| 1. |
- Diakonov, Dmitri, et al.
(författare)
-
Theory of baryon resonances at large N-c
- 2013
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 88:7
-
Tidskriftsartikel (refereegranskat)abstract
- At large number of colors, N-c quarks in baryons are in a mean field of definite space and flavor symmetry. We write down the general Lorentz and flavor structure of the mean field, and derive the Dirac equation for quarks in that field. The resulting baryon resonances exhibit a hierarchy of scales: the crude mass is O(N-c), the intrinsic quark excitations are O(1), and each intrinsic quark state entails a finite band of collective excitations that are split as O(1/N-c). We build a (new) theory of these collective excitations, where the full dynamics is represented by only a few constants. In a limiting (but unrealistic) case when the mean field is spherically and flavor symmetric, our classification of resonances reduces to the SU(6) classification of the old nonrelativistic quark model. Although in the real world N-c is only three, we obtain a good accordance with the observed resonance spectrum up to 2 GeV.
|
|
| 2. |
- Moiseeva, A., et al.
(författare)
-
Chiral Expansion of Nucleon PDF at x similar to m(pi)/M-N
- 2014
-
Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 55:5-7, s. 389-394
-
Tidskriftsartikel (refereegranskat)abstract
- Based on the chiral perturbation theory, we investigate the low-energy dynamics of nucleon parton distributions. We show that in different regions of the momentum fraction x the chiral expansion is significantly different. For nucleon parton distributions these regions are characterized by x similar to 1, x similar to m(pi)/M-N and x similar to (m(pi)/M-N)(2). We derive extended counting rules for each region and obtain model-independent results for the nucleon parton distributions down to x greater than or similar to m(pi)(2)/M-N(2) approximate to 10(-2).
|
|
| 3. |
- Vladimirov, Alexey
(författare)
-
Generating function for web diagrams
- 2014
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:6
-
Tidskriftsartikel (refereegranskat)abstract
- We present the description of the exponentiated diagrams in terms of generating function within the universal diagrammatic technique. In particular, we show the exponentiation of the gauge theory amplitudes involving products of an arbitrary number of Wilson lines of arbitrary shapes, which generalizes the concept of web diagrams. The presented method gives a new viewpoint on the web diagrams and proves the non-Abelian exponentiation theorem.
|
|
| 4. |
- Vladimirov, Alexey, et al.
(författare)
-
Key Features of the TMD Soft-Factor Structure
- 2014
-
Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 55:5-7, s. 297-302
-
Tidskriftsartikel (refereegranskat)abstract
- We show that the geometry of the Wilson lines, entering the operator definition of the transverse-momentum dependent parton distributions and that of the soft factor, follows from the kinematics of the underlying physical process in conjunction with the gauge invariance of the QCD Lagrangian. We demonstrate our method in terms of concrete examples and determine the paths of the associated Wilson lines. The validation of the factorization theorem in our approach is postponed to future work.
|
|
| 5. |
- Vladimirov, Alexey
(författare)
-
TMD PDFs in the Laguerre polynomial basis
- 2014
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :8
-
Tidskriftsartikel (refereegranskat)abstract
- We suggest the modified matching procedure for TMD PDF to the integrated PDF aimed to increase the amount of perturbative information in the TMD PDF expression. The procedure consists in the selection and usage of the non-minimal operator basis, which restricts the expansion to desired general behavior. The implication of OPE allows to systematic account of the higher order corrections. In the case of TMD PDF we assume the Gaussian behavior, which suggests Laguerre polynomial basis as the best for the convergence of OPE. We present the leading and next-to-leading expression of TMD PDF in this basis. The obtained perturbative expression for the TMD PDF is valid in the wide region of b(T) (we estimate this region as b(T) less than or similar to 2 - 3GeV(-1) depending on x).
|
|
