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The ADHM-like Constructions for Instantons on CP^2 and Three Dimensional Gauge Theories
http://cds.cern.ch/record/1695527
We study the moduli spaces of self-dual instantons on CP^2 in a simple group G. When G is a classical group, these instanton solutions can be realised using ADHM-like constructions which can be naturally embedded into certain three dimensional quiver gauge theories with 4 supercharges. The topological data for such instanton bundles and their relations to the quiver gauge theories are described. Based on such gauge theory constructions, we compute the Hilbert series of the moduli spaces of instantons that correspond to various configurations. The results turn out to be equal to the Hilbert series of their counterparts on C^2 upon an appropriate mapping. We check the former against the Hilbert series derived from the blowup formula for the Hirzebruch surface F_1 and find an agreement. The connection between the moduli spaces of instantons on such two spaces is explained in detail.Mekareeya, NoppadolWed, 16 Apr 2014 02:41:13 GMThttp://cds.cern.ch/record/1695527Status of Neutrino Mass and Mixing
http://cds.cern.ch/record/1695520
In the last two decades experiments have established the existence of neutrino oscillations and most of the related parameters have by now been measured with reasonable accuracy. These results have accomplished a major progress for particle physics and cosmology. At present neutrino physics is a most vital domain of particle physics and cosmology and the existing open questions are of crucial importance. We review the present status of the subject, the main lessons that we have learnt so far and discuss the great challenges that remain in this field.Altarelli, GuidoWed, 16 Apr 2014 02:40:11 GMThttp://cds.cern.ch/record/1695520Faraday scaling and the Bicep2 observations
http://cds.cern.ch/record/1695490
As repeatedly speculated in the past, the linear polarization of the Cosmic Microwave Background can be rotated via the Faraday effect. An economic explanation of the recent Bicep2 observations, not relying on long-wavelength tensor modes of the geometry, would stipulate that the detected B mode comes exclusively from a Faraday rotated E mode polarization. We show hereunder that this interpretation is ruled out by the existing upper limits on the B mode polarization obtained by independent experiments at observational frequencies much lower than the operating frequency of the Bicep2 experiment. We then derive the fraction of the observed B mode polarization ascribable to the Faraday effect and suggest a dedicated experimental strategy for its detection.Giovannini, MassimoWed, 16 Apr 2014 02:38:48 GMThttp://cds.cern.ch/record/1695490QCD and strongly coupled gauge theories: challenges and perspectives
http://cds.cern.ch/record/1695448
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly-coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Brambilla, NWed, 16 Apr 2014 02:37:44 GMThttp://cds.cern.ch/record/1695448Complete Higgs Sector Constraints on Dimension-6 Operators
http://cds.cern.ch/record/1695294
Constraints on the full set of Standard Model dimension-6 operators have previously used triple-gauge couplings to complement the constraints obtainable from Higgs signal strengths. Here we extend previous analyses of the Higgs sector constraints by including information from the associated production of Higgs and massive vector bosons (H+V production), which excludes a blind direction allowed by the triple-gauge sector. Kinematic distributions in H+V production provide improved sensitivity to dimension-6 operators, as we illustrate here with simulations of the invariant mass and $p_T$ distributions measured by D0 and ATLAS, respectively. We provide bounds from a global fit to a complete set of CP-conserving operators affecting Higgs physics.Ellis, JohnTue, 15 Apr 2014 02:25:54 GMThttp://cds.cern.ch/record/1695294Tensor B mode and stochastic Faraday mixing
http://cds.cern.ch/record/1695258
Following a recent proposal, the formation of Faraday rotation is treated as a stationary, random and Markovian process. The scalar, vector and tensor modes of the brightness perturbations can all be Faraday rotated even if the vector and tensor parts of the effect have been neglected, so far, by focussing the attention on the scalar aspects of the problem. The mixing between the power spectra of the E mode and B mode polarizations involves a unitary transformation depending nonlinearly on the Faraday rotation rate. The present approach is suitable for a general scrutiny of the polarization observables and of their frequency dependence. It is finally demonstrated that the recently detected B mode cannot be explained by a predominant Faraday rotated E mode polarization since, in this case, the observed temperature autocorrelations would be excessively distorted.Giovannini, MassimoTue, 15 Apr 2014 02:24:58 GMThttp://cds.cern.ch/record/1695258Spectator Effects during Leptogenesis in the Strong Washout Regime
http://cds.cern.ch/record/1694614
By including spectator fields into the Boltzmann equations for Leptogenesis, we show that partially equilibrated spectator interactions can have a significant impact on the freeze-out value of the asymmetry in the strong washout regime. The final asymmetry is typically increased, since partially equilibrated spectators "hide" a part of the asymmetry from washout. We study examples with leptonic and non-leptonic spectator processes, assuming thermal initial conditions, and find up to 50% enhanced asymmetries compared to the limit of fully equilibrated spectators. Together with a comprehensive overview of the equilibration temperatures for various Standard Model processes, the numerical results indicate the ranges when the limiting cases of either fully equilibrated or negligible spectator fields are applicable and when they are not. Our findings also indicate an increased sensitivity to initial conditions and finite density corrections even in the strong washout regime.Garbrecht, BjornFri, 11 Apr 2014 02:37:13 GMThttp://cds.cern.ch/record/1694614Inclusive and pion production neutrino-nucleus cross sections
http://cds.cern.ch/record/1693962
We analyze the experimental data on the inclusive double differential cross section by neutrinos charged current, measured by T2K, with the same model which was successful for the MiniBooNE quasielastic cross sections. As in our previous analysis the multinucleon component is needed in order to reproduce the data. For the total cross section our evaluation is smaller than the SciBooNE data above 1 GeV. This indicates the opening of a new channel not included in our evaluation, presumably the two pion emission channel. We also check that our description holds for the exclusive single pion production channel by confronting our evaluation with the MiniBooNE double differential cross section for a single charged pion and the Q^2 distribution. Both are compatible with data.Martini, MTue, 08 Apr 2014 03:05:34 GMThttp://cds.cern.ch/record/1693962W Symmetry in six dimensions
http://cds.cern.ch/record/1693594
Six-dimensional conformal field theories with $(2,0)$ supersymmetry are shown to possess a protected sector of operators and observables that are isomorphic to a two-dimensional chiral algebra. We argue that the chiral algebra associated to a $(2,0)$ theory labelled by the simply-laced Lie algebra $\mathfrak{g}$ is precisely the W algebra of type $\mathfrak{g}$, for a specific value of the central charge. Simple examples of observables that are made accessible by this correspondence are the three-point functions of half-BPS operators. For the $A_n$ series, we compare our results at large $n$ to those obtained using the holographic dual description and find perfect agreement. We further find protected chiral algebras that appear on the worldvolumes of codimension two defects in $(2,0)$ SCFTs. This construction has likely implications for understanding the microscopic origin of the AGT correspondence.Rastelli, LeonardoMon, 07 Apr 2014 02:26:47 GMThttp://cds.cern.ch/record/1693594Towards precise predictions for Higgs-boson production in the MSSM
http://cds.cern.ch/record/1692791
We study the production of scalar and pseudoscalar Higgs bosons via gluon fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD calculation implemented in the public code SusHi, we provide precise predictions for the Higgs-production cross section in six benchmark scenarios compatible with the LHC searches. We also provide a detailed discussion of the sources of theoretical uncertainty in our calculation. We examine the dependence of the cross section on the renormalization and factorization scales, on the precise definition of the Higgs-bottom coupling and on the choice of PDFs, as well as the uncertainties associated to our incomplete knowledge of the SUSY contributions through NNLO. In particular, a potentially large uncertainty originates from uncomputed higher-order QCD corrections to the bottom-quark contributions to gluon fusion.Harlander, R VWed, 02 Apr 2014 02:34:57 GMThttp://cds.cern.ch/record/1692791Resurrecting Quadratic Inflation in No-Scale Supergravity in Light of BICEP2
http://cds.cern.ch/record/1691136
The magnitude of primordial tensor perturbations reported by the BICEP2 experiment is consistent with simple models of chaotic inflation driven by a single scalar field with a power-law potential \propto \phi^n: n \simeq 2, in contrast to the WMAP and Planck results, which favored models resembling the Starobinsky R + R^2 model if running of the scalar spectral index could be neglected. While models of inflation with a quadratic potential may be constructed in simple N=1 supergravity, these constructions are more challenging in no-scale supergravity. We discuss here how quadratic inflation can be accommodated within supergravity, focussing primarily on the no-scale case. We also argue that the quadratic inflaton may be identified with the supersymmetric partner of a singlet (right-handed) neutrino, whose subsequent decay could have generated the baryon asymmetry via leptogenesis.Garcia, Marcos A GMon, 31 Mar 2014 02:22:15 GMThttp://cds.cern.ch/record/1691136Split SUSY Radiates Flavor
http://cds.cern.ch/record/1689938
Radiative flavor models where the hierarchies of Standard Model (SM) fermion masses and mixings are explained via loop corrections are elegant ways to solve the SM flavor puzzle. Here we build such a model in the context of Mini-Split Supersymmetry (SUSY) where both flavor and SUSY breaking occur at a scale of 1000 TeV. This model is consistent with the observed Higgs mass, unification, and WIMP dark matter. The high scale allows large flavor mixing among the sfermions, which provides part of the mechanism for radiative flavor generation. In the deep UV, all flavors are treated democratically, but at the SUSY breaking scale, the third, second, and first generation Yukawa couplings are generated at tree level, one loop, and two loops, respectively. Save for one, all the dimensionless parameters in the theory are O(1), with the exception being a modest and technically natural tuning that explains both the smallness of the bottom Yukawa coupling and the largeness of the Cabibbo angle.Stolarski, DanielWed, 26 Mar 2014 05:53:09 GMThttp://cds.cern.ch/record/1689938FRW Cosmological Perturbations in Massive Bigravity
http://cds.cern.ch/record/1670744
Cosmological perturbations of FRW solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that sub horizon exponential instabilities are unavoidable and they lead to a premature departure from the perturbative regime of cosmological perturbations.Crisostomi, MTue, 25 Mar 2014 03:37:48 GMThttp://cds.cern.ch/record/1670744The Imaginary Starobinsky Model
http://cds.cern.ch/record/1670433
The recent detection by the BICEP2 collaboration of a high level of tensor modes seems to exclude the Starobinsky model of inflation. In this paper we show that this conclusion can be avoided: one can embed the Starobinsky model in supergravity and identify the inflaton field with the imaginary (instead of the real) part of the chiral scalaron multiplet in its formulation. Once coupled to matter, the Starobinsky model may then become the chaotic quadratic model with shift symmetry during inflation and is in good agreement with the current data.Kehagias, AlexMon, 24 Mar 2014 03:29:50 GMThttp://cds.cern.ch/record/1670433From scale invariance to Lorentz symmetry
http://cds.cern.ch/record/1669952
It is shown that a unitary translationally invariant field theory in (1+1) dimensions satisfying isotropic scale invariance, standard assumptions about the spectrum of states and operators and the requirement that signals propagate with finite velocity possesses Lorentz invariance, and hence the full conformal symmetry.Sibiryakov, SergeyThu, 20 Mar 2014 03:39:07 GMThttp://cds.cern.ch/record/1669952Higgs boson gluon-fusion production at threshold in N3LO QCD
http://cds.cern.ch/record/1669932
We present the cross-section for the threshold production of the Higgs boson at hadron-colliders at next-to-next-to-next-to-leading order (N3LO) in perturbative QCD. We present an analytic expression for the partonic cross-section at threshold and the impact of these corrections on the numerical estimates for the hadronic cross-section at the LHC. With this result we achieve a major milestone towards a complete evaluation of the cross-section at N3LO which will reduce the theoretical uncertainty in the determination of the strengths of the Higgs boson interactions.Duhr, ClaudeThu, 20 Mar 2014 03:38:47 GMThttp://cds.cern.ch/record/1669932Emergent Time and the M5-Brane
http://cds.cern.ch/record/1669734
We consider the maximal super-Yang-Mills theory in 5 Euclidean dimensions with SO(5) R-symmetry and 16 supersymmetries. We argue that the strong coupling limit of this theory (with a possible UV completion) has an emergent time dimension and gives a description of the 5+1 dimensional Lorentz invariant (2,0) theory of the M5-brane, compactified on a timelike circle with radius R=g^2/4\pi^2 . Our discussion involves issues of quantization of Euclidean theories without time.Hull, C MWed, 19 Mar 2014 05:50:46 GMThttp://cds.cern.ch/record/1669734Solving the 3d Ising Model with the Conformal Bootstrap II. c-Minimization and Precise Critical Exponents
http://cds.cern.ch/record/1669709
We use the conformal bootstrap to perform a precision study of the operator spectrum of the critical 3d Ising model. We conjecture that the 3d Ising spectrum minimizes the central charge c in the space of unitary solutions to crossing symmetry. Because extremal solutions to crossing symmetry are uniquely determined, we are able to precisely reconstruct the first several Z2-even operator dimensions and their OPE coefficients. We observe that a sharp transition in the operator spectrum occurs at the 3d Ising dimension Delta_sigma=0.518154(15), and find strong numerical evidence that operators decouple from the spectrum as one approaches the 3d Ising point. We compare this behavior to the analogous situation in 2d, where the disappearance of operators can be understood in terms of degenerate Virasoro representations.Paulos, Miguel FWed, 19 Mar 2014 05:50:04 GMThttp://cds.cern.ch/record/1669709eHDECAY: an Implementation of the Higgs Effective Lagrangian into HDECAY
http://cds.cern.ch/record/1668729
We present eHDECAY, a modified version of the program HDECAY which includes the full list of leading bosonic operators of the Higgs effective Lagrangian with a linear or non-linear realization of the electroweak symmetry and implements two benchmark composite Higgs models.Contino, RobertoFri, 14 Mar 2014 03:57:38 GMThttp://cds.cern.ch/record/1668729The Minimal Volkov - Akulov - Starobinsky Supergravity
http://cds.cern.ch/record/1668687
We construct a supergravity model whose scalar degrees of freedom arise from a chiral superfield and are solely a scalaron and an axion that is very heavy during the inflationary phase. The model includes a second chiral superfield $X$, which is subject however to the constraint $X^2=0$ so that it describes only a Volkov - Akulov goldstino and an auxiliary field. We also construct the dual higher - derivative model, which rests on a chiral scalar curvature superfield ${\cal R}$ subject to the constraint ${\cal R}^2=0$, where the goldstino dual arises from the gauge - invariant gravitino field strength as $\gamma^{mn} {\cal D}_m \psi_n$. The final bosonic action is an $R+R^2$ theory involving an axial vector $A_m$ that only propagates a physical pseudoscalar mode.Dudas, EFri, 14 Mar 2014 03:54:43 GMThttp://cds.cern.ch/record/1668687Coulomb branch Hilbert series and Three Dimensional Sicilian Theories
http://cds.cern.ch/record/1668001
We evaluate the Coulomb branch Hilbert series of mirrors of three dimensional Sicilian theories, which arise from compactifying the $6d$ $(2,0)$ theory with symmetry $G$ on a circle times a Riemann surface with punctures. We obtain our result by gluing together the Hilbert series for building blocks $T_{\mathbf{\rho}}(G)$, where $\mathbf{\rho}$ is a certain partition related to the dual group of $G$, which we evaluated in a previous paper. The result is expressed in terms of a class of symmetric functions, the Hall-Littlewood polynomials. As expected from mirror symmetry, our results agree at genus zero with the superconformal index prediction for the Higgs branch Hilbert series of the Sicilian theories and extend it to higher genus. In the $A_1$ case at genus zero, we also evaluate the Coulomb branch Hilbert series of the Sicilian theory itself, showing that it only depends on the number of external legs.Hanany, AmihayWed, 12 Mar 2014 04:24:46 GMThttp://cds.cern.ch/record/1668001Characterizing New Physics with Polarized Beams at High-Energy Hadron Colliders
http://cds.cern.ch/record/1667973
The TeV energy region is currently being explored by both the ATLAS and CMS experiments of the Large Hadron Collider and phenomena beyond the Standard Model are extensively searched for. Large fractions of the parameter space of many models have already been excluded, and the ranges covered by the searches will certainly be increased by the upcoming energy and luminosity upgrades. If new physics has to be discovered in the forthcoming years, the ultimate goal of the high-energy physics program will consist of fully characterizing the newly-discovered degrees of freedom in terms of properties such as their masses, spins and couplings. The scope of this paper is to show how the availability of polarized beams at high-energy proton-proton colliders could yield a unique discriminating power between different beyond the Standard Model scenarios. We first discuss in a model-independent way how this discriminating power arises from the differences between polarized and unpolarized parton distribution functions. We then demonstrate how polarized beams allow one not only to disentangle different production mechanisms giving the same final-state signature, but also to obtain information on the parameters of the hypothetical new physics sector of the theory. This is illustrated in the case of a particular class of scenarios leading to monotop production. We consider three specific models that could produce a monotop signature in unpolarized proton collisions, and show how they could be distinguished by means of single- and double-spin asymmetries in polarized collisions. Our results are presented for both the Large Hadron Collider operating at a center-of-mass energy of 14 TeV and a recently proposed Future Circular Collider assumed to collide protons at a center-of-mass energy of 100 TeV.Proudom, JosselinWed, 12 Mar 2014 04:20:45 GMThttp://cds.cern.ch/record/1667973Enhancing the ttH signal through top-quark spin polarization effects at the LHC
http://cds.cern.ch/record/1667315
We compare the impact of top-quark spin polarization effects in Higgs boson production in association with top-quark pairs and in corresponding backgrounds at the LHC. Because of the spin-zero nature of the Higgs boson, one expects, in the chiral limit for the top quarks, a substantial complementarity in $t\bar t$ spin correlations for a Higgs decaying into fermions/gauge-bosons and $t\bar{t}$ spin correlations for the corresponding irreducible $t\bar t f\bar f/VV$ backgrounds. Although top mass effects in $t\bar t H$ production are in general dominant, and seriously spoil the chiral-limit expectations, one can find observables that capture the $t \bar t$ angular spin correlations and can help in separating the signal from irreducible backgrounds. In particular, we show that, for both $H\to b\bar b$ and $H\to \gamma\gamma$, taking into account $t\bar{t}$ spin correlations in $t\bar t H$ production and irreducible backgrounds could appreciably improve the LHC sensitivity to the $t\bar t H$ channel.Frederix, RMon, 10 Mar 2014 03:36:27 GMThttp://cds.cern.ch/record/1667315Gauged R-symmetry and de Sitter vacua in supergravity and string theory
http://cds.cern.ch/record/1666971
A new class of metastable de Sitter vacua is presented and analyzed in N =1 supergravity and string theory with tunable (infinitesimally small) value of the cosmological constant. They are based on a gauged R-symmetry and the minimal spectrum contains a vector and a linear multiplet of the string dilaton or of a compactification modulus. In the minimum of the scalar potential supersymmetry is broken by an expectation value of both a D- and F-term.Knoops, RobFri, 07 Mar 2014 03:28:55 GMThttp://cds.cern.ch/record/1666971Coulomb branch Hilbert series and Hall-Littlewood polynomials
http://cds.cern.ch/record/1666649
There has been a recent progress in understanding the chiral ring of 3d $\mathcal{N}=4$ superconformal gauge theories by explicitly constructing an exact generating function (Hilbert series) counting BPS operators on the Coulomb branch. In this paper we introduce Coulomb branch Hilbert series in the presence of background magnetic charges for flavor symmetries, which are useful for computing the Hilbert series of more general theories through gluing techniques. We find a simple formula of the Hilbert series with background magnetic charges for $T_\rho(G)$ theories in terms of Hall-Littlewood polynomials. Here $G$ is a classical group and $\rho$ is a certain partition related to the dual group of $G$. The Hilbert series for vanishing background magnetic charges show that Coulomb branches of $T_\rho(G)$ theories are complete intersections. We also demonstrate that mirror symmetry maps background magnetic charges to baryonic charges.Hanany, AmihayWed, 05 Mar 2014 04:20:09 GMThttp://cds.cern.ch/record/1666649