgs look-alikes with nonstandard decay patterns, including a very suppressed branching to W + W − or very enhanced branchings to γγ and Zγ. Even if two vector boson branching fractions conform to Standard Model expectations for a Higgs doublet, measurements of the other two decay modes could unmask a Higgs imposter.

LHC experiments have placed strong bounds on the production of supersymmetric colored particles (squarks and gluinos), under the assumption that all flavors of squarks are nearly degenerate. However, the current experimental constraints on stop squarks are much weaker, due to the smaller production cross section and difficult backgrounds. While light stops are motivated by naturalness arguments, it has been suggested that such particles become nearly impossible to detect near the limit where their mass is degenerate with the sum of the masses of their decay products. We show that this is not the case, and that searches based on missing transverse energy (MET) have significant reach for stop masses above 175 GeV, even in the degenerate limit. We consider direct pair production of stops, decaying to invisible LSPs and tops with either hadronic or semi-leptonic final states. Modest intrinsic differences in MET are magnified by boosted kinematics and by shape analyses of MET or suitably-chosen observables related to MET. For these observables we show that the distributions of the relevant backgrounds and signals are well-described by simple analytic functions, in the kinematic regime where signal is enhanced. Shape analyses of MET-related distributions will allow the LHC experiments to place significantly improved bounds on stop squarks, even in scenarios where the stop-LSP mass difference is degenerate with the top mass. Assuming 20/fb of luminosity at 8 TeV, we conservatively estimate that experiments can exclude or discover degenerate stops with mass as large as ~ 360 GeV and 560 GeV for massless LSPs.

The latest results from the ATLAS and CMS experiments at the CERN Large Hadron Collider unequivocally confirm the existence of a resonance X with mass near 125 GeV which could be the Higgs boson of the standard model. Measuring the properties (quantum numbers and couplings) of this resonance is of paramount importance. Initial analyses by the LHC Collaborations disfavor specific alternative benchmark hypotheses, e.g., pure pseudoscalars or gravitons. However, this is just the first step in a long-term program of detailed measurements. We consider the most general set of operators in the decay channels X→ZZ, WW, Zγ, γγ, and derive the constraint implied by the measured rate. This allows us to provide a useful parametrization of the orthogonal independent Higgs coupling degrees of freedom as coordinates on a suitably defined sphere.

We investigate the possibility of large $\mathrm{CP}$-violating phases in the soft breaking terms derived in superstring models. The bounds on the electric dipole moments (EDM's) of the electron and neutron are satisfied through cancellations occurring because of the structure of the string models. Three general classes of four-dimensional string models are considered: (i) orbifold compactifications of perturbative heterotic string theory, (ii) scenarios based on Ho\ifmmode \check{r}\else \v{r}\fi{}ava-Witten theory, and (iii) type I string models (type IIB orientifolds). Nonuniversal phases of the gaugino mass parameters greatly facilitate the necessary cancellations among the various contributions to the EDM's; in the overall modulus limit, the gaugino masses are universal at the tree level in both the perturbative heterotic models and the Ho\ifmmode \check{r}\else \v{r}\fi{}ava-Witten scenarios, which severely restricts the allowed regions of parameter space. Nonuniversal gaugino masses do arise at one-loop in the heterotic orbifold models, providing for corners of parameter space with $\mathcal{O}(1)$ phases consistent with the phenomenological bounds. However, there is a possibility of nonuniversal gaugino masses at the tree level in the type I models, depending on the details of the embedding of the SM into the D-brane sectors. We find that, in a minimal model with a particular embedding of the standard model gauge group into two D-brane sectors, viable large phase solutions can be obtained over a wide range of parameter space.

We examine arguments that could avoid light superpartners as an implication of supersymmetric radiative electroweak symmetry breaking. We argue that, from the point of view of string theory and standard approaches to generating the μ term, cancellations among parameters are not a generic feature. While the coefficients relating MZ to parameters in the soft supersymmetry breaking Lagrangian can be made smaller, these same mechanisms lead to lighter superpartner masses at the electroweak scale. Consequently we strengthen the implication that gluinos, neutralinos, and charginos are light and likely to be produced at the Fermilab Tevatron and a linear collider.

We derive a Landau-Ginzburg description of semionic superconductors. On a fundamental level the lagrangian of the system involves two vector potentials: the ordinary electromagnetic potential and a potential that describes the statistical interaction between semions. The Goldstone pole in the current correlator of the semionic gas (which was discovered in a mean field expansion by Fetter et al.) occurs when the polarization-induced Chern-Simons mass term for the statistical vector potential exactly cancels the bare term responsible for the statistics. We speculate about reasons why this cancellations should hold beyond the lowest order in the mean field expansion. When the cancellation occurs, it is possible to rewrite the system in terms of a standard Landau-Ginzburg order parameter. We derive the effective long wavelength description of the dynamics of this order parameter interacting with the electromagnetic field. Apart from the sort of anisotropies one might expect in any theory of superconductivity of layered materials, we find a time reversal violating term in the electromagnetic field lagrangian which may be the distinguishing feature of the anyonic theory of superconductivity.

A missing energy discovery is possible at the LHC with the first $100\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of understood data. We present a realistic strategy to rapidly narrow the list of candidate theories at, or close to, the moment of discovery. The strategy is based on robust ratios of inclusive counts of simple physics objects. We study specific cases showing discrimination of look-alike models in simulated data sets that are at least 10 to 100 times smaller than used in previous studies. We discriminate supersymmetry models from nonsupersymmetric look-alikes with only $100\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of simulated data, using combinations of observables that trace back to differences in spin.

An electroweak singlet scalar can couple to pairs of vector bosons through loop-induced dimension five operators. Compared to a standard model Higgs boson, the singlet decay widths in the diphotons and $Z\ensuremath{\gamma}$ channels are generically enhanced, while decays into massive final states like $WW$ and $ZZ$ are kinematically disfavored. The overall event rates into $\ensuremath{\gamma}\ensuremath{\gamma}$ and $Z\ensuremath{\gamma}$ can exceed the standard model expectations by orders of magnitude. Such a singlet may appear as a resonant signal in the $\ensuremath{\gamma}\ensuremath{\gamma}$ and $Z\ensuremath{\gamma}$ channels, even with a mass above the $WW$ kinematic threshold.

Recently we proposed a framework for explaining the observed evidence for neutrino oscillations without enlarging the neutrino sector, by introducing CPT-violating Dirac masses for the neutrinos. In this Letter we continue the exploration of the phenomenology of CPT violation in the neutrino sector. We show that our CPT-violating model fits the existing SuperKamiokande data at least as well as the standard atmospheric neutrino oscillation models. We discuss the challenge of measuring CP violation in a neutrino sector that also violates CPT. We point out that the proposed off-axis extension of MINOS looks especially promising in this regard. Finally, we describe a method to compute CPT-violating neutrino effects by mocking them up with analog matter effects.

International Journal of Modern Physics AVol. 06, No. 29, pp. 5155-5214 (1991) ReviewNo AccessTHE THEORY OF ANYONIC SUPERCONDUCTIVITY: A REVIEWJOSEPH D. LYKKEN, JACOB SONNENSCHEIN, and NATHAN WEISSJOSEPH D. LYKKENTheory Group, MS106, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois, 60510, USA, JACOB SONNENSCHEINSchool of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel, and NATHAN WEISSDepartment of Physics, University of British Columbia, Vancouver, B.C., V6T2A6, Canadahttps://doi.org/10.1142/S0217751X91002434Cited by:41 Next AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail You currently do not have access to the full text article. Recommend the journal to your library today! 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Semenoff12 June 2013 | Journal of High Energy Physics, Vol. 2013, No. 6Relativistic Green functions in a plane-wave gravitational backgroundA N Vaidya, C Farina, M S Guimarães and M J Neves12 July 2007 | Journal of Physics A: Mathematical and Theoretical, Vol. 40, No. 30Three methods for calculating the Feynman propagatorF. A. Barone, H. Boschi-Filho and C. Farina1 May 2003 | American Journal of Physics, Vol. 71, No. 5Effective action for QED in 2+1 dimensions at finite temperatureMarcelo Hott and Georgios Metikas12 August 1999 | Physical Review D, Vol. 60, No. 6Magnetization and dynamically induced finite densities in three-dimensional Chern-Simons QEDTaichi Roll and Hiroshi Kato1 Jul 1999 | Nuclear Physics B, Vol. 551, No. 3Two-particle scattering theory for anyonsC. Korff, G. Lang and R. Schrader1 Apr 1999 | Journal of Mathematical Physics, Vol. 40, No. 4String holonomy and extrinsic geometry in four-dimensional topological gauge theoryRichard J. Szabo1 Oct 1998 | Nuclear Physics B, Vol. 531, No. 1-3Dual response models for the fractional quantum Hall effectL. Cooper, I. I. Kogan, A. Lopez and R. J. Szabo15 September 1998 | Physical Review B, Vol. 58, No. 12Curing fermion mass gauge variance in QED2+1I.V. Tyutin and Vadim Zeitlin1 Jul 1998 | Physics Letters B, Vol. 430, No. 3-4Dynamical Generation of Fermion Mass and Magnetic Field in Three-Dimensional QED with Chern-Simons TermTaichi Itoh and Hiroshi Kato6 July 1998 | Physical Review Letters, Vol. 81, No. 1Effective QED actions: Representations, gauge invariance, anomalies, and mass expansionsS. Deser, L. Griguolo and D. Seminara15 June 1998 | Physical Review D, Vol. 57, No. 12Chiral and parity anomalies at finite temperature and densityA.N. Sissakian, O.Yu. Shevchenko and S.B. Solganik1 May 1998 | Nuclear Physics B, Vol. 518, No. 1-2Perturbative Evidence of Nonuniversality in the Quantized Hall Conductivity of A Disordered Relativistic 2D Electron GasN. Balić, C. A. A. de Carvalho, R. M. Cavalcanti, and P. Donatis21 November 2011 | Modern Physics Letters B, Vol. 12, No. 09Influence of the Aharonov-Bohm flux on the optical polarons in the molecular-crystal model with the dispersion term in a ringHao Chen and Yuan Chen1 Feb 1998 | Solid State Communications, Vol. 105, No. 8Induced Chern-Simons-type terms in general metric nonlinear σ modelsF. M. de Carvalho Filho15 October 1997 | Physical Review D, Vol. 56, No. 8Gauge Invariance, Finite Temperature, and Parity Anomaly in D=3S. Deser, L. Griguolo and D. Seminara15 September 1997 | Physical Review Letters, Vol. 79, No. 11Thermodynamic properties of spontaneous magnetization in three-dimensional Chern-Simons QEDShinya Kanemura and Takao Matsushita15 July 1997 | Physical Review D, Vol. 56, No. 2Chern-Simons term at finite densityA.N. Sissakian, O.Yu. Shevchenko and S.B. Solganik1 Jun 1997 | Physics Letters B, Vol. 403, No. 1-2Quantum structural approach to high- Tc ssuperconductivity theory: Herzberg-Teller, Renner-Teller, Jahn-Teller effects and intervalent geminal charge transferYing-Nan Chiu1 March 1997 | Physical Review B, Vol. 55, No. 9Effective theory for parity-conserving three-dimensional QEDI. J. R. Aitchison, C. D. Fosco and F. D. Mazzitelli15 September 1996 | Physical Review D, Vol. 54, No. 6Charge condensation in QED3 with a Chern-Simons termTaichi Itoh and Toshiro Sato1 Jan 1996 | Physics Letters B, Vol. 367, No. 1-4Formulation of the Landau-Lifshitz model of ferromagnetism as a constrained dynamical systemR. Banerjee and B. Chakraborty1 Aug 1995 | Nuclear Physics B, Vol. 449, No. 1-2Topological excitations in a condensate of nonrelativistic bosons coupled to Maxwell and Chern-Simons fieldsIgor V. Barashenkov and Alexander O. Harin15 August 1995 | Physical Review D, Vol. 52, No. 4Magnetization in (2+1)-dimensional QED at finite temperature and densityJens O. Andersen and Tor Haugset15 March 1995 | Physical Review D, Vol. 51, No. 6Bibliography1 Jan 1995Structure of the effective potential in nonrelativistic Chern-Simons field theoryD. Caenepeel, F. Gingras, M. Leblanc and D. G. C. McKeon15 May 1994 | Physical Review D, Vol. 49, No. 10Diamagnetism of a gas of 2D-fermions in strong non-homogeneous magnetic fields and anyonsO. Hudák1 Jan 1994 | Czechoslovak Journal of Physics, Vol. 44, No. 1Schwinger's method for a harmonic oscillator with a time-dependent frequencyCarlos Farina and Antonio J. Seguí-Santonja1 Dec 1993 | Physics Letters A, Vol. 184, No. 1Universality of the shift of the Chern-Simons parameter for a general class of BRS invariant regularizationsG. Giavarini, C.P. Martin and F.Ruiz Ruiz1 Sep 1993 | Physics Letters B, Vol. 314, No. 3-4Gauge-independent analysis of dynamical systems with Chern-Simons termR. Banerjee15 September 1993 | Physical Review D, Vol. 48, No. 6A particular realization of a gravitational anyonA.A. Kehagias and C.E. Vayonakis1 Mar 1993 | Physics Letters B, Vol. 301, No. 4Operator algebra in Chern-Simons theory on a torusChoon-Lin Ho and Yutaka Hosotani8 March 1993 | Physical Review Letters, Vol. 70, No. 10Anyons in a four-dimensional world with gravityC.E. Vayonakis1 Jan 1993 | Vistas in Astronomy, Vol. 37Self-dual vortices in the generalized Abelian Higgs model with independent Chern-Simons interactionChanju Kim15 January 1993 | Physical Review D, Vol. 47, No. 2A Chemist's View of BCS Theory for Low Tc Superconductivity and Its Relationship to Charge Transfer and High Tc SuperconductivityYing-Nan Chiu24 September 2013 | Journal of the Chinese Chemical Society, Vol. 39, No. 5Aspects Of Chern-Simons TheoryG. V. Dunne Recommended Vol. 06, No. 29 Metrics History Received 8 March 1991 PDF download

We propose an action for an interacting closed bosonic string. Our formalism relies heavily on ideas discussed by Witten for the open bosonic string. We also obtain the gauge fixed quantum action for the fully interacting open bosonic string.

Any operator realization of the N = 2 superconformal algebra is equivalent to composites of a free scalar field (which defines the local U(1) current) and certain non-local chiral operators. In certain cases, such as the minimal N = 2 discrete series models, the non-local operators generate an associative algebra of parafermions. The spectrum of conformal primary fields in such models is finitely-reducible with respect to representations of the parafermion algebra. In this paper, all models of this type are derived. They form a two-parameter extended family of N = 2 models which includes the minimal models as a one-parameter subset. An explicit construction is given of the unitary N = 2 highest weight modules in the Neveu-Schwarz and Ramond sectors. These results have significant applications to superstring theory. We present an infinite list of new c = 9 models, and show how an even larger class are obtained from tensor products of our construction. We conjecture that any rational conformal theory corresponding to a classical ground state of the heterotic superstring, with space-time supersymmetry, contains one of these c = 9 N = 2 models.

Theories of new physics often involve a large number of unknown parameters which need to be scanned. Additionally, a putative signal in a particular channel may be due to a variety of distinct models of new physics. This makes experimental attempts to constrain the parameter space of motivated new physics models with a high degree of generality quite challenging. We describe how the reweighting of events may allow this challenge to be met, as fully simulated Monte Carlo samples generated for arbitrary benchmark models can be effectively re-used. In particular, we suggest procedures that allow more efficient collaboration between theorists and experimentalists in exploring large theory parameter spaces in a rigorous way at the LHC.

We construct brane configurations leading to chiral four dimensional N=1 supersymmetric gauge theories. The brane realizations consist of intersecting Neveu-Schwarz five-branes and Dirichlet four-branes in non-flat spacetime backgrounds. We discuss in some detail the construction in a C^2/Z_M orbifold background. The infrared theory on the four-brane worldvolume is a four dimensional N=1 SU(N)^M gauge theory with chiral matter representations. We discuss various consistency checks and show that the spectral curves describing the Coulomb phase of the theory can be obtained once the orbifold brane construction is embedded in M-theory. We also discuss the addition of extra vectorlike matter and other interesting generalizations.

We estimate the Fermilab Tevatron run II potential for top and bottom squark searches. We find an impressive reach in several of the possible discovery channels. We also study some new channels which may arise in nonconventional supersymmetry models. In each case we rely on a detailed Monte Carlo simulation of the collider events and the CDF detector performance in run I.

We clarify the relations between string theory and two-dimensional gravity.

The renormalized Chern-Simons term at finite density is shown to vanish when the renormalized coefficient at zero density takes values $\frac{{\mathrm{Ne}}^{2}}{2\ensuremath{\pi}}$. Thus in the Chern-Simons description a system of anyons at zero temperature is a superfluid. This result is shown to hold to all orders in perturbation theory by generalizing a nonrenormalization theorem of the zero-density case. We also discuss the finite-temperature case, where a perturbative Chern-Simons mass appears.

Attempts so far at constructing a covariant closed-string field theory have been frustrated by the fact that modular invariance always appears to be violated. At both the tree and loop levels, moduli space is either overcounted an infinite number of times, or undercounted because of a missing region. We solve this problem by demonstrating that a new Iclosed four-string interactionR is necessary to reproduce the closed-string amplitude which precisely fills the missing region. This closed four-string interaction, which has the topology of a tetrahedron, is predicted by geometric string field theory. The tetrahedron graph is generated by gauge fixing the geometric theory's local gauge group, the unified string group, and is the exact counterpart of the instantaneous four-fermion Coulomb term found in QED. We prove the existence of this tetrahedron graph both analytically and by direct computer calculation and show that it is the key to reproducing the Shapiro-Virasoro amplitude.

A dilaton could be the dominant messenger between standard model fields and dark matter. The measured dark matter relic abundance relates the dark matter mass and spin to the conformal breaking scale. The dark matter-nucleon spin-independent cross section is predicted in terms of the dilaton mass. We compute the current constraints on the dilaton from LEP and Tevatron experiments, and the gamma-ray signal from dark matter annihilation to dilatons that could be observed by Fermi Large Area Telescope.

We review the status of CPT violation in the neutrino sector. Apart from LSND, current data favors three flavors of light stable neutrinos and antineutrinos, with both halves of the spectrum having one smaller mass splitting and one larger mass splitting. Oscillation data for the smaller splitting is consistent with CPT. For the larger splitting, current data favor an antineutrino mass-squared splitting that is an order of magnitude larger than the corresponding neutrino splitting, with the corresponding mixing angle less-than-maximal. This CPT-violating spectrum is driven by recent results from MINOS, but is consistent with other experiments if we ignore LSND. We describe an analysis technique which, together with MINOS running optimized for muon antineutrinos, should be able to conclusively confirm the CPT-violating spectrum proposed here, with as little as three times the current data set. If confirmed, the CPT-violating neutrino mass-squared difference would be an order of magnitude less than the current most-stringent upper bound on CPT violation for quarks and charged leptons.

Direct searches for electroweak pair production of new particles at the LHC are a difficult proposition, due to the large background and low signal cross sections. We demonstrate how these searches can be improved by a combination of new razor variables and shape analysis of signal and background kinematics. We assume that the pair-produced particles decay to charged leptons and missing energy, either directly or through a W boson. In both cases the final state is a pair of opposite sign leptons plus missing transverse energy. We estimate exclusion reach in terms of sleptons and charginos as realized in minimal supersymmetry. We compare this super-razor approach in detail to analyses based on other kinematic variables, showing how the super-razor uses more of the relevant kinematic information while achieving higher selection efficiency on signals, including cases with compressed spectra.

These lectures give a self-contained introduction to supersymmetry from a modern perspective. Emphasis is placed on material essential to understanding duality. Topics include: central charges and BPS-saturated states, supersymmetric nonlinear sigma models, N=2 Yang-Mills theory, holomorphy and the N=2 Yang-Mills beta function, supersymmetry in 2, 6, 10, and 11 spacetime dimensions.

We examine whether the cosmic ray positron excess observed by PAMELA can be explained by neutralino annihilation in the next-to-minimal supersymmetric standard model (NMSSM). The main dark matter annihilation products are the lightest $CP$-even scalar ${h}_{1}$ plus the lightest $CP$-odd scalar ${a}_{1}$, with the ${a}_{1}$ decaying into two muons. The energetic positrons needed to explain PAMELA are thus obtained in the NMSSM simply from kinematics. The required large annihilation cross section is obtained from an $s$-channel resonance with the heavier $CP$-odd scalar ${a}_{2}$. Various experiments constrain the PAMELA-favored NMSSM parameter space, including collider searches for a light ${a}_{1}$. These constraints point to a unique corner of the NMSSM parameter space, having a lightest neutralino mass around 160 GeV and a very light pseudoscalar mass less than a GeV. A simple parametrized formula for the charge-dependent solar modulation effects reconciles the discrepancy between the PAMELA data and the estimated background at lower energies. We also discuss the electron and gamma-ray spectra from the Fermi LAT observations, and point out the discrepancy between the NMSSM predictions and Fermi LAT preliminary results and possible resolution. An NMSSM explanation of PAMELA makes three striking and uniquely correlated predictions: the rise in the PAMELA positron spectrum will turn over at around 70 GeV, the dark matter particle mass is less than the top quark mass, and a light sub-GeV pseudoscalar will be discovered at colliders.

We present the activities of the `New Physics' working group for the `Physics at TeV Colliders' workshop (Les Houches, France, 5--23 June, 2017). Our report includes new physics studies connected with the Higgs boson and its properties, direct search strategies, reinterpretation of the LHC results in the building of viable models and new computational tool developments.

We study scenarios in which there is a hierarchy of two sets of large compactified extra dimensions. One particularly interesting case has a single millimeter size extra dimension and five TeV−1 size dimensions. The Standard Model gauge bosons have Kaluza–Klein excitations with respect to one of the TeV scale dimensions. We discuss astrophysical constraints on this scenario, as well as prospects for signals at future high energy colliders.

We discuss the relation between 2D gravity and critical string theory in two target space dimensions. In particular we consider the effect that the tachyon, and its back reaction on the metric, has on the interpretation of the critical theory as a non-critical theory coupled to world sheet gravity. We examine the generalizations of the black hole solution of the critical theory and argue that a generic feature of these solutions is that they have two horizons, similar to, but distinct from, the Reissner-Nordstrøm black hole. We also find some indication that the tachyon may destabilize a naked singularity. Finally we show that KPZ scaling is valid for the general solution of the critical theory, when it is interpreted as a theory of world sheet gravity.

The steepest descent solution of the Penner matrix model has a one-cut eigenvalue support. Criticality results when the two branch points of this support coalesce. The support is then a closed contour in the complex eigenvalue plane. Simple generalizations of the Penner model have multi-cut solutions. For these models, the eigenvalue support at criticality is also a closed contour, but consisting of several cuts. We solve the simplest such model, which we call the KT model, in the double-scaling limit. Its free energy is a Legendre transform of the free energy of the c = 1 string compactified to the critical radius of the Kosterlitz–Thouless phase transition.

This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 1 contains the table of contents and introduction and gives a summary of the case for a 500 GeV linear collider.

We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four-dimensional brane located in a (nearly) flat extra-dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions, R, and a physical ultraviolet cutoff of the order of the fundamental Planck scale in the higher-dimensional theory, M. We show that, having implemented cutoffs, the radius of the extra dimensions cannot be arbitrarily large for M≳1 TeV. Moreover, for finite radii, the gravitational effects localized on the brane can substantially alter the phenomenology of collider and/or table-top gravitational experiments. This phenomenology is dictated by the presence of a massless graviton, with standard couplings to the matter fields, and a massive graviton which couples to matter in a much stronger way. While graviton KK modes lighter than the massive graviton couple to matter in a standard way, the couplings to matter of the heavier KK modes are strongly suppressed.

We examine the cosmology and hierarchy of scales in models with branes immersed in a five-dimensional curved spacetime subject to radion stabilization. When the radion field is time-independent and the inter-brane spacing is stabilized, the universe can naturally find itself in the radiation-dominated epoch. This feature is independent of the form of the stabilizing potential. We recover the standard Friedmann equations without assuming a specific form for the bulk energy-momentum tensor. In the models considered, if the observable brane has positive tension, a solution to the hierarchy problem requires the presence of a negative tension brane somewhere in the bulk. We find that the string scale can be as low as the electroweak scale. In the situation of self-tuning branes where the bulk cosmological constant is set to zero, the brane tensions have hierarchical values. In the case of a polynomial stabilizing potential no new hierarchy is created.

We derive several results pertaining to anyonic superconductivity as described by a Chern-Simons field theory. (1) The renormalized Chern-Simons term at finite density is shown to vanish when the renormalized coefficient at zero density takes values Ne 2 /2π. This is the field-theoretical requirement to have a massless pole in the current-current correlator. We can then show that in the Chern-Simons description a system of charged anyons at zero temperature is a superconductor. This result is shown to hold to all orders in perturbation theory by generalizing a nonrenormalization theorem of the zero density case. (2) At finite temperature the renormalized Chern-Simons term does not vanish at the one-loop perturbative level. We compute the mass of this apparent “pseudo-Goldstone mode”. We also exhibit an effect suggestive of critical behavior, for this same system, at a nonzero T c . We discuss the possible implications of these perturbative results. (3) A low energy effective action for an anyonic superconductor is derived directly from Chern-Simons field theory. Several P and T violating effects occur.

We consider the phenomenological implications of a soft SUSY breaking term BN at the TeV scale (here B is the U(1)_Y gaugino and N is the right-handed neutrino field). In models with a massless (or nearly massless) neutralino, such a term will give rise through the see-saw mechanism to new contributions to the mass matrix of the light neutrinos. We treat the massless neutralino as an (almost) sterile neutrino and find that its mass depends on the square of the soft SUSY breaking scale, with interesting consequences for neutrino physics. We also show that, although it requires fine-tuning, a massless neutralino in the MSSM or NMSSM is not experimentally excluded. The implications of this scenario for neutrino physics are discussed.

We present a new approach to quintessential inflation, in which both dark energy and inflation are explained by the evolution of a single scalar field. We start from a simple scalar potential with both oscillatory and exponential behavior. We employ the conventional reheating mechanism of new inflation, in which the scalar decays to light fermions with a decay width that is proportional to the scalar mass. Because our scalar mass is proportional to the Hubble rate, this gives adequate reheating at early times while shutting off at late times to preserve quintessence and satisfy nucleosynthesis constraints. We discuss a simple model which solves the horizon, flatness, and “why now” problems. Without any additional tuning of parameters, this model satisfies all constraints from CMB, large scale structure, and nucleosynthesis. The predictions for the inflationary spectral indices are nS=nT=1. In this model we are currently beginning the third cosmic epoch of accelerated expansion.

The increasing use of multivariate methods, and in particular the Matrix Element Method (MEM), represents a revolution in experimental particle physics. With continued exponential growth in computing capabilities, the use of sophisticated multivariate methods-- already common-- will soon become ubiquitous and ultimately almost compulsory. While the existence of sophisticated algorithms for disentangling signal and background might naively suggest a diminished role for theorists, the use of the MEM, with its inherent connection to the calculation of differential cross sections will benefit from collaboration between theorists and experimentalists. In this white paper, we will briefly describe the MEM and some of its recent uses, note some current issues and potential resolutions, and speculate about exciting future opportunities.

In response to the growing interest in building a Neutrino Factory to produce high intensity beams of electron- and muon-neutrinos and antineutrinos, in October 1999 the Fermilab Directorate initiated two six-month studies. The first study, organized by N. Holtkamp and D. Finley, was to investigate the technical feasibility of an intense neutrino source based on a muon storage ring. This design study has produced a report in which the basic conclusion is that a Neutrino Factory is technically feasible, although it requires an aggressive R&D program. The second study, which is the subject of this report, was to explore the physics potential of a Neutrino Factory as a function of the muon beam energy and intensity, and for oscillation physics, the potential as a function of baseline.

We present some phenomenology of a new class of intersecting D-brane models. Soft supersymmetry (SUSY) breaking terms for these models are calculated in the $u$-moduli dominant SUSY breaking approach (in type IIA). In this case, the dependence of the soft terms on the Yukawas and Wilson lines drops out. These soft terms have a different pattern compared to the usual heterotic string models. Phenomenological implications for dark matter are discussed.

Gravity in five-dimensional braneworld backgrounds may exhibit extra scalar degrees of freedom with problematic features, including kinetic ghosts and strong coupling behavior. Analysis of such effects is hampered by the standard heuristic approaches to braneworld gravity, which use the equations of motion as the starting point, supplemented by orbifold projections and junction conditions. Here we develop the interval approach to braneworld gravity, which begins with an action principle. This shows how to implement general covariance, despite allowing metric fluctuations that do not vanish on the boundaries. We reproduce simple ${\mathbf{Z}}_{\mathbf{2}}$ orbifolds of gravity, even though in this approach we never perform a ${\mathbf{Z}}_{\mathbf{2}}$ projection. We introduce a family of ``straight gauges'', which are bulk coordinate systems in which both branes appear as straight slices in a single coordinate patch. Straight gauges are extremely useful for analyzing metric fluctuations in braneworld models. By explicit gauge-fixing, we show that a general $\mathrm{Ad}{\mathrm{S}}_{5}/\mathrm{Ad}{\mathrm{S}}_{4}$ setup with two branes has at most a radion, but no physical ``brane-bending'' modes.

Braneworld models with induced gravity have the potential to replace dark energy as the explanation for the current accelerating expansion of the Universe. The original model of Dvali, Gabadadze, and Porrati (DGP) demonstrated the existence of a ``self-accelerating'' branch of background solutions, but suffered from the presence of ghosts. We present a new large class of braneworld models which generalize the DGP model. Our models have negative curvature in the bulk, allow a second brane, and have general brane tensions and localized curvature terms. We exhibit three different kinds of ghosts, associated to the graviton zero mode, the radion, and the longitudinal components of massive graviton modes. The latter two species occur in the DGP model, for negative and positive brane tension, respectively. In our models, we find that the two kinds of DGP ghosts are tightly correlated with each other, but are not always linked to the feature of self-acceleration. Our models are a promising laboratory for understanding the origins and physical meaning of braneworld ghosts, and perhaps for eliminating them altogether.

The LHC has started to constrain supersymmetry-breaking parameters by setting bounds on possible colored particles at the weak scale. Moreover, constraints from Higgs physics, flavor physics, the anomalous magnetic moment of the muon, as well as from searches at LEP and the Tevatron have set additional bounds on these parameters. Renormalization Group Invariants (RGIs) provide a very useful way of representing the allowed parameter space by making direct connection with the values of these parameters at the messenger scale. Using a general approach, based on the pMSSM parametrization of the soft supersymmetry-breaking parameters, we analyze the current experimental constraints to determine the probability distributions for the RGIs. As examples of their application, we use these distributions to analyze the question of Gaugino Mass Unification and to probabilistically determine the parameters of General and Minimal Gauge Mediation with arbitrary Higgs mass parameters at the Messenger Scale.

We analyse in detail the SL(2, R) black hole by extending standard techniques of Kac-Moody current algebra to the non-compact case. We construct the elements of the ground ring and exhibit W∞ type structure in the fusion algebra of the discrete states. As a consequence, we can identify some of the exactly marginal deformations of the black hole. We show that these deformations alter not only the spacetime metric but also turn on non-trivial backgrounds for the tachyon and all of the massive modes of the string.

We consider a brane configuration consisting of intersecting Neveu-Schwarz five-branes, Dirichlet four-branes, and an orientifold four-plane in a C2/Z3 orbifold background. We show that the low-energy dynamics is described by a four-dimensional gauge theory with N = 1 supersymmetry and S(N + 4) × SU(N) or SP(2M) × SU(2M) × SU(2M + 4) gauge symmetry. The matter content of this theory is chiral. In particular, the SU group has one matter field in the antisymmetric tensor or symmetric tensor representation and several fields in the fundamental and antifundamental representations. We discuss various consistency checks on these theories. By considering the brane configuration in M-theory we deduce the spectral curves for these theories. Finally, we consider the effects of replacing the orbifold background with a non-singular ALE space (both with and without an orientifold plane) and show that it leaves the spectral curves unchanged.

We present an analysis of the discovery reach for supersymmetric particles at the upgraded Tevatron collider, assuming that SUSY breaking results in universal soft breaking parameters at the grand unification scale, and that the lightest supersymmetric particle is stable and neutral. We first present a review of the literature, including the issues of unification, renormalization group evolution of the supersymmetry breaking parameters and the effect of radiative corrections on the effective low energy couplings and masses of the theory. We consider the experimental bounds coming from direct searches and those arising indirectly from precision data, cosmology and the requirement of vacuum stability. The issues of flavor and CP-violation are also addressed. The main subject of this study is to update sparticle production cross sections, make improved estimates of backgrounds, delineate the discovery reach in the supergravity framework, and examine how this might vary when assumptions about universality of soft breaking parameters are relaxed. With 30 fb$^{-1}$ luminosity and one detector, charginos and neutralinos, as well as third generation squarks, can be seen if their masses are not larger than 200-250 GeV, while first and second generation squarks and gluinos can be discovered if their masses do not significantly exceed 400 GeV. We conclude that there are important and exciting physics opportunities at the Tevatron collider, which will be significantly enhanced by continued Tevatron operation beyond the first phase of Run II.

The work contained herein constitutes a report of the ``Beyond the Standard Model'' working group for the Workshop "Physics at TeV Colliders", Les Houches, France, 26 May--6 June, 2003. The research presented is original, and was performed specifically for the workshop. Tools for calculations in the minimal supersymmetric standard model are presented, including a comparison of the dark matter relic density predicted by public codes. Reconstruction of supersymmetric particle masses at the LHC and a future linear collider facility is examined. Less orthodox supersymmetric signals such as non-pointing photons and R-parity violating signals are studied. Features of extra dimensional models are examined next, including measurement strategies for radions and Higgs', as well as the virtual effects of Kaluza Klein modes of gluons. An LHC search strategy for a heavy top found in many little Higgs model is presented and finally, there is an update on LHC $Z'$ studies.

The two indices that have been proposed for quantifying the accuracy of smooth-following eye movements are shown to be interchangeable. This algebraic fact will permit comparability of values between laboratories only if workers who employ the signal-to-noise ratio (S/N) as their index measure S and N as the total signal and noise power, respectively, in the eye movement record.

Gravity in five-dimensional braneworld backgrounds often exhibits problematic features, including kinetic ghosts, strong coupling, and the van Dam-Veltman-Zakharov (vDVZ) discontinuity. These problems are an obstacle to producing and analyzing braneworld models with interesting and potentially observable modifications of 4d gravity. We examine these problems in a general ${\mathrm{AdS}}_{5}/{\mathrm{AdS}}_{4}$ setup with two branes and localized curvature from arbitrary brane kinetic terms. We use the interval approach and an explicit straight gauge-fixing. We compute the complete quadratic gauge-fixed effective 4d action, as well as the leading cubic order corrections. We compute the exact Green's function for gravity as seen on the brane. In the full parameter space, we exhibit the regions which avoid kinetic ghosts and tachyons. We give a general formula for the strong coupling scale, i.e., the energy scale at which the linearized treatment of gravity breaks down, for relevant regions of the parameter space. We show how the vDVZ discontinuity can be naturally but nontrivially avoided by ultralight graviton modes. We present a direct comparison of warping versus localized curvature in terms of their effects on graviton mode couplings. We exhibit the first example of Dvali-Gabadadze-Porrati (DGP)-like crossover behavior in a general warped setup.

Terascale supersymmetry has the potential to provide a natural explanation of the dominant dark matter component of the standard ΛCDM cosmology. However once we impose the constraints on minimal supersymmetry parameters from current particle physics data, a satisfactory dark matter abundance is no longer prima facie natural. This Neutralino Tuning Problem could be a hint of nonstandard cosmology during and/or after the Terascale era. To quantify this possibility, we introduce an alternative cosmological benchmark based upon a simple model of quintessential inflation. This benchmark has no free parameters, so for a given supersymmetry model it allows an unambiguous prediction of the dark matter relic density. As a example, we scan over the parameter space of the CMSSM, comparing the neutralino relic density predictions with the bounds from WMAP. We find that the WMAP–allowed regions of the CMSSM are an order of magnitude larger if we use the alternative cosmological benchmark, as opposed to ΛCDM. Initial results from the CERN Large Hadron Collider will distinguish between the two allowed regions.

The Higgs boson decay into a pair of real or virtual W bosons, with one of them decaying leptonically, is predicted within the Standard Model to have the largest branching fraction of all Higgs decays that involve an isolated electron or muon, for M h > 120 GeV. We compute analytically the fully-differential width for this h 0→ℓνjj decay at tree level, and then explore some multi-dimensional cuts that preserve the region of large signal. Future searches for semileptonic decays at the Tevatron and LHC, employing fully-differential information as outlined here, may be essential for ruling out or in the Higgs boson and for characterizing a Higgs signal.

We study the supersymmetry reach of the Tevatron in channels containing both isolated leptons and identified tau jets. In the most challenging case, where the branching ratios of gauginos to taus dominate, we find that searches for two leptons, a tau jet and a large amount of missing transverse energy have a much better reach than the classic trilepton signature. With total integrated luminosity of ${\rm L} \gsim 4 {\rm fb}^{-1}$, the Tevatron will start extending the expected LEP-II reach for supersymmetry.

In an effort to promote communication between the formal and phenomenological branches of the high-energy theory community, we provide a description of some important issues in supersymmetric and string phenomenology. We describe each within the context of string constructions, illustrating them with specific examples where applicable. Each topic culminates in a set of questions that we believe are amenable to direct consideration by string theorists, and whose answers we think could help connect string theory and phenomenology.

We demonstrate how much it is possible to deviate from the standard cosmological paradigm of inflation-assisted ΛCDM, keeping within current observational constraints, and without adding to or modifying any theoretical assumptions. We show that within a minimal framework there are many new possibilities, some of them wildly different from the standard picture. We present three illustrative examples of new models, described phenomenologically by a noncanonical scalar field coupled to radiation and matter. These models have interesting implications for inflation, quintessence, reheating, electroweak baryogenesis, and the relic densities of WIMPs and other exotics.

We consider a brane-world construction which incorporates a finite region of flat space, ``the box,'' surrounded by a region of anti-de Sitter space. This hybrid construction provides a framework which interpolates between the scenario proposed by Arkani-Hamed, Dimopoulos and Dvali, and that proposed by Randall and Sundrum. Within this composite framework, we investigate the effects of resonant modes on four-dimensional gravity. We also show that, on a probe brane in the anti-de Sitter region, there is enhanced production of on-shell nonresonant modes. We compare our model to some recent attempts to incorporate the Randall-Sundrum scenario into superstring theory.

We propose a new framework for understanding the hierarchies of fermion masses and mixings. The masses and mixings of all Standard Model (SM) charged fermions other than top arise from higher dimensional operators involving a messenger scalar S and flavon scalars F_i. The flavons spontaneously break SM flavor symmetries at around the TeV scale. The SM singlet scalar S couples directly to the Higgs H and spontaneously breaks another U(1) at the electroweak scale. At the TeV scale, SM quarks and charged leptons have renormalizable couplings to S, but not to H or F_i. These couplings involve new heavy vectorlike fermions. Integrating out these fermions produces a pattern of higher dimensional operators that reproduce the observed hierarchies of the SM masses and mixings in terms of powers of the "little hierarchy": the ratio of the electroweak scale to the flavor-breaking scale. The framework has important phenomenological implications. Flavor-changing neutral currents are within experimental limits but D^0 mixing and B_s->mu+mu- could be close to current sensitivities. The neutral scalar s of the messenger field mixes with the light Higgs of the SM, which can have strong effects on Higgs decay branching fractions. The s mass eigenstate may be lighter than the Higgs, and could be detected at the Tevatron or the LHC.

'BSM physics' is a phrase used in several ways. It can refer to physical phenomena established experimentally but not accommodated by the Standard Model, in particular dark matter and neutrino oscillations (technically also anything that has to do with gravity, since gravity is not part of the Standard Model). 'Beyond the Standard Model' can also refer to possible deeper explanations of phenomena that are accommodated by the Standard Model but only with ad hoc parameterizations, such as Yukawa couplings and the strong CP angle. More generally, BSM can be taken to refer to any possible extension of the Standard Model, whether or not the extension solves any particular set of puzzles left unresolved in the SM. In this general sense one sees reference to the BSM 'theory space' of all possible SM extensions, this being a parameter space of coupling constants for new interactions, new charges or other quantum numbers, and parameters describing possible new degrees of freedom or new symmetries. Despite decades of model-building it seems unlikely that we have mapped out most of, or even the most interesting parts of, this theory space. Indeed we do not even know what is the dimensionality of this parameter space, ormore » what fraction of it is already ruled out by experiment. Since Nature is only implementing at most one point in this BSM theory space (at least in our neighborhood of space and time), it might seem an impossible task to map back from a finite number of experimental discoveries and measurements to a unique BSM explanation. Fortunately for theorists the inevitable limitations of experiments themselves, in terms of resolutions, rates, and energy scales, means that in practice there are only a finite number of BSM model 'equivalence classes' competing at any given time to explain any given set of results. BSM phenomenology is a two-way street: not only do experimental results test or constrain BSM models, they also suggest - to those who get close enough to listen - new directions for BSM model building. Contrary to popular shorthand jargon, supersymmetry (SUSY) is not a BSM model: it is a symmetry principle characterizing a BSM framework with an infinite number of models. Indeed we do not even know the full dimensionality of the SUSY parameter space, since this presumably includes as-yet-unexplored SUSY-breaking mechanisms and combinations of SUSY with other BSM principles. The SUSY framework plays an important role in BSM physics partly because it includes examples of models that are 'complete' in the same sense as the Standard Model, i.e. in principle the model predicts consequences for any observable, from cosmology to b physics to precision electroweak data to LHC collisions. Complete models, in addition to being more explanatory and making connections between diverse phenomena, are also much more experimentally constrained than strawman scenarios that focus more narrowly. One sometimes hears: 'Anything that is discovered at the LHC will be called supersymmetry.' There is truth behind this joke in the sense that the SUSY framework incorporates a vast number of possible signatures accessible to TeV colliders. This is not to say that the SUSY framework is not testable, but we are warned that one should pay attention to other promising frameworks, and should be prepared to make experimental distinctions between them. Since there is no formal classification of BSM frameworks I have invented my own. At the highest level there are six parent frameworks: (1) Terascale supersymmetry; (2) PNGB Higgs; (3) New strong dynamics; (4) Warped extra dimensions; (5) Flat extra dimensions; and (6) Hidden valleys. Here is the briefest possible survey of each framework, with the basic idea, the generic new phenomena, and the energy regime over which the framework purports to make comprehensive predictions.« less

Experimentalists and theorists are still celebrating the Nobel-worthy discovery of the Higgs boson that was announced in July 2012 at CERN’s Large Hadron Collider. Now they are working on the profound implications of that discovery.

A suppression in the spectrum of ultrahigh-energy (UHE, eV) neutrinos will be present in extra-dimensional scenarios, due to enhanced neutrino–anti-neutrino annihilation processes with the supernova relic neutrinos. In the n>4 scenario, n being the number of extra dimensions, neutrinos cannot be responsible for the highest energy events observed in the UHE cosmic ray spectrum. A direct implication of these extra-dimensional interactions would be the absence of UHE neutrinos in ongoing and future neutrino telescopes.

Scalar–tensor gravity is the simplest and best understood modification of general relativity, consisting of a real scalar field coupled directly to the Ricci scalar curvature. Models of this type have self-accelerating solutions. In an example inspired by string dilaton couplings, scalar–tensor gravity coupled to ordinary matter exhibits a de Sitter type expansion, even in the presence of a negative cosmological constant whose magnitude exceeds that of the matter density. This unusual behavior does not require phantoms, ghosts or other exotic sources. More generally, we show that any expansion history can be interpreted as arising partly or entirely from scalar–tensor gravity. To distinguish any quintessence or inflation model from its scalar–tensor variants, we use the fact that scalar–tensor models imply deviations of the post-Newtonian parameters of general relativity and time variation of Newton's gravitational coupling G. We emphasize that next-generation probes of modified GR and the time variation of G are an essential complement to dark energy probes based on luminosity–distance measurements.

We examine the prospects for extending the Tevatron reach for a Standard Model Higgs boson by including the semileptonic Higgs boson decays h → WW → ℓν ℓ jj for M h ≳ 2 M W , and h → Wjj → ℓν ℓ jj for M h ≲ 2 M W , where j is a hadronic jet. We employ a realistic simulation of the signal and backgrounds using the Sherpa Monte Carlo event generator. We find kinematic selections that enhance the signal over the dominant W+ jets background. The resulting sensitivity could be an important addition to ongoing searches, especially in the mass range 120 ≲ M h ≲ 150 GeV. The techniques described can be extended to Higgs boson searches at the Large Hadron Collider.

We exhibit a model in which a single pseudo-Nambu-Goldstone boson explains dark energy, inflation and baryogenesis. The model predicts correlated signals in future collider experiments, WIMP searches, proton decay experiments, dark energy probes, and the PLANCK satellite CMB measurements.

The "golden" channel, in which the newly-discovered Higgs boson decays to four leptons by means of intermediate vector bosons, is important for determining the properties of the Higgs boson and for searching for subtle new physics effects. Different approaches exist for parametrizing the relevant Higgs couplings in this channel; here we relate the use of pseudo-observables to methods based on specifying the most general amplitude or Lagrangian terms for the $HVV$ interactions. We also provide projections for sensitivity in this channel in several novel scenarios, illustrating the use of pseudo-observables, and analyze the role of kinematic distributions and (ratios of) rates in such $H\to4\ell$ studies.

In the same sense that 5D anti--de Sitter space (${\mathrm{AdS}}_{5}$) warped geometries arise naturally from type IIB string theory with stacks of $D3$ branes, ${\mathrm{AdS}}_{7}$ warped geometries arise naturally from $M$ theory with stacks of $M5$ branes. We compactify two spatial dimensions of ${\mathrm{AdS}}_{7}$ to get ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{\ensuremath{\Sigma}}^{2}$, where the metric for ${\ensuremath{\Sigma}}^{2}$ inherits the same warp factor as appears in the ${\mathrm{AdS}}_{5}$. We analyze the 5D spectrum in detail for the case of a bulk scalar or a graviton in ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{T}^{2}$, in a setup which mimics the first Randall-Sundrum model. The results display novel features which might be observed in experiments at the CERN Large Hadron Collider. For example, we obtain TeV scale string winding states without lowering the string scale. This is due to the double warping which is a generic feature of winding states along compactified AdS directions. Experimental verification of these signatures of ${\mathrm{AdS}}_{7}$ could be interpreted as direct evidence for $M$ theory.

It is a common belief among field theorists that path integrals can be computed exactly only in a limited number of special cases, and that most of these cases are already known. However recent developments, which generalize the WKBJ method using equivariant cohomology, appear to contradict this folk wisdom. At the formal level, equivariant localization would seem to allow exact computation of phase space path integrals for an arbitrary partition function! To see how, and if, these methods really work in practice, we have applied them in explicit quantum mechanics examples. We show that the path integral for the 1D hydrogen atom, which is not WKBJ exact, is licalizable and computable using the more general formalism. We find however considerable ambiguities in this approach, which we can only partially resolve. In addition, we find a large class of quantum mechanics examples where the localization procedure breaks down completely.

We revisit the possibility of ``visible sector'' SUSY models: models which are straightforward renormalizable extensions of the Minimal Supersymmetric Standard Model (MSSM), where SUSY is broken at tree level. Models of this type were abandoned twenty years ago due to phenomenological problems, which we review. We then demonstrate that it is possible to construct simple phenomenologically viable visible sector SUSY models. Such models are indeed quite constrained, and have some inelegant features. They also have interesting and distinctive phenomenology. Our models predict light gauginos and very heavy squarks and sleptons. The squarks and sleptons may not be observable at the LHC. The LSP is a stable very light gravitino with a significant Higgsino admixture. The NLSP is mostly Bino. The Higgs boson is naturally heavy. Proton decay is sufficently and naturally suppressed, even for a cutoff scale as low as 108 GeV. The lightest particle of the O'Raifeartaigh sector (the LOP) is stable, and is an interesting cold dark matter candidate.

These lectures give a self-contained introduction to supersymmetry from a modern perspective. Emphasis is placed on material essential to understanding duality. Topics include: central charges and BPS-saturated states, supersymmetric nonlinear sigma models, N=2 Yang-Mills theory, holomorphy and the N=2 Yang-Mills beta function, supersymmetry in 2, 6, 10, and 11 spacetime dimensions.

We propose a Kaluza-Klein cosmology by reversing the usual scenario: instead of starting with a flat 4 + N dimensional universe in which N of the dimensions curl up into a compact manifold, we start with a compact 3 + N dimensional manifold in which 3 of the dimensions are allowed to peel off and expand into the known universe. We reverse the usual “spontaneous compactification” scenario and begin with a closed manifold M3+N which undergoes “spontaneous fissioning” into a product manifold M3 × MN. Remarkably, the 3-dimensional universe M3 can undergo a rapid de Sitter expansion large enough to solve the horizon and flatness problem. We call this “topological inflation”, which we propose as an alternative to the usual GUT inflation. The inflationary phase automatically terminates into a big bang phase.

The possibility of the charge-monopole systems with half-integer spin in the grand unified SU(5) model is investigated and found to occur.Received 29 February 1980DOI:https://doi.org/10.1103/PhysRevLett.44.1175©1980 American Physical Society

Assuming a heavy electroweak singlet scalar, which couples to the Standard Model gauge bosons only through loop-induced couplings, SU(2)_L x U(1)_Y gauge invariance imposes interesting patterns on its decays into electroweak gauge bosons, which are dictated by only two free parameters. Therefore experimental measurements on any two of the four possible electroweak channels would determine the remaining two decay channels completely. Furthermore, searches in the WW/ZZ channels probe a complimentary region of parameter space from searches in the gamma-gamma/Z-gamma channels. We derive a model-independent upper bound on the branching fraction in each decay channel, which for the diphoton channel turns out to be about 61%. Including the coupling to gluons, the upper bound on the diphoton branching fraction implies an upper bound on the mass scale of additional colored particles mediating the gluon-fusion production. Using an event rate of about 5 fb for the reported 750 GeV diphoton excess, we find the new colored particle must be lighter than O(1.7 TeV) and O(2.6 TeV) for a pure CP-even and a pure CP-odd singlet scalar, respectively.

We explore the possibility of unification of gauge couplings near the Planck scale in models of extended technicolor. We observe that models of the form G X SU(3)_c X SU(2)_L X U(1)_Y cannot be realized, due to the presence of massless neutral Goldstone bosons (axions) and light charged pseudo-Goldstone bosons; thus, unification of the known forces near the Planck scale cannot be achieved. The next simplest possibility, G X SU(4)_{PS} X SU(2)_L X U(1)_{T_{3R}}, cannot lead to unification of the Pati-Salam and weak gauge groups near the Planck scale. However, superstring theory provides relations between couplings at the Planck scale without the need for an underlying grand-unified gauge group, which allows unification of the SU(4)$_{PS}$ and SU(2)$_L$ couplings.

This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 4 discusses options for the linear collider program, at a number of levels. First, it presents a broad review of physics beyond the Standard Model, indicating how the linear collider is relevant to each possible pathway. Next, it surveys options for the accelerator and experimental plan, including the questions of the running scenario, the issue of one or two interaction regions, and the options for positron polarization, photon-photon collisions, and e-e- collisions. Finally, it reviews the detector design issues for the linear collider and presents three possible detector designs.

An elementary review of models and phenomenology for physics beyond the Standard Model (excluding supersymmetry). The emphasis is on LHC physics. Based upon a talk given at the ''Physics at LHC'' conference, Vienna, 13-17 July 2004.