Search results for "GLUON"
showing 10 items of 697 documents
Total and inelastic cross sections at LHC ats=7 TeVand beyond
2011
We discuss expectations for the total and inelastic cross sections at LHC CM energies $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ and 14 TeV obtained in an eikonal minijet model augmented by soft gluon ${k}_{t}$-resummation, which we describe in some detail. We present a band of predictions which encompass recent LHC data and suggest that the inelastic cross section described by two-channel eikonal models include only uncorrelated processes. We show that this interpretation of the model is supported by the LHC data.
The COMPASS experiment at CERN
1998
Abstract The recently approved COMPASS experiment attempts a measurement of the gluon polarization around η ⋍ 0.1 with a precision of δ(Δ g / g ) ⋍ 0.1. The experiment uses open charm muo-production and large PT hadron pairs to tag the photon-gluon fusion process. COMPASS will also cover a rich spin-physics program in polarized DIS.
Low-mass dileptons at high momenta in ultra-relativistic heavy-ion collisions
1992
Abstract We calculate the emission rate of low-mass dileptons at high momenta from a quark-gluon plasma. We find a large enhancement compared with the naive Born rate. Numerical estimates for relativistic heavy ions collisions at RHIC and LHC suggest, however, that the thermal signal is dominated by the background coming from meson decays and from hadronic bremsstrahlung.
New measurements of at COMPASS
2007
One of the main goals of the COMPASS experiment at CERN is the determination of the gluon polarisation in the nucleon, Δ G / G . It is determined from spin asymmetries in the scattering of polarised muons at 160 GeV/c on a polarised LiD target. The gluon polarisation is accessed by the selection of photon-gluon fusion events. Such events are tagged either with a charmed meson or a hadron pair with high transverse momenta in the final state. The selection of charmed mesons is based on the reconstruction of decayed D ⋆ and D 0 mesons in the COMPASS spectrometer. For the high- p T hadron pairs two independent analyses are performed in the kinematic regimes of DIS ( Q 2 > 1 ( GeV / c ) 2 ) and …
Charmonium Production at Tevatron, HERA and LHC
1998
Charmonia hadro- and photo-production are analyzed in the framework of the color-octet model taking into account higher-order effects induced by initial-state radiation of gluons. We argue that color-octet matrix elements obtained from Tevatron data might be reconciled with those extracted from HERA data on inelastic $J/\psi$ photoproduction. Finally we estimate cross sections for events with muons from prompt $J/\psi$'s as a background for the B physics programme at LHC experiments.
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.
Understanding LHC jets in the light of RHIC data
2012
Hard probes are a cornerstone in the ongoing program to determine the properties of hot and dense QCD matter as created in ultrarelativistic heavy ion collisions. LHC measurements have so far resulted in a wealth of high P_T data, opening new kinematic windows with high statistics. Yet on first glance, several observations are counter-intuitive and seem to contradict results from the RHIC high P_T program. This calls for a combined analysis of high P_T hadrons and reconstructed jets at RHIC and LHC in a unified framework testing a large number of theoretical models for both medium evolution and shower medium interactions against the systematics of the data. A consistent picture of shower-me…
New extraction of color-octet NRQCD matrix elements from charmonium hadroproduction
1999
We re-analyze Tavatron data on charmonium hadroproduction in the framework of the color-octet model implemented in the event generator PYTHIA taking into account initial-state radiation of gluons and Altarelli-Parisi evolution of final-state gluons fragmenting into $c\bar{c}$ pairs. We obtain new values for the color-octet matrix elements relevant to this production process. We discuss the sensitivity of our results to the transverse momentum lower cut-off employed in the generation to avoid the problematic $p_t{\to}0$ region, arguing about the reliability of our previous extraction of the NRQCD matrix elements for the $^3S_1^{(8)}$ and $^1S_0^{(8)}+^3P_J^{(8)}$ contributions. Finally we ex…
D meson enhancement in pp collisions at the LHC due to nonlinear gluon evolution
2004
When nonlinear effects on the gluon evolution are included with constraints from HERA, the gluon distribution in the free proton is enhanced at low momentum fractions, x < 0.01, and low scales, Q^2 < 10 GeV^2, relative to standard, DGLAP-evolved, gluon distributions. Consequently, such gluon distributions can enhance charm production in pp collisions at center of mass energy 14 TeV by up to a factor of five at midrapidity, y \sim 0, and transverse momentum p_T -> 0 in the most optimistic case. We show that most of this enhancement survives hadronization into D mesons. Assuming the same enhancement at leading and next-to-leading order, we show that the D enhancement may be measured …
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.