Transverse-momentum resummation for boson plus jet production at hadron colliders

We consider the associated production of a vector or Higgs boson with a jet in hadronic collisions. When the transverse momentum $$q_T$$ q T of the boson-jet system is much smaller than its invariant mass Q, the QCD perturbative expansion is affected by large logarithmic terms that must be resummed to all orders. We discuss the all-order resummation structure of the logarithmically enhanced contributions up to next-to-leading logarithmic accuracy. Resummation is performed at the differential level with respect to the kinematical variables of the boson-jet system. Soft-parton radiation produces azimuthal correlations that are fully accounted for in our framework. We present explicit analytical results for the resummation coefficients up to next-to-leading order and next-to-leading logarithmic accuracy, that include the exact dependence on the jet radius.

Method for calculating the «mamsar+a» coupling with rope-core elements

Цель представленной статьи – ознакомление читателей с оригинальной методикой расчета канатностержневой муфты «MAMSAR+A». Методика расчета канатностержневой муфты рассматривается применительно к экспериментальному дизель-генераторному агрегату мощностью 9,56 кВт при частоте вращения 1500 мин-1с дизелем 2Ч8,5/11 и генератором «КГ-5,6». Расчетная рабочая длина канатных стержней 90 мм, диаметр каната 12 мм с шестью одинаковыми прядями. Максимальный угол закручивания канатностержневой муфты принят 30°. Задача состоит в выводе уточненной зависимости угла закручивания от величины крутящего момента на основе теоретических и экспериментальных исследований для определения количества канатных стержней при заданных значениях диаметра и длины канатного стержня. Оригинальность методики заключается: 1. Учитывая, что канатностержневая муфта «MAMSAR+A» содержит несколько канатных стержней, каждый из которых состоит из шести прядей, то зависимость угла закручивания от величины крутящего момента изначально рассчитывается для одной пряди. 2. Зависимость угла закручивания от величины крутящего момента пряди получена по известной формуле для цилиндрического торсиона и методом конечных элементов. Далее путем умножения результатов расчета на число прядей получены значения для одного центрального и трех канатных стержней. Оси последних расположены по диаметру окружности равномерно под углом 120°. 3. Зависимость угла закручивания от величины крутящего момента одного центрального и трех канатных стержней получена также экспериментально с использованием специально разработанных авторами устройств. 4. На основе теоретических и экспериментальных исследований получены поправочные коэффициенты, обеспечивающие возможность получения точной зависимости угла закручивания канатного стержня от величины крутящего момента, а из нее уже необходимое их количество для всей муфты. Данная методика применима также для расчета канатных муфт в том числе и для других диаметров каната. The purpose of this article is to familiarize readers with the original method of calculating the rope-rod coupling «MAMSAR+A». The method of calculating the rope-rod coupling is considered in relation to an experimental diesel generator unit with a power of 9.56 kW at a rotation speed of 1500 min-1 with a diesel 2H8,5/11 and a generator "KG-5.6". The estimated working length of the rope rods is 90 mm, the diameter of the rope is 12 mm with six identical strands. The maximum twisting angle of the rope-rod coupling is 30°. The task is to derive a refined dependence of the twisting angle on the torque value based on theoretical and experimental studies to determine the number of rope rods at specified values of the diameter and length of the rope rod. The originality of the method: 1. Considering that the «MAMSAR+A» rope-rod coupling contains several rope rods, each of which consists of six strands, the dependence of the twisting angle on the torque value is initially calculated for one strand. 2. The Dependence of the twist angle on the value of the torque of the strand is obtained by the well-known formula for the cylindrical torsion and the finite element method. Further, by multiplying the calculation results by the number of strands, the values for one Central and three rope rods are obtained. The axes of the latter are evenly spaced along the circumference of the circle at an angle of 120°. 3. The Dependence of the twisting angle on the torque value of one Central and three rope rods was also obtained experimentally using devices specially developed by the authors. 4. Based on theoretical and experimental studies, correction coefficients have been obtained that make it possible to obtain an exact dependence of the twisting angle of the rope rod on the torque value, and from it the necessary number of them for the entire coupling. This method is also applicable for calculating rope couplings, including for other rope diameters.

Top quark contribution to two-loop helicity amplitudes for Z boson pair production in gluon fusion

We compute the top quark contribution to the two-loop amplitude for on-shell Z boson pair production in gluon fusion, gg → ZZ. Exact dependence on the top quark mass is retained. For each phase space point the integral reduction is performed numerically and the master integrals are evaluated using the auxiliary mass flow method, allowing fast computation of the amplitude with very high precision.

Optical properties of atomically thin films of the topological insulator Bi2Se3

Problem formulating. To study the transport properties of atomically thin films of topological insulators, it is very important to determine their thickness as accurately as possible, as well as the state of the surface. Goal. To obtain atomically thin films of the topological insulator Bi2Se3 and to determine their thickness and the degree of surface degradation via their optical properties. Result. A technique that allows one to obtain single-crystal films of large area and various thicknesses on optically transparent substrates has been developed. The dependence of the transparency depending on the number of atomic layers (Bi2Se3 quintiples) in the film is determined. The obtained exact dependence of transparency on the number of layers is in good agreement with theory. It was also possible to observe how the transparency of the films changes over time, which is associated with the degradation of its surface layers. Practical meaning.The results obtained can be used for optical quality control of atomically thin films of quasi-twodimensional compounds, as well as for the manufacture of various micro- and nanostructures based on them, which can bring closer to the creation of a new element base for electronic devices.

Method for calculating the «mamsar+a» coupling with rope-core elements

Цель представленной статьи – ознакомление читателей с оригинальной методикой расчета канатностержневой муфты «MAMSAR+A». Методика расчета канатностержневой муфты рассматривается применительно к экспериментальному дизель-генераторному агрегату мощностью 9,56 кВт при частоте вращения 1500 мин-1с дизелем 2Ч8,5/11 и генератором «КГ-5,6». Расчетная рабочая длина канатных стержней 90 мм, диаметр каната 12 мм с шестью одинаковыми прядями. Максимальный угол закручивания канатностержневой муфты принят 30°. Задача состоит в выводе уточненной зависимости угла закручивания от величины крутящего момента на основе теоретических и экспериментальных исследований для определения количества канатных стержней при заданных значениях диаметра и длины канатного стержня. Оригинальность методики заключается: 1. Учитывая, что канатностержневая муфта «MAMSAR+A» содержит несколько канатных стержней, каждый из которых состоит из шести прядей, то зависимость угла закручивания от величины крутящего момента изначально рассчитывается для одной пряди. 2. Зависимость угла закручивания от величины крутящего момента пряди получена по известной формуле для цилиндрического торсиона и методом конечных элементов. Далее путем умножения результатов расчета на число прядей получены значения для одного центрального и трех канатных стержней. Оси последних расположены по диаметру окружности равномерно под углом 120°. 3. Зависимость угла закручивания от величины крутящего момента одного центрального и трех канатных стержней получена также экспериментально с использованием специально разработанных авторами устройств. 4. На основе теоретических и экспериментальных исследований получены поправочные коэффициенты, обеспечивающие возможность получения точной зависимости угла закручивания канатного стержня от величины крутящего момента, а из нее уже необходимое их количество для всей муфты. Данная методика применима также для расчета канатных муфт в том числе и для других диаметров каната. The purpose of this article is to familiarize readers with the original method of calculating the rope-rod coupling «MAMSAR+A». The method of calculating the rope-rod coupling is considered in relation to an experimental diesel generator unit with a power of 9.56 kW at a rotation speed of 1500 min-1 with a diesel 2H8,5/11 and a generator "KG-5.6". The estimated working length of the rope rods is 90 mm, the diameter of the rope is 12 mm with six identical strands. The maximum twisting angle of the rope-rod coupling is 30°. The task is to derive a refined dependence of the twisting angle on the torque value based on theoretical and experimental studies to determine the number of rope rods at specified values of the diameter and length of the rope rod. The originality of the method: 1. Considering that the «MAMSAR+A» rope-rod coupling contains several rope rods, each of which consists of six strands, the dependence of the twisting angle on the torque value is initially calculated for one strand. 2. The Dependence of the twist angle on the value of the torque of the strand is obtained by the well-known formula for the cylindrical torsion and the finite element method. Further, by multiplying the calculation results by the number of strands, the values for one Central and three rope rods are obtained. The axes of the latter are evenly spaced along the circumference of the circle at an angle of 120°. 3. The Dependence of the twisting angle on the torque value of one Central and three rope rods was also obtained experimentally using devices specially developed by the authors. 4. Based on theoretical and experimental studies, correction coefficients have been obtained that make it possible to obtain an exact dependence of the twisting angle of the rope rod on the torque value, and from it the necessary number of them for the entire coupling. This method is also applicable for calculating rope couplings, including for other rope diameters.

Forward–backward asymmetry in electron–positron annihilation into pion or kaon pairs revisited

Forward–backward (charge) asymmetry in the processes of [Formula: see text] annihilation into a pair of charged pseudoscalar mesons is recalculated in the one-loop approximation. The exact dependence on the meson masses is taken into account. Results known in the literature are partially corrected. The bulk of the charge asymmetry appears due to double-photon exchange in [Formula: see text] channel. Experimental studies of the asymmetry can be used to verify the point-like approximation used in calculation of radiative corrections due to emission of photons by pions or kaons.

The effect of the environment-dependent IMF on the formation and metallicities of stars over the cosmic history

Recent observational and theoretical studies indicate that the stellar initial mass function (IMF) varies systematically with the environment (star formation rate – SFR, metallicity). Although the exact dependence of the IMF on those properties is likely to change with improving observational constraints, the reported trend in the shape of the IMF appears robust. We present the first study aiming to evaluate the effect of the IMF variations on the measured cosmic SFR density (SFRD) as a function of metallicity and redshift, fSFR(Z, z). We also study the expected number and metallicity of white dwarf, neutron star, and black hole progenitors under different IMF assumptions. Applying the empirically driven IMF variations described by the integrated galactic IMF (IGIMF) theory, we revise fSFR(Z, z) obtained in our previous study that assumed a universal IMF. We find a lower SFRD at high redshifts and a higher fraction of metal-poor stars being formed than previously determined. In the local Universe, our calculation applying the IGIMF theory suggests more white dwarf and neutron star progenitors in comparison with the universal IMF scenario, while the number of black hole progenitors remains unaffected.