Search results for "Reno"
showing 10 items of 1031 documents
Chiral sum rules and duality in QCD
1998
The ALEPH data on the vector and axial-vector spectral functions, extracted from tau-lepton decays is used in order to test local and global duality, as well as a set of four QCD chiral sum rules. These are the Das-Mathur-Okubo sum rule, the first and second Weinberg sum rules, and a relation for the electromagnetic pion mass difference. We find these sum rules to be poorly saturated, even when the upper limit in the dispersion integrals is as high as $3 GeV^{2}$. Since perturbative QCD, plus condensates, is expected to be valid for $|q^{2}| \geq \cal{O}$$(1 GeV^{2})$ in the whole complex energy plane, except in the vicinity of the right hand cut, we propose a modified set of sum rules with…
Renormalization group evolution of multi-gluon correlators in high energy QCD
2011
Many-body QCD in leading high energy Regge asymptotics is described by the Balitsky-JIMWLK hierarchy of renormalization group equations for the x evolution of multi-point Wilson line correlators. These correlators are universal and ubiquitous in final states in deeply inelastic scattering and hadronic collisions. For instance, recently measured di-hadron correlations at forward rapidity in deuteron-gold collisions at the Relativistic Heavy Ion Collider (RHIC) are sensitive to four and six point correlators of Wilson lines in the small x color fields of the dense nuclear target. We evaluate these correlators numerically by solving the functional Langevin equation that describes the Balitsky-…
anQCD: Fortran programs for couplings at complex momenta in various analytic QCD models
2015
We provide three Fortran programs which evaluate the QCD analytic (holomorphic) couplings $\mathcal{A}_{\nu}(Q^2)$ for complex or real squared momenta $Q^2$. These couplings are holomorphic analogs of the powers $a(Q^2)^{\nu}$ of the underlying perturbative QCD (pQCD) coupling $a(Q^2) \equiv \alpha_s(Q^2)/\pi$, in three analytic QCD models (anQCD): Fractional Analytic Perturbation Theory (FAPT), Two-delta analytic QCD (2$\delta$anQCD), and Massive Perturbation Theory (MPT). The index $\nu$ can be noninteger. The provided programs do basically the same job as the Mathematica package anQCD.m in Mathematica published by us previously, Ref.[1], but are now written in Fortran.
QCD running in neutrinoless double beta decay: Short-range mechanisms
2016
16 pages.- 3 figures.- 2 tables
A comparison of jet production rates on the Z0 resonance to perturbative QCD
1990
The production rates for 2-, 3-, 4- and 5-jet hadronic final states have been measured with the DELPHI detector at the e+e- storage ring LEP at centre of mass energies around 91.5 GeV. Fully corrected data are compared to O(αs 2) QCD matrix element calculations and the QCD scale parameter ΛMS is determined for different parametrizations of the renormalization scale μ2. Including all uncertainties our result is αs(MZ 2)=0.114±0.003[stat.]±0.004[syst.]±0.012[theor.] .
mb at MZ
1998
Abstract The value of the b quark mass at the M Z scale defined in the MS renormalization scheme, m b ( M Z ), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI detector to be m b (M Z )=2.67±0.25 ( stat. )±0.34 ( frag. )±0.27 ( theo. ) GeV/c 2 . The analysis considers NLO corrections to the three-jet production rate including mass effects, and the result obtained agrees with the QCD prediction of having a running b quark mass at an energy scale equal to M Z . This is the first time that such a measurement is performed far above the b b production threshold. The study also verifies the flavour independence of the strong coupling constant for b and l…
Heavy quark pair production in gluon fusion at next-to-next-to-leadingO(αs4)order: One-loop squared contributions
2008
We calculate the next-to-next-to-leading-order $\mathcal{O}({\ensuremath{\alpha}}_{s}^{4})$ one-loop squared corrections to the production of heavy-quark pairs in the gluon-gluon fusion process. Together with the previously derived results on the $q\overline{q}$ production channel, the results of this paper complete the calculation of the one-loop squared contributions of the next-to-next-to-leading-order $\mathcal{O}({\ensuremath{\alpha}}_{s}^{4})$ radiative QCD corrections to the hadroproduction of heavy flavors. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in dimensional regularization.
One-loop amplitudes for four-point functions with two external massive quarks and two external massless partons up toO(ε2)
2006
We present complete analytical O({epsilon}{sup 2}) results on the one-loop amplitudes relevant for the next-to-next-to-leading order (NNLO) quark-parton model description of the hadroproduction of heavy quarks as given by the so-called loop-by-loop contributions. All results of the perturbative calculation are given in the dimensional regularization scheme. These one-loop amplitudes can also be used as input in the determination of the corresponding NNLO cross sections for heavy flavor photoproduction, and in photon-photon reactions.
QCD sum rules for heavy baryons
2001
We construct the heavy baryonic currents by using the Bethe-Salpeter wave functions in the heavy quark limit. We discuss the one-loop renormalization of these heavy baryonic currents as well as their two-point correlators up to the order $1/M_h$. For a special case, we do the QCD sum rule for masses of the doublet (3/2,5/2).
Phase diagram of the two-channel kondo lattice model in one dimension.
2004
Employing the density matrix renormalization group method and strong-coupling perturbation theory, we study the phase diagram of the $\mathrm{SU}(2)\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(2)$ Kondo lattice model in one dimension. We show that, at quarter filling, the system can exist in two phases depending on the coupling strength. The weak-coupling phase is dominated by RKKY exchange correlations, while the strong-coupling phase is characterized by strong antiferromagnetic correlations of the channel degree of freedom. These two phases are separated by a quantum critical point. For conduction-band fillings of less than one-quarter, we find a paramagnetic metallic phase at weak coupl…