Person: Scimemi, Ignazio
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 31
PublicationTMD factorization for dijet and heavy-meson pair in DIS(Springer, 2021-01-15) Del Castillo, Rafael; Echevarria, Miguel G.; Makris, Yiannis; Scimemi, IgnazioWe study a transverse momentum dependent (TMD) factorization framework for the processes of dijet and heavy-meson pair production in deep-inelastic-scattering in an electron-proton collider, considering the measurement of the transverse momentum imbalance of the two hard probes in the Breit frame. For the factorization theorem we employ soft-collinear and boosted-heavy-quark effective field theories. The factorized cross-section for both processes is sensitive to gluon unpolarized and linearly polarized TMD distributions and requires the introduction of a new soft function. We calculate the new soft function here at one-loop, regulating rapidity divergences with the delta -regulator. In addition, using a factorization consistency relation and a universality argument regarding the heavy-quark jet function, we obtain the anomalous dimension of the new soft function at two and three loops. PublicationRound table: nucleon tomography. What can we do better today than Rutherford 100 years ago?(E D P Sciences, 2017) Stefanis, N. G.; Alexandrou, Constantia; Tanja, Horn; Moutarde, Herve; Scimemi, IgnazioA survey is presented on the current status of 3D nucleon tomography. Several research frontiers are addressed that dominate modern physics from theory to current and future experiments. We have now a much more detailed spatial image of the nucleon thanks to various theoretical concepts and methods to describe its charge distribution and spin decomposition which are highlighted here. The progress of lattice computations of these quantities is reported and the prospects of what we can come to expect in the near future are discussed. Multi-dimensional maps of the nucleon's partonic structure appear now within reach of forthcoming experiments. PublicationTransverse Momentum Dependent (TMD) Parton Distribution Functions: Status and Prospects(arXiv, 2015-07-19) Angeles Martinez, R.; Bacchetta, A.; Balitsky, I.I.; Boer, D.; Boglione, M.; Boussarie, R.; Ceccopieri, F.A.; Cherednikov, I.O.; Connor, P.; Echevarria, M.G.; Ferrera, G.; Grados Luyando, J.; Hautmann, F.; Jung, H.; Kasemets, T.; Kutak, K.; Lansberg, J.P.; Lelek, A.; Lykasov, G.; Madrigal Martinez, J.D.; Mulders, P.J.; Nocera, E.R.; Petreska, E.; Pisano, C.; Plačakytė, R.; Radescu, V.; Radici, M.; Schnell, G.; Scimemi, Ignazio; Signori, A.; Szymanowski, L.; Taheri Monfared, S.; Van der Veken, F.F.; van Haevermaet, H.J.; Van Mechelen, P.; Vladimirov, A.A.; Wallon, S.We provide a concise overview on transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q_T spectra of Higgs and vector bosons for low q_T, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present an application of a new tool, TMDlib, to parton density fits and parameterizations. PublicationTransverse momentum dependent fragmentation function at next-to-next-to-leading order(American Physical Society, 2016-01-21) Echevarria, Miguel G.; Scimemi, Ignazio; Vladimirov, AlekseyWe calculate the unpolarized transverse momentum dependent fragmentation function at next-to-next-to-leading order, evaluating separately the transverse momentum dependent (TMD) soft factor and the TMD collinear correlator. For the first time, the cancellation of spurious rapidity divergences in a properly defined individual TMD beyond the first nontrivial order is shown. This represents a strong check of the given TMD definition. We extract the matching coefficient necessary to perform the transverse momentum resummation at next-to-next-to-next-to-leading-logarithmic accuracy. The universal character of the soft function, which enters the definition of all (un)polarized TMD distribution/fragmentation functions, facilitates the future calculation of all the other TMDs and their coefficients at next-to-next-to-leading order, pushing forward the accuracy of theoretical predictions for the current and next generation of high energy colliders. PublicationAnalysis of vector boson production within TMD factorization(Springer, 2018-01-30) Scimemi, Ignazio; Vladimirov, Alexey A.We present a comprehensive analysis and extraction of the unpolarized transverse momentum dependent (TMD) parton distribution functions, which are fundamental constituents of the TMD factorization theorem. We provide a general review of the theory of TMD distributions, and present a new scheme of scale fixation. This scheme, called the zeta-prescription, allows to minimize the impact of perturbative logarithms in a large range of scales and does not generate undesired power corrections. Within zeta-prescription we consistently include the perturbatively calculable parts up to next-to-next-to-leading order (NNLO), and perform the global fit of the Drell-Yan and Z-boson production, which include the data of E288, Tevatron and LHC experiments. The non-perturbative part of the TMDs are explored checking a variety of models. We support the obtained results by a study of theoretical uncertainties, perturbative convergence, and a dedicated study of the range of applicability of the TMD factorization theorem. The considered non-perturbative models present significant differences in the fitting behavior, which allow us to clearly disfavor most of them. The numerical evaluations are provided by the arTeMiDe code, which is introduced in this work and that can be used for current/future TMD phenomenology. PublicationSystematic analysis of double-scale evolution(Springer, 2018-08-01) Scimemi, Ignazio; Vladimirov, AlexeyOften the factorization of differential cross sections results in the definition of fundamental hadronic functions/distributions which have a double-scale evolution, as provided by a pair of coupled equations. Typically, the two scales are the renormalization and rapidity scales. The two-dimensional structure of their evolution is the object of the present study. In order to be more specific, we consider the case of the transverse momentum dependent distributions (TMD). Nonetheless, most of our findings can be used with other double-scale parton distributions. On the basis of the two-dimensional structure of TMD evolution, we formulate the general statement of the ζ-prescription introduced in , and we define an optimal TMD distribution, which is a scaleless model-independent universal non-perturbative function. Within this formulation the non-perturbative definition of the distribution is disentangled from the evolution, which clarifies the separation of perturbative and non-perturbative effects in the phenomenology. A significant part of this work is devoted to the study of the effects of truncation of perturbation theory on the double-scale evolution. We show that within truncated perturbation theory the solution of evolution equations is ambiguous and this fact generates extra uncertainties within the resummed cross-section. The alternatives to bypass this issue are discussed. Finally, we discuss the sources and distribution of the scale variation uncertainties. PublicationQuarkonium TMD fragmentation functions in NRQCD.(Springer, 2020-10-26) Echevarria, Miguel G.; Makris, Yiannis; Scimemi, IgnazioWe study the transverse-momentum spectrum of quarkonium production from single light-parton fragmentation mechanism. In the case of semi-inclusive deep inelastic scattering, we observe that there are two possible initiating processes, namely photongluon fusion and light-quark fragmentation. For the second case we derive the factorization theorem, which involves a new hadronic quantity: the quarkonium transverse-momentumdependent fragmentation functions in NRQCD. We calculate their matching onto the non-perturbative long distance matrix elements at the lowest order in the strong-coupling constant, O(alpha(2)(s)). Focusing on the case of the electron-ion collider, we make a comparative phenomenological study of the two production mechanisms and find the regions of the phase space where one is dominant over the other. PublicationTMDs: Evolution, modeling, precision(EDP Sciences: EPJ Open Access, 2015) D'Alesio, Umberto; Echevarria, Miguel G.; Melis, Stefano; Scimemi, IgnazioThe factorization theorem for qT spectra in Drell-Yan processes, boson production and semi-inclusive deep inelastic scattering allows for the determination of the non-perturbative parts of transverse momentum dependent parton distribution functions. Here we discuss the fit of Drell-Yan and Z-production data using the transverse momentum dependent formalism and the resummation of the evolution kernel. We find a good theoretical stability of the results and a final chi(2)/points less than or similar to 1. We show how the fixing of the non-perturbative pieces of the evolution can be used to make predictions at present and future colliders. PublicationTransverse-momentum-dependent distributions with jets(Amer Physical Soc, 2018-10-03) Gutierrez Reyes, Daniel; Scimemi, Ignazio; Waalewijn, Wouter J.; Zoppi, LorenzoWe investigate the use of jets to measure transverse- momentum-dependent distributions (TMDs). The example we use to present our framework is the dijet momentum decorrelation at lepton colliders. Translating this momentum decorrelation into an angle Ө << 1, we analyze the factorization of the cross section for the cases Ө >> R, Ө similar to R, and Ө << R, where R is the jet radius. Critically, for the winner-take-all axis, the jet TMD has the same double-scale renormalization group evolution as TMD fragmentation functions for all radii R. TMD fragmentation functions in factorization theorems may then simply be replaced by the jet TMDs we calculate, and all ingredients to perform the resummation to next-to-next-to- leading logarithmic accuracy are available. Our approach also applies to semi-inclusive deep inelastic scattering, where a jet instead of a hadron is measured in the final state, and we find a clean method to probe the intrinsic transverse momentum of quarks and gluons in the proton that is less sensitive to final- state nonperturbative effects. PublicationTransverse momentum dependent distributions in dijet and heavy hadron pair production at EIC(Springer, 2022-03-08) Fernández del Castillo, Rafael; Echevarria, Miguel G.; Makris, Yiannis; Scimemi, IgnazioWe discuss the measurement of gluon transverse momentum distribution (TMD) in dijet and heavy hadron pair (HHP) production in semi-inclusive deep inelastic scattering. The factorization of these processes in position space shows the appearance of a specific new soft factor matrix element on top of angular and complex valued anomalous dimensions. We show in detail how these features can be treated consistently and we discuss a scale prescription for the evolution kernel of the dijet soft function. As a result we obtain phenomenological predictions for unpolarized and angular modulated cross-sections for the electron-ion collider (EIC) using current available information on unpolarized TMD.