Search results for "parto"
showing 10 items of 608 documents
Poopćene raspodjele partona i struktura sastavnog kvarka
2003
In a scenario where the constituent quarks are composite systems, generalized parton distributions (GPDs) are built from wave functions to be evaluated in a constituent quark model (CQM), convoluted with the GPDs of the constituent quarks themselves. The approach permits to access the full kinematical range corresponding to the DGLAP and ERBL regions, so that cross-sections for deeply virtual Compton scattering can be estimated.
Measurement of azimuthal asymmetries associated with deeply virtual Compton scattering on a longitudinally polarized deuterium target
2010
Azimuthal asymmetries in exclusive electroproduction of a real photon from a longitudinally polarized deuterium target are measured with respect to target polarization alone and with respect to target polarization combined with beam helicity and/or beam charge. The asymmetries appear in the distribution of the real photons in the azimuthal angle $\phi$ around the virtual photon direction, relative to the lepton scattering plane. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe-Heitler process. The results for the beam-charge and beam-helicity asymmetries from a tensor polarized deuterium target with vanishing vector polarization ar…
Multiplicity fluctuations in hadronic final states from the decay of the Z0
1992
An analysis of the fluctuations in the phase space distribution of hadrons produced in the decay of 78829 Z0 has been carried out, using the method of factorial moments. The high statistics collected by the DELPHI experiment at LEP during 1990 allowed studies of the event sample both globally and in intervals of p(t) and multiplicity, and for different jet topologies and for single jets. A large contribution to the factorial moments of the one-dimensional data on rapidity with respect to the event axis comes from hard gluons. Details of factorial moments in two and three dimensions are presented. Influences of resonance decays have been studied by Monte Carlo simulation: one-dimensional fac…
Jet energy scale determination in the D0 experiment
2013
The calibration of jet energy measured in the \DZero detector is presented, based on ppbar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with photon+jet, Z+jet and dijet{} events, with jet transverse momentum pT > 6 GeV and pseudorapidity range |eta| < 3.6. The corrections are measured separately for data and simulation, achieving a precision of 1.4%-1.8% for jets in the central part of the calorimeter and up to 3.5% for the jets with pseudorapidity…
The pion transition form factor and the pion distribution amplitude
2010
Recent BaBar data on the pion transition form factor, whose Q(2)-dependence is much steeper then predicted by asymptotic Quantum Chromodynamics (QCD), have caused a renewed interest in its theoretical description. We present here a formalism based on a model-independent description for low photon virtuality and a high photon virtuality description based on QCD, which match at a scale Q(0). The high photon virtuality description incorporates a flat pion distribution amplitude, phi(x) = 1, at the matching scale Q(0) and QCD evolution from Q(0) to Q > Q(0). The flat pion distribution is connected, through soft pion theorems and chiral symmetry, to the pion valence parton distribution at the sa…
Energy dependence of inclusive spectra in e+ e- annihilation
1999
Inclusive charged hadron distributions as obtained from the DELPHI measurements at 130, 136, 161, 172 and 183 GeV are presented as a function of the variables rapidity, xi(p), p and transversal momenta. Data are compared with event generators and with MLLA calculations, in order to examine the hypothesis of local parton hadron duality. The differential momentum spectra show an indication for coherence effects in the production of soft particles. The relation between the energy dependence of the charged multiplicity and the rapidity distribution is examined. (C) 1999 Elsevier Science B.V. All rights reserved.
Evaluating the double parton scattering contribution to Mueller-Navelet jets production at the LHC
2015
We propose a model to study the importance of double parton scattering (DPS) in Mueller-Navelet jets production at the LHC which is consistent with the BFKL framework used to compute the single parton scattering contribution to this process. We study this model in kinematics corresponding to existing and possible future measurements at the LHC and estimate the importance of this DPS contribution on relevant observables for this process, namely the cross section and the azimuthal correlation of the jets.
A QCD analysis of LHCb D-meson data in p plus Pb collisions
2020
We scrutinize the recent LHCb data for D$^0$-meson production in p+Pb collisions within a next-to-leading order QCD framework. Our calculations are performed in the SACOT-$m_{\rm T}$ variant of the general-mass variable-flavour-number scheme (GM-VFNS), which has previously been shown to provide a realistic description of the LHC p+p data. Using the EPPS16 and nCTEQ15 nuclear parton distribution functions (PDFs) we show that a very good agreement is obtained also in the p+Pb case both for cross sections and nuclear modification ratios in the wide rapidity range covered by the LHCb data. Encouraged by the good correspondence, we quantify the impact of these data on the nuclear PDFs by the Hes…
Revisiting the D-meson hadroproduction in general-mass variable flavour number scheme
2018
We introduce a novel realization of the open heavy-flavour hadroproduction in general-mass variable flavour number scheme at next-to-leading order in perturbative QCD. The principal novelty with respect to the earlier works is in the treatment of small-transverse-momentum limit, which has been a particularly challenging kinematic region in the past. We show that by a suitable choice of scheme, it is possible to obtain a well-behaved description of the open heavy-flavour hadroproduction cross sections from zero up to asymptotically high transverse momentum. We contrast our calculation with the available D$^0$-meson data as measured by the LHCb and ALICE collaborations at the LHC, finding a v…
A study of intermittency in Hadronic Z$^0$ Decays
1990
The correlations in rapidity in hadron production from e+e- annihilation near the Z0 resonance were studied by means of the method of factorial moments, using data taken with the DELPHI detector at LEP. The parton shower hadronization model was found to be in quantitative agreement with the data, in contrast with previous results at lower energies. © 1990.