A critical appraisal and evaluation of modern PDFs

Accardi, Alberto; Alekhin, S.; Blümlein, J.; Garzelli, Maria Vittoria; Lipka, K.; Melnitchouk, Wally; Moch, S.; Owens, J. F.; Plačakytė, R.; Reya, E.; Sato, Nobuo; Vogt, A.; Zenaiev, O.

doi:10.1140/epjc/s10052-016-4285-4

Cited by 132 publications

(150 citation statements)

References 348 publications

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“…At the present time several groups determine PDFs (for latest results see, e.g. [1,[236][237][238][239][240][241], and for a recent review see [242,243]). In Fig.…”

Section: Introductionmentioning

confidence: 99%

Charm production and QCD analysis at HERA and LHC

Zenaiev

2017

Eur. Phys. J. C

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This review is devoted to the study of charm production in ep and pp collisions. The total set of measurements obtained by the two collaborations H1 and ZEUS from HERA and their combination is outlined, as well as complementary data obtained by the LHCb Collaboration at the LHC. After fitting the parton distribution functions the charm-production cross sections are predicted within perturbative QCD at next-to-leading order using the fixed-flavournumber scheme. Agreement with the data is found. The combined HERA charm data are sensitive to the c-quark mass and enabled its accurate determination. The predictions crucially depend upon the knowledge of the gluon distribution function. It is shown that the shape of the gluon distribution based on the HERA data is considerably improved by adding the measurements from LHCb and applicable down to values x of about 10 −6 , where x is the proton momentum fraction carried by a parton.

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“…At the present time several groups determine PDFs (for latest results see, e.g. [1,[236][237][238][239][240][241], and for a recent review see [242,243]). In Fig.…”

Section: Introductionmentioning

confidence: 99%

Charm production and QCD analysis at HERA and LHC

Zenaiev

2017

Eur. Phys. J. C

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“…PDFs collaborations constantly improve their fitting in order to reduce this error, by including high precision data from HERA and Fermilab [1,2]. In the large-x regime PDFs uncertainties have been sensibly reduced, allowing precise predictions at higher energy scales where we expect new physics to appear.…”

Section: The Lhc As Photon Collidermentioning

confidence: 99%

Photon-initiated production of a di-lepton final state at the LHC: cross section versus forward-backward asymmetry studies

Fiaschi¹,

Hautmann²,

Moretti³

et al. 2017

Proceedings of 38th International Conference on High Energy Physics — PoS(ICHEP2016)

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We discuss the effect of the Photon Initiated (PI) process on the dilepton channel at the LHC. Adopting various QED PDF sets, we evaluate the contribution produced by two resolved photons which is not included in the Equivalent Photon Approximation (EPA). We compare the PI central value as predicted by the CTEQ, MRST and NNPDF collaborations. With the NNPDF2.3QED set of replicas we also estimate the PDF uncertainties on the PI central value. We show the effect of the inclusion of the PI contribution and its PDF uncertainties on neutral heavy Z -boson searches. We explore the two scenarios of narrow and broad resonances, including in the analysis the reconstructed Forward-Backward Asymmetry observable, the latter being less affected by systematics effects.

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“…Most of these differences have been addressed by benchmark exercises to assess the true differences in the methodologies of the groups [20,21]. The level of precision for these benchmarked PDFs (based on General-Mass-Variable-Flavour-Number-Schemes) reaches below 10% in the bulk x region of 10 −3 − 10 −1 , however, outside this region, the level of uncertainties escalate considerably, as shown in figure 3 for the gluon distribution.…”

Section: Current Pdf Groupsmentioning

confidence: 99%

Parton Distribution Functions and the role of forward region data

Radescu

2017

EPJ Web Conf.

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Abstract. In the era of searching for new discoveries at the LHC, it is crucial to achieve a higher level of precision in understanding the proton structure which will allow for unambiguous interpretations of the high energy, luminous data ahead. The knowledge of proton's constituents comes mainly from the deep inelastic scattering data at HERA, complemented by the measurements from the fixed target, Tevatron, and now increasingly precise more data from LHC. A road-map that marks the most recent developments from the past and present experiments sensitive to the proton constituents will be presented here with an emphasis on the recent results using LHC data from the forward region. MotivationIt is a most exciting phase of particle physics where there are many crucial questions which point to the deficiencies of the Standard Model (SM) that need to be answered. These questions can be addressed by the long term plan of the LHC running in different stages for achieving ever higher energies and luminosity. This poses new challenges for the experimental set-up and for the understanding of quark-gluon dynamics of the incoming proton beam particles at the LHC in the search for new particles or new interaction effects. The goal is first to facilitate the discovery of new physics by comparing measurements with the expectations driven either by the current SM hypothesis or by testing various beyond-SM scenarios. Precision is crucial to control the dominant uncertainties in order to observe and later analyse possible deviations from expectations. On the experimental side, the current measurements are now available at sub percent precision (e.g. W, Z at 7 TeV, Z p T at 8 TeV), while the last decade has seen an enormous progress in achieving percent level precision on the theory calculations. Many of these are now available up to the next-to-next-to leading order (NNLO) in the truncated perturbative series of the strong coupling. In the following, an overview of the progress on improving the current limiting factor on precision, which arises from the limited knowledge of the proton's constituents, is presented. Parton Distribution FunctionsProton's Parton Distribution Functions (PDFs) are understood, at the leading order approximation in QCD, as the probability of finding a parton of a given flavour that carries a fraction x of the total proton's momentum. Once QCD corrections are included, PDFs become scheme dependent. Their shape and normalisation are very different for each flavour, reflecting the different underlying dynamics that a

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A critical appraisal and evaluation of modern PDFs

Cited by 132 publications

References 348 publications

Charm production and QCD analysis at HERA and LHC

Charm production and QCD analysis at HERA and LHC

Photon-initiated production of a di-lepton final state at the LHC: cross section versus forward-backward asymmetry studies

Parton Distribution Functions and the role of forward region data

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