Quarkonium production and decays

Quarkonium decays are studied in the charmonium model. Relativistic corrections, higher-order perturbative QCD corrections and non- perturbative contributions are discussed. Recent measurements of charmonium annihilation rates are used to evaluate the strong coupling constant $\alpha_s$ simultaneously with the wave functions (and their derivatives) at the origin. Further predictions are made for yet unobserved decay rates. The various models for quarkonium production in hadronic collisions are critically reviewed. Based on the charmonium model, the cross sections of different quarkonium states are given in a well-defined QCD perturbation series, including quark--antiquark, quark--gluon, and gluon--gluon scatterings. Numerical estimates are given for charmonium production in \p\p, \ppbar, and \pi\p collisions. The role of indirect \JP production via $\chi_{\c J}(1P)$, \eta_{\c}(2S), $\psi(2S)$ and \b-decays is pointed out. Relativistic effects and non-perturbative contributions are found to be important. Existing measurements are compiled and shown to be well explained if all contributions are included. The ${}^1S_0$ cross section is calculated in complete next-to-leading order. Finally, a study of the high-energy behaviour of quarkonium cross sections is made, based on the asymptotical behaviour of higher-order QCD corrections.Comment: 128 pages, compressed ps file available via anonymous ftp to darssrv1.cern.ch: cern/9402/th-7170-94.ps.Z, CERN-TH.7170/9

Model-independent QED corrections to photon structure-function measurements

We present the first calculation of QED radiative corrections to deep-inelastic electron-photon scattering in terms of those variables that are reconstructed in measurements of the photon structure function in electron-positron collisions. In order to cover the low-$Q^2$ region, we do not invoke the QCD-improved parton model but rather express our results in terms of the photon structure functions. Both analytical and numerical results are given.Comment: Latex, 8 pages, 3 figures, uses epsfig.sty, 12pt.st

Models for Photon-photon Total Cross-sections

We present here a brief overview of recent models describing the photon-photon cross-section into hadrons. We shall show in detail results from the eikonal minijet model, with and without soft gluon summation.Comment: 7 pages, 5 figures, laTeX, requires espcrc2.sty. To appear in the Proceedings of Photon-99, Freiburg, 23 -27 May 99, labels in the figures 1,3,4,5 corrected, one typo in an equation correcte

χcJ\chi_{c J} production in e+e−e^+e^- annihilation

Inclusive production of $\chi_{c J}$ in $e^+e^-$ annihilation is an excellent probe of the role of higher Fock states in the production of heavy quarkonia. Within the non-relativistic QCD approach, contributions from the short-distance production of colour-octet $c\bar{c}$ pairs are significantly larger than those from colour-singlet production. At the same time, $\chi_{c J}$ production rates are significantly smaller than expected in the colour evaporation approach. Measurements of $\chi_{\c J}$ production at CLEO and future B-factories will thus constitute a major test of theoretical approaches to the production of heavy quarkonia.Comment: 11 pages, Revtex, 2 figure

Are the reactions γγ→VV′\gamma\gamma\to VV' a challenge for the factorized Pomeron at high energies?

We would like to point to the strong violation of the putative factorized Pomeron exchange model in the reactions $\gamma\gamma\to VV'$ in the high-energy region where this model works fairly well in all other cases.Comment: 4 pages, LaTex, 1 fig. in postscript, minor typos corrected, to be published in Phys. Rev. D 60, 117503 (1999

Meson-photon transition form factors and resonance cross-sections in e+e−e^+ e^- collisions

Meson--photon--photon transition form factors for S-, P-, and D-wave states are calculated, the meson being treated as a non-relativistic heavy-quark--antiquark pair. The full dependence on both photon virtualities is included. Cross-section formulas for charge-conjugation even mesons with J^P = 0^-, 0^+, 1^+, 2^+, and 2^- in electron--positron collisions are presented and numerical results for LEP energies are given. In particular, we find two-photon event rates for \chi_{\rc 1}, \eta_{\rc}(2S), and \eta_{\rb}(1S) within reach of LEP. With minor modifications to incorporate SU(3)-flavour breaking we estimate rates for 18 light mesons as well, based on the observation that their two-photon decay widths agree remarkably well with measured data. Finally we point out that e^+ e^- cross sections for 1^+ states do not vanish at low Q^2, the Landau--Yang suppression factors of the two-photon cross sections being compensated by the photon propagators

PEPSI deep spectra. III. A chemical analysis of the ancient planet-host star Kepler-444

We obtained an LBT/PEPSI spectrum with very high resolution and high signal-to-noise ratio (S/N) of the K0V host Kepler-444, which is known to host 5 sub-Earth size rocky planets. The spectrum has a resolution of R=250,000, a continuous wavelength coverage from 4230 to 9120A, and S/N between 150 and 550:1 (blue to red). We performed a detailed chemical analysis to determine the photospheric abundances of 18 chemical elements, in order to use the abundances to place constraints on the bulk composition of the five rocky planets. Our spectral analysis employs the equivalent width method for most of our spectral lines, but we used spectral synthesis to fit a small number of lines that require special care. In both cases, we derived our abundances using the MOOG spectral analysis package and Kurucz model atmospheres. We find no correlation between elemental abundance and condensation temperature among the refractory elements. In addition, using our spectroscopic stellar parameters and isochrone fitting, we find an age of 10+/-1.5 Gyr, which is consistent with the asteroseismic age of 11+/-1 Gyr. Finally, from the photospheric abundances of Mg, Si, and Fe, we estimate that the typical Fe-core mass fraction for the rocky planets in the Kepler-444 system is approximately 24 per cent. If our estimate of the Fe-core mass fraction is confirmed by more detailed modeling of the disk chemistry and simulations of planet formation and evolution in the Kepler-444 system, then this would suggest that rocky planets in more metal-poor and alpha-enhanced systems may tend to be less dense than their counterparts of comparable size in more metal-rich systems.Comment: in press, 11 pages, 3 figures, data available from pepsi.aip.d

The Trigger Menu Handler of the ATLAS Level-1 Central Trigger Processor

The role of the Central Trigger Processor (CTP) in the ATLAS Level-1 trigger is to combine information from the calorimeter and muon trigger processors, as well as from other sources, e.g. calibration triggers, and to make the final Level-1 decision. The information sent to the CTP consists of multiplicity values for a variety of pT thresholds, and of flags for ET thresholds. The algorithm used by the CTP to combine the different trigger inputs allows events to be selected on the basis of menus. Different trigger menus for different run conditions have to be considered. In order to provide sufficient flexibility and to fulfil the required low latency, the CTP will be implemented with look-up tables and programmable logic devices. The trigger menu handler is the tool that translates the human-readable trigger menu into the configuration files necessary for the hardware, stores several prepared configurations and down-loads them into the hardware on request. An automatic compiler for the trigger menu and a prototype of the trigger menu handler have been implemented

Cortical Thickness of Brain Areas Beyond Stroke Lesions and Sensory-Motor Recovery: A Systematic Review

Background: The clinical outcome of patients suffering from stroke is dependent on multiple factors. The features of the lesion itself play an important role but clinical recovery is remarkably influenced by the plasticity mechanisms triggered by the stroke and occurring at a distance from the lesion. The latter translate into functional and structural changes of which cortical thickness might be easy to quantify one of the main players. However, studies on the changes of cortical thickness in brain areas beyond stroke lesion and their relationship to sensory-motor recovery are sparse. Objectives: To evaluate the effects of cerebral stroke on cortical thickness (CT) beyond the stroke lesion and its association with sensory-motor recovery. Materials and Methods: Five electronic databases (PubMed, Embase, Web of Science, Scopus and the Cochrane Library) were searched. Methodological quality of the included studies was assessed with the Newcastle-Ottawa Scale for non-randomized controlled trials and the Risk of Bias Cochrane tool for randomized controlled trials. Results: The search strategy retrieved 821 records, 12 studies were included and risk of bias assessed. In most of the included studies, cortical thinning was seen at the ipsilesional motor area (M1). Cortical thinning can occur beyond the stroke lesion, typically in regions anatomically connected because of anterograde degeneration. Nonetheless, studies also reported cortical thickening of regions of the unaffected hemisphere, likely related to compensatory plasticity. Some studies revealed a significant correlation between changes in cortical thickness of M1 or somatosensory (S1) cortical areas and motor function recovery. Discussion and Conclusions: Following a stroke, changes in cortical thickness occur both in regions directly connected to the stroke lesion and in contralateral hemisphere areas as well as in the cerebellum. The underlying mechanisms leading to these changes in cortical thickness are still to be fully understood and further research in the field is needed. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020200539; PROSPERO 2020, identifier: CRD42020200539