Study on initial geometry fluctuations via participant plane correlations in heavy ion collisions: part II

Further investigation of the participant plane correlations within a Glauber model framework is presented, focusing on correlations between three or four participant planes of different order. A strong correlation is observed for $\cos(2\Phi_{2}^*+3\Phi_{3}^*-5\Phi_{5}^*)$ which is a reflection of the elliptic shape of the overlap region. The correlation between the corresponding experimental reaction plane angles can be easily measured. Strong correlations of similar geometric origin are also observed for $\cos(2\Phi_{2}^*+4\Phi_{4}^*-6\Phi_{6}^*)$, $\cos(2\Phi_2^*-3\Phi_3^*-4\Phi_4^*+5\Phi_5^*)$, $\cos(6\Phi_2^*+3\Phi_3^*-4\Phi_4^*-5\Phi_5^*)$, $\cos(\Phi_1^*-2\Phi_2^*-3\Phi_3^*+4\Phi_4^*)$, $\cos(\Phi_1^*+6\Phi_2^*-3\Phi_3^*-4\Phi_4^*)$, and $\cos(\Phi_1^*+2\Phi_2^*+3\Phi_3^*-6\Phi_6^*)$, which are also measurable. Experimental measurements of the corresponding reaction plane correlators in heavy ion collisions at RHIC and the LHC may improve our understanding of the physics underlying the measured higher order flow harmonics.Comment: 5 pages, 5 figure

Inconsistency of QED in the Presence of Dirac Monopoles

A precise formulation of $U(1)$ local gauge invariance in QED is presented, which clearly shows that the gauge coupling associated with the unphysical longitudinal photon field is non-observable and actually has an arbitrary value. We then re-examine the Dirac quantization condition and find that its derivation involves solely the unphysical longitudinal coupling. Hence an inconsistency inevitably arises in the presence of Dirac monopoles and this can be considered as a theoretical evidence against their existence. An alternative, independent proof of this conclusion is also presented.Comment: Extended and combined version, refinements added; 20 LaTex pages, Published in Z. Phys. C65, pp.175-18

The Ratio of Gluon Distributions in Sn and C

We calculate the ratio of gluon densities, G^Sn(x)/G^C(x), for 0.01<x<0.1, from the new high statistics data on F_2^Sn/F_2^C taken by the NM Collaboration. For small x, the shadowing in the gluon distribution is about equal to the shadowing of quark distribution. The antishadowing in the gluon distribution, however, is roughly 10%. We also compare with the ratio difference, R=sigma_L/sigma_T, from Sn and C.Comment: LaTeX, 9 page

η−η′\eta-\eta^\prime mixing and the next-to-leading-order power correction

The next-to-leading-order $O(1/Q^4)$ power correction for $\eta\gamma$ and $\eta^\prime\gamma$ form factors are evaluated and employed to explore the $\eta-\eta^\prime$ mixing. The parameters of the two mixing angle scheme are extracted from the data for form factors, two photon decay widths and radiative $J/\psi$ decays. The $\chi^2$ analysis gives the result: $f_{\eta_1}=(1.16\pm0.06)f_\pi, f_{\eta_8}=(1.33\pm0.23)f_\pi, \theta_1=-9^\circ\pm 3^\circ, \theta_8=-21.3^\circ\pm 2.3^\circ$, where $f_{\eta_{1(8)}}$ and $\theta_{1(8)}$ are the decay constants and the mixing angles for the singlet (octet) state. In addition, we arrive at a stringent range for $f_{\eta^\prime}^c:-10$ MeV$\le f_{\eta^\prime}^c\le -4$ MeV.Comment: 23 pages, 9 figures, To be publshied in Phys. Rev.

Nonperturbative Description of Deep Inelastic Structure Functions in Light-Front QCD

We explore the deep inelastic structure functions of hadrons nonperturbatively in an inverse power expansion of the light-front energy of the probe in the framework of light-front QCD. We arrive at the general expressions for various structure functions as the Fourier transform of matrix elements of different components of bilocal vector and axial vector currents on the light-front in a straightforward manner. The complexities of the structure functions are mainly carried by the multi-parton wave functions of the hadrons, while, the bilocal currents have a dynamically dependent yet simple structure on the light-front in this description. We also present a novel analysis of the power corrections based on light-front power counting which resolves some ambiguities of the conventional twist analysis in deep inelastic processes. Further, the factorization theorem and the scale evolution of the structure functions are presented in this formalism by using old-fashioned light-front time-ordered perturbation theory with multi-parton wave functions. Nonperturbative QCD dynamics underlying the structure functions can be explored in the same framework. Once the nonperturbative multi-parton wave functions are known from low-energy light-front QCD, a complete description of deep inelastic structure functions can be realized.Comment: Revtex, 30 pages and no figur

Jet Evolution in the Quark-Gluon Plasma from RHIC to the LHC

The observed suppression of high-$p_\perp$ hadrons allows different explanations. We discuss two possible scenarios: In scenario 1, parton energy loss from scattering in the hot medium is complemented by final state interactions in the resonance matter. Scenario 2 has an enhanced transport parameter $\hat q$ which is fitted to RHIC data. For LHC, the two scenarios lead to very different predictions for the nuclear modification factor of hadrons. In addition, jet reconstruction allows more specific tests of the mechanisms responsible for jet quenching. We calculate the distribution of partons inside a jet and find different results for the two scenarios.Comment: 25 pages, 6 figure

Fluctuating diamagnetism in underdoped high temperature superconductors

The fluctuation induced diamagnetism of underdoped high temperature superconductors is studied in the framework of the Lawrence-Doniach model. By taking into account the fluctuations of the phase of the order parameter only, the latter reduces to a layered XY-model describing a liquid of vortices which can be either thermally excited or induced by the external magnetic field. The diamagnetic response is given by a current-current correlation function which is evaluated using the Coulomb gas analogy. Our results are then applied to recent measurements of fluctuation diamagnetism in underdoped YBCO. They allow to understand both the observed anomalous temperature dependence of the zero-field susceptibility and the two distinct regimes appearing in the magnetic field dependence of the magnetization.Comment: 12 pages, 4 figures included, accepted for publication in PR

From GHz to mHz: A Multiwavelength Study of the Acoustically Active 14 August 2004 M7.4 Solar Flare

We carried out an electromagnetic acoustic analysis of the solar flare of 14 August 2004 in active region AR10656 from the radio to the hard X-ray spectrum. The flare was a GOES soft X-ray class M7.4 and produced a detectable sun quake, confirming earlier inferences that relatively low-energy flares may be able to generate sun quakes. We introduce the hypothesis that the seismicity of the active region is closely related to the heights of coronal magnetic loops that conduct high-energy particles from the flare. In the case of relatively short magnetic loops, chromospheric evaporation populates the loop interior with ionized gas relatively rapidly, expediting the scattering of remaining trapped high-energy electrons into the magnetic loss cone and their rapid precipitation into the chromosphere. This increases both the intensity and suddenness of the chromospheric heating, satisfying the basic conditions for an acoustic emission that penetrates into the solar interior.Comment: Accepted in Solar Physic

Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons

We report on the generation of coherent phonon polaritons in ZnTe, GaP and LiTaO$_{3}$ using ultrafast optical pulses. These polaritons are coupled modes consisting of mostly far-infrared radiation and a small phonon component, which are excited through nonlinear optical processes involving the Raman and the second-order susceptibilities (difference frequency generation). We probe their associated hybrid vibrational-electric field, in the THz range, by electro-optic sampling methods. The measured field patterns agree very well with calculations for the field due to a distribution of dipoles that follows the shape and moves with the group velocity of the optical pulses. For a tightly focused pulse, the pattern is identical to that of classical Cherenkov radiation by a moving dipole. Results for other shapes and, in particular, for the planar and transient-grating geometries, are accounted for by a convolution of the Cherenkov field due to a point dipole with the function describing the slowly-varying intensity of the pulse. Hence, polariton fields resulting from pulses of arbitrary shape can be described quantitatively in terms of expressions for the Cherenkov radiation emitted by an extended source. Using the Cherenkov approach, we recover the phase-matching conditions that lead to the selection of specific polariton wavevectors in the planar and transient grating geometry as well as the Cherenkov angle itself. The formalism can be easily extended to media exhibiting dispersion in the THz range. Calculations and experimental data for point-like and planar sources reveal significant differences between the so-called superluminal and subluminal cases where the group velocity of the optical pulses is, respectively, above and below the highest phase velocity in the infrared.Comment: 13 pages, 11 figure