Wed·Apr 5, 2023Wednesday·April 5, 2023

1. 01*

   Anomalies in Particle Physics

   Andreas Crivellin🇨🇭

   I provide a (personal) review of the current hints for physics beyond the Standard Model, called ``anomalies'', obtained both at the intensity frontier (flavour and electroweak precision observables) and in direct LHC searches. This includes the deviations from the Standard Model predictions in semi-leptonic $B$ decays, the anomalous magnetic moment of the muon, the Cabibbo Angle Anomaly, the $W$ mass as well as non-resonant di-lepton searches, the hints for new scalar particles around $\approx 95$GeV, $\approx 151$GeV, $\approx 670$GeV and the (di-)di-jet excess at $\approx 1$TeV ($\approx 3.6$TeV). Possible explanations in terms of new particles are briefly summarized and discussed.

   ↳ hep-phhep-exhep-latnucl-ex+1PoS(2024)·8 citations
2. 02*

   Investigation of the cause of the discrepancies between calculated running sums for nuclear matrix elements of two-neutrino double-$\beta$ decay

   J. Terasaki🇨🇿

   A qualitative difference in the running sum for the nuclear matrix element of the two-neutrino double-$\beta$ decay of ${}^{136}$Xe was found four years ago between quasiparticle random-phase approximation (QRPA) and shell model calculations. The former result has large increase and decrease with respect to the excitation energy of the intermediate state, and the latter one is an almost monotonically and mildly increasing function. My QRPA calculations independently of the above one do not have a remarkable decrease. This discrepancy is a serious problem affecting the reliability of calculations of the neutrinoless double-$\beta$ decay, and the cause was unknown. I perform several relevant test calculations and make an analytical consideration to find the cause, which is found to be in the strength of the attractive interactions. The possible major local decrease in the running sum is also explained analytically. The interactions of my QRPA calculation are appropriate in terms of the strength, thus the almost monotonic behavior is reasonable.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·2 citations
3. 03*

   $\gamma Z$-Exchange Contributions in Low-Energy Parity-Violating $ep$ Scattering

   Qian-Qian Guo🇨🇳 · Hai-Qing Zhou🇨🇳

   In this work, the $\gamma Z$-exchange contributions in the low-energy elastic parity-violating $ep$ scattering are discussed with the approximation $m_e=0$. By expanding the $\gamma pp$ and $Zpp$ interactions on the momentum of photon and considering both the leading-order and the next-to-leading order interactions, we calculate the amplitudes of the $\gamma Z$-exchange diagrams. After performing the loop integral, we expand the results in the low energy limit, and obtain the analytic expressions for the amplitudes. Numerical comparisons show that the analytic expressions are very close to the full results over a large region. We investigate the power behaviors of these contributions and find that some are enhanced by a kinematic factor in the low energy limit. Additionally, in some cases, the imaginary parts of the contributions from the next-to-leading-order interactions are at the same order as those from the leading-order interactions. Furthermore, the corresponding contributions to the physical observable quantity $A_{\text{PV}}$ are also discussed. Combining all the properties together, we conclude that these analytic expressions describe the leading-order contributions of all $\gamma Z$-exchange helicity amplitudes in the region with ${\alpha }_e\ll Q/M_N\sim \delta /M_N^2\ll 1$, where ${\alpha }_e$ is the fine structure constant, $M_N$ is the mass of proton, $Q$ and $\delta$ are the small quantities related to the momentum transfer and the center-of-mass energy.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2023)·3 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.