Results 1 - 10 of 1405
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[en] We analyze the known results for the eigenvalue of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation in the perturbative regime using the analytic continuation of harmonic sums from even positive arguments to the complex plane. The resulting meromorphic functions have poles at negative integer values of the argument. The typical classification of harmonic sums is determined by two major parameters: a) the weight - a sum of inverse powers of the summation indices; b) the depth - a number of nested summations. We introduce the third parameter: the alternation - a number of nested sign-alternating summations in a given harmonic sum. We claim that the maximal alternation of the nested summation in the functions building the BFKL eigenvalue is preserved from loop to loop in the perturbative expansion. The BFKL equation is formulated for arbitrary color configuration of the propagating states in the t-channel. Based on known results one can state that color adjoint BFKL eigenvalue can be written using only harmonic sums with positive indices, maximal alternation zero, and at most depth one, whereas the singlet BFKL eigenvalue is constructed of harmonic sums with maximal sign alternation being equal one. We also note that for maximal alternation being equal unity the harmonic sums can be expressed through alternation zero harmonic sums with half-shifted arguments.
[en] We present preliminary results of the exclusive electroproduction of ρ+ on the proton at CLAS. We discuss the interpretation of the cross sections in terms of t-channel Reggeon exchanges and in terms of Generalized Parton Distributions (GPDs) formalism.
[en] We show that the deviation from exponential behavior of the diffraction cone observed near t = −0.1 GeV"2 both at the ISR and at the LHC (the so-called break) follows from a two-pion loop in the t-channel, imposed by unitarity. By using a simple Regge-pole model we extrapolate the 'break' from the ISR energy region to that of the LHC.
[en] Solution of Bethe-Salpeter equation was obtained in t-channel for four-gluon operators in the Regge-logarithmic approximation of quantum chromodynamic theory of perturbation. Used for solving method brings to effective theory, similar to (Regge) field theory
[en] The transverse momentum spectra of hadrons produced in high energy collisions can be decomposed into two components: the exponential ("thermal") and the power ("hard") ones. Recently, the H1 Collaboration has discovered that the relative strength of these two components in Deep Inelastic Scattering (DIS) depends drastically upon the global structure of the event — namely, the exponential component is absent in the diffractive events characterized by a rapidity gap. We discuss the possible origin of this effect and speculate that it is linked to confinement. Specifically, we argue that the thermal component is due to the effective event horizon introduced by the confining string, in analogy to the Hawking–Unruh effect. In diffractive events, the t-channel exchange is color-singlet and there is no fragmenting string — so the thermal component is absent. The slope of the soft component of the hadron spectrum in this picture is determined by the saturation momentum that drives the deceleration in the color field, and thus the Hawking–Unruh temperature. We analyze the data on nondiffractive pp collisions and find that the slope of the thermal component of the hadron spectrum is indeed proportional to the saturation momentum. (author)
[en] A separation of the two-Reggeon-cut contribution into different s-channel-discontinuity components using a t-channel approach is suggested and compared with the Reggeon-cutting rules obtained from a s-channel approach. The separation agrees with the Abramovskii--Gribov--Kancheli cutting rules and suggests that these rules are model independent
[en] We develop the mathematical apparatus necessary to isolate pure naturality contributions from the helicity amplitudes for an arbitrary 2 → 2 scattering process (with a Bosonic t channel). We prove that certain combinations of the amplitudes and their (multiple) energy-derivatives suffice, and that no simpler methods exist. For high spin processes, where our methods might be overcomplicated, we develop a simple and accurate approximation using just a single energy-derivative
[en] The use of simplified models as a tool for interpreting dark matter collider searches has become increasingly prevalent, and while early Run II results are beginning to appear, we look to see what further information can be extracted from the Run I dataset. We consider three ‘standard’ simplified models that couple quarks to fermionic singlet dark matter: an s-channel vector mediator with vector or axial-vector couplings, and a t-channel scalar mediator. Upper limits on the couplings are calculated and compared across three alternate channels, namely mono-jet, mono-Z (leptonic) and mono-W/Z (hadronic). The strongest limits are observed in the mono-jet channel, however the computational simplicity and absence of significant t-channel model width effects in the mono-boson channels make these a straightforward and competitive alternative. We also include a comparison with relic density and direct detection constraints.