Tue·Dec 4, 2018Tuesday·December 4, 2018

1. 01*

   Exotic decay channels are not the cause of the neutron lifetime anomaly

   D. Dubbers🇩🇪 · H. Saul🇩🇪 · B. Märkisch🇩🇪 · T. Soldner🇫🇷 · H. Abele🇦🇹

   Since long neutron lifetimes measured with a beam of cold neutrons are significantly different from lifetimes measured with ultracold neutrons bottled in a trap. It is often speculated that this "neutron anomaly" is due to an exotic dark neutron decay channel of unknown origin. We show that this explanation of the neutron anomaly can be excluded with a high level of confidence when use is made of new data on neutron decay parameters. Furthermore, data from neutron decay now compare well with Ft data derived from nuclear \b{eta} decays.

   nucl-exhep-exPLB(2019)·63 citations
2. 02*

   Some properties of the pT regions observed at the LHC energies

   Mais Suleymanov🇵🇰

   The inclusive spectra of the charged particles, ${\pi }^0$- and $\eta$-mesons produced in the pp collisions at LHC energies were analyzed . The data revealed several $p_T$ regions, which could be characterized by the length of the regions L and two free fitting parameters a and b. The study of the characteristics of the regions shown that the regions are divided into two groups. The values of the L and b for the first group don't depend on colliding energy and the properties of the particles (though the values of a increase linearly with energy), however, the second group regions' characteristics show strong dependencies. We found that the ratio of the eta-mesons to neutral pions lengths is approximately equal to the ratio of their masses. Assuming that the L values are directly proportional to the string tension, this result could be the evidence of parton string fragmentation dynamics, since in string theory the masses of elementary particles and their energy are defined by the intensity of string vibration . The increasing lengths for the eta-mesons' regions are accompanied with increasing values of b parameter. Taking into account that $Q^2\sim 1/b^2$ we have concluded that the eta-mesons were produced at lesser values of ${\alpha }_S$ compare to neutral pions. The results show that the lengths of the first group of regions are ~3-5 times greater than the lengths of neighboring lower pT regions. The second group's lengths are ~ 2 times greater than the lengths of neighboring lower pT region. In the framework of string fragmentation and hadronization dynamics, it could mean that the group I is produced through string decay into ~ 3-5 strings, whereas group II is produced through decay into ~2 strings. The existence of 2 groups of regions could hint to two types of strings responsible for the observed groups.

   nucl-exIJMPE(2019)·6 citations
3. 03*

   $\eta$ photoproduction off the deuteron and low-energy $\eta$-nucleon interaction

   S.X. Nakamura (Univ. Cruzeiro do Sul)🇧🇷 · H. Kamano (RCNP, Osaka Univ.)🇯🇵 · T. Ishikawa (ELPH, Tohoku Univ.)🇯🇵

   We study $\eta$ photoproduction off the deuteron ($\gamma d\to \eta pn$) at a special kinematics: $\sim 0.94$ GeV of the photon beam energy and $\sim 0^{\circ }$ of the scattering angle of the proton. This kinematics is ideal to extract the low-energy $\eta$-nucleon scattering parameters such as $a_{\eta N}$ (scattering length) and $r_{\eta N}$ (effective range) because the $\eta$-nucleon elastic scattering is significantly enhanced. We show that if a ratio $R$, the $\gamma d\to \eta pn$ cross section divided by the $\gamma p\to \eta p$ cross section convoluted with the proton momentum distribution in the deuteron, is measured with 5% error, $\mathrm{Re}[a_{\eta N}]$ ($\mathrm{Re}[r_{\eta N}]$) can be determined at the precision of $\sim \pm$0.1 fm ($\sim \pm$0.5 fm), significantly narrowing down the currently estimated range of the parameters. The measurement is ongoing at the Research Center for Electron Photon Science (ELPH), Tohoku University.

   ↳ nucl-thhep-phnucl-exJPS Conf.Proc.(2019)·0 citations
4. 04*

   Recent Progress in QCD Condensate Evaluations and Sum Rules

   Philipp Gubler🇯🇵 · Daisuke Satow🇯🇵

   We review the recent status of the QCD sum rule approach to study the properties of hadrons in vacuum and in hot or dense matter. Special focus is laid on the progress made in the evaluation of the QCD condensates, which are the input of all QCD sum rule calculations, and for which much new information has become available through high precision lattice QCD calculations, chiral perturbation theory and experimental measurements. Furthermore, we critically examine common analysis methods for QCD sum rules and contrast them with potential alternative strategies. The status of QCD sum rule studies investigating the modification of hadrons at finite density as well as recent derivations of exact sum rules applicable to finite temperature spectral functions, are also reviewed.

   ↳ hep-phhep-exhep-latnucl-ex+1PPNP(2019)·136 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.