Wed·May 12, 2021Wednesday·May 12, 2021

1. 01*

   Production of $\Lambda$ and ${\mathrm{K}}_{\mathrm{S}}^0$ in jets in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV and pp collisions at $\sqrt{s}=7$ TeV

   ALICE Collaboration

   The production of $\Lambda$ baryons and ${\mathrm{K}}_{\mathrm{S}}^0$ mesons (${\mathrm{V}}^0$ particles) was measured in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV and pp collisions at $\sqrt{s}=7$ TeV with ALICE at the LHC. The production of these strange particles is studied separately for particles associated with hard scatterings and the underlying event to shed light on the baryon-to-meson ratio enhancement observed at intermediate transverse momentum ($p_{\mathrm{T}}$) in high multiplicity pp and p-Pb collisions. Hard scatterings are selected on an event-by-event basis with jets reconstructed with the anti-$k_{\mathrm{T}}$ algorithm using charged particles. The production of strange particles associated with jets $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}>10$ and $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}>20$ GeV/$c$ in p-Pb collisions, and with jet $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}>10$ GeV/$c$ in pp collisions is reported as a function of $p_{\mathrm{T}}$. Its dependence on angular distance from the jet axis, $R({\mathrm{V}}^0,\mathrm{jet})$, for jets with $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}>10$ GeV/$c$ in p-Pb collisions is reported as well. The $p_{\mathrm{T}}$-differential production spectra of strange particles associated with jets are found to be harder compared to that in the underlying event and both differ from the inclusive measurements. In events containing a jet, the density of the ${\mathrm{V}}^0$ particles in the underlying event is found to be larger than the density in the minimum bias events. The $\Lambda /{\mathrm{K}}_{\mathrm{S}}^0$ ratio associated with jets in p-Pb collisions is consistent with the ratio in pp collisions and follows the expectation of jets fragmenting in vacuum. On the other hand, this ratio within jets is consistently lower than the one obtained in the underlying event and it does not show the characteristic enhancement of baryons at intermediate $p_{\mathrm{T}}$ often referred to as "baryon anomaly" in the inclusive measurements.

   nucl-exhep-exPLB(2022)·33 citations
2. 02*

   Fusion of 16O+165Ho at deep sub-barrier energies

   Saikat Bhattacharjee🇮🇳 · A. Mukherjee🇮🇳 · Ashish Gupta🇮🇳 · Rajkumar Santra🇮🇳 · D. Chattopadhyay🇮🇳 · N. Deshmukh🇮🇹 · Sangeeta Dhuri🇮🇳 · Shilpi Gupta🇮🇳 · V.V. Parkar🇮🇳 · S.K. Pandit🇮🇳 · K. Ramachandran🇮🇳 · K. Mahata🇮🇳 and 3 other authors

   Fusion cross-sections have been measured for the asymmetric system 16O+165Ho at energies near and deep below the Coulomb barrier with an aim to investigate the occurrence of fusion hindrance for the system. Fusion cross sections down to ~ 700 nb have been measured using the off-beam gamma-ray technique. The fusion cross sections have been compared with the coupled channel calculations. Although the onset of fusion hindrance could not be observed experimentally, an indication of a small deviation of the experimental fusion cross-sections with respect to the calculated cross-sections could be observed at the lowest energy measured. However, the energy onset of fusion hindrance has been obtained from the extrapolation technique and is found to be about 2 MeV below the lowest energy of the present measurement.

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

   First measurements of $N$-subjettiness in central Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   The ALICE Collaboration reports the first fully-corrected measurements of the $N$-subjettiness observable for track-based jets in heavy-ion collisions. This study is performed using data recorded in pp and Pb$-$Pb collisions at centre-of-mass energies of $\sqrt{s}=7$ TeV and $\sqrt{s_{\mathrm{NN}}}=2.76$\,TeV, respectively. In particular the ratio of 2-subjettiness to 1-subjettiness, ${\tau }_2/{\tau }_1$, which is sensitive to the rate of two-pronged jet substructure, is presented. Energy loss of jets traversing the strongly interacting medium in heavy-ion collisions is expected to change the rate of two-pronged substructure relative to vacuum. The results are presented for jets with a resolution parameter of $R=0.4$ and charged jet transverse momentum of $40\le p_{\mathrm{T},\mathrm{jet}}\le 60$ GeV/$c$, which constitute a larger jet resolution and lower jet transverse momentum interval than previous measurements in heavy-ion collisions. This has been achieved by utilising a semi-inclusive hadron-jet coincidence technique to suppress the larger jet combinatorial background in this kinematic region. No significant modification of the ${\tau }_2/{\tau }_1$ observable for track-based jets in Pb--Pb collisions is observed relative to vacuum PYTHIA6 and PYTHIA8 references at the same collision energy. The measurements of ${\tau }_2/{\tau }_1$, together with the splitting aperture angle $\Delta R$, are also performed in pp collisions at $\sqrt{s}=7$ TeV for inclusive jets. These results are compared with PYTHIA calculations at $\sqrt{s}=7$ TeV, in order to validate the model as a vacuum reference for the Pb$-$Pb centre-of-mass energy. The PYTHIA references for ${\tau }_2/{\tau }_1$ are shifted to larger values compared to the measurement in pp collisions. This hints at a reduction in the rate of two-pronged jets in Pb--Pb collisions compared to pp collisions.

   nucl-exhep-exJHEP(2021)·20 citations
4. 04*

   Inclusive, prompt and non-prompt $\mathrm{J}/\psi$ production at midrapidity in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   A measurement of inclusive, prompt, and non-prompt $\mathrm{J}/\psi$ production in p$-$Pb collisions at a nucleon$-$nucleon centre-of-mass energy $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is presented. The inclusive $\mathrm{J}/\psi$ mesons are reconstructed in the dielectron decay channel at midrapidity down to a transverse momentum $p_{\mathrm{T}}=0$. The inclusive $\mathrm{J}/\psi$ nuclear modification factor $R_{\mathrm{pPb}}$ is calculated by comparing the new results in p$-$Pb collisions to a recently measured proton$-$proton reference at the same centre-of-mass energy. Non-prompt $\mathrm{J}/\psi$ mesons, which originate from the decay of beauty hadrons, are separated from promptly produced $\mathrm{J}/\psi$ on a statistical basis for $p_{\mathrm{T}}$ larger than 1.0 GeV/$c$. These results are based on the data sample collected by the ALICE detector during the 2016 LHC p$-$Pb run, corresponding to an integrated luminosity ${\mathcal{L}}_{\mathrm{int}}=292\pm 11{\mu \mathrm{b}}^{-1}$, which is six times larger than the previous publications. The total uncertainty on the $p_{\mathrm{T}}$-integrated inclusive $\mathrm{J}/\psi$ and non-prompt $\mathrm{J}/\psi$ cross section are reduced by a factor 1.7 and 2.2, respectively. The measured cross sections and $R_{\mathrm{pPb}}$ are compared with theoretical models that include various combinations of cold nuclear matter effects. From the non-prompt $\mathrm{J}/\psi$ production cross section, the $\mathrm{b}\overline{\mathrm{b}}$ production cross section at midrapidity, $\mathrm{d}{\sigma }_{\mathrm{b}\overline{\mathrm{b}}}/\mathrm{d}y$, and the total cross section extrapolated over full phase space, ${\sigma }_{\mathrm{b}\overline{\mathrm{b}}}$, are derived.

   nucl-exhep-exJHEP(2022)·28 citations
5. 05*

   Measurement of the cross sections of ${\Xi }_{\mathrm{c}}^0$ and ${\Xi }_{\mathrm{c}}^{+}$ baryons and branching-fraction ratio BR(${\Xi }_{\mathrm{c}}^0\to {\Xi }^{-}{\mathrm{e}}^{+}{\nu }_{\mathrm{e}}$)/BR(${\Xi }_{\mathrm{c}}^0\to {\Xi }^{-}{\pi }^{+}$) in pp collisions at 13 TeV

   ALICE Collaboration

   The $p_{\mathrm{T}}$-differential cross sections of prompt charm-strange baryons ${\Xi }_{\mathrm{c}}^0$ and ${\Xi }_{\mathrm{c}}^{+}$ were measured at midrapidity ($|y|<0.5$) in proton-proton (pp) collisions at a centre-of-mass energy $\sqrt{s}=$~13~TeV with the ALICE detector at the LHC. The ${\Xi }_{\mathrm{c}}^0$ baryon was reconstructed via both the semileptonic decay (${\Xi }^{-}{\mathrm{e}}^{+}{\nu }_{\mathrm{e}}$) and the hadronic decay (${\Xi }^{-}{\pi }^{+}$) channels. The ${\Xi }_{\mathrm{c}}^{+}$ baryon was reconstructed via the hadronic decay (${\Xi }^{-}{\pi }^{+}{\pi }^{+}$) channel. The branching-fraction ratio $\mathrm{BR}({\mathrm{\Xi }}_{\mathrm{c}}^0\to {\mathrm{\Xi }}^{-}{\mathrm{e}}^{+}{\nu }_{\mathrm{e}})/\mathrm{BR}({\mathrm{\Xi }}_{\mathrm{c}}^0\to {\mathrm{\Xi }}^{-}{\pi }^{+})=$ 0.95 $\pm$ 0.15 (stat) $\pm$ 0.16 (syst) was consistent with the Belle's result within 1$\sigma$. The transverse momentum ($p_{\mathrm{T}}$) dependence of the ${\Xi }_{\mathrm{c}}^0$- and ${\Xi }_{\mathrm{c}}^{+}$-baryon production relative to the ${\mathrm{D}}^0$-meson and to the ${\Sigma }_{\mathrm{c}}^{0,+,++}$- and ${\Lambda }_{\mathrm{c}}^{+}$-baryon production are reported. The baryon-to-meson ratio increases towards low $p_{\mathrm{T}}$ up to a value of approximately 0.3. The measurements are compared with various models that take different hadronisation mechanisms into consideration. The results provide stringent constraints to these theoretical calculations and additional evidence that different processes are involved in charm hadronisation in electron-positron (${\mathrm{e}}^{+}{\mathrm{e}}^{-}$) and hadronic collisions.

   nucl-exhep-exPRL(2021)·101 citations
6. 06*

   Investigating the role of strangeness in baryon$-$antibaryon annihilation at the LHC

   ALICE Collaboration

   Annihilation dynamics plays a fundamental role in the baryon$-$antibaryon interaction (B$-\overline{\mathrm{B}}$) at low-energy and its strength and range are crucial in the assessment of possible baryonic bound states. Experimental data on annihilation cross sections are available for the p$-\overline{\mathrm{p}}$ system but not in the low relative momentum region. Data regarding the B$-\overline{\mathrm{B}}$ interaction with strange degrees of freedom are extremely scarce, hence the modeling of the annihilation contributions is mainly based on nucleon$-$antinucleon (N$-\overline{\mathrm{N}}$) results, when available. In this letter we present a measurement of the p$-\overline{\mathrm{p}}$, p$-\overline{\Lambda }\oplus \overline{\mathrm{p}}-\mathrm{\Lambda }$ and $\Lambda -\overline{\Lambda }$ interaction using correlation functions in the relative momentum space in high-multiplicity triggered pp collisions at $\sqrt{s}=13$ TeV recorded by ALICE at the LHC. In the p$-\overline{\mathrm{p}}$ system the couplings to the mesonic channels in different partial waves are extracted by adopting a coupled-channel approach with recent $\chi \mathrm{EFT}$ potentials. The inclusion of these inelastic channels provides good agreement with the data, showing a significant presence of the annihilation term down to zero momentum. Predictions obtained using the Lednický$-$Lyuboshits formula and scattering parameters obtained from heavy-ion collisions, hence mainly sensitive to elastic processes, are compared with the experimental p$-\overline{\Lambda }\oplus \overline{\mathrm{p}}-\mathrm{\Lambda }$ and $\Lambda -\overline{\Lambda }$ correlations. The model describes the $\Lambda -\overline{\Lambda }$ data and underestimates the p$-\overline{\Lambda }\oplus \overline{\mathrm{p}}-\mathrm{\Lambda }$ data in the region of momenta below 200 MeV/$c$. The observed deviation indicates a different contribution of annihilation channels to the two systems containing strange hadrons.

   nucl-exhep-exPLB(2022)·38 citations
7. 07*

   Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

   Bao-An Li🇺🇸 · Bao-Jun Cai🇨🇳 · Wen-Jie Xie🇨🇳 · Nai-Bo Zhang🇨🇳

   New observational data of neutron stars since GW170817 have helped improve our knowledge about nuclear symmetry energy especially at high densities. We have learned particularly: (1) The slope parameter $L$ of nuclear symmetry energy at saturation density ${\rho }_0$ of nuclear matter from 24 new analyses is about $L\approx 57.7\pm 19$ MeV at 68\% confidence level consistent with its fiducial value, (2) The curvature $K_{\mathrm{sym}}$ from 16 new analyses is about $K_{\mathrm{sym}}\approx -107\pm 88$ MeV, (3) The magnitude of nuclear symmetry energy at $2{\rho }_0$, i.e. $E_{\mathrm{sym}}(2{\rho }_0)\approx 51\pm 13$ MeV at 68\% confidence level, has been extracted from 9 new analyses of neutron star observables consistent with results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories, (4) while the available data from canonical neutron stars do not provide tight constraints on nuclear symmetry energy at densities above about $2{\rho }_0$, the lower radius boundary $R_{2.01}=12.2$ km from NICER's very recent observation of PSR J0740+6620 of mass $2.08\pm 0.07$ $M_{\odot }$ and radius $R=12.2-16.3$ km at 68\% confidence level sets a tight lower limit for nuclear symmetry energy at densities above $2{\rho }_0$, (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars indicate that the phase transition shift appreciably both the $L$ and $K_{\mathrm{sym}}$ to higher values but with larger uncertaintie , (6) The high-density behavior of nuclear symmetry energy affects significantly the minimum frequency necessary to rotationally support GW190814's secondary component of mass (2.50-2.67) $M_{\odot }$ as the fastest and most massive pulsar discovered so far.

   ↳ nucl-thastro-ph.HEnucl-exUniverse(2021)·229 citations
8. 08*

   European Spallation Source: a future for Coherent Neutrino Nucleus Scattering

   Ivan Esteban🇺🇸

   The European Spallation Source (ESS), currently finishing its construction, will soon provide the most intense neutron beams for multi-disciplinary science. At the same time, it will also produce a high-intensity neutrino flux with an energy suitable for precision measurements of Coherent Elastic Neutrino-Nucleus Scattering. We describe some physics prospects, within and beyond the Standard Model, of employing innovative detector technologies to take the most out of this large flux. We show that, compared to current measurements, the ESS will provide a much more precise understanding of neutrino and nuclear properties.

   ↳ hep-phhep-exnucl-exnucl-th3 citations
9. 09*

   Model investigations of the correlation between the mean transverse momentum and anisotropic flow in shape-engineered events

   Niseem Magdy🇺🇸 · Roy A. Lacey🇺🇸

   The correlation between the event mean-transverse momentum $[p_{\mathrm{T}}]$, and the anisotropic flow magnitude $v_n$, $\rho (v_n^2,[p_T])$, has been argued to be sensitive to the initial conditions in heavy-ion collisions. We use simulated events generated with the AMPT and EPOS models for Au+Au at $\sqrt{{\text{s}}_{NN}}$ = 200 GeV, to investigate the model dependence and the response and sensitivity of the $\rho (v_2^2,[p_T])$ correlator to collision-system size and shape, and the viscosity of the matter produced in the collisions. We find good qualitative agreement between the correlators for the string melting version of the AMPT model and the EPOS model. The model investigations for shape-engineered events as well as events with different viscosity ($\eta /s$), indicate that $\rho (v_2^2,[p_T])$ is sensitive to the initial-state geometry of the collision system but is insensitive to sizable changes in $\eta /s$ for the medium produced in the collisions. These findings suggest that precise differential measurements of $\rho (v_2^2,[p_T])$ as a function of system size, shape, and beam-energy could provide more stringent constraints to discern between initial-state models and hence, more reliable extractions of $\eta /s$.

   ↳ nucl-thhep-phnucl-exPLB(2021)·12 citations
10. 10*

    Model independent analysis of coupled-channel scattering: a deep learning approach

    Denny Lane B. Sombillo🇵🇭 · Yoichi Ikeda🇯🇵 · Toru Sato🇯🇵 · Atsushi Hosaka🇯🇵

    We develop a robust method to extract the pole configuration of a given partial-wave amplitude. In our approach, a deep neural network is constructed where the statistical errors of the experimental data are taken into account. The teaching dataset is constructed using a generic S-matrix parametrization, ensuring that all the poles produced are independent of each other. The inclusion of statistical error results into a noisy classification dataset which we should solve using the curriculum method. As an application, we use the elastic $\pi N$ amplitude in the $I(J^P)=1/2(1/2^{-})$ sector where $10^6$ amplitudes are produced by combining points in each error bar of the experimental data. We fed the amplitudes to the trained deep neural network and find that the enhancements in the $\pi N$ amplitude are caused by one pole in each nearby unphysical sheet and at most two poles in the distant sheet. Finally, we show that the extracted pole configurations are independent of the way points in each error bar are drawn and combined, demonstrating the statistical robustness of our method.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2021)·28 citations
11. 11*

    r-Process Radioisotopes from Near-Earth Supernovae and Kilonovae

    Xilu Wang · Adam M. Clark · John Ellis · Adrienne F. Ertel · Brian D. Fields · Zhenghai Liu · Jesse A. Miller · Rebecca Surman

    The astrophysical sites where r-process elements are synthesized remain mysterious: it is clear that neutron star mergers (kilonovae (KNe)) contribute, and some classes of core-collapse supernovae (SNe) are also likely sources of at least the lighter r-process species. The discovery of 60Fe on the Earth and Moon implies that one or more astrophysical explosions have occurred near the Earth within the last few million years, probably SNe. Intriguingly, 244Pu has now been detected, mostly overlapping with 60Fe pulse. However, the 244Pu flux may extend to before 12 Myr ago, pointing to a different origin. Motivated by these observations and difficulties for r-process nucleosynthesis in SN models, we propose that ejecta from a KN enriched the giant molecular cloud that gave rise to the Local Bubble, where the Sun resides. Accelerator mass spectrometry (AMS) measurements of 244Pu and searches for other live isotopes could probe the origins of the r-process and the history of the solar neighborhood, including triggers for mass extinctions, e.g., that at the end of the Devonian epoch, motivating the calculations of the abundances of live r-process radioisotopes produced in SNe and KNe that we present here. Given the presence of 244Pu, other r-process species such as 93Zr, 107Pd, 129I, 135Cs, 182Hf, 236U, 237Np and 247Cm should be present. Their abundances and well-resolved time histories could distinguish between the SN and KN scenarios, and we discuss prospects for their detection in deep-ocean deposits and the lunar regolith. We show that AMS 129I measurements in Fe-Mn crusts already constrain a possible nearby KN scenario.

    ↳ astro-ph.HEhep-phnucl-exnucl-th+1ApJ(2021)·24 citations
12. 12*

    Measurement of nuclear spin relaxation time in lanthanum aluminate for development of polarized lanthanum target

    K. Ishizaki🇯🇵 · H. Hotta🇯🇵 · I. Ide🇯🇵 · M. Iinuma🇯🇵 · T. Iwata🇯🇵 · M. Kitaguchi🇯🇵 · H. Kohri🇯🇵 · D. Miura🇯🇵 · Y. Miyachi🇯🇵 · T. Ohta🇯🇵 · H. M. Shimizu🇯🇵 · H. Yoshikawa🇯🇵 · M. Yosoi🇯🇵

    The nuclear spin-lattice relaxation time ($T_1$) of lanthanum and aluminum nuclei in a single crystal of lanthanum aluminate doped with neodymium ions is studied to estimate the feasibility of the dynamically polarized lanthanum target applicable to beam experiments. The application of our interest is the study of fundamental discrete symmetries in the spin optics of epithermal neutrons. This study requires a highly flexible choice of the applied magnetic field for neutron spin control and favors longer $T_1$ under lower magnetic field and at higher temperature. The $T_1$ of ${}^{139}\mathrm{La}$ and ${}^{27}\mathrm{Al}$ was measured under magnetic fields of $0.5$-$2.5$ T and at temperatures of $0.1$-$1.5$ K and found widely distributed up to 100 h. The result suggests that the $T_1$ can be as long as $T_1\sim$ 1 h at $0.1$ K with a magnetic field of $0.1$ T, which partially fulfills the requirement of the neutron beam experiment. Possible improvements to achieve a longer $T_1$ are discussed.

    ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·1 citation

* 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.