State of the art POWHEG generators for top mass measurements at the LHC

We study the theoretical uncertainties in the determination of the top-quark mass using next-to-leading-order (NLO) generators, that describe the top-quark decay at different levels of accuracy, interfaced to parton showers (PS). Specifically we consider one generator that implements NLO corrections only in the production dynamics, one that also takes them into account in the top-quark decay in the narrow width approximation (NWA) and one that implements them exactly, including finite-width and interference effects. We aim at assessing the errors in top-mass determinations of purely theoretical origin. We do so by measuring relative peak position shifts of $Wb$-jet mass distributions. Besides the theoretical errors due to the use of less accurate NLO+PS generators, we also explore uncertainties related to shower and modelling of non-perturbative effects by comparing the results obtained by interfacing our generators to both Pythia and Herwig shower Monte Carlos (SMCs).Comment: Proceedings of the XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2018), 16-20 April 2018, Kobe, Japa

Hadroproduction of four top quarks in the POWHEG BOX

We present a new Monte Carlo event generator for the hadronic production of four top quarks in the POWHEG BOX framework. Besides the dominant next-to-leading order QCD corrections at $\mathcal{O}(\alpha_s^5)$ we also include all subleading electroweak productions channels at leading-order accuracy. We validate our theoretical predictions by comparing to parton-shower matched predictions obtained within the MC@NLO framework for stable top quarks. Furthermore, we investigate in detail the various sources of theoretical uncertainties. Finally, we investigate a single lepton plus jets signature to study for the first time the impact of the electroweak production modes as well as spin-correlation effects at the fiducial level.Comment: 14 pages, 8 figures, 1 table, matches published versio

NLO+NLL limits on W′W' and Z′Z' gauge boson masses

QCD resummation predictions for the production of new charged ($W'$) and neutral ($Z'$) heavy gauge bosons decaying leptonically are presented. These results are obtained with our resummation code at next-to-leading order and next-to-leading logarithmic (NLO+NLL) accuracy. Our predictions are compared to PYTHIA at leading order (LO) supplemented with parton showers (PS) and FEWZ at NLO and next-to-next-to-leading order (NNLO) for the $p_T$-differential and total cross sections in the Sequential Standard Model (SSM) and general SU(2)$\times$SU(2)$\times$U(1) models. We show that the importance of resummation for total cross sections increases with the gauge boson mass. Finally, the latest ATLAS and CMS results are reinterpreted to derive new limits at NLO+NLL on $W'$ and $Z'$ boson masses in general extensions of the Standard Model.Comment: Proceeding of the XXIII International Workshop on Deep Inelastic Scattering and Related Subjects, April 27 - May 1, 2015, Southern Methodist University, Dallas, Texa

Can new heavy gauge bosons be observed in ultra-high energy cosmic neutrino events?

A wide range of models beyond the Standard Model predict charged and neutral resonances, generically called $W'$- and $Z'$-bosons, respectively. In this paper we study the impact of such resonances on the deep inelastic scattering of ultra-high energy neutrinos as well as on the resonant charged current $\bar\nu_e e^-$ scattering (Glashow resonance). We find that the effects of such resonances can not be observed with the Pierre Auger Observatory or any foreseeable upgrade of it.Comment: 5 pages, 2 figure

Vliv krytých call opcí na výkonnost portfolia

This thesis aims to evaluate the performance of a covered call strategy writ- ten on Exchange-traded funds compared to a buy-and-hold strategy of the Exchange-traded fund on the US stock market. The strategy is constructed us- ing at-the-money, two-percent and five-percent out-of-the-money call options. The premium for the former is taken from historical market data and for the latter two calculated using the Black-Scholes-Merton formula adjusted for div- idends. The results further provide a two-period distinction to better account for di erent market periods, namely Covid-19 and the geopolitical conflict in Ukraine. The results fail to show evidence of a significant di erence between a covered call strategy and the buy-and-hold strategy. However, we provide possible applications of the strategy in certain market settings. The perfor- mance is evaluated on the basis of annualized returns and standard deviation, as ratios based on the mean-variance framework are omitted due to possible bias of negatively skewed distribution of returns of the covered call strategy. JEL Classification G10, G11, G12, G13, C02 Keywords Covered calls, ETF, Black-Scholes model, Op- tions pricing, Portfolio performance Title E ect of covered calls on portfolio performanceCie om tejto práce je zhodnoti v˝konnos stratégie kryt˝ch call opcií vypísan˝ch na fondy obchodované na burze v porovnaní so stratégiou nákupu a drûa- nia dan˝ch fondov na americkom akciovom trhu. Stratégia je zostavená s pouûitím kúpnych opcií at-the-money, dvojpercentn˝ch a pä percentn˝ch out- of-the-money. Prémia pre prvú z nich je prevzatá z historick˝ch trhov˝ch údajov a pre druhé dve je vypo ítaná pomocou Black-Scholesovho-Mertonovho vzorca upraveného o dividendy. V˝sledky alej poskytujú rozlíöenie na dve ob- dobia, aby sa lepöie zoh adnili fluktuácie na trhu, konkrétne Covid-19 a geopol- itick˝ konflikt na Ukrajine. V˝sledky nepreukazujú v˝znamn˝ rozdiel medzi stratégiou kryt˝ch kúpnych opcií a stratégiou nákupu a drûania. Uvádzame vöak, ûe stratégiu je moûné vyuûi v ur it˝ch trhov˝ch podmienkach. V˝kon- nos sa hodnotí na základe anualizovan˝ch v˝nosov a ötandardnej odch˝lky. Metriky zaloûené na rámci strednej odch˝lky sa vynechávajú z dôvodu moûného skreslenia kvôli tomu, ûe v˝nosy stratégie kryt˝ch call opcií majú negatívne zoöikmenie. Klasifikace JEL G10, G11, G12, G13, C02 Klí ová slova Kryté call opcie, ETF, Blackov-Scholesov model, Oce ovanie opcií, V˝konnos port- fólia Název práce Vliv kryt˝ch call opcí na v˝konnost portfo- liaInstitute of Economic StudiesInstitut ekonomických studiíFaculty of Social SciencesFakulta sociálních vě

On the intrinsic bottom content of the nucleon and its impact on heavy new physics at the LHC

Heavy quark parton distribution functions (PDFs) play an important role in several Standard Model and New Physics processes. Most analyses rely on the assumption that the charm and bottom PDFs are generated perturbatively by gluon splitting and do not involve any non-perturbative degrees of freedom. It is clearly necessary to test this hypothesis with suitable QCD processes. Conversely, a non-perturbative, intrinsic heavy quark parton distribution has been predicted in the literature. We demonstrate that to a very good approximation the scale-evolution of the intrinsic heavy quark content of the nucleon is governed by non-singlet evolution equations. This allows us to analyze the intrinsic heavy quark distributions without having to resort to a full-fledged global analysis of parton distribution functions. We exploit this freedom to model intrinsic bottom distributions which are so far missing in the literature in order to estimate the impact of this non-perturbative contribution to the bottom-quark PDF, and on parton--parton luminosities at the LHC. This technique can be applied to the case of intrinsic charm, albeit within the limitations outlined in the following.Comment: 23 pages, 11 figure