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Oscillating propagators in heavy-dense QCD
http://cds.cern.ch/record/2131018
Using Monte Carlo simulations and extended mean field theory calculations we show that the $3$-dimensional $\mathbb{Z}_3$ spin model with complex external fields has non-monotonic correlators in some regions of its parameter space. This model serves as a proxy for heavy-dense QCD in $(3+1)$ dimensions. Non-monotonic correlators are intrinsically related to a complex mass spectrum and a liquid-like (or crystalline) behavior. A liquid phase could have implications for heavy-ion experiments, where it could leave detectable signals in the spatial correlations of baryons.Akerlund, Oscarde Forcrand, PhilippeRindlisbacher, TobiasThu, 11 Feb 2016 07:20:17 GMT09 Feb 2016arXiv:1602.02925http://cds.cern.ch/record/2131018['arXiv:1602.02925']arXiv:1602.02925Specialized minimal PDFs for optimized LHC calculations
http://cds.cern.ch/record/2128277
We present a methodology for the construction of parton distribution functions (PDFs) designed to provide an accurate representation of PDF uncertainties for specific processes or classes of processes with a minimal number of PDF error sets: specialized minimal PDF sets, or SM-PDFs. We construct these SM-PDFs in such a way that sets corresponding to different input processes can be combined without losing information, specifically on their correlations, and that they are robust upon smooth variations of the kinematic cuts. The proposed strategy never discards information, so that the SM-PDF sets can be enlarged by the addition of new processes, until the prior PDF set is eventually recovered for a large enough set of processes. We illustrate the method by producing SM-PDFs tailored to Higgs, top quark pair, and electroweak gauge boson physics, and determine that, when the PDF4LHC15 combined set is used as the prior, around 11, 4 and 11 Hessian eigenvectors respectively are enough to fully describe the corresponding processes.Carrazza, StefanoForte, StefanoKassabov, ZahariRojo, JuanTue, 02 Feb 2016 06:36:24 GMT29 Jan 2016arXiv:1602.00005http://cds.cern.ch/record/2128277['arXiv:1602.00005']arXiv:1602.00005Aspects of topological actions on the lattice
http://cds.cern.ch/record/2124518
We consider a lattice action which forbids large fields, and which remains invariant under smooth deformations of the field. Such a "topological" action depends on one parameter, the field cutoff, but does not have a classical continuum limit as this cutoff approaches zero. We study the properties of such an action in 4d compact U(1) lattice gauge theory, and compare them with those of the Wilson action. In both cases, we find a weakly first-order transition separating a confining phase where monopoles condense, and a Coulomb phase where monopoles are exponentially suppressed. We also find a different, critical value of the field cutoff where monopoles completely disappear. Finally, we show that a topological action simplifies the measurement of the free energy.Akerlund, Oscarde Forcrand, PhilippeMon, 18 Jan 2016 06:39:29 GMT15 Jan 2016arXiv:1601.03905http://cds.cern.ch/record/2124518['arXiv:1601.03905']arXiv:1601.03905Research infrastructures in the LHC era: a scientometric approach
http://cds.cern.ch/record/2124510
When a research infrastructure is funded and implemented, new information and new publications are created. This new information is the measurable output of discovery process. In this paper, we describe the impact of infrastructure for physics experiments in terms of publications and citations. In particular, we consider the Large Hadron Collider (LHC) experiments (ATLAS, CMS, ALICE, LHCb) and compare them to the Large Electron Positron Collider (LEP) experiments (ALEPH, DELPHI, L3, OPAL) and the Tevatron experiments (CDF, D0). We provide an overview of the scientific output of these projects over time and highlight the role played by remarkable project results in the publication-citation distribution trends. The methodological and technical contribution of this work provides a starting point for the development of a theoretical model of modern scientific knowledge propagation over time.Carrazza, StefanoFerrara, AlfioSalini, SilviaMon, 18 Jan 2016 06:38:34 GMT14 Jan 2016arXiv:1601.03746http://cds.cern.ch/record/2124510['arXiv:1601.03746']arXiv:1601.03746Statistical anisotropy from inflationary magnetogenesis
http://cds.cern.ch/record/2124315
Provided the quantum fluctuations are amplified in the presence of a classical gauge field configuration the resulting curvature perturbations exhibit a mild statistical anisotropy which should be sufficiently weak not to conflict with current observational data. The curvature power spectra induced by weakly anisotropic initial states are computed here for the first time when the electric and the magnetic gauge couplings evolve at different rates as it happens, for instance, in the relativistic theory of van der Waals interactions. After recovering the results valid for coincident gauge couplings, the constraints imposed by the isotropy and the homogeneity of the initial states are discussed. The obtained bounds turn out to be more stringent than naively expected and cannot be ignored when discussing the underlying magnetogenesis scenarios.Giovannini, MassimoSat, 16 Jan 2016 07:21:52 GMT14 Jan 2016arXiv:1601.03556http://cds.cern.ch/record/2124315['arXiv:1601.03556']arXiv:1601.03556Mean distribution approach to spin and gauge theories
http://cds.cern.ch/record/2119710
We formulate self-consistency equations for the distribution of links in spin models and of plaquettes in gauge theories. This improves upon known mean-field, mean-link, and mean-plaquette approximations in such that we self-consistently determine all moments of the considered variable instead of just the first. We give examples in both Abelian and non-Abelian cases.Akerlund, Oscarde Forcrand, PhilippeFri, 08 Jan 2016 06:48:09 GMT06 Jan 2016arXiv:1601.01175http://cds.cern.ch/record/2119710['arXiv:1601.01175']arXiv:1601.01175Origins of the di-jet asymmetry in heavy ion collisions
http://cds.cern.ch/record/2118247
The di-jet asymmetry --- the measure of the momentum imbalance in a di-jet system --- is a key jet quenching observable. Using the event generator \jewel we show that the di-jet asymmetry is dominated by fluctuations both in proton-proton and in heavy ion collisions. We discuss how in proton-proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy ion collisions two additional sources contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable.Milhano, José GuilhermeZapp, Korinna ChristineTue, 29 Dec 2015 06:27:20 GMT26 Dec 2015arXiv:1512.08107http://cds.cern.ch/record/2118247['arXiv:1512.08107']arXiv:1512.08107Golden Probe of the Top Yukawa
http://cds.cern.ch/record/2118000
We describe how the Higgs decay to four leptons can be used to probe the nature and $CP$ structure of the top Yukawa coupling.Chen, YiStolarski, DanielVega-Morales, RobertoSat, 26 Dec 2015 06:26:46 GMT24 Dec 2015arXiv:1512.07859http://cds.cern.ch/record/2118000['arXiv:1512.07859']arXiv:1512.07859Theory Motivation For Exotic Signatures: Prospects and Wishlist for Run II
http://cds.cern.ch/record/2117999
Here I give some motivations for exotic signatures to search for at Run II of the LHC, focusing on displaced phenomena. I will discuss signatures arising from various different kinds of models including theories of dark matter and those with exotic decays of the Higgs.Stolarski, DanielSat, 26 Dec 2015 06:26:45 GMT24 Dec 2015arXiv:1512.07857http://cds.cern.ch/record/2117999['arXiv:1512.07857']arXiv:1512.07857Comments on the nilpotent constraint of the goldstino superfield
http://cds.cern.ch/record/2117819
Superfield constraints were often used in the past, in particular to describe the Akulov-Volkov action of the goldstino by a superfield formulation with $L=(\Phi^\dagger \Phi)_D + [(f\Phi)_F + h.c.]$ endowed with the nilpotent constraint $\Phi^2=0$ for the goldstino superfield ($\Phi$). Inspired by this, such constraint is often used to define the goldstino superfield even in the presence of additional superfields, for example in models of "nilpotent inflation". In this review we show that the nilpotent property is not valid in general, under the assumption of a microscopic (ultraviolet) description of the theory with linear supermultiplets. Sometimes only weaker versions of the nilpotent relation are true such as $\Phi^3=0$ or $\Phi^4=0$ ($\Phi^2\not=0$) in the infrared (far below the UV scale) under the further requirement of decoupling all additional scalars (coupling to sgoldstino), something not always possible (e.g. if light scalars exist). In such cases the weaker nilpotent property is not specific to the goldstino superfield anymore. We review the restrictions for the Kahler curvature tensor and superpotential $W$ under which $\Phi^2=0$ remains true in infrared, assuming linear supermultiplets in the microscopic description. One can reverse the arguments to demand that the nilpotent condition, initially an infrared property, be extended even in the presence of additional superfields, but this may question the nature of supersymmetry breaking or the existence of a perturbative ultraviolet completion with linear supermultiplets.Ghilencea, D MThu, 24 Dec 2015 07:39:29 GMT23 Dec 2015arXiv:1512.07484http://cds.cern.ch/record/2117819['arXiv:1512.07484']arXiv:1512.07484Trinification can explain the di-photon and di-boson LHC anomalies
http://cds.cern.ch/record/2117808
LHC data show a diphoton excess at 750 GeV and a less significant diboson excess around 1.9 TeV. We propose trinification as a common source of both anomalies. The 1.9 TeV excess can be produced by the lightest extra vector: a $W_R^\pm$ with a gauge coupling $g_R\approx 0.44$ that does not decay into leptons. Furthermore, trinification predicts extra scalars. One of them can reproduce the $\gamma\gamma$ excess while satisfying constraints from all other channels, given the specific set of extra fermions predicted by trinification.Pelaggi, Giulio MariaStrumia, AlessandroVigiani, ElenaThu, 24 Dec 2015 07:39:27 GMT22 Dec 2015arXiv:1512.07225http://cds.cern.ch/record/2117808['arXiv:1512.07225']arXiv:1512.07225Time-Sliced Perturbation Theory for Large Scale Structure I: General Formalism
http://cds.cern.ch/record/2117189
We present a new analytic approach to describe large scale structure formation in the mildly non-linear regime. The central object of the method is the time-dependent probability distribution function generating correlators of the cosmological observables at a given moment of time. Expanding the distribution function around the Gaussian weight we formulate a perturbative technique to calculate non-linear corrections to cosmological correlators, similar to the diagrammatic expansion in a three-dimensional Euclidean quantum field theory, with time playing the role of an external parameter. For the physically relevant case of cold dark matter in an Einstein--de Sitter universe, the time evolution of the distribution function can be found exactly and is encapsulated by a time-dependent coupling constant controlling the perturbative expansion. We show that all building blocks of the expansion are free from spurious infrared enhanced contributions that plague the standard cosmological perturbation theory. This paves the way towards the systematic resummation of infrared effects in large scale structure formation. We also argue that the approach proposed here provides a natural framework to account for the influence of short-scale dynamics on larger scales along the lines of effective field theory.Blas, DiegoGarny, MathiasIvanov, Mikhail MSibiryakov, SergeyTue, 22 Dec 2015 07:24:11 GMT17 Dec 2015arXiv:1512.05807http://cds.cern.ch/record/2117189['arXiv:1512.05807']arXiv:1512.05807Weak and strong coupling equilibration in nonabelian gauge theories
http://cds.cern.ch/record/2116964
We present a direct comparison studying equilibration through kinetic theory at weak coupling and through holography at strong coupling in the same set-up. The set-up starts with a homogeneous thermal state, which then smoothly transitions through an out-of-equilibrium phase to an expanding system undergoing boost-invariant flow. This first apples-to-apples comparison of equilibration provides a benchmark for similar equilibration processes in heavy-ion collisions, where the equilibration mechanism is still under debate. We find that results at weak and strong coupling can be smoothly connected by simple, empirical power-laws for the viscosity, equilibration time and entropy production of the system.Keegan, LiamKurkela, AleksiRomatschke, Paulvan der Schee, WilkeZhu, YanSat, 19 Dec 2015 07:37:32 GMT16 Dec 2015arXiv:1512.05347http://cds.cern.ch/record/2116964['arXiv:1512.05347']arXiv:1512.05347Lattice simulation of the SU(2) chiral model at zero and non-zero pion density
http://cds.cern.ch/record/2116960
We propose a flux representation based lattice formulation of the partition function corresponding to the SU(2) principal chiral Lagrangian, including a chemical potential and scalar/pseudo-scalar source terms. Lattice simulations are then used to obtain non-perturbative properties of the theory, in particular its mass spectrum at zero and non-zero pion density. We also sketch a method to efficiently measure general one- and two-point functions during the worm updates.Rindlisbacher, Tobiasde Forcrand, PhilippeSat, 19 Dec 2015 07:37:05 GMT17 Dec 2015arXiv:1512.05684http://cds.cern.ch/record/2116960['arXiv:1512.05684']arXiv:1512.05684Post-Inflationary Gravitino Production Revisited
http://cds.cern.ch/record/2116906
We revisit gravitino production following inflation. As a first step, we review the standard calculation of gravitino production in the thermal plasma formed at the end of post-inflationary reheating when the inflaton has completely decayed. Next we consider gravitino production prior to the completion of reheating, assuming that the inflaton decay products thermalize instantaneously while they are still dilute. We then argue that instantaneous thermalization is in general a good approximation, and also show that the contribution of non-thermal gravitino production via the collisions of inflaton decay products prior to thermalization is relatively small. Our final estimate of the gravitino-to-entropy ratio is approximated well by a standard calculation of gravitino production in the post-inflationary thermal plasma assuming total instantaneous decay and thermalization at a time $t \simeq 1.2/\Gamma_\phi$. Finally, in light of our calculations, we consider potential implications of upper limits on the gravitino abundance for models of inflation, with particular attention to scenarios for inflaton decays in supersymmetric Starobinsky-like models.Ellis, JohnGarcia, Marcos A GNanopoulos, Dimitri VOlive, Keith APeloso, MarcoSat, 19 Dec 2015 07:34:42 GMT17 Dec 2015arXiv:1512.05701http://cds.cern.ch/record/2116906['arXiv:1512.05701']arXiv:1512.05701The sensitivity of R_pA to color recombination effects
http://cds.cern.ch/record/2115635
In hadronization models with color recombination, partons are allowed to regroup into color singlet structures that are different from those determined by the perturbative parton shower. This aims at modeling the possibility that soft interactions of partons with the underlying event can change color connections. If such an effect is at play in proton-proton collisions, it may be expected to be enhanced in proton-nucleus collisions due to the higher color charge density in the underlying event. Here, we provide a qualitative argument that color recombination effects could lead to a multiplicity dependent hardening of single inclusive hadron spectra that dies out very weakly with increasing transverse momentum. We present results of a (conservative) model implementation in the cluster hadronization model of the SHERPA event generator. In this model, we find that color recombination effects harden indeed the single inclusive hadron spectra without affecting the jet spectra, but that this effect does not depend significantly on underlying event activity. We explain this model feature and we argue why, in general, data on proton-nucleus collisions can help to constrain hadronization models used in proton-proton event generators.Zapp, Korinna ChristinaMilhano, GuilhermeWiedemann, Urs AchimThu, 17 Dec 2015 08:42:17 GMT16 Dec 2015arXiv:1512.05196http://cds.cern.ch/record/2115635['arXiv:1512.05196']arXiv:1512.05196On the Interpretation of a Possible $\sim 750$ GeV Particle Decaying into $\gamma \gamma$
http://cds.cern.ch/record/2115616
We consider interpretations of the recent $\sim 3 \sigma$ reports by the CMS and ATLAS collaborations of a possible $X(\sim 750~{\rm GeV})$ state decaying into $\gamma \gamma$ final states. We focus on the possibilities that this is a scalar or pseudoscalar electroweak isoscalar state produced by gluon-gluon fusion mediated by loops of heavy fermions. We consider several models for these fermions, including a single vector-like charge $2/3$ T quark, a doublet of vector-like quarks $(T, B)$, and a vector-like generation of quarks, with or without leptons that also contribute to the $X \to \gamma \gamma$ decay amplitude. We also consider the possibility that $X(750)$ is a dark matter mediator, with a neutral vector-like dark matter particle. These scenarios are compatible with the present and prospective direct limits on vector-like fermions from LHC Runs 1 and 2, as well as indirect constraints from electroweak precision measurements, and we show that the required Yukawa-like couplings between the $X$ particle and the heavy vector-like fermions are small enough to be perturbative so long as the $X$ particle has dominant decay modes into $gg$ and $\gamma \gamma$. The decays $X \to Z Z, Z \gamma$ and $W^+ W^-$ are interesting prospective signatures that may help distinguish between different vector-like fermion scenarios.Ellis, JohnEllis, Sebastian A RQuevillon, JérémieSanz, VeronicaYou, TevongThu, 17 Dec 2015 08:39:23 GMT16 Dec 2015arXiv:1512.05327http://cds.cern.ch/record/2115616['arXiv:1512.05327']arXiv:1512.05327What is the gamma gamma resonance at 750 GeV?
http://cds.cern.ch/record/2115101
Run 2 LHC data show hints of a new resonance in the diphoton distribution at an invariant mass of 750 GeV. We analyse the data in terms of a new boson, extracting information on its properties and exploring theoretical interpretations. Scenarios covered include a narrow resonance and, as preliminary indications suggest, a wider resonance. If the width indications persist, the new particle is likely to belong to a strongly-interacting sector. We also show how compatibility between Run 1 and Run 2 data is improved by postulating the existence of an additional heavy particle, whose decays are possibly related to dark matter.Franceschini, RobertoGiudice, Gian FKamenik, Jernej FMcCullough, MatthewPomarol, AlexRattazzi, RiccardoRedi, MicheleRiva, FrancescoStrumia, AlessandroTorre, RiccardoWed, 16 Dec 2015 07:05:36 GMT15 Dec 2015arXiv:1512.04933http://cds.cern.ch/record/2115101['arXiv:1512.04933']arXiv:1512.04933The Universal One-Loop Effective Action
http://cds.cern.ch/record/2112531
We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.Drozd, AleksandraEllis, JohnQuevillon, JérémieYou, TevongFri, 11 Dec 2015 07:19:33 GMT09 Dec 2015arXiv:1512.03003http://cds.cern.ch/record/2112531['arXiv:1512.03003']arXiv:1512.03003ALPtraum: ALP production in proton beam dump experiments
http://cds.cern.ch/record/2112501
With their high beam energy and intensity, existing and near-future proton beam dumps provide an excellent opportunity to search for new very weakly coupled particles in the MeV to GeV mass range. One particularly interesting example is a so-called axion-like particle (ALP), i.e. a pseudoscalar coupled to two photons. The challenge in proton beam dumps is to reliably calculate the production of the new particles from the interactions of two composite objects, the proton and the target atoms. In this work we argue that Primakoff production of ALPs proceeds in a momentum range where production rates and angular distributions can be determined to sufficient precision using simple electromagnetic form factors. Reanalysing past proton beam dump experiments for this production channel, we derive novel constraints on the parameter space for ALPs. We show that the NA62 experiment at CERN could probe unexplored parameter space by running in 'dump mode' for a few days and discuss opportunities for future experiments such as SHiP.Döbrich, BabetteJaeckel, JoergKahlhoefer, FelixRingwald, AndreasSchmidt-Hoberg, KaiFri, 11 Dec 2015 07:17:16 GMT09 Dec 2015arXiv:1512.03069http://cds.cern.ch/record/2112501['arXiv:1512.03069']arXiv:1512.03069Energy spectra of massive two-body decay products and mass measurement
http://cds.cern.ch/record/2111823
We have recently established a new method for measuring the mass of unstable particles produced at hadron colliders based on the analysis of the energy distribution of a massless product from their two-body decays. The central ingredient of our proposal is the remarkable result that, for an unpolarized decaying particle, the location of the peak in the energy distribution of the observed decay product is identical to the (fixed) value of the energy that this particle would have in the rest-frame of the decaying particle, which, in turn, is a simple function of the involved masses. In addition, we utilized the property that this energy distribution is symmetric around the location of peak when energy is plotted on a logarithmic scale. The general strategy was demonstrated in several specific cases, including both beyond the SM particles, as well as for the top quark. In the present work, we generalize this method to the case of a massive decay product from a two-body decay; this procedure is far from trivial because (in general) both the above- mentioned properties are no longer valid. Nonetheless, we propose a suitably modified parametrization of the energy distribution that was used successfully for the massless case, which can deal with the massive case as well. We establish the accuracy of this parametrization using concrete examples of energy spectra of Z bosons from the decay of a heavier stop into a Z boson and a lighter stop. We then study a realistic application for the same process, but now including dominant backgrounds and using foreseeable statistics at LHC14, in order to determine the performance of this method for an actual mass measurement. The upshot of our present and previous work is that, in spite of energy being a Lorentz-variant quantity, its distribution emerges as a powerful tool for mass measurement at hadron colliders.Agashe, KaustubhFranceschini, RobertoHong, SungwooKim, DoojinWed, 09 Dec 2015 08:35:05 GMT07 Dec 2015arXiv:1512.02265http://cds.cern.ch/record/2111823['arXiv:1512.02265']arXiv:1512.02265Complete Normal Ordering 1: Foundations
http://cds.cern.ch/record/2111761
We introduce a new prescription for quantising scalar field theories perturbatively around a true minimum of the full quantum effective action, which is to `complete normal order' the bare action of interest. When the true vacuum of the theory is located at zero field value, the key property of this prescription is the automatic cancellation, to any finite order in perturbation theory, of all tadpole and, more generally, all `cephalopod' Feynman diagrams. The latter are connected diagrams that can be disconnected into two pieces by cutting one internal vertex, with either one or both pieces free from external lines. In addition, this procedure of `complete normal ordering' (which is an extension of the standard field theory definition of normal ordering) reduces by a substantial factor the number of Feynman diagrams to be calculated at any given loop order. We illustrate explicitly the complete normal ordering procedure and the cancellation of cephalopod diagrams in scalar field theories with non-derivative interactions, and by using a point splitting `trick' we extend this result to theories with derivative interactions, such as those appearing as non-linear sigma-models in the world-sheet formulation of string theory. We focus here on theories with trivial vacua, generalising the discussion to non-trivial vacua in a follow-up paper.Ellis, JohnMavromatos, Nick ESkliros, Dimitri PWed, 09 Dec 2015 08:31:27 GMT08 Dec 2015arXiv:1512.02604http://cds.cern.ch/record/2111761['arXiv:1512.02604']arXiv:1512.02604Renormalization of Horava Gravity
http://cds.cern.ch/record/2111753
We prove perturbative renormalizability of projectable Horava gravity. The key element of the argument is the choice of a gauge which ensures the correct anisotropic scaling of the propagators and their uniform falloff at large frequencies and momenta. This guarantees that the counterterms required to absorb the loop divergences are local and marginal or relevant with respect to the anisotropic scaling. Gauge invariance of the counterterms is achieved by making use of the background-covariant formalism. We also comment on the difficulties of this approach when addressing the renormalizability of the non-projectable model.Barvinsky, Andrei OBlas, DiegoHerrero-Valea, MarioSibiryakov, Sergey MSteinwachs, Christian FWed, 09 Dec 2015 08:31:25 GMT07 Dec 2015arXiv:1512.02250http://cds.cern.ch/record/2111753['arXiv:1512.02250']arXiv:1512.02250Quantum mechanics of 4-derivative theories
http://cds.cern.ch/record/2111085
A renormalizable theory of gravity is obtained if the dimension-less 4-derivative kinetic term of the graviton, which classically suffers from negative unbounded energy, admits a sensible quantisation. We find that a 4-derivative degree of freedom involves a canonical coordinate with unusual time-inversion parity, and that a correspondingly unusual representation must be employed for the relative quantum operator. The resulting theory has positive energy eigenvalues, normalisable wave functions, unitary evolution in a negative-norm configuration space. We present a formalism for quantum mechanics with a generic norm.Salvio, AlbertoStrumia, AlessandroMon, 07 Dec 2015 06:50:09 GMT03 Dec 2015arXiv:1512.01237http://cds.cern.ch/record/2111085['arXiv:1512.01237']arXiv:1512.01237Herwig 7.0 / Herwig++ 3.0 Release Note
http://cds.cern.ch/record/2110873
A major new release of the Monte Carlo event generator Herwig++ (version 3.0) is now available. This release marks the end of distinguishing Herwig++ and HERWIG development and therefore constitutes the first major release of version 7 of the Herwig event generator family. The new version features a number of significant improvements to the event simulation, including: built-in NLO hard process calculation for all Standard Model processes, with matching to both angular-ordered and dipole shower modules via both subtractive (MC@NLO-type) and multiplicative (Powheg-type) algorithms; QED radiation and spin correlations in the angular ordered shower; a consistent treatment of perturbative uncertainties within the hard process and parton showering. Several of the new features will be covered in detail in accompanying publications, and an update of the manual will follow in due course.Bellm, JohannesGieseke, StefanGrellscheid, DavidPlätzer, SimonRauch, MichaelReuschle, ChristianRichardson, PeterSchichtel, PeterSeymour, Michael HSiódmok, AndrzejWilcock, AlexandraFischer, NadineHarrendorf, Marco ANail, GraemePapaefstathiou, AndreasRauch, DanielSat, 05 Dec 2015 06:45:12 GMT03 Dec 2015arXiv:1512.01178http://cds.cern.ch/record/2110873['arXiv:1512.01178']arXiv:1512.01178