475 research outputs found

    Tvorba teŇ°kih kvarkova u HERI

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    Recent measurements of the charm and beauty production in ep collisions at HERA are presented. Heavy-quark tagging methods used by the ZEUS and H1 experiments are described. Cross section results are compared with NLO QCD predictions and in general the data are well described by the calculations. A determination of the charm and beauty contributions to the proton structure function is also presented. The comparison with NLO QCD predictions shows reasonable agreement. A comparison of the result on the beauty contribution to the structure function with a NNLO calculation is also shown, although the errors are currently too large to discriminate between theories.Predstavljamo nedavna mjerenja tvorbe kvarkova Ň°arma i ljepote u ep sudarima u HERI. Opisujemo metode oznańćavanja teŇ°kih kvarkova koje se primjenjuju u mjerenjima ZEUS i H1. Ishodi za udarne presjeke usporeńĎuju se s predvińĎanjima NLO QCD, a eksperimentalni i teorijski podaci su u dobrom skladu. Predstavljamo takońĎer odreńĎivanje doprinosa Ň°arma i ljepote protonskoj strukturnoj funkciji. Usporedba s predvińĎanjima NLO QCD pokazuje dobro slaganje. Dajemo i usporedbu ishoda za doprinos ljepote strukturnoj funkciji s rańćunima NNLO, iako su sada pogreŇ°ke prevelike da bi se razlikovale teorije

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Search for dark matter produced in association with bottom or top quarks in ‚ąös = 13 TeV pp collisions with the ATLAS detector