Polarization mesurements of gamma ray bursts and axion like particles

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of axion like particles (ALPs). Based on evidences of polarized gamma ray emission detected in several gamma ray bursts we estimated the level of ALPs induced dichroism, which could take place in the magnetized fireball environment of a GRB. This allows to estimate the sensitivity of polarization measurements of GRBs to the ALP-photon coupling. This sensitivity \gag\le 2.2\cdot 10^{-11} {\rm GeV^{-1}} calculated for the ALP mass $m_a=10^{-3}~{\rm eV}$ and MeV energy spread of gamma ray emission is competitive with the sensitivity of CAST and becomes even stronger for lower ALPs masses.Comment: Contribution to Proc. 4th Patras Workshop on Axions, WIMPs and WISPs (18-21 June 2008, DESY

Minimal Length Scale in Annihilation

Experimental data suggest the existence of a minimal length scale in annihilation process for the reaction e+e- --> gamma gamma (gamma). Nonlinear electrodynamics coupled to gravity and satisfying the weak energy condition predicts, for an arbitrary gauge invariant lagrangian, the existence of a spinning charged electromagnetic soliton asymptotically Kerr-Newman for a distant observer with a gyromagnetic ratio g=2. Its internal structure includes an equatorial disk of de Sitter vacuum which has properties of a perfect conductor and ideal diamagnetic, and displays superconducting behavior within a single spinning soliton. De Sitter vacuum supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry. We apply this approach to interpret the existence of a minimal characteristic length scale in annihilation.Comment: 16 pages, 3 figure

Relating multihadron production in hadronic and nuclear collisions

The energy-dependence of charged particle mean multiplicity and pseudorapidity density at midrapidity measured in nucleus-nucleus and (anti)proton-proton collisions are studied in the entire available energy range. The study is performed using a model, which considers the multiparticle production process according to the dissipating energy of the participants and their types, namely a combination of the constituent quark picture together with Landau relativistic hydrodynamics. The model reveals interrelations between the variables under study measured in nucleus-nucleus and nucleon-nucleon collisions. Measurements in nuclear reactions are shown to be well reproduced by the measurements in (anti)proton-proton interactions common and the corresponding fits are presented. Different observations in other types of collisions are discussed in the framework of the proposed model. Predictions are made for measurements at the forthcoming LHC energies.Comment: Europ. Phys. J. C (to appear). Recently CMS reported (arXiv:1005.3299) on the midrapidity density value of 5.78 +/- 0.01(stat) +/- 0.23(syst) in pp collisons at 7 TeV, which agrees well with the value of 5.8 of our prediction

Antimatter regions in the baryon-dominated Universe

Quantum fluctuations of a complex, baryonic charged scalar field caused by inflation can generate large domains, which convert later into antimatter regions. As a result the Universe can become globally matter-dominated, with minor contribution of antimatter regions. The distribution and evolution of such antimatter regions could cause every galaxy to be a harbour of an anti-star globular cluster. At the same time, the scenario does not lead to large-scale isocuvature perturbations, which would disturb observable CMB anisotropy. The existence of one of such antistar globular cluster in our Galaxy does not contradict the observed $\gamma$-ray background, but the expected fluxes of $\bar{\rm ^4He}$ and $\bar{\rm ^3He}$ from such an antimatter object are definitely accessible to the sensitivity of the coming AMS--02 experiment.Comment: Talk given at the XIVth Rencontres de Blois 2002 on Matter-Antimatter Asymmetry, Blois, France, June, 2002, to be published in the proceedings, ed. J. Tran Thanh Van, 4 latex pages, 2 eps figure

Possible Origin of Antimatter Regions in the Baryon Dominated Universe

We discuss the evolution of U(1) symmetric scalar field at the inflation epoch with a pseudo Nambu-Goldstone tilt revealing after the end of exponential expansion of the Universe. The U(1) symmetry is supposed to be associated with baryon charge. It is shown that quantum fluctuations lead in natural way to baryon dominated Universe with antibaryon excess regions. The range of parameters is calculated at which the fraction of Universe occupied by antimatter and the size of antimatter regions satisfy the observational constraints, survive to the modern time and lead to effects, accessible to experimental search for antimatter.Comment: 10 pages, 1 figur