Literatura académica sobre el tema "TMD factorisation"

In this review, we describe the status of transverse momentum dependence (TMD) in double parton scattering (DPS). The different regions of TMD DPS are discussed, and expressions are given for the DPS cross section contributions that make use of as much perturbative information as possible. The regions are then combined with each other as well as single parton scattering to obtain a complete expression for the cross section. Particular emphasis is put on the differences and similarities to transverse momentum dependence in single parton scattering. We further discuss the status of the factorisation proof for double colour singlet production in DPS, which is now on a similar footing to the proofs for TMD factorisation in single Drell-Yan, discuss parton correlations, and give an outlook on possible research on DPS in the near future.

The inclusive large-pTproduction of a single pion, jet or direct photon, and Drell-Yan processes, are considered for proton-proton collisions in the kinematical range expected for the fixed-target experiment AFTER, proposed at LHC. For all these processes, predictions are given for the transverse single-spin asymmetry,AN, computed according to a Generalised Parton Model previously discussed in the literature and based on TMD factorisation. Comparisons with the results of a collinear twist-3 approach, recently presented, are made and discussed.

Abstract Using the colour dipole picture and the colour glass condensate effective theory, we study the diffractive production of two or three jets via coherent photon-nucleus interactions at high energy. We consider the hard regime where the photon virtuality and/or the transverse momenta of the produced jets are much larger than the saturation momentum Qs of the nuclear target. We show that, despite this hardness, the leading-twist contributions are controlled by relatively large parton configurations, with transverse sizes R ~ 1/Qs, which undergo strong scattering and probe gluon saturation. We demonstrate that these leading-twist contributions admit transverse-momentum dependent (TMD) factorisation, in terms of quark and gluon diffractive TMD distribution functions, for which we obtain explicit expressions from first principles. We go beyond our previous work by evaluating the contributions involving the quark diffractive distributions and by establishing that their DGLAP evolution emerges via controlled calculations within the colour dipole picture. We find the same expression for the quark diffractive TMD in two different processes (semi-inclusive diffraction and the diffractive production of quark-gluon dijets), thus demonstrating its universality.

Abstract Within the colour dipole picture for deep inelastic scattering at small Bjorken x, we study the production of a pair of relatively hard jets via coherent diffraction. By “relatively hard” we mean that the transverse momenta of the two jets — the quark (q) and the antiquark ($$ \overline{q} $$ q ¯ ) generated by the decay of the virtual photon — are much larger than the target saturation momentum Qs(Yℙ) evaluated at the rapidity gap Yℙ. We argue that the typical final-state configurations are such that the hard $$ q\overline{q} $$ q q ¯ dijets are accompanied by a semi-hard gluon jet, with a transverse momentum of the order of Qs(Yℙ). The presence of this third jet ensures that the scattering is strong and thus avoids the strong suppression of exclusive (hard) dijet production due to colour transparency. For such “2+1” jet configurations, we demonstrate that both the emission of the semi-hard gluon and its scattering with the hadronic target can be factorised in terms of an effective gluon-gluon dipole. This effective description, originally proposed in [1–7], builds a bridge between the colour dipole picture and the transverse-momentum dependent (TMD) version of the collinear factorisation: the cross-section for diffractive 2+1 jets can be written as the product between a hard factor describing the $$ q\overline{q} $$ q q ¯ dijets and a semi-hard factor expressing the unintegrated gluon distribution of the Pomeron. The latter is controlled by gluon dipole scattering in the black disk limit and hence is strongly sensitive to gluon saturation. By integrating out the kinematics of the 3 jets, we obtain the $$ q\overline{q}g $$ q q ¯ g contribution to the diffractive structure function in collinearly-factorised form.

AbstractWe argue that semi-inclusive photo-production of a pair of hard jets via coherent diffraction in nucleus-nucleus ultra-peripheral collisions at high energy is a golden channel to study gluon saturation. The dominant contribution is the diffractive production of three jets in an asymmetric configuration. Two of the jets are hard and propagate at nearly central pseudo-rapidities. The third jet is semi-hard, with transverse momentum comparable to the nuclear saturation momentum, and is well separated in pseudo-rapidity from the hard dijets. The emission of the semi-hard jet allows for strong scattering, thus avoiding the “higher-twist” suppression of the exclusive dijet production due to colour transparency. We compute the trijet cross-section using the diffractive TMD factorisation which emerges from the CGC effective theory at high energy. The cross-section is controlled by gluon saturation, which leaves its imprints on the structure of the final state, notably on the rapidity distribution.

Abstract Background So far, the safety evaluation of food additives has been performed substance by substance, while in real life, millions of individuals are exposed to mixtures of food additives daily. According to preliminary experimental data, some of these chemicals, alone and/or in synergy are suspected to impact metabolic health. The objective of this study was to investigate for the first time the associations between exposure to mixtures of food additives and type 2 diabetes (T2D) risk in a large prospective cohort of French adults. Methods Participants (n = 108,783, 79.2% women, mean age=42.4 years, SD = 14.6) from the NutriNet-Santé cohort (2009-2024) completed repeated 24h-dietary records, detailing industrial product brands. Additive exposure was assessed using composition databases and laboratory assays. Five mixtures of additives were identified through non-negative matrix factorisation (NMF). Associations between these mixtures and the risk of T2D were characterised using multivariable proportional hazards Cox models adjusted for known risk factors. Findings 1115 participants were identified with T2D during follow-up. Two additive mixtures were associated with increased T2D risk. The first mixture included higher exposure to modified starches E14xx, pectins E440, guar gum E412, carrageenan E407, and polyphosphates E452 (HRper 1SD increment=1.11 [1.05-1.18]), p < 0.0001). The second mixture comprised citric acid E330, sodium citrates E331, phosphoric acid E338, sulphite ammonia caramel E150d, acesulfame-K E950, aspartame E951, sucralose E955 and arabic gum E414 (HR1SD=1.13 [1.08-1.18]), p < 0.0001). Interpretation This large prospective cohort study revealed direct associations between T2D risk and exposure to two food additive mixtures. Molecular epidemiology and experimental studies will be necessary to depict underlying mechanisms and potential cocktail effects. Key messages • Consumed together, widely used food additives may contribute to T2D aetiology, shedding light on the detrimental impact of highly processed foods on metabolic health. • This study highlights positives associations between T2D risk and exposure to two food additive mixtures.

Avec le Large Hadron Collider (LHC) et les expériences à haute énergie à venir avec le Electron-Ion Collider (EIC), nous pouvons explorer la structure élémentaire des protons. Autrefois, on pensait que les protons étaient composés de trois quarks de valence (deux quarks up et un quark down), mais nous savons désormais qu'ils contiennent également des paires éphémères de quark-antiquark de tous les six types de quarks ainsi que des gluons, les médiateurs de la force nucléaire forte, décrits par la chromodynamique quantique (QCD). Pour sonder la structure interne d'un nucléon, les fonctions de distribution des partons (PDFs) quantifient la manière dont le moment est distribué parmi les partons (quarks et gluons) longitudinalement dans une réaction, tandis transverse-momentum-dependent PDFs (TMDs) ajoutent des informations sur le moment transverse. Bien que les TMDs de quarks soient de mieux en mieux comprises, nos connaissances sur les TMDs de gluons sont encore très limitées. Cette étude se concentre sur l'extraction des TMDs de gluons à travers la production de quarkonium, en particulier des mésons J/psi, au LHC et à l'EIC, puisque le quarkonium, un méson formé par une paire quark-antiquark lourde de même saveur, provient principalement des gluons partoniques. Pour étudier de tels processus, il est essentiel qu'ils puissent être factorisés. Cela signifie que la section efficace, représentant la probabilité du processus, est une convolution d'un terme QCD perturbatif, qui peut être calculé théoriquement, et de termes non perturbatifs comme les TMDs et les éléments de matrice à longue distance (LDMEs) qui décrivent la formation du quarkonium, et qui doivent être extraits par expérimentation. Pour la production de J/psi dans les collisions électron-proton, la neutralité de couleur nécessite l'émission de gluons à faible énergie. Cela introduit la fonction de forme, cruciale pour réconcilier les cadres TMD et collinéaire (en termes de PDF) dans leur régime de recouvrement. Les calculs montrent que la fonction de forme est universelle, accompagnée d'un facteur dépendant du processus, et qu'elle devrait également jouer un rôle dans la production directe de quarkonium neutre en couleur à des ordres supérieurs. Les prédictions d'une asymétrie azimutale, liée au rapport entre les TMDs des gluons polarisés linéairement et non polarisés, suggèrent des effets mesurables à l'EIC pour sonder ces TMDs et ces fonctions de forme.De plus, un nouveau facteur non perturbatif de Sudakov a été développé pour le formalisme de l'évolution des TMD, améliorant les modèles gaussiens en extrapolant le comportement perturbatif connu dans le régime non perturbatif. Bien que novateur, ce facteur reste à déterminer expérimentalement. L'utilisation de ce nouveau facteur de Sudakov a permis d'obtenir un accord avec les données récentes de sections efficaces normalisées pour la production de paires de J/psi au LHCb. Cependant, les incertitudes liées à la variation des échelles nécessitent des corrections à des ordres supérieurs. Les études futures au LHC, telles que la production de paires d'Upsilon et la production de paires de J/psi avec un proton stationnaire, pourraient révéler davantage d'informations sur les TMDs de gluons à des énergies et fractions de moment plus élevées. Pour l'EIC, des progrès ont été réalisés vers un spectre complet pour la production de J/psi, en se concentrant sur les contributions indépendantes de l'angle. Bien que les sections efficaces TMD et collinéaires suivent des lois de puissance significativement différentes dans le régime cinématique à explorer par l'EIC, nous ne trouvons aucun problème de correspondance, car les sections efficaces TMD se trouvent au-dessus des sections collinéaires dans la région où la correspondance est censée se produire
With the Large Hadron Collider (LHC) and the upcoming Electron-Ion Collider (EIC) high-energy experiments we can investigate the elementary structure of protons. In the past, protons were thought to comprise three valence quarks (two up, one down), but now we know they also contain short-lived quark-antiquark pairs of all six quark types and gluons, the mediators of the strong nuclear force, described by quantum chromodynamics (QCD). To probe the internal structure of a nucleon, parton distribution functions (PDFs) quantify how momentum is distributed among partons (quarks and gluons) longitudinally in a reaction, while transverse-momentum-dependent PDFs (TMDs) add transverse momentum information. While quark TMDs are getting better understood, our knowledge of gluon TMDs is still very limited. This study focuses on extracting gluon TMDs through quarkonium production, particularly J/psi mesons, at the LHC and EIC, since quarkonium, a meson formed by a heavy quark-antiquark pair of the same heavy flavour, mainly originates from partonic gluons. To study such processes, it is essential that they can be factorised. This means that the cross section, representing process likelihood, is a convolution of a perturbative QCD term, that can be theoretically calculated, and nonperturbative terms like the TMDs and the long-distance matrix elements (LDMEs) which describe the formation of the quarkonium, that need to be extracted from an experiment. For J/psi production in electron-proton collisions, colour neutrality requires low-energy gluon emission. This introduces the shape function, crucial for reconciling TMD and collinear frameworks (in terms of PDFs) in their overlapping regime. Calculations show the shape function is universal, while accompanied by a process-dependent factor, and it is expected to play a role in direct colour-neutral quarkonium production at higher orders as well. Predictions of an azimuthal asymmetry, linked to the ratio of linearly polarised to unpolarised gluon TMDs, suggest measurable effects at the EIC to probe these TMDs and shape functions. Additionally, a novel nonperturbative Sudakov factor was developed for the TMD evolution formalism, improving upon Gaussian models by extrapolating known perturbative behaviour into the nonperturbative regime. While innovative, this factor remains to be determined by experiment. Employing this novel Sudakov factor agreement with recent normalised cross-section data for J/psi-pair production at the LHCb is found. However, scale variation uncertainties necessitate higher-order corrections. Future LHC studies, such as Upsilon-pair production and J/psi-pair production with one stationary proton, may reveal more about gluon TMDs at higher energies and momentum fractions. For the EIC, progress was made toward a complete spectrum for J/psi production, focusing on angle-independent contributions. Although the TMD and collinear cross sections follow significantly different power laws in the kinematic regime to be probed by the EIC, we find no matching issues, because the TMD cross sections lie above the collinear ones in the region where matching is expected to occur