Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Nausheen R. Shah I will show, via effective field theory (EFT) techniques, that obtaining an observationally consistent relic density while evading stringent direct detection limits and maintaining h125 phenomenology in an extended Higgs sector can be easily achieved. I will then map such an EFT to the low energy limit of the NMSSM with the Higgsinos integrated out. Both the singlino and the singlet-like CP-odd and even scalars in the NMSSM may play a relevant role in such a scenario, while being difficult to probe via conventional searches. The singlet sector of the general NMSSM can be mapped on to a 2HDM+S, and I will discuss prospects of probing this at the LHC using signatures such as mono-Higgs and mono-Z. This proceeding is mostly based on Refs. [S. Baum, M. Carena, N.R. Shah, C.E.M. Wagner, Higgs portals for thermal Dark Matter. EFT perspectives and the NMSSM, JHEP 04 (2018) 069. arXiv:1712.09873, doi: 10.1007/JHEP04(2018)069] and [S. Baum, N.R. Shah, Two Higgs Doublets and a Complex Singlet: Disentangling the Decay Topologies and Associated Phenomenology. arXiv:1808.02667].

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): F. Garufi, Virgo Collaboration We report on the results obtained by Advanced Virgo in the last joint run with LIGO, the observation of first GW source together with gamma, X satellites and astronomical observatories and the scientific outcomes of this revolutionary observation. Finally we report on the status and perspectives of the upgrades of Advanced Virgo.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Pietro Baratella, Alex Pomarol, Fabrizio Rompineve We argue that strongly-interacting theories at the TeV scale can naturally lead to a long period of supercooling in the early universe. We analyze the implications for the relic abundance of axions, dark matter and baryons.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): R. Bernabei, P. Belli, A. Bussolotti, F. Cappella, V. Caracciolo, R. Cerulli, C.J. Dai, A. d'Angelo, A. Di Marco, H.L. He, A. Incicchitti, X.H. Ma, A. Mattei, V. Merlo, F. Montecchia, X.D. Sheng, Z.P. Ye The first results obtained by the DAMA/LIBRA–phase2 experiment with the data collected deep underground at the Gran Sasso National Laboratory over 6 independent annual cycles (corresponding to a total exposure of 1.13 ton × yr) are presented. The DAMA/LIBRA–phase2 apparatus, about 250 kg highly radio-pure NaI(Tl), profits of a second generation high quantum efficiency photomultipliers and of new electronics; in the new configuration the software energy threshold is at 1 keV. The DAMA/LIBRA–phase2 data confirm the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature, at 9.5 σ C.L. in the energy region (1-6) keV. In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA–phase1 the achieved C.L. for the full exposure (2.46 ton × yr) is 12.9 σ.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Thomas Flacke Many Standard Model extensions which address the hierarchy problem contain Dirac-fermion partners of the top quark at the TeV scale. We discuss several classes of composite Higgs models with top partners which have underlying descriptions in terms of a fundamental gauge-fermion dynamics. All of these models contain additional BSM states which are pseudo-Nambu-Goldstone bosons and are thus likely to be lighter than the top partners. We first discuss constraints from direct production and decay of these new states at the LHC and show that they can be light without conflicting with current searches. The pNGBs couple to top partners and thus provide new decay channels for them. We identify the novel top partner decays which occur most commonly in underlying models, provide effective Lagrangians and benchmarks, and discuss opportunities for future searches.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Seung J. Lee Traditional searches for fermionic top partners have focused on particles that can be described by Breit-Wigner resonances. We consider a natural model framework called “continuum naturalness” in which the top partners and gauge partners responsible for cutting off the Higgs potential are not particles but rather continuum states with a generic spectral density.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Dave Sutherland We consider how the effect of Anderson localisation in a one-dimensional, disordered lattice can be applied to generate exponential hierarchies amongst the couplings of 4D field theories. This may have applications in the study of beyond the Standard Model physics; we give a proof-of-concept model for the generation of small neutrino masses.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): M. Destefanis, BESIII Collaboration Since 2009 the BESIII spectrometer, which operates at the IHEP of Beijing, China, collected the world largest data sample of J/ψ, ψ(2S) and ψ(3770). Its excellent performances allowed to access a wide physics program, which includes deep investigation of the Standard Model, spectroscopy studies of the charmonium states, and search for new physics. An overview of the main experimental innovations and of the latest performed investigations will be here discussed.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Lucia Masetti, ATLAS Collaboration A summary of results relevant for searches of phenomena beyond the Standard Model (SM) obtained by the ATLAS experiment at the LHC is presented. While all SM measurements can be considered as indirect searches, the focus will be set on direct searches and measurements interpreted as limits on phenomena beyond the SM. Prospects towards Run 3 and High Luminosity LHC are reported where available. Most results are based on an integrated luminosity of 36 fb−1 at a centre-of-mass energy of 13 TeV.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Farvah Mahmoudi We present an overview of direct and indirect constraints in the MSSM, in CP-conserving and CP-violating MSSM scenarios, with some emphasis on the importance of combining the constraints from different sectors, namely SUSY and Higgs direct searches at the LHC, flavour physics, dark matter detection and electric dipole moments.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Ciro Riccio, T2K Collaboration T2K (Tokai to Kamioka) is a long-baseline neutrino oscillation experiment designed to measure (anti)neutrino flavor oscillations using an off-axis (anti)neutrino beam. The most recent oscillation results, obtained with an exposure of 1.5(1.3)×1021 protons on target in neutrino (antineutrino) mode are reported. The 2σ confidence interval for the CP-violating phase, δCP, does not include the CP-conserving cases (δCP=0,π). The best-fit values of the other parameters are sin2θ23=0.536−0.046+0.031(sin2θ23=0.536−0.041+0.031) and Δm322/10−3=2.434−0.072+0.073eV2/c4 (Δm132/10−3=2.410−0.071+0.070eV2/c4) for normal (inverted) ordering.One of the largest systematic uncertainties in neutrino oscillation analysis comes from neutrino interaction uncertainty. The T2K Collaboration has a wide cross section measurements program and the most recent results are discussed.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Bibhushan Shakya We discuss interpretations of anomalies in semitauonic to light semileptonic B decay ratios, R(D(⁎)), in frameworks where new physics couples to a light right-handed neutrino. An EFT level discussion of all simplified models involving a right-handed neutrino that can give rise to the relevant decay channel is presented. We discuss in detail the phenomenology of these flavor anomalies-inspired light sterile neutrinos, which includes possibilities for displaced decays at colliders and direct searches, measurable dark radiation, and gamma ray signals.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Hideki Miyake, Belle II collaboration The Belle II experiment at the SuperKEKB energy-asymmetric e+e− collider is the second-generation B-factory experiment, which is successor to the former Belle experiment at the KEKB accelerator. The Belle II experiment is aiming to study new physics beyond the Standard Model with high precision measurements. The design luminosity of the SuperKEKB accelerator, is 8×1035cm−1s−1, 40 times greater than that of the KEKB accelerator and plans to collect an integrated luminosity of 50 ab−1. In 2018 April, the Belle II detector recorded the first collision events during phase 2 operation. In this contribution, we present some highlights from phase 2 operation and prospects for the early and future physics programs.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Marco Ciuchini, Antonio M. Coutinho, Marco Fedele, Enrico Franco, Ayan Paul, Luca Silvestrini, Mauro Valli We review the hadronic uncertainties involved in the decay B→K⁎ℓ+ℓ−, arguing that the non-factorizable hadronic contribution might account for some of the anomalies observed in b→s transitions, namely the ones relating to the P5′ observable. Moreover, we explore how alternative Beyond Standard Model interpretations of the anomalies pattern, e.g. involving New Physics effects in axial operators, become viable with a more conservative approach on the treatment of non-factorizable contributions.

Abstract: Publication date: October–December 2018Source: Nuclear and Particle Physics Proceedings, Volumes 303–305Author(s): Tobias Hurth, Alexandre Arbey, Farvah Mahmoudi, Siavash Neshatpour The LHCb experiment has made several measurements in b→s transitions which indicate tensions with the Standard Model predictions. Assuming the source of these tensions to be new physics, we present new global fits to all Wilson coefficients which can effectively receive beyond the Standard Model contributions. While the theoretically clean ratios RK(⁎) which are sensitive to lepton flavour non-universality may unambiguously establish lepton non-universal new physics in the near future, most of the other tensions with the SM in the b→s data, in particular in the angular observables of the B→K⁎μμ decays and in the branching ratios of the Bs→ϕμμ decays, depend on the estimates of non-factorisable power corrections. Therefore, we also analyze the dependence of the new global fit on these corrections.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): P.G. Mitkin, G. Prokhorov, O.V. Teryaev, V.I. Zakharov For a number of reasons, theory of chiral effects in an external gravitational field has become actual recently. First, one can utilize a well known analogy between flows of fluid along gradient of temperature and along acceleration due to an external gravitational field. Using this analogy one can approach theory of thermal chiral effects. Another motivation to include external gravitational fleld comes from the phenomenology of heavy-ion collisions which indicates that the initial state can be considered as a rotated and accelerated medium. We concentrate mostly on two issues. First, existence of extra conservation laws in case of ideal fluid and its manifestation in chiral effects in gravitational field. Second, we review briefly introduction of the notion of imagnary acceleration and its relation to anomalies.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): E. Megías, E. Ruiz Arriola, L.L. Salcedo We study the equation of state, fluctuations and static correlators of electric charge, baryon number and strangeness, by considering a realization of the Hadron Resonance Gas model in the light flavor sector of QCD. We emphasize the importance of these observables to study, within this approach, the possible existence of exotic and missing states in the hadron spectrum. Some preliminary results for the baryon spectrum have been obtained within a relativistic quark-diquark model, leading to an overall good agreement with the spectrum obtained with other quark models. Finally, it is conjectured, within the Hadron Resonance Gas approach, the existence of a singularity in the correlators at zero temperature, which turns out to be analogous to the divergence of the partition function at the Hagedorn temperature.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Bianca Scavino, Belle II collaborations Belle II is a next generation B-factory experiment at the SuperKEKB collider. In early 2019 the fully operational detector will start taking data. The goal is to collect an integrated luminosity of 50 ab-1, a statistics 50 times larger than the one collected by its predecessor Belle. Belle II offers the most promising prospects for bottomonium physics in the next decade, since experimentally only high-luminosity e+e- colliders can collect enough statistics to fully exploit the potential of this sector.The current status of the experiment will be presented, together with the perspectives for studies of conventional and exotic quarkonium-like states.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Ina Carli, ATLAS Collaboration The measurements of production and properties of heavy flavoured hadrons can be used to probe our understanding of quantum chromodynamics and to search for physics beyond the Standard Model.This paper summarises three recent results from the ATLAS experiment at the Large Hadron Collider. It includes search for an exotic state X(5568) in the Bs0π± final state, measurement of quarkonia production in pPb and pp collisions and angular analysis of the rare decay B0→K⁎μ+μ−.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Michele Atzeni, LHCb collaboration The universality of the electroweak boson couplings to the different lepton flavours is a fundamental property of the Standard Model that is expected to be violated in a variety of new physics scenarios. A review of recent results obtained by the LHCb collaboration in semileptonic decays involving both charged and neutral currents is presented. The measurements were performed with the full data sample collected during the LHC Run 1, corresponding to an integrated luminosity of 3.0 fb−1 of proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. An overview of the ongoing and future measurements is also given.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): T.N. Pham Like the two-photon and two-gluon decays of the P-wave charmonium state for which the Born term produces a very simple decays amplitude, the Born term for the processes cd‾→(π,K)ℓν and bd‾→(π,K)ℓν, could also produce a simple expression for D and B meson semileptonic decays with a light meson π, K in the final state. The pole term at q2=mB2+mπ2 for B → π and at q2=mD2+mK2 for D → K form factor, are generated by the Born term and given as: f+(0)/(1−q2/(mH2+mπ2)), with H = D, B for D, B → π form factors, and f+(0)/(1−q2/(mH2+mK2)) for B, D → K form factor. These pole dominance terms describe rather well the q2-behavior of the form factors observed in the BaBar, Belle and BESIII measurements and in lattice simulation. In particular, the D → K form factors are in good agreement with the measured values in the whole range of q2 showing evidence for S U(3) breaking with the presence of the mK2 term in the quark propagator, but some corrections to the Born term are needed at large q2 for D, B → π form factors.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Hector Gisbert, Antonio Pich A recent lattice evaluation of ε′/ε, finding a 2.1 σ deviation from the experimental value, has revived the old debate about a possible ε′/ε anomaly. The unfounded claims of a too low Standard Model prediction are based on incorrect estimates that neglect the long-distance re-scattering of the final pions in K → 2π. In view of the current situation, we have recently updated the Standard Model calculation, including all known short- and long-distance contributions. Our result, Re(ε′/ε)=(15±7)⋅10−4 [H. Gisbert and A. Pich, “Direct CP violation in K0→ππ: Standard Model Status”, Rept. Prog. Phys. 81 (2018) no. 7, 076201 arXiv:1712.06147 [hep-ph].], is in complete agreement with the experimental measurement.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Antonio Rodríguez-Sánchez, Antonio Pich In the chiral limit, the D = 6 contribution to the Operator Product Expansion (OPE) of the VV −AA correlator of quark currents only depends on two vacuum condensates, which can be related to hadronic matrix elements associated to CP violation in non-leptonic kaon decays. We use those relations to determine 〈(ππ)I=2 Q8 K〉, using the updated ALEPH spectral functions. Alternatively, we use those relations in the opposite direction. Taking the values of the matrix elements from the lattice to obtain the D = 6 vacuum elements provides a new short-distance constraint which allows for an inclusive determination of fπ and an updated value for the D = 8 condensate.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Giuseppina Anzivino, G. Anzivino, R. Arcidiacono, W. Baldini, S. Balev, J.R. Batley, M. Behler, S. Bifani, C. Biino, A. Bizzeti, B. Bloch-Devaux, G. Bocquet, N. Cabibbo, M. Calvetti, N. Cartiglia, A. Ceccucci, E. Celeghini, P. Cenci, C. Cerri, C. Cheshkov The NA48/2 experiment collected data in 2003 and 2004 with the main purpose to study direct CP violation in charged kaons decaying in three pions. Thanks to the huge statistics collected, other studies are also possible. In this paper two recent results, in the framework of QCD studies, are reported: the measurement of the K± → π0e±ν Form Factors and the first observation of the rare decay K± → π±π0e+e−.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Akira Watanabe, Takahiro Sawada, Chung Wen Kao We present our analysis on the valence quark distribution functions of the K+ meson, νK(u)(x,Q2) and νK(s‾)(x,Q2), taking into account the meson cloud effects in the framework of the chiral constituent quark model. Assuming appropriate bare quark distribution functions at the initial scale, evaluating the Goldstone boson dressing corrections with the model, and performing the QCD evolution, one can obtain the realistic dressed distributions at a certain scale. The phenomenologically satisfactory valence quark distribution of the pion was obtained in the previous study and there are available experimental data of the valence u quark distribution ratio νK(u)(x,Q2)/νπ(u)(x,Q2), which enable us to obtain the kaon quark distribution functions. Besides presenting the resulting dressed distributions, we also show how the meson cloud effects affect the bare distributions in detail. A striking result is that the observed size of the SU(3) flavor symmetry breaking is considerably smaller than those seen in the preceding works based on other approaches.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Ugo Gastaldi For a long time doubts have existed on the existence of the f0(1370) meson as an individual object distinct and separated from the σ meson. Decays into π+π− of the f0(1370) are the main source of an isolated structure localized between 1.2 and 1.5 GeV in the π+π− mass spectrum measured in pp Central Exclusive Production (CEP) at s=200GeV at very low four momentum transfer squared ltl. These data confirm in the π+π− decay channel the existence of the f0(1370) as an isolated well identified structure that was previously observed in K+K−, KsKs, 4π0, 2π0π+π− and π+π−π+π− decays measured in pbar annihilations at rest. The decay branching ratios of f0(1370) into σσ, ρρ, ππ, KKbar, ηη relative to ππ decays obtained in analysis of data of pbar annihilations at rest which treat separately f0(1370) and σ are respectively 5.6, 3, 1, 1, 0.02. The decay and production properties of f0(1370) point to a large gg content. CEP interactions at very high energies favour production of 0++ and 2++ mesons. Selection of events with low ltl at both proton vertices suppresses 2++ structures. LHC runs dedicated to pp CEP measurements...

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Lukas Varnhorst, Budapest-Marseille-Wuppertal collaboration Nucleon sigma terms are fundamental properties of the nucleons and are important input quantities for direct dark matter detection experiments. Here we present a determination of these sigma terms directly from the underlying theory. We use the lattice formulation of QCD to non-perturbativley calculate the quark mass dependence of the nucleon mass and the Feynman-Hellmann theorem to deduce the sigma terms. We present results for the up, down, and strange sigma terms of the proton and neutron.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): A. Matyja, ALICE Collaboration The LHC provided pp collisions in the energy range s=0.9to13TeV, p-Pb collisions at sNN=5.02and8TeV, as well as Pb-Pb collisions at sNN=2.76and5.02TeV. Neutral meson production spectra and their ratios η/π0 as well as photon double ratio Rγ and direct photon spectra have been measured in a wide pT range at mid-rapidity by the ALICE experiment. Photons are registered in ALICE electromagnetic calorimeters, EMCal and PHOS or reconstructed from e+e− pairs when photons converted in the material of the inner barrel detectors (TPC and ITS). The π0 and η mesons are reconstructed via invariant mass technique with several complementary methods. The overview of the recent results from ALICE on the photon and meson production is presented.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Andrii Verbytskyi, Andrea Banfi, Adam Kardos, Pier Francesco Monni, Stefan Kluth, Gábor Somogyi, Zoltán Szőr, Zoltán Trocsányi, Zoltán Tulipánt, Giulia Zanderighi We present a comparison of the computation of energy-energy correlations and Durham algorithm jet rates in e+e− collisions at next-to-next-to-leading logarithmic accuracy matched with the next-to-next-to-leading order perturbative prediction to LEP, PEP, PETRA, SLC and TRISTAN data. With these predictions we perform global extractions of the strong coupling constant taking into account non-perturbative effects modelled with modern Monte Carlo event generators that simulate NLO QCD corrections.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Sergey Sukhoruchkin This review is devoted to the analysis of empirical data within the symmetry motivated electron-based approach to the Standard Model. It contains a continuation of investigations of the use of empirical correlations in particle masses and nuclear data (excitation energies and binding energies) for obtaining an additional fundamental information on parameters of the Standard Model. We consider here unexpectedly accurate empirical relations between nucleon masses and the electron rest mass (CODATA relations), the QCD based quark-gluon dressing effect (generation of the pion parameters and the constituent quark masses) and a role of QED radiative correction due to the influence of the physical condensate. Relations between masses of constituent quarks and masses of fundamental fields as well as the role of nuclear parameters connected with the one-meson exchange dynamics are discussed.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): M.T. Grippo, CMS collaboration Description of a broad range of analyses about additional Higgs bosons in the contest of Beyond Standard Model (BSM) physics performed at the CMS experiment at LHC.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Junquan Tao, CMS Collaboration Results of the measurements of the 125 GeV Higgs boson properties with proton-proton collision data at s=13TeV collected by CMS detector are presented. The used Higgs boson decay channels include the five major decay modes, H→γγ, H→ZZ→4ℓ, H→WW→ℓνℓν, H→τ+τ− and H→bb‾, and two rare decay modes, H→μ+μ− and H→Z/γ⁎+γ→ℓℓγ, with ℓ=e,μ. The measured Higgs boson properties include its mass, signal strength relative to the standard model prediction, signal strength modifiers for different Higgs boson production modes, coupling modifiers to fermions and bosons, effective coupling modifiers to photons and gluons, simplified template cross sections, fiducial cross sections. All results are consistent, within their uncertainties, with the expectations for the Standard Model Higgs boson.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Akanksha Vishwakarma, ATLAS Collaboration Measurements of the inclusive and differential cross-sections for top quark pair and single top production cross-sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider (LHC) are presented at centre-of-mass energies of 8 TeV and 13 TeV. These measurements reach high precision and are compared to the best available theoretical calculations. The differential measurements, including results using boosted topology, probe our understanding of top quark pair production in the TeV regime. Measurements of top-quark pair with additional jets enable the study of effect of gluon radiation, especially the measurement with additional heavy flavour jets provides test of multi-scale QCD calculation. The first evidence of single top quark production in the s-channel is quoted. Interference of top quark pair and single top productions is investigated, and the single top production cross-section in association with a Z boson is measured. Measurements of the properties of the Wtb vertex in single top quark production allow to set limits on anomalous couplings.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): T. Dado, ATLAS Collaboration The top quark plays a unique role among other known quarks as it decays before it forms hadronic bound states. Thus, studying its properties provides an interesting opportunity to access properties of a bare quark directly. The latest measurements of these properties with the ATLAS detector [ATLAS Collaboration, JINST 3, S08003 (2008)] at the LHC are presented. Measurements sensitive to the Wtb vertex are summarized and compared to the best theoretical calculations. Effects of colour reconnection on the jet variables in top quark events are presented. Limits on the flavour-changing neutral currents are discussed. The latest top quark decay width and mass measurements are reported.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): A.B. Shokouhi, A. Vafaee In this article, we present a Next-to-Leading Order (NLO) QCD analysis to determine of Parton Distribution Functions (PDFs) and the strong coupling αs(MZ2) based on four different, Thorne-Roberts (TR or RT), Thorne-Roberts Fast (RT FAST), Thorne-Roberts Optimal (RTOPT) and Thorne-Roberts Optimal Fast (RTOPT FAST) heavy-quark schemes and compare the central values of PDFs, fit quality and numerical values of the strong coupling with each other. We show the best fit quality is corresponding to RTOPT FAST heavy-quark scheme with χTotal2/dof=1.077 and the best improvement in the uncertainty of the strong coupling is corresponding again to RTOPT FAST scheme with αs(MZ2)=0.1184±0.0030.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): A. Vafaee This Next-to-Leading Order (NLO) Quantum Chromo Dynamics (QCD) analysis attempts to investigate the impact of LHCb charm and beauty production data in pp collisions at s=7TeV on the Parton Distribution Functions (PDFs) extracted from H1 and ZEUS collaboration data sets. We show adding the LHCb charm and beauty production data on the H1 and ZEUS combined data sets reduces the uncertainty bands of partonic distributions and improve the relative fit-quality up to 4.0 %.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): R.L. Pearson, C. Voisey An important limitation in current fits of parton distribution functions (PDFs) is that PDF uncertainties do not include any source of theoretical uncertainty. Here we present a general method for incorporating theoretical uncertainties into PDF fits, focussing in particular on perturbative missing higher order uncertainties (MHOUs). We consider two methods for estimating the effect of MHOUs on PDFs, both based on scale variations. Firstly, we present PDF fits based on theoretical predictions with varied scales, and use these to estimate the associated MHOUs. Secondly, we discuss the construction of a theoretical covariance matrix using scale variations, and its combination with the experimental covariance matrix currently used in PDF fits.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): F. Giuli, ATLAS Collaboration High-precision measurements of Standard Model (SM) processes provide information on different aspects contributing to the process, such as parton distribution functions (PDFs), and comparisons with the current precision reached theoretically on the calculations of the cross sections of such processes. This document describes ATLAS measurements, performed at different centre-of-mass energies, of vector boson (W and Z) cross sections and cross-section ratios. It also discusses measurements of ratios of Z-boson and top-quark pair production cross sections, which provide important information on the proton PDFs. Finally, a measurement involving the di-lepton decay channel of top-quark pairs at 8 TeV is presented, because of its direct sensitivity to the gluon PDF.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Metin Yalvac, Kadir Ocalan, CMS Collobration The production cross section of highly boosted vector bosons (V = W, Z or γ) recoiling against jets is studied, with CMS data, differentially as function of the transverse momentum and angular correlations of the final state particles. The measurements are confronted with different state-of-the-art theory predictions that include next-to-leading order calculations and matrix-element plus parton shower event simulations.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): Fernando Barreiro, ATLAS Collaboration ATLAS recent results obtained at the LHC on inclusive jet and dijet production at s=13TeV, on transverse energy-energy correlations and on azimuthal decorrelations at s=8TeV are discussed. The latter two are used to determine the strong coupling constant and to probe its running up to scales of order 2 TeV.

Abstract: Publication date: July–September 2018Source: Nuclear and Particle Physics Proceedings, Volumes 300–302Author(s): V. Mariani, CMS Collaboration We present recent results on minimum bias collisions, underlying event activity and double parton scattering using data recorded by the CMS detector at the LHC. The results on the measurement of the underlying event (UE) using leading tracks, jets, and Drell-Yan processes are presented. Double parton scattering is investigated in several final states including vector bosons, and the results are compared to other experiments and to multi parton interaction (MPI) models tuned to recent underlying event measurements at CMS.