Nuclear Experiment·nucl-ex

Wed·Jun 17, 2026Wednesday·June 17, 2026

11 papers—7 primary·4 cross-listed

01
Measurement of dijet transverse momentum imbalance and azimuthal acoplanarity in $p$ + $p$ collisions at $s = 200$ GeV with the sPHENIX detector
sPHENIX Collaboration: M. I. Abdulhamid · U. Acharya · E. R. Adams · G. Adawi · I. Ahmed · C. A. Aidala · Y. Akiba · M. Alfred · S. Ali · A. Alsayegh · S. Altaf · H. Amedi and 317 other authors
This Letter reports on measurements of dijet transverse momentum ( $p_{T}$ ) imbalance and azimuthal acoplanarity in proton-proton collisions at $s = 200$ ~GeV, using data recorded by the sPHENIX detector at the Relativistic Heavy Ion Collider corresponding to an integrated luminosity of $41$ ~pb $^{- 1}$ . Jets are reconstructed using the anti- $k_{t}$ algorithm with radius parameters $R = 0.3$ to $0.8$ from electromagnetic and hadronic calorimeter energy deposits. The jet $p_{T}$ resolution is determined directly in data using two independent methods. The dijet $p_{T}$ imbalance is characterized by the ratio $x_{J} = p_{T, 2} / p_{T, 1}$ where $p_{T, 1 (2)}$ is the highest (second-highest) jet $p_{T}$ in the event. The dijet azimuthal acoplanarity $Δ ϕ = ∣ ϕ_{1} - ϕ_{2} ∣$ is also reported. Results are reported for different $p_{T, 1}$ selections and jet radius parameters, normalized per dijet pair, and compared to the results of \textsc{Pythia} and \textsc{Herwig} Monte Carlo event generators. These measurements provide a stringent quantitative test of the modeling of QCD parton shower and hadronization dynamics, place important constraints on event-generator descriptions at RHIC energies, and establish a comprehensive proton-proton baseline for forthcoming measurements of jet modification in heavy ion collisions.
nucl-ex1 citation
02
Measurement of isolated photon plus two-jet correlations in Pb+Pb and $pp$ collisions at 5.02 TeV with ATLAS
ATLAS Collaboration
This paper presents a measurement of photon plus two-jet events in $pp$ and Pb+Pb collisions, i.e. events in which the transverse momentum of a single photon is balanced by two distinct jets. The measurement was performed using $pp$ data taken in 2017 with an integrated luminosity 260 pb $^{- 1}$ , and Pb+Pb data taken in 2018 with an integrated luminosity 1.72 nb $^{- 1}$ , both at $s_{NN}$ =5.02 TeV, as recorded by the ATLAS detector. Events with photons in the transverse momentum range 90-180 GeV and at least two anti- $k_{t}$ $R = 0.2$ jets with a $p_{T}$ > 30 GeV are selected, and three observables are measured: $x_{JJ γ}$ , $A_{JJ γ}$ , and $Δ R_{JJ}$ . These observables characterise the overall energy loss of the multiparton system from medium interactions ( $x_{JJ γ}$ ), the relative energy loss between the two colour-charge carriers ( $A_{JJ γ}$ ), and medium-induced modifications to their opening angle ( $Δ R_{JJ}$ ). The observables are corrected for uncorrelated combinatoric background contributions using a novel multijet mixing technique, for photon purity, and for detector resolution effects via iterative unfolding. Final results are presented per photon, and the ratio ( $I_{AA}$ ) is taken between measurements in Pb+Pb and $pp$ collisions, for Pb+Pb centrality intervals of 30-80%, 10-30%, and 0-10%. Significant suppression of per photon two-jet yields in all three observables, $I_{AA} < 1$ , is observed as a result of parton-medium interactions. The experimental measurements are compared to three different jet quenching models: JEWEL, JETSCAPE, and LBT.
nucl-exhep-ex0 citations
03
Direct Measurement of the $^{212} Pb$ and $^{214} Pb$ $β$ Decay Branching Ratios with the XENONnT Experiment
E. Aprile · J. Aalbers · K. Abe · M. Abu Rmeileh · M. Adrover · S. Ahmed Maouloud · L. Althueser · B. Andrieu · E. Angelino · D. Antón Martin · S. R. Armbruster · F. Arneodo and 169 other authors
We present precision measurements of $^{212} Pb$ and $^{214} Pb$ $β$ decay branching ratios using $^{220} Rn$ and $^{222} Rn$ calibration data from the XENONnT detector, a dual-phase liquid xenon time projection chamber. Characterizing these isotopes is critical, as they lead to significant low-energy backgrounds in rare-event searches. We report ground-state branching ratios of $(14.75 \pm 0.20 (stat)_{- 0.40}^{+ 0.14} (sys)) %$ for $^{212} Pb$ and $(9.8 \pm 0.3 (stat)_{- 0.2}^{+ 0.8} (sys)) %$ for $^{214} Pb$ , providing the most precise direct measurements of these transitions to date. These results contribute to enhancing background modeling for dark matter and neutrino experiments, improving sensitivity to solar neutrinos and physics beyond the Standard Model.
nucl-exhep-ex1 citation
04
Hyperon ( $Λ$ ) polarization along the beam axis in Pb-Pb collisions at $s_{NN} = 5.36$ TeV
ALICE Collaboration
The measurement of hyperon ( $Λ$ and $Λ$ ) polarization along the beam axis in Pb-Pb collisions at $s_{NN} = 5.36$ TeV using the ALICE detector is presented. The polarization, arising from vorticity components induced by anisotropic flow, is studied relative to the second- and third-order event planes. The measured polarization exhibits clear azimuthal sine modulations, providing the first observation of polarization along the beam direction measured relative to the third-order event plane at the Large Hadron Collider. The values of the polarization measured with respect to the second-order event plane relative to the second harmonic event plane are consistent with previous measurements at $s_{NN} = 5.02$ TeV and show improved statistical precision owing to the larger data sample. Comparisons with hydrodynamic calculations indicate that the measured polarization is sensitive to the bulk viscosity and the vortical structure of the quark-gluon plasma, offering new constraints on its transport properties. In particular, the polarization measured relative to the third-order event plane is expected to provide an additional and independent input to constrain both bulk and shear viscosities of the quark-gluon plasma.
nucl-ex0 citations
05
Probing jet evolution with charged energy correlators in small systems
ALICE Collaboration
The ALICE Collaboration presents measurements of charged energy-energy correlators (charged EECs) within charged-particle jets at $s_{NN} = 5.02$ Tev in proton-proton and proton-lead collisions at the LHC. Charged EECs are a class of jet substructure observables that trace the flow of energy and electric charge within a jet, and provide a tool for disentangling the energy scales involved in the jet fragmentation process through the angular separation and charges of particle pairs. The interplay between energy distribution and charge conservation enables charged EECs to provide novel constraints on hadronization mechanisms. Measurements of charged EECs in proton--proton collisions in charged-particle jets with $20 < p_{T, chjet} < 80$ GeV/ $c$ are compared to event generators to investigate different hadronization mechanisms and parton shower models. These model comparisons show that the like-sign EECs are sensitive to changes in parton shower modeling, while unlike-sign EECs are sensitive to different hadronization schemes. Measurements in proton-lead collisions indicate that cold nuclear matter effects on charged EECs are consistent with charge-independent behavior.
nucl-ex3 citations
06
Energy-energy correlators in p-Pb collisions at $s_{NN} = 5.02$ TeV
ALICE Collaboration
This paper presents the first measurement of the two-point energy-energy correlator (EEC) inside charged-particle jets in p-Pb collisions at $s_{NN} = 5.02$ TeV with the ALICE experiment. The two-point EEC, an infrared- and collinear-safe measure of angular energy flow within jets, is used to probe both perturbative and non-perturbative stages of the jet evolution. The EEC is reported in 20-80 GeV/ $c$ jets in p-Pb collisions and compared to a measurement of the EEC in pp events at $s = 5.02$ TeV. A modification is observed in the 20-40 GeV/ $c$ interval, with an enhancement at large opening angles and a suppression at small angles relative to pp collisions. The dependence of this modification on jet transverse momentum, rapidity, and forward activity is investigated. These results provide new constraints on cold nuclear matter effects relevant for disentangling initial- and final-state contributions to jet-structure modifications. An understanding of these cold nuclear matter effects is also relevant for interpreting EEC measurements in heavy-ion collisions.
nucl-ex3 citations
07
Observation of a dominant $0 f_{7/2}$ neutron configuration in the $^{32}$ Si $J^{π} = 5^{-}$ isomeric state
C. R. Hoffman🇺🇸 · G. L. Wilson🇺🇸 · J. Chen🇺🇸 · B. P. Kay🇺🇸 · T. L. Tang🇺🇸 · S. R. Carmichael🇺🇸 · M. Gott · S. Lesher · M. S. Martin · G. E. Morgan · J. Wu🇯🇵
An yrast, $J^{π} = 5^{-}$ , spin-trap isomer has been previously identified in $^{32}$ Si. The isomeric state decays predominantly via a hindered $E 3$ transition [B( $E 3$ ) = 0.0841(10)~W.u.], bypassing a nearby $E 2$ decay path to the first excited $3^{-}$ level. The single-neutron aspects of these negative parity levels were investigated via the $^{31}$ Si $(d$ , $p)^{32}$ Si reaction at 9.6~MeV/ $u$ using HELIOS and the ATLAS in-flight facility. The $5^{-}$ state appears as a dominant $ℓ = 3$ transfer with a relatively large spectroscopic factor, confirming its single-particle $ν 0 f_{7/2}$ character. The yrast $3^{-}$ level had a reduced $ℓ = 3$ spectroscopic factor of $\approx$ 0.44 compared to that of the $5_{1}^{-}$ level. This is similar to the situation observed in nearby $^{34}$ S which by contrast has a measured B( $E 2, 5^{-} \to 3^{-}$ ) transition strength closer to 1~W.u.. It has been concluded that the hinderance of the $5_{1}^{-} \to 3_{1}^{-}$ transition in $^{32}$ Si is not primarily due to the differing overlaps in the neutron structure. Instead, the lack of participation by both the protons and the neutrons in the transition is proposed as the transition-strength reduction mechanism.
nucl-exnucl-thPRC(2026)·0 citations
08
Short-Range Correlations Between Partons in a Proton
Jen-Chieh Peng🇺🇸 · Krishna Rajagopal🇺🇸 · John Terry🇺🇸
A principal lesson from recreating droplets of quark-gluon plasma (QGP) in heavy ion collisions is that it is a strongly coupled liquid, not a plasma of partons. The energy density and pressure of quarks and gluons confined within a proton are comparable to those of QGP at or just above the QCD transition temperature. Given this similarity between protons and QGP, we propose that the investigation of correlations between nearby partons within a proton must be a central goal for the future Electron-Ion Collider (EIC). Here, we ask how EIC measurements can discern such short-range correlations (SRCs) of quark pairs. Doing so would characterize the strongly coupled interior of a proton, augmenting the one-parton-at-a-time understanding of protons via (generalized) parton distribution functions, and could at the same time yield a key ingredient for the microscopic understanding of the liquid nature of QGP. Motivated by the experiments that have been used to demonstrate the existence of SRCs between nucleon pairs within a nucleus, we propose using EIC observables involving measurements of a jet and a pion, together with the scattered electron, to seek and quantify the possible existence of SRCs between quark pairs within a nucleon. The pronounced isospin dependence observed in the dominance of $n p$ SRCs over $pp$ or $nn$ SRCs has played a central role in establishing the importance of SRCs among nucleons in nuclei. Analogously, the QCD attraction in the $u d$ diquark channel can make the $u d$ SRC stronger than the $uu$ and $dd$ SRCs, allowing a first observation of partonic SRCs.
↳ hep-phnucl-exnucl-th0 citations
09
Quantum decoherence of hyperon spin correlations in QCD hadronization
Feng Liu🇺🇸 · Zhoudunming Tu🇺🇸
Hadronization, the transition of quarks and gluons into hadrons, lies beyond the reach of perturbative quantum chromodynamics (QCD) and is commonly described by the semiclassical Lund string model. Yet this very success raises a fundamental question: where does the quantumness go during hadronization? In this Letter, we propose an approach inspired by quantum information science, in which (i) quark-antiquark pairs excited from the QCD vacuum inherit its quantum numbers, giving rise to spin entanglement at their creation, and (ii) subsequent string breaking generates environmental degrees of freedom that induce quantum decoherence of the spin state. This framework simultaneously describes the $Λ$ hyperon spin-correlation data measured at RHIC [Nature 650, 65-71 (2026)] and at the LHC, establishing a quantitative connection between the QCD vacuum, spin entanglement and decoherence, and hadronization.
↳ hep-phhep-exnucl-exnucl-th3 citations
10
Mass Probe of Tetrahedral Symmetry in Atomic Nuclei
F. F. Xu🇨🇳 · P. W. Zhao🇨🇳
Tetrahedral symmetry has long been predicted as an exotic shape degree of freedom in atomic nuclei, yet clear experimental manifestations remain elusive. We show that the triple binding energy difference $δ V_{p n}^{(3)}$ can isolate a structural effect of tetrahedral symmetry in $^{80}$ Zr. Using relativistic density functional theory solved on a three-dimensional lattice without symmetry restrictions, the experimental $δ V_{p n}^{(3)}$ values for even-even $^{80 - 90}$ Zr isotopes are well reproduced without adjustable parameters. While an enhancement of $δ V_{p n}^{(3)}$ near $N ≃ Z$ is commonly attributed to proton-neutron correlations beyond the mean field, the pronounced nonmonotonic peak at $N = 40$ emerges at the mean-field level only when the tetrahedral degree of freedom is included. Constraining the tetrahedral deformation to zero removes the peak and leads to clear deviations from experiment. The anomaly is traced to a well-localized tetrahedral minimum in $^{80}$ Zr, supported by potential energy surfaces and characteristic single-particle level splittings. Calculations restricted to quadrupole and triaxial shapes fail to reproduce the localized enhancement, indicating that the effect is not a generic proton-neutron correlation but a symmetry-selective increase of proton-neutron binding associated with tetrahedral geometry. We therefore identify the $δ V_{p n}^{(3)}$ anomaly in $^{80}$ Zr as a structural mechanism distinct from the conventional Wigner-type enhancement and show that nuclear masses constitute a sensitive probe of tetrahedral symmetry.
↳ nucl-thnucl-ex0 citations
11
Optimized filtering for pulse-shape based pile-up rejection applied to $0 ν β β$ search with $^{100}$ Mo
V. Berest🇫🇷 · M. Buchynska🇫🇷 · P. Carniti🇮🇹 · A. Giuliani🇫🇷 · C. Gotti🇮🇹 · H. Khalife🇫🇷 · P. Loaiza🇫🇷 · P. de Marcillac🇫🇷 · C. Nones🇫🇷 · M. Pageot🇫🇷 · E. Olivieri🇫🇷 · G. Pessina🇮🇹 and 4 other authors
Pile-up events, arising from the partial or complete temporal overlap of distinct signals, represent a major challenge in many areas of experimental physics where rare or low-rate processes are targeted. If not properly identified, pile-up can distort reconstructed observables, degrade energy resolution, and generate backgrounds that mimic genuine events of interest. This work presents an algorithm to obtain an optimized digital filter for the discrimination of pile-up events for detectors with known signal response and stationary noise power spectral density. It is developed in the context of the search for neutrinoless double beta decay with cryogenic Li $_{2}$ $^{100}$ MoO $_{4}$ detectors like CUPID, where pile-up induced background from $^{100}$ Mo $2 ν β β$ is expected to be the leading background contribution. For this application, the new filter discriminant reduces the pile-up induced background (at 90% efficiency) by 31%, compared to an analysis with a reference method previously presented in Eur. Phys. J. C 83(5), 373 (2023). While the discussion is grounded in cryogenic calorimetric detectors, the concepts and methods described are broadly applicable to a wide class of detector technologies and experimental contexts.
↳ physics.ins-dethep-exnucl-ex0 citations

Affiliations

first authorsco-authorsvia INSPIRE