569 research outputs found

    Фольклорные произведения в зеркале современной литературы: необходимость изучения в иностранной аудитории

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    The necessity of learning and the difficulties of comprehension and understanding of the folklore works for foreign students are examined in the article. Folklore works of literature should have a comparative character and the character of linguistic area studies. The connection between folklore texts and modern Russian writers’ works is displayed.В статье речь идет о необходимости изучения и трудностях восприятия и понимания произведений фольклора в иностранной аудитории. Обращается внимание на то, что работа с фольклорными произведениями должна носить сопоставительно-лингвострановедческий характер. Показана связь фольклорных текстов с произведениями современных русских писателей

    Berry Curvature in Graphene: A New Approach

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    In the present paper we have directly computed the Berry curvature terms relevant for Graphene in the presence of an \textit{inhomogeneous} lattice distortion. We have employed the generalized Foldy Wouthuysen framework, developed by some of us \cite{ber0,ber1,ber2}. We show that a non-constant lattice distortion leads to a valley-orbit coupling which is responsible to a valley-Hall effect. This is similar to the valley-Hall effect induced by an electric field proposed in \cite{niu2} and is the analogue of the spin-Hall effect in semiconductors \cite{MURAKAMI, SINOVA}. Our general expressions for Berry curvature, for the special case of homogeneous distortion, reduce to the previously obtained results \cite{niu2}. We also discuss the Berry phase in the quantization of cyclotron motion.Comment: Slightly modified version, to appear in EPJ

    The CDF dijet excess from intrinsic quarks

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    The CDF collaboration reported an excess in the production of two jets in association with a WW. We discuss constraints on possible new particle state interpretations of this excess. The fact of no statistically significant deviation from the SM expectation for {ZZ+dijet} events in CDF data disfavors the new particle explanation. We show that the nucleon intrinsic strange quarks provide an important contribution to the WW boson production in association with a single top quark production. Such {WW+t} single top quark production can contribute to the CDF {WW+dijet} excess, thus the nucleon intrinsic quarks can provide a possible explanation to the CDF excess in {WW+dijet} but not in {ZZ+dijet} events.Comment: 4 latex pages, 1 figure. Version for journal publicatio

    B_c meson rare decays in the light-cone quark model

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    We investigate the rare decays BcDs(1968)ˉB_c \rightarrow D_s(1968) \ell \bar{\ell} and BcDs(2317)ˉB_c\rightarrow D_s^*(2317) \ell \bar{\ell} in the framework of the light-cone quark model (LCQM). The transition form factors are calculated in the space-like region and then analytically continued to the time-like region via exponential parametrization. The branching ratios and longitudinal lepton polarization asymmetries (LPAs) for the two decays are given and compared with each other. The results are helpful to investigating the structure of BcB_c meson and to testing the unitarity of CKM quark mixing matrix. All these results can be tested in the future experiments at the LHC.Comment: 9 pages, 11 figures, version accepted for publication in EPJ

    Pion-photon and photon-pion transition form factors in light-cone formalism

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    We derive the minimal Fock-state expansions of the pion and the photon wave functions in light-cone formalism, then we calculate the pion-photon and the photon-pion transition form factors of γπ0γ\gamma ^{\ast}\pi ^{0}\to \gamma and γγπ0\gamma ^{\ast}\gamma \to \pi ^{0} processes by employing these quark-antiquark wave functions of the pion and the photon. We find that our calculation for the γγπ0\gamma ^{\ast}\gamma \to \pi ^{0} transition form factor agrees with the experimental data at low and moderately high energy scale. Moreover, the physical differences and inherent connections between the transition form factors of γπ0γ\gamma ^{\ast}\pi ^{0}\to \gamma and γγπ0 \gamma ^{\ast}\gamma \to \pi ^{0} have been illustrated, which indicate that these two physical processes are intrinsically related. In addition, we also discuss the π0γγ\pi ^{0}\to \gamma \gamma form factor and the decay width Γ(πγγ) \mathit{\Gamma}(\pi \to \gamma \gamma) at Q2=0Q^{2}=0.Comment: 20 pages, 2 figure

    Restoration of kTk_T factorization for low pTp_T hadron hadroproduction

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    We discuss the applicability of the kTk_T factorization theorem to low-pTp_T hadron production in hadron-hadron collision in a simple toy model, which involves only scalar particles and gluons. It has been shown that the kTk_T factorization for high-pTp_T hadron hadroproduction is broken by soft gluons in the Glauber region, which are exchanged among a transverse-momentum-dependent (TMD) parton density and other subprocesses of the collision. We explain that the contour of a loop momentum can be deformed away from the Glauber region at low pTp_T, so the above residual infrared divergence is factorized by means of the standard eikonal approximation. The kTk_T factorization is then restored in the sense that a TMD parton density maintains its universality. Because the resultant Glauber factor is independent of hadron flavors, experimental constraints on its behavior are possible. The kTk_T factorization can also be restored for the transverse single-spin asymmetry in hadron-hadron collision at low pTp_T in a similar way, with the residual infrared divergence being factorized into the same Glauber factor.Comment: 12 pages, 2 figures, version to appear in EPJ

    Branching ratio and CP asymmetry of Bsπ+πB_s \to \pi^+ \pi^- decays in the perturbative QCD approach

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    In this paper, we calculate the decay rate and CP asymmetry of the Bsπ+πB_s \to \pi^+\pi^- decay in perturbative QCD approach with Sudakov resummation. Since none of the quarks in final states is the same as those of the initial BsB_s meson, this decay can occur only via annihilation diagrams in the standard model. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. We find that (a) the branching ratio is about 4×1074 \times 10^{-7}; (b) the penguin diagrams dominate the total contribution; and (c) the direct CP asymmetry is small in size: no more than 33% ; but the mixing-induced CP asymmetry can be as large as ten percent testable in the near future LHC-b experiments.Comment: 12 pages, 4 figures included, RevTe

    Forward Jets and Energy Flow in Hadronic Collisions

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    We observe that at the Large Hadron Collider, using forward + central detectors, it becomes possible for the first time to carry out calorimetric measurements of the transverse energy flow due to "minijets" accompanying production of two jets separated by a large rapidity interval. We present parton-shower calculations of energy flow observables in a high-energy factorized Monte Carlo framework, designed to take into account QCD logarithmic corrections both in the large rapidity interval and in the hard transverse momentum. Considering events with a forward and a central jet, we examine the energy flow in the interjet region and in the region away from the jets. We discuss the role of these observables to analyze multiple parton collision effects.Comment: 9 pages, 5 figures. Version2: added results on azimuthal distributions and more discussion of energy flow definition using jet clusterin

    Tri-meson-mixing of π\pi-η\eta-η\eta' and ρ\rho-ω\omega-ϕ\phi in the light-cone quark model

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    The radiative transition form factors of the pseudoscalar mesons {π\pi, η\eta, η\eta'} and the vector mesons {ρ\rho, ω\omega, ϕ\phi} are restudied with π\pi-η\eta-η\eta' and ρ\rho-ω\omega-ϕ\phi in tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson-mixing than previous results in a two-mixing-angle scenario of only two-meson η\eta-η\eta' mixing and ω\omega-ϕ\phi mixing.Comment: 8 pages, 6 figures, final version to appear in EPJ
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