Fri·Aug 6, 2021Friday·August 6, 2021

1. 01*

   Prompt and non-prompt J/$\psi$ production cross sections at midrapidity in proton-proton collisions at $\sqrt{s}$ = 5.02 and 13 TeV

   ALICE Collaboration

   The production of J/$\psi$ is measured at midrapidity ($|y|<0.9$) in proton-proton collisions at $\sqrt{s}$ = 5.02 and 13 TeV, through the dielectron decay channel, using the ALICE detector at the Large Hadron Collider. The data sets used for the analyses correspond to integrated luminosities of ${\mathcal{L}}_{\mathrm{int}}$ = 19.4 $\pm$ 0.4 nb${}^{-1}$ and ${\mathcal{L}}_{\mathrm{int}}$ = 32.2 $\pm$ 0.5 nb${}^{-1}$ at $\sqrt{s}$ = 5.02 and 13 TeV, respectively. The fraction of non-prompt J/$\psi$ mesons, i.e. those originating from the decay of beauty hadrons, is measured down to a transverse momentum $p_{\mathrm{T}}$ = 2 GeV/$c$ (1 GeV/$c$) at $\sqrt{s}$ = 5.02 TeV (13 TeV). The $p_{\mathrm{T}}$ and rapidity ($y$) differential cross sections, as well as the corresponding values integrated over $p_{\mathrm{T}}$ and $y$, are carried out separately for prompt and non-prompt J/$\psi$ mesons. The results are compared with measurements from other experiments and theoretical calculations based on quantum chromodynamics (QCD). The shapes of the $p_{\mathrm{T}}$ and $y$ distributions of beauty quarks predicted by state-of-the-art perturbative QCD models are used to extrapolate an estimate of the $\mathrm{b}\overline{\mathrm{b}}$ pair cross section at midrapidity and in the total phase space. The total $\mathrm{b}\overline{\mathrm{b}}$ cross sections are found to be ${\sigma }_{\mathrm{b}\overline{\mathrm{b}}}=541\pm 45(stat.)\pm 69(syst.{)}_{-12}^{+10}(extr.)\mu \mathrm{b}$ and ${\sigma }_{\mathrm{b}\overline{\mathrm{b}}}=218\pm 37(stat.)\pm 31(syst.{)}_{-9.1}^{+8.2}(extr.)\mu \mathrm{b}$ at $\sqrt{s}$ = 13 and 5.02 TeV, respectively. The value obtained from the combination of ALICE and LHCb measurements in pp collisions at $\sqrt{s}$ = 13 TeV is also provided.

   nucl-exhep-exJHEP(2022)·62 citations
2. 02*

   An Investigation of radiative proton-capture reactions in the Cd-In mass region

   P. Vasileiou (1) · T. J. Mertzimekis (1)🇬🇷 · A. Chalil (1)🇫🇷 · C. Fakiola (1) · I. Karakasis (1) · A. Kotsovolou (1) · S. Pelonis (1) · A. Zyriliou (1) · A. Lagoyannis (2) · M. Axiotis (2) ((1) National & Kapodistrian University of Athens, Zografou Campus, Athens, GR-15784, Greece, (2) Institute of Nuclear and Particle Physics, NCSR "Demokritos", Aghia Paraskevi, GR-15310, Greece)

   The reaction network in the neutron-deficient part of the nuclear chart around $A\sim 100$ contains several nuclei of importance to astrophysical processes, such as the p-process. This work reports on the results from recent experimental studies of the radiative proton-capture reactions ${}^{112,114}\mathrm{Cd}(p,\gamma {)}^{113,115}\mathrm{In}$. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched ${}^{112}\mathrm{Cd}$ and ${}^{114}\mathrm{Cd}$ targets. Two different techniques, the in-beam $\gamma$-ray spectroscopy and the activation method have been employed, with the latter considered necessary to account for the presence of low-lying isomers in ${}^{113}\mathrm{In}$ ($E_{\gamma }\approx 392$~keV, $t_{1/2}\approx 100$~min), and ${}^{115}\mathrm{In}$ ($E_{\gamma }\approx 336$~keV, $t_{1/2}\approx 4.5$~h). Following the measurement of the total reaction cross sections, the astrophysical S factors have been additionally deduced. The experimental results are compared with Hauser-Feshbach theoretical calculations carried out with the most recent version of TALYS. The results are discussed in terms of their significance to the various parameters entering the models.

   nucl-exNPA(2021)·5 citations
3. 03*

   Charge radii in covariant density functional theory: a global view

   U. C. Perera🇺🇸 · A.V. Afanasjev🇺🇸 · P. Ring🇩🇪

   A systematic global investigation of differential charge radii has been performed within the CDFT framework for the first time. Theoretical results obtained with conventional covariant energy density functionals and separable pairing interaction are compared with experimental differential charge radii in the regions of the nuclear chart in which available experimental data crosses neutron shell closures at N = 28, 50, 82 and 126. The analysis of absolute differential radii of different isotopic chains and their relative properties indicate clearly that such properties are reasonably well described in model calculations in the cases when the mean-field approximation is justified. However, while the observed clusterization of differential charge radii of different isotopic chains is well described above the N=50 and N=126 shell closures, it is more difficult to reproduce it above the N=28 and N=82 shell closures because of possible deficiencies in underlying single-particle structure. The impact of the latter has been evaluated for spherical shapes and it was shown that the relative energies of the single-particle states and the patterns of their occupation with increasing neutron number have an appreciable impact on the evolution of the differential charge radii. It is shown that the kinks in the charge radii at neutron shell closures are due to the underlying single-particle structure and due to weakening or collapse of pairing at these closures. It is usually assumed that pairing is a dominant contributor to odd-even staggering (OES) in charge radii. Our analysis paints a more complicated picture. It suggests a new mechanism in which the fragmentation of the single-particle content of the ground state in odd-mass nuclei due to particle-vibration coupling provides a significant contribution to OES in charge radii.

   ↳ nucl-thnucl-exPRC(2021)·79 citations
4. 04*

   Dynamical diquarks in the ${\mathbf{\gamma }}^{(\ast )}\mathbf{p}\to \mathbf{N}(1535){\frac{1}{2}}^{-}$ transition

   Khépani Raya🇨🇳 · L. X. Gutiérrez-Guerrero🇲🇽 · Adnan Bashir🇲🇽 · Lei Chang🇨🇳 · Zhu-Fang Cui🇨🇳 · Ya Lu🇨🇳 · Craig D. Roberts🇨🇳 · Jorge Segovia🇪🇸

   The ${\gamma }^{(\ast )}+p\to N(1535){\frac{1}{2}}^{-}$ transition is studied using a symmetry-preserving regularisation of a vector$\otimes$vector contact interaction (SCI). The framework employs a Poincaré-covariant Faddeev equation to describe the initial and final state baryons as quark+di\-quark composites, wherein the diquark correlations are fully dynamical, interacting with the photon as allowed by their quantum numbers and continually engaging in breakup and recombination as required by the Faddeev kernel. The presence of such correlations owes largely to the mechanisms responsible for the emergence of hadron mass; and whereas the nucleon Faddeev amplitude is dominated by scalar and axial-vector diquark correlations, the amplitude of its parity partner, the $N(1535){\frac{1}{2}}^{-}$, also contains sizeable pseudoscalar and vector diquark components. It is found that the ${\gamma }^{(\ast )}+p\to N(1535){\frac{1}{2}}^{-}$ helicity amplitudes and related Dirac and Pauli form factors are keenly sensitive to the relative strengths of these diquark components in the baryon amplitudes, indicating that such resonance electrocouplings possess great sensitivity to baryon structural details. Whilst SCI analyses have their limitations, they also have the virtue of algebraic simplicity and a proven ability to reveal insights that can be used to inform more sophisticated studies in frameworks with closer ties to quantum chromodynamics.

   ↳ hep-phhep-latnucl-exnucl-thEPJA(2021)·43 citations
5. 05*

   Elastic $\alpha$-${}^{12}$C scattering at low energies with the resonant $2_2^{+}$ and $2_3^{+}$ states of ${}^{16}$O

   Shung-Ichi Ando🇰🇷

   The elastic $\alpha$-${}^{12}$C scattering for $l=2$ at low energies is studied in an effective Lagrangian approach. We explicitly include two resonant $2_2^{+}$ and $2_3^{+}$ states of ${}^{16}$O in the scattering amplitudes and construct an $S$ matrix assuming that three amplitudes, the non-resonant part of the amplitude which has the sub-threshold $2_1^{+}$ state of ${}^{16}$O and those of the two resonant states, are represented by the summation of corresponding parts of the phase shift. Then, we fit the parameters in the $S$ matrix to the phase shift data by imposing three conditions at very low energies where the phase shift data are not available. By using the fitted parameters, we calculate the asymptotic normalization coefficients (ANC) of the $2_1^{+}$ state of ${}^{16}$O and find that the previously reported small and large values of the ANC can be reproduced depending on the imposed conditions, but we obtain large error bars for the large ANC values which are reported from the $\alpha$ transfer reactions.

   ↳ nucl-thnucl-exPRC(2022)·7 citations
6. 06*

   $J/\psi$ photo-production in Pb-Pb peripheral collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5 TeV

   LHCb collaboration: R. Aaij · C. Abellán Beteta · T. Ackernley · B. Adeva · M. Adinolfi · H. Afsharnia · C.A. Aidala · S. Aiola · Z. Ajaltouni · S. Akar · J. Albrecht · F. Alessio and 941 other authors

   The photo-production of $J/\psi$ mesons at low transverse momentum is studied in peripheral lead-lead collisions collected by the LHCb experiment at a centre-of-mass energy per nucleon pair of 5 TeV, corresponding to an integrated luminosity of 210 ${\mu \mathrm{b}}^{-1}$. The $J/\psi$ candidates are reconstructed through the prompt decay into two muons of opposite charge in the rapidity region of $2.0<y<4.5$. The results significantly improve previous measurements and are compared to the latest theoretical prediction.

   ↳ hep-exnucl-exPRC(2022)·54 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.