Nuclear Experiment·nucl-ex

Fri·Jun 19, 2026Friday·June 19, 2026

11 papers—7 primary·4 cross-listed

01
Evidence for parton energy loss in oxygen $-$ oxygen collisions at $s_{NN} = 5.36$ TeV
ALICE Collaboration
Ultra-relativistic heavy-ion collisions create a hot and dense medium of deconfined quarks and gluons, the quark $-$ gluon plasma (QGP), in which parton energy loss ("jet quenching") is a key probe of hot medium properties. While parton energy loss has been firmly established in large systems such as Pb $-$ Pb and Au $-$ Au collisions, no unambiguous direct evidence exists in smaller systems such as high-multiplicity p $-$ Pb and pp collisions. To probe the onset of parton energy loss at intermediate system size, measurements of neutral-pion production are presented in this Letter for oxygen $-$ oxygen (OO) and proton $-$ oxygen (pO) collisions recorded with the ALICE detector in July 2025, relative to a pp baseline. The nuclear modification factor $R_{OO}$ is suppressed relative to unity with a transverse-momentum dependence similar to that observed in Pb $-$ Pb collisions, consistent with a previous CMS measurement in OO collisions with charged particles. As $R_{OO}$ contains contributions from both cold and hot nuclear matter effects, $R_{pO}$ is also presented in order to constrain cold nuclear matter (CNM) contributions. $R_{pO}$ is found to be compatible with unity, indicating that CNM effects alone cannot account for the suppression observed in $R_{OO}$ . Final-state effects are isolated using the measured double ratio $R_{OO} / R_{pO}^{2}$ , which largely cancels CNM contributions and exhibits a significant suppression relative to expectations without energy loss at a 4.9 $σ$ level. Theoretical models incorporating parton energy loss via different mechanisms predict a significant suppression of the $R_{OO} / R_{pO}^{2}$ relative to unity, consistent with the data. These findings establish parton energy loss in OO collisions, extending experimental evidence for jet quenching to the smallest nuclear system studied to date.
nucl-ex12 citations
02
Probing flavor effects in the QCD parton shower using $D^{0}$ -tagged jet angularities in proton $-$ proton collisions at $s = 5.02$ TeV
ALICE Collaboration
The ALICE Collaboration presents the first measurements of $D^{0}$ -tagged jet angularities in proton $-$ proton (pp) collisions at $s = 5.02$ TeV. Jet angularities are powerful substructure observables that characterize the angular and momentum distributions of particles within jets via tunable weighting parameters. Varying the angular parameter in jet angularities allows for a systematic probe of the sensitivity to collinear and soft radiation, enabling the study of flavor-dependent fragmentation and hadronization through comparisons of jets initiated by different partons. This paper reports $D^{0}$ -tagged and inclusive (gluon-dominated) charged-particle jet angularities with a resolution parameter $R = 0.4$ in the low jet transverse momentum range ( $10 < p_{T}^{ch. jet} < 20$ GeV/ $c$ ), where charm-quark mass effects are most significant. At low angular weight, which emphasizes collinear radiation, $D^{0}$ -tagged jets exhibit smaller angularity values than inclusive jets. This provides evidence for the radiation suppression from massive quarks -- a phenomenon known as the QCD dead-cone effect. As the angular weight increases, giving more emphasis to wide-angle radiation, the difference between $D^{0}$ -tagged and inclusive jet distributions decreases. This indicates that the modification is concentrated within the jet core rather than its edge. PYTHIA 8 simulations qualitatively reproduce both the angularity of $D^{0}$ -tagged and inclusive charged-particle jets, but reproduce the $D^{0}$ -tagged jet distributions better than those of inclusive jets, offering a powerful new constraint for models. These results provide insight into flavor-dependent fragmentation and establish an essential baseline for future studies of jet modifications in the quark-gluon plasma produced in heavy-ion collisions.
nucl-exnucl-th0 citations
03
Modification of jet-energy flow in heavy-ion collisions
ALICE Collaboration
The ALICE Collaboration presents the first measurements of the jet-energy flow ( $Δ p_{T}$ ) observable in proton-proton and heavy-ion collisions. Jets are excellent probes for the quark $-$ gluon plasma, a deconfined state of matter produced in heavy-ion collisions. The jet-energy flow observable characterizes the radial distribution of energy from the jet axis in an infrared and collinear-safe way and is sensitive to medium-induced parton-shower modifications. Inclusive charged jets are measured in Pb $-$ Pb collisions at $s_{NN} = 5.02$ TeV for the transverse-momentum interval 60 $-$ 80 GeV/ $c$ . For pp collisions at $s = 13$ TeV, measurements include the 40 $-$ 60 and 60 $-$ 80 GeV/ $c$ intervals, where the latter serves as the reference for investigating medium-induced modifications. Results show that most parton energy is concentrated in the jet core, with a clear suppression of energy flow in heavy-ion collisions at larger radii (significance 3.5 $-$ 4.5 $σ$ ) indicating a narrowing of the energy flow. While all models -- PYTHIA 8, HERWIG, JEWEL, and JETSCAPE -- reproduce the pp results with only small deviations in the tails, the relative modification in Pb $-$ Pb collisions is well described by JEWEL without recoil. Conversely, JEWEL with recoil (medium response) and JETSCAPE show significant deviations, exhibiting increasing or more constant trends with radius that are disfavored by the data.
nucl-ex0 citations
04
Precision mass measurements of multistrange baryons and their antiparticles
ALICE Collaboration
The $Ω^{-}$ baryon, composed of three strange quarks (sss), was predicted by the quark model and discovered in 1964, playing a pivotal role in establishing quarks as fundamental constituents of matter. Despite its importance, experimental knowledge of its mass remains limited, with the current world average relying on measurements performed more than four decades ago and lacking robust estimates of systematic uncertainties. This is notable given the central role of the $Ω^{-}$ mass, and alternatively that of the $Ξ^{-}$ (dss), in lattice QCD calculations, where it is widely used to set the overall physical scale. Precise scale setting is essential for first-principles studies of quark confinement, chiral symmetry breaking, and stringent tests of the Standard Model. Here we report high-precision measurements of the masses of the $Ω^{-}$ and $Ξ^{-}$ baryons and their antiparticles, determined from invariant-mass reconstruction of their decay products in proton $-$ proton collisions at the LHC. The analysis exploits the excellent tracking and particle-identification capabilities of the ALICE experiment, enabling accurate reconstruction of the displaced decay vertices characteristic of these short-lived particles. Each mass is measured with a fractional uncertainty of about 60 parts per million, for example $M_{Ω ˉ^{+}} = 1672.558 \pm 0.034 (stat.) \pm 0.102 (syst.)$ MeV/ $c^{2}$ . The precisely known K $_{S}^{0}$ and $Λ$ masses are used for calibration. These results establish new precision benchmarks in strange-baryon spectroscopy and enable stringent tests of Charge-Parity-Time invariance in the multistrange-hadron sector. Our measurement reduces the scale uncertainty in lattice QCD calculations, enabling for instance sub per mille precision for the hadronic vacuum-polarization contribution to the muon anomalous magnetic moment.
nucl-exhep-ex0 citations
05
Probing Strange-Quark Hadronization via (Multi-)Strange Hadron Multiplicity Distributions in Small Collision Systems with ALICE
Sara Pucillo🇮🇹
Strangeness enhancement is defined as the increased relative production of strange hadrons in heavy-ion collisions compared to proton--proton (pp) interactions. It was originally proposed as one of the signatures of quark--gluon plasma (QGP) formation. At the LHC, the ALICE experiment observed that strange-hadron-to-pion yield ratios rise with increasing charged-particle multiplicity at midrapidity, independently of collision energy ( $s$ ) and system size, from pp to p--Pb and up to Pb--Pb collisions. To gain deeper insight into the mechanisms of strangeness production, the ALICE collaboration has measured the probability distribution of producing a given number of strange particles ( $K_{S}^{0}$ , $Λ$ , $Ξ$ , and $Ω$ ) of the same species per event in pp collisions at $s = 5.02$ TeV. This measurement extends the study of strangeness production beyond the mean particle yield by employing, for the first time, a technique based on event-by-event particle counting. It provides a new test bench for production mechanisms, probing events with large imbalances between strange and non-strange content. The results are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, offering enhanced sensitivity to the underlying dynamics of strangeness production.
nucl-exhep-ex0 citations
06
Measurements of charged-particle pseudorapidity and transverse momentum distributions in O+O and Ne+Ne collisions at $s_{_{NN}} = 5.36$ TeV with the ATLAS detector
ATLAS Collaboration
Measurements of charged-particle transverse momentum spectra, multiplicity, and mean transverse momentum are presented as a function of pseudorapidity and collision centrality in O+O and Ne+Ne collisions at $s_{_{NN}} = 5.36$ TeV using 27.7 $μ b^{- 1}$ and 53.1 $μ b^{- 1}$ data sets recorded by the ATLAS experiment at the LHC. The collision centrality is characterized by the total transverse energy measured in the ATLAS forward calorimeters. The kinematics of charged particles are reconstructed with the inner detector over the fiducial pseudorapidity and transverse momentum ranges $∣ η ∣ < 2.5$ and $0.27 < p_{T} < 5$ GeV using data from the ATLAS inner detector. The per-event charged-particle pseudorapidity density $d n / d η$ and mean transverse momentum $⟨ p_{T} ⟩$ are measured over this fiducial range as a function of $η$ . The results are reported in 5%-wide centrality intervals covering the 5-80% centrality range, and in 1%-wide intervals covering the 0-5% centrality range. Invariant per-event yields are evaluated as a function of $η$ and $p_{T}$ . Their $p_{T}$ dependence is fitted to estimate extrapolated $d n / d η$ and $⟨ p_{T} ⟩$ values over $0 < p_{T} < 5$ GeV. To evaluate the impact of using pseudorapidity instead of rapidity, measurements are also performed as a function of rapidity computed using a pion mass hypothesis. The fiducial and extrapolated results are compared with hydrodynamic calculations.
nucl-exhep-ex4 citations
07
Observation of centrality-dependent dijet transverse momentum imbalance in O+O and Ne+Ne collisions at $s_{N N}$ = 5.36 TeV with the ATLAS detector
ATLAS Collaboration
The ATLAS experiment presents an observation of a centrality-dependent dijet transverse momentum imbalance in O+O and Ne+Ne collisions at a nucleon-nucleon center-of-mass energy of 5.36 TeV at the Large Hadron Collider. The measurement uses 8.0 nb $^{- 1}$ of O+O and 1.0 nb $^{- 1}$ of Ne+Ne data collected in 2025, together with 386 pb $^{- 1}$ of \textit{pp} data at the same energy used as a reference. The dijet momentum balance is quantified using the ratio of the sub-leading jet transverse momentum to that of the leading jet, $x_{J}$ . For dijets produced azimuthally back-to-back, the self-normalized $x_{J}$ distributions exhibit increasingly large deviations from the \textit{pp} reference as collisions become more central, corresponding to an increasing overlap of the colliding nuclei. The observed centrality dependence is consistent with medium-induced partonic energy loss in O+O and Ne+Ne collisions, demonstrating that such effects persist in collision systems considerably smaller than Pb+Pb and Xe+Xe. These results establish a new regime for investigating the path-length dependence of jet quenching and constrain the onset of quark-gluon plasma effects in small nuclear collision systems.
nucl-exhep-ex5 citations
08
Self-Calibration of the Neutrino-Argon Cross Section with Solar Neutrinos
Rasmi Hajjar🇺🇸 · Obada Nairat🇺🇸 · John F. Beacom🇺🇸
The success of DUNE's MeV physics program depends upon high-precision knowledge of the charged-current (CC) $ν_{e} +^{40} Ar$ cross section. While there are indirect constraints at the 10% level for the nuclear transitions that constitute this cross section, the only direct measurement in the MeV range has an uncertainty of $\sim$ 50%. We show, surprisingly, that the cross section can be precisely measured using the solar-neutrino data themselves. This is possible because of independent knowledge of the $^{8}$ B flux and survival probability, plus the distinctive angular distributions of the Fermi and Gamow-Teller transitions that comprise the cross section. We propose new methods to extract the transition strengths, considering both intuitive groupings and a Principal Component Analysis. Under pessimistic assumptions about detection, but taking detector uncertainties to be controlled, we demonstrate that a precision of $≲$ 2% on the cross section can be achieved in the 9-15 MeV energy range. These results will be an important foundation for studying the cross section up to several tens of MeV, where the complexity increases significantly due to nuclear breakup channels but where reducing uncertainties is critical for supernova and atmospheric neutrino studies.
↳ hep-phhep-exnucl-exnucl-th0 citations
09
The Silicon Tracking System of the E16 experiment at J-PARC: construction, installation and commissioning in beam test experiments
Dairon Rodríguez Garcés🇩🇪 · Rento Yamada🇯🇵 · Kazuya Aoki🇯🇵 · Lady Maryann Collazo Sánchez · David Emschermann🇩🇪 · Hideto En'yo🇯🇵 · Jürgen Eschke · Ulrich Frankenfeld · David Gutiérrez Menéndez · Johann M. Heuser🇩🇪 · Masaya Ichikawa🇯🇵 · Ralf Kapell and 28 other authors
The J-PARC E16 experiment aims to search for signatures of chiral symmetry restoration. It studies in-medium modifications of vector mesons that decay via the dielectron channel. The measurements use a high-intensity 30 GeV proton beam with C and Cu targets at rates up to 10 MHz. To achieve this, the experiment upgrades its tracking, by introducing innermost detector modules constructed with the same technology and procedures as the modules of the Silicon Tracking System (STS) of the Compressed Baryonic Matter (CBM) experiment at Facility for Antiproton and Ion Research (FAIR). A total of 15 modules were assembled, tested, characterized and then installed in the E16 detector setup. The detector was commissioned in a beam test experiment at Tsukuba, where the detector modules could be exposed to a 3 GeV electron beam. In preparation for the beam test the modules were characterized and calibrated, and performance studies were accomplished to assess the quality of the setup. During beamtime, three modules were operated and illuminated in two planes by the electron beam. This paper presents the results of the construction, characterization, commissioning, and operation of the E16-STS modules in beam test experiments.
↳ physics.ins-detnucl-ex0 citations
10
Toward Precision Fragmentation of $Ω_{3 Q}$ Baryons: The OMG3Q1.1 Framework
Francesco Giovanni Celiberto🇪🇸
Recent experimental advances in the baryon sector, including the observation of doubly charmed states, have renewed interest in the production mechanisms of increasingly heavy hadronic systems, calling for precision and uncertainty-controlled descriptions. We present the OMG3Q1.1 framework for the fragmentation of same-flavor all-heavy $Ω_{3 Q}$ baryons in high-energy hadronic collisions. The construction combines diquark-inspired inputs for constituent-heavy-quark and gluon channels with threshold-aware DGLAP evolution within the HF-NRevo scheme. A replica-based strategy consistently quantifies perturbative missing-higher-order effects (F-MHOUs) and nonperturbative wave-function uncertainties (F-NPWFs), yielding the first uncertainty-resolved fragmentation-function set for the $Ω_{3 Q}$ sector. The resulting LHAPDF6 grids are employed to investigate semi-inclusive $Ω_{3 Q}$ plus jet production at the HL-LHC and future FCC within the (sym)JETHAD environment. The OMG3Q1.1 framework establishes a precision-oriented baseline for rare triply heavy baryons and provides a foundation for future studies of the heavy-flavor baryon landscape.
↳ hep-phhep-exnucl-exnucl-th4 citations
11
Ultra high-energy neutrino at GZK energy: Z-WW showering in dark halo and tau airshowers emerging from the Earth
D. Fargion🇮🇹
Relic neutrino nu_r light masses clustering in Galactic and Local Hot Dark Halos act as a beam dump calorimeter. Ultra High Energy nu, above ZeV, born by AGNs, GRBs at cosmic edges, overcoming (GZK) cut-off, may hit near Z resonance and WW-ZZ channels energies: their showering into UHECR fit observed data . Any tiny neutrino mass splitting may reflect into a twin bump at highest GZK energy cut-off. The Z or WW,ZZ showering explain a peculiar clustering in observed UHECR spectra at 10^19, 210^19, 4 10^19 eV found by AGASA. Coincidence of clustered UHECR with highest gamma BLac sources is well tuned to Z-Showering Scenario. Additional prompt TeVs signals occur offering a natural solution of growing Infrared-TeV cut-off paradoxes related to distant TeV BLac sources and a GRB at TeV energy. Electromagnetic Cascades tail explain correlation found between GeV-EGRET Sources and UHECR. Such UHE nu Astrophysics might trace into Horizontal Tau Air-Showers originated by the UHE nu_tau Earth-Skimming in wide Corona Earth Crust around the observer. These Upward and Horizontal tau Air-Showers UPTAUS, HORTAUS, monitor huge volumes from high mountains as well as observing from planes, balloons and satellites. HORTAUS from mountains observe corona masses at UHE neutrino at EeVs energies comparable to few km^3, while from satellites at orbit altitudes, at GZK energies, their corresponding Horizontal Corona Masses may even exceed 150 km^3. The expected event rate may exceed a dozen of event a year in Z-WW Showering model from satellite.
↳ hep-phastro-phastro-ph.HEnucl-exProc.SPIE Int.Soc.Opt.Eng.(2003)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE