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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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1029-8479 |
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WOS:000344788000003 |
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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 |
Sborlini, G.F.R.; de Florian, D.; Rodrigo, G. |
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Title |
Double collinear splitting amplitudes at next-to-leading order |
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 |
01 |
Issue |
1 |
Pages |
018 - 55pp |
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Keywords |
NLO Computations; Hadronic Colliders |
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Abstract |
We compute the next-to-leading order (NLO) QCD corrections to the 1 -> 2 splitting amplitudes in different dimensional regularization (DREG) schemes. Besides recovering previously known results, we explore new DREG schemes and analyze their consistency by comparing the divergent structure with the expected behavior predicted by Catani's formula. Through the introduction of scalar-gluons, we show the relation among splittings matrices computed using different schemes. Also, we extended this analysis to cover the double collinear limit of scattering amplitudes in the context of QCD+QED. |
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Address |
[Sborlini, German F. R.; de Florian, Daniel] Univ Buenos Aires, FCEyN, Dept Fis, RA-1428 Buenos Aires, Argentina, Email: gfsborlini@df.uba.ar; |
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Springer |
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1029-8479 |
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Notes |
WOS:000329617800009 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1698 |
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Author |
Sborlini, G.F.R.; de Florian, D.; Rodrigo, G. |
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Title |
Polarized triple-collinear splitting functions at NLO for processes with photons |
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 |
03 |
Issue |
3 |
Pages |
021 - 30pp |
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Keywords |
NLO Computations |
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Abstract |
We compute the polarized splitting functions in the triple collinear limit at next-to-leading order accuracy (NLO) in the strong coupling alpha(S), for the splitting processes gamma -> qq gamma, gamma -> qqg and g -> qq gamma. The divergent structure of each splitting function was compared to the predicted behaviour according to Catani's formula. The results obtained in this paper are compatible with the unpolarized splitting functions computed in a previous article. Explicit results for NLO corrections are presented in the context of conventional dimensional regularization (CDR). |
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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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1029-8479 |
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Notes |
WOS:000351363800004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2169 |
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Author |
Bierenbaum, I.; Buchta, S.; Draggiotis, P.; Malamos, I.; Rodrigo, G. |
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Title |
Tree-loop duality relation beyond single poles |
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 |
03 |
Issue |
3 |
Pages |
025 - 24pp |
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Keywords |
QCD Phenomenology; NLO Computations |
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Abstract |
We develop the Tree-Loop Duality Relation for two- and three-loop integrals with multiple identical propagators (multiple poles). This is the extension of the Duality Relation for single poles and multi-loop integrals derived in previous publications. We prove a generalization of the formula for single poles to multiple poles and we develop a strategy for dealing with higher-order pole integrals by reducing them to single pole integrals using Integration By Parts. |
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Address |
Univ Hamburg, Inst Theoret Phys 2, D-22761 Hamburg, Germany, Email: isabella.bierenbaum@desy.de; |
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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:000317521200025 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1418 |
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Author |
Catani, S.; de Florian, D.; Rodrigo, G. |
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Title |
Space-like (vs. time-like) collinear limits in QCD: is factorization violated? |
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 |
07 |
Issue |
7 |
Pages |
026 - 88pp |
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Keywords |
NLO Computations; Hadronic Colliders |
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Abstract |
We consider the singular behaviour of QCD scattering amplitudes in kinematical configurations where two or more momenta of the external partons become collinear. At the tree level, this behaviour is known to be controlled by factorization formulae in which the singular collinear factor is universal (process independent). We show that this strict (process-independent) factorization is not valid at one-loop and higher-loop orders in the case of the collinear limit in space-like regions (e. g., collinear radiation from initial-state partons). We introduce a generalized version of all-order collinear factorization, in which the space-like singular factors retain some dependence on the momentum and colour charge of the non-collinear partons. We present explicit results on one-loop and two-loop amplitudes for both the two-parton and multiparton collinear limits. At the level of squared amplitudes and, more generally, cross sections in hadron-hadron collisions, the violation of strict collinear factorization has implications on the non-abelian structure of logarithmically-enhanced terms in perturbative calculations (starting from the next-to-next-to-leading order) and on various factorization issues of mass singularities (starting from the next-to-next-to-next-to-leading order). |
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Address |
[Catani, Stefano] Univ Florence, Sez Firenze, Ist Nazl Fis Nucl, I-50019 Florence, Italy, Email: catani@fi.infn.it; |
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Springer |
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English |
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Series Volume |
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Series Issue |
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Edition |
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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 |
WOS:000307298400026 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1160 |
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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 |
ISBN |
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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 |
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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ISSN |
1126-6708 |
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Conference |
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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 |
Hernandez-Pinto, R.J.; Sborlini, G.F.R.; Rodrigo, G. |
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Title |
Towards gauge theories in four dimensions |
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 |
02 |
Issue |
2 |
Pages |
044 - 14pp |
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Keywords |
NLO Computations |
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Abstract |
The abundance of infrared singularities in gauge theories due to unresolved emission of massless particles (soft and collinear) represents the main difficulty in perturbative calculations. They are typically regularized in dimensional regularization, and their subtraction is usually achieved independently for virtual and real corrections. In this paper, we introduce a new method based on the loop-tree duality (LTD) theorem to accomplish the summation over degenerate infrared states directly at the integrand level such that the cancellation of the infrared divergences is achieved simultaneously, and apply it to reference examples as a proof of concept. Ultraviolet divergences, which are the consequence of the point-like nature of the theory, are also reinterpreted physically in this framework. The proposed method opens the intriguing possibility of carrying out purely four-dimensional implementations of higher-order perturbative calculations at next-to-leading order (NLO) and beyond free of soft and final-state collinear subtractions. |
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Address |
[Hernandez-Pinto, Roger J.; Sborlini, German F. R.; Rodrigo, German] Univ Valencia, Inst Fis Corpuscular, Consejo Super Invest Cient, Pare Cient, E-46980 Valencia, Spain, Email: rogerjose.hernandez@ific.uv.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:000375270700002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2661 |
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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 |
Campanario, F.; Kerner, M.; Ninh, L.D.; Rosario, I. |
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Title |
Diphoton production in vector-boson scattering at the LHC at next-to-leading order QCD |
Type |
Journal Article |
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Year |
2020 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
06 |
Issue |
6 |
Pages |
072 - 25pp |
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Keywords |
NLO Computations |
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Abstract |
In this paper, we present results at next-to-leading order (NLO) QCD for photon pair production in association with two jets via vector boson scattering within the Standard Model (SM), and also in an effective field theory framework with anomalous gauge coupling effects via bosonic dimension-6 and 8 operators. We observe that, com- pared to other processes in the class of two electroweak (EW) vector boson production in association with two jets, more exclusive cuts are needed in order to suppress the SM QCD-induced background channel. As expected, the NLO QCD corrections reduce the scale uncertainties considerably. Using a well-motivated dynamical scale choice, we find moderate K -factors for the EW-induced process while the QCD-induced channel receives much larger corrections. Furthermore, we observe that applying a cut of Delta phi(cut)(j2 gamma 1) <2.5 for the second hardest jet and the hardest photon helps to increase the signal significance and reduces the impact of higher-order QCD corrections. |
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Address |
[Campanario, Francisco; Rosario, Ivan] Univ Valencia, CSIC, IFIC, Div Theory, E-46980 Valencia, Spain, Email: francisco.campanario@ific.uv.es; |
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Springer |
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English |
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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:000541147600003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4433 |
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