Search results for "Observable"
showing 10 items of 634 documents
Triangle singularity enhancing isospin violation in ${\bar{{\rm{B}}}}_{{\rm{s}}}^{0}\to {\rm{J}}/{\rm{\psi }}{\pi }^{0}{{\rm{f}}}_{0}(980)$
2018
We perform calculations for the and reactions, showing that the first is isospin-suppressed while the second is isospin-allowed. The reaction proceeds via a triangle mechanism, with , followed by the decay K* → Kπ and a further fusion of into the or a0(980). We show that the mechanism develops a singularity around the π0 f0(980) or π0 a0(980) invariant mass of 1420 MeV, where the π0 f0 and π0 a0 decay modes are magnified and also the ratio of π0 f0 to π0 a0 production. Using experimental information for the decay, we are able to obtain absolute values for the reactions studied which fall into the experimentally accessible range. The reactions proposed and the observables evaluated, when con…
A time dependent RPA-theory for heavy ion reactions
1980
The time dependent Hartree Fock theory (TDHF) is generalized by incorporating 2p-2h correlations into the TDHF Slater determinant in order to improve the description of two-body observables. To this end a time dependent RPA theory (TDRPA) is formulated using the quasi boson approximation. The approach turns out to be readily applicable requiring only minor changes in the present time TDHF codes. The theory is exemplified by considering the spreading width of the fragment particle number in a nucleus-nucleus collision. The TDRPA states are furthermore used to formulate a scattering theory for heavy ion collisions which incorporates the quantum corrections of orderh2 by means of a gaussian pa…
Model-independent fit to Planck and BICEP2 data
2014
Inflation is the leading theory to describe elegantly the initial conditions that led to structure formation in our universe. In this paper, we present a novel phenomenological fit to the Planck, WMAP polarisation (WP) and the BICEP2 datasets using an alternative parameterisation. Instead of starting from inflationary potentials and computing the inflationary observables, we use a phenomenological parameterisation due to Mukhanov, describing inflation by an effective equation-of-state, in terms of the number of e-folds and two phenomenological parameters $\alpha$ and $\beta$. Within such a parametrisation, which captures the different inflationary models in a model-independent way, the valu…
Updated global analysis of the atmospheric neutrino data in terms of neutrino oscillations
2000
A global analysis of all the available atmospheric neutrino data is presented in terms of neutrino oscillations in the nu_mu -> nu_tau and nu_mu -> nu_s channels, where nu_s denotes a sterile neutrino. We perform our analysis of the contained events data as well as the upward-going neutrino-induced muon fluxes. In addition to the previous data samples of Frejus, Nusex, IMB and Kamioka experiments, we include the full data set of the 52 kton-yr of Super-Kamiokande, the recent 4.6 kton-yr contained events of Soudan2 and the results on upgoing muons from the MACRO and Baksan detectors. From the statistical analysis it emerges that the nu_mu -> nu_tau channel provides the best agreemen…
Limits on Anomalous Top Couplings from Z Pole Physics
1997
We obtain constraints on possible anomalous interactions of the top quark with the electroweak vector bosons arising from the precision measurements at the Z pole. In the framework of $SU(2)_L \otimes U(1)_Y$ chiral Lagrangians, we examine all effective CP-conserving operators of dimension five which induce fermionic currents involving the top quark. We constrain the magnitudes of these anomalous interactions by evaluating their one-loop contributions to the Z pole physics. Our analysis shows that the operators that contribute to the LEP observables get bounds close to the theoretical expectation for their anomalous couplings. We also show that those which break the $SU(2)_C$ custodial symm…
Top-Quark Pair Production Beyond Next-to-Leading Order
2010
We report on recent calculations of the differential cross section for top-quark pair production at hadron colliders. The results are differential with respect to the top-pair invariant mass and to the partonic scattering angle. In these calculations, which were carried out by employing soft-collinear effective theory techniques, we resummed threshold logarithms up to next-to-next-to-leading logarithmic order. Starting from the differential cross section, it is possible to obtain theoretical predictions for the invariant-mass distribution and the total cross section. We summarize here our results for these observables, and we compare them with the results obtained from different calculation…
Structure of chromomagnetic fields in the glasma
2014
The initial stage of a heavy ion collision is dominated by nonperturbatively strong chromoelectric and -magnetic fields. The spatial Wilson loop provides a gauge invariant observable to probe the dynamics of the longitudinal chromomagnetic field. We discuss recent results from a real time lattice calculation of the area-dependence of the expectation value of the spatial Wilson loop. We show that at relatively early times after the collision, a universal scaling as a function of the area emerges at large distances for very different initial conditions, with a nontrivial critical exponent. A similar behavior has earlier been seen in calculations of the gluon transverse momentum spectrum, whic…
Propagation of uncertainties in the nuclear DFT models
2014
Parameters of the nuclear density functional theory (DFT) models are usually adjusted to experimental data. As a result they carry certain theoretical error, which, as a consequence, carries out to the predicted quantities. In this work we address the propagation of theoretical error, within the nuclear DFT models, from the model parameters to the predicted observables. In particularly, the focus is set on the Skyrme energy density functional models.
Determination of the ΔS=1 weak Hamiltonian of the SU(4) chiral limit through topological zero-mode wave functions
2008
38 pages, 9 figures.-- Published in: JHEP05(2008)043, available at: http://dx.doi.org/10.1088/1126-6708/2008/05/043 (open-acess).
The first Virtual Compton Scattering experiment at MAMI
1999
Abstract Virtual Compton scattering, i.e. the exclusive reaction γ ∗ p → γ′p′ with γ ∗ denoting a virtual photon, provides new insights on the internal structure of the proton. Below π 0 production threshold, this experiment measures the generalized polarizabilities of the proton as defined by Guichon et al [1], [2] and Drechsel et al [3]. These new electromagnetic observables, functions of Q 2 , enlarge the concept of electric (α0 and magnetic (β) polarizabilities in Real Compton Scattering ( Q 2 =0) [4]. The first VCS experiment [5] of this kind was measured at the three spectrometer facility at the Mainz Microtron MAMI for Q 2 =0.33 GeV 2 and we present in this paper the preliminary resu…