Search results for "Fermi"
showing 10 items of 1388 documents
Measurement of Inclusive Jet Cross Sections inZ/γ*(→e+e−)+jetsProduction inpp¯Collisions ats=1.96 TeV
2008
Inclusive jet cross sections in Z/{gamma}* events, with Z/{gamma}* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in p{bar p} collisions at {radical}s - 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 1.7 fb{sup -1}. The measurements cover the rapidity region |y{sup jet}| 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.
Alternative large-n limit for QCD and its implications for low-energy nuclear phenomena
1990
The Corrigan-Ramond model for large-{ital N} QCD is analyzed in detail. The spectrum, leading-order results for interactions, and an effective Lagrangian describing large-{ital N} interactions are derived. This Lagrangian, when quantized, provides an effective quantum field theory for mesons and baryons. The applicability of such a theory to low-energy nuclear phenomena is studied. The model has features that distinguish it clearly from standard large-{ital N} QCD.
Review of Lattice QCD Studies of Hadronic Vacuum Polarization Contribution to Muon g-2
2019
Lattice QCD (LQCD) studies for the hadron vacuum polarization (HVP) and its contribution to the muon anomalous magnetic moment (muon g-2) are reviewed. There currently exists more than 3-sigma deviations in the muon g-2 between the BNL experiment with 0.5 ppm precision and the Standard Model (SM) predictions, where the latter relies on the QCD dispersion relation for the HVP. The LQCD provides an independent crosscheck of the dispersive approaches and important indications for assessing the SM prediction with measurements at ongoing/forthcoming experiments at Fermilab/J-PARC (0.14/0.1 ppm precision). The LQCD has made significant progress, in particular, in the long distance and finite volu…
QCD running in neutrinoless double beta decay: Short-range mechanisms
2016
16 pages.- 3 figures.- 2 tables
Excited state systematics in extracting nucleon electromagnetic form factors
2012
We present updated preliminary results for the nucleon electromagnetic form factors for non-perturbatively $\mathcal{O}(a)$ improved Wilson fermions in $N_f=2$ QCD measured on the CLS ensembles. The use of the summed operator insertion method allows us to suppress the influence of excited states in our measurements. A study of the effect that excited state contaminations have on the $Q^2$ dependence of the extracted nucleon form factors may then be made through comparisons of the summation method to standard plateau fits, as well as to excited state fits.
Ratio of Isolated Photon Cross Sections in pp¯ Collisions at √s=630 and 1800 GeV
2001
The inclusive cross section for production of isolated photons has been measured in p (p) over bar collisions at roots = 630 GeV with the DO detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E-T) range from 7-49 GeV and have pseudorapidity \eta\ s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E-T range.
Charge asymmetry of heavy quarks at hadron colliders
1998
A sizeable difference in the differential production cross section of top and antitop quarks, respectively, is predicted for hadronically produced heavy quarks. It is of order $\alpha_s$ and arises from the interference between charge odd and even amplitudes respectively. For the TEVATRON it amounts up to 15\% for the differential distribution in suitable chosen kinematical regions. The resulting integrated forward-backward asymmetry of 4--5\% could be measured in the next round of experiments. At the LHC the asymmetry can be studied by selecting appropriately chosen kinematical regions. Furthermore, a slight preference at LHC for centrally produced antitop is predicted, with top quarks mor…
Measurement of spin correlation in tt¯ production using dilepton final states
2011
We measure the correlation between the spin of the top quark and the spin of the anti-top quark in (ttbar -> W+ W- b bbar -> l+ nu b l- nubar bbar) final states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96 TeV, where l is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and tbar rest frames, yielding a correlation strength C= 0.10^{+0.45}_{-0.45}, in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
Nucleon average quark momentum fraction with Nf = 2+1 Wilson fermions
2018
We report on an analysis of the average quark momentum fraction of the nucleon and related quantities using Nf = 2 + 1 Wilson fermions. Computations are performed on four CLS ensembles covering three values of the lattice spacing at pion masses down to Mπ ≈ 200 MeV. Several source-sink separations (~ 1:0 fm to ~ 1:4 fm) are used to assess the excited-state contamination. To gain further insight, the generalized pencil-of-functions approach has been implemented to reduce the excited-state contamination in the relevant two-and three-point functions. Preliminary results are shown for the isovector nucleon charges from vector, axial vector and tensor derivative (twist-2) operators.
Quantum Thermodynamic Perturbation Theory for Fermions
1993
The quantum version of classical thermodynamic perturbation theory is applied to the ground state of a fluid of spin-1/2 fermions interacting via the Aziz interatomic potential, as a model for liquid 3He. Results from the rapidly-convergent sixth-order calculation about the unperturbed hard-sphere fluid for energy, density and sound velocity at the zero-pressure liquid equilibrium point, lie within a few percent of computer-simulation values and appreciably closer than the most elaborate recent variational calculation. The procedure explicitly avoids crossing phase boundaries and is relatively insensitive to varying the close-packing density up to a value somewhat below the maximum possible…