Novel subjet observables for jet quenching in heavy-ion collisions

Using a novel observable that relies on the momentum difference of the two most energetic subjets within a jet \(\varDelta S_{12}\) we study the internal structure of high-energy jets simulated by several Monte Carlo event generators that implement the partonic energy-loss in a dense partonic medium. Based on inclusive jet and dijet production we demonstrate that \(\varDelta S_{12}\) is an effective tool to discriminate between different models of jet modifications over a broad kinematic range. The new quantity, while preserving the collinear and infrared safety of modern jet algorithms, it is experimentally attractive because of its inherent resilience against backgrounds of heavy-ion collisions.     

Consequences of temperature fluctuations in observables measured in high-energy collisions

We review the consequences of intrinsic, nonstatistical temperature fluctuations as seen in observables measured in high-energy collisions. We do this from the point of view of nonextensive statistics and Tsallis distributions. Particular attention is paid to multiplicity fluctuations as a first consequence of temperature fluctuations, to the equivalence of temperature and volume fluctuations, to the generalized thermodynamic fluctuations relations allowing us to compare fluctuations observed in different parts of the phase space, and to the problem of the relation between Tsallis entropy and Tsallis distributions. We also discuss the possible influence of conservation laws on these distributions and provide some examples of how one can get them without considering temperature fluctuations.     

Novel jet quenching observables in heavy ion collisions at the LHC

We discuss such novel jet quenching observables at the LHC as direct measurements of medium-modified jet fragmentation function, nuclear modification factor and azimuthal anisotropy for jets with finite cone size and p _T -imbalance for dimuon tagged jets. The corresponding predictions obtained with PYQUEN partonic energy loss model are presented.     

Dispersive shock waves with nonlocal nonlinearity

We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.     

Solitary wave solutions of nonlocal sine-Gordon equations

In this paper a nonlocal generalization of the sine-Gordon equation, u(tt)+sin u=( partial differential / partial differential x) integral (- infinity ) (+ infinity )G(x-x('))u(x(') )(x('),t)dx(') is considered. We present a brief review of the applications of such equations and show that involving such a nonlocality can change features of the model. In particular, some solutions of the sine-Gordon model (for example, traveling 2pi-kink solutions) may disappear in the nonlocal model; furthermore, some new classes of solutions such as traveling topological solitons with topological charge greater than 1 may arise. We show that the lack of Lorenz invariancy of the equation under consideration can lead to a phenomenon of discretization of kink velocities. We discussed this phenomenon in detail for the special class of kernels G(xi)= summation operator (j=1) (N)kappa(j)e(-eta(j)mid R:ximid R:), eta(j)>0, j=1,2, em leader,N. We show that, generally speaking, in this case the velocities of kinks (i) are determined unambiguously by a type of kink and value(s) of kernel parameter(s); (ii) are isolated i.e., if c(*) is the velocity of a kink then there are no other kink solutions of the same type with velocity c in (c(*)- varepsilon,c(*)+ varepsilon ) for a certain value of varepsilon. We also used this special class of kernels to construct approximations for analytical and numerical study of the problem in a more general case. Finally, we set forth results of the numerical investigation of the problem with the kernel that is the McDonald function G(xi) approximately K(0)(mid R:ximid R:/lambda) (lambda is a parameter) that have applications in the Josephson junction theory. (c) 1998 American Institute of Physics.     

Phase modulations due to collisions of beam pairs in nonlocal nonlinear media

In this paper, discussed is the evolution of two co-propagating optical beams in parallel in nonlocal Kerr media, governed by the nonlocal nonlinear Schrödinger equation (NNLSE). A simplified model to the NNLSE is presented when the media is strongly nonlocal, which is a bridge between the Snyder–Mitchell model (Snyder and Mitchell Science 276 1538, 1997) and the strongly-nonlocal model (Guo, Luo, Yi, Chi, and Xie Phys. Rev. E. 69 016602, 2004). It is found that when one of the soliton beams is much stronger than the other, the weaker (probe beam) can experience $\pi $ nonlinear phase shift, which can be modulated by the stronger (pump beam), within a rather short propagation distance (about 40-m). The comparisons of analytical solutions of the model with numerical simulations of the NNLSE show that the model is of excellent accuracy in the case of strong nonlocality.     

Cold collisions in strong laser fields: partial wave analysis of magnesium collisions

We have developed Monte Carlo wave function simulation schemes to study cold collisions between magnesium atoms in a strong red-detuned laser field. In order to address the strong-field problem, we extend the Monte Carlo wave function framework to include the partial wave structure of the three-dimensional system. The average heating rate due to radiative collisions is calculated with two different simulation schemes which are described in detail. We show that the results of the two methods agree and give estimates for the radiative collision heating rate for ²⁴Mg atoms in a magneto-optical trap based on the ¹S₀–¹P₁ atomic laser cooling transition.     

Influence of then-n cross section on the observables in dynamical process of heavy ion collisions

The influence of then- n cross section on the observables in dynamical process of heavy ion collisions was investigated by means of the BUU (Boltzmann-Uehling-Uhlenbeck) equation. The influence of then-n cross section upon transverse momentum, flow angle and quadrupole moment of momentum distribution with increasing incident energy was successfully illustrated according to the variation law ofn-n cross section with and without the medium effects with increasing bombarding energy. This investigation also shows a close relationship between the medium effects of then- n cross section and the nuclear equation of state (EOS).     

Dependence of flow observables in heavy-ion collisions on the symmetry energy and the in-medium nucleon-nucleon interaction

We employ a QMD transport model to study the influence of the isospin dependent part of the nuclear matter equation of state on the dynamics of heavy-ion collisions at intermediate energies. Parametrization of the in-medium dependence of the nucleon-nucleon elastic cross-sections, as predicted by microscopical models, are used. The sensitivity of flow observables to various parametrizations of the isospin dependent part of the equation of state (symmetry energy) is studied. The experimentally observed splitting of the elliptic flow values in Ru+Zr and Zr+Ru at incident energies of 400 MeV is shown to be due to, to an equal extent, density dependence of the microscopic nucleon-nucleon cross-section and symmetry energy.     

Computation of NMR observables: Consequences of projector-augmented wave sphere overlap

The assumptions underlying the popular projector-augmented wave (PAW) method of computing electronic structure in solids are examined, with primary attention to the computation of NMR observables. In particular, the assumption of non-overlapping PAW spheres is studied, and it is shown that when the spheres do overlap, the errors may be significant and furthermore are of unpredictable sign. Examples are provided by comparing PAW-based calculations with and without overlapping spheres, with the highly accurate all-electron linear augmented wave method.     

放射性束引起的重离子碰撞中敏感于对称能的几个观测量

利用同位旋与动量相关的强子输运模型，我们研究了放射性束引起的中能重离子碰撞中几个观测量的对称能效应。我们发现自由核子发射的非对称度的快度分布，中快度中－质比的横动量分布，的动能分布，以及同位旋相分化（fractionation）的时间演化都敏感于对称能。     

Matter wave soliton collisions in the quasi one-dimensional potential

We consider soliton solutions of a two-dimensional nonlinear system with the self-focusing nonlinearity and a quasi 1D confining potential, taking harmonic potential as an example. We investigate a single soliton in detail and find criterion for possible collapse. This information is then used to investigate the dynamics of the two soliton collision. In this dynamics we identify three regimes according to the relation between nonlinear interaction and the excitation energy: elastic collision, excitation and collapse regime. We show that surprisingly accurate predictions can be obtained from variational analysis.     

Measurement of scaling laws for shock waves in thermal nonlocal media

We are able to detect the details of spatial optical collisionless wave breaking through the high aperture imaging of a beam suffering shock in a fluorescent nonlinear nonlocal thermal medium. This allows us to directly measure how nonlocality and nonlinearity affect the point of shock formation and compare results with numerical simulations.