5148649
On N = 2 supersymmetric QCD with four flavors
Seiberg and Witten's proposed solution of N = 2 SQCD with Nc = 2 and NF = 4 is known to conflict with instanton calculations in three distinct ways. Here we show how to resolve all three discrepancies, simply by reparametrizing the elliptic curve in terms of quantities τeff(0) and u rather than τ and u = 〈Tr A2〉. SL(2,Z) invariance of the curve is preserved. However, there is now an infinite ambiguity in the relation between τeff(0) and τ and between u and u, corresponding to an infinite number of unknown coefficients in the instanton expansion. Thus the reinterpreted curve (unlike the cases NF < 4) no longer determines the quantum modulus u as a function of the classical VEV a.
34905319
Minkowski space non-Abelian classical solutions with noninteger winding number change.
Working in a spherically symmetric ansatz in Minkowski space, we discover new solutions to the classical equations of motion of pure SU(2) gauge theory. These solutions represent spherical shells of energy, which move inward near the speed of light at early times, excite the region of space around the origin at intermediate times, and move outward at late times. The solutions change the winding number in bounded regions centered at the origin by noninteger amounts. They also produce a noninteger topological charge in these regions. We show that the previously discovered solutions of Luescher and Schechter also have these properties.
119236962
Travels on the squark-gluino mass plane
Institut fur Theoretische Physik, Universitat Heidelberg, Germany(Dated: September 12, 2011)Soft supersymmetry breaking appears in the weak-scale e ective action but is usually generated athigher scales. For these models the structure of the renormalization group evolution down to theelectroweak scale leaves only part of the squark-gluino and slepton-gaugino mass planes accessible.Our observations divide these physical mass planes into three wedges: the rst can be reached byall models of high-scale breaking; the second can only be populated by models with a low mediationscale; in the third wedge squarks and gluinos would have to be described by an exotic theory. Allusual benchmark points reside in the rst wedge, even though an LHC discovery in the third wedge
14098895
Gluino condensate and magnetic monopoles in supersymmetric gluodynamics
We examine supersymmetric SU(N) gauge theories on R3 × S1 with a circle of circumference β. These theories interpolate between four-dimensional N = 1 pure gauge theory for β = ∞ and three-dimensional N = 2 gauge theory for β = 0. The dominant field configurations of the R3 × S1 SU(N) theories in the semi-classical regime arise from N varieties of monopole. Periodic instanton configurations correspond to mixed configurations of N single monopoles of the N different types. We semi-classically evaluate the non-perturbatively generated superpotential of the R3 × S1 theory and hence determine its vacuum structure. to the gluino condensate in these theories and take the decompactification limit β = ∞. In this way we obtain a value for the gluino condensate in the four-dimensional N = 1 supersymmetric SU(N) Yang-Mills theory, which agrees with the previously known ‘weak coupling’ expression but not with the ‘strong coupling’ expression derived in the early literature solely from instanton considerations. Moreover, we discover that the superpotential gives a mass to the dual (magnetic) photon, which implies confinement of the original electric photon and disappearance of all the massless modes.
119447895
Multi-gluon collinear limits from MHV diagrams
We consider the multi-collinear limit of multi-gluon QCD amplitudes at tree level. We use the MHV rules for constructing colour ordered tree amplitudes and the general collinear factorization formula to derive timelike splitting functions that are valid for specific numbers of negative helicity gluons and an arbitrary number of positive helicity gluons (or vice versa). As an example we present new results describing the collinear limits of up to six gluons.
119379193
The calculus of many instantons
We describe the modern formalism, ideas and applications of the instanton calculus for gauge theories with, and without, supersymmetry. Particular emphasis is put on developing a formalism that can deal with any number of instantons. This necessitates a thorough review of the ADHM construction of instantons with arbitrary charge and an in-depth analysis of the resulting moduli space of solutions. We review the construction of the ADHM moduli space as a hyper-Kahler quotient. We show how the functional integral in the semi-classical approximation reduces to an integral over the instanton moduli space in each instanton sector and how the resulting matrix partition function involves various geometrical quantities on the instanton moduli space: volume form, connection, curvature, isometries, etc. One important conclusion is that this partition function is the dimensional reduction of a higher- dimensional gauged linear sigma model which naturally leads us to describe the relation of the instanton calculus to D-branes in string theory. Along the way we describe powerful applications of the calculus of many instantons to supersymmetric gauge theories including (i) the gluino condensate puzzle in N = 1 theories (ii) Seiberg-Witten theory in N = 2 theories; and (iii) the AdS/CFT correspondence in N = 2 and N = 4 theories. Finally, we brielfy review the modifications of the instanton calculus for a gauge theory defined on a non-commutative spacetime and we also describe a new method for calculating instanton processes using a form of localization on the instanton moduli space.
119444664
Physics with forward protons at hadron colliders
We emphasize the importance of tagging the outgoing forward protons to sharpen the predictions for New Physics at the LHC. We show that exclusive double-diffractive Higgs production, pp ⇒ p + H + p , followed by the H → bb decay, could play an important role in identifying a ‘light’ Higgs boson.
15910996
Diffractive dissociation re-visited for predictions at the LHC
AbstractWe describe the formalism and present the results for a triple-Regge analysis of the available pp and 
$p\bar{p}$ 
high-energy data which explicitly account for absorptive corrections. In particular, we allow for the gap survival probability, S2, in single-proton diffractive dissociation. Since for pp scattering the value of S2 is rather small, the triple-pomeron vertex obtained in this analysis is larger than that obtained in the old analyses where the suppression caused by the absorptive corrections was implicitly included in an effective vertex. We show that the bare triple-pomeron coupling that we extract from the pp and 
$p\bar{p}$ 
data is consistent with that obtained in a description of the γp→J/ψ+Y HERA data. The analyses of the data prefer a zero slope, corresponding to the small size of the bare vertex, giving the hope of a smooth matching to the perturbative QCD treatment of the triple-pomeron coupling.
120416191
Stop near threshold
Abstract The observation that perturbative QCD suffices to describe threshold production of heavy particles if their decay width is sufficiently large is extended to SUSY particles: the production of squarks — and there in particular of stops — and of gluinos is analyzed, both for e + e − annihilation and hadronic collisions. Some qualitatively new features — like intrinsic limitations to a non-relativistic treatment of P wave production — are pointed out and discussed.
120061643
Physics of Top and {CP} Violation in $B$ Decays in the Light of the Argus Measurements
Implications of the significant mixing, observed by the ARGUS collaboration, on our present understanding of nature are discussed. Our emphasis is on the consequences of the standard model with a heavy top quark. We discuss also the future prospects of the observation of CP violation in B decays.
15306416
Hadronic returns to the Z in electron positron annihilation at high-energy
The production of four hadronic jets in e+e− collisions above the Z pole is dominated by the QCD e+e−→qq,qgg processes and, for sufficiently high energy, the electroweak e+e−→W+W−→qq process. However, there is another mechanism for producing four jets, e+e−→Zgg→qgg, which can be regarded as a ``hadronic return'' to the Z pole. We investigate this process in detail.