119210924
Gauge-invariant Theory of Two-Pion Photo- and Electro-Production off the Nucleon
A field-theoretical description of the photoproduction of two pions off the nucleon is presented that applies to real as well as virtual photons in the one-photon approximation. The Lorentz-covariant theory is complete at the level of all explicit Faddeev-type three-body final-state mechanisms of dressed interacting hadrons, including those of the nonlinear Dyson–Schwinger type. All electromagnetic currents are constructed to satisfy their respective (generalized) Ward-Takahashi identities and thus satisfy local gauge invariance as a matter of course. The Faddeev-type ordering structure results in a natural expansion of the full two-pion photoproduction current $${M^\mu_{\pi \pi}}$$ in terms of multiple loops that preserve gauge invariance order by order in the number of loops, which in turn lends itself naturally to practical applications of increasing sophistication with increasing number of loops.
118886519
Skyrmions with vector mesons in the hidden local symmetry approach
(hWZ) terms. We write a general “master formula” that allows us to determine the parameters of the HLS Lagrangian from a class of holographic QCD models valid at large Nc and � (’t Hooft constant) limit by integrating out the infinite towers of vector and axial-vector mesons other than the lowest � and ! mesons. Within this approach we find that the physical properties of the Skyrmion as the solitonic description of baryons are independent of the HLS parameter a. Therefore the only parameters of the model are the pion decay constant and the vector meson mass. Once determined in the meson sector, we have a totally parameter-free theory that allows us to study unequivocally the role of light vector mesons in the Skyrmion structure. We find, as suggested by Sutcliffe, that
119182023
Skyrmions, half-skyrmions and nucleon mass in dense baryonic matter
We explore the hadron properties in dense baryonic matter in a unified way by using a Skyrme model constructed with an effective Lagrangian which includes the ρ and ω vector mesons as hidden gauge bosons and is valid up to O(p4) in chiral expansion including the homogeneous Wess-Zumino terms. With the two input values of pion decay constant and the lowest lying vector meson mass which can be fixed in free space, all the other low energy constants in the effective Lagrangian are determined by their master formulas derived from holographic QCD models, which allows us to study the baryonic matter properties with no additional free parameters and thus without ambiguities. We find that the ω field that figures in the homogeneous Wess-Zumino term plays a crucial role in the skyrmion structure and its matter properties. The most striking and intriguing observation is that the pion decay constant that smoothly drops with increasing density in the Skyrmion phase stops decreasing at n1/2 at which the skyrmions in medium fractionize into half-skyrmions and remains nearly constant in the half-skyrmion phase. In accordance with the large Nc consideration, the baryon mass also stays non-scaling in the half-skyrmion phase. This feature is supported by the nuclear effective field theory with the parameters of the Lagrangian scaling modified at the skyrmion–half-skyrmion phase transition. Our exploration also uncovers the crucial role of the ω meson in multi-baryon systems as well as in the structure of a single skyrmion.
990859
Polarization Observables in {phi} -Meson Photoproduction and the Strangeness Content of the Proton
The contributions of direct knockout processes, in addition to the diffractive production and one-pion-exchange processes associated with the ��� and �� couplings, to the polarization observables of thephotoproduction from pro- ton are calculated. We make use of Pomeron-photon analogy and a relativistic harmonic oscillator quark model. We find that some of the double polariza- tion observables are very sensitive to a possible s¯ s admixture in the proton. It arises from the difference in the spin structures of the three different am- plitudes. This suggests that such measurements could be very useful to probe the strangeness content in the proton.
34948294
Heavy baryons as Skyrmions with 1/mQ corrections.
We take into account the 1/[ital m][sub [ital Q]] corrections up to 1/[ital N][sub [ital c]] order in the heavy-meson-soliton bound state approach for heavy baryons. With these corrections, the mass spectra of baryons with [ital c] quarks as well as of those with [ital b] quarks are well reproduced. For charmed baryons, however, the correction to the mass spectra amounts to about 300 MeV, which is not small compared to the leading order binding energy, [similar to]800 MeV.
41744701
Nuclear modification factor of nonphotonic electrons in heavy-ion collisions, and the heavy-flavor baryon-to-meson ratio
The nuclear modification factor ${R}_{\mathit{AA}}$ of nonphotonic electrons in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV is studied by considering the decays of heavy-flavor hadrons produced in a quark coalescence model. Although an enhanced ${\ensuremath{\Lambda}}_{c}/{D}^{0}$ ratio is predicted by the coalescence model, it is peaked at small transverse momenta ($~2$ GeV) due to the large difference between heavy and light quark masses. As a result, the enhanced ${\ensuremath{\Lambda}}_{c}/{D}^{0}$ ratio, which is expected to suppress the electron ${R}_{\mathit{AA}}$ as the branching ratio of ${\ensuremath{\Lambda}}_{c}$ decay into electrons is smaller than that of ${D}^{0}$, does not lead to additional suppression of the electron ${R}_{\mathit{AA}}$ at large transverse momenta ($\ensuremath{\geqslant}5$ GeV), where the suppression is mainly due to heavy quark energy loss in produced quark-gluon plasma. Also, the enhanced ${\ensuremath{\Lambda}}_{b}/{\overline{B}}^{0}$ ratio predicted by the coalescence model has even smaller effect on the nonphotonic electron ${R}_{\mathit{AA}}$ as bottom baryons and mesons have similar branching ratios for semileptonic decays into electrons.
121615298
Measurement of the refractive index of the LAB-based liquid scintillator and acrylic at RENO
In this paper, we describe the first measurement of the refractive index of the linear alkyl benzene (LAB)-based liquid scintillator and acrylic used at the Reactor Experiment for Neutrino Oscillation (RENO). The refractive index of a material is an important optical property and the prism spectrometer is the most common device for measuring the refractive index. Using the minimum deviation technique, which requires an exact measurement of the apex angle, we determined the refractive indices at six different wavelengths and then fitted them. We also compared the refractive index of the LAB-based liquid scintillator with the refractive indices of other liquid scintillator solvents commonly used in reactor neutrino experiments.
121196804
CERN beam test of silicon-tungsten calorimeter test module
PIN diode silicon sensors with low leakage current were developed as 4×4 pixel arrays from 5 inch wafers. A test module of silicon-tungsten calorimeter was designed, built using the sensors, and tested with high energy beam of electron, muon, and hadrons for the study of its application at the future linear collider. The construction of the test module and the results of the beam test are discussed.