Narrow Results

The probability of correlated emission of fluorescent photons as a function of detection directions has been investigated. The model system comprises identical two-level atoms arranged in the form of a line. A weak laser field resonantly excites only one of the atoms in the line. Two interaction mechanisms, namely, the vacuum-induced dipole–dipole interaction and the collective spontaneous emission couple the system of atoms. The aim is to observe the emission of a set of photon twins synchronized in time. It is seen that strongly directional emission of pairs of photons can take place due to the interference between the emitters. These highly correlated pairs of photons can be observed in very precise geometric directions. The observation is made based on two different detection procedures. It is found that the superradiant photons always tend to be bunched along the same direction.

Motivated by the first measurements of the experiment CMS at the LHC at and 2.36 TeV, we discuss energy dependence of average transverse momentum of the secondary particles in hadron production in pp-collisions. We suggest a possible explanation of this dependence as a result of collective rotation of the transient state and associate its further possible decrease with flattening off at higher energies with transition to the genuine QGP state of matter.

We consider collective effects in pp-collisions at the LHC energies related to presence of the large orbital angular momentum in the initial state and role of this orbital momentum in the elliptic flow behavior.

We briefly discuss the possible decoherence observed at the LHC emphasizing that the value of the average transverse momentum at can be interpreted as a manifestation of the deviation from the mechanism of the transient state of rotating matter.

We discuss a possible explanation of the double-ridge observation in pPb-collisions at the LHC emphasizing that this double structure in the two-particle correlation function can result from the rotation of the transient state of matter.

In this work, we calculate the expression for the potential due to neutrino–(anti)neutrino forward scattering at low energies $(E\ll m_{Z^0})$ for ultra-relativistic massive neutrinos $(E\gg m_{\nu })$, a representative regime within astrophysical scenarios. There is a broadly used expression for this potential in the literature, which, however, lacks an explicit derivation from basic principles of quantum field theory. Therefore, this paper has an intention to guide the reader through the steps and concepts to derive this potential, trying to be clear and pedagogical. Moreover, we used a rigorous approach concerning the massive nature of the neutrinos, using massive quantized neutrino fields throughout the entire process, while the usual approach is to consider massless neutrino fields at the interaction. In this context, we explicitly show the validity of the massless neutrino fields approximation at the ultra-relativistic regime, as expected. As the last step, we connect the potential expression to the density matrix formalism, which is a usual framework for works considering neutrino–neutrino interactions. We also discuss some theoretical details through the paper such as the normal ordering of quantum operators and the implications of massive fields in the neutrino state at its production.

The Super Tau-Charm Facility (STCF) proposed in China is a new-generation high-luminosity $e^{+}∕e^{-}$ collider in the low-energy region, with the beam energy of 1–3.5GeV and a target luminosity of larger than $5\times 10^{34}{\mathrm{\text{cm}}}^{-2}{\mathrm{\text{s}}}^{-1}$ at the optimized beam energy of 2GeV. Due to the limitations posed by the coherent X-Z instability and significant beam collective effects, the longitudinal beam dynamics are crucial for the STCF. This paper aims to introduce an iterative optimization model for the design of longitudinal beam dynamics in STCF. The model takes into account factors such as lattice design, coherent X-Z instability, and single-bunch collective effects. The analysis includes an estimation of the main collective instabilities and proposes corresponding mitigation strategies. This study will contribute to the further design optimization of the STCF collider rings.

Neutral short and long spheroidal cap clusters have been investigated within the liquid drop model. Analytical results have been obtained for the deformation-dependent surface and curvature energies. A large variety of experimentally determined shapes (both oblate and prolate) are explained by simulating the interaction energy with the substrate with a modified surface tension of the base, and by changing the missing or extended height of the cap, d. The results are illustrated for Na₅₆ and Na₁₄₈ atomic clusters.

We discuss collective effects in pp-collisions at the LHC energies and derive an upper bound for the anisotropic flow coefficients v_n. A possibility of its verification via comparison with the measurements of v₂ is considered. We use an assumption on the relation of the two-particle correlations with the rotation of the transient state of matter.

Many present and future storage-ring-based light sources make use of cavities at a harmonic of the main RF to lengthen the electron bunches. This reduces Touschek and intrabeam scattering to improve the beam lifetime and transverse emittances respectively. These harmonic cavities are also beneficial in increasing the threshold currents of many collective instabilities in both longitudinal and transverse planes. The latter case has previously been explored in detail making extensive use of Laclare’s eigenvalue method. Such an approach does not take into account the diffusion of head-tail modes of nonzeroth order, which is a consequence of the quantum-mechanical nature of synchrotron radiation. In this paper, we show that Laclare’s eigenvalue method is a change of basis from another popular method of solving the Sacherer formalism, where Fokker-Planck diffusion terms can be readily included. For the case of the MAX IV 3 GeV ring, it is found that the effect is a large increase in the threshold currents of the resistive-wall coupled-bunch instability at positive chromaticity.