Search results for "PARTON"
showing 10 items of 552 documents
Multiplicities and Transverse Energies in Central AA Collisions at RHIC and LHC from pQCD, Saturation and Hydrodynamics
2001
We compute the particle multiplicities and transverse energies at central and nearly central AA collisions at RHIC and LHC. The initial state is computed from perturbative QCD supplemented by the conjecture of saturation of produced partons. The expansion stage is described in terms of hydrodynamics assuming longitudinal boost invariance and azimuthal symmetry. Transverse flow effects, a realistic list of hadrons and resonance decays are included. Comparison with the data of the multiplicities at $\sqrt s=56$ AGeV and 130 AGeV from RHIC is done and predictions for the full RHIC energy and LHC energy are made for the multiplicities and transverse energies. The reduction from the initially re…
A perturbative QCD analysis of charged-particle distributions in hadronic and nuclear collisions
2002
We compute the distributions of charged particles at large transverse momenta in $p\bar p(p)$, $pA$ and $AA$ collisions in the framework of perturbative QCD, by using collinear factorization and the modern PDFs and fragmentation functions. At the highest cms-energies the shape of the spectra measured in $p\bar p(p)$ collisions at large $q_T$ can be well explained. The difference between the data and the lowest-order computation is quantified in terms of a constant $K$-factor for each energy. The $K$-factor is found to systematically decrease with growing $\sqrt s$. Also a lower limit for the partonic transverse momentum, $p_0$, is extracted for each $\sqrt s$ based on the comparison with th…
Minijet and transverse energy production in the BFKL regime
1996
Minijet production in hadronic and nuclear collisions through a BFKL pomeron ladder is studied for the energies of the future LHC heavy-ion collisions. We use unintegrated gluon densities compatible with the small-$x$ increase of parton distributions observed at HERA. We show that at LHC energies the BFKL minijet and transverse energy production is at most of the same order of magnitude as that in the collinear factorization approach.
The fragility of high- hadron spectra as a hard probe
2004
We study the suppression of high-pT hadron spectra in nuclear collisions, supplementing the perturbative QCD factorized formalism with radiative parton energy loss. We find that the nuclear modification factor which quantifies the degree of suppression, is almost pT-independent both for RHIC (in agreement with data) and for the LHC. This is a consequence of the shape of the partonic pT-spectrum in elementary collisions which implies that for the same value of the nuclear modification factor at higher pT, an increasingly smaller fraction of parton energy loss is needed. When the values of the time-averaged transport coefficient exceed 5 GeV^2/fm, the nuclear modification factor gradually los…
Prospects of searching for (un)particles from Hidden Sectors using rapidity correlations in multiparticle production at the LHC
2008
Most signatures of new physics have been studied on the transverse plane with respect to the beam direction at the LHC where background is much reduced. In this paper we propose the analysis of inclusive longitudinal (pseudo) rapidity correlations among final-state (charged) particles in order to search for (un)particles belonging to a hidden sector beyond the Standard Model, using a selected sample of p-p minimum bias events (applying appropriate off-line cuts on events based on, e.g. minijets, high-multiplicity, event shape variables, high-p(perpendicular to) leptons and photons, etc.) collected at the early running of the LHC. To this aim, we examine inclusive and semi-inclusive two-part…
Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction
2001
We examine carefully bottomonia hadroproduction in proton colliders, especially focusing on the LHC, as a way of probing the gluon density in protons. To this end we develop some previous work, getting quantitative predictions and concluding that our proposal can be useful to perform consistency checks of the parameterization sets of different parton distribution functions.
Hard dihadron correlations in heavy-ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider
2011
High transverse momentum (${P}_{T}$) processes are considered to be an important tool to probe and understand the medium produced in ultrarelativistic heavy-ion collisions via the interaction of hard, perturbatively produced partons with the medium. In this context, triggered hard dihadron correlations constitute a class of observables set between hard single inclusive hadrons (dominated by the leading jet fragments) and fully reconstructed jets; while they probe some features of the perturbative QCD evolution of a parton shower in the medium, they do not suffer from the problem of finding a suitable separation between soft hadrons coming from perturbative jets and soft hadrons coming from …
Re-weighting at the LHC: the p–Pb data impact
2016
Abstract In this work we present selected results of a comprehensive analysis of the medium modifications in proton-lead LHC Run I data, and discuss the implications on different sets of nuclear parton densities. We find that the nuclear environment has a non-negligible relevance on the experimental results. We incorporate the information from Run I into the current nuclear densities and provide novel sets of nPDFs that will be useful for future predictions.
Measurement of the differential γ+c-jet cross section and the ratio of differential γ+c and γ+b cross sections in pp¯ collisions at s=1.96 TeV
2013
We present measurements of the differential cross section $d\sigma/dp_{T}^{\gamma}$ for the associated production of a $c$-quark jet and an isolated photon with rapidity $|y^{\gamma}| 15$ GeV. The cross section ratios $\sigma(\gamma+c)/\sigma(\gamma+b)$ as a function of $p_{T}^{\gamma}$ are also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=$1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the $k_{T}$-factorization approach, and to pr…
Double parton interactions inγ+3jet events inpp¯collisions ats=1.96 TeV
2010
We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single ppbar collision at sqrt{s}=1.96 TeV. The DP fraction and effective cross section (sigma_eff), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in pT) jet transverse momentum pT_jet2 within the range 15 < pT_jet2 < 30 GeV. In this range, f_DP varies between 0.23 < f_DP < 0.47, while sigma_eff has the average value sigma_eff_ave = 16.4 +- 0.3(stat) +- 2.3(syst) mb.