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Resurgent Analysis of Localizable Observables in Supersymmetric Gauge Theories
http://cds.cern.ch/record/1956995
Localization methods have recently led to a plethora of new exact results in supersymmetric gauge theories, as certain observables may be computed in terms of matrix integrals. These can then be evaluated by making use of standard large N techniques, or else via perturbative expansions in the gauge coupling. Either approximation often leads to observables given in terms of asymptotic series, which need to be properly defined in order to obtain nonperturbative results. At the same time, resurgent analysis has recently been successfully applied to several problems, e.g., in quantum, field and string theories, precisely to overcome this issue and construct nonperturbative answers out of asymptotic perturbative expansions. The present work uses exact results from supersymmetric localization to address the resurgent structure of the free energy and partition function of Chern-Simons and ABJM gauge theories in three dimensions, and of N=2 supersymmetric Yang-Mills theories in four dimensions. For each case, the complete structure of Borel singularities is exactly determined, and the relation of these singularities with the large-order behavior of (multi-instanton) perturbative expansions is made fully precise.Aniceto, InêsThu, 23 Oct 2014 05:58:55 GMThttp://cds.cern.ch/record/1956995Matching the $D^6 {\cal R}^4$ interaction at two-loops
http://cds.cern.ch/record/1956983
The coefficient of the $D^6 {\cal R}^4$ interaction in the low energy expansion of the two-loop four-graviton amplitude in type II superstring theory is known to be proportional to the integral of the Zhang-Kawazumi (ZK) invariant over the moduli space of genus-two Riemann surfaces. We demonstrate that the ZK invariant is an eigenfunction with eigenvalue 5 of the Laplace-Beltrami operator in the interior of moduli space. Exploiting this result, we evaluate the integral of the ZK invariant explicitly, finding agreement with the value of the two-loop $D^6 {\cal R}^4$ interaction predicted on the basis of S-duality and supersymmetry. A review of the current understanding of the $D^{2p} {\cal R}^4$ interactions in type II superstring theory compactified on a torus $T^d$ with $p \leq 3$ and $d \leq 4$ is included.D'Hoker, EricThu, 23 Oct 2014 05:58:52 GMThttp://cds.cern.ch/record/1956983Exploring CP Violation in the MSSM
http://cds.cern.ch/record/1956033
We explore the prospects for observing CP violation in the minimal supersymmetric extension of the Standard Model (MSSM) with six CP-violating parameters, three gaugino mass phases and three phases in trilinear soft supersymmetry-breaking parameters, using the CPsuperH code combined with a geometric approach to maximize CP-violating observables subject to the experimental upper bounds on electric dipole moments. We also implement CP-conserving constraints from Higgs physics, flavour physics and the upper limits on the cosmological dark matter density and spin-independent scattering. We study possible values of observables within the constrained MSSM (CMSSM), the non-universal Higgs model (NUHM), the CPX scenario and a variant of the phenomenological MSSM (pMSSM). We find values of the CP-violating asymmetry A_CP in b -> s gamma decay that may be as large as 3%, so future measurements of A_CP may provide independent information about CP violation in the MSSM. We find that CP-violating MSSM contributions to the B_s meson mass mixing term Delta M_Bs are in general below the present upper limit, which is dominated by theoretical uncertainties. If these could be reduced, Delta M_Bs could also provide an interesting and complementary constraint on the six CP-violating MSSM phases, enabling them all to be determined experimentally, in principle. We also find that CP violation in the h_{2,3} tau+ tau- and h_{2,3} tbar t couplings can be quite large, and so may offer interesting prospects for future pp, e+ e-, mu+ mu- and gamma gamma colliders.Arbey, AMon, 20 Oct 2014 06:00:34 GMThttp://cds.cern.ch/record/1956033Global fits to b -> s ll data and signs for lepton non-universality
http://cds.cern.ch/record/1955758
There are some slight tensions with the SM predictions within the latest LHCb measurements. Besides the known anomaly in one angular observable of the rare decay B -> K* mu+ mu-, another slight discrepancy recently occurred. The ratio R_K = BR(B+ -> K+ mu+ mu-) / BR(B+ -> K+ e+ e-) in the low-q^2 region has been measured by LHCb showing a 2.6 sigma deviation from the SM prediction. In contrast to the anomaly in the rare decay B -> K* mu+ mu- which is affected by power corrections, the ratio R_K is theoretically rather clean. We analyse all the b -> s ll data with global fits and in particular explore the possibility of breaking of lepton universality. Possible cross-checks with an analysis of the inclusive B -> X_s l+ l- decay are also explored.Hurth, TFri, 17 Oct 2014 05:43:19 GMThttp://cds.cern.ch/record/1955758An Introduction to PYTHIA 8.2
http://cds.cern.ch/record/1955026
The PYTHIA program is a standard tool for the generation of events in high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard process to a complex multiparticle final state. It contains a library of hard processes, models for initial- and final-state parton showers, matching and merging methods between hard processes and parton showers, multiparton interactions, beam remnants, string fragmentation and particle decays. It also has a set of utilities and several interfaces to external programs. PYTHIA 8.2 is the second main release after the complete rewrite from Fortran to C++, and now has reached such a maturity that it offers a complete replacement for most applications, notably for LHC physics studies. The many new features should allow an improved description of data.Sjöstrand, TorbjörnTue, 14 Oct 2014 06:02:54 GMThttp://cds.cern.ch/record/1955026New features of MadAnalysis 5 for analysis design and reinterpretation
http://cds.cern.ch/record/1954609
We present MadAnalysis 5, an analysis package dedicated to phenomenological studies of simulated collisions occurring in high-energy physics experiments. Within this framework, users are invited, through a user-friendly Python interpreter, to implement physics analyses in a very simple manner. A C++ code is then automatically generated, compiled and executed. Very recently, the expert mode of the program has been extended so that analyses with multiple signal/control regions can be handled. Additional observables have also been included, and an interface to several fast detector simulation packages has been developed, one of them being a tune of the Delphes 3 software. As a result, a recasting of existing ATLAS and CMS analyses can be achieved straightforwardly.Conte, EricMon, 13 Oct 2014 05:46:28 GMThttp://cds.cern.ch/record/1954609Completing Lorentz violating massive gravity at high energies
http://cds.cern.ch/record/1954361
Theories with massive gravitons are interesting for a variety of physical applications, ranging from cosmological phenomena to holographic modeling of condensed matter systems. To date, they have been formulated as effective field theories with a cutoff proportional to a positive power of the graviton mass m_g and much smaller than that of the massless theory (M_P ~ 10^19 GeV in the case of general relativity). In this paper we present an ultraviolet completion for massive gravity valid up to a high energy scale independent of the graviton mass. This is achieved by the introduction of vectors fields that develop condensates and spontaneously break the product of internal and space-time symmetries to a diagonal subgroup. The perturbations of these fields are massive and below their mass the theory reduces to a model of Lorentz violating massive gravity. The latter theory possesses instantaneous modes whose consistent quantization we discuss in detail. We briefly study some modifications to gravitational phenomenology at low-energies. The homogeneous cosmological solutions are the same as in the standard cosmology. The gravitational potential of point sources agrees with the Newtonian one at distances small with respect to m_g^(-1). Interestingly, it becomes repulsive at larger distances.Blas, DiegoSat, 11 Oct 2014 05:26:59 GMThttp://cds.cern.ch/record/1954361T^{\sigma}_{\rho}(G) Theories and Their Hilbert Series
http://cds.cern.ch/record/1953927
We give an explicit formula for the Higgs and Coulomb branch Hilbert series for the class of 3d N=4 superconformal gauge theories T^{\sigma}_{\rho}(G) corresponding to a set of D3 branes ending on NS5 and D5-branes, with or without O3 planes. Here G is a classical group, \sigma is a partition of G and \rho a partition of the dual group G^\vee. In deriving such a formula we make use of the recently discovered formula for the Hilbert series of the quantum Coulomb branch of N=4 superconformal theories. The result can be expressed in terms of a generalization of a class of symmetric functions, the Hall-Littlewood polynomials, and can be interpreted in mathematical language in terms of localization. We mainly consider the case G=SU(N) but some interesting results are also given for orthogonal and symplectic groups.Cremonesi, StefanoThu, 09 Oct 2014 06:26:33 GMThttp://cds.cern.ch/record/1953927Deformations of infrared-conformal theories in two dimensions
http://cds.cern.ch/record/1953098
We study two exactly solvable two-dimensional conformal models, the critical Ising model and the Sommerfield model, on the lattice. We show that finite-size effects are important and depend on the aspect ratio of the lattice. In particular, we demonstrate how to obtain the correct massless behavior from an infinite tower of finite-size-induced masses and show that it is necessary to first take the cylindrical geometry limit in order to get correct results. In the Sommerfield model we also introduce a mass deformation to measure the mass anomalous dimension, $\gamma_m$. We find that the explicit scale breaking of the lattice setup induces corrections which must be taken into account in order to reproduce $\gamma_m$ at the infrared fixed point. These results can be used to improve the methodology in the search for the conformal window in QCD-like theories with many flavors.Akerlund, OscarTue, 07 Oct 2014 05:29:02 GMThttp://cds.cern.ch/record/1953098Lattice gauge theory without link variables
http://cds.cern.ch/record/1951631
We obtain a sequence of alternative representations for the partition function of pure SU(N) or U(N) lattice gauge theory with the Wilson plaquette action, using the method of Hubbard-Stratonovich transformations. In particular, we are able to integrate out all the link variables exactly, and recast the partition function of lattice gauge theory as a Gaussian integral over auxiliary fields.Vairinhos, HelvioThu, 02 Oct 2014 05:59:42 GMThttp://cds.cern.ch/record/1951631Natural Braneworld Inflation in Light of Results from Planck and BICEP2
http://cds.cern.ch/record/1951523
In this paper we report on a major theoretical observation in cosmology. We present a concrete cosmological model for which inflation has natural beginning and natural ending. Inflation is driven by a cosine-form potential, $V(\phi)= \Lambda^4 (1-\cos(\phi/f))$, which begins at $\phi \lesssim \pi f$ and ends at $\phi =\phi_{\rm end} \lesssim 5 f/3$. The distance traversed by the inflaton field $\phi$ is sub-Planckian. The Gauss-Bonnet term ${\cal R}^2$ arising as leading curvature corrections in the action $S = \int d^5{x} \sqrt{-g_{5}} M^3 (- 6\lambda M^2 + R + \alpha M^{-2} {\cal R}^2)+ \int d^{4}x \sqrt{-g_{4}} (\dot{\phi}^2/2 - V(\phi)- \sigma +{\cal L}_{\text matter})$ (where $\alpha$ and $\lambda$ are constants and $M$ is the five-dimensional Planck mass) plays a key role to terminate inflation. The model generates appropriate tensor-to-scalar ratio $r$ and inflationary perturbations that are consistent with results from \textit{Planck} and BICEP2. For example, for $N_*= 50-60$ and $n_s\sim 0.960\pm 0.005$, the model predicts that $M\sim 5.64\times 10^{16}\,{\rm GeV}$ and $r\sim (0.14-0.21)$ ($N_*$ is the number of e-folds of inflation and $n_s$ ($n_{t}$) is the scalar (tensor) spectrum spectral index). The ratio $-n_t/r$ is (13 -- 24)% less than its value in 4D Einstein gravity, $-n_t/r=1/8$. The upper bound on the energy scale of inflation $V^{1/4}=2.37\times 10^{16}\,{\text GeV}$ ($r<0.27$) implies that $(-\lambda \alpha) \gtrsim 75 \times 10^{-5}$ and $\Lambda<2.17\times 10^{16}\,{\text GeV}$, which thereby rule out the case $\alpha=0$ (Randall-Sundrum model). The true nature of gravity is holographic as implied by braneworld realisation of string and M theory. The model correctly predicts a late epoch cosmic acceleration with the dark energy equation of state ${\text w}_{\text DE}\approx -1$.Neupane, Ishwaree PThu, 02 Oct 2014 05:56:32 GMThttp://cds.cern.ch/record/1951523Two-Field Analysis of No-Scale Supergravity Inflation
http://cds.cern.ch/record/1951105
Since the building-blocks of supersymmetric models include chiral superfields containing pairs of effective scalar fields, a two-field approach is particularly appropriate for models of inflation based on supergravity. In this paper, we generalize the two-field analysis of the inflationary power spectrum to supergravity models with arbitrary K\"ahler potential. We show how two-field effects in the context of no-scale supergravity can alter the model predictions for the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$, yielding results that interpolate between the Planck-friendly Starobinsky model and BICEP2-friendly predictions. In particular, we show that two-field effects in a chaotic no-scale inflation model with a quadratic potential are capable of reducing $r$ to very small values $\ll 0.1$. We also calculate the non-Gaussianity measure $f_{\rm NL}$, finding that is well below the current experimental sensitivity.Ellis, JohnTue, 30 Sep 2014 05:33:36 GMThttp://cds.cern.ch/record/1951105On the consistent use of Constructed Observables
http://cds.cern.ch/record/1950761
We define "constructed observables" as relating experimental measurements to terms in a Lagrangian while simultaneously making assumptions about possible deviations from the Standard Model (SM), in other Lagrangian terms. Ensuring that the SM effective field theory (EFT) is constrained correctly when using constructed observables requires that their defining conditions are imposed on the EFT in a manner that is consistent with the equations of motion. Failing to do so can result in a "functionally redundant" operator basis and the wrong expectation as to how experimental quantities are related in the EFT. We illustrate the issues involved considering the $\rm S$ parameter and the off shell triple gauge coupling (TGC) verticies. We show that the relationships between $h \rightarrow V \bar{f} \, f$ decay and the off shell TGC verticies are subject to these subtleties, and how the connections between these observables vanish in the limit of strong bounds due to LEP. The challenge of using constructed observables to consistently constrain the Standard Model EFT is only expected to grow with future LHC data, as more complex processes are studied.Trott, MichaelMon, 29 Sep 2014 05:34:29 GMThttp://cds.cern.ch/record/1950761Higgs production in association with bottom quarks
http://cds.cern.ch/record/1756681
We study the production of a Higgs boson in association with bottom quarks in hadronic collisions, and present phenomenological predictions relevant to the 13 TeV LHC. Our results are accurate to the next-to-leading order in QCD, and matched to parton showers through the MC@NLO method; thus, they are fully differential and based on unweighted events, which we shower by using both Herwig++ and Pythia8. We perform the computation in both the four-flavour and the five-flavour schemes, whose results we compare extensively at the level of exclusive observables. In the case of the Higgs transverse momentum, we also consider the analytically-resummed cross section up to the NNLO+NNLL accuracy. In addition, we analyse at ${\cal O}(\alpha_S^3)$ the effects of the interference between the $b\bar{b}H$ and gluon-fusion production modes.Wiesemann, MFri, 19 Sep 2014 06:15:05 GMThttp://cds.cern.ch/record/1756681$tt^*$ equations, localization and exact chiral rings in 4d N=2 SCFTs
http://cds.cern.ch/record/1756083
We compute exact 2- and 3-point functions of chiral primaries in four-dimensional N=2 superconformal field theories, including all perturbative and instanton contributions. We demonstrate that these correlation functions are nontrivial and satisfy exact differential equations with respect to the coupling constants. These equations are the analogue of the $tt^*$ equations in two dimensions. In the SU(2) N=2 SYM theory coupled to 4 hypermultiplets they take the form of a semi-infinite Toda chain. We provide the complete solution of this chain using input from supersymmetric localization. To test our results we calculate the same correlation functions independently using Feynman diagrams up to 2-loops and we find perfect agreement up to the relevant order. As a spin-off, we perform a 2-loop check of the recent proposal of arXiv:1405.7271 that the logarithm of the sphere partition function in N=2 SCFTs determines the K\"ahler potential of the Zamolodchikov metric on the conformal manifold. We also present the $tt^*$ equations in general SU(N) N=2 superconformal QCD theories and comment on their structure and implications.Baggio, MarcoWed, 17 Sep 2014 05:55:03 GMThttp://cds.cern.ch/record/1756083Exact correlation functions in SU(2) N=2 superconformal QCD
http://cds.cern.ch/record/1756059
We report an exact solution of 2- and 3-point functions of chiral primary fields in SU(2) N=2 super-Yang-Mills theory coupled to four hypermultiplets. It is shown that these correlation functions are non-trivial functions of the gauge coupling, obeying differential equations which take the form of the semi-infinite Toda chain. We solve these equations recursively in terms of the Zamolodchikov metric that can be determined exactly from supersymmetric localization on the four-sphere. Our results are verified independently in perturbation theory with a Feynman diagram computation up to 2-loops. This is a short version of a companion paper that contains detailed technical remarks, additional material and aspects of an extension to SU(N) gauge group.Baggio, MarcoWed, 17 Sep 2014 05:54:39 GMThttp://cds.cern.ch/record/1756059The Discovery of the Gluon
http://cds.cern.ch/record/1756020
Soon after the postulation of quarks, it was suggested that they interact via gluons, but direct experimental evidence was lacking for over a decade. In 1976, Mary Gaillard, Graham Ross and the author suggested searching for the gluon via 3-jet events due to gluon bremsstrahlung in $e^+ e^-$ collisions. Following our suggestion, the gluon was discovered at DESY in 1979 by TASSO and the other experiments at the PETRA collider.Ellis, JohnWed, 17 Sep 2014 05:53:32 GMThttp://cds.cern.ch/record/1756020Interplay and Characterization of Dark Matter Searches at Colliders and in Direct Detection Experiments
http://cds.cern.ch/record/1756012
In this White Paper we present and discuss a concrete proposal for the consistent interpretation of Dark Matter searches at colliders and in direct detection experiments. Based on a specific implementation of simplified models of vector and axial-vector mediator exchanges, this proposal demonstrates how the two search strategies can be compared on an equal footing.Malik, SarahWed, 17 Sep 2014 05:53:31 GMThttp://cds.cern.ch/record/1756012On holography for (pseudo-)conformal cosmology
http://cds.cern.ch/record/1755912
We propose a holographic dual for (pseudo-)conformal cosmological scenario, with a scalar field that forms a moving domain wall in adS_5. The domain wall separates two vacua with unequal energy densities. Unlike in the existing construction, the 5d solution is regular in the relevant space-time domain.Libanov, MWed, 17 Sep 2014 05:52:12 GMThttp://cds.cern.ch/record/1755912N=4 superconformal Ward identities for correlation functions
http://cds.cern.ch/record/1754745
In this paper we study the four-point correlation function of the energy-momentum supermultiplet in theories with N=4 superconformal symmetry in four dimensions. We present a compact form of all component correlators as an invariant of a particular abelian subalgebra of the N=4 superconformal algebra. This invariant is unique up to a single function of the conformal cross-ratios which is fixed by comparison with the correlation function of the lowest half-BPS scalar operators. Our analysis is independent of the dynamics of a specific theory, in particular it is valid in N=4 super Yang-Mills theory for any value of the coupling constant. We discuss in great detail a subclass of component correlators, which is a crucial ingredient for the recent study of charge-flow correlations in conformal field theories. We compute the latter explicitly and elucidate the origin of the interesting relations among different types of flow correlations previously observed in arXiv:1309.1424.Belitsky, A VWed, 10 Sep 2014 05:36:59 GMThttp://cds.cern.ch/record/1754745Ambient cosmology and spacetime singularities
http://cds.cern.ch/record/1754677
We present a new approach to the issues of spacetime singularities and cosmic censorship in general relativity. This is based on asymptotically splitting 5-dimensional bulk space that has standard 4-dimensional spacetime as its boundary geometry, and constructing a unique, complete, smooth 'ambient' metric which has the latter as its conformal infinity. We then find that the existence of spacetime singularities is intimately linked to breaking the boundary conformal structure, while the 5-dimensional metric is only sensitive to conformal infinity without singular points. It follows that uniqueness of the ambient cosmological metric crucially depends on cosmic censorship holding on the boundary.Antoniadis, IgnatiosWed, 10 Sep 2014 05:35:18 GMThttp://cds.cern.ch/record/1754677A Cheap Alternative to the Lattice?
http://cds.cern.ch/record/1754001
We show how to perform accurate, nonperturbative and controlled calculations in quantum field theory in d dimensions. We use the Truncated Conformal Space Approach (TCSA), a Hamiltonian method which exploits the conformal structure of the UV fixed point. The theory is regulated in the IR by putting it on a sphere of a large finite radius. The QFT Hamiltonian is expressed as a matrix in the Hilbert space of CFT states. After restricting ourselves to energies below a certain UV cutoff, an approximation to the spectrum is obtained by numerical diagonalization of the resulting finite-dimensional matrix. The cutoff dependence of the results can be computed and efficiently reduced via a renormalization procedure. We work out the details of the method for the phi^4 theory in d dimensions with d not necessarily integer. A numerical analysis is then performed for the specific case d = 2.5, a value chosen in the range where UV divergences are absent. By going from weak to intermediate to strong coupling, we are able to observe the symmetry-preserving, symmetry-breaking, and conformal phases of the theory, and perform rough measurements of masses and critical exponents. As a byproduct of our investigations we find that both the free and the interacting theories in non integral d are not unitary, which however does not seem to cause much effect at low energies.Hogervorst, MatthijsMon, 08 Sep 2014 05:25:58 GMThttp://cds.cern.ch/record/1754001Alpha- and Omega-Deformations from fluxes in M-Theory
http://cds.cern.ch/record/1753681
We discuss an SL(2,R) family of deformed N=2 four-dimensional gauge theories which we derive from a flux background in M-theory. In addition to the Omega-deformation this family includes a new deformation, which we call the Alpha-deformation, which can be viewed as an S-dual to the Omega-deformation. We study these gauge theories in two ways: by constructing a non-Abelian (but UV-complete) Lagrangian, and by their strong coupling lift to M-theory where their low-energy dynamics can be determined by examining the equation of motion of a single M5-brane wrapped on a Riemann surface.Lambert, NeilFri, 05 Sep 2014 05:35:29 GMThttp://cds.cern.ch/record/1753681Challenges for New Physics in the Flavour Sector
http://cds.cern.ch/record/1753632
In these proceedings I present a personal perspective of the challenges for new physics (NP) searches in the flavour sector. Since the CKM mechanism of flavour violation has been established to a very high precision, we know that physics beyond the Standard Model can only contribute sub-dominantly. Therefore, any realistic model of physics beyond the Standard Model (SM) must respect the stringent constrains from flavour observables like $b\to s \gamma$, $B_s\to\mu^+\mu^-$, $\Delta F=2$ processes etc., in a first step. In a second step, it is interesting to ask the question if some deviations from the SM predictions (like the anomalous magnetic moment of the muon or recently observed discrepancies in tauonic $B$ decays or $B\to K^*\mu^+\mu^-$) can be explained by a model of NP without violating bounds from other observables.Crivellin, AndreasFri, 05 Sep 2014 05:34:21 GMThttp://cds.cern.ch/record/1753632Transverse momentum resummation for Higgs production via gluon fusion in the MSSM
http://cds.cern.ch/record/1753256
The resummed transverse momentum distribution of supersymmetric Higgs bosons produced through gluon fusion at NLO+NLL is presented, including the exact quark and squark mass dependences. Considering various MSSM scenarios, we compare our results to previous ones within the POWHEG approach. We analyze the impact of the bottom loop which becomes the dominant contribution to the gluon fusion cross section for a wide range of the parameter space for the pseudo-scalar and heavy Higgs.Harlander, Robert VWed, 03 Sep 2014 05:46:04 GMThttp://cds.cern.ch/record/1753256