We study the classical dynamics of the Abelian Higgs model employing an asymptotic multiscale expansion method, which uses the ratio of the Higgs to the gauge field amplitudes as a small parameter. We derive an effective nonlinear Schrödinger equation for the gauge field, and a linear equation for the scalar field containing the gauge field as a nonlinear source. This equation is used to predict the existence of oscillons and oscillating kinks for certain regimes of the ratio of the Higgs to the gauge field masses. Results of numerical simulations are found to be in very good agreement with the analytical findings, and show that the oscillons are robust, while kinks are unstable. It is also demonstrated that oscillons emerge spontaneously as a result of the onset of the modulational instability of plane wave solutions of the model. Connections of the obtained solutions with the phenomenology of superconductors is discussed.

Considering the 3d Ising universality class of the QCD critical endpoint we use a universal effective action for the description of the baryon-number density fluctuations around the critical region. Calculating the baryon-number multiplicity moments and determining their scaling with system's size we show that the critical region is very narrow in the direction of the baryon chemical potential µ and wide in the temperature direction T for T > Tc. In this context, published experimental results on local proton density-fluctuation measurements obtained by intermittency analysis in transverse momentum space in NA49 central A+A collisions at √ sNN = 17.2 GeV (A=C,Si,Pb), restrict significantly the location (µc, Tc) of the QCD critical endpoint. The main constraint is provided by the freeze-out chemical potential of the Si+Si system, which shows non-conventional baryon density fluctuations, restricting (µc, Tc) within a narrow domain, 119 MeV ≤ Tc ≤ 162 MeV, 252 MeV ≤ µc ≤ 258 MeV, of the phase diagram.

We study the classical dynamics of the Abelian-Higgs model in (1+1) space-time dimensions for the case of strongly broken gauge symmetry. In this limit the wells of the potential are almost harmonic and sufficiently deep, presenting a scenario far from the associated critical point. Using a multiscale perturbation expansion, the equations of motion for the fields are reduced to a system of coupled nonlinear Schrödinger equations (CNLS). Exact solutions of the latter are used to obtain approximate analytical solutions for the full dynamics of both the gauge and Higgs field in the form of oscillons and oscillating kinks. Numerical simulations of the exact dynamics verify the validity of these solutions. We explore their persistence for a wide range of the model's single parameter which is the ratio of the Higgs mass (mH) to the gauge field mass (mA). We show that only oscillons oscillating symmetrically with respect to the "classical vacuum", for both the gauge and the Higgs field, are long lived. Furthermore plane waves and oscillating kinks are shown to decay into oscillon-like patterns, due to the modulation instability mechanism.

We investigate Non-Linear Plane-Wave solutions of the classical Minkowskian Yang-Mills (YM) equations of motion. By imposing a suitable ansatz which solves Gauss' law for the SU (3) theory, we derive solutions which consist of Jacobi elliptic functions depending on an enumerable set of elliptic modulus values. The solutions represent periodic anharmonic plane waves which possess arbitrary non-zero mass and are exact extrema of the non-linear YM action. Among them, a unique harmonic plane wave with a non-trivial pattern in phase, spin and color is identified. Similar solutions are present in the SU (4) case while are absent from the SU (2) theory.

We consider the prompt photon production in pp collisions using, within the framework of perturbative QCD, a non-gaussian distribution for the transverse momentum distribution of the partons inside the proton. Our description adopts the widely used in the literature factorization of the partonic momentum distribution into longitudinal and transverse components. It is argued that the non-gaussian distribution of the intrinsic transverse momenta of the partons is dictated by the asymptotic freedom as well as the 3D confinement of the partons in the proton. To make this association more transparent we use the MIT bag model, which plainly incorporates both properties (asymptotic freedom, confinement), in order to determine in a simplified way the partonic transverse momentum distribution. A large set of data from 6 different experiments have been fitted with this simple description using as a single free parameter the mean partonic transverse momentum kT . Surprisingly enough, a perfect fit of the experimental data turns out to require kT values which are compatible with Heisenberg's uncertainty relation for the proton and decrease almost smoothly as a function of the scaled variable z = p T √ s , where pT is the transverse momentum of the final photon and √ s is the beam energy in the center of mass frame. Our analysis indicates that asymptotic freedom and 3D confinement may influence significantly the form of the partonic transverse momentum distribution leaving an imprint on the pp → γ + X cross section.PACS numbers: 13.60. Le,13.85.Ni,12.38.Qk The production of photons with large transverse momentum is an excellent probe of the dynamics in hard scattering processes [1,2]. In particular, the study of direct photon production possesses numerous and well known advantages, both theoretical and experimental [2][3][4][5][6][7][8][9]. In the latter case the main advantage is that photons are easier to detect than jets. From the theoretical point of view the main advantage is the simplicity of the process allowing for an accurate determination of the gluon distribution within the proton. In the lowest order (O(αα s )) only two subprocesses, gq → γq (Compton) and qq → γg (annihilation), contribute to high p T photons. Their characteristic signature is the production of a photon isolated from the hadrons in the event, accompanied by a kinematically balancing high-p T jet appearing on the opposite site. In the next-to-leading order (NLO) the process associated with the production of a photon coming from the collinear fragmentation of a hard parton produced in a short-distance subprocess, constitutes a background to the direct photon production of the same order in α s as the corresponding Born level terms [10] provided that the fragmentation scale is large enough. However, the contribution from fragmentation remains small (less than 10%) for fixed target experiments and becomes significant only in inclusive prompt photon production at higher collider energies [10]. Recently there has been observed a systematic disagreeme...