Fri·Dec 29, 2023Friday·December 29, 2023

1. 01*

   Anisotropic Flow of Identified Particles in Au + Au Collisions at $\sqrt{s_{NN}}$ = 3-3.9 GeV at RHIC

   Zuowen Liu🇨🇳

   In these proceedings, we present transverse momentum dependence of the mid-rapidity slope of directed flow ($d{v}_1/dy{|}_{y=0}$) for ${\pi }^{+}$ and $K_S^0$ in Au + Au collisions at $\sqrt{s_{NN}}$ = 3.0, 3.2, 3.5, and 3.9 GeV. Both ${\pi }^{+}$ and $K_S^0$ show negative $v_1$ slope at low $p_T$ ($p_T<0.6$ GeV/$c$). Collision energy dependence of $v_1$ slope and $p_T$-integrated $v_2$ for ${\pi }^{\pm }$, $K_S^0$, and $\Lambda$ are also presented. A comparison to JAM model calculations indicates that spectator shadowing can lead to anti-flow at low $p_T$. In addition, a breaking of the Number of Constitute Quark (NCQ) scaling of elliptic flow ($v_2$) is observed at $\sqrt{s_{NN}}$ = 3.2 GeV, which implies the dominance of hadronic degrees of freedom occurs in collisions at $\sqrt{s_{NN}}$ = 3.2 GeV and below.

   nucl-exhep-exEPJ Web Conf.(2024)·3 citations
2. 02*

   Search for the 6$\alpha$ condensed state in ${}^{24}$Mg using the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ scattering

   Y. Fujikawa · T. Kawabata🇯🇵 · S. Adachi · S. Enyo · T. Furuno🇯🇵 · Y. Hijikata🇯🇵 · K. Himi · K. Hirose🇯🇵 · Y. Honda🇯🇵 · K. Inaba🇯🇵 · H. Makii · K. Miyamoto🇯🇵 and 9 other authors

   We searched for the 6$\alpha$-condensed state in ${}^{24}$Mg by measuring the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ scattering with the SAKRA Si detector array at E_\rm{cm} = 17.5-25.0 MeV. By using the invariant-mass method for the detected 3$\alpha$ particles, the inclusive cross sections for the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}\to {}^{12}\mathrm{C}(0_2^{+})+\mathrm{X}$ and ${}^{12}\mathrm{C}(3_1^{-})+\mathrm{X}$ reactions were determined. In addition, the missing-mass spectroscopy was successfully utilized to determine the excitation energy of the residual ${}^{12}\mathrm{C}$ nucleus and the exclusive cross sections for the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}\to {}^{12}\mathrm{C}(0_2^{+})+{}^{12}\mathrm{C}(0_1^{+})$, ${}^{12}\mathrm{C}(0_2^{+})+{}^{12}\mathrm{C}(2_1^{+})$, and ${}^{12}\mathrm{C}(0_2^{+})+{}^{12}\mathrm{C}(0_2^{+})$ reactions. In both the inclusive ${}^{12}\mathrm{C}(0_2^{+})+\mathrm{X}$ channel and the exclusive ${}^{12}\mathrm{C}(0_2^{+})+{}^{12}\mathrm{C}(0_1^{+})$ channel, the cross section peaked at $E_{r}mcm$ = 19.4 MeV, which correspond to the excitation energy of $E_x$ = 33.3 MeV in ${}^{24}\mathrm{Mg}$. This 19.4-MeV state is a candidate for the 6$\alpha$-condensed state because of the agreement of the excitation energy with the theoretical value and its decay property. In the exclusive ${}^{12}\mathrm{C}(0_2^{+})+{}^{12}\mathrm{C}(0_2^{+})$ channel, a broad state was observed at E_\rm{cm} = 22.5 MeV, which correspond to the excitation energy of $E_x$ = 36.4 MeV in ${}^{24}\mathrm{Mg}$. From the angular distribution of the differential cross section, the spin and parity of this 22.5-MeV state was assigned to be $4^{+}$. In addition, a $2^{+}$ state was suggested at the low-energy side of the 22.5-MeV state. Because their excitation energies are higher than the theoretical value of the 6$\alpha$-condensed state, these states might be excited states of the 6$\alpha$-condensed state such as the $2_2^{+}$ and $4_1^{+}$ states in ${}^{12}\mathrm{C}$.

   nucl-exnucl-thPLB(2024)·12 citations
3. 03*

   Elliptic anisotropy measurement of the f${}_0$(980) hadron in proton-lead collisions and evidence for its quark-antiquark composition

   CMS Collaboration

   Despite the f${}_0$(980) hadron having been discovered half a century ago, the question about its quark content has not been settled: it might be an ordinary quark-antiquark ($\mathrm{q}\bar{\mathrm{q}}$) meson, a tetraquark ($\mathrm{q}\bar{\mathrm{q}}\mathrm{q}\bar{\mathrm{q}}$) exotic state, a kaon-antikaon ($\mathrm{K}\bar{\mathrm{K}}$) molecule, or a quark-antiquark-gluon ($\mathrm{q}\bar{\mathrm{q}}\mathrm{g}$) hybrid. This paper reports strong evidence that the f${}_0$(980) state is an ordinary $\mathrm{q}\bar{\mathrm{q}}$ meson, inferred from the scaling of elliptic anisotropies ($v_2$) with the number of constituent quarks ($n_{\mathrm{q}}$), as empirically established using conventional hadrons in relativistic heavy ion collisions. The f${}_0$(980) state is reconstructed via its dominant decay channel f${}_0$(980) $\to$ ${\pi }^{+}{\pi }^{-}$, in proton-lead collisions recorded by the CMS experiment at the LHC, and its $v_2$ is measured as a function of transverse momentum ($p_{\mathrm{T}}$). It is found that the $n_q$ = 2 ($\mathrm{q}\bar{\mathrm{q}}$ state) hypothesis is favored over $n_q$ = 4 ($\mathrm{q}\bar{\mathrm{q}}\mathrm{q}\bar{\mathrm{q}}$ or $\mathrm{K}\bar{\mathrm{K}}$ states) by 7.7, 6.3, or 3.1 standard deviations in the $p_{\mathrm{T}}$ $<$ 10, 8, or 6 GeV/$c$ ranges, respectively, and over $n_{\mathrm{q}}$ = 3 ($\mathrm{q}\bar{\mathrm{q}}\mathrm{g}$ hybrid state) by 3.5 standard deviations in the $p_{\mathrm{T}}$ $<$ 8 GeV/$c$ range. This result represents the first determination of the quark content of the f${}_0$(980) state, made possible by using a novel approach, and paves the way for similar studies of other exotic hadron candidates.

   nucl-exhep-exNature Commun.(2025)·17 citations
4. 04*

   $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ cross sections and the ${\Lambda }_c^{+}$ electromagnetic form factors within the extended vector meson dominance model

   Cheng Chen🇨🇳 · Bing Yan🇨🇳 · Ju-Jun Xie🇨🇳

   Within the extended vector meson dominance model, we investigate the $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ reaction and the electromagnetic form factors of the charmed baryon ${\Lambda }_c^{+}$. The model parameters are determined by fitting them to the cross sections of the process $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ and the magnetic form factor $|G_M|$ of ${\Lambda }_c^{+}$. By considering four charmoniumlike states, called $\psi (4500)$, $\psi (4660)$, $\psi (4790)$, and $\psi (4900)$, we can well describe the current data on the $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ reaction from the reaction threshold up to $4.96\mathrm{GeV}$. In addition to the total cross sections and $|G_M|$, the ratio $|G_E/G_M|$ and effective form factor $|G_{\mathrm{eff}}|$ for ${\Lambda }_c^{+}$ are also calculated, and found that these calculations are consistent with the experimental data. Within the fitted model parameters, we have also estimated the charge radius of the charmed ${\Lambda }_c^{+}$ baryon.

   ↳ hep-phhep-exnucl-exnucl-thChin.Phys.Lett.(2024)·15 citations
5. 05*

   Light-by-Light Scattering at Next-to-Leading Order in QCD and QED

   Ajjath A H🇫🇷 · Ekta Chaubey🇩🇪 · Mathijs Fraaije🇨🇭 · Valentin Hirschi🇨🇭 · Hua-Sheng Shao🇫🇷

   The recent experimental observation of Light-by-Light (LbL) scattering at the Large Hadron Collider has revived interest in this fundamental process, and especially of the accurate prediction of its cross-section, which we present here for the first time at Next-to-Leading Order (NLO) in both QCD and QED. We compare two radically different computational approaches, both exact in the fermion mass dependence, thus offering a strong cross-check of our results. The first approach is a fully analytic method to calculate compact and well-organized two-loop helicity amplitudes. The second one is entirely numerical and leverages the Local Unitarity construction. Our two calculations agree with each other and conclude that including the exact fermion mass contribution typically increases the size of the NLO corrections. Moreover, we find that the exact result converges slowly to the massless limit of the high-energy regime, thus emphasizing the importance of including the full mass dependence at NLO. We also compare our results with the ATLAS measurement of LbL in ultra-peripheral lead-lead collisions, and find that the inclusion of exact NLO corrections reduces, but does not eliminate, the existing tension with theoretical predictions.

   ↳ hep-phhep-exhep-thnucl-ex+1PLB(2024)·33 citations
6. 06*

   Constraining the p{\Lambda} interaction from a combined analysis of scattering data and correlation functions

   D. L. Mihaylov🇩🇪 · J. Haidenbauer🇩🇪 · V. Mantovani Sarti🇩🇪

   This work provides the first combined analysis of low-energy p$\Lambda$ scattering, considering both cross section and correlation data. The obtained results establish the most stringent constraints to date on the two-body p$\Lambda$ interaction, pointing to a weaker attraction than so far accepted. The best set of scattering lengths for the spin singlet and triplet are found to range from $f_0,f_1=(2.1,1.56)$ to $(3.34,1.18)$fm. With a chiral NY potential fine-tuned to those scattering parameters, the in-medium properties of the $\Lambda$ are explored and a potential depth of $U_{\Lambda }=-36.3\pm 1.3{(\mathrm{stat})}_{-6.2}^{+2.5}(\mathrm{syst})$ MeV is found at nuclear matter saturation density.

   ↳ nucl-thnucl-exPLB(2024)·25 citations
7. 07*

   Atomic mass determination of uranium-238

   Kathrin Kromer🇩🇪 · Chunhai Lyu🇩🇪 · Jacek Bieroń🇵🇱 · Menno Door🇩🇪 · Lucia Enzmann · Pavel Filianin🇩🇪 · Gediminas Gaigalas🇱🇹 · Zoltán Harman🇩🇪 · Jost Herkenhoff🇩🇪 · Wenjia Huang🇫🇷 · Christoph H. Keitel🇩🇪 · Sergey Eliseev🇩🇪 · Klaus Blaum🇩🇪

   The atomic mass of uranium-238 has been determined to be $238.050787618(15)\text{u}$, improving the literature uncertainty by two orders of magnitude. It is obtained from a measurement of the mass ratio of ${}^{238}$U${}^{47+}$ and ${}^{132}$Xe${}^{26+}$ ions with an uncertainty of $3.5\times 10^{-12}$. The measurement was carried out with the Penning-trap mass spectrometer \textsc{Pentatrap} and was accompanied by a calculation of the binding energies $E_{\text{U}}$ and $E_{\text{Xe}}$ of the 47 and 26 missing electrons of the two highly charged ions, respectively. These binding energies were determined using an \textit{ab initio} multiconfiguration Dirac-Hartree-Fock (MCDHF) method to be $E_{\text{U}}=39927(10)\text{eV}$ and $E_{\text{Xe}}=8971.2(21)\text{eV}$. The new mass value will serve as a reference for high-precision mass measurements in the heavy mass region of the nuclear chart up to transuranium nuclides.

   ↳ physics.atom-phnucl-exPRC(2024)·4 citations
8. 08*

   Production of super-heavy nuclei in hot-fusion reactions

   V. Yu. Denisov🇺🇦

   A model for hot-fusion reactions leading to the synthesis of super-heavy nuclei is discussed. The values of the hot-fusion cross-sections obtained in the model agree with the available experimental data. The hot-fusion cross-sections are found for two different models of the fission barrier heights of super-heavy nuclei. The calculations of the cross-sections for the various hot-fusion reactions leading to the 119 and 120 elements are presented. Simple expressions useful for qualitative analysis of the cross-section for forming super-heavy nuclei are obtained. It is shown that the super-heavy nuclei production cross section is proportional to the transmission coefficient of the capture barrier, realization probability of the $xn$-evaporation channel, and exponentially depends on the quasi-elastic barrier, fusion reaction Q-value, compound nucleus formation barrier, neutron separation energies, and fission barrier heights.

   ↳ nucl-thnucl-exPRC(2024)·9 citations
9. 09*

   Observation of enhanced long-range elliptic anisotropies inside high-multiplicity jets in pp collisions at $\sqrt{s}$ = 13 TeV

   CMS Collaboration

   A search for partonic collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged constituents using the CMS detector at the CERN LHC. The analysis uses data collected at a center-of-mass energy of $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb${}^{-1}$. Jets are reconstructed with the anti-$k_{\mathrm{T}}$ algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity $|\eta |$ $<$ 1.6. Two-particle correlations among the charged constituents within the jets are studied as functions of the particles' azimuthal angle and pseudorapidity separations ($\Delta {\varphi }^{\ast }$ and $\Delta {\eta }^{\ast }$) in a jet coordinate basis, where constituents' ${\eta }^{\ast }$, ${\varphi }^{\ast }$ are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to $N_{\text{ch}}^{\mathrm{j}}$ $\approx$ 100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for $|\Delta {\eta }^{\ast }|$ $>$ 2. For low-$N_{\text{ch}}^{\mathrm{j}}$, the long-range elliptic anisotropic harmonic, $v_2^{\ast }$, is observed to decrease with $N_{\text{ch}}^{\mathrm{j}}$. This trend is well described by Monte Carlo event generators. However, a rising trend for $v_2^{\ast }$ emerges at $N_{\text{ch}}^{\mathrm{j}}$ $\gtrsim$ 80, hinting at a possible onset of collective behavior, which is not reproduced by the models tested. This observation yields new insights into the dynamics of parton fragmentation processes in the vacuum.

   ↳ hep-exnucl-exPRL(2024)·39 citations
10. 10*

    Extended Skyrme effective interactions for transport model and neutron stars

    Si-Pei Wang🇨🇳 · Rui Wang🇮🇹 · Jun-Ting Ye🇨🇳 · Lie-Wen Chen🇨🇳

    It is important to develop a unified theoretical framework to describe the nuclear experiments and astrophysical observations based on the same effective nuclear interactions. Based on the so-called Skyrme pseudopotential up to next-to-next-to-next-to-leading order, we construct a series of extended Skyrme interactions by modifying the density-dependent term and fitting the empirical nucleon optical potential up to above $1$ GeV, the empirical properties of isospin symmetric nuclear matter, the microscopic calculations of pure neutron matter and the properties of neutron stars from astrophysical observations. The modification of the density-dependent term in the extended Skyrme interactions follows the idea of Fermi momentum expansion and this leads to a highly flexible density behavior of the symmetry energy. In particular, the values of the density slope parameter $L$ of the symmetry energy for the new extended Skyrme interactions range from $L=-5$ MeV to $L=125$ MeV by construction, to cover the large uncertainty of the density dependence of the symmetry energy. Furthermore, in order to consider the effects of isoscalar and isovector nucleon effective masses, we adjust the momentum dependency of the single-nucleon optical potential and the symmetry potential of these new extended Skyrme interactions and construct a parameter set family, by which we systematically study the impacts of the symmetry energy and the nucleon effective masses on the properties of nuclear matter and neutron stars. The new extended Skyrme interactions constructed in the present work will be useful to determine the equation of state of isospin asymmetric nuclear matter, especially the symmetry energy, as well as the nucleon effective masses and their isospin splitting, in transport model simulations for heavy-ion collisions, nuclear structure calculations and neutron star studies.

    ↳ nucl-thastro-ph.HEhep-phnucl-exPRC(2024)·19 citations
11. 11*

    Empirical fits to inclusive electron-carbon scattering data obtained by deep-learning methods

    Beata E. Kowal🇵🇱 · Krzysztof M. Graczyk🇵🇱 · Artur M. Ankowski🇵🇱 · Rwik Dharmapal Banerjee🇵🇱 · Hemant Prasad🇵🇱 · Jan T. Sobczyk🇵🇱

    Employing the neural network framework, we obtain empirical fits to the electron-scattering cross sections for carbon over a broad kinematic region, extending from the quasielastic peak through resonance excitation to the onset of deep-inelastic scattering. We consider two different methods of obtaining such model-independent parametrizations and the corresponding uncertainties: based on the bootstrap approach and the Monte Carlo dropout approach. In our analysis, the ${\chi }^2$ defines the loss function, including point-to-point and normalization uncertainties for each independent set of measurements. Our statistical approaches lead to fits of comparable quality and similar uncertainties of the order of $7$%. To test these models, we compare their predictions to test datasets excluded from the training process and theoretical predictions obtained within the spectral function approach. The predictions of both models agree with experimental measurements and theoretical calculations. We also perform a comparison to a dataset lying beyond the covered kinematic region, and find that the bootstrap approach shows better interpolation and extrapolation abilities than the one based on the dropout algorithm.

    ↳ hep-phcs.LGhep-exnucl-ex+1PRC(2024)·9 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.