Istraživanja ep sudara na najvišim Q2 I P_T sudaračem HERA

The HERA collider with its center of mass energy of 318 GeV makes it possible to study a wide range of electroweak physics as well as to search for physics beyond the Standard Model (SM). In this article, recent results, obtained by the two collider experiments H1 and ZEUS, are reviewed. The cross sections for inclusive neutral current and charged current processes are shown, and results from a combined electroweak and QCD analysis of the data are discussed. Selected results from searches for physics beyond the SM are presented.Sudaračem HERA, na energijama u sustavu središta mase od 318 GeV, može se proučavati široko područje elektroslabe fizike, kao i tražiti pojave izvan standardnog modela (SM). Izlažemo pregled nedavnih ishoda dvaju mjerenja sudara, H1 i ZEUS. Prikazujemo udarne presjeke inkluzivnih procesa neutralnih i nabijenih struja, te raspravljamo ishode skupnih elektroslabih i QCD analiza. Predstavljamo i ishode traganja pojava izvan SM-a

Difrakcija i tvorba vektorskih mezona u HERI

Results of new measurements of diffractive cross sections in deep-inelastic scattering (DIS) and photo-production at HERA are presented. The cross sections of dijet and open charm production are compared with next-to-leading order (NLO) QCD predictions based on parton distribution functions obtained from diffractive inclusive DIS data. A combined NLO QCD fit to the inclusive and dijet DIS data is performed to determine diffractive quark singlet and gluon densities with a better precision. Recent measurements of elastic vector meson production and deeply virtual Compton scattering at HERA are also reviewed.Predstavljamo ishode novih mjerenja difrakcijskih udarnih presjeka duboko-neelastičnog raspršenja (DIS) i fototvorbe u HERI. Uspoređujemo udarne presjeke tvorbe dvomlazeva i otvorenog šarma s predviđanjima QCD u prvom redu iza vodećeg (NLO), na osnovi funkcija partonske raspodjele dobivenih iz difrakcijskih inkluzivnih DIS podataka. Proveli smo NLO QCD prilagodbu skupno za inkluzivne i DIS podatke radi određivanja difrakcijskih singletnih kvarkovskih i gluonskih gustoća s većom točnošću. Također dajemo pregled nedavnih mjerenja elastične tvorbe vektorskih mezona i duboko virtualnog Comptonovog raspršenja u HERI

Tvorba teških kvarkova u HERI

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 šarma i ljepote u ep sudarima u HERI. Opisujemo metode označavanja teških kvarkova koje se primjenjuju u mjerenjima ZEUS i H1. Ishodi za udarne presjeke uspoređuju se s predviđanjima NLO QCD, a eksperimentalni i teorijski podaci su u dobrom skladu. Predstavljamo također određivanje doprinosa šarma i ljepote protonskoj strukturnoj funkciji. Usporedba s predviđanjima NLO QCD pokazuje dobro slaganje. Dajemo i usporedbu ishoda za doprinos ljepote strukturnoj funkciji s računima NNLO, iako su sada pogreške prevelike da bi se razlikovale teorije

Mlazovi u proučavanju dinamike za male x

One of the most challenging aspects of low x proton structure is the study of QCD dynamics - the evolution of partons between different kinematic regimes. In electron-proton deep-inelastic scattering, this can be investigated by studying processes in the target region of the proton - forward going jets. In this paper various measurements made at HERA by the H1 and ZEUS experiments are presented and compared to Monte Carlo models and fixed-order QCD calculations.Među najspornijim izazovima protonske strukture za male x je proučavanje QCD dinamike razvoja partona pri prijelazu među različitim kinematičkim uvjetima. To je moguće proučavanjem procesa u području protonske mete u duboko-neelastičnom raspršenju elektrona s protonima preko mlazova pod malim kutom. Predstavljamo više mjerenja suradnje H1 i ZEUS na HERI i uspoređujemo ih s Monte Carlo modelima i QCD računima određenog reda

Razlamanje i tvorba čestica u duboko-neelastičnom raspršenju i fototvorbi

Charged particle production has been studied in deep inelastic scattering with the H1 and ZEUS detectors at HERA. The evolution of scaled momentum distribution with respect to Q2 is shown in the current fragmentation region of the Breit frame in the range from 10 to 40000 GeV2. Characteristics of the produced particle are presented for (anti)deuteron, (anti)protons, kaon pair production as well as (anti)lambda and K0.Istraživali smo tvorbu nabijenih čestica u duboko-neelastičnom raspršenju s detektorima H1 i ZEUS kod HERA-e. Pokazujemo razvoj sumjerne impulsne raspodjele u ovisnosti o Q2 u području strujnog razlamanja u Breitovom sustavu u području od 10 do 40000 GeV2 . Predstavljaju se značajke ovih proizvedenih čestica: (anti)deuterona, (anti)protona, parova kaona, (anti)lambda i K0

Impact of jet-production data on the next-to-next-to-leading-order determination of HERAPDF2.0 parton distributions

The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive deep inelastic ep scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of αs(M2Z) and the PDFs, was performed with the result αs(M2Z)=0.1156±0.0011 (exp) +0.0001−0.0002 (model +parameterisation) ±0.0029 (scale). The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of αs(M2Z), αs(M2Z)=0.1155 and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input

Electroweak Physics at LHC

The prospects for electroweak physics at the LHC are reviewed focusing mainly on precision studies. This includes projections for measurements of the effective Z pole weak mixing angle, of top quark, W boson, and Higgs scalar properties, and new physics searches