Properties of new unflavored mesons below 2.4 GeV

The global features of spectrum of highly excited light nonstrange mesons can be well understood within both chiral symmetry restoration scenario combined with the relation $M^2\sim J+n$ and within nonrelativistic description based on the relation $M^2\sim L+n$. The predictions of these two alternative classifications for missing states are different and only future experiments can distinguish between the two. We elaborate and compare systematically the predictions of both schemes, which may serve as a suggestion for future experiments devoted to the search for missing states.Comment: 5 pages, to appear in Phys. Rev. C XX, 005200 (2007

Theory of phonon-drag thermopower of extrinsic semiconducting single-wall carbon nanotubes and comparison with previous experimental data

A theoretical model for the calculation of the phonon-drag thermopower, $S^{g}$, in degenerately doped semiconducting single-wall carbon nanotubes (SWCNTs) is proposed. Detailed calculations of $S^{g}$ are performed as a function of temperature, tube radius and position of the Fermi level. We derive a simple analytical expression for $S^{g}$ that can be utilized to determine the free carrier density in doped nanotubes. At low temperatures $S^{g}$ shows an activated behavior characteristic of the one-dimensional (1D) character of carriers. Screening effects are taken into account and it is found that they dramatically reduce the magnitude of $S^{g}$. Our results are compared with previous published experimental data in bulk p-doped SWCNT materials. Excellent agreement is obtained in the temperature range 10-200 K for a consistent set of parameters. This is a striking result in view of the complexity of these systems.Comment: 21 pages, 6 figures. This version has been accepted for publication in Phys. Rev.

Implications of the Crystal Barrel data for meson-baryon symmetries

Making use of numerous resonances discovered by the Crystal Barrel Collaboration we discuss some possible relations between the baryon and meson spectra of resonances composed of the light non-strange quarks. Our goal is to indicate new features that should be reproduced by the realistic dynamical models describing the hadron spectrum in the sector of light quarks.Comment: Completely modified version; to appear in Mod. Phys. Lett.

Parity doubling in particle physics

Parity doubling in excited hadrons is reviewed. Parity degeneracy in hadrons was first experimentally observed 40 years ago. Recently new experimental data on light mesons caused much excitement and renewed interest to the phenomenon, which still remains to be enigmatic. The present retrospective review is an attempt to trace the history of parity doubling phenomenon, thus providing a kind of introduction to the subject. We begin with early approaches of 1960s (Regge theory and dynamical symmetries) and end up with the latest trends (manifestations of broader degeneracies and AdS/QCD). We show the evolution of various ideas about parity doubling. The experimental evidence for this phenomenon is scrutinized in the non-strange sector. Some experiments of 1960s devoted to the search for missing non-strange bosons are re-examined and it is argued that results of these experiments are encouraging from the modern perspective.Comment: Version to appear in Int. J. Mod. Phys. A, 63 pages, 9 figure

Weinberg like sum rules revisited

The generalized Weinberg sum rules containing the difference of isovector vector and axial-vector spectral functions saturated by both finite and infinite number of narrow resonances are considered. We summarize the status of these sum rules and analyze their overall agreement with phenomenological Lagrangians, low-energy relations, parity doubling, hadron string models, and experimental data.Comment: 31 pages, noticed misprints are corrected, references are added, and other minor corrections are mad

Electromagnetic proton form factors in large NcN_{c} QCD

The electromagnetic form factors of the proton are obtained using a particular realization of QCD in the large $N_c$ limit (${QCD}_{\infty}$), which sums up the infinite number of zero-width resonances to yield an Euler's Beta function (Dual-${QCD}_{\infty}$). The form factors $F_1(q^2)$ and $F_2(q^2)$, as well as $G_M(q^2)$ agree very well with reanalyzed space-like data in the whole range of momentum transfer. In addition, the predicted ratio $\mu_p G_E/G_M$ is in good agreement with recent polarization transfer measurements at Jefferson Lab.Comment: 10 page

Dephasing Times in a Non-degenerate Two-Dimensional Electron Gas

Studies of weak localization by scattering from vapor atoms for electrons on a liquid helium surface are reported. There are three contributions to the dephasing time. Dephasing by the motion of vapor atoms perpendicular to the surface is studied by varying the holding field to change the characteristic width of the electron layer at the surface. A change in vapor density alters the quasi-elastic scattering length and the dephasing due to the motion of atoms both perpendicular and parallel to the surface. Dephasing due to the electron-electron interaction is dependent on the electron density.Comment: 4 pages, Revte

New Projects of Crystal Extraction at IHEP 70 GeV Accelerator

Using channeling in a 5-mm crystal with bending angle of 0.65 mrad, a record high efficiency, over 60%, of particle extraction from accelerator was achieved. The extracted beam intensity was up to 5.2 x 10**11 protons per spill of ~ 0.5 s duration. Also, the first proof-of-principle experiment on crystal collimation' was performed where crystal - serving as a scraper - has reduced the radiation level in the accelerator by a factor of two. The measurements agree with Monte Carlo predictions

Application of bent crystals at IHEP 70-GeV accelerator to enhance the efficiency of its usage

Bent crystal was extracting 70-GeV protons with average intensity 4*10^11 (as measured in external beamline) per spill of 1.6 s duration, in parallel to the simultaneous work of two internal targets in the accelerator ring. An additional crystal, placed in the external beamline, was deflecting a small part of the extracted beam with intensity 10^7 protons toward another physics experiment. Crystal-extracted beam had a typical size of 4 mm by 4 mm fwhm at the end of the external beamline. Measurements for the extraction efficiency and other characteristics at the simultaneous work of four experimental set-ups are presented. With crystal working in the above-said regime during one month, no degradation of channeling was observed. The studies of extraction efficiency have been continued with new crystals.Comment: 6pp. Presented at EPAC 200