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Novel tools and observables for jet physics in heavy-ion collisions
http://cds.cern.ch/record/2634233
Studies of fully-reconstructed jets in heavy-ion collisions aim at extracting thermodynamical and transport properties of hot and dense QCD matter. Recently, a plethora of new jet substructure observables have been theoretically and experimentally developed that provide novel precise insights on the modifications of the parton radiation pattern induced by a QCD medium. This report, summarizing the main lines of discussion at the 5th Heavy Ion Jet Workshop and CERN TH institute "Novel tools and observables for jet physics in heavy-ion collisions" in 2017, presents a first attempt at outlining a strategy for isolating and identifying the relevant physical processes that are responsible for the observed medium-induced jet modifications. These studies combine theory insights, based on the Lund parton splitting map, with sophisticated jet reconstruction techniques, including grooming and background subtraction algorithms.Andrews, Harry ArthurApolinario, LilianaBertens, Redmer AlexanderBierlich, ChristianCacciari, MatteoChen, YiChien, Yang-TingMendez, Leticia CunqueiroDeak, Michald'Enterria, DavidDominguez, FabioHarris, Philip ColemanKutak, KrzysztofLee, Yen-JieMehtar-Tani, YacineMulligan, JamesNguyen, MatthewNing-Bo, ChangPerepelitsa, DennisSalam, GavinSpousta, MartinMilhano, Jose GuilhermeTywoniuk, KonradVan Leeuwen, MarcoVerweij, MartaVila, VictorWiedemann, Urs A.Zapp, Korinna C.Wed, 15 Aug 2018 03:22:27 GMT2018-08-10arXiv:1808.03689http://cds.cern.ch/record/2634233['arXiv:1808.03689']arXiv:1808.03689A clockwork solution to the flavor puzzle
http://cds.cern.ch/record/2633862
We introduce a set of clockwork models of flavor that can naturally explain the large hierarchies of the Standard Model quark masses and mixing angles. Since the clockwork only contains chains of new vector-like fermions without any other dynamical fields, the flavor constraints allow for relatively light new physics scale. For two benchmarks with gear masses just above 1 TeV, allowed by flavor constraints, we discuss the collider searches and the possible ways of reconstructing gear spectra at the LHC. We also examine the similarities and differences with the other common solutions to the SM flavor puzzle, i.e., with the Froggatt-Nielsen models, where we identify a new {\it clockworked } version, and with the Randall-Sundrum models.Alonso, RodrigoCarmona, AdrianDillon, Barry M.Kamenik, Jernej F.Martin Camalich, JorgeZupan, JureSat, 11 Aug 2018 02:39:10 GMT2018-07-25arXiv:1807.09792http://cds.cern.ch/record/2633862['arXiv:1807.09792']arXiv:1807.09792Top-Yukawa contributions to bbH production at the LHC
http://cds.cern.ch/record/2633583
We study the production of a Higgs boson in association with bottom quarks ($b\bar{b}H$) in hadronic collisions at the LHC, including the different contributions stemming from terms proportional to the top-quark Yukawa coupling ($y_t^2$), to the bottom-quark one ($y_b^2$), and to their interference ($y_b y_t$). Our results are accurate to next-to-leading order in QCD, employ the four-flavour scheme and the (Born-improved) heavy-top quark approximation. We find that next-to-leading order corrections to the $y_t^2$ component are sizable, making it the dominant production mechanism for associated $b\bar{b}H$ production in the Standard Model and increasing its inclusive rate by almost a factor of two. By studying final-state distributions of the various contributions, we identify observables and selection cuts that can be used to select the various components and to improve the experimental sensitivity of $b\bar{b}H$ production on the bottom-quark Yukawa coupling.Deutschmann, NicolasMaltoni, FabioWiesemann, MariusZaro, MarcoWed, 08 Aug 2018 03:25:41 GMT2018-08-05arXiv:1808.01660http://cds.cern.ch/record/2633583['arXiv:1808.01660']arXiv:1808.01660RHMC with Block Solvers and Multiple Pseudofermions
http://cds.cern.ch/record/2633582
The dominant cost of most lattice QCD simulations is the inversion of the Dirac operator required to calculate the force term in the RHMC update. One way to improve this situation is to use multiple pseudofermions, which reduces the size and variance of this force and hence allows a larger integration step size to be used. This means fewer force term calculations are required, but at the cost of having to invert the Dirac operator for each pseudofermion field. This bottleneck can be addressed: recently there has been renewed interest in the use of block Krylov solvers, which can solve multiple right hand side vectors with significantly fewer iterations than are required if each vector is solved using a separate Krylov solver. We combine these two ideas, achieving a significant speed-up of RHMC lattice QCD simulations.de Forcrand, PhilippeKeegan, LiamWed, 08 Aug 2018 03:25:35 GMT2018-08-06arXiv:1808.01829http://cds.cern.ch/record/2633582['arXiv:1808.01829']arXiv:1808.01829Adding Pseudo-Observables to the Four-Lepton Experimentalist's Toolbox
http://cds.cern.ch/record/2633490
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.Gainer, James S.González-Alonso, MartínGreljo, AdmirIsaković, SenadIsidori, GinoKorytov, AndreyLykken, JosephMarzocca, DavidMatchev, Konstantin T.Milenović, PredragMitselmakher, GuenakhMrenna, StephenPark, MyeonghunRinkevicius, AurelijusSelimović, NudzeimTue, 07 Aug 2018 02:04:51 GMT2018-08-02arXiv:1808.00965http://cds.cern.ch/record/2633490['arXiv:1808.00965']arXiv:1808.00965On Lepton Flavor Universality in Top Quark Decays
http://cds.cern.ch/record/2633489
We propose a novel strategy to test lepton flavor universality (LFU) in top decays, applicable to top pair production at colliders. Our proposal mostly hinges on data-driven techniques and has very little dependence on our theoretical understanding of top pair production. Based on simplified models accommodating recent hints of LFU violation in charged current B meson decays, we show that existing LHC measurements already provide non-trivial information on the flavor structure and the mass scale of such new physics (NP). We also project that the measurements of LFU in top decays at the high-luminosity LHC could reach a precision at the percent level or below, improving the sensitivity to LFU violating NP in the top sector by more than an order of magnitude compared to existing approaches.Kamenik, Jernej F.Katz, AndreyStolarski, DanielTue, 07 Aug 2018 02:04:45 GMT2018-08-02arXiv:1808.00964http://cds.cern.ch/record/2633489['arXiv:1808.00964']arXiv:1808.00964Maximal Flavour Violation: a Cabibbo mechanism for leptoquarks
http://cds.cern.ch/record/2633361
We propose a mechanism that allows for sizeable flavour violation in quark-lepton currents, while suppressing flavour changing neutral currents in quark-quark and lepton-lepton sectors. The mechanism is applied to the recently proposed 4321 renormalizable model, which can accommodate the current experimental anomalies in $B$-meson decays, both in charged and neutral currents, while remaining consistent with all other indirect flavour and electroweak precision measurements and direct searches at high-$p_T$. To support this claim, we present an exhaustive phenomenological survey of this fully calculable UV complete model and highlight the rich complementarity between indirect and direct searches.Di Luzio, LucaFuentes-Martin, JavierGreljo, AdmirNardecchia, MarcoRenner, SophieSun, 05 Aug 2018 03:15:24 GMT2018-08-02arXiv:1808.00942http://cds.cern.ch/record/2633361['arXiv:1808.00942']arXiv:1808.00942Coaction for Feynman integrals and diagrams
http://cds.cern.ch/record/2633177
We propose a general coaction for families of integrals appearing in the evaluation of Feynman diagrams, such as multiple polylogarithms and generalized hypergeometric functions. We further conjecture a link between this coaction and graphical operations on Feynman diagrams. At one-loop order, there is a basis of integrals for which this correspondence is fully explicit. We discuss features and present examples of the diagrammatic coaction on two-loop integrals. We also present the coaction for the functions ${}_{p+1}F_p$ and Appell $F_1$.Abreu, SamuelBritto, RuthDuhr, ClaudeGardi, EinanMatthew, JamesFri, 03 Aug 2018 02:32:11 GMT2018-07-31arXiv:1808.00069http://cds.cern.ch/record/2633177['arXiv:1808.00069']arXiv:1808.00069Femtolensing by Dark Matter Revisited
http://cds.cern.ch/record/2633096
Femtolensing of gamma ray bursts (GRBs) has been put forward as an exciting possibility to probe exotic astrophysical objects with masses below $10^{-13}$ solar masses such as small primordial black holes or ultra-compact dark matter minihalos, made up for instance of QCD axions. In this paper we critically review this idea, properly taking into account the extended nature of the source as well as wave optics effects. We demonstrate that most GRBs are inappropriate for femtolensing searches due to their large sizes. This removes the previous femtolensing bounds on primordial black holes, implying that vast regions of parameter space for primordial black hole dark matter are not robustly constrained. Still, we entertain the possibility that a small fraction of GRBs, characterized by fast variability can have smaller sizes and be useful. However, a large number of such bursts would need to be observed to achieve meaningful constraints. We study the sensitivity of future observations as a function of the number of detected GRBs and of the size of the emission region.Katz, AndreyKopp, JoachimSibiryakov, SergeyXue, WeiThu, 02 Aug 2018 02:25:08 GMT2018-07-30arXiv:1807.11495http://cds.cern.ch/record/2633096['arXiv:1807.11495']arXiv:1807.11495Higgs boson production at the LHC using the $q_T$ subtraction formalism at N$^3$LO QCD
http://cds.cern.ch/record/2633095
We consider higher-order QCD corrections to Higgs boson production through gluon-gluon fusion in the large top quark mass limit in hadron collisions. We extend the transverse-momentum ($q_T$) subtraction method to next-to-next-to-next-to-leading order (N$^3$LO) and combine it with the NNLO Higgs-plus-jet calculation to numerically compute differential infrared-safe observables at N$^3$LO for Higgs boson production in gluon fusion. To cancel the infrared divergences, we exploit the universal behaviour of the associated $q_T$ distributions in the small-$q_T$ region. We document all the necessary ingredients of the transverse-momentum subtraction method up to N$^3$LO. The missing third order collinear functions, which contribute only at $q_T$ =0, are approximated using a prescription which uses the known result for the total Higgs boson cross section at this order. As a first application of the third-order $q_T$ subtraction method, we present the N$^3$LO rapidity distribution of the Higgs boson at the LHC.Cieri, LeandroChen, XuanGehrmann, ThomasGlover, E.W. N.Huss, AlexanderThu, 02 Aug 2018 02:25:06 GMT2018-07-30arXiv:1807.11501http://cds.cern.ch/record/2633095['arXiv:1807.11501']arXiv:1807.11501New constraints on classical de Sitter: flirting with the swampland
http://cds.cern.ch/record/2632490
We study the existence and stability of classical de Sitter solutions of type II supergravities with parallel $D_p$-branes and orientifold $O_p$-planes. Together with the dilaton and volume scalar fields, we consider a third one that distinguishes between parallel and transverse directions to the $D_p/O_p$. We derive the complete scalar potential for these three fields. This formalism allows us to reproduce known constraints obtained in 10d, and to derive new ones. Specifying to group manifolds with constant fluxes, we exclude a large region of parameter space, forbidding de Sitter solutions on nilmanifolds, semi-simple group manifolds, and some solvmanifolds. In the small remaining region, we identify a stability island, where the three scalars would be stabilized in any de Sitter solution. We discuss these results in the swampland context.Andriot, DavidFri, 27 Jul 2018 02:03:01 GMT2018-07-25arXiv:1807.09698http://cds.cern.ch/record/2632490['arXiv:1807.09698']arXiv:1807.09698Dark Energy in light of Multi-Messenger Gravitational-Wave astronomy
http://cds.cern.ch/record/2632389
Gravitational waves (GWs) provide a new tool to probe the nature of dark energy (DE) and the fundamental properties of gravity. We review the different ways in which GWs can be used to test gravity and models for late-time cosmic acceleration. Lagrangian-based gravitational theories beyond general relativity (GR) are classified into those breaking fundamental assumptions, containing additional fields and massive graviton(s). In addition to Lagrangian based theories we present the effective theory of DE and the $\mu$-$\Sigma$ parametrization as general descriptions of cosmological gravity. Multi-messenger GW detections can be used to measure the cosmological expansion (standard sirens), providing an independent test of the DE equation of state and measuring the Hubble parameter. Several key tests of gravity involve the cosmological propagation of GWs, including anomalous GW speed, massive graviton excitations, Lorentz violating dispersion relation, modified GW luminosity distance and additional polarizations, which may also induce GW oscillations. We summarize present constraints and their impact on DE models, including those arising from the binary neutron star merger GW170817. Upgrades of LIGO-Virgo detectors to design sensitivity and the next generation facilities such as LISA or Einstein Telescope will significantly improve these constraints in the next two decades.Ezquiaga, Jose MaríaZumalacárregui, MiguelThu, 26 Jul 2018 02:22:57 GMT2018-07-24IFT-UAM-CSIC-18-83http://cds.cern.ch/record/26323891883Broadening Dark Matter Searches at the LHC: Mono-X versus Darkonium Channels
http://cds.cern.ch/record/2632297
Current searches for dark matter at the LHC focus on mono-X signatures: the production of dark matter in association with a Standard Model (SM) particle. The simplest benchmark introduces a massive spin-1 mediator, the $Z^\prime$ boson, between the dark matter $\chi$ and the SM. Limits derived from mono-X channels are most effective when the mediator can decay into two on-shell dark matter particles: $M_{Z'}\gtrsim 2M_\chi$. We broaden the experimental reach into the complementary region, where the $Z^\prime$ mediator is much lighter than the dark matter. In this scenario the $Z^\prime$ mediates an effective long-range force between the dark matter, thereby facilitating the formation of darkonium bound states, as is common in many dark sector models. The darkonium becomes active when $M_{\chi}>M_{Z'}/\alpha_{\rm eff}$, where $\alpha_{\rm eff}$ is the effective fine-structure constant in the dark sector. Moreover, the darkonium could decay back into SM quarks, without producing missing transverse momentum in the detector. Considering multijet final states, we reinterpret existing searches to constrain the simple $Z^\prime$ benchmark beyond the region probed by mono-X searches. Assuming a baryonic $Z^\prime$ mediator and a Dirac dark matter, direct detection bounds can be loosened by giving a small Majorana mass to the dark matter. We also consider the interplay between mono-X and darkonium channels at future high energy colliders, which is at the frontier of probing the model parameter space.Krovi, AnirudhLow, IanZhang, YueWed, 25 Jul 2018 02:44:34 GMT2018-07-20arXiv:1807.07972http://cds.cern.ch/record/2632297['arXiv:1807.07972']arXiv:1807.07972Multi-Loop Amplitudes in the High-Energy Limit in N=4 SYM
http://cds.cern.ch/record/2632183
We introduce a novel way to perform high-order computations in multi-Regge-kinematics in planar $\mathcal{N}=4$ supersymmetric Yang-Mills theory and generalize the existing factorization into building blocks at two loops to all loop orders. Afterwards, we will explain how this framework can be used to easily obtain higher-loop amplitudes from existing amplitudes and how to relate them to amplitudes with higher number of legs.Del Duca, VittorioDruc, StefanDrummond, JamesDuhr, ClaudeDulat, FalkoMarzucca, RobinPapathanasiou, GeorgiosVerbeek, BramTue, 24 Jul 2018 03:17:51 GMT2018-07-20arXiv:1807.07751http://cds.cern.ch/record/2632183['arXiv:1807.07751']arXiv:1807.07751Searching for heavy Higgs bosons in the $t \bar t Z$ and $t b W$ final states
http://cds.cern.ch/record/2632181
In the context of two-Higgs doublet models, we explore the possibility of searching for heavy Higgs bosons in the $t \bar t Z$ and $t bW$ final states. We develop realistic analyses strategies and in the case of the $t \bar t Z$ channel provide a detailed evaluation of the new-physics reach at the 14 TeV LHC. We find that already with an integrated luminosity of $300 \, {\rm fb}^{-1}$ searches for the $t \bar t Z$ signature can provide statistically significant constraints at low values of $\tan \beta$ for heavy Higgs masses in the range from around $450 \, {\rm GeV}$ to $1150 \, {\rm GeV}$. Future searches for heavy Higgses in the $tbW$ final state are also expected to be able to probe parts of this parameter space, though the precise constraints turn out to depend sensitively on the assumed systematics on the shape of the $t \bar t$ background.Haisch, UlrichPolesello, GiacomoTue, 24 Jul 2018 03:17:44 GMT2018-07-20arXiv:1807.07734http://cds.cern.ch/record/2632181['arXiv:1807.07734']arXiv:1807.07734Elliptic polylogarithms and two-loop Feynman integrals
http://cds.cern.ch/record/2631857
We review certain classes of iterated integrals that appear in the computation of Feynman integrals that involve elliptic functions. These functions generalise the well-known class of multiple polylogarithms to elliptic curves and are closely related to the elliptic multiple polylogarithms (eMPLs) studied in the mathematics literature. When evaluated at certain special values of the arguments, eMPLs reduce to another class of special functions, defined as iterated integrals of Eisenstein series. As a novel application of our formalism, we illustrate how a class of special functions introduced by Remiddi and one of the authors can always naturally be expressed in terms of either eMPLs or iterated integrals of Eisenstein series for the congruence subgroup Gamma(6).Broedel, JohannesDuhr, ClaudeDulat, FalkoPenante, BrendaTancredi, LorenzoFri, 20 Jul 2018 02:10:36 GMT2018-07-17arXiv:1807.06238http://cds.cern.ch/record/2631857['arXiv:1807.06238']arXiv:1807.06238Limits on Neutrino Lorentz Violation from Multimessenger Observations of TXS 0506+056
http://cds.cern.ch/record/2631515
The observation by the IceCube Collaboration of a high-energy ($E \gtrsim 200$ TeV) neutrino from the direction of the blazar TXS 0506+056 and the coincident observations of enhanced $\gamma$-ray emissions from the same object by MAGIC and other experiments can be used to set stringent constraints on Lorentz violation in the propagation of neutrinos that is linear in the neutrino energy: $\Delta v = - E/M_1$, where $\Delta v$ is the deviation from the velocity of light, and $M_1$ is an unknown high energy scale to be constrained by experiment. Allowing for a difference in neutrino and photon propagation times of $\sim 10$ days, we find that $M_1 \gtrsim 3 \times 10^{16}$ GeV. This improves on previous limits on linear Lorentz violation in neutrino propagation by many orders of magnitude, and the same is true for quadratic Lorentz violation.Ellis, JohnMavromatos, Nikolaos E.Sakharov, Alexander S.Sarkisyan-Grinbaum, Edward K.Tue, 17 Jul 2018 02:15:05 GMT2018-07-13arXiv:1807.05155http://cds.cern.ch/record/2631515['arXiv:1807.05155']arXiv:1807.05155On the de Sitter swampland criterion
http://cds.cern.ch/record/2631513
A new swampland criterion has recently been proposed. As a consequence, it forbids the existence of de Sitter solutions in a low energy effective theory of a quantum gravity. However, there exist classical de Sitter solutions of ten-dimensional (10d) type II supergravities, even though they are unstable. This appears at first sight in contradiction with the criterion. Beyond possible doubts on the validity of these solutions, we propose two answers to this apparent puzzle. A first possibility is that the known 10d solutions always exhibit an energy scale of order or higher than a Kaluza-Klein scale, as we argue. A corresponding 4d low energy effective theory would then differ from the usual consistent truncations, and as we explain, would not admit a de Sitter solution. This would reconcile the existence of these 10d de Sitter solutions with the 4d criterion. A second, alternative possibility is to have a refined swampland criterion, that we propose. It forbids to have both the existence and the stability of a de Sitter solution, while unstable solutions are still allowed.Andriot, DavidTue, 17 Jul 2018 02:14:58 GMT2018-06-28arXiv:1806.10999http://cds.cern.ch/record/2631513['arXiv:1806.10999']arXiv:1806.10999Effective operators in $t$-channel single top production and decay
http://cds.cern.ch/record/2630406
The production of a single top quark in the $t$-channel and its subsequent decay is studied at NLO accuracy in QCD, augmented with the relevant dimension-6 effective operators from the Standard Model Effective Theory. We examine various kinematic and angular distributions for proton-proton collisions at the LHC at 13 TeV, in order to assess the sensitivity to these operators, both with and without the top quark narrow width approximation. Our results will be helpful when devising strategies to establish bounds on their coefficients, including the amount of CP violation of the weak dipole operator.de Beurs, M.Laenen, E.Vreeswijk, M.Vryonidou, E.Thu, 12 Jul 2018 02:27:16 GMT2018-07-10arXiv:1807.03576http://cds.cern.ch/record/2630406['arXiv:1807.03576']arXiv:1807.03576Infrared sensitivity of single jet inclusive production at hadron colliders
http://cds.cern.ch/record/2630405
Jet production at hadron colliders is a benchmark process to probe the dynamics of the strong interaction and the structure of the colliding hadrons. One of the most basic jet production observables is the single jet inclusive cross section, which is obtained by summing all jets that are observed in an event. Our recent computation of next-to-next-to-leading order (NNLO) QCD contributions to single jet inclusive observables uncovered large corrections in certain kinematical regions, which also resulted in a sizeable ambiguity on the appropriate choice of renormalization and factorization scales. We now perform a detailed investigation of the infrared sensitivity of the different ingredients to the single jet inclusive cross section. We show that the contribution from the second jet, ordered in transverse momentum $p_{T}$, in the event is particularly sensitive to higher order effects due to implicit restrictions on its kinematics. By investigating the second-jet transverse momentum distribution, we identify large-scale cancellations between different kinematical event configurations, which are aggravated by certain types of scale choice. Taking perturbative convergence and stability as selection criteria enables us to single out the total partonic transverse energy $\hat{H}_{T}$ and twice the individual jet transverse momentum $2\,p_{T}$ (with which $\hat{H}_{T}$ coincides in Born kinematics) as the most appropriate scales in the perturbative description of single jet inclusive production.Currie, JamesGehrmann-De Ridder, AudeGehrmann, ThomasGlover, E.W. NigelHuss, AlexanderPires, JoãoThu, 12 Jul 2018 02:24:37 GMT2018-07-10IPPP-18-38http://cds.cern.ch/record/26304051838Two-current correlations in the pion on the lattice
http://cds.cern.ch/record/2630206
We perform a systematic study of the correlation functions of two quark currents in a pion using lattice QCD. We obtain good signals for all but one of the relevant Wick contractions of quark fields. We investigate the quark mass dependence of our results and test the importance of correlations between the quark and the antiquark in the pion. Our lattice data are compared with predictions from chiral perturbation theory.Bali, Gunnar S.Bruns, PeterCastagnini, LucaDiehl, MarkusGaunt, Jonathan R.Glaessle, BenjaminSchafer, AndreasSternbeck, AndréZimmermann, ChristianWed, 11 Jul 2018 02:20:29 GMT2018-07-09DESY-18-105http://cds.cern.ch/record/263020618105A No-go Theorem for a Gauge Vector as a Space-time Goldstone
http://cds.cern.ch/record/2630205
Scalars and fermions can arise as Goldstone modes of non-linearly realised extensions of the Poincare group (with important implications for the soft limits of such theories): the Dirac-Born-Infeld scalar realises a higher-dimensional Poincare symmetry, while the Volkov-Akulov fermion corresponds to super-Poincare. In this paper we classify extensions of the Poincare group which give rise to a vector Goldstone mode instead. Our main result is that there are no healthy interacting $U(1)$ gauge theories that non-linearly realise space-time symmetries beyond gauge transformations. This implies that the special soft limits of e.g. the Born-Infeld vector cannot be explained by space-time symmetries.Klein, RemkoMalek, EmanuelRoest, DiederikStefanyszyn, DavidWed, 11 Jul 2018 02:20:29 GMT2018-06-18CERN-TH-2018-143http://cds.cern.ch/record/26302052018143Seifert fibering operators in 3d $\mathcal{N}=2$ theories
http://cds.cern.ch/record/2629915
We study 3d $\mathcal{N}=2$ supersymmetric gauge theories on closed oriented Seifert manifold---circle bundles over an orbifold Riemann surface---, with a gauge group G given by a product of simply-connected and/or unitary Lie groups. Our main result is an exact formula for the supersymmetric partition function on any Seifert manifold, generalizing previous results on lens spaces. We explain how the result for an arbitrary Seifert geometry can be obtained by combining simple building blocks, the "fibering operators." These operators are half-BPS line defects, whose insertion along the $S^1$ fiber has the effect of changing the topology of the Seifert fibration. We also point out that most supersymmetric partition functions on Seifert manifolds admit a discrete refinement, corresponding to the freedom in choosing a three-dimensional spin structure. As a strong consistency check on our result, we show that the Seifert partition functions match exactly across infrared dualities. The duality relations are given by intricate (and seemingly new) mathematical identities, which we tested numerically. Finally, we discuss in detail the supersymmetric partition function on the lens space $L(p,q)_b$ with rational squashing parameter $b^2 \in \mathbb{Q}$, comparing our formalism to previous results, and explaining the relationship between the fibering operators and the three-dimensional holomorphic blocks.Closset, CyrilKim, HeeyeonWillett, BrianTue, 10 Jul 2018 02:11:10 GMT2018-07-06arXiv:1807.02328http://cds.cern.ch/record/2629915['arXiv:1807.02328']arXiv:1807.02328Phenomenological Constraints on Anomaly-Free Dark Matter Models
http://cds.cern.ch/record/2629914
We study minimal benchmark models of dark matter with an extra anomaly-free U(1)' gauge boson Z'. We find model parameters that give rise to the correct cosmological dark matter density while evading the latest direct detection searches for dark matter scattering produced by the XENON1T experiment, including the effects of Z-Z' mixing. We also find regions of parameter space that evade the constraints from LHC measurements of dileptons and dijets, precision electroweak measurements, and LHC searches for monojet events with missing transverse energy. We study two benchmark Z' models with Y-sequential couplings to quarks and leptons, one with a vector-like coupling to the dark matter particle and one with an axial dark matter coupling. The vector-like model is extremely tightly constrained, with only a narrow allowed strip where $m_\chi \simeq M_{Z'}/2$, and the axial model is excluded within the parameter range studied. We also consider two leptophobic Z$^\prime$ benchmark models, finding again narrow allowed strips where $m_\chi \simeq M_{Z'}/2$ as well as more extended regions where $\log_{10} (m_\chi/ {\rm GeV}) \gtrsim 3.2$.Ellis, JohnFairbairn, MalcolmTunney, PatrickTue, 10 Jul 2018 02:10:53 GMT2018-07-06KCL-PH-TH-2018-32http://cds.cern.ch/record/2629914201832Spin Correlations in Parton Shower Simulations
http://cds.cern.ch/record/2629427
Spin correlations are an important, but often neglected, effect in modern Monte Carlo event generators. We show that they can be fully incorporated in Herwig 7 using the algorithm originally proposed by Collins and Knowles in all stages of the event generation process and between the different stages of the event generation. In this paper we present the final missing ingredient, correlations in both the angular-ordered and dipole shower algorithms and between the parton shower and hard production and decay processes.Richardson, PeterWebster, StephenSat, 07 Jul 2018 02:56:26 GMT2018-07-05IPPP/18/55http://cds.cern.ch/record/2629427['IPPP/18/55']IPPP/18/55