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DOE OSTI2024

Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training

Abstract This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90‐min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O 2 peak) exercise using indirect calorimetry, and 6‐6‐[ 2 H 2 ]‐glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE ( p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased ( p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST ( p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole‐body and skeletal muscle fat metabolism.

Drummer, Devin J.↗

DOE OSTI2026

$\overline{\Sigma }^{\pm }$ production in $\text {pp}$ and $\text {p}{-}\text{Pb}$ collisions at $\sqrt{s_{\textrm{NN}}} = 5.02$ TeV with ALICE

The transverse momentum spectra and integrated yields of anti-$Σ$ hyperons ($\overline{\Sigma}^{\pm}$) have been measured in and collisions at $\sqrt{s_{\textrm{NN}}} = 5.02$ TeV with the ALICE experiment. Measurements are performed via the newly accessed decay channel $\overline{\Sigma}^{\pm}$ → $\bar{\textrm{n}}π^±$. A new method of antineutron reconstruction with the PHOS electromagnetic spectrometer is developed and applied to this analysis. The p T spectra of $\overline{\Sigma}^{\pm}$ are measured in the range 0.5 < p T < 3 GeV/c and compared to predictions of the PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4 models. The EPOS LHC and EPOS4 models provide the best descriptions of the measured spectra both in pp and p-Pb collisions, while models which do not account for multiparton interactions provide a considerably worse description at high p T . The total yields of $\overline{\Sigma }^{\pm }$ in both pp and p-Pb collisions are compared to predictions of the Thermal-FIST model and dynamical models PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4. All models reproduce the total yields in both colliding systems within uncertainties. The nuclear modification factors R pPb for both $\overline{\Sigma}^{+}$ and $\overline{\Sigma}^{-}$ are evaluated and compared to those of protons, $Λ$ and $Ξ$ hyperons, and predictions of EPOS LHC and EPOS4 models. No deviations of R pPb for $\overline{\Sigma}^{\pm}$ from the model predictions or measurements for other hadrons are found within uncertainties.

Abualrob, I. J. [University of Houston] (ORCID:000↗

DOE OSTI2024

Leveraging Calibration Transfer Techniques for Remote Monitoring of Samarium and Europium in LiCl Using Laser-Induced Florescence Spectroscopy for Radioisotope Production Applications

Radioisotope production relies on complex chemical processes that must be performed in radiological hot cells or glove boxes because of the radioactive and otherwise hazardous materials being used. In these situations, optical sensors can provide real-time monitoring to users, which is unobtainable by more traditional methods. This study explores the use of calibration transfer methods to train a model on one instrument and date and then transfer it to another instrument of the same or different configuration on a different date. By performing laser-induced fluorescence measurements of Eu(III) and Sm(III) in 10 M LiCl over the course of 6 months using two disparate spectrometers and two different training sets, a strategy for calibrating and deploying models for online monitoring was established. Three transfer techniques were compared: direct standardization (DS), piecewise direct standardization (PDS), and external parameter orthogonalization (EPO). DS and PDS outperformed EPO for day-to-day transfers, and EPO was not effective for instrument-to-instrument transfers. Transferring the initial date’s full factorial model provided better prediction performance compared with retraining models the day of measurements using a D-optimal designed calibration set. For both day-to-day and instrument-to-instrument transfers, five Kennard–Stone selected samples were sufficient. Based on this choice, the initial-date, high-resolution spectrometer model was transferred to a lower-resolution, compact spectrometer 6 months later to monitor a simulated, real-time demonstration. Here, the combined predictions of the DS and PDS transferred models were able to accurately track the anticipated concentration profiles, maintaining root-mean-square error of prediction values below 10 ppm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Multimuons in cosmic-ray events as seen in ALICE at the LHC

ALICE is a large experiment at the CERN Large Hadron Collider. Located 52 meters underground, its detectors are suitable to measure muons produced by cosmic-ray interactions in the atmosphere. In this paper, the studies of the cosmic muons registered by ALICE during Run 2 (2015–2018) are described. The analysis is limited to multimuon events defined as events with more than four detected muons (N μ > 4) and in the zenith angle range 0° < θ < 50°. The results are compared with Monte Carlo simulations using three of the main hadronic interaction models describing the air shower development in the atmosphere: QGSJET-II-04, EPOS-LHC, and SIBYLL 2.3d. The interval of the primary cosmic-ray energy involved in the measured muon multiplicity distribution is about 4 × 10 15 < E prim < 6 × 10 16 eV. In this interval none of the three models is able to describe precisely the trend of the composition of cosmic rays as the energy increases. However, QGSJET-II-04 is found to be the only model capable of reproducing reasonably well the muon multiplicity distribution, assuming a heavy composition of the primary cosmic rays over the whole energy range, while SIBYLL 2.3d and EPOS-LHC underpredict the number of muons in a large interval of multiplicity by more than 20% and 30%, respectively. The rate of high muon multiplicity events (N μ > 100) obtained with QGSJET-II-04 and SIBYLL 2.3d is compatible with the data, while EPOS-LHC produces a significantly lower rate (55% of the measured rate). For both QGSJET-II-04 and SIBYLL 2.3d, the rate is close to the data when the composition is assumed to be dominated by heavy elements, an outcome compatible with the average energy E prim ∼ 10 17 eV of these events. This result places significant constraints on more exotic production mechanisms.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Ketone monoester plus high‐dose glucose supplementation before exercise does not affect immediate post‐exercise erythropoietin concentrations versus glucose alone

Abstract The objective of this study was to examine the effect of consuming ketone monoester plus a high dose of carbohydrate from glucose (KE + CHO) on the change in erythropoietin (EPO) concentrations during load carriage exercise compared with carbohydrate (CHO) alone. Using a randomized, crossover design, 12 males consumed KE + CHO (573 mg KE/kg body mass, 110 g glucose) or CHO (110 g glucose) 30 min before 4 miles of self‐paced treadmill exercise (KE + CHO:51 ± 13%, CHO: 52 ± 12% V̇O 2peak ) wearing a weighted vest (30% body mass; 25 ± 3 kg). Blood samples for analysis were obtained under resting fasted conditions before (Baseline) consuming the KE + CHO or CHO supplement and immediately after exercise (Post). βHB increased ( p < 0.05) from Baseline to Post in KE + CHO, with no change in CHO. Glucose and glycerol increased ( p < 0.05) from Baseline to Post in CHO, with no effect of time in KE + CHO. Insulin and lactate increased ( p < 0.05) from Baseline to Post independent of treatment. EPO increased ( p < 0.05) from Baseline to Post in KE + CHO and CHO with no difference between treatments. Although KE + CHO altered βHB, glucose, and glycerol concentrations, results from this study suggest that KE + CHO supplementation before load carriage exercise does not enhance immediate post‐exercise increases in EPO compared with CHO alone.

Howard, Emily E.↗

DOE OSTI2025

Light neutral-meson production in pp collisions at $\sqrt{\text{s}}$ = 13 TeV

The momentum-differential invariant cross sections of π 0 and η mesons are reported for pp collisions at $\sqrt{s}$ = 13 TeV at midrapidity (|y| < 0.8). The measurement is performed in a broad transverse-momentum range of 0.2 < p T < 200 GeV/c and 0.4 < p T < 60 GeV/c for the π 0 and η, respectively, extending the p T coverage of previous measurements. Transverse-mass-scaling violation of up to 60% at low transverse momentum has been observed, agreeing with measurements at lower collision energies. Transverse Bjorken x (x T ) scaling of the π 0 cross sections at LHC energies is fulfilled with a power-law exponent of n = 5.01 ± 0.05, consistent with values obtained for charged pions at similar collision energies. The data are compared to predictions from next-to-leading order perturbative QCD calculations, where the π 0 spectrum is best described using the CT18 parton distribution function and the NNFF1.0 or BDSS fragmentation function. Expectations from PYTHIA8 and EPOS LHC overestimate the spectrum for the π 0 and are not able to describe the shape and magnitude of the η spectrum. The charged-particle multiplicity dependent π 0 and η p T spectra show the expected change of the spectral shape, characterized by a flatter slope with increasing multiplicity. This is demonstrated across a broad transverse-momentum range and up to events with a charged-particle multiplicity exceeding five times the mean value in minimum bias collisions. The η/π 0 ratio depends on the charged-particle multiplicity for p T < 4 GeV/c. PYTHIA8 and EPOS LHC qualitatively explain this behavior with an increasing contribution from the feed-down of heavier particles to the π 0 spectrum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2026

Multiplicity dependence of K*(892) ± production in pp collisions at $\sqrt{s}$ = 13 TeV

The first results of K*(892) ± production at midrapidity (|y| < 0.5) in pp collisions at $\sqrt{s}$= 13 TeV as a function of the event multiplicity are presented. The K*(892) ± has been reconstructed via its hadronic decay channel K*(892) ± → π ± + K$^0_{\textrm{S}}$ using the ALICE detector at the LHC. For each multiplicity class, the differential transverse momentum (p T ) spectrum, the mean transverse momentum ⟨p T ⟩, the p T -integrated yield (dN/dy), and the ratio of the K*(892) ± to K$^0_{\textrm{S}}$ yields are reported. These are consistent with previous K*(892) 0 resonance results with a higher level of precision. Comparisons with phenomenological models such as PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY are also discussed. For the first time, a significant K*(892) ± /K$^0_{\textrm{S}}$ suppression in pp collisions is observed at a 7σ level passing from low to high multiplicity events. The ratios of the p T -differential yields of K*(892) ± and K$^0_{\textrm{S}}$ in high and low multiplicity events are also presented along with their double ratio. For p T ≲ 2 GeV/c this double ratio persists below unity by more than 3σ suggesting that the suppression affects mainly low p T resonances. The measured decreasing trend of the K*(892) ± /K$^0_{\textrm{S}}$ ratio with increasing multiplicity, which in heavy-ion collisions is typically attributed to the rescattering of decay particles of the short-lived resonances, is reproduced by the EPOS-LHC model without the use of hadronic afterburners.

Hadronic resonance production↗

DOE OSTI2025

Measurement of the mean number of muons with energies above 500 GeV in air showers detected with the IceCube Neutrino Observatory

We present a measurement of the mean number of muons with energies larger than 500 GeV in near-vertical extensive air showers initiated by cosmic rays with primary energies between 2.5 and 100 PeV. The measurement is based on events detected in coincidence between the surface and in-ice detectors of the IceCube Neutrino Observatory. Air showers are recorded on the surface by IceTop, while a bundle of high-energy muons (TeV muons) from the shower can subsequently produce a tracklike event in the IceCube in-ice array. Results are obtained assuming the hadronic interaction models Sibyll 2.1, QGSJet-II.04, and EPOS-LHC. The measured number of TeV muons is found to be in agreement with predictions from air-shower simulations. The results have also been compared to a measurement of low-energy muons by IceTop, indicating an inconsistency between the predictions for low- and high-energy muons in simulations based on the EPOS-LHC model.

Abbasi, R. [Loyola University Chicago]↗

DOE OSTI2025

Multiplicity-dependent jet modification from di-hadron correlations in pp collisions at $ \sqrt{s} $ = 13 TeV

Short-range correlations between charged particles are studied via two-particle angular correlations in pp collisions at $\sqrt{s}$ = 13 TeV. The correlation functions are measured as a function of the relative azimuthal angle ∆φ and the pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum range 1 < p T < 8 GeV/c. Near-side (|∆φ| < 1.3) peak widths are extracted from a generalised Gaussian fitted over the correlations in full pseudorapidity separation (|∆η| < 1.8), while the per-trigger associated near-side yields are extracted for the short-range correlations (|∆η| < 1.3). Both are evaluated as a function of charged-particle multiplicity obtained by two different event activity estimators. The width of the near-side peak decreases with increasing multiplicity, and this trend is reproduced qualitatively by the Monte Carlo event generators PYTHIA 8, AMPT, and EPOS. However, the models overestimate the width in the low transverse-momentum region (p T < 3 GeV/c). The per-trigger associated near-side yield increases with increasing multiplicity. Although this trend is also captured qualitatively by the considered event generators, the yield is mostly overestimated by the models in the considered kinematic range. The measurement of the shape and yield of the short-range correlation peak can help us understand the interplay between jet fragmentation and event activity, quantify the narrowing trend of the near-side peak as a function of transverse momentum and multiplicity selections in pp collisions, and search for final-state jet modification in small collision systems.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2026

Space-time evolution of particle emission in p–Pb collisions at $\sqrt{{s}_{\text{NN}}} = 5.02$ TeV with 3D kaon femtoscopy

The measurement of three-dimensional femtoscopic correlations between identical charged kaons (K ± K ± ) produced in p–Pb collisions at center-of-mass energy per nucleon pair $\sqrt{{s}_{\text{NN}}}=5.02$ TeV with ALICE at the LHC is presented for the first time. This measurement, supplementary to those in pp and Pb–Pb collisions, allows understanding the particle-production mechanisms at different charged-particle multiplicities and provides information on the dynamics of the source of particles created in p–Pb collisions, for which a general consensus does not yet exist. It is shown that the measured source sizes increase with charged-particle multiplicity and decrease with increasing pair transverse momentum. These trends for K ± K ± are similar to the ones observed earlier in identical charged-pion and ${\text{K}}_{\text{s}}^{0}{\text{K}}_{\text{s}}^{0}$ correlations in Pb–Pb collisions at various energies and in π ± π ± correlations in p–Pb collisions at $\sqrt{{s}_{\text{NN}}}=5.02$ TeV. At comparable multiplicity, the source sizes measured in p–Pb collisions agree within uncertainties with those observed in pp collisions, and there is an indication that they are smaller than those observed in Pb–Pb collisions. The obtained results are also compared with predictions from the hadronic interaction model EPOS 3, which tends to underestimate the source size for the most central collisions and agrees with the data for semicentral and peripheral events. Furthermore, the time of maximal emission for kaons is extracted. It turns out to be comparable with the value obtained in highly peripheral Pb–Pb collisions at the same energy, indicating that the kaon emission evolution is similar to that in p–Pb collisions.

Heavy Ion Experiments↗

DOE OSTI2024

Multiplicity-dependent production of Σ(1385) ± and Ξ(1530) 0 in pp collisions at $\sqrt{s}$ = 13 TeV

The production yields of the Σ(1385) ± and Ξ(1530) 0 resonances are measured in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE. The measurements are performed as a function of the charged-particle multiplicity $\langle$dN ch /dη$\rangle$, which is related to the energy density produced in the collision. The results include transverse momentum (p T ) distributions, p T - integrated yields, mean transverse momenta of Σ(1385) ± and Ξ(1530) 0 , as well as ratios of the p T - integrated resonance yields relative to yields of other hadron species. The Σ(1385) ± /π ± and Ξ(1530) 0 /π ± yield ratios are consistent with the trend of the enhancement of strangeness production from low to high multiplicity pp collisions, which was previously observed for strange and multi-strange baryons. The yield ratio between the measured resonances and the long-lived baryons with the same strangeness content exhibits a hint of a mild increasing trend at low multiplicity, despite too large uncertainties to exclude the flat behaviour. The results are compared with predictions from models such as EPOS-LHC and PYTHIA 8 with Rope shoving. The latter provides the best description of the multiplicity dependence of the Σ(1385) ± and Ξ(1530) 0 production in pp collisions at $\sqrt{s}$ = 13 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2026

Strangeness enhancement at its extremes: multiple (multi-)strange hadron production in pp collisions at $\sqrt{s}=5.02$ TeV

The probability to observe a specific number of strange and multi-strange hadrons (nS), denoted as P(nS), is measured by ALICE at midrapidity (|y| < 0.5) in $$\sqrt{s}=5.02$$ TeV proton-proton (pp) collisions, dividing events into several multiplicity-density classes. Exploiting, for the first time, a technique based on counting the number of strange-particle candidates event-by-event, this measurement allows one to extend the study of strangeness production beyond the mean of the distribution. This constitutes a new test bench for production mechanisms, probing events with a large imbalance between strange and non-strange content. The analysis of a large-statistics data sample makes it possible to extract P(nS) up to a maximum nS of 7 for $${\text{K}}_{\text{S}}^{0}$$, 5 for Λ and $$\overline{\Lambda }$$, 4 for Ξ− and $${\overline{\Xi } }^{+}$$, and 2 for Ω− and $${\overline{\Omega } }^{+}$$. From this, the probability of producing strange hadron multiplets per event is calculated, thereby enabling the extension of the study of strangeness enhancement to extreme situations where several strange quarks hadronize in a single event at midrapidity. Moreover, comparing hadron combinations with different u and d quark compositions and equal overall s quark content, the contribution to the enhancement pattern coming from non-strangeness related mechanisms is isolated. The results are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, including PYTHIA 8 Monash 2013, PYTHIA 8 with QCD-based Color Reconnection and Rope Hadronization (QCD-CR + Ropes), and EPOS LHC, which incorporates both partonic interactions and hydrodynamic evolution. These comparisons show that the new approach dramatically enhances the sensitivity to the different underlying physics mechanisms modeled by each generator.

Abualrob, I J↗

DOE OSTI2025

Measurement of correlations among net-charge, net-proton, and net-kaon multiplicity distributions in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Correlations among conserved quantum numbers, such as the net-electric charge, the net-baryon, and the net-strangeness in heavy-ion collisions, are crucial for exploring the QCD phase diagram. In this paper, these correlations are investigated using net-proton number (as a proxy for the net-baryon), net-kaon number (for the net-strangeness), and net-charged particle number in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with the ALICE detector. The observed correlations deviate from the Poissonian baseline, with a more pronounced deviation at LHC energies than at RHIC. Theoretical calculations of the Thermal-FIST hadron resonance gas model, HIJING, and EPOS LHC event generators are compared with experimental results, where a significant impact of resonance decays is observed. Thermal-FIST calculations under the grand canonical and canonical ensembles highlight significant differences, underscoring the role of local charge conservation in explaining the data. Recent lattice QCD studies have demonstrated that the magnetic field generated by spectator protons in heavy-ion collisions affects susceptibility ratios, in particular those related to the net-electric charge and the net-baryon numbers. The experimental findings are in qualitative agreement with the expectations of lattice QCD.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Investigating strangeness enhancement with multiplicity in pp collisions using angular correlations

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 ${\textrm{K}}_{\textrm{S}}^0$ and the double-strange baryon Ξ ± is measured, in each event, in the azimuthal direction of the highest-p 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 ${\textrm{K}}_{\textrm{S}}^0$ and Ξ ± 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 Ξ ± /${\textrm{K}}_{\textrm{S}}^0$ 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 Ξ ± with respect to ${\textrm{K}}_{\textrm{S}}^0$ is higher in transverse-to-leading processes over the whole multiplicity interval covered by the measurement. The ${\textrm{K}}_{\textrm{S}}^0$ and Ξ ± per-trigger yields and yield ratios are compared with predictions of three different phenomenological models, namely Pythia8.2 with the Monash tune, Pythia8.2 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 ${\textrm{K}}_{\textrm{S}}^0$ and Ξ ± .

hadron-hadron scattering↗

DOE OSTI2024

Rapidity dependence of antideuteron coalescence in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

The production yields of antideuterons and antiprotons are measured in pp collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV, as a function of transverse momentum ( p T ) and rapidity ( y ), for the first time rapidity-differentially up to | y | = 0.7. The measured spectra are used to study the p T and rapidity dependence of the coalescence parameter B 2 , which quantifies the coalescence probability of antideuterons. The p T and rapidity dependence of the obtained B 2 is extrapolated for p T > 1.7 GeV/ c and | y | = 0.7 using the phenomenological antideuteron production model implemented in Pythia 8.3 as well as a baryon coalescence afterburner model based on EPOS 3. Such measurements are of interest to the astrophysics community, since they can be used for the calculation of the flux of antinuclei from cosmic rays, in combination with coalescence models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Measurement of 𝜔 meson production in 𝑝⁢𝑝 and 𝑝-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

We present the measurement of the 𝑝 T -differential production cross section of 𝜔 mesons in pp and 𝑝-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV at midrapidity by ALICE. In addition, the first measurement of the nuclear modification factor 𝑅 𝑝⁢Pb for 𝜔 mesons at LHC energies is presented, complementing the existing measurements of lighter neutral mesons such as the 𝜋 0 and 𝜂. Within the measured 𝑝 T range, the 𝑅 𝑝⁢Pb of 𝜔 mesons is compatible with no cold nuclear matter effects within the uncertainties, consistent with previous measurements at lower energies. The 𝜔/𝜋 0 ratio is presented for both collision systems, showing no collision system dependence within the uncertainties. The comparison to previously published 𝜔/𝜋 0 ratios at lower and higher collision energies in pp collisions suggests a decreasing trend of the ratio above 𝑝T = 4 GeV/𝑐 with increasing collision energy. The data in both collision systems are compared to predictions from PYTHIA 8, EPOS LHC, and DPMJET event generators, revealing significant shortcomings in these models’ ability to describe the production of 𝜔 mesons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

New proxies for second-order cumulants of conserved charges in heavy-ion collisions within the EPOS4 framework

Proxies for cumulants of baryon number 𝐵, electric charge 𝑄, and strangeness 𝑆 are usually measured in heavy-ion collisions via moments of net-number distribution of given hadronic species. Since these cumulants of conserved charges are expected to be sensitive to the existence of a critical point in the phase diagram of nuclear matter, it is crucial to ensure that the proxies used as substitutes are as close to them as possible. Hence, we use the EPOS 4 framework to generate Au + Au collisions at several collision energies of the BNL Relativistic Heavy Ion Collider beam energy scan. We compute second-order net cumulants of 𝜋, 𝐾, and 𝑝, for which experimental data have been published as well as the corresponding conserved charge cumulants. We then compare them with proxies, defined in previous lattice QCD and hadron resonance gas model studies, which are shown to reproduce more accurately their associated conserved charge cumulants. We investigate the impact of hadronic rescatterings occurring in the late evolution of the system on these quantities, as well as the amount of signal actually originating from the bulk medium which endures a phase transition.

Physics↗

DOE OSTI2025

Particle production as a function of charged-particle flattenicity in 𝑝⁢𝑝 collisions at $\sqrt{s}$ = 13 TeV

This paper reports the first measurement of the transverse momentum (𝑝 T ) spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at $\sqrt{s}$ =13 TeV. Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, 2.8 < 𝜂 < 5.1 and −3.7 < 𝜂 < −1.7. According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases toward larger 𝑝 T due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to 𝑝 T = 20 GeV/⁢𝑐. The event selection requires at least one charged particle produced in the pseudorapidity interval |𝜂| < 1. The measured 𝑝 T distributions, average 𝑝 T , kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using pythia 8 based on color strings and EPOS LHC. The modification of the 𝑝 T -spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate 𝑝 T (2 < 𝑝 T < 8 GeV/𝑐), and approaches the vicinity of unity at higher 𝑝 T . The results are qualitatively described by pythia, and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗