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Author |
Kleiss, R.H.P.; Malamos, I.; Papadopoulos, C.G.; Verheyen, R. |
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Title |
Counting to one: reducibility of one- and two-loop amplitudes at the integrand level |
Type |
Journal Article |
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Year |
2012 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume  |
12 |
Issue |
12 |
Pages |
038 - 24pp |
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Keywords |
QCD Phenomenology; NLO Computations |
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Abstract |
Calculation of amplitudes in perturbative quantum field theory involve large loop integrals. The complexity of those integrals, in combination with the large number of Feynman diagrams, make the calculations very difficult. Reduction methods proved to be very helpful, lowering the number of integrals that need to be actually calculated. Especially reduction at the integrand level improves the speed and set-up of these calculations. In this article we demonstrate, by counting the numbers of tensor structures and independent coefficients, how to write such relations at the integrand level for one-and two-loop amplitudes. We clarify their connection to the so-called spurious terms at one loop and discuss their structure in the two-loop case. This method is also applicable to higher loops, and the results obtained apply to both planar and non-planar diagrams. |
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Address |
[Kleiss, Ronald H. P.; Verheyen, Rob] Radboud Univ Nijmegen, NL-6525 ED Nijmegen, Netherlands, Email: R.Kleiss@science.ru.nl; |
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Springer |
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English |
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1126-6708 |
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Notes |
WOS:000313123800038 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1346 |
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Author |
Llanes Jurado, J.; Rodrigo, G.; Torres Bobadilla, W.J. |
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Title |
From Jacobi off-shell currents to integral relations |
Type |
Journal Article |
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Year |
2017 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
12 |
Issue |
12 |
Pages |
122 - 22pp |
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Keywords |
NLO Computations; QCD Phenomenology |
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Abstract |
In this paper, we study off-shell currents built from the Jacobi identity of the kinematic numerators of gg -> X with X = ss, q (q) over bar, gg. We find that these currents can be schematically written in terms of three-point interaction Feynman rules. This representation allows for a straightforward understanding of the Colour-Kinematics duality as well as for the construction of the building blocks for the generation of higher-multiplicity tree-level and multi-loop numerators. We also provide one-loop integral relations through the Loop-Tree duality formalism with potential applications and advantages for the computation of relevant physical processes at the Large Hadron Collider. We illustrate these integral relations with the explicit examples of QCD one-loop numerators of gg -> ss. |
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Address |
[Llanes Jurado, Jose; Rodrigo, German; Torres Bobadilla, William J.] Univ Valencia, Inst Fis Corpuscular, CSIC, Parc Cient, E-46980 Valencia, Spain, Email: jollaju@alumni.uv.es; |
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Springer |
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1029-8479 |
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Notes |
WOS:000418560700004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
3431 |
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Author |
Mateu, V.; Rodrigo, G. |
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Title |
Oriented event shapes at (NLL)-L-3 + O(alpha(2)(S)) |
Type |
Journal Article |
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Year |
2013 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
11 |
Issue |
11 |
Pages |
030 - 29pp |
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Keywords |
Jets; NLO Computations |
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Abstract |
We analyze oriented event-shapes in the context of Soft-Collinear Effective Theory (SCET) and in fixed-order perturbation theory. Oriented event-shapes are distributions of event-shape variables which are differential on the angle theta(T) that the thrust axis forms with the electron-positron beam. We show that at any order in perturbation theory and for any event shape, only two angular structures can appear: F-0 = 3/8 (1+cos(2) theta(T)) and F-1 = (1 – 3 cos(2) theta(T)). When integrating over theta(T) to recover the more familiar event-shape distributions, only F-0 survives. The validity of our proof goes beyond perturbation theory, and hence only these two structures are present at the hadron level. The proof also carries over massive particles. Using SCET techniques we show that singular terms can only arise in the F-0 term. Since only the hard function is sensitive to the orientation of the thrust axis, this statement applies also for recoil-sensitive variables such as Jet Broadening. We show how to carry out resummation of the singular terms at (NLL)-L-3 for Thrust, Heavy-Jet Mass, the sum of the Hemisphere Masses and C-parameter by using existing computations in SCET. We also compute the fixed-order distributions for these event-shapes at O(alpha(S)) analytically and at O(alpha(2)(S)) with the program Event2. |
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Address |
[Mateu, Vicent; Rodrigo, German] Univ Valencia, Consejo Super Invest Cient, Inst Fis Corpuscular, E-46980 Paterna, Valencia, Spain, Email: mateu@ific.uv.es; |
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Springer |
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English |
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ISSN |
1029-8479 |
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Conference |
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Notes |
WOS:000326699400001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
1675 |
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Author |
Buchta, S.; Chachamis, G.; Draggiotis, P.; Malamos, I.; Rodrigo, G. |
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Title |
On the singular behaviour of scattering amplitudes in quantum field theory |
Type |
Journal Article |
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Year |
2014 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
11 |
Issue |
11 |
Pages |
014 - 13pp |
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Keywords |
QCD Phenomenology; NLO Computations |
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Abstract |
We analyse the singular behaviour of one-loop integrals and scattering amplitudes in the framework of the loop-tree duality approach. We show that there is a partial cancellation of singularities at the loop integrand level among the different components of the corresponding dual representation that can be interpreted in terms of causality. The remaining threshold and infrared singularities are restricted to a finite region of the loop momentum space, which is of the size of the external momenta and can be mapped to the phase-space of real corrections to cancel the soft and collinear divergences. |
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Address |
[Buchta, Sebastian; Chachamis, Grigorios; Malamos, Ioannis; Rodrigo, German] Univ Valencia, CSIC, Inst Fis Corpuscular, E-46980 Valencia, Spain, Email: sbuchta@ific.uv.es; |
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Springer |
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English |
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1029-8479 |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000344788000003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2065 |
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Author |
Bierenbaum, I.; Catani, S.; Draggiotis, P.; Rodrigo, G. |
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Title |
A tree-loop duality relation at two loops and beyond |
Type |
Journal Article |
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Year |
2010 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
10 |
Issue |
10 |
Pages |
073 - 22pp |
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Keywords |
NLO Computations; QCD |
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Abstract |
The duality relation between one-loop integrals and phase-space integrals, developed in a previous work, is extended to higher-order loops. The duality relation is realized by a modification of the customary +i0 prescription of the Feynman propagators, which compensates for the absence of the multiple-cut contributions that appear in the Feynman tree theorem. We rederive the duality theorem at one-loop order in a form that is more suitable for its iterative extension to higher-loop orders. We explicitly show its application to two-and three-loop scalar master integrals, and we discuss the structure of the occurring cuts and the ensuing results in detail. |
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Address |
[Bierenbaum, Isabella; Draggiotis, Petros; Rodrigo, German] Univ Valencia, Consejo Super Invest Cient, Inst Fis Corpuscular, E-46071 Valencia, Spain, Email: isabella.bierenbaum@ific.uv.es |
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Springer |
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English |
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ISSN |
1126-6708 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
ISI:000284147000016 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial |
326 |
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| Permanent link to this record |
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Author |
Sborlini, G.F.R.; de Florian, D.; Rodrigo, G. |
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Title |
Triple collinear splitting functions at NLO for scattering processes with photons |
Type |
Journal Article |
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Year |
2014 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
10 |
Issue |
10 |
Pages |
161 - 29pp |
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Keywords |
NLO Computations |
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Abstract |
We present splitting functions in the triple collinear limit at next-to-leading order. The computation was performed in the context of massless QCD+QED, considering only processes which include at least one photon. Through the comparison of the IR divergent structure of splitting amplitudes with the expected known behavior, we were able to check our results. Besides that we implemented some consistency checks based on symmetry arguments and cross-checked the results among them. Studying photon-started processes, we obtained very compact results. |
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Address |
[Sborlini, German F. R.; de Florian, Daniel] Univ Buenos Aires, FCEyN, Dept Fis, RA-1428 Buenos Aires, DF, Argentina, Email: gfsborlini@df.uba.ar; |
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Springer |
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English |
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ISSN |
1029-8479 |
ISBN |
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Expedition |
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Conference |
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Notes |
WOS:000347905900001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2082 |
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Author |
Sborlini, G.F.R.; Driencourt-Mangin, F.; Rodrigo, G. |
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Title |
Four-dimensional unsubtraction with massive particles |
Type |
Journal Article |
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Year |
2016 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
10 |
Issue |
10 |
Pages |
162 - 34pp |
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Keywords |
NLO Computations |
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Abstract |
We extend the four-dimensional unsubtraction method, which is based on the loop-tree duality (LTD), to deal with processes involving heavy particles. The method allows to perform the summation over degenerate IR configurations directly at integrand level in such a way that NLO corrections can be implemented directly in four space-time dimensions. We define a general momentum mapping between the real and virtual kinematics that accounts properly for the quasi-collinear configurations, and leads to an smooth massless limit. We illustrate the method first with a scalar toy example, and then analyse the case of the decay of a scalar or vector boson into a pair of massive quarks. The results presented in this paper are suitable for the application of the method to any multipartonic process. |
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Address |
[Sborlini, German F. R.; Driencourt-Mangin, Felix; Rodrigo, German] Univ Valencia, CSIC, Inst Fis Corpuscular, Parc Cient, E-46980 Valencia, Spain, Email: german.sborlini@ific.uv.es; |
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Springer |
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English |
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ISSN |
1029-8479 |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000387374000001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
2853 |
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Author |
de Florian, D.; Sborlini, G.F.R.; Rodrigo, G. |
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Title |
Two-loop QED corrections to the Altarelli-Parisi splitting functions |
Type |
Journal Article |
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Year |
2016 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
10 |
Issue |
10 |
Pages |
056 - 16pp |
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Keywords |
NLO Computations; QCD Phenomenology |
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Abstract |
We compute the two-loop QED corrections to the Altarelli-Parisi (AP) splitting functions by using a deconstructive algorithmic Abelianization of the well-known NLO QCD corrections. We present explicit results for the full set of splitting kernels in a basis that includes the leptonic distribution functions that, starting from this order in the QED coupling, couple to the partonic densities. Finally, we perform a phenomenological analysis of the impact of these corrections in the splitting functions. |
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Address |
[de Florian, Daniel] UNSAM, ICAS, Campus Miguelete,25 Mayo & Francia, RA-1650 Buenos Aires, DF, Argentina, Email: deflo@unsam.edu.ar; |
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Springer |
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English |
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1029-8479 |
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Conference |
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Notes |
WOS:000386669900007 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2863 |
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Author |
Chachamis, G.; Deak, M.; Hentschinski, M.; Rodrigo, G.; Sabio Vera, A. |
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Title |
Single bottom quark production in kT-factorisation |
Type |
Journal Article |
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Year |
2015 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
09 |
Issue |
9 |
Pages |
123 - 17pp |
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Keywords |
QCD Phenomenology; NLO Computations |
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Abstract |
We present a study within the k(T)-factorisation scheme on single bottom quark production at the LHC. In particular, we calculate the rapidity and transverse momentum differential distributions for single bottom quark/anti-quark production. In our setup, the unintegrated gluon density is obtained from the NLx BFKL Green function whereas we included mass effects to the Lx heavy quark jet vertex. We compare our results to the corresponding distributions predicted by the usual collinear factorisation scheme. The latter were produced with Pythia 8.1. |
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Address |
[Chachamis, Grigorios; Sabio Vera, Agustin] Univ Autonoma Madrid, E-28049 Madrid, Spain, Email: grigorios.chachamis@csic.es; |
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Springer |
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English |
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1029-8479 |
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Conference |
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Notes |
WOS:000361753300003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2614 |
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| Permanent link to this record |
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Author |
Sborlini, G.F.R.; Driencourt-Mangin, F.; Hernandez-Pinto, R.J.; Rodrigo, G. |
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Title |
Four-dimensional unsubtraction from the loop-tree duality |
Type |
Journal Article |
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Year |
2016 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
08 |
Issue |
8 |
Pages |
160 - 42pp |
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Keywords |
NLO Computations |
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Abstract |
We present a new algorithm to construct a purely four dimensional representation of higher-order perturbative corrections to physical cross-sections at next-to-leading order (NLO). The algorithm is based on the loop-tree duality (LTD), and it is implemented by introducing a suitable mapping between the external and loop momenta of the virtual scattering amplitudes, and the external momenta of the real emission corrections. In this way, the sum over degenerate infrared states is performed at integrand level and the cancellation of infrared divergences occurs locally without introducing subtraction counter-terms to deal with soft and final-state collinear singularities. The dual representation of ultraviolet counter-terms is also discussed in detail, in particular for self-energy contributions. The method is first illustrated with the scalar three-point function, before proceeding with the calculation of the physical cross-section for gamma* -> q (q) over bar (g), and its generalisation to multi-leg processes. The extension to next-to-next-to-leading order (NNLO) is briefly commented. |
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Address |
[Sborlini, German F. R.; Driencourt-Mangin, Felix; Hernandez-Pinto, Roger J.; Rodrigo, German] Univ Valencia, Inst Fis Corpuscular, CSIC, Parc Cient, E-46980 Valencia, Spain, Email: gfsborlini@df.uba.ar; |
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Springer |
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Language |
English |
Summary Language |
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Abbreviated Series Title |
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Series Volume |
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ISSN |
1029-8479 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000382685100001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2793 |
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| Permanent link to this record |
