Sökresultat

Fourier transform spectroscopy has proven to be a useful toot when measuring wavelengths and branching fractions. The high spectral resolution makes it possible to extend and improve term analyses of complex spectra. We present an overview of our measurements with the Fourier transform spectrometer at Lund Observatory. Much of our work is motivated by astrophysical problems, and we show an applica

We introduce four-point functions in the hadronic ladder resummation approach to large N-c QCD Green functions. We determine the relevant one to calculate the B-K kaon parameter in the chiral limit. This four-point function contains both the large momenta QCD OPE and the small momenta ChPT at NLO limits, analytically. We get (B) over cap (X)(K) = 0.38 +/- 0.15. We also give the ChPT result at NLO

New experimental lifetimes for two levels in doubly ionized tungsten, W III, have been obtained using the time-resolved laser-induced-fluorescence technique. Theoretical oscillator strengths obtained from a HFR calculation including the effects of core-polarization are reported for all transitions from levels below E < 70000 cm(-1) and with log g f >= -2, thus greatly extending our knowledge of th

At small x, the effects of finite transverse momenta of partons inside a hadron become increasingly important, especially in analyses of jets and heavy-quark production. These effects can be systematically accounted for in a formalism based on k(perpendicular to)-factorization and unintegrated distribution functions. We present results for the unintegrated distribution function, together with the

We present an implementation of the Linked Dipole Chain model for deeply inelastic ep scattering into the framework of the ARIADNE event generator. Using this implementation we obtain results both for the inclusive structure function as well as for exclusive properties of the hadronic final state.

This paper discusses a general class of ladder resummation inspired hadronic approximations. It is found that this approach naturally reproduces many successes of single meson per channel saturation models (e.g. VMD) and NJL based models. In particular the existence of a constituent quark mass and a gap equation follows naturally. We construct an approximation that satisfies a large set of QCD sho

Using the large N-C approximation we have constructed the most general chiral resonance Lagrangian in the odd-intrinsic parity sector that can generate low-energy chiral constants up to O(p(6)). Integrating out the resonance fields these O(p(6)) constants are expressed in terms of resonance couplings and masses. The role of eta' is discussed and its contribution is explicitly factorized. Using the

In a previous report we used the Linked Dipole Chain model unintegrated gluon densities to investigate the uncertainties in the predictions for central exclusive production of scalars at hadron colliders. Here we expand this investigation by also looking at other parameterizations of the unintegrated gluon density, and look in more detail on the behavior of these at small k(<^>). We confirm our co

We investigate the implication of uncertainties in the unintegrated gluon distribution for the predictions for central exclusive production of scalars at hadron colliders. We use parameterizations of the k(perpendicular to)-unintegrated gluon density obtained from the Linked Dipole Chain model, applying different options for the treatment of non-leading terms. We find that the luminosity function

The scalar form factors for the pions and kaons are calculated in SU(3) Chiral Perturbation Theory at order p(6), in the isospin limit m(u)=m(d)=(m) over cap. We find in general sizable corrections of O(p(6)). We use our results to obtain information on the 1/N-c suppressed low energy constants L-4(r) and L-6(r) as well as on two O(p(6)) low energy constants. We present some numerical results for

We discuss what happens at the end of the QCD cascades. We show that, with just a few reasonable assumptions, the emission of soft gluons is constrained to produce an ordered field in the form of a helix. We describe how to modify the Lund fragmentation scheme in order to fragment such a field. Our modified fragmentation scheme yields results which are consistent with current experimental measurem

Radiative lifetimes of 7 odd and 11 even parity states of Tb I (Z = 65) have been measured by the time resolved laser induced fluorescence method (TR-LIF). Experimental data for 9 out of the 18 states are obtained for the first time. The radiative lifetimes presented in this study are in good agreement with previous TR-LIF experimental results but systematically shorter than those obtained by the

We describe an algorithm for improving subsequent parton shower emissions by full SU(3) color correlations in the framework of a dipole-type shower. As a proof of concept, we present results from the first implementation of such an algorithm for a final state shower. The corrections are found to be small for event shapes and jet rates but can be more significant for tailored observables.

Recently, new soft graviton theorem proposed by Cachazo and Strominger has inspired a lot of works. In this note, we use the KLT-formula to investigate the theorem. We have shown how the soft behavior of color ordered Yang-Mills amplitudes can be combined with KLT relation to give the soft behavior of gravity amplitudes. As a byproduct, we find two nontrivial identities of the KLT momentum kernel

We calculate next-to-leading order (NLO) QCD corrections to electroweak Higgs boson plus three jet production. Both vector boson fusion (VBF) and Higgs-strahlung type contributions are included along with all interferences. The calculation is implemented within the MATCHBOX NLO framework of the HERWIG++ event generator.

Adopting the hypothesis about the exact cancellation of vacuum condensates contributions to the ground state energy in particle physics to the leading order in graviton-mediated interactions, we argue that the observable cosmological constant can be dynamically induced by an uncompensated quantum gravity correction to them after the QCD phase transition epoch. To start with, we demonstrate a possi