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Search Results: 1 - 10 of 7151 matches for " Th. Klein "
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On the Asymptotic Behaviour of F_2(x,Q^2)
A. DeRoeck,M. Klein,Th. Naumann
Statistics , 1996, DOI: 10.1016/0370-2693(96)00976-8
Abstract: We discuss how the proton structure function F2 is described in the HERA kinematic range by double asymptotic expressions for low x and large Q^2. From a NLO double asymptotic approximation of recent data from the H1 experiment at HERA we extract the strong coupling constant alpha_S(M^2_Z)=0.113+/-0.002(stat)+/-0.007(syst). The additional theoretical error can be as large as 0.007.
$B \to D^{(*)}$ Form Factors from QCD Light-Cone Sum Rules
Faller, S.;Khodjamirian, A.;Klein, Ch.;Mannel, Th.
High Energy Physics - Phenomenology , 2008, DOI: 10.1140/epjc/s10052-009-0968-4
Abstract: We derive new QCD sum rules for $B\to D$ and $B\to D^*$ form factors. The underlying correlation functions are expanded near the light-cone in terms of $B$-meson distribution amplitudes defined in HQET, whereas the $c$-quark mass is kept finite. The leading-order contributions of two- and three-particle distribution amplitudes are taken into account. From the resulting light-cone sum rules we calculate all $B\to \Dst $ form factors in the region of small momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the sum rules reduce to a single expression for the Isgur-Wise function. We compare our predictions with the form factors extracted from experimental $B\to \Dst l \nu_l$ decay rates fitted to dispersive parameterizations.
Semileptonic charm decays $D \to πl ν_?$ and $D \to K l ν_l$ from QCD Light-Cone Sum Rules
A. Khodjamirian,Ch. Klein,Th. Mannel,N. Offen
Physics , 2009, DOI: 10.1103/PhysRevD.80.114005
Abstract: We present a new calculation of the $D\to\pi$ and $D \to K$ form factors from QCD light-cone sum rules. The $\overline{MS}$ scheme for the $c$-quark mass is used and the input parameters are updated. The results are $f^+_{D\pi}(0)= 0.67^{+0.10}_{-0.07}$, $f^+_{DK}(0)=0.75^{+0.11}_{-0.08}$ and $f^+_{D\pi}(0)/f^+_{DK}(0)=0.88 \pm 0.05$. Combining the calculated form factors with the latest CLEO data, we obtain $|V_{cd}|=0.225\pm 0.005 \pm 0.003 ^{+0.016}_{-0.012}$ and $|V_{cd}|/|V_{cs}|= 0.236\pm 0.006\pm 0.003\pm 0.013$ where the first and second errors are of experimental origin and the third error is due to the estimated uncertainties of our calculation. We also evaluate the form factors $f^-_{D\pi}$ and $f^-_{DK}$ and predict the slope parameters at $q^2=0$. Furthermore, calculating the form factors from the sum rules at $q^2<0$, we fit them to various parameterizations. After analytic continuation, the shape of the $D\to \pi,K $ form factors in the whole semileptonic region is reproduced, in a good agreement with experiment.
How much charm can PANDA produce?
A. Khodjamirian,Ch. Klein,Th. Mannel,Y. -M. Wang
Physics , 2011, DOI: 10.1140/epja/i2012-12031-8
Abstract: We consider the production of charmed baryons and mesons in the proton-antiproton binary reactions at the energies of the future $\bar{P}$ANDA experiment. To describe these processes in terms of hadronic interaction models, one needs strong couplings of the initial nucleons with the intermediate and final charmed hadrons. Similar couplings enter the models of binary reactions with strange hadrons. For both charmed and strange hadrons we employ the strong couplings and their ratios calculated from QCD light-cone sum rules. In this method finite masses of $c$ and $s$ quarks are taken into account. Employing the Kaidalov's quark-gluon string model with Regge poles and adjusting the normalization of the amplitudes in this model to the calculated strong couplings, we estimate the production cross section of charmed hadrons. For $p\bar{p}\to \Lambda_c\bar{\Lambda}_c$ it can reach several tens of $nb$ at $p_{lab}= 15 {GeV}$, whereas the cross sections of $\Sigma_c$ and $D$ pair production are predicted to be smaller.
First Detection of Millimeter Dust Emission from Brown Dwarf Disks
R. Klein,D. Apai,I. Pascucci,Th. Henning,L. B. F. M. Waters
Physics , 2003, DOI: 10.1086/377729
Abstract: We report results from the first deep millimeter continuum survey targeting Brown Dwarfs (BDs). The survey led to the first detection of cold dust in the disks around two young BDs (CFHT-BD-Tau 4 and IC348 613), with deep JCMT and IRAM observations reaching flux levels of a few mJy. The dust masses are estimated to be a few Earth masses assuming the same dust opacities as usually applied to TTauri stars.
What does the “arrow of time” stand for?  [PDF]
Etienne Klein
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.23033
Abstract: One hundred and thirty years after the work of Ludwig Boltzmann on the interpretation of the irreversibility of physical phenomena, and one century after Einstein's formulation of Special Relativity, we are still not sure what we mean when we talk of “time” or “arrow of time”. We shall try to show that one source of this difficulty is our tendency to confuse, at least verbally, time and becoming, i.e. the course of time and the arrow of time, two concepts that the formalisms of modern physics are careful to distinguish. The course of time is represented by a time line that leads us to define time as the producer of duration. It is customary to place on this time line a small arrow that, ironically, must not be confused with the “arrow of time”. This small arrow is only there to indicate that the course of time is oriented, has a well-defined direction, even if this direction is arbitrary. The arrow of time, on the other hand, indicates the possibility for physical systems to experience, over the course of time, changes or transforma-tions that prevent them from returning to their initial state forever. Contrary to what the ex-pression “arrow of time” suggests, it is there-fore not a property of time itself but a property of certain physical phenomena whose dynamic is irreversible. By its very definition, the arrow of time presupposes the existence of a well- established course of time within which – in addition – certain phenomena have their own temporal orientation. We think that it is worth-while to emphasize the difference between sev-eral issues traditionally subsumed under the label “the problem of the direction of time”. If the expressions “course of time”, “direction of time” and “arrow of time” were better defined, systematically distinguished from one another and always used in their strictest sense, the debate about time, irreversibility and becoming in physics would become clearer.
The structured environments of embedded star-forming cores. PACS and SPIRE mapping of the enigmatic outflow source UYSO 1
H. Linz,O. Krause,H. Beuther,Th. Henning,R. Klein,M. Nielbock,B. Stecklum,J. Steinacker,A. Stutz
Physics , 2010, DOI: 10.1051/0004-6361/201014669
Abstract: The intermediate-mass star-forming core UYSO 1 has previously been found to exhibit intriguing features. While deeply embedded and previously only identified by means of its (sub-)millimeter emission, it drives two powerful, dynamically young, molecular outflows. Although the process of star formation has obviously started, the chemical composition is still pristine. We present Herschel PACS and SPIRE continuum data of this presumably very young region. The now complete coverage of the spectral energy peak allows us to precisely constrain the elevated temperature of 26 - 28 K for the main bulge of gas associated with UYSO1, which is located at the interface between the hot HII region Sh 2-297 and the cold dark nebula LDN 1657A. Furthermore, the data identify cooler compact far-infrared sources of just a few solar masses, hidden in this neighbouring dark cloud.
Probing Dust around Brown Dwarfs: The naked LP 944-20 and the Disk of Cha Ha2
D. Apai,I. Pascucci,Th. Henning,M. F. Sterzik,R. Klein,D. Semenov,E. Guenther,B. Stecklum
Physics , 2002, DOI: 10.1086/342210
Abstract: We present the first mid-infrared (MIR) detection of a field brown dwarf (BD) and the first ground-based MIR measurements of a disk around a young BD candidate. We prove the absence of warm dust surrounding the field BD LP 944-20. In the case of the young BD candidate Cha Ha2, we find clear evidence for thermal dust emission from a disk. Surprisingly, the object does not exhibit any silicate feature as previously predicted. We show that the flat spectrum can be explained by an optically thick flat dust disk.
Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy
P. Szabo,P. Samuely,J. Kacmarcik,Th. Klein,J. Marcus,D. Fruchart,S. Miraglia,C. Marcenat,A. G. M. Jansen
Physics , 2001, DOI: 10.1103/PhysRevLett.87.137005
Abstract: Experimental support is found for the multiband model of the superconductivity in the recently discovered system MgB2 with the transition temperature Tc = 39 K. By means of Andreev reflection evidence is obtained for two distinct superconducting energy gaps. The sizes of the two gaps (Delta_S = 2.8 meV and Delta_L = 7 meV) are respectively smaller and larger than the expected weak coupling value. Due to the temperature smearing of the spectra the two gaps are hardly distinguishable at elevated temperatures but when a magnetic field is applied the presence of two gaps can be demonstrated close to the bulk T_c in the raw data.
The Efficacy of Hyaluronic Acid in the Restoration of Soft Tissue Volume of the Lips and Lower 1/3 of the Face: The Evolution of the Injection Technique  [PDF]
Arnold William Klein
Journal of Cosmetics, Dermatological Sciences and Applications (JCDSA) , 2011, DOI: 10.4236/jcdsa.2011.14022
Abstract: Study objective: To establish the safety and efficacy of small-gel particle hyaluronic acid (SGP-HA; Restylane®, Medicis Aesthetics Inc., Scottsdale, AZ) for lip augmentation. Study design: This was a Phase 3, prospective, open-label, evaluator-blinded, single-center pilot study of SGP-HA use in lip augmentation. The primary efficacy objectives were to investigate the efficacy of SGP-HA in lip augmentation and to assess subject satisfaction with the procedure 12 weeks after treatment. Secondary efficacy objectives were to validate 3D imaging to measure lip augmentation, identify subject satisfaction at all points in time, and identify the duration of lip augmentation and palpability of SGP-HA in the lips. The primary safety objective was to assess the incidence, duration, and severity of all adverse experiences. Results: All 20 subjects and the treating investigator indicated improvement in the appearance of subjects’ lips at weeks 2, 6, and 12. SGP-HA administered for augmentation was well tolerated. Four (20%) subjects treated with SGP-HA experienced 7 treatment-emergent adverse events (TEAEs). Conclusions: Results of this study show promising efficacy and an absence of safety issues with the use of SGP-HA in lip augmentation.
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