Tue·Mar 12, 2024Tuesday·March 12, 2024

1. 01*

   Search for a new charged particle in the mass range of 2-100 MeV

   M.H. Anikina · V.A. Nikitin · V.C.Rikhvitsky

   In the theory of electroweak interactions, there is no prohibition on the existence of particles with a mass other than that of an electron, muon and tauon. The task is to search for a new particle in the mass range of 2-100 MeV. The search was performed using the photo material of the 2-m propane bubble chamber. The chamber has been exposed in a 10 GeV proton beam at the JINR Synchrophasotron. For its search, ~55 thousand stereo photos have been scanned. The events of the $\gamma$ quantum conversion into a pair of charged particles have been analyzed. 50 anomalous events have been found in which one particle of the pair stops in the volume of the chamber, has an increased track density at the end of the range and, upon identification, detects a mass of ~ 8 MeV. The average value of the mass of the new particle is (8.5 $\pm$ 2.5) MeV

   nucl-exhep-ex0 citations
2. 02*

   Testing effective field theory with the most general neutron decay correlations

   Chien-Yeah Seng🇺🇸

   Built on the seminal works by Jackson-Treiman-Wyld and Ebel-Feldman, we derive the most general free neutron differential decay rate where all massive particles (neutron, proton and electron) are polarized. This introduces 33 new correlations in addition to the 18 existing ones, which over-constrain the coupling constants in the low-energy effective field theory of charged weak interactions, and thus provides stringent tests of the validity of the theory framework itself. We classify the correlation coefficients in terms of their Standard Model limit and discrete symmetries, and study their expansion with respect to the new physics coupling strengths, supplemented by the experiment-independent $\mathcal{O}(\alpha )$ virtual electromagnetic radiative corrections.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2024)·2 citations
3. 03*

   Muon Capture on ${}^6$Li, ${}^{12}$C, and ${}^{16}$O from $AbInitio$ Nuclear Theory

   Lotta Jokiniemi🇨🇦 · Petr Navratil🇨🇦 · Jenni Kotila🇫🇮 · Kostas Kravvaris🇺🇸

   Muon capture on nuclei is one of the most promising probes of the nuclear electroweak current driving the yet-hypothetical neutrinoless double-beta ($0\nu \beta \beta$) decay. Both processes involve vector and axial-vector currents at finite momentum transfer, $q\sim 100$ MeV, as well as the induced pseudoscalar and weak-magnetism currents. Comparing measured muon-capture rates with reliable $abinitio$ nuclear-theory predictions could help us validate these currents. To this end, we compute partial muon-capture rates for ${}^6$Li, ${}^{12}$C and ${}^{16}$O, feeding the ground and excited states in ${}^6$He, ${}^{12}$B and ${}^{16}$N, using $abinitio$ no-core shell model with two- and three-nucleon chiral interactions. We remove the spurious center-of-mass motion by introducing translationally invariant operators and approximate the effect of hadronic two-body currents by Fermi-gas model. We solve the bound-muon wave function from the Dirac wave equations in the Coulomb field created by a finite nucleus. We find that the computed rates to the low-lying states in the final nuclei are in good agreement with the measured counterparts. We highlight sensitivity of some of the transitions to the sub-leading three-nucleon interaction terms. We also compare summed rates to several tens of final states with the measured total capture rates and note that we slightly underestimate the total rate with this simple approach due to limited range of excitation energies.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2024)·17 citations
4. 04*

   Symmetric cumulant $s{c}_{2,4}\left\{4\right\}$ and asymmetric cumulant $a{c}_2\left\{3\right\}$ from transverse momentum conservation and flow

   Jia-Lin Pei🇨🇳 · Guo-Liang Ma🇨🇳 · Adam Bzdak🇵🇱

   Multiparticle cumulants method can be used to reveal long-range collectivity in small and large colliding systems. The four-particle symmetric cumulant $s{c}_{2,4}\left\{4\right\}$, three-particle asymmetric cumulant $a{c}_2\left\{3\right\}$, and the normalized cumulants $ns{c}_{2,4}\left\{4\right\}$ and $na{c}_2\left\{3\right\}$ from the transverse momentum conservation and flow are calculated. The interplay between the two effects is also investigated. Our results are in a good agreement with the recent ATLAS measurements of multiparticle azimuthal correlations with the subevent cumulant method, which provides insight into the origin of collective flow in small systems.

   ↳ hep-phnucl-exnucl-thPRC(2024)·5 citations
5. 05*

   Accessing the speed of sound in relativistic ultracentral nucleus-nucleus collisions using the mean transverse momentum

   Fernando G. Gardim🇧🇷 · Andre V. Giannini🇧🇷 · Jean-Yves Ollitrault🇫🇷

   It has been argued that the speed of sound of the strong interaction at high temperature can be measured using the variation of the mean transverse momentum with the particle multiplicity in ultracentral heavy-ion collisions. We test this correspondence by running hydrodynamic simulations at zero impact parameter with several equations of state, at several colliding energies from 0.2 TeV to 15 TeV per nucleon pair. The correspondence is found to be precise and robust for a smooth, boost-invariant fluid and an ideal detector. We discuss the differences between this ideal setup and an actual experiment. We conclude that the extraction of the speed of sound from data is reliable, and that the main uncertainty comes from our poor knowledge of the distribution of density fluctuations at the early stages of the collision.

   ↳ nucl-thhep-phnucl-exPLB(2024)·21 citations
6. 06*

   Gluon Double-Spin Asymmetry in the Longitudinally Polarized $p+p$ Collisions

   Yuri V. Kovchegov🇺🇸 · Ming Li🇺🇸

   We derive the first-ever small-$x$ expression for the inclusive gluon production cross section in the central rapidity region of the longitudinally polarized proton-proton collisions. The cross section depends on the polarizations of both protons, therefore comprising the numerator of the longitudinal double-spin asymmetry $A_{LL}$ for the produced gluons. The cross section is calculated in the shock wave formalism and is expressed in terms of the polarized dipole scattering amplitudes on the projectile and target protons. We show that the small-$x$ evolution corrections are included into our cross section expression if one evolves these polarized dipole amplitudes using the double-logarithmic helicity evolution derived in \cite{Kovchegov:2015pbl, Kovchegov:2016zex, Kovchegov:2018znm, Cougoulic:2022gbk}. Our calculation is performed for the gluon sector only, with the quark contribution left for future work. When that work is complete, the resulting formula will be applicable to longitudinally polarized proton-proton and proton-nucleus collisions, as well as to polarized semi-inclusive deep inelastic scattering (SIDIS) on a proton or a nucleus. Our results should allow one to extend the small-$x$ helicity phenomenology analysis of \cite{Adamiak:2023yhz} to the jet/hadron production data reported for the longitudinally polarized proton-proton collisions at RHIC and to polarized SIDIS measurements at central rapidities to be performed at the EIC.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2024)·19 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.