Medium Modification of the Jet Properties

In the case that a dense medium is created in a heavy ions collision, high-E_t jets are expected to be broadened by medium-modified gluon emission. This broadening is directly related, through geometry, to the energy loss measured in inclusive high-p_t particle suppression. We present here the modifications of jet observables due to the presence of a medium for the case of azimuthal jet energy distributions and k_t-differential multiplicities inside the jets.Comment: 4 pages, 3 postscript figures. Proceedings for Quark Matter 200

Restriction on the energy and luminosity of e+e- storage rings due to beamstrahlung

The role of beamstrahlung in high-energy e+e- storage-ring colliders (SRCs) is examined. Particle loss due to the emission of single energetic beamstrahlung photons is shown to impose a fundamental limit on SRC luminosities at energies 2E_0 >~ 140 GeV for head-on collisions and 2E_0 >~ 40 GeV for crab-waist collisions. With beamstrahlung taken into account, we explore the viability of SRCs in the E_0=240-500 GeV range, which is of interest in the precision study of the Higgs boson. At 2E_0=240 GeV, SRCs are found to be competitive with linear colliders; however, at 2E_0=400-500 GeV, the attainable SRC luminosity would be a factor 15-25 smaller than desired.Comment: Latex, 5 pages. v2 differs only by minor changes is abstract and introduction, one reference is added. v3 corresponds to the paper published in PR

Jet multiplicities as the QGP thermometer

It is proposed to use the energy behavior of mean multiplicities of jets propagating in a nuclear medium as the thermometer of this medium during the collision phases. The qualitative effects are demonstrated in the framework of the fixed coupling QCD with account of jet quenching.Comment: Modify version of hep-ph/0509344, 3 figure

Hadron multiplicity in pp and AA collisions at LHC from the Color Glass Condensate

We provide quantitative predictions for the rapidity, centrality and energy dependencies of inclusive charged-hadron productions for the forthcoming LHC measurements in nucleus-nucleus collisions based on the idea of gluon saturation in the color-glass condensate framework. Our formulation gives very good descriptions of the first data from the LHC for the inclusive charged-hadron production in proton-proton collisions, the deep inelastic scattering at HERA at small Bjorken-x, and the hadron multiplicities in nucleus-nucleus collisions at RHIC.Comment: 7 pages, 8 figures; v3: minor changes, one reference added, results unchanged, the version to appear in Phys. Rev.

Laser cooling of electron beams for linear colliders

A novel method of electron beam cooling is considered which can be used for linear colliders. The electron beam is cooled during collision with focused powerful laser pulse. With reasonable laser parameters (laser flash energy about 10 J) one can decrease transverse beam emittances by a factor about 10 per one stage. The ultimate transverse emittances are much below those achievable by other methods. Beam depolarization during cooling is about 5--15 % for one stage. This method is especially useful for photon colliders and opens new possibilities for e+e- colliders.Comment: 4 pages, Latex, v2 corresponds to the PRL paper with erratum (in 1998) include

Non-Abelian Energy Loss at Finite Opacity

A systematic expansion in opacity, $L/\lambda$, is used to clarify the non-linear behavior of induced gluon radiation in quark-gluon plasmas. The inclusive differential gluon distribution is calculated up to second order in opacity and compared to the zeroth order (factorization) limit. The opacity expansion makes it possible to take finite kinematic constraints into account that suppress jet quenching in nuclear collisions below RHIC ($\sqrt{s}=200$ AGeV) energies.Comment: 4 pages (revtex) with 3 eps figures, submitted to PR

Young Measures Generated by Ideal Incompressible Fluid Flows

In their seminal paper "Oscillations and concentrations in weak solutions of the incompressible fluid equations", R. DiPerna and A. Majda introduced the notion of measure-valued solution for the incompressible Euler equations in order to capture complex phenomena present in limits of approximate solutions, such as persistence of oscillation and development of concentrations. Furthermore, they gave several explicit examples exhibiting such phenomena. In this paper we show that any measure-valued solution can be generated by a sequence of exact weak solutions. In particular this gives rise to a very large, arguably too large, set of weak solutions of the incompressible Euler equations.Comment: 35 pages. Final revised version. To appear in Arch. Ration. Mech. Ana

Thermal conductance of Andreev interferometers

We calculate the thermal conductance $G^T$ of diffusive Andreev interferometers, which are hybrid loops with one superconducting arm and one normal-metal arm. The presence of the superconductor suppresses $G^T$; however, unlike a conventional superconductor, $G^T/G^T_N$ does not vanish as the temperature $T\to0$, but saturates at a finite value that depends on the resistance of the normal-superconducting interfaces, and their distance from the path of the temperature gradient. The reduction of $G^T$ is determined primarily by the suppression of the density of states in the proximity-coupled normal metal along the path of the temperature gradient. $G^T$ is also a strongly nonlinear function of the thermal current, as found in recent experiments.Comment: 5 pages, 4 figure

Ultimate parameters of the photon collider at the ILC

At linear colliders, the e+e- luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs). While in gamma-gamma collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In present damping rings designs, nominal DR parameters correspond to those required for e+e- collisions. In this note, I would like to stress once again that as soon as we plan the photon-collider mode of ILC operation, the damping-ring emittances are dictated by the photon-collider requirements--namely, they should be as small as possible. This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential improvement of the gamma-gamma luminosity. No expert analysis exists as of yet, but it seems realistic to obtain a factor five increase of the gamma-gamma luminosity compared to the ``nominal'' DR design.Comment: Talk at LCWS06, Bangalore, India, March 2006, to be published in Indian Journal of Physics, 5 pp, Latex, 1 .eps figur

Efficient computation of matched solutions of the Kapchinskij-Vladimirskij envelope equations for periodic focusing lattices

A new iterative method is developed to numerically calculate the periodic, matched beam envelope solution of the coupled Kapchinskij-Vladimirskij (KV) equations describing the transverse evolution of a beam in a periodic, linear focusing lattice of arbitrary complexity. Implementation of the method is straightforward. It is highly convergent and can be applied to all usual parameterizations of the matched envelope solutions. The method is applicable to all classes of linear focusing lattices without skew couplings, and also applies to all physically achievable system parameters -- including where the matched beam envelope is strongly unstable. Example applications are presented for periodic solenoidal and quadrupole focusing lattices. Convergence properties are summarized over a wide range of system parameters.Comment: 20 pages, 5 figures, Mathematica source code provide