Antiparticle Production Research Articles

The concept of the massive photon and its astrophysical implications

We discuss the concept of the massive photon with its possible implications in astrophysics. We use the term ”mass equivalent” instead of relativistic or effective mass. We also analyzed modified Planck’s law and estimated (mean mass/rest mass) ratio in connection to the temperature of blackbody radiation of the massive photons. This ratio diverges at high temperatures and approaches unity at low temperatures. The ”mass equivalent” for the CMB radiation was estimated to be equal to 0.0468% of the total mass of the Universe. We have discussed importance of the Breit-Wheeler process of particle – antiparticle production in the early Universe. We have evaluated the upper limit of the rest mass of the photon using gravitational and cosmological redshifts. A correlation was found between estimated masses of the photon and the lowest/highest frequencies of the spectral bands used for estimation of the mass.

Entanglement in model-independent cosmological scenario

We propose a model-independent approach to study entanglement creation due to the dynamics between two asymptotic quantum regimes in the framework of homogeneous and isotropic universe. We realize it by Padé expansion to reconstruct the functional form of scale factor, rather than postulating it a priori. This amounts to fix the Padé approximants constraining the free parameters in terms of current cosmic observations. Assuming fermions, we solve the Dirac equation for massive particles and we investigate entanglement entropy in terms of modes [Formula: see text] and mass [Formula: see text]. We consider two rational approximations of [Formula: see text] and [Formula: see text] orders, which turn out to be the most suitable choices for guaranteeing cosmic bounds. Our results show qualitative agreement with those known in literature and arising from toy models, but with sensible quantitative discrepancies. Moreover, our outcomes are model-independent reconstructions which show that any higher orders departing from [Formula: see text] do not significantly modify particle–antiparticle production (hence entanglement), if cosmic bounds are taken into account.

Equilibration in fermionic systems

The time evolution of a finite fermion system towards local statistical equilibrium is investigated using analytical solutions of a nonlinear partial differential equation that had been derived earlier from the Boltzmann collision term. The solutions of this fermionic diffusion equation are rederived in closed form, evaluated exactly for simplified initial conditions, and applied to hadron systems at low energies in the MeV-range, as well as to quark systems at relativistic energies in the TeV-range where antiparticle production is abundant. Conservation laws for particle number including created antiparticles, and for the energy are discussed.

Relieving the Tension between Dark Matter Production of High-energy Cosmic Antiparticles and FERMI/LAT Constraint on Isotropic Diffuse Gamma-ray Background

The dark matter explanation of both cosmic ray positron and antiproton excesses, seen by PAMELA and recently confirmed by AMS-02, inevitably faces the contradiction with the latest FERMI/LAT data on isotropic diffuse gamma-ray background (IGRB). Here we discuss a possible solution to this problem, based on the accumulation of self-interacting dark matter component in the Galactic disk. For the same purpose, the mechanism of high-energy antiparticle production in the collisions of high-energy particles with matter can also be suggested.

Flux of antinucleons induced by cosmic rays in the atmosphere

This work is devoted to the calculation of the fluxes of the atmospheric antiprotons and antineutrons generated at various atmospheric depths, lying from 5 to 300 g/cm2. The simulations are carried out with the help of CORSIKA package involving a primary energy spectrum starting at the energy threshold of antiparticle production up to 1 PeV. The obtained results match well with the atmospheric antiproton spectra measured by the BESS-2001 experiment in the kinetic energy range 1-3 GeV.

Relativistic confinement of neutral fermions with a trigonometric tangent potential

The problem of neutral fermions subject to a pseudoscalar potential is investigated. Apart from the solutions for E = ±mc2, the problem is mapped into the Sturm–Liouville equation. The case of a singular trigonometric tangent potential (∼tan γx) is exactly solved and the complete set of solutions is discussed in some detail. It is revealed that this intrinsically relativistic and true confining potential is able to localize fermions into a region of space arbitrarily small without the menace of particle–antiparticle production.

Multistrange baryon production in relativistic heavy ion collisions

Using a multiphase transport model, we study the production of multistrange (anti)baryons from the hadronic matter formed in relativistic heavy ion collisions. The mechanism we introduce is the strangeness-exchange reactions between antikaons and hyperons for strange particle production and between kaons and antihyperons for strange antiparticle production. We find that these reactions contribute significantly to the production of multistrange baryons and antibaryons in heavy ion collisions at SPS energies, which has been found to be appreciably enhanced. We have also made predictions for multistrange baryon and antibaryon production in heavy ion collisions at RHIC and found a similar enhancement. The (anti)particle mass dependence of inverse slope parameters extracted from their transverse mass spectra in the transport model exhibit similar trend as in the available experimental data at both SPS and RHIC energies.

Asymmetries in the production of Λ0 in 250 GeV/cπ±, K± and p–nucleon interactions

Using data from Fermilab fixed-target experiment E769, we have measured particle–antiparticle production asymmetries for Λ0 hyperons in 250 GeV/cπ±, K± and p–nucleon interactions. The asymmetries are measured as functions of Feynman-x (xF) and pT2 over the ranges −0.12⩽xF⩽0.12 and 0⩽pT2⩽3 (GeV/c)2 (for positive beam) and −0.12⩽xF⩽0.4 and 0⩽pT2⩽10 (GeV/c)2 (for negative beam). We find substantial asymmetries, even at xF around zero. We also observe leading-particle-type asymmetries. These latter effects are qualitatively as expected from valence-quark content of the target and variety of projectiles studied.

Asymmetries in the production of Λ0, Ξ−, and [formula omitted] hyperons in 500 GeV/ cπ−–nucleon interactions

Using data from Fermilab fixed-target experiment E791, we have measured particle–antiparticle production asymmetries for Λ 0, Ξ −, and Ω − hyperons in π −–nucleon interactions at 500 GeV/ c. The asymmetries are measured as functions of Feynman- x ( x F ) and p T 2 over the ranges −0.12⩽ x F ⩽0.12 and 0⩽ p T 2⩽4 (GeV/ c) 2. We find substantial asymmetries, even at x F =0. We also observe leading-particle-type asymmetries which qualitatively agree with theoretical predictions.

$D^\pm}$ and $D^0(\bar{D}^0)$ production asymmetries in $\pi p$ collisions

We use a two-component model to describe the production mechanism of $D$ mesons in $\pi p$ collisions. The model combines the usual QCD processes plus fragmentation and recombination of charm that has been produced by nonperturbative QCD mechanisms. A hard charm component in the pion must be responsible of the particle anti-particle production asymmetries observed.

$D^\pm}$

We use a two-component model to describe the production mechanism of D mesons in pi-p collisions. The model combines the usual QCD processes plus fragmentation and recombination of charm that has been produced by nonperturbative QCD mechanisms. A hard charm component in the pion must be responsible of the particle anti-particle production asymmetries observed.

Strangelet search and particle production studies in Pb+Pb collisions at 158 AGeV/c at CERN SPS

We searched for long-lived strange quark matter particles, so-calledstrangelets, and studied particle and antiparticle production in Pb+Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c 2 and lifetimest lab>1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

Strangelet search and antinuclei production studies in Pb + Pb collisions

We searched for long-lived strange quark matter particles, so-called strangelets, and studied particle and antiparticle production in Pb + Pb collisions at 158 GeV/ c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/ c 2 and lifetimes t lab > 1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

Inclusive production ofK *(892) andΣ(1385) in $$\bar p$$ p interactions at 3.6 GeV/c and a test of factorization hypothesis

We present a study of the inclusive production ofK*(892) and ∑t+-(1385)+cc at 3.6 GeV/c from\(\bar p\)p interactions. The sensitivity of the exposure is 35.4 events/μb. Longitudinal and transverse momentum distributions are presented. The indirect production ofK s 0 from parentK* and that of Λ's from parent Σ(1385) are studied. The shape of thex distribution of Λ's for\(p\xrightarrow{{\bar p}}\Lambda \) are calculated from\(p\xrightarrow{p}\Lambda \) and\(p\xrightarrow{{\pi ^ - }}\Lambda \) and compared with the experimental distributions. The difference of antiparticle production cross-section ofK s 0 in the central region is compared with the expectation from Mueller-Regge formalism.

Particle and antiparticle production by 200 GeV/c protons in the charged hyperon beam at the CERN SPS

A charge hyperon beam has been brought into operation at the CERN SPS. Particles are identified by a DISC Čerenkov counter, and decay products are analysed by a magnetic spectrometer. Cross sections for the inclusive production of π + , K + , p , Σ + , Σ − , ζ − , d, and π − , K − , p , Σ + , Σ − , ζ − , ω − , d in the forward direction have been measured at laboratory momenta between 70 and 130 GeV/ c . This range of momenta corresponds to 0.35 ⩽ x ⩽ 0.66 for an incident proton momentum of 200 GeV/ c . Antihyperon ( Σ − , ζ − , Σ + ) and Σ + and ω − fluxes have been measured for the first time in a hyperon beam. Scaling behaviour is observed when the data are compared with the results from other experiments. The inclusive particle production cross sections have a (1 − x ) n dependence, where n is characteristics of the particle. A search has been made for new particles in the mass range 2–10 GeV/ c 2 . No evidence is found for such particles.

Particle and antiparticle production by 200 GeV/ c protons in the charged hyperon beam at the CERN SPS

A charge hyperon beam has been brought into operation at the CERN SPS. Particles are identified by a DISC Čerenkov counter, and decay products are analysed by a magnetic spectrometer. Cross sections for the inclusive production of π +, K +, p, Σ +, Σ − , ζ − , d, and π −, K −, p , Σ + , Σ −, ζ −, ω −, d in the forward direction have been measured at laboratory momenta between 70 and 130 GeV/ c. This range of momenta corresponds to 0.35 ⩽ x ⩽ 0.66 for an incident proton momentum of 200 GeV/ c. Antihyperon ( Σ − , ζ − , Σ + ) and Σ + and ω − fluxes have been measured for the first time in a hyperon beam. Scaling behaviour is observed when the data are compared with the results from other experiments. The inclusive particle production cross sections have a (1 − x) n dependence, where n is characteristics of the particle. A search has been made for new particles in the mass range 2–10 GeV/ c 2. No evidence is found for such particles.