We consider the production of a heavy quark pair in proton–proton collisions. For bottom and charm quarks, the final state invariant mass is typically much smaller than the collider energy (e.g. at ...the LHC), so that high-energy logarithms may spoil the perturbativity of the theoretical prediction at fixed order. The resummation of these logarithms to all orders is thus needed to obtain reliable predictions. In this work, we extend previous results on high-energy (or small-
x
) resummation to differential distributions in rapidity, transverse momentum and invariant mass, and implement them in the public code HELL.
We present a determination of the parton distribution functions (PDFs) of the proton from HERA data using a PDF parametrization inspired by a quantum statistical model of the proton dynamics. This ...parametrization is characterised by a very small number of parameters, yet it leads to a reasonably good description of the data, comparable with other parametrizations on the market. It may thus provide an alternative to standard parametrizations, useful for studying parametrization bias and to possibly simplify the fit procedure thanks to the small number of parameters. Interestingly, the model reproduces key physical features, such as a
d
¯
distribution larger than
u
¯
, that HERA data alone are not able to constrain when using more flexible parametrizations. Moreover, polarized distributions are described in the model by the same parameters of the unpolarized ones, giving us the possibility of extracting both types of distributions within the same fit.
With the ongoing Run 3 of the LHC and its upcoming High-Luminosity upgrade, there is a growing need to study observables with high precision both experimentally and theoretically. To increase ...precision on the theory side, improvements of fixed-order perturbative predictions, resummation of logarithmic enhancements and accurate determination of proton structure are required. This thesis explores the latter two topics. We discuss high-energy logarithms and their resummation techniques, introducing an extension of the HELL formalism for multi-differential distributions in transverse momentum, rapidity and invariant mass. We apply this framework to heavy-quark pair production at the LHC, studying the kinematics of both a single quark and the final-state pair. An additional discussion is dedicated to a possible extension of the kt-factorisation framework, which underlies high-energy resummation, to capture next-to-leading logarithmic corrections. To test this hypothesis, we delve into the computation of a NLO off-shell coefficient function using Higgs-induced DIS in the infinite top mass limit as a benchmark process and report a partial result. Beside high-energy logarithms, we consider the determination of transverse-momentum distributions from a high mass system with additional QCD radiation and exclusive production cuts. Specifically, we focus on \(HW^+\) production with a jet veto and analyse the Higgs transverse momentum spectrum at NNLO, using qt-subtraction. We complement the fixed order study with NNLL resummation of jet-veto logarithms and linear power correction in ptHW using the RadISH formalism. Finally, in the last project pertaining to this thesis we consider the problem of Parton Distribution Function determination. We propose a minimal parametrisation guided by physical arguments and investigate its performance in fitting the HERA dataset with NLO QCD theory predictions.
High-energy logarithmic correction are enhanced when the ratio, $x =
\frac{Q^2}{s}$ between the typical energy scale of a scattering process $Q$ and
the total centre of mass energy available $s$ is ...small. We discuss recent
developments on their resummation in differential cross sections in rapidity,
transverse momentum and invariant mass and their application to heavy flavour
production at the LHC.
We consider the production of a heavy quark pair in proton-proton collisions.
For bottom and charm quarks, the final state invariant mass is typically much
smaller than the collider energy (e.g. at ...the LHC), so that high-energy
logarithms may spoil the perturbativity of the theoretical prediction at fixed
order. The resummation of these logarithms to all orders is thus needed to
obtain reliable predictions. In this work, we extend previous results on
high-energy (or small-$x$) resummation to differential distributions in
rapidity, transverse momentum and invariant mass, and implement them in the
public code HELL.
High-energy logarithmic correction are enhanced when the ratio, \(x = \frac{Q^2}{s}\) between the typical energy scale of a scattering process \(Q\) and the total centre of mass energy available ...\(s\) is small. We discuss recent developments on their resummation in differential cross sections in rapidity, transverse momentum and invariant mass and their application to heavy flavour production at the LHC.
We consider the production of a heavy quark pair in proton-proton collisions. For bottom and charm quarks, the final state invariant mass is typically much smaller than the collider energy (e.g. at ...the LHC), so that high-energy logarithms may spoil the perturbativity of the theoretical prediction at fixed order. The resummation of these logarithms to all orders is thus needed to obtain reliable predictions. In this work, we extend previous results on high-energy (or small-\(x\)) resummation to differential distributions in rapidity, transverse momentum and invariant mass, and implement them in the public code HELL.
We present a determination of the parton distribution functions (PDFs) of the proton from HERA data using a PDF parametrization inspired by a quantum statistical model of the proton dynamics. This ...parametrization is characterised by a very small number of parameters, yet it leads to a reasonably good description of the data, comparable with other parametrizations on the market. It may thus provide an alternative to standard parametrizations, useful for studying parametrization bias and to possibly simplify the fit procedure thanks to the small number of parameters. Interestingly, the model reproduces key physical features, such as a \(\bar d\) distribution larger than \(\bar u\), that HERA data alone are not able to constrain when using more flexible parametrizations. Moreover, polarized distributions are described in the model by the same parameters of the unpolarized ones, opening up the possibility of a simultaneous fit with the same number of parameters. The results of this study can motivate future work in this direction.
Blood contact with surfaces of the extracorporeal circuit provokes the activation of the coagulation system. To improve biocompatibility of the extracorporeal circuit without increasing the risk of ...bleeding, coatings of artificial surfaces were designed; many of them involve the use of heparin. Data in the literature show that heparin‐induced thrombocytopenia is a major issue in the extracorporeal membrane oxygenation scenario, and no relevant benefits have been shown comparing heparin and no‐heparin coating.
Postoperative delirium (POD) is an acute alteration of mental state, characterized by reduced awareness and attention, occurring up to five postoperative days after recovery from anesthesia. Several ...original studies and reviews have identified possible perioperative POD risk factors; however, there is no comprehensive review of the preoperative risk factors in patients diagnosed with POD using only validated diagnostic scales. The aim of this systematic review was to report the preoperative risk factors associated with an increased incidence of POD in patients undergoing non-cardiac and non-brain surgery. The reviewed studies included original research papers that used at least one validated diagnostic scale to identify POD occurrence for more than 24 h. A total of 6475 references were retrieved from the database search, with only 260 of them being suitable for further review. Out of the 260 reviewed studies, only 165 that used a validated POD scale reported one or more preoperative risk factors. Forty-one risk factors were identified, with various levels of statistical significance. The extracted risk factors could serve as a preoperative POD risk assessment workup. Future studies dedicated to the further evaluation of the specific preoperative risk factors' contributions to POD could help with the development of a weighted screening tool.
