Fri·May 24, 2024Friday·May 24, 2024

1. 01*

   High-precision spectroscopy of ${}^{20}$O benchmarking ab-initio calculations in light nuclei

   I. Zanon🇮🇹 · E. Clément🇫🇷 · A. Goasduff🇮🇹 · J. Menéndez🇪🇸 · T. Miyagi🇩🇪 · M. Assié🇫🇷 · M. Ciemała🇵🇱 · F. Flavigny🇫🇷 · A. Lemasson🇫🇷 · A. Matta🇫🇷 · D. Ramos🇫🇷 · M. Rejmund🇫🇷 and 69 other authors

   The excited states of unstable ${}^{20}$O were investigated via $\gamma$-ray spectroscopy following the ${}^{19}$O$(d,p{)}^{20}$O reaction at 8 $A$MeV. By exploiting the Doppler Shift Attenuation Method, the lifetime of the 2${}_2^{+}$ and 3${}_1^{+}$ states were firmly established. From the $\gamma$-ray branching and E2/M1 mixing ratios for transitions deexciting the 2${}_2^{+}$ and 3${}_1^{+}$ states, the B(E2) and B(M1) were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of $\gamma$-ray transition probabilities with the valence space in medium similarity renormalization group ab-initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab-initio approaches using chiral EFT forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab-initio models.

   nucl-exnucl-thPRL(2023)·7 citations
2. 02*

   Investigating strangeness enhancement in jet and medium via $\varphi$(1020) production in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   This work aims to differentiate strangeness produced from hard processes (jet-like) and softer processes (underlying event) by measuring the angular correlation between a high-momentum trigger hadron (h) acting as a jet-proxy and a produced strange hadron ($\varphi (1020)$ meson). Measuring h$-\varphi$ correlations at midrapidity in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV as a function of event multiplicity provides insight into the microscopic origin of strangeness enhancement in small collision systems. The jet-like and the underlying-event-like strangeness production are investigated as a function of event multiplicity. They are also compared between a lower and higher momentum region. The evolutions of the per-trigger yields within the near-side (aligned with the trigger hadron) and away-side (in the opposite direction of the trigger hadron) jets are studied separately, allowing for the characterization of two distinct jet-like production regimes. Furthermore, the h$-\varphi$ correlations within the underlying event give access to a production regime dominated by soft production processes, which can be compared directly to the in-jet production. Comparisons between h$-\varphi$ and dihadron correlations show that the observed strangeness enhancement is largely driven by the underlying event, where the $\varphi /\mathrm{h}$ ratio is significantly larger than within the jet regions. As multiplicity increases, the fraction of the total $\varphi (1020)$ yield coming from jets decreases compared to the underlying event production, leading to high-multiplicity events being dominated by the increased strangeness production from the underlying event.

   nucl-exhep-exPRC(2024)·3 citations
3. 03*

   Measurement of the impact-parameter dependent azimuthal anisotropy in coherent ${\rho }^0$ photoproduction in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   This Letter presents the first measurement of the impact-parameter dependent angular anisotropy in the decay of coherently photoproduced ${\rho }^0$ mesons. The ${\rho }^0$ mesons are reconstructed through their decay into pion pairs. The measured anisotropy corresponds to the amplitude of the $\cos (2\varphi )$ modulation, where $\varphi$ is the angle between the two vectors formed by the sum and the difference of the transverse momenta of the pions, respectively. The measurement was performed by the ALICE Collaboration at the LHC using data from ultraperipheral Pb$-$Pb collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV per nucleon pair. Different impact-parameter regions are selected by classifying the events in nuclear-breakup classes. The amplitude of the $\cos (2\varphi )$ modulation is found to increase by about one order of magnitude from large to small impact parameters. Theoretical calculations describe the measured $\cos (2\varphi )$ anisotropy and its impact-parameter dependence as the result of a quantum interference effect at the femtometer scale, arising from the ambiguity regarding which of the nuclei is the photon source in the interaction.

   nucl-exhep-exPLB(2024)·24 citations
4. 04*

   Measurement of the production cross section of prompt ${\Xi }_{\mathrm{c}}^0$ baryons in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The transverse momentum ($p_{\mathrm{T}}$) differential production cross section of the promptly produced charm-strange baryon ${\Xi }_{\mathrm{c}}^0$ (and its charge conjugate $\overline{{\Xi }_{\mathrm{c}}^0}$) is measured at midrapidity via its hadronic decay into ${\pi }^{+}{\Xi }^{-}$ in p$-$Pb collisions at a centre-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The ${\Xi }_{\mathrm{c}}^0$ nuclear modification factor ($R_{\mathrm{pPb}}$), calculated from the cross sections in pp and p$-$Pb collisions, is presented and compared with the $R_{\mathrm{pPb}}$ of ${\Lambda }_{\mathrm{c}}^{+}$ baryons. The ratios between the $p_{\mathrm{T}}$-differential production cross section of ${\Xi }_{\mathrm{c}}^0$ baryons and those of ${\mathrm{D}}^0$ mesons and ${\Lambda }_{\mathrm{c}}^{+}$ baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt ${\Xi }_{\mathrm{c}}^0$ baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p$-$Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model that includes string formation beyond leading-colour approximation or in which hadronisation is implemented via quark coalescence. The $p_{\mathrm{T}}$-integrated cross section of prompt ${\Xi }_{\mathrm{c}}^0$-baryon production at midrapidity extrapolated down to $p_{\mathrm{T}}$ = 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p$-$Pb collisions at midrapidity.

   nucl-exhep-exEPJC(2025)·10 citations
5. 05*

   Charm fragmentation fractions and $\mathrm{c}\overline{\mathrm{c}}$ cross section in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The total charm-quark production cross section per unit of rapidity $\mathrm{d}\sigma (\mathrm{c}\overline{\mathrm{c}})/\mathrm{d}y$, and the fragmentation fractions of charm quarks to different charm-hadron species $f(\mathrm{c}\to {\mathrm{h}}_{\mathrm{c}})$, are measured for the first time in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV at midrapidity ($-0.96<y<0.04$ in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measurements of prompt production of ground-state charm-hadron species: ${\mathrm{D}}^0$, ${\mathrm{D}}^{+}$, ${\mathrm{D}}_{\mathrm{s}}^{+}$, and $J/\psi$ mesons, and ${\Lambda }_{\mathrm{c}}^{+}$ and ${\Xi }_{\mathrm{c}}^0$ baryons. The resulting cross section is $\mathrm{d}\sigma (\mathrm{c}\overline{\mathrm{c}})/\mathrm{d}y=219.6\pm 6.3(stat.){}_{-11.8}^{+10.5}(syst.){}_{-2.9}^{+8.3}(extr.)\pm 5.4(\mathrm{BR})\pm 4.6(lumi.)\pm 19.5(\text{rapidity shape})+15.0({\Omega }_{\mathrm{c}}^0)$ mb, which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at $\sqrt{s}=5.02$ and $13$ TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p$-$Pb collisions compared with ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and ${\mathrm{e}}^{-}\mathrm{p}$ collisions. The $p_{\mathrm{T}}$-integrated nuclear modification factor of charm quarks, $R_{\mathrm{pPb}}(\mathrm{c}\overline{\mathrm{c}})=0.91\pm 0.04(stat.){}_{-0.09}^{+0.08}(syst.){}_{-0.03}^{+0.05}(extr.)\pm 0.03(lumi.)$, is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions.

   nucl-exhep-exEPJC(2024)·13 citations
6. 06*

   Benchmarking the Non-flow Contributions to the Elliptic Flow Parameter ($v_{{}_2}$) in Proton-Proton Collisions

   M. I. Abdulhamid🇪🇬 · A. M. Hamed🇪🇬 · E. A. Osama🇪🇬 · M. Rateb🇪🇬 · N. K. Sadoun🇪🇬 · F. H. Sawy🇪🇬

   This manuscript reports on the elliptic flow parameter, $v_{{}_2}$, in proton-proton (p-p) collisions using PYTHIA8 event generator simulations. The typical Event Plane ($EP$) method $v_{{}_2}$($EP$) as the one used for the real data analysis has been adopted to measure the $v_{{}_2}$ of particles composed of different quark flavors, and produced at mid-pseudorapidity $|\eta |\le 1$ at center-of-mass energy $\sqrt{s}$ = 200 GeV and $\sqrt{s}$ = 13 TeV. The event plane has been constructed using the soft charged particles with transverse momentum ($p{}_{{}_T}<$ 2 GeV/c) produced in various $\eta$ ranges. The pseudorapidity gap technique ($\Delta \eta$) between the particle of interest and the soft charged particles contributed to the event plane constructions has been utilized to benchmark the non-flow contributions. The $v_{{}_2}^{{\pi }^{{}^{\pm },}{\pi }^{{}^0}}$, $v_{{}_2}^{J/\psi ,{\rm Y},K,D,B}$, and the $v_{{}_2}^{{\gamma }_{dir}}$ show similar pattern dependence on the transverse momentum for the same $\Delta \eta$, at both $\sqrt{s}$ = 200 GeV and $\sqrt{s}$ = 13 TeV. At each center-of-mass energy, the measured $v_{{}_2}$ shows obvious dependence on the quark flavor contents where $v_{{}_2}^{{\gamma }_{dir}}$ $\le$ $v_{{}_2}^{J/\psi ,{\rm Y},K,D,B}$ $\le$ $v_{{}_2}^{{\pi }^{{}^{\pm },}{\pi }^{{}^0}}$ for similar $\Delta \eta$ gap. The measured $v_{{}_2}$ shows slightly higher values at smaller $\sqrt{s}$ for particles of similar values of $\Delta \eta$ gaps, particularly at small $\Delta \eta$ gap. The measured $v_{{}_2}$ for all particles shows systematic decreases with increasing the $\Delta \eta$ gap as expected from the previous experimental results. Because PYTHIA8 simulations do not incorporate final state interactions, the $v_{{}_2}(EP)$ values reported here primarily reflect the non-flow contributions and its dependence on the quark contents, pseudorapidity gap as a function on $p_T$ at each center of mass-energy.

   ↳ hep-phhep-exnucl-exJ.Phys.G(2024)·2 citations
7. 07*

   Investigating strangeness enhancement with multiplicity in pp collisions using angular correlations

   ALICE Collaboration

   A study of strange hadron production associated with hard scattering processes and with the underlying event is conducted to investigate the origin of the enhanced production of strange hadrons in small collision systems characterised by large charged-particle multiplicities. For this purpose, the production of the single-strange meson ${\mathrm{K}}_{\mathrm{S}}^0$ and the double-strange baryon ${\Xi }^{\pm }$ is measured, in each event, in the azimuthal direction of the highest-$p_{\mathrm{T}}$ particle (``trigger" particle), related to hard scattering processes, and in the direction transverse to it in azimuth, associated with the underlying event, in pp collisions at $\sqrt{s}=5.02$ TeV and $\sqrt{s}=13$ TeV using the ALICE detector at the LHC. The per-trigger yields of ${\mathrm{K}}_{\mathrm{S}}^0$ and ${\Xi }^{\pm }$ are dominated by the transverse-to-leading production (i.e., in the direction transverse to the trigger particle), whose contribution relative to the toward-leading production is observed to increase with the event charged-particle multiplicity. The transverse-to-leading and the toward-leading ${\Xi }^{\pm }$/${\mathrm{K}}_{\mathrm{S}}^0$ yield ratios increase with the multiplicity of charged particles, suggesting that strangeness enhancement with multiplicity is associated with both hard scattering processes and the underlying event. The relative production of ${\Xi }^{\pm }$ with respect to ${\mathrm{K}}_{\mathrm{S}}^0$ is higher in transverse-to-leading processes over the whole multiplicity interval covered by the measurement. The ${\mathrm{K}}_{\mathrm{S}}^0$ and ${\Xi }^{\pm }$ per-trigger yields and yield ratios are compared with predictions of three different phenomenological models, namely PYTHIA 8.2 with the Monash tune, PYTHIA 8.2 with ropes and EPOS LHC. The comparison shows that none of them can quantitatively describe either the transverse-to-leading or the toward-leading yields of ${\mathrm{K}}_{\mathrm{S}}^0$ and ${\Xi }^{\pm }$.

   ↳ hep-exnucl-exJHEP(2024)·12 citations
8. 08*

   Multiplicity fluctuations and rapidity correlations in ultracentral proton-nucleus collisions

   Rupam Samanta🇵🇱 · Jean-Yves Ollitrault🇫🇷

   A collision between a proton and a heavy nucleus at ultrarelativistic energy creates particles whose rapidity distribution is asymmetric, with more particles emitted in the direction of the nucleus than in the direction of the proton. This asymmetry becomes more pronounced as the centrality estimator, defined from the energy deposited in a calorimeter, increases. We argue that for high-multiplicity collisions, the variation of the impact parameter plays a negligible role, and that the fluctuations of the multiplicity and of the centrality estimator are dominated by quantum fluctuations, whose probability distribution can be well approximated by a correlated gamma distribution. We show that this simple model reproduces existing data, and we make quantitative predictions for collisions in the $0-0.1\%$ and $0-0.01\%$ centrality windows. We argue that by repeating the same analysis with a different centrality estimator, one can obtain direct information about the rapidity decorrelation in particle production.

   ↳ nucl-thnucl-exPLB(2024)·1 citation
9. 09*

   Fully charmed tetraquarks from LHC to FCC: Natural stability from fragmentation

   Francesco Giovanni Celiberto🇪🇸 · Gabriele Gatto🇮🇹 · Alessandro papa🇮🇹

   We investigate the inclusive production of fully charmed tetraquarks, $T_{4c}(0^{++})$ or $T_{4c}(2^{++})$ radial excitations, in high-energy proton collisions. We build our study upon the collinear fragmentation of a single parton in a variable-flavor number scheme, suited to describe the tetraquark formation mechanism from moderate to large transverse-momentum regimes. To this extent, we derive a novel set of DGLAP-evolving collinear fragmentation functions, named TQ4Q1.0 determinations. They encode initial-scale inputs corresponding to both gluon and heavy-quark fragmentation channels, defined within the context of quark-potential and spin-physics inspired models, respectively. We work within the NLL/NLO${}^{+}$ hybrid factorization and make use of the JETHAD numeric interface along with the symJETHAD symbolic calculation plugin. With these tools, we provide predictions for high-energy observables sensitive to $T_{4c}$ plus jet emissions at center-of-mass energies ranging from 14 TeV at the LHC to the 100 TeV nominal energy of the FCC.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2024)·35 citations
10. 10*

    Effectiveness of denoising diffusion probabilistic models for fast and high-fidelity whole-event simulation in high-energy heavy-ion experiments

    Yeonju Go🇺🇸 · Dmitrii Torbunov🇺🇸 · Timothy Rinn🇺🇸 · Yi Huang · Haiwang Yu🇺🇸 · Brett Viren🇺🇸 · Meifeng Lin🇺🇸 · Yihui Ren🇺🇸 · Jin Huang

    Artificial intelligence (AI) generative models, such as generative adversarial networks (GANs), variational auto-encoders, and normalizing flows, have been widely used and studied as efficient alternatives for traditional scientific simulations. However, they have several drawbacks, including training instability and inability to cover the entire data distribution, especially for regions where data are rare. This is particularly challenging for whole-event, full-detector simulations in high-energy heavy-ion experiments, such as sPHENIX at the Relativistic Heavy Ion Collider and Large Hadron Collider experiments, where thousands of particles are produced per event and interact with the detector. This work investigates the effectiveness of Denoising Diffusion Probabilistic Models (DDPMs) as an AI-based generative surrogate model for the sPHENIX experiment that includes the heavy-ion event generation and response of the entire calorimeter stack. DDPM performance in sPHENIX simulation data is compared with a popular rival, GANs. Results show that both DDPMs and GANs can reproduce the data distribution where the examples are abundant (low-to-medium calorimeter energies). Nonetheless, DDPMs significantly outperform GANs, especially in high-energy regions where data are rare. Additionally, DDPMs exhibit superior stability compared to GANs. The results are consistent between both central and peripheral centrality heavy-ion collision events. Moreover, DDPMs offer a substantial speedup of approximately a factor of 100 compared to the traditional Geant4 simulation method.

    ↳ physics.data-anhep-exnucl-exPRC(2024)·10 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.