Wed·Apr 22, 2020Wednesday·April 22, 2020

1. 01*

   Anomaly in decay of 8Be and 4He -- can an observed light boson mediate low energy nucleon-nucleon interactions ?

   M. Veselsky🇨🇿 · V. Petousis🇨🇿 · J. Leja🇸🇰

   We present a hypothesis that the anomaly in the folding angle distribution of electron-positron pairs, emitted in the decay of the excited levels of nucleus ${}^8$Be and ${}^4$He can be related to the cluster structure of the decaying state. Furthermore, we present a hypothesis that the potentially observed boson with re st mass $m_X$=17 MeV can mediate the nucleon-nucleon interaction at the low-energy regime of QCD, in particular in the weakly bound cluster state p+${}^7$Li,${}^3$H. We present a possible equations of state of symmetric nuclear matter corresponding to the vector meson mass $m_v$=17 MeV, obtained using relativistic mean field theory of nuclear force, QHD-I in particular, with physically relevant incompessibility K${}_0$=240-260 MeV and the values of couplings $g_v$, $g_s$ lower than unity. Based on concepts of chiral symmetry breaking, we show that reduction of the rest mass of pseudoscalar particle from physical value $m_{\pi }$=135 MeV to $m_X$=17 MeV is equivalent to reduction of the quark mass from dynamical value around 310 MeV down to current quark mass around 5 MeV ($\frac{m_X^2}{m_{q,curr}}\simeq \frac{m_{\pi }^2}{m_{q,dyn}}$). Corresponding version of Goldberger-Treiman relation leads to the value of coupling close to the results from relativistic mean field theory of nuclear force. Both model approaches thus point towards apparent restoration of chiral symmetry in nucleon-nucleon interaction at large distances, possibly via bounce into false instanton vacuum. Observation of boson with rest mass $m_X$=17 MeV in the decay of high lying excited states of ${}^8$Be and ${}^4$He can possibly resolve one of the longest lasting open questions in nuclear physics.

   ↳ nucl-thhep-phnucl-exJ.Phys.G(2021)·10 citations
2. 02*

   Skewness of mean transverse momentum fluctuations in heavy-ion collisions

   Giuliano Giacalone🇫🇷 · Fernando G. Gardim🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jean-Yves Ollitrault🇫🇷

   We propose the skewness of mean transverse momentum, $⟨p_t⟩$, fluctuations as a fine probe of hydrodynamic behavior in relativistic nuclear collisions. We describe how the skewness of the $⟨p_t⟩$ distribution can be analyzed experimentally, and we use hydrodynamic simulations to predict its value. We predict in particular that $⟨p_t⟩$ fluctuations have positive skew, which is significantly larger than if particles were emitted independently. We elucidate the origin of this result by deriving generic formulas relating the fluctuations of $⟨p_t⟩$ to the fluctuations of the early-time thermodynamic quantities. We postulate that the large positive skewness of $⟨p_t⟩$ fluctuations is a generic prediction of hydrodynamic models.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2021)·52 citations
3. 03*

   New approach to search for parity-even and parity-odd time-reversal violation beyond the Standard Model in a storage ring

   N.N. Nikolaev🇷🇺 · F. Rathmann🇩🇪 · A.J. Silenko🇷🇺 · Yu. Uzikov🇷🇺

   Time-reversal breaking and parity-conserving millistrong interactions, suggested in 1965, still remain a viable mechanism of CP-violation beyond the Standard Model. One of its possible manifestations is the T-odd asymmetry in the transmission of tensor-polarized deuterons through a vector-polarized hydrogen gas target. Upon the rotation of the deuteron polarization from the vertical direction into the ring plane, the T-odd asymmetries, odd against the reversal of the proton polarization in the target, will continuously oscillate with first or second harmonics of the spin precession frequency. The Fourier analysis of the oscillating T-odd asymmetries allows for an easy separation from background persistent in conventional experiments employing static vector and tensor polarizations.

   ↳ nucl-thhep-exhep-phnucl-ex+1PLB(2020)·20 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.