Diffractive photoproduction of heavy quarks in hadronic collisions

In this letter we study the diffractive photoproduction of heavy quarks in hadronic (pp/pA/AA) interactions for Tevatron and LHC energies. The integrated cross section and rapidity distribution for the process h_1 h_2 --> h_1 h_2 QQBAR (h_i = p,A and Q = c,b) are estimated using the Color Glass Condensate (CGC) formalism. Our results indicate that this production channel has larger cross sections than the competing reactions of double diffractive production and coherent AA reactions initiated by two-photon collisions.Comment: 4 pages, 2 figures, 1 table. Version to be published in Physical Review

Detecting the Transverse Proximity Effect: Radiative Feedback from QSOs

We present results of a search for absorbers close to QSOs near the line of sight of background quasars based on sensitive Keck/HIRES observations of the QSO triplet KP76, KP77, and KP78 (z=2.466, 2.535, and 2.615), with separations of 2-3 arcmin on the plane plane of the sky. Through the use of a high resolution spectra, together with accurate systemic redshifts of the QSOs using near-IR spectroscopy, we quantify the state of the IGM gas at the redshifts of the foreground QSOs. The inferred ionizing flux at the proper transverse distances probed is up to 100 times greater than the UV background. We show that the state of the gas has been significantly affected by the UV radiation from the foreground QSOs

A note on the cylindrical collapse of counter-rotating dust

We find analytical solutions describing the collapse of an infinitely long cylindrical shell of counter-rotating dust. We show that--for the classes of solutions discussed herein--from regular initial data a curvature singularity inevitably develops, and no apparent horizons form, thus in accord with the spirit of the hoop conjecture.Comment: 8 pages, LaTeX, ijmpd macros (included), 1 eps figure; accepted for publication in Int. J. Mod. Phys.

Photoproduction of ρ0\rho^0 mesons in ultraperipheral heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC)

We investigate the photoproduction of $\rho$ mesons in ultraperipheral heavy ion collisions at RHIC and LHC energies in the dipole approach and within two phenomenological models based on the the Color Glass Condensate (CGC) formalism. We estimate the integrated cross section and rapidity distribution for meson production and compare our predictions with the data from the STAR collaboration. In particular, we demonstrate that the total cross section at RHIC is strongly dependent on the energy behavior of the dipole-target cross section at low energies, which is not well determined in the dipole approach. In contrast, the predictions at midrapidities at RHIC and in the full rapidity at LHC are under theoretical control and can be used to test the QCD dynamics at high energies.Comment: 6 pages, 5 figures, 1 table. Improved version to be published in Physical Review

No-horizon theorem for spacetimes with spacelike G1 isometry groups

We consider four-dimensional spacetimes $(M,{\mathbf g})$ which obey the Einstein equations ${\mathbf G}={\mathbf T}$, and admit a global spacelike $G_{1}={\mathbb R}$ isometry group. By means of dimensional reduction and local analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on ${\mathbf T}$ which guarantees that $(M,{\mathbf g})$ cannot contain apparent horizons. Given any (3+1) spacetime with spacelike translational isometry, the no-horizon condition can be readily tested without the need for dimensional reduction. This provides thus a useful and encompassing apparent horizon test for $G_{1}$-symmetric spacetimes. We argue that this adds further evidence towards the validity of the hoop conjecture, and signals possible violations of strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra

The QCD Pomeron in ultraperipheral heavy ion collisions: III. Photonuclear production of heavy quarks

We calculate the photonuclear production of heavy quarks in ultraperipheral heavy ion collisions. The integrated cross section and the rapidity distribution are computed employing sound high energy QCD formalisms as the collinear and semihard approaches as well as the saturation model. In particular, the color glass condensate (CGC) formalism is also considered using a simple phenomenological parameterization for the color field correlator in the medium, which allow us to obtain more reliable estimates for charm and bottom production at LHC energies.Comment: 15 pages, 2 figures. Extended version to be published in Eur. Phys. J.