754 research outputs found

    Modified Fragmentation Function from Quark Recombination

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    Within the framework of the constituent quark model, it is shown that the single hadron fragmentation function of a parton can be expressed as a convolution of shower diquark or triquark distribution function and quark recombination probability, if the interference between amplitudes of quark recombination with different momenta is neglected. The recombination probability is determined by the hadron's wavefunction in the constituent quark model. The shower diquark or triquark distribution functions of a fragmenting jet are defined in terms of overlapping matrices of constituent quarks and parton field operators. They are similar in form to dihadron or trihadron fragmentation functions in terms of parton operator and hadron states. Extending the formalism to the field theory at finite temperature, we automatically derive contributions to the effective single hadron fragmentation function from the recombination of shower and thermal constituent quarks. Such contributions involve single or diquark distribution functions which in turn can be related to diquark or triquark distribution functions via sum rules. We also derive QCD evolution equations for quark distribution functions that in turn determine the evolution of the effective jet fragmentation functions in a thermal medium.Comment: 23 pages in RevTex with 8 postscript figure

    A NLO analysis on fragility of dihadron tomography in high energy AAAA collisions

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    The dihadron spectra in high energy AAAA collisions are studied within the NLO pQCD parton model with jet quenching taken into account. The high pTp_T dihadron spectra are found to be contributed not only by jet pairs close and tangential to the surface of the dense matter but also by punching-through jets survived at the center while the single hadron high pTp_T spectra are only dominated by surface emission. Consequently, the suppression factor of such high-pTp_T hadron pairs is found to be more sensitive to the initial gluon density than the single hadron suppression factor.Comment: 4 pages, 4 figures, proceedings for the 19th international Conference on ultra-relativistic nucleus-nucleus collisions (QM2006), Shanghai, China, November 14-20, 200

    Selective metal‐complexation on polymeric templates and their investigation via isothermal titration calorimetry

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    Selective complexation of metal ions represents a powerful tool for the development of versatile supramolecular architectures. While research in the field of molecular devices and machinery is sophisticated, the selective formation of metal complexes is not prevalent in polymer chemistry. Thus, the implementation of orthogonal binding concepts into a polymeric matrix is presented. In this context, an end‐functionalized poly( N ‐isopropylacrylamide) (PNIPAm) carrying zinc‐porphyrin (ZnTPP) as well as a terpyridine (tpy) ligand side by side is utilized. With these binding sites, the polymer can simultaneously interact with a pyridine moiety via a ZnTPP interaction and a terpyridine unit by the formation of a bis‐terpyridine complex. The complexation behavior of this polymer and different model compounds is intensively investigated by isothermal titration calorimetry. The obtained results indicate that the reported orthogonality of these two systems is successfully transferred into a functional polymeric architecture

    Bremsstrahlung Radiation as Coherent State in Thermal QED

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    Based on fully finite temperature field theory we investigate the radiation probability in the bremsstrahlung process in thermal QED. It turns out that the infrared divergences resulting from the emission and absorption of the real photons are canceled by the virtual photon exchange processes at finite temperature. The full quantum calculation results for soft photons radiation coincide completely with that obtained in the semi-classical approximation. In the framework of Thermofield Dynamics it is shown that the bremsstrahlung radiation in thermal QED is a coherent state, the quasiclassical behavior of the coherent state leads to above coincidence.Comment: 8 pages, 2 figure

    Improved modelling of helium and tritium production for spallation targets

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    Reliable predictions of light charged particle production in spallation reactions are important to correctly assess gas production in spallation targets. In particular, the helium production yield is important for assessing damage in the window separating the accelerator vacuum from a spallation target, and tritium is a major contributor to the target radioactivity. Up to now, the models available in the MCNPX transport code, including the widely used default option Bertini-Dresner and the INCL4.2-ABLA combination of models, were not able to correctly predict light charged particle yields. The work done recently on both the intranuclear cascade model INCL4, in which cluster emission through a coalescence process has been introduced, and on the de-excitation model ABLA allows correcting these deficiencies. This paper shows that the coalescence emission plays an important role in the tritium and 3He^3He production and that the combination of the newly developed versions of the codes, INCL4.5-ABLA07, now lead to good predictions of both helium and tritium cross sections over a wide incident energy range. Comparisons with other available models are also presented.Comment: 6 pages, 9 figure

    The MUSE-Wide Survey: Survey Description and First Data Release

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    We present the MUSE-Wide survey, a blind, 3D spectroscopic survey in the CANDELS/GOODS-S and CANDELS/COSMOS regions. Each MUSE-Wide pointing has a depth of 1 hour and hence targets more extreme and more luminous objects over 10 times the area of the MUSE-Deep fields (Bacon et al. 2017). The legacy value of MUSE-Wide lies in providing "spectroscopy of everything" without photometric pre-selection. We describe the data reduction, post-processing and PSF characterization of the first 44 CANDELS/GOODS-S MUSE-Wide pointings released with this publication. Using a 3D matched filtering approach we detected 1,602 emission line sources, including 479 Lyman-α\alpha (Lya) emitting galaxies with redshifts 2.9z6.32.9 \lesssim z \lesssim 6.3. We cross-match the emission line sources to existing photometric catalogs, finding almost complete agreement in redshifts and stellar masses for our low redshift (z < 1.5) emitters. At high redshift, we only find ~55% matches to photometric catalogs. We encounter a higher outlier rate and a systematic offset of Δ\Deltaz\simeq0.2 when comparing our MUSE redshifts with photometric redshifts. Cross-matching the emission line sources with X-ray catalogs from the Chandra Deep Field South, we find 127 matches, including 10 objects with no prior spectroscopic identification. Stacking X-ray images centered on our Lya emitters yielded no signal; the Lya population is not dominated by even low luminosity AGN. A total of 9,205 photometrically selected objects from the CANDELS survey lie in the MUSE-Wide footprint, which we provide optimally extracted 1D spectra of. We are able to determine the spectroscopic redshift of 98% of 772 photometrically selected galaxies brighter than 24th F775W magnitude. All the data in the first data release - datacubes, catalogs, extracted spectra, maps - are available on the website https://musewide.aip.de. [abridged]Comment: 25 pages 15+1 figures. Accepted, A&A. Comments welcom
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