Cross Section Sigma Research Articles

Measuring lepton number violation in heavy neutral lepton decays at the future muon collider

The future muon collider has the potential to discover feebly interacting particles in a wide range of masses above the electroweak scale. It is particularly suitable to search for heavy neutral leptons (HNLs), as their production cross section σ∼mW−2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sigma \\sim {m}_W^{-2} $$\\end{document} is not suppressed by the new physics scale. We demonstrate that with the capacity to observe up to 105 events in the previously unexplored TeV mass range, the muon collider provides the means to measure the fraction of lepton number violating (LNV) processes with precision at the level of a percent. This capability enables elucidating the nature of HNLs, allowing us to differentiate between Majorana, Dirac, and non-minimal scenarios featuring multiple degenerate HNLs. We link the observed fraction of LNV processes to the parameters of the model with three degenerate HNLs, which could be responsible for generating baryon asymmetry in the Universe. Additionally, we present a simple estimate for the number of signal events, as well as analyze the feasibility of vector boson fusion processes in searches for HNLs.

Production of 180m\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{180\ extrm{m}}}$$\\end{document}Hf in photoproton reaction 181\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{181}}$$\\end{document}Ta(γ,p)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\gamma ,p)$$\\end{document} at energy Eγmax=35\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\\mathrm{\\gamma max}} = 35$$\\end{document}–95 MeV

The production of the 180mHf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{180\ extrm{m}}\ extrm{Hf}$$\\end{document} nuclei in the photoproton reaction 181Ta(γ,p)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{181}\ extrm{Ta}}(\\gamma ,p)$$\\end{document} was studied at end-point bremsstrahlung energies Eγmax=35\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\\mathrm{\\gamma max}}=35$$\\end{document}–95 MeV. The experiment was performed at the electron linear accelerator LUE-40 NSC KIPT with the use of the γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document} activation and off-line γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document}-ray spectroscopy. The experimental values of the bremsstrahlung flux-averaged cross-sections ⟨σ(Eγmax)⟩m\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\langle {\\sigma (E_{\\mathrm{\\gamma max}})}\\rangle _{\ extrm{m}}$$\\end{document} for the 181Ta(γ,p)180mHf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{181}\ extrm{Ta}}(\\gamma ,p)^{180\ extrm{m}}\ extrm{Hf}$$\\end{document} reaction were determined, and at Eγmax>55\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\\mathrm{\\gamma max}} > 55$$\\end{document} MeV obtained for the first time. The measured values, as well as the literature data, significantly (by more that an order of magnitude) exceed the theoretical flux-averaged cross-sections ⟨σ(Eγmax)⟩th\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\langle {\\sigma (E_{\\mathrm{\\gamma max}})}\\rangle _{\ extrm{th}}$$\\end{document}. The ⟨σ(Eγmax)⟩th\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\langle {\\sigma (E_{\\mathrm{\\gamma max}})}\\rangle _{\ extrm{th}}$$\\end{document} values were calculated using the cross-section σ(E)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma (E)$$\\end{document} computed with the TALYS1.95 code for six different level density models. A comparative analysis of the calculated total cross-sections from the TALYS computation for the reactions 181Ta(γ,p)180Hf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{181}\ extrm{Ta}}(\\gamma ,p)^{180}\ extrm{Hf}$$\\end{document} and 181Ta(γ,n)180Ta\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{181}\ extrm{Ta}}(\\gamma ,n)^{180}\ extrm{Ta}$$\\end{document} was performed. It was shown that the photoproton (γ,p)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\gamma ,p)$$\\end{document} to photoneutron (γ,n)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\gamma ,n)$$\\end{document} strength ratio is consistent with the estimates based on the isospin selection rules and the value from the (e,e′p)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(e,e'p)$$\\end{document} experiment.

Effects of exact kinematics and the Sudakov form factor on the dipole amplitude

We investigate the effects of exact gluon kinematics on the parameters of the Golec-Biernat–Wüsthoff, and Bartels–Golec-Biernat–Kowalski saturation models. The resulting fits show some differences, particularly, in the normalization of the dipole cross section σ0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma _0$$\\end{document}. The refitted models are used for the dijet production process in DIS to describe HERA data and investigate the effects of the Sudakov form factor at the future Electron Ion Collider.

Measurement of the total cross section and rho -parameter from elastic scattering in pp collisions at sqrt{s}=13 TeV with the ATLAS detector

In a special run of the LHC with beta ^{star } = 2.5 km, proton–proton elastic-scattering events were recorded at sqrt{s} = 13 TeV with an integrated luminosity of 340~upmu {text {b}}^{-1} using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from -t = 2.5 cdot 10^{-4} GeV^{2} to -t = 0.46 GeV^{2} using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section sigma _{text {tot}}, parameters of the nuclear slope, and the rho -parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit t rightarrow 0. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for sigma _{text {tot}} and rho are σtot(pp→X)=104.7±1.1mb,ρ=0.098±0.011.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} \\sigma _{\ ext {tot}}(pp\\rightarrow X) = 104.7 \\pm 1.1 \\; \ ext{ mb },\\quad \\rho = 0.098 \\pm 0.011 . \\end{aligned}$$\\end{document}The uncertainty in sigma _{text {tot}} is dominated by the luminosity measurement, and in rho by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.

Production of double heavy quarkonia at super Z factory

Within the color singlet model, we calculate the exclusive production of double charmonia, double bottomonia, and double B_c mesons at future super Z factory. The two heavy quarkonia or B_c’s are either two S-wave Fock states (^1S_0, ~^3S_1), or one S-wave and one P-wave states (^1P_1,~^3P_J~(J=0,1,2)). The top three Z^0 propagated channels in cross sections for double charmonia are sigma {(J/psi +h_c)}_{Z^0}=(454.0^{+39.1}_{-59.2})times 10^{-5} fb, sigma {(eta _c+chi _{c2})}_{Z^0}=(284.2^{+22.2}_{-35.3})times 10^{-5} fb, and sigma {(eta _c+chi _{c0})}_{Z^0}=(137.0^{+9.9}_{-16.4})times 10^{-5} fb. For double bottomonia, they are sigma {(eta _b+Upsilon )}_{Z^0}=(428.6^{+67.9}_{-60.9})times 10^{-4} fb, sigma {(Upsilon +chi _{b2})}_{Z^0}=(230.6^{+23.6}_{-22.2})times 10^{-4} fb, and sigma {(Upsilon +Upsilon )}_{Z^0}=(119.9^{+18.4}_{-16.6})times 10^{-4} fb. For double B_c mesons, they are sigma {(B_c^{*+}+B_c^{*-})}_{Z^0}=(1150^{+87}_{-84})times 10^{-3} fb, sigma {(B_c^{*+}+chi _{bc2}^-)}_{Z^0}=(1133^{-16}_{+22})times 10^{-3} fb, and sigma {(eta _{bc}^++B_c^{*-})}_{Z^0}=(634.6^{+47.8}_{-45.8})times 10^{-3} fb. Here the uncertainties come from the varying masses of constituent heavy quarks, which bring up to 20% corrections. The cross sections of double B_c mesons are roughly one order of magnitude larger than those of the double bottomonia, and two orders of magnitude larger than those of the double charmonia. To make it helpful for experimental study, we present the total cross sections sigma as functions of CM energy sqrt{s}, sigma as functions of the renormalization scale mu , the angle distributions dsigma /dcostheta , and the p_T distributions dsigma /dp_{t}. We also find that the initial state radiation can bring about 30–40% suppresions when 1%m_Z energy is losing, and cross sections can increase by about 2–3 times or decrease by an order of magnitude when adopting different potential models which becomes the major source of uncertainty. The numerical results show that it might be not optimistic for the experimental observation, but it is still far from excluded at the FCC-ee and also the CEPC running in the Z factory mode.

PNNPlus Saturation Logging Technology And Its Application

As oilfield enters middle and late stages of exploitation, the dynamic monitoring of oil saturation has become an essential part for grasping the distribution of remaining oil and improving the crude oil recovery. PNNPlus is a new saturation logging technology that adds two activated gamma probes on the basis of thermal neutron lifetime logging using neutron probes to assist in determining the water content of the reservoir, but its adaptability for residual oil saturation monitoring in low-porosity and low-permeability formation is unclear. Therefore, this paper researches and analyzes the adaptability of PNNPlus saturation logging technology by taking the Longdong Oilfield in the Ordos Basin as the research object. It is shown that: the PNNPlus logging technology is suitable for evaluating the remaining oil saturation of the mediumlow porosity reservoir in the Longdong Oilfield as the PNNPlus logging results are consistent with the oil saturation of completed wells and the interpretation conclusions can accurately evaluate the remaining oil saturation; The water saturation of the formation calculated by the oxygen content in the formation as detected by PNNPlus logging tool and the macro-capture cross-section Sigma, combined with the oil saturation, completion logging data, and geological data, can accurately identify and divide water-flooded layers; The formation porosity obtained from PNNPlus logging deviates from that obtained from completion logging by 0. 5%, but matches well with the oil saturation of the oil layer and water layer obtained from completion logging.

Interaction of Solar Neutrinos with {}^{98}mathrm{Mo} and {}^{100}mathrm{Mo} Nuclei

The process of neutrino interaction with {}^{98}mathrm{Mo} and {}^{100}mathrm{Mo} nuclei is studied with allowance for the effect of charge-exchange resonances. The results obtained by calculating the cross section for solar-neutrino capture by the isotopes {}^{98}Mo and {}^{100}Mo, sigma(E_{nu}), are presented. Use is made of both experimental data obtained for the strength functions S(E) in (p,n) and ({}^{3}He, t) charge-exchange reactions and the strength functions S(E) calculated within the theory of finite Fermi systems. The effect of the resonance structure of S(E) on the calculated cross sections for solar-neutrino capture is studied, and the contribution of each high-lying resonance to the capture cross section sigma(E_{nu}) is isolated. The contributions of all components of the solar neutrino spectrum are calculated. The contribution of background solar neutrinos to the double-beta decay of {}^{100}Mo nuclei is estimated.

The shear viscosity of parton matter under anisotropic scatterings

The shear viscosity eta of a quark–gluon plasma in equilibrium can be calculated analytically using multiple methods or numerically using the Green–Kubo relation. It has been realized, which we confirm here, that the Chapman–Enskog method agrees well with the Green–Kubo result for both isotropic and anisotropic two-body scatterings. We then apply the Chapman–Enskog method to study the shear viscosity of the parton matter from a multi-phase transport model. In particular, we study the parton matter in the center cell of central and midcentral Au + Au collisions at 200A GeV and Pb + Pb collisions at 2760A GeV, which is assumed to be a plasma in thermal equilibrium but partial chemical equilibrium. As a result of using a constant Debye mass or cross section sigma for parton scatterings, the eta /s ratio increases with time (as the effective temperature decreases), contrary to the trend preferred by Bayesian analysis of the experimental data or pQCD results that use temperature-dependent Debye masses. At sigma =3 mb that enables the transport model to approximately reproduce the elliptic flow data of the bulk matter, the average eta /s of the parton matter in partial equilibrium is found to be very small, between one to two times 1/(4pi ).

Adequacy of Effective Born for electroweak effects and TauSpinner algorithms for high energy physics simulated samples

Matching and comparing the measurements of past and future experiments call for consistency checks of electroweak (EW) calculations used for their interpretation. On the other hand, new calculation schemes of the field theory can be beneficial for precision, even if they may obscure comparisons with earlier results. Over the years, concepts of Improved Born, Effective Born, as well as of effective couplings, in particular of sin ^2theta _W^{{textit{eff}}} mixing angle for EW interactions, have evolved. In our discussion, we use four versions of DIZET EW library for phenomenology of practically all HEP accelerator experiments over the last 30 years. We rely on the codes published and archived with the KKMC Monte Carlo program for e^+e^- rightarrow f {bar{f}} n(gamma ) and available for the TauSpinner as well. TauSpinner re-weighs generated events for introduction of EW effects. To this end, DIZET is first invoked, and its results are stored in data file and later used. Documentation of TauSpinner upgrade, to version 2.1.0, and that of its new arrangement for semi-automated benchmark plots are provided. In our paper, focus is placed on the numerical results, on the different approximations introduced in Improved Born to obtain Effective Born, which is simpler for applications of strong or QED processes in pp or e^+e^- colliders. The tau lepton polarization P_{tau }, forward–backward asymmetry A_{{textit{FB}}} and parton-level total cross section sigma ^{{textit{tot}}} are used to monitor the size of EW effects and effective sin ^2theta _W^{{textit{eff}}} picture limitations for precision physics. Collected results include: (i) Effective Born approximations and sin ^2theta _W^{{textit{eff}}}, (ii) differences between versions of EW libraries and (iii) parametric uncertainties due to, for example, m_t or Delta alpha _h^{(5)}(s). These results can be considered as benchmarks and also allow to evaluate the adequacy of Effective Born with respect to Improved Born. Definitions are addressed too.

Toverline{t}toverline{t} signatures through the lens of color-octet scalars

We reinterpret two recent LHC searches for events containing four top quarks left(toverline{t}toverline{t}right) in the context of supersymmetric models with Dirac gauginos and color-octet scalars (sgluons). We explore whether sgluon contributions to the four-top production cross section sigma left( ppto toverline{t}toverline{t}right) can accommodate an excess of four-top events recently reported by the ATLAS collaboration. We also study constraints on these models from an ATLAS search for new phenomena with high jet multiplicity and significant missing transverse energy left({E}_{mathrm{T}}^{mathrm{miss}}right) sensitive to signals with four top quarks. We find that these two analyses provide complementary constraints, with the jets + {E}_{mathrm{T}}^{mathrm{miss}} search exceeding the four-top cross section measurement in sensitivity for sgluons heavier than about 800 GeV. We ultimately find that either a scalar or a pseudoscalar sgluon can currently fit the ATLAS excess in a range of reasonable benchmark scenarios, though a pseudoscalar in minimal Dirac gaugino models is ruled out. We finally offer sensitivity projections for these analyses at the HL-LHC, mapping the 5σ discovery potential in sgluon parameter space and computing exclusion limits at 95% CL in scenarios where no excess is found.

Fire behaviour and resistance of cold-formed steel beams with sigma cross-sections

PurposeSigma cross-section profiles are often chosen for their lightness and ability to support large spans, offering a favourable bending resistance. However, they are more susceptible to local, distortional and lateral-torsional buckling, as possible failure modes when compared to common I-sections and hollow cross-sections. However, the instability phenomena associated to these members are not completely understood in fire situation. Therefore, the purpose of this study is to analyse the behaviour of beams composed of cold-formed sigma sections at elevated temperatures.Design/methodology/approachThis study presents a numerical analysis, using advanced methods by applying the finite element software SAFIR. A numerical analysis of the behaviour of simply supported cold-formed sigma beams in the case of fire is presented considering different cross-section slenderness values, elevated temperatures, steel grades and bending moment diagrams. Comparisons are made between the obtained numerically ultimate bending capacities and the design bending resistances from Eurocode 3 Part 1–2 rules and its respective French National Annex (FN Annex).FindingsThe current design expressions revealed to be over conservative when compared with the obtained numerical results. It was possible to observe that the FN Annex is less conservative than the general prescriptions, the first having a better agreement with the numerical results.Originality/valueFollowing the previous comparisons, new fire design formulae are analysed. This new methodology, which introduces minimum changes in the existing formulae, provides at the same time safety and accuracy when compared to the numerical results, considering the occurrence of local, distortional and lateral-torsional buckling phenomena in these members at elevated temperatures.

Current--Voltage, Capacitance--Voltage--Temperature, and DLTS Studies of Ni|6H-SiC Schottky Diode

In this paper, we give a systematical description of Ni|6H-SiC Schottky diode by current--voltage I(V) characteristics at room temperature and capacitance--voltage C(V) characteristics at various frequencies (10-800 kHz) and various temperatures (77-350oK). The I(V) characteristics show a double-barrier phenomenon, which gives a low and high barrier height (phiLbn=0.91 eV, phiHbn=1.55 eV), with a difference of Deltaphibn=0.64 eV. Also, low ideality factor nL=1.94 and high ideality factor nH=1.22 are obtained. The C-V-T measurements show that the barrier height phibn decreases with decreasing of temperature and gives a temperature coefficient alpha=1.0·10-3 eV/K and phibn(T=0 K)=1.32 eV. Deep-level transient spectroscopy (DLTS) has been used to investigate deep levels in the Ni|6H-SiC Schottky diode. The traps signatures such as activation energies Ea=0.50±0.07 eV, capture cross-section sigma=1.8·10-20 cm2, and defect concentration NT=6.2·1013 cm-3 were calculated from Arrhenius plots. Keywords: si1licon carbide, Schottky diodes, I-V, C-V-T, deep-level transient spectroscopy (DLTS).

Structural behaviour of steel cold-formed sigma beams strengthened with bonded steel tapes

In the paper the effectiveness of strengthening of thin-walled, cold-formed sigma beams using glued steel tapes is investigated. Special attention is paid to the evaluation of the possibility of increase the load capacity with simultaneous limitation of beams displacements by appropriate location of steel tapes on the sigma cross-section. The study is based on laboratory tests and numerical analysis results. The laboratory test were conducted on eight simply supported, single-span beams made of Σ200x70x2 profile by “Blachy Pruszyński”. Two beams were reinforced with steel tape placed on the inside surface of the upper flange, two with steel tape glued on the inside surface of the web, two beams with reinforcement located on the inside surface of the bottom flange, and two beams were tested as reference beams without reinforcement. Steel tape with the width of 50 mm and thickness of 1.5 mm, made of steel S235 was used as the reinforcement and was glued to the beams with SikaDur®-30 adhesive. Precise strain measurement was made using electrofusion strain gauges and displacements measurement was performed using two lenses of Aramis software with combination with the Tritop machine. Numerical models of the considered beams were developed in the program Abaqus. Work completes the comparative analysis and conclusions.

Measurement of the tbar{t} production cross-section and lepton differential distributions in emu dilepton events from pp collisions at sqrt{s}=13,text {TeV} with the ATLAS detector

The inclusive top quark pair (tbar{t}) production cross-section sigma _{tbar{t}} has been measured in proton–proton collisions at sqrt{s}=13,text {TeV}, using 36.1 fb^{-1} of data collected in 2015–2016 by the ATLAS experiment at the LHC. Using events with an opposite-charge emu pair and b-tagged jets, the cross-section is measured to be: σtt¯=826.4±3.6(stat)±11.5(syst)±15.7(lumi)±1.9(beam)pb,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$\\begin{aligned} \\sigma _{t\\bar{t}} = 826.4 \\pm 3.6\\,\\mathrm {(stat)}\\ \\pm 11.5\\,\\mathrm {(syst)}\\ \\pm 15.7\\,\\mathrm {(lumi)}\\ \\pm 1.9\\,\\mathrm {(beam)}\\,\\mathrm {pb}, \\end{aligned}$$\\end{document}where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the LHC beam energy, giving a total uncertainty of 2.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. It is used to determine the top quark pole mass via the dependence of the predicted cross-section on m_t^{mathrm{pole}}, giving m_t^{mathrm{pole}}=173.1^{+2.0}_{-2.1},text {GeV}. It is also combined with measurements at sqrt{s}=7,text {TeV} and sqrt{s}=8,text {TeV} to derive ratios and double ratios of tbar{t} and Z cross-sections at different energies. The same event sample is used to measure absolute and normalised differential cross-sections as functions of single-lepton and dilepton kinematic variables, and the results are compared with predictions from various Monte Carlo event generators.

A search for the standard model Higgs boson decaying to charm quarks

A direct search for the standard model Higgs boson, H, produced in association with a vector boson, V (W or Z), and decaying to a charm quark pair is presented. The search uses a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment at the LHC in 2016, at a centre-of-mass energy of 13 TeV. The search is carried out in mutually exclusive channels targeting specific decays of the vector bosons: W → ℓν, Z → ℓℓ, and Z → νν, where ℓ is an electron or a muon. To fully exploit the topology of the H boson decay, two strategies are followed. In the first one, targeting lower vector boson transverse momentum, the H boson candidate is reconstructed via two resolved jets arising from the two charm quarks from the H boson decay. A second strategy identifies the case where the two charm quark jets from the H boson decay merge to form a single jet, which generally only occurs when the vector boson has higher transverse momentum. Both strategies make use of novel methods for charm jet identification, while jet substructure techniques are also exploited to suppress the background in the merged-jet topology. The two analyses are combined to yield a 95% confidence level observed (expected) upper limit on the cross section sigma left(mathrm{VH}right)mathrm{mathcal{B}}left(mathrm{H}to mathrm{c}overline{mathrm{c}}right) of 4.5 left({2.4}_{-0.7}^{+1.0}right) pb, corresponding to 70 (37) times the standard model prediction.

Heavy neutrino searches at future Z-factories

We analyze the capacity of future Z-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos N are considered to be produced via the process e^+e^-rightarrow Zrightarrow nu N and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections sigma (e^+e^-rightarrow nu Nrightarrow nu ell jj) given by the Z-factories with integrated luminosities of 0.1, 1 and 10 hbox {ab}^{-1} if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints.

Measurement of exclusive {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0}\xa0photoproduction in ultraperipheral pPb collisions at sqrt{smash [b]{s_{_{mathrm {NN}}}}} = 5.02,text {Te}text {V}

Exclusive {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0} photoproduction is measured for the first time in ultraperipheral pPb collisions at sqrt{smash [b]{s_{_{mathrm {NN}}}}} = 5.02,text {Te}text {V} with the CMS detector. The cross section sigma ({upgamma _{}^{}} mathrm{p}rightarrow {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0}mathrm{p}) is 11.0 pm 1.4,text {(stat)} pm 1.0,text {(syst)} mu b at langle W_{{upgamma _{}^{}} mathrm{p}}rangle = 92.6,text {Ge}text {V} for photon–proton centre-of-mass energies W_{{upgamma _{}^{}} mathrm{p}} between 29 and 213,text {Ge}text {V} . The differential cross section mathrm {d}sigma /mathrm {d}|t | is measured in the interval 0.025< |t | < 1,text {Ge}text {V} ^{2} as a function of W_{{upgamma _{}^{}} mathrm{p}}, where t is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section sigma ({upgamma _{}^{}} mathrm{p}rightarrow {{{uprho _{}^{}} _{}^{}}{{left( {770}right) }{}_{}^{}}} ^{0}mathrm{p}) has a power-law dependence on the photon–proton centre-of-mass, consistent with electron–proton collision measurements performed at HERA. The W_{{upgamma _{}^{}} mathrm{p}} dependence of the exponential slope of the differential cross section mathrm {d}sigma /mathrm {d}|t | is also measured.

Studies on gluon evolution and geometrical scaling in kinematic constrained unitarized BFKL equation: application to high-precision HERA DIS data

We suggest a modified form of a unitarized BFKL equation imposing the so-called kinematic constraint on the gluon evolution in multi-Regge kinematics. The underlying nonlinear effects on the gluon evolution are investigated by solving the unitarized BFKL equation analytically. We obtain an equation of the critical boundary between dilute and dense partonic system, following a new differential geometric approach and sketch a phenomenological insight on geometrical scaling. Later we illustrate the phenomenological implication of our solution for unintegrated gluon distribution f(x,k_T^2) towards exploring high precision HERA DIS data by theoretical prediction of proton structure functions (F_2 and F_L) as well as double differential reduced cross section (sigma _r). The validity of our theory in the low Q^2 transition region is established by studying virtual photon–proton cross section in light of HERA data.

Measurement of the {mathrm {t}overline{mathrm {t}}} production cross section, the top quark mass, and the strong coupling constant using dilepton events in pp collisions at sqrt{s}=13,text {Te}text {V}

A measurement of the top quark–antiquark pair production cross section sigma _{mathrm {t}overline{mathrm {t}}} in proton–proton collisions at a centre-of-mass energy of 13,text {Te}text {V} is presented. The data correspond to an integrated luminosity of 35.9{,text {fb}^{-1}} , recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events (mathrm {e}^{pm }mathrm {mu }^{{mp }}, mathrm {mu ^+}mathrm {mu ^-}, mathrm {e}^+mathrm {e}^-) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of m_mathrm {mathrm {t}} ^{mathrm {MC}} = 172.5 ,text {Ge}text {V} the fit yields a measured cross section sigma _{mathrm {t}overline{mathrm {t}}} = 803 pm 2 ,text {(stat)} pm 25 ,text {(syst)} pm 20 ,text {(lumi)} ,text {pb} , in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the powheg simulation is performed. The measured value of m_mathrm {mathrm {t}} ^{mathrm {MC}} = 172.33 pm 0.14 ,text {(stat)} ,^{+0.66}_{-0.72} ,text {(syst)} ,text {Ge}text {V} is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions.

On Problem of Torsional Characteristics of Thin-walled Steel Beams with Web Openings

The current trend in the design of steel structures leads, due to the saving of the material, to the frequent use of thin-walled cold formed steel sections. The thin-walled cold-formed steel profiles are often manufactured with web holes. In the design of such a thin-walled steel members with web openings arises a question of correct determination of the real crosssectional properties. This paper focuses on the problem of the real torsional characteristics determination, which are parameters needed for the design of members subjected to the bending with respect to lateral torsional buckling or for the design of the compressed members prone to torsional buckling or flexural torsional buckling. These torsional characteristics include St. Venant torsion constant and warping constant. In the forthcoming European Standard specifying the rules for the design of beams with holes, it is recommended to use the cross-sectional characteristics of the most weakened section of the member with web openings. This paper deals with the possibility of introduction of “substitute cross-section” whose cross-sectional characteristics are determined as the weighted average of the properties of full section and the most weakened section. The solution with substitute cross-section is validated by the series of tests focusing on the experimental verification of the both real torsional stiffness –- St. Venant torsion stiffness and warping torsion stiffness. Based on the results of test series with twisted beams freely supported in torsion, the St. Venant torsion constant is being derived, respectively from the results of the test series with twisted beams fixed in torsion (the warping is restrained at both beam ends), the warping constant is being derived. Both torsional characteristics are verified by tests executed on three different lengths (L=2.0m, L=3.0m and L=4.0m) of beams with sigma cross-section with large circular web openings.