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The Top Mass in Hadronic Collisions
http://cds.cern.ch/record/2300413
I discuss theoretical issues related to the top mass measurements in hadronic collisions.Nason, PaoloWed, 17 Jan 2018 06:37:46 GMT2017-12-07CERN-TH-2017-266http://cds.cern.ch/record/23004132017266Counting of oscillatory modes of valence quarks forming qqq baryons for 3 quark flavors u,d,s
http://cds.cern.ch/record/2300410
We present a selection the unique properties of oscillatory modes of N fl = 3 light quarks -u, d, s-, using the broken symmetry classification. stands for the space rotation group generated by the sum of the three individual angular momenta of quarks in their c.m. system. The baryonic multiplets are shown to emerge from the picture of oscillating quarks in 3 space dimensions in the center of mass system of the baryons. All oscillatory modes are fully relativistic with a finite number of oscillators and ths is forming the unique harmonic oscillators with these properties. The density of states as a function of mass-square is calculated. This estimate is of relevance for the accounting of the missing states of unobserved hadrons, as the here estimated baryonic multiplets include both the observed and the unobserved (or “missing”) hadrons. The estimate is conceptually different from Hagedorn’s model and is based on field theory of QCD.Kabana, SoniaMinkowski, PeterWed, 17 Jan 2018 05:02:26 GMThttp://cds.cern.ch/record/2300410['']Comparing the $R_\xi$ gauge and the unitary gauge for the standard model: An example
http://cds.cern.ch/record/2300397
For gauge theory, the matrix element for any physical process is independent of the gauge used. However, since this is a formal statement, it does not guarantee this gauge independence in every case. An example is given here where, for a physical process in the standard model, the matrix elements calculated with two different gauge – the Rξ gauge and the unitary gauge – are explicitly verified to be different. This is accomplished by subtracting one matrix element from the other. This non-zero difference turns out to have a subtle origin. Two simple operators are found not to commute with each other: in one gauge these two operations are carried out in one order, while in the other gauge these same two operations are carried out in the opposite order. Because of this result, a series of question are raised such that the answers to these question may lead to a deeper understanding of the Yang–Mills non-Abelian gauge theory in general and the standard model in particular.Wu, Tai TsunWu, Sau LanWed, 17 Jan 2018 05:02:10 GMThttp://cds.cern.ch/record/2300397['']Multi Quark Production in p+A collisions: Quantum Interference Effects
http://cds.cern.ch/record/2300290
We consider forward inclusive production of several quarks in the high energy p-A collisions in the CGC formalism. For three particle production we provide a complete expression in terms of multipole scattering amplitudes on the nucleus and multi particle generalized TMD's of the proton. We then calculate all the terms that are not suppressed by the factor of the area in four particle production, and generalize this result up to terms of order $1/N_c^2$ for arbitrary number of produced particles. Our results include the contribution of quantum interference effects both in the final state radiation (HBT) and in the initial projectile wave function (Pauli blocking).Kovner, AlexRezaeian, Amir H.Tue, 16 Jan 2018 06:49:43 GMT2018-01-15CERN-TH-2018-007http://cds.cern.ch/record/23002902018007Serendipity in dark photon searches
http://cds.cern.ch/record/2300288
Searches for dark photons provide serendipitous discovery potential for other types of vector particles. We develop a framework for recasting dark photon searches to obtain constraints on more general theories, which includes a data-driven method for determining hadronic decay rates. We demonstrate our approach by deriving constraints on a vector that couples to the $B\!-\!L$ current, a leptophobic $B$ boson that couples directly to baryon number and to leptons via $B$-$\gamma$ kinetic mixing, and on a vector that mediates a protophobic force. Our approach can easily be generalized to any massive gauge boson with vector couplings to the Standard Model fermions, and software to perform any such recasting is provided at https://gitlab.com/philten/darkcast .Ilten, PhilipSoreq, YotamWilliams, MikeXue, WeiTue, 16 Jan 2018 06:49:20 GMT2018-01-15MIT-CTP/4976http://cds.cern.ch/record/2300288MITCTP/4976The Top Quark Mass at the LHC
http://cds.cern.ch/record/2300287
I briefly discuss some theoretical aspects of top mass measurements at the LHC. In particular, I illustrate a recent theoretical study performed using next-to-leading order (NLO) calculations interfaced to shower generators (NLO+PS) of increasing accuracy, interfaced to both Pythia8 and Herwig7 Monte Carlo generators.Nason, PaoloTue, 16 Jan 2018 06:49:20 GMT2018-01-15CERN-TH-2018-008http://cds.cern.ch/record/23002872018008Elliptic polylogarithms and iterated integrals on elliptic curves I: general formalism
http://cds.cern.ch/record/2300275
We introduce a class of iterated integrals, defined through a set of linearly independent integration kernels on elliptic curves. As a direct generalisation of multiple polylogarithms, we construct our set of integration kernels ensuring that they have at most simple poles, implying that the iterated integrals have at most logarithmic singularities. We study the properties of our iterated integrals and their relationship to the multiple elliptic polylogarithms from the mathematics literature. On the one hand, we find that our iterated integrals span essentially the same space of functions as the multiple elliptic polylogarithms. On the other, our formulation allows for a more direct use to solve a large variety of problems in high-energy physics. We demonstrate the use of our functions in the evaluation of the Laurent expansion of some hypergeometric functions for values of the indices close to half integers.Broedel, JohannesDuhr, ClaudeDulat, FalkoTancredi, LorenzoTue, 16 Jan 2018 05:45:37 GMT2017-12-19arXiv:1712.07089http://cds.cern.ch/record/2300275['arXiv:1712.07089']arXiv:1712.07089Quantum corrections to quartic inflation with a non-minimal coupling: metric vs. Palatini
http://cds.cern.ch/record/2300274
We study models of quartic inflation where the inflaton field $\phi$ is coupled non-minimally to gravity, $\xi \phi^2 R$, and perform a study of quantum corrections in curved space-time at one-loop level. We specifically focus on comparing results between the metric and Palatini theories of gravity. Transformation from the Jordan to the Einstein frame gives different results for the two formulations. By using an effective field theory expansion we derive the appropriate $\beta$-functions and the renormalisation group improved effective potentials in curved space for both cases in the Einstein frame. In particular, we show that in both formalisms the Einstein frame depends on the order of perturbation theory but that the flatness of the potential is unaltered by quantum corrections.Markkanen, TommiTenkanen, TommiVaskonen, VilleVeermäe, HardiTue, 16 Jan 2018 05:45:36 GMT2017-12-13arXiv:1712.04874http://cds.cern.ch/record/2300274['arXiv:1712.04874']arXiv:1712.048742d orbifolds with exotic supersymmetry
http://cds.cern.ch/record/2300273
We analyse various two dimensional theories arising from compactification of type II and heterotic string theory on asymmetric orbifolds. We find extra supersymmetry generators arising from twisted sectors, giving rise to exotic supersymmetry algebras. Among others we discover new cases with a large number of supercharges, such as $\mathcal{N}=(20,8)$, $\mathcal{N}=(24,8)$, $\mathcal{N}=(32,0)$, $\mathcal{N}=(24,24)$ and $\mathcal{N}=(48,0)$.Florakis, IoannisGarcía-Etxebarria, IñakiLust, DieterRegalado, DiegoTue, 16 Jan 2018 05:45:33 GMT2017-12-12arXiv:1712.04318http://cds.cern.ch/record/2300273['arXiv:1712.04318']arXiv:1712.04318Understanding the Impact of Pythia Hadronization in Top Quark Mass Determinations at the LHC
http://cds.cern.ch/record/2300147
Most of the methods to measure the top quark mass suffer from the jet energy scaling in achieving better precision. As a way to circumvent this issue, the study of $B$-hadron observables is motivated. While they do not involve such an issue, understanding underlying hadronization models is a key to achieve $\sim 0.5\%$ precision or better. In this presentation, we discuss the impact of the hadronization model parameters - for example, implemented in Pythia 8 - on precision measurements of the top quark mass through $B$-hadron observables. We study the sensitivity of the top quark mass to relevant hadronization and showering parameters, followed by a discussion on observables to be used for constraining the hadronization and showering parameters.Kim, DoojinMon, 15 Jan 2018 07:06:04 GMT2018-01-12CERN-TH-2018-006http://cds.cern.ch/record/23001472018006A Theoretical Study of Top-Mass Measurements at the LHC Using NLO+PS Generators of Increasing Accuracy
http://cds.cern.ch/record/2300146
In this paper we study the theoretical uncertainties in the determination of the top-quark mass using next-to-leading-order (NLO) generators interfaced to parton showers (PS) that have different levels of accuracy. Specifically we consider three generators: one that implements NLO corrections in the production dynamics, one that includes also NLO corrections in top decay in the narrow width approximation, and one that implements NLO corrections for both production and decay including finite-width and interference effects. Our aim is to provide an assessment of the uncertainties of purely theoretical origin, we thus consider simplified top-mass related observables that are broadly related to those effectively used by experiments, eventually modelling experimental resolution effects with simple smearing procedures. Examining these observables with generators of increasing accuracy allows us to assess the theoretical errors due to the use of the less accurate generators. Furthermore, we estimate theoretical uncertainties associated with the variation of scales and with the choice of parton distribution functions. In order to give an indicative assessment of the uncertainties due to the shower and to the modelling of non-perturbative effects, we interface our NLO+PS generators to both Pythia8.2 and Herwig7.1, with various settings, and compare the results.Ferrario Ravasio, SilviaJezo, TomasNason, PaoloOleari, CarloMon, 15 Jan 2018 07:05:56 GMT2018-01-11CERN-TH-2018-001-ZU-TH-01-18http://cds.cern.ch/record/23001460118Recent $\boldsymbol{B}$ Physics Anomalies - a First Hint for Compositeness?
http://cds.cern.ch/record/2300085
We scrutinize the recently further strengthened hints for new physics in semileptonic $B$-meson decays, focusing on the 'clean' ratios of branching fractions $R_K$ and $R_{K^\ast}$ and examining to which pattern of new effects they point to. We explore in particular the hardly considered, yet fully viable, option of new physics in the right-handed electron sector and demonstrate how a recently proposed framework of leptons in composite Higgs setups naturally solves both the $R_K$ and $R_{K^\ast}$ anomalies via a peculiar structure of new physics effects, predicted by minimality of the model and the scale of neutrino masses. Finally, we also take into account further observables, such as ${\cal B}(B_s \to \mu^+\mu^-)$, $\Delta M_{B_s}$, and angular observables in $B \to K^{\ast} \mu^+ \mu^-$ decays, to arrive at a comprehensive picture of the model concerning (semileptonic) $B$ decays. We conclude that -- since it is in good agreement with the experimental situation in flavor physics and also allows to avoid ultra-light top partners -- the model furnishes a very promising scenarios of Higgs compositeness in the light of LHC data.Carmona, AdriánGoertz, FlorianSat, 13 Jan 2018 05:24:17 GMT2017-12-07arXiv:1712.02536http://cds.cern.ch/record/2300085['arXiv:1712.02536']arXiv:1712.02536Catching a New Force by the Tail
http://cds.cern.ch/record/2300084
The Large Hadron Collider (LHC) is sensitive to new heavy gauge bosons that produce narrow peaks in the dilepton invariant mass spectrum up to about $m_{Z'}\sim 5$ TeV. $Z'$s that are too heavy to produce directly can reveal their presence through interference with Standard Model dilepton production. We show that the LHC can significantly extend the mass reach for such $Z'$s by performing precision measurements of the shape of the dilepton invariant mass spectrum. The high luminosity LHC can exclude, with 95$\%$ confidence, new gauge bosons as heavy as $m_{Z'} \sim 10-20$ TeV that couple with gauge coupling strength of $g_{Z'} \sim 1-2$.Alioli, SimoneFarina, MarcoPappadopulo, DuccioRuderman, Joshua T.Sat, 13 Jan 2018 05:24:16 GMT2017-12-06arXiv:1712.02347http://cds.cern.ch/record/2300084['arXiv:1712.02347']arXiv:1712.02347Machine learning challenges in theoretical HEP
http://cds.cern.ch/record/2300083
In these proceedings we perform a brief review of machine learning (ML) applications in theoretical High Energy Physics (HEP-TH). We start the discussion by defining and then classifying machine learning tasks in theoretical HEP. We then discuss some of the most popular and recent published approaches with focus on a relevant case study topic: the determination of parton distribution functions (PDFs) and related tools. Finally, we provide an outlook about future applications and developments due to the synergy between ML and HEP-TH.Carrazza, StefanoSat, 13 Jan 2018 05:24:15 GMT2017-11-29CERN-TH-2017-212http://cds.cern.ch/record/23000832017212Penrose limits of Abelian and non-Abelian T-duals of $AdS_5\times S^5$ and their field theory duals
http://cds.cern.ch/record/2300082
We consider the backgrounds obtained by Abelian and non-Abelian T-duality applied on $AdS_5\times S^5$. We study geodesics, calculate Penrose limits and find the associated plane-wave geometries. We quantise the weakly coupled type-IIA string theory on these backgrounds. We study the BMN sector, finding operators that wrap the original quiver CFT. For the non-Abelian plane wave, we find a 'flow' in the frequencies. We report some progress to understand this, in terms of deconstruction of a higher dimensional field theory. We explore a relation with the plane-wave limit of the Janus solution, which we also provide.Itsios, GeorgiosNastase, HoratiuNúñez, CarlosSfetsos, KonstantinosZacarías, SalomónSat, 13 Jan 2018 05:24:14 GMT2017-11-27arXiv:1711.09911http://cds.cern.ch/record/2300082['arXiv:1711.09911']arXiv:1711.09911Effective description of general extensions of the Standard Model: the complete tree-level dictionary
http://cds.cern.ch/record/2300081
We compute all the tree-level contributions to the Wilson coefficients of the dimension-six Standard-Model effective theory in ultraviolet completions with general scalar, spinor and vector field content and arbitrary interactions. No assumption about the renormalizability of the high-energy theory is made. This provides a complete ultraviolet/infrared dictionary at the classical level, which can be used to study the low-energy implications of any model of interest, and also to look for explicit completions consistent with low-energy data.de Blas, J.Criado, J.C.Perez-Victoria, M.Santiago, J.Sat, 13 Jan 2018 05:24:12 GMT2017-11-28arXiv:1711.10391http://cds.cern.ch/record/2300081['arXiv:1711.10391']arXiv:1711.10391Minimisation strategies for the determination of parton density functions
http://cds.cern.ch/record/2300080
We discuss the current minimisation strategies adopted by research projects involving the determination of parton distribution functions (PDFs) and fragmentation functions (FFs) through the training of neural networks. We present a short overview of a proton PDF determination obtained using the covariance matrix adaptation evolution strategy (CMA-ES) optimisation algorithm. We perform comparisons between the CMA-ES and the standard nodal genetic algorithm (NGA) adopted by the NNPDF collaboration.Carrazza, StefanoHartland, Nathan P.Sat, 13 Jan 2018 05:24:12 GMT2017-11-27arXiv:1711.09991http://cds.cern.ch/record/2300080['arXiv:1711.09991']arXiv:1711.09991Dedicated Strategies for Triboson Signals from Cascade Decays of Vector Resonances
http://cds.cern.ch/record/2300079
New colorless electroweak (EW) charged spin-1 particles with mass of a few TeV arise in numerous extensions of the Standard Model (SM). Decays of such a vector into a pair of SM particles, either fermions or EW bosons, are well studied. Many of these models have an additional scalar, which can lead to (and even dominate in certain parameter regions) a novel decay channel for the heavy vector particles instead - into a SM EW boson and the scalar, which subsequently decays into a SM EW boson pair. In this work, we focus on the scalar being relatively heavy, roughly factor of two lighter than the vector particles, rendering its decay products well separated. Such a cascade decay results in a final state with three isolated bosons. We argue that for this "triboson" signal the existing diboson searches are not quite optimal due to combinatorial ambiguity for three identical bosons, and in addition, due to a relatively small signal cross-section determined by the heaviness of the decaying vector particle. In order to isolate the signal, we demonstrate that tagging all three bosons, followed by use of the full triboson invariant mass distribution as well as that of appropriate subsets of dibosons, is well motivated. We develop these general strategies in detail within the context of a specific class of models that are based on extensions of the standard warped extra-dimensional scenario. We also point out that a similar analysis would apply to models with an enlarged EW gauge sector in four dimensions, even if they involve a different Lorentz structure for the relevant couplings.Agashe, KaustubhCollins, Jack H.Du, PeizhiHong, SungwooKim, DoojinMishra, Rashmish K.Sat, 13 Jan 2018 05:24:10 GMT2017-11-27arXiv:1711.09920http://cds.cern.ch/record/2300079['arXiv:1711.09920']arXiv:1711.09920Black hole superradiance and polarization-dependent bending of light
http://cds.cern.ch/record/2300078
An inhomogeneous pseudo-scalar field configuration behaves like an optically active medium. Consequently, if a light ray passes through an axion cloud surrounding a Kerr black hole, it may experience a polarization-dependent bending. We explore the size and relevance of such effect considering both the QCD axion and a generic axion-like particle.Plascencia, Alexis D.Urbano, AlfredoSat, 13 Jan 2018 05:24:09 GMT2017-11-22arXiv:1711.08298http://cds.cern.ch/record/2300078['arXiv:1711.08298']arXiv:1711.08298Transverse single spin asymmetry in $p+p^\uparrow \rightarrow J/\psi +X$
http://cds.cern.ch/record/2300077
We present estimates of transverse single spin asymmetry (TSSA) in $p+p^\uparrow \rightarrow J/\psi+X$ within the colour evaporation model of charmonium production in a generalized parton model (GPM) framework, using the recently obtained best fit parameters for the gluon Sivers function (GSF) extracted from PHENIX data on TSSA in $p+p^\uparrow \to \pi^0+X$ at midrapidity. We calculate asymmetry at $\sqrt{s} = 200$ GeV, and compare the results with PHENIX data on TSSA in the process $p + p^\uparrow \to J/\psi+X$. We also present estimates for asymmetry at $\sqrt{s} = 115 $ GeV corresponding to the proposed fixed target experiment AFTER@LHC and at $\sqrt{s} = 500$ GeV corresponding to the higher RHIC energy. Finally, we investigate the effect of the transverse momentum dependent (TMD) evolution of the densities involved, on the asymmetry.Godbole, Rohini M.Kaushik, AbhiramMisra, AnuradhaRawoot, VaibhavSonawane, BipinSat, 13 Jan 2018 05:24:07 GMT2017-03-06arXiv:1703.01991http://cds.cern.ch/record/2300077['arXiv:1703.01991']arXiv:1703.01991Colored Dark Matter
http://cds.cern.ch/record/2299437
We explore the possibility that Dark Matter is the lightest hadron made of two stable color octet Dirac fermions ${\cal Q}$. The cosmological DM abundance is reproduced for $M_{\cal Q}\approx 9.5$ TeV, compatibly with direct searches (the Rayleigh cross section, suppressed by $1/M_{\cal Q}^6$, is close to present bounds), indirect searches (enhanced by ${\cal Q}{\cal Q}+\bar{\cal Q}\bar{\cal Q}\to {\cal Q}\bar{\cal Q}+{\cal Q}\bar{\cal Q}$ recombination), and with collider searches (where ${\cal Q}$ manifests as tracks, pair produced via QCD). Hybrid hadrons, made of $\cal Q$ and of SM quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is $10^5$ times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles.De Luca, ValerioMitridate, AndreaRedi, MicheleSmirnov, JuriStrumia, AlessandroMon, 08 Jan 2018 07:04:18 GMT2018-01-03CERN-TH-2017-283http://cds.cern.ch/record/22994372017283Supersymmetric gauged matrix models from dimensional reduction on a sphere
http://cds.cern.ch/record/2299212
It was recently proposed that N=1 supersymmetric gauged matrix models have a duality of order four - that is, a quadrality - reminiscent of infrared dualities of SQCD theories in higher dimensions. In this note, we show that the zero-dimensional quadrality proposal can be infered from the two-dimensional Gadde-Gukov-Putrov triality. We consider two-dimensional N=(0,2) SQCD compactified on a sphere with the half-topological twist. For a convenient choice of R-charge, the zero-mode sector on the sphere gives rise to a simple N=1 gauged matrix model. Triality on the sphere then implies a triality relation for the supersymmetric matrix model, which can be completed to the full quadrality.Closset, CyrilGhim, DongwookSeong, Rak-KyeongMon, 01 Jan 2018 07:03:08 GMT2017-12-28CERN-TH-2017-284http://cds.cern.ch/record/22992122017284Riemann-Theta Boltzmann Machine
http://cds.cern.ch/record/2298977
A general Boltzmann machine with continuous visible and discrete integer valued hidden states is introduced. Under mild assumptions about the connection matrices, the probability density function of the visible units can be solved for analytically, yielding a novel parametric density function involving a ratio of Riemann-Theta functions. The conditional expectation of a hidden state for given visible states can also be calculated analytically, yielding a derivative of the logarithmic Riemann-Theta function. The conditional expectation can be used as activation function in a feedforward neural network, thereby increasing the modelling capacity of the network. Both the Boltzmann machine and the derived feedforward neural network can be successfully trained via standard gradient- and non-gradient-based optimization techniques.Krefl, DanielCarrazza, StefanoHaghighat, BabakKahlen, JensSat, 23 Dec 2017 08:35:11 GMT2017-12-20CERN-TH-2017-275http://cds.cern.ch/record/22989772017275NNLO QCD corrections to the transverse momentum distribution of weak gauge bosons
http://cds.cern.ch/record/2298974
The transverse momentum spectra of weak gauge bosons and their ratios probe the underlying dynamics and are crucial in testing our understanding of the Standard Model. They are an essential ingredient in precision measurements, such as the $\mathrm{W}$-boson mass extraction. To fully exploit the potential of the LHC data, we compute the second-order (NNLO) QCD corrections to the inclusive-$p_\mathrm{T}^\mathrm{W}$ spectrum as well as to the ratios of spectra for $\mathrm{W}^-/\mathrm{W}^+$ and $\mathrm{Z}/\mathrm{W}$. We find that the inclusion of NNLO QCD corrections considerably improves the theoretical description of the experimental CMS data and results in a substantial reduction of the residual scale uncertainties.Gehrmann-De Ridder, A.Gehrmann, T.Glover, E.W.N.Huss, A.Walker, D.M.Sat, 23 Dec 2017 08:35:04 GMT2017-12-20CERN-TH-2017-280http://cds.cern.ch/record/22989742017280Asymmetric dark matter: residual annihilations and self-interactions
http://cds.cern.ch/record/2298973
The putative discrepancies between observations of the small scale galactic structure and the predictions of collisionless cold dark matter may be resolved if dark matter possesses sizable self-interactions. The coupling of dark matter to a light force mediator can ensure sufficiently large self-interactions, reproduce the observed relic abundance via freeze-out and satisfy constraints from cluster mergers and direct detection. However, strong bounds on such scenarios still arise from indirect detection, particularly from the CMB and $\gamma$-rays observations. As a simple way to alleviate this tension, we consider the possibility of dark matter possessing a particle-antiparticle asymmetry. First, we point out that, contrary to the common perception, significant residual annihilations occur even for highly asymmetric dark matter coupled to light force carriers. We compute the indirect detection signals and corresponding constraints from the CMB, $\gamma$-ray, neutrino and antiproton searches. On this basis, we then identify the parameter space where the dark matter self-interactions are significant while evading the above bounds. While the direct detection constraints are not suppressed by the asymmetry, we show that they do not yet rule out this scenario, but provide a method for confirming it.Baldes, IasonCirelli, MarcoPanci, PaoloPetraki, KalliopiSala, FilippoTaoso, MarcoSat, 23 Dec 2017 08:35:02 GMT2017-12-20CERN-TH-2017-272http://cds.cern.ch/record/22989732017272