Search results for "Chromodynamics"
showing 10 items of 1030 documents
Results from bottomonia production at the Tevatron and prospects for the LHC
2000
We extend our previous analysis on inclusive heavy quarkonia hadroproduction to the whole Upsilon(nS) (n=1,2,3) resonance family. We use a Monte Carlo framework with the colour-octet mechanism implemented in the PYTHIA event generator. We include in our study higher order QCD effects such as initial-state emission of gluons and Altarelli-Parisi evolution of final-state gluons. We extract some NRQCD colour-octet matrix elements relevant for Upsilon(nS) (n=1,2,3) hadroproduction from CDF data at the Fermilab Tevatron. Then we extrapolate to LHC energies to predict prompt bottomonia production rates. Finally, we examine the prospect to probe the gluon density in protons from heavy quarkonia in…
Neutral pion and η meson production in proton–proton collisions at s=0.9 TeV and s=7 TeV
2012
The first measurements of the invariant differential cross sections of inclusive pi(0) and eta meson production at mid-rapidity in proton-proton collisions root s = 0.9 TeV and root s = 7 TeV are reported. The pi(0) measurement covers the ranges 0.4 < p(T) < 7 GeV/c and 0.3 < p(T) < 25 GeV/c for these two energies, respectively. The production of eta mesons was measured at root s = 7 TeV in the range 0.4 < p(T) < 15 GeV/c. Next-to-Leading Order perturbative QCD calculations, which are consistent with the pi(0) spectrum at root s = 0.9 TeV, overestimate those of pi(0) and eta mesons at root s = 7 TeV, but agree with the measured eta/pi(0) ratio at root s = 7 TeV. (C) 2012 CERN. Published by …
Measurement of angular correlations in Drell–Yan lepton pairs to probe Z/γ⁎ boson transverse momentum at s=7 TeV with the ATLAS detector
2013
A measurement of angular correlations in Drell-Yan lepton pairs via the phi(eta)* observable is presented. This variable probes the same physics as the Z/gamma* boson transverse momentum with a better experimental resolution. The Z/gamma* -> e(+)e(-) and Z/gamma* -> mu(+)mu(-) decays produced in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV are used. The data were collected with the ATLAS detector at the LHC and correspond to an integrated luminosity of 4.6 fb(-1). Normalised differential cross sections as a function of phi(eta)* are measured separately for electron and muon decay channels. These channels are then combined for improved accuracy. The cross section is …
Transverse energy from minijets in ultrarelativistic nuclear collisions: a next-to-leading order analysis
2000
We compute in next-to-leading order (NLO) perturbative QCD the amount of transverse energy produced into a rapidity region $\Delta Y$ of a nuclear collision from partons created in the few-GeV subcollisions. The NLO formulation assumes collinear factorization and is based on the subtraction method. We first study the results as a function of the minimum transverse momentum scale and define and determine the associated $K$-factors. The dependence of the NLO results on the scale choice and on the size of $\Delta Y$ is also studied. The calculations are performed for GRV94 and CTEQ5 sets of parton distributions. Also the effect of nuclear shadowing to the NLO results is investigated. The main …
Forward J / ψ and D meson nuclear suppression at the LHC
2017
Abstract Using the color glass condensate formalism, we study the nuclear modification of forward J/ψ and D meson production in high energy proton-nucleus collisions at the LHC. We show that relying on the optical Glauber model to obtain the dipole cross section of the nucleus from the one of the proton fitted to HERA DIS data leads to a smaller nuclear suppression than in the first study of these processes in this formalism and a better agreement with experimental data.
Precise determination of α(M) from global fits of e+e− data to NNLO+NNLL predictions
2018
Abstract We present a comparison of the computation of energy-energy correlations and Durham algorithm jet rates in e + e − collisions at next-to-next-to-leading logarithmic accuracy matched with the next-to-next-to-leading order perturbative prediction to LEP, PEP, PETRA, SLC and TRISTAN data. With these predictions we perform global extractions of the strong coupling constant taking into account non-perturbative effects modelled with modern Monte Carlo event generators that simulate NLO QCD corrections.
Physics at MAMI C
2005
The physics motivation for the energy increase of the Mainz Microtron from 885 to 1500 MeV (MAMI C) is presented. It is argued that the low energy regime in hadron physics where the perturbative approach to QCD is not applicable is the most relevant to further understand this peculiar theory. However, the investigation of the most significant observables needs excellent experimental precision and an intensive interaction with theory. As examples the recent measurement of the form factor of the neutron and the pion polarisability are presented. They show that the mentioned conditions are given at MAMI and will be extended by the energy increase.
Finite Energy Sum Rules with Legendre Polynomial Kernels
2016
Abstract In this note we report about a method to deal with finite energy sum rules. With a reasonable knowledge of the main resonances of the spectrum, the method guarantees that we can find a nice duality matching between the low energy hadronic data and asymptotic QCD at high energies.
The large $$N_{c}$$ limit of QCD on the lattice
2021
We review recent progress in the study of the large $N_c$ limit of gauge theories from lattice simulations. The focus is not only the planar limit but also the size of ${\mathcal O}(N_c^{-1})$ corrections for values of $N_c\gtrsim 3$. Some concrete examples of the topics we include are tests of large-$N_c$ factorization, the topological susceptibility, the glueball, meson and baryon spectra, the chiral dependence of masses and decay constants, and weak matrix elements related to the $\Delta I=1/2$ rule in kaon decays.
Search for γγ→ηb in e+e− collisions at LEP 2
2002
A search for the pseudoscalar meson eta_b is performed in two-photon interactions at LEP~2 with an integrated luminosity of 699 pb^-1 collected at e+e- centre-of-mass energies from 181 GeV to 209 GeV. One candidate event is found in the six-charged-particle final state and none in the four-charged-particle final state, in agreement with the total expected background of about one event. Upper limits of Gamma_gammagamma(eta_b) * BR(eta_b -> 4 charged particles) 6 charged particles) < 132 eV are obtained at 95% confidence level, which correspond to 95% confidence level upper limits of 9.0% and 25% on these branching ratios.