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Determining the CP nature of spin-0 mediators in associated production of dark matter and $t \bar t$ pairs
http://cds.cern.ch/record/2236681
In the framework of spin-0 $s$-channel simplified models, we explore the possibility of assessing the structure of dark matter interactions through the associate production of dark matter and $t\bar{t}$ pairs. To this purpose, final states with two leptons are considered and the kinematic properties of the dilepton system is studied. We develop a realistic analysis strategy and provide a detailed evaluation of the achievable sensitivity for the dark matter signal assuming integrated luminosities of $300 \, {\rm fb}^{-1}$ and $3 \, {\rm ab}^{-1}$ at the 14 TeV LHC. Furthermore, upper limits on the mediator masses for which the two different CP hypotheses can be distinguished are derived. The obtained limits on the signal strengths are finally translated into constraints on the parameter space of two spin-0 simplified models including a scenario with an extended Higgs sector.Haisch, UlrichPani, PriscillaPolesello, GiacomoFri, 02 Dec 2016 11:44:23 GMT29 Nov 2016arXiv:1611.09841http://cds.cern.ch/record/2236681['arXiv:1611.09841']arXiv:1611.09841Phenomenological analysis of associated production of $Z^0+b$ in the $b \rightarrow J/\psi X$ decay channel at the LHC
http://cds.cern.ch/record/2236670
The ATLAS collaboration recently reported on the first observation of associated-production of a $Z^0$ boson with a $J/\psi$. We recently claimed that the corresponding yield of the {\it prompt} $J/\psi$ was dominated by double parton scatterings in the ATLAS acceptance with a somewhat small value of $\sigma_{\rm eff}$. We also found out that single parton scatterings were only dominant at large transverse momenta. We present here the first phenomenological analysis of another part of the ATLAS data sample, namely of a $Z^0$ boson plus a {\it non-prompt} $J/\psi$. Our study is performed at next-to-leading order in $\alpha_s$ and includes parton-shower effects via the {\sc\small MadGraph5_aMC@NLO} framework. We find out that the data, unlike the case of prompt $J/\psi+Z^0$, do not hint at significant DPS contributions. Owing to the current experimental and theoretical uncertainties, there is still a room for these but with a lower limit of $\sigma_{\rm eff}$ close to 5 mb. We stress the importance of QCD corrections to account for the ATLAS data.Lansberg, Jean-PhilippeShao, Hua-ShengFri, 02 Dec 2016 11:44:21 GMT28 Nov 2016arXiv:1611.09303http://cds.cern.ch/record/2236670['arXiv:1611.09303']arXiv:1611.09303Constraints on violation of Lorentz invariance from atmospheric showers initiated by multi-TeV photons
http://cds.cern.ch/record/2236459
We discuss the effect of hypothetical violation of Lorentz invariance at high energies on the formation of atmospheric showers by very-high-energy gamma rays. In the scenario where Lorentz invariance violation leads to a decrease of the photon velocity with energy the formation of the showers is suppressed compared to the Lorentz invariant case. Absence of such suppression in the high-energy part of spectrum of the Crab nebula measured independently by HEGRA and H.E.S.S. collaborations is used to set lower bounds on the energy scale of Lorentz invariance violation. These bounds are competitive with the strongest existing constraints obtained from timing of variable astrophysical sources and the absorption of TeV photons on the extragalactic background light. They will be further improved by the next generation of multi-TeV gamma-ray observatories.Rubtsov, GrigorySatunin, PetrSibiryakov, SergeyFri, 02 Dec 2016 11:37:51 GMT30 Nov 2016arXiv:1611.10125http://cds.cern.ch/record/2236459['arXiv:1611.10125']arXiv:1611.10125Massless Interacting Scalar Fields in de Sitter space
http://cds.cern.ch/record/2228768
We present a method to compute the two-point functions for an $O(N)$ scalar field model in de Sitter spacetime, avoiding the well known infrared problems for massless fields. The method is based on an exact treatment of the Euclidean zero modes and a perturbative one of the nonzero modes, and involves a partial resummation of the leading secular terms. This resummation, crucial to obtain a decay of the correlation functions, is implemented along with a double expansion in an effective coupling constant $\sqrt\lambda$ and in $1/N$. The results reduce to those known in the leading infrared approximation and coincide with the ones obtained directly in Lorentzian de Sitter spacetime in the large $N$ limit. The new method allows for a systematic calculation of higher order corrections both in $\sqrt\lambda$ and in $1/N$.Nacir, Diana LópezMazzitelli, Francisco DTrombetta, Leonardo GTue, 01 Nov 2016 06:47:05 GMT31 Oct 2016arXiv:1610.09943http://cds.cern.ch/record/2228768['arXiv:1610.09943']arXiv:1610.09943Likelihood Analysis of Supersymmetric SU(5) GUTs
http://cds.cern.ch/record/2228749
We perform a likelihood analysis of the constraints from accelerator experiments and astrophysical observations on supersymmetric (SUSY) models with SU(5) boundary conditions on soft SUSY-breaking parameters at the GUT scale. The parameter space of the models studied has 7 parameters: a universal gaugino mass $m_{1/2}$, distinct masses for the scalar partners of matter fermions in five- and ten-dimensional representations of SU(5), $m_5$ and $m_{10}$, and for the $\mathbf{5}$ and $\mathbf{\bar 5}$ Higgs representations $m_{H_u}$ and $m_{H_d}$, a universal trilinear soft SUSY-breaking parameter $A_0$, and the ratio of Higgs vevs $\tan \beta$. In addition to previous constraints from direct sparticle searches, low-energy and flavour observables, we incorporate constraints based on preliminary results from 13 TeV LHC searches for jets + MET events and long-lived particles, as well as the latest PandaX-II and LUX searches for direct Dark Matter detection. In addition to previously-identified mechanisms for bringing the supersymmetric relic density into the range allowed by cosmology, we identify a novel ${\tilde u_R}/{\tilde c_R} - \tilde{\chi}^0_1$ coannihilation mechanism that appears in the supersymmetric SU(5) GUT model and discuss the role of ${\tilde \nu_\tau}$ coannihilation. We find complementarity between the prospects for direct Dark Matter detection and SUSY searches at the LHC.Bagnaschi, ECosta, J.C.Sakurai, K.Borsato, M.Buchmueller, O.Cavanaugh, R.Chobanova, V.Citron, M.De Roeck, A.Dolan, M.J.Ellis, J.R.Flächer, H.Heinemeyer, S.Isidori, G.Lucio, M.Martínez Santos, D.Olive, K.A.Richards, A.de Vries, K.J.Weiglein, G.Tue, 01 Nov 2016 06:46:07 GMT31 Oct 2016arXiv:1610.10084http://cds.cern.ch/record/2228749['arXiv:1610.10084']arXiv:1610.10084D = 3 Unification of Curious Supergravities
http://cds.cern.ch/record/2228159
We consider the dimensional reduction to D = 3 of four maximal-rank supergravities which preserve minimal supersymmetry in D = 11, 7, 5 and 4. Such "curious" theories were investigated some time ago, and the four-dimensional one corresponds to an N = 1 supergravity with 7 chiral multiplets spanning the seven-disk manifold. Recently, this latter theory was considered to provide cosmological models for alpha-attractors, which are based on the disk geometry with possible restrictions on the parameter alpha. A unified picture emerges in D = 3, where the Ehlers group of General Relativity merges with the S-, T- and U- dualities of the D = 4 parent theories.Duff, M JFerrara, SMarrani, AFri, 28 Oct 2016 05:41:22 GMT27 Oct 2016arXiv:1610.08800http://cds.cern.ch/record/2228159['arXiv:1610.08800']arXiv:1610.08800Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
http://cds.cern.ch/record/2228150
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.Mehtar-Tani, YacineTywoniuk, KonradFri, 28 Oct 2016 05:40:55 GMT27 Oct 2016arXiv:1610.08930http://cds.cern.ch/record/2228150['arXiv:1610.08930']arXiv:1610.08930Accurate initial conditions in mixed Dark Matter--Baryon simulations
http://cds.cern.ch/record/2228024
We quantify the error in the results of mixed baryon--dark-matter hydrodynamic simulations, stemming from outdated approximations for the generation of initial conditions. The error at redshift 0 in contemporary large simulations, is of the order of few to ten percent in the power spectra of baryons and dark matter, and their combined total-matter power spectrum. After describing how to properly assign initial displacements and peculiar velocities to multiple species, we review several approximations: (1) {using the total-matter power spectrum to compute displacements and peculiar velocities of both fluids}, (2) scaling the linear redshift-zero power spectrum back to the initial power spectrum using the Newtonian growth factor ignoring homogeneous radiation, (3) using longitudinal-gauge velocities with synchronous-gauge densities, and (4) ignoring the phase-difference in the Fourier modes for the offset baryon grid, relative to the dark-matter grid. Three of these approximations do not take into account that dark matter and baryons experience a scale-dependent growth after photon decoupling, which results in directions of velocity which are not the same as their direction of displacement. We compare the outcome of hydrodynamic simulations with these four approximations to our reference simulation, all setup with the same random seed and simulated using Gadget-III.Valkenburg, WesselVillaescusa-Navarro, FranciscoFri, 28 Oct 2016 05:38:16 GMT26 Oct 2016arXiv:1610.08501http://cds.cern.ch/record/2228024['arXiv:1610.08501']arXiv:1610.08501A Clockwork Theory
http://cds.cern.ch/record/2227514
The clockwork is a mechanism for generating light particles with exponentially suppressed interactions in theories which contain no small parameters at the fundamental level. We develop a general description of the clockwork mechanism valid for scalars, fermions, gauge bosons, and gravitons. This mechanism can be implemented with a discrete set of new fields or, in its continuum version, through an extra spatial dimension. In both cases the clockwork emerges as a useful tool for model-building applications. Notably, the continuum clockwork offers a solution to the Higgs naturalness problem, which turns out to be the same as in linear dilaton duals of Little String Theory. We also elucidate the similarities and differences of the continuum clockwork with large extra dimensions and warped spaces. All clockwork models, in the discrete and continuum, exhibit novel phenomenology with a distinctive spectrum of closely spaced resonances.Giudice, Gian FMcCullough, MatthewWed, 26 Oct 2016 06:39:43 GMT20 Oct 2016arXiv:1610.07962http://cds.cern.ch/record/2227514['arXiv:1610.07962']arXiv:1610.07962Spectator Higgs, large-scale gauge fields and the non-minimal coupling to gravity
http://cds.cern.ch/record/2227420
Even if the Higgs field does not affect the evolution of the background geometry, its massive inhomogeneities induce large-scale gauge fields whose energy density depends on the slow-roll parameters, on the effective scalar mass and, last but not least, on the dimensionless coupling to the space-time curvature. Since the non-Abelian gauge modes are screened, the non-minimal coupling to gravity predominantly affects the evolution of the hypercharge and electromagnetic fields. While in the case of minimal coupling the obtained constraints are immaterial, as soon as the coupling increases beyond one fourth the produced fields become overcritical. We chart the whole parameter space of this qualitatively new set of bounds. Whenever the limits on the curvature coupling are enforced, the magnetic field may still be partially relevant for large-scale magnetogenesis and exceed $10^{-20}$ G for the benchmark scale of the protogalactic collapse.Giovannini, MassimoWed, 26 Oct 2016 06:36:00 GMT25 Oct 2016arXiv:1610.07977http://cds.cern.ch/record/2227420['arXiv:1610.07977']arXiv:1610.07977Linearized supergravity with a dynamical preferred frame
http://cds.cern.ch/record/2227399
We study supersymmetric extension of the Einstein-aether gravitational model where local Lorentz invariance is broken down to the subgroup of spatial rotations by a vacuum expectation value of a timelike vector field. By restricting to the level of linear perturbations around Lorentz-violating vacuum and using the superfield formalism we construct the most general action invariant under the linearized supergravity transformations. We show that, unlike its non-supersymmetric counterpart, the model contains only a single free dimensionless parameter, besides the usual dimensionful gravitational coupling. This makes the model highly predictive. An analysis of the spectrum of physical excitations reveal superluminal velocity of gravitons. The latter property leads to the extension of the gravitational multiplet by additional fermonic and bosonic states with helicities $\pm 3/2$ and $\pm 1$. We outline the observational constraints on the model following from its low-energy phenomenology.Marakulin, ArthurSibiryakov, SergeyWed, 26 Oct 2016 06:35:56 GMT25 Oct 2016arXiv:1610.07805http://cds.cern.ch/record/2227399['arXiv:1610.07805']arXiv:1610.07805Exact $\nabla^4 R^4$ couplings and helicity supertraces
http://cds.cern.ch/record/2226938
In type II string theory compactified on a $d$-dimensional torus $T^d$ down to $D=10-d$ dimensions, the $R^4$ and $\nabla^4 R^4$ four-graviton couplings are known exactly, for all values of the moduli, in terms of certain Eisenstein series of the U-duality group $E_{d}(\mathbb{Z})$. In the limit where one circle in the torus becomes large, these couplings are expected to reduce to their counterpart in dimension $D+1$, plus threshold effects and exponentially suppressed corrections corresponding to BPS black holes in dimension $D+1$ whose worldline winds around the circle. By combining the weak coupling and large radius limits, we determine these exponentially suppressed corrections exactly, and demonstrate that the contributions of 1/4-BPS black holes to the $\nabla^4 R^4$ coupling are proportional to the appropriate helicity supertrace. Mathematically, our results provide the complete Fourier expansion of the next-to-minimal theta series of $E_{d+1}(\mathbb{Z})$ with respect to the maximal parabolic subgroup with Levi component $E_{d}$ for $d\leq 6$, and the complete Abelian part of the Fourier expansion of the same for $d=7$.Bossard, GuillaumePioline, BorisMon, 24 Oct 2016 05:21:43 GMT21 Oct 2016arXiv:1610.06693http://cds.cern.ch/record/2226938['arXiv:1610.06693']arXiv:1610.06693Science with the space-based interferometer LISA. IV: Probing inflation with gravitational waves
http://cds.cern.ch/record/2226671
We investigate the potential for the LISA space-based interferometer to detect the stochastic gravitational wave background produced from different mechanisms during inflation. Focusing on well-motivated scenarios, we study the resulting contributions from particle production during inflation, inflationary spectator fields with varying speed of sound, effective field theories of inflation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes. The projected sensitivities of LISA are used in a model-independent way for various detector designs and configurations. We demonstrate that LISA is able to probe these well-motivated inflationary scenarios beyond the irreducible vacuum tensor modes expected from any inflationary background.Bartolo, NicolaCaprini, ChiaraDomcke, ValerieFigueroa, Daniel GGarcia-Bellido, JuanGuzzetti, Maria ChiaraLiguori, MicheleMatarrese, SabinoPeloso, MarcoPetiteau, AntoineRicciardone, AngeloSakellariadou, MairiSorbo, LorenzoTasinato, GianmassimoSat, 22 Oct 2016 05:28:20 GMT20 Oct 2016arXiv:1610.06481http://cds.cern.ch/record/2226671['arXiv:1610.06481']arXiv:1610.06481Constraints on the trilinear Higgs coupling from vector boson fusion and associated Higgs production at the LHC
http://cds.cern.ch/record/2226225
We examine the constraints on the trilinear Higgs coupling $\lambda$ that originate from associated ($Vh$) and vector boson fusion (VBF) Higgs production in $pp$ collisions in the context of the Standard Model effective field theory. The 1-loop contributions to $pp \to V h$ and $pp \to jj h$ that stem from insertions of the dimension-6 operator $O_6 = - \lambda \left (H^\dagger H \right )^3$ are calculated and combined with the ${\cal O} (\lambda)$ corrections to the partial decay widths of the Higgs boson. Employing next-to-next-to-leading order QCD predictions, we analyse the sensitivity of current and forthcoming measurements of the signal strengths in $Vh$ and VBF Higgs production to changes in $\lambda$. We show that future LHC runs may be able to probe modifications of $\lambda$ with a sensitivity similar to the one that is expected to arise from determinations of double-Higgs production. The sensitivity of differential $Vh$ and VBF Higgs distributions to a modified $h^3$ coupling is also studied.Bizon, WojciechGorbahn, MartinHaisch, UlrichZanderighi, GiuliaThu, 20 Oct 2016 06:40:35 GMT18 Oct 2016arXiv:1610.05771http://cds.cern.ch/record/2226225['arXiv:1610.05771']arXiv:1610.05771Towards an automated tool to evaluate the impact of the nuclear modification of the gluon density on quarkonium, D and B meson production in proton-nucleus collisions
http://cds.cern.ch/record/2226219
We propose a simple and model-independent procedure to account for the impact of the nuclear modification of the gluon density as encoded in nuclear collinear PDF sets on two-to-two partonic hard processes in proton-nucleus collisions. This applies to a good approximation to quarkonium, D and B meson production, generically referred to H. Our procedure consists in parametrising the square of the parton scattering amplitude, A_{gg -> H X} and constraining it from the proton-proton data. Doing so, we have been able to compute the corresponding nuclear modification factors for J/psi, Upsilon and D^0 as a function of y and P_T at sqrt(s_NN)=5 and 8 TeV in the kinematics of the various LHC experiments in a model independent way. It is of course justified since the most important ingredient in such evaluations is the probability of each kinematical configuration. Our computations for D mesons can also be extended to B meson production. To further illustrate the potentiality of the tool, we provide --for the first time-- predictions for the nuclear modification factor for eta_c production in pPb collisions at the LHC.Lansberg, Jean-PhilippeShao, Hua-ShengThu, 20 Oct 2016 06:40:24 GMT17 Oct 2016arXiv:1610.05382http://cds.cern.ch/record/2226219['arXiv:1610.05382']arXiv:1610.05382QCD next-to-leading order predictions matched to parton showers for vector-like quark models
http://cds.cern.ch/record/2225709
Vector-like quarks are featured by a wealth of beyond the Standard Model theories and are consequently an important goal of many LHC searches for new physics. Those searches, as well as most related phenomenological studies, however rely on predictions evaluated at the leading-order accuracy in QCD and consider well-defined simplified benchmark scenarios. Adopting an effective bottom-up approach, we compute next-to-leading-order predictions for vector-like-quark pair-production and single production in association with jets, with a weak or with a Higgs boson in a general new physics setup. We additionally compute vector-like-quark contributions to the production of a pair of Standard Model bosons at the same level of accuracy. For all processes under consideration, we focus both on total cross sections and on differential distributions, most these calculations being performed for the first time in our field. As a result, our work paves the way to precise extraction of experimental limits on vector-like quarks thanks to an accurate control of the shapes of the relevant observables and emphasize the extra handles that could be provided by novel vector-like-quark probes never envisaged so farFuks, BenjaminShao, Hua-ShengTue, 18 Oct 2016 06:01:20 GMT14 Oct 2016arXiv:1610.04622http://cds.cern.ch/record/2225709['arXiv:1610.04622']arXiv:1610.04622Compensating strong coupling with large charge
http://cds.cern.ch/record/2225343
We study (conformal) field theories with global symmetries in the sector where the value of the global charge $Q$ is large. We find (as expected) that the low energy excitations of this sector are described by the general form of Goldstone's theorem in the non-relativistic regime. We also derive the unexpected result, first presented in [Hellerman:2015], that the effective field theory describing such sector of fixed $Q$ contains effective couplings $\lambda_{\text{eff}}\sim \lambda^b /Q^{a}$, where $\lambda$ is the original coupling. Hence, large charge leads to weak coupling. In the last section of the paper we present an outline of how to compute anomalous dimensions in this limit.Alvarez-Gaume, LuisLoukas, OrestisOrlando, DomenicoReffert, SusanneMon, 17 Oct 2016 05:23:03 GMT14 Oct 2016arXiv:1610.04495http://cds.cern.ch/record/2225343['arXiv:1610.04495']arXiv:1610.04495Seven-Disk Manifold, alpha-attractors and B-modes
http://cds.cern.ch/record/2224414
Cosmological alpha-attractor models in \cN=1 supergravity are based on hyperbolic geometry of a Poincar\'e disk with the radius square {\cal R}^2=3\alpha. The predictions for the B-modes, r\approx 3\alpha {4\over N^2}, depend on moduli space geometry and are robust for a rather general class of potentials. Here we notice that starting with M-theory compactified on a 7-manifold with G_2 holonomy, with a special choice of Betti numbers, one can obtain d=4 \cN=1 supergravity with rank 7 scalar coset \Big[{SL(2)\over SO(2)}\Big]^7. In a model where these 7 unit size Poincar\'e disks have identified moduli one finds that 3 alpha =7. Assuming that the moduli space geometry of the phenomenological models is inherited from this version of M-theory, one would predict r \approx 10^{-2} for 53 e-foldings. We also describe the related maximal supergravity and M/string theory models leading to preferred values 3 alpha =1,2,3,4,5,6,7.Ferrara, SergioKallosh, RenataFri, 14 Oct 2016 05:50:02 GMT13 Oct 2016arXiv:1610.04163http://cds.cern.ch/record/2224414['arXiv:1610.04163']arXiv:1610.04163Six-dimensional Origin of $\mathcal{N}=4$ SYM with Duality Defects
http://cds.cern.ch/record/2224132
We study the topologically twisted compactification of the 6d $(2,0)$ M5-brane theory on an elliptically fibered K\"ahler three-fold preserving two supercharges. We show that upon reducing on the elliptic fiber, the 4d theory is $\mathcal{N}=4$ Super-Yang Mills, with varying complexified coupling $\tau$, in the presence of defects. For abelian gauge group this agrees with the so-called duality twisted theory, and we determine a non-abelian generalization to $U(N)$. When the elliptic fibration is singular, the 4d theory contains 3d walls (along the branch-cuts of $\tau$) and 2d surface defects, around which the 4d theory undergoes $SL(2,\mathbb{Z})$ duality transformations. Such duality defects carry chiral fields, which from the 6d point of view arise as modes of the two-form $B$ in the tensor multiplet. Each duality defect has a flavor symmetry associated to it, which is encoded in the structure of the singular elliptic fiber above the defect. Generically 2d surface defects will intersect in points in 4d, where there is an enhanced flavor symmetry. The 6d point of view provides a complete characterization of this 4d-3d-2d-0d `Matroshka'-defect configuration.Assel, BenjaminSchafer-Nameki, SakuraThu, 13 Oct 2016 06:17:42 GMT12 Oct 2016arXiv:1610.03663http://cds.cern.ch/record/2224132['arXiv:1610.03663']arXiv:1610.03663Worm Algorithm for CP(N-1) Model
http://cds.cern.ch/record/2223059
The CP(N-1) model in 2D is an interesting toy model for 4D QCD as it possesses confinement, asymptotic freedom and a non-trivial vacuum structure. Due to the lower dimensionality and the absence of fermions, the computational cost for simulating 2D CP(N-1) on the lattice is much lower than that for simulating 4D QCD. However, to our knowledge, no efficient algorithm for simulating the lattice CP(N-1) model has been tested so far, which also works at finite density. To this end we propose a new type of worm algorithm which is appropriate to simulate the lattice CP(N-1) model in a dual, flux-variables based representation, in which the introduction of a chemical potential does not give rise to any complications. In addition to the usual worm moves where a defect is just moved from one lattice site to the next, our algorithm additionally allows for worm-type moves in the internal variable space of single links, which accelerates the Monte Carlo evolution. We use our algorithm to compare the two popular CP(N-1) lattice actions and exhibit marked differences in their approach to the continuum limit.Rindlisbacher, Tobiasde Forcrand, PhilippeSat, 08 Oct 2016 05:49:24 GMT05 Oct 2016arXiv:1610.01435http://cds.cern.ch/record/2223059['arXiv:1610.01435']arXiv:1610.01435Time evolution of linearized gauge field fluctuations on a real-time lattice
http://cds.cern.ch/record/2223057
Classical real-time lattice simulations play an important role in understanding non-equilibrium phenomena in gauge theories and are used in particular to model the prethermal evolution of heavy-ion collisions. Due to instabilities, small quantum fluctuations on top of the classical background may significantly affect the dynamics of the system. In this paper we argue for the need for a numerical calculation of a system of classical gauge fields and small linearized fluctuations in a way that keeps the separation between the two manifest. We derive and test an explicit algorithm to solve these equations on the lattice, maintaining gauge invariance and Gauss's law.Kurkela, AleksiLappi, TuomasPeuron, JarkkoSat, 08 Oct 2016 05:49:21 GMT05 Oct 2016arXiv:1610.01355http://cds.cern.ch/record/2223057['arXiv:1610.01355']arXiv:1610.01355The Slab Method to Measure the Topological Susceptibility
http://cds.cern.ch/record/2221432
In simulations of a model with topological sectors, algorithms which proceed in small update steps tend to get stuck in one sector, especially on fine lattices. This distorts the numerical results, in particular it is not straightforward to measure the topological susceptibility chi_t. We test a method to measure chi_t even if configurations from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as "slabs". This enables the evaluation of chi_t, as we demonstrate with numerical results for non-linear sigma-models and for 2-flavour QCD.Bietenholz, WolfgangCichy, Krzysztofde Forcrand, PhilippeDromard, ArthurGerber, UrsTue, 04 Oct 2016 05:54:10 GMT03 Oct 2016arXiv:1610.00685http://cds.cern.ch/record/2221432['arXiv:1610.00685']arXiv:1610.00685ZZ production in gluon fusion at NLO matched to parton-shower
http://cds.cern.ch/record/2221411
We present a calculation of the next-to-leading order (NLO) QCD corrections to the hadroproduction process $gg\to ZZ \to e^+e^- \mu^+ \mu^-$, matched to the parton shower in the POWHEG framework. We take advantage of the POWHEG BOX tool for the implementation and rely on PYTHIA 8 for the showering and hadronization stages. We fully include $\gamma^*/Z$ interference effects, while also covering the single-resonant region. For this phenomenological study we focus on four lepton production as a signal process, neglecting all quark mass effects as well as the Higgs-mediated contributions, which are known to be subdominant in this case. We provide predictions from our simulations for the 13 TeV LHC Run II setup, including realistic experimental cuts.Alioli, SimoneCaola, FabrizioLuisoni, GionataRöntsch, RaulTue, 04 Oct 2016 05:52:42 GMT30 Sep 2016arXiv:1609.09719http://cds.cern.ch/record/2221411['arXiv:1609.09719']arXiv:1609.09719Mass Formulae for Broken Supersymmetry in Curved Space-Time
http://cds.cern.ch/record/2219927
We derive the mass formulae for ${\cal N}=1$, $D=4$ matter-coupled Supergravity for broken (and unbroken) Supersymmetry in curved space-time. These formulae are applicable to de Sitter configurations as is the case for inflation. For unbroken Supersymmetry in anti-de Sitter (AdS) one gets the mass relations modified by the AdS curvature. We compute the mass relations both for the potential and its derivative non-vanishing.Ferrara, SergioVan Proeyen, AntoineWed, 28 Sep 2016 06:01:04 GMT27 Sep 2016arXiv:1609.08480http://cds.cern.ch/record/2219927['arXiv:1609.08480']arXiv:1609.08480Gauged Lepton Flavour
http://cds.cern.ch/record/2217407
The gauging of the lepton flavour group is considered in the Standard Model context and in its extension with three right-handed neutrinos. The anomaly cancellation conditions lead to a Seesaw mechanism as underlying dynamics for all leptons; requiring in addition a phenomenologically viable setup leads to Majorana masses for the neutral sector: the type I Seesaw Lagrangian in the Standard Model case and the inverse Seesaw in the extended model. Within the minimal extension of the scalar sector, the Yukawa couplings are promoted to scalar fields in the bifundamental of the flavour group. The resulting low-energy Yukawa couplings are proportional to inverse powers of the vacuum expectation values of those scalars; the protection against flavour changing neutral currents differs from that of Minimal Flavor Violation. In all cases, the $\mu-\tau$ flavour sector exhibits rich and promising phenomenological signals.Alonso, RMartinez, E FernandezGavela, M BGrinstein, BMerlo, LQuilez, PThu, 22 Sep 2016 06:22:55 GMT19 Sep 2016arXiv:1609.05902http://cds.cern.ch/record/2217407['arXiv:1609.05902']arXiv:1609.05902