QCD fits to ZEUS and fixed target structure function data

Botje, M.

doi:10.1063/1.53606

Cited by 6 publications

(6 citation statements)

References 8 publications

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“…This Markovian MC program has been tested in refs [10]. and[11] against two non-MC programs QCDnum16[21] and APCheb33[22]. Small systematic discrepancy between EvolMC and QCDnum16 for gluon distribution reported in ref [10].…”

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confidence: 99%

Solving constrained Markovian evolution in QCD with the help of the non-Markovian Monte Carlo

Jadach

Skrzypek

2006

Computer Physics Communications

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We present the constrained Monte Carlo (CMC) algorithm for the QCD evolution. The constraint resides in that the total longitudinal energy of the emissions in the MC and in the underlying QCD evolution is predefined (constrained). This CMC implements exactly the full DGLAP evolution of the parton distributions in the hadron with respect to the logarithm of the energy scale. The algorithm of the CMC is referred to as the non-Markovian type. The non-Markovian MC algorithm is defined as the one in which the multiplicity of emissions is chosen randomly as the first variable and not the last one, as in the Markovian MC algorithms. The former case resembles that of the fixed-order matrix element calculations. The CMC algorithm can serve as an alternative to the so-called backward evolution Markovian algorithm of Sjöstrand, which is used for modelling the initial-state parton shower in modern QCD MC event generators. We test practical feasibility and efficiency of our CMC implementation in a series of numerical exercises, comparing its results with those from other MC and non-MC programs, in a wide range of Q and x, down to the 0.1% precision level. In particular, satisfactory numerical agreement is found with the results of the Markovian MC program of our own and the other non-MC program. The efficiency of the new constrained MC is found to be quite good.

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confidence: 99%

Solving constrained Markovian evolution in QCD with the help of the non-Markovian Monte Carlo

Jadach

Skrzypek

2006

Computer Physics Communications

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“…The success of fixed-order perturbative QCD in describing the increasingly precise HERA F 2 data when Q 2 1 GeV 2 has been confirmed many times by successful NLO fits [24]. From these a gluon distribution may be extracted, (see figure 3(a)), and predictions for F c 2 (figure 3(b)), dijet production, and F L , all of which have now been supported by direct measurements [25].…”

Section: Qcd: Resummation Of Logs Of Qmentioning

confidence: 74%

The challenge of smallx

Ball

Landshoff²

2000

J. Phys. G: Nucl. Part. Phys.

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“…The statistical and systematic experimental errors are added in quadrature. We use the qcdnum program [15] to perform the NLO DGLAP evolution and the minuit program [16] to find the optimal parameters. The values of α S (M 2 Z ) and the charm and bottom quark masses are taken to be the same as in the MRST2001 NLO parton set [17].…”

Section: (A)mentioning

confidence: 99%

A QCD analysis of diffractive deep-inelastic scattering data

2004

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We perform a novel type of analysis of diffractive deep-inelastic scattering data, in which the input parton distributions of the Pomeron are parameterised using the perturbative QCD expressions. In particular, we treat individually the components of the Pomeron of different size. We are able to describe simultaneously both the recent ZEUS and H1 diffractive data. In addition to the usual two-gluon model for the perturbative Pomeron, we allow for the possibility that it may be made from two sea quarks.A notable feature of deep-inelastic scattering is the existence of diffractive events, γ * p → Xp, in which the slightly deflected proton and the cluster X of outgoing hadrons are well-separated in rapidity. The large rapidity gap is believed to be associated with Pomeron exchange. The diffractive events make up an appreciable fraction of all (inclusive) deep-inelastic events, γ * p → X. We will refer to the diffractive and inclusive processes as DDIS and DIS respectively.Here we perform a perturbative QCD analysis of the new high precision DDIS data, recently obtained by the ZEUS [1, 2] and H1 [3] Collaborations at HERA. The analysis is novel in that it treats individually the components of the Pomeron of different transverse size. The description of the DDIS data is based on a purely perturbative QCD framework. We take input forms of the parton distributions of the Pomeron given by the calculation of the lowest-order QCD diagrams for γ * p → Xp [4]. In previous analyses, the Pomeron was treated as a hadron-like object of more or less fixed size. However, the microscopic structure of the Pomeron is different to that of a hadron. In perturbative QCD, it is known that the Pomeron singularity is not an isolated pole, but a branch cut, in the complex angular momentum plane [5]. The pole singularity corresponds to a single particle, whereas a branch cut may be regarded as a continuum series of poles. That is, the Pomeron wave function consists of a continuous number of components. Each component i has its own size, 1/µ i . The QCD DGLAP evolution of a component should start from its own scale µ i , provided that µ i is large enough for the perturbative evolution to be valid. Therefore, the expression for the diffractive structure function F D 2 contains an integral

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QCD fits to ZEUS and fixed target structure function data

Cited by 6 publications

References 8 publications

Solving constrained Markovian evolution in QCD with the help of the non-Markovian Monte Carlo

Solving constrained Markovian evolution in QCD with the help of the non-Markovian Monte Carlo

The challenge of smallx

A QCD analysis of diffractive deep-inelastic scattering data

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