We investigate medium-induced modifications to jet substructure observables that characterize hard components in central Pb-Pb collisions at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>5.02</mn></mrow></math> TeV. Using a multistage Monte Carlo simulation of in-medium jet shower evolution, we explore flavor-dependent medium effects through simulations of inclusive and <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>γ</mi></math>-tagged jets. The results show that quark jets undergo a nonmonotonic modification compared with gluon jets in observables such as the Pb-Pb to <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>p</mi><mtext>−</mtext><mi>p</mi></mrow></math> ratio of the soft drop prong angle <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>r</mi><mi>g</mi></msub></math>, the relative prong transverse momentum <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>k</mi><mrow><mi>T</mi><mo>,</mo><mi>g</mi></mrow></msub></math>, and the groomed mass <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>m</mi><mi>g</mi></msub></math> distributions. Due to this nonmonotonic modification, <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>γ</mi></math>-tagged jets, enriched in quark jets, provide surprisingly clear signals of medium-induced structural modifications, distinct from effects dominated by selection bias. Further systematic studies demonstrate that these effects are dominated by recoil medium response. This work highlights the potential of hard substructures in <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>γ</mi></math>-tagged jets as powerful tools for probing the jet-medium interactions in high-energy heavy-ion collisions, in particular by enabling detailed investigations of jet-medium parton scatterings via their associated medium response. All simulations for <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>γ</mi></math>-tagged jet analyses carried out in this paper used triggered events containing at least one hard photon, which highlights the utility of these observables for future Bayesian analysis.

Japan

Y. Tachibana

United States

C. Sirimanna

A. Majumder

A. Angerami

R. Arora

S.A. Bass

Y. Chen

R. Datta

Canada

L. Du

R. Ehlers

Germany

H. Elfner

R.J. Fries

C. Gale

China

Y. He

B.V. Jacak

P.M. Jacobs

S. Jeon

Y. Ji

F. Jonas

L. Kasper

M. Kordell

A. Kumar

R. Kunnawalkam-Elayavalli

J. Latessa

Y.J. Lee

United Kingdom

R. Lemmon

Brazil

M. Luzum

S. Mak

A. Mankolli

C. Martin

H. Mehryar

T. Mengel

C. Nattrass

J. Norman

C. Parker

J.F. Paquet

J.H. Putschke

H. Roch

G. Roland

B. Schenke

L. Schwiebert

A. Sengupta

C. Shen

M. Singh

D. Soeder

R.A. Soltz

Finland

I. Soudi

J. Velkovska

G. Vujanovic

X.N. Wang

X. Wu

W. Zhao

Effect of recoils on soft-drop-groomed observables in <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>γ</mi></math>-tagged jets in a multistage approach

Studying experimental observables is a key benchmark for validating theoretical models in high energy physics. In this work, we employ the PACIAE 4.0 model to simulate nonsingle diffractive proton-proton (<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>p</mi><mi>p</mi></mrow></math>) collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV, comparing the results with compact muon solenoid (CMS) experimental data on charged-particle pseudorapidity densities and transverse momentum spectra across different pseudorapidity bins, respectively. Our results show good agreement with the CMS data, particularly only using a single set of parameters for all collision energies. This demonstrates that the PACIAE 4.0 model can serve as a reliable tool for systematically studying the physics of NSD <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>p</mi><mi>p</mi></mrow></math> collisions.

Zhen Xie

An-Ke Lei

Hua Zheng

Wen-Chao Zhang

Dai-Mei Zhou

Zhi-Lei She

Yu-Liang Yan

Ben-Hao Sa

Pseudorapidity dependence of charged-particle production in nonsingle diffractive <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>p</mi><mi>p</mi></mrow></math> collisions in the PACIAE 4.0 model

We show that a very clear signal of the presence of a strong magnetic field during the early stage of a high-energy heavy-ion collision is provided by the decay of the <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Z</mi><mn>0</mn></msup></math> into dimuon pairs. We find that the process is highly anisotropic, producing pairs mainly out of plane, as signaled by a negative value of <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>2</mn></msub></math>, and leads to an antimuon transverse momentum distribution which peaks at a higher value of the transverse momentum compared to the peak of the muon transverse momentum distribution. We also show that the process does not produce a significant distortion of the <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Z</mi><mn>0</mn></msup></math> spectral function. The signal can be identified by comparing the dimuon-invariant mass and the individual muon and antimuon spectra produced in semicentral heavy-ion collisions with the corresponding scaled spectra produced in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>p</mi><mo>+</mo><mi>p</mi></mrow></math> collisions at the <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Z</mi><mn>0</mn></msup></math> peak.

Mexico

Alejandro Ayala

Chile

Ana Julia Mizher

Javier Rendón

Asymmetric muon-antimuon emission from <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Z</mi><mn>0</mn></msup></math> decays: A potential magnetometer in relativistic heavy-ion collisions

We study the internal structure of exotic hadrons, especially focusing on the relation between the compositeness and physical observables. Defined as the probability of finding hadronic molecular components in the wave function, compositeness serves as a quantitative measure of the internal structure of exotic hadrons. We utilize the coupled-channel potential model incorporating both quark and hadron degrees of freedom, which naturally generate the “bare state” responsible for the elementary component as the bound state in the quark channel. The behavior of the compositeness under the variation of the model parameters is investigated by using the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></mrow></math> as an example. In particular, we analyze the associated scattering phase shifts and the bound-state wave functions to discuss the relation between the compositeness and the scattering observables for a shallow bound state. As a phenomenological application of the present framework, the compositeness of the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></mrow><mo>,</mo><mo> </mo><mrow><msub><mi>T</mi><mrow><mi>c</mi><mi>c</mi></mrow></msub><mrow><mo>(</mo><mn>3875</mn><mo>)</mo></mrow></mrow><mo>,</mo><mo> </mo><mrow><msub><mi>D</mi><mrow><mi>s</mi><mn>0</mn></mrow></msub><mrow><mo>(</mo><mn>2317</mn><mo>)</mo></mrow></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>D</mi><mrow><mi>s</mi><mn>1</mn></mrow></msub><mrow><mo>(</mo><mn>2460</mn><mo>)</mo></mrow></mrow></math> is discussed.

Ibuki Terashima

Tetsuo Hyodo

Compositeness and wave function of shallow bound states in relation to scattering observables

We investigate charge-balance functions for pion, kaon, and proton pairs in proton-proton (pp) collisions at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn></mrow></math> TeV using Monte Carlo models, pythia8, and epos-lhc, with transverse spherocity to classify event topology and charged-particle multiplicity to select system size. Simulations with pythia8 and epos-lhc reveal that balance-function widths in rapidity and azimuthal angle depend on multiplicity and event shape. In pythia8, widths decrease monotonically with multiplicity, consistent with local charge conservation in a fragmentation-dominated scenario. In contrast, the epos-lhc model, especially when using the core corona implementation, exhibits a more intricate response, where the combined effects of hydrodynamic radial flow and longitudinal diffusion result in narrower azimuthal correlations and broader rapidity correlations. These features are characteristic signatures of collective dynamics, similar to those observed in heavy-ion collisions. Events with low spherocity, which are jetlike in nature, exhibit significantly narrower balance-function widths compared to isotropic events with high spherocity, illustrating that event-shape selection provides clear sensitivity to the underlying dynamics of particle production in pp collisions. The species dependence and event-shape sensitivity of the balance-function widths provide information about the hadronization dynamics and collectivity in small systems. These results demonstrate that multidimensional, particle-species-dependent balance-function measurements can disentangle the underlying mechanisms of charge correlations and mediumlike behavior in high-multiplicity pp collisions.

Italy

Subash Chandra Behera

Arvind Khuntia

System-size and event-shape dependence of particle-identified balance functions in proton-proton collisions at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn></mrow></math> TeV using PYTHIA 8 and EPOS models

The MAGNETO-<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>ν</mi></math> experiment searches for keV-scale heavy neutral leptons (HNLs) through precise measurements of the <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>β</mi><mo>−</mo></msup></math>-decay spectrum of <math xmlns="http://www.w3.org/1998/Math/MathML"><mmultiscripts><mi>Pu</mi><mprescripts></mprescripts><none></none><mn>241</mn></mmultiscripts></math>. We present spectra comprising a total of 194 million <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>β</mi><mo>−</mo></msup></math> decays recorded using decay energy spectrometry with metallic magnetic calorimeters, representing the most statistically precise measurement of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mmultiscripts><mi>Pu</mi><mprescripts></mprescripts><none></none><mn>241</mn></mmultiscripts><mspace width="0.16em"></mspace><msup><mi>β</mi><mo>−</mo></msup></mrow></math> decay to date. The <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>β</mi></math>-endpoint energy was determined using <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>γ</mi></math> rays and x-rays from an external <math xmlns="http://www.w3.org/1998/Math/MathML"><mmultiscripts><mi>Ba</mi><mprescripts></mprescripts><none></none><mn>133</mn></mmultiscripts></math> calibration source, yielding <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Q</mi><mi>β</mi></msub><mo>=</mo><mn>22.273</mn><mspace width="0.16em"></mspace><mrow><mo>(</mo><mn>33</mn><mo>)</mo></mrow><mspace width="0.28em"></mspace><mi>keV</mi></mrow></math>. The measured spectrum shows no statistically significant deviation from the allowed <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>β</mi></math>-decay model. From a subset of the high-statistics data, we set an upper limit on the mixing of an 11.5-keV HNL with the electron neutrino, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mrow><mo>|</mo></mrow><msub><mi>U</mi><mrow><mi>e</mi><mn>4</mn></mrow></msub><msup><mrow><mo>|</mo></mrow><mn>2</mn></msup><mo>&lt;</mo><mn>1.31</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math> at the 95% confidence level.

C. Lee

X. Zhang

A. Kavner

T. Parsons-Davis

D. Lee

N. Hines

S.T.P. Boyd

France

M. Loidl

X. Mougeot

M. Rodrigues

South Korea

M.K. Lee

J.W. Song

R. Wood

I. Jovanovic

G.B. Kim

Search for a heavy neutral lepton with the MAGNETO-<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>ν</mi></math> experiment using <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mmultiscripts><mi>Pu</mi><mprescripts></mprescripts><none></none><mn>241</mn></mmultiscripts><mspace width="0.16em"></mspace><msup><mi>β</mi><mo>−</mo></msup></mrow></math> decays

Jet interactions with the color-deconfined quantum chromodynamics medium in relativistic heavy-ion collisions are conventionally assessed by measuring the modification of the distributions of jet observables with respect to their baselines in proton-proton collisions. Deep learning methods enable per-jet evaluation of these modifications, enhancing the use of jets as precision probes of the nuclear medium. In this work, we predict the jet-by-jet fractional energy loss <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>χ</mi></math> for jets evolving through a quark-gluon plasma (QGP) medium using a linear Boltzmann transport model. To approximate realistic experimental conditions, we embed medium-modified jets in a thermal background and apply constituent subtraction for background removal. Two network architectures are studied: convolutional neural networks (CNNs) using jet images, and dynamic graph convolutional neural networks (DGCNNs) using particle clouds. We find that CNNs achieve accurate predictions for background-free jets but degrade in the presence of the QGP background and remain below the background-free baseline even after background subtraction. In contrast, DGCNNs applied to background-subtracted particle clouds maintain high accuracy across the entire <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>χ</mi></math> range, demonstrating the advantage of point-cloud–based graph neural networks that exploit full jet structure under realistic conditions.

Ran Li

Yi-Lun Du

Shanshan Cao

Deep learning for jet modification in the presence of the quark gluon plasma background

We investigate inclusive <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> production in proton-proton collisions at tens of GeV <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mi>s</mi></msqrt></math> energy, relevant for forthcoming measurements with the Spin Physics Detector (SPD) at NICA. Simulations are performed using the PEGASUS event generator with transverse-momentum-dependent (TMD) gluon densities, comparing the recent KMR-based <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi>KL</mi></mrow><mo>′</mo></msup><mn>2025</mn></mrow></math> and CCFM-based <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi>LLM</mi></mrow><mo>′</mo></msup><mn>2024</mn></mrow></math> parametrizations. Differential cross sections in rapidity and transverse momentum exhibit smooth, stable behavior under renormalization-scale variation. Normalized <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>p</mi><mi>T</mi></msub></math> spectra reveal distinct hardening patterns linked to the underlying gluon <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>k</mi><mi>T</mi></msub></math> broadening in each model. The relative contributions of color-singlet and color-octet channels are also quantified, demonstrating the dominance of color-octet mechanisms in the SPD energy regime. These results provide the first detailed assessment of quarkonium production sensitivity to gluon TMDs near threshold, offering timely theoretical guidance for upcoming <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> measurements at SPD/NICA.

Russia

Shubham Sharma

JINR

Kazakhstan

Alexey Aparin

<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> production in proton-proton collisions at Spin Physics Detector energies of the JINR Nuclotron-based Ion Collider fAcility

We perform a high-statistics lattice QCD calculation of the low-energy two-nucleon scattering amplitudes. To address discrepancies in the literature, the calculation is performed at a heavy pion mass in the limit that the light quark masses are equal to the physical strange quark mass, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>m</mi><mi>π</mi></msub><mo>=</mo><msub><mi>m</mi><mi>K</mi></msub><mo>≃</mo><mn>714</mn><mspace width="0.28em"></mspace><mi>MeV</mi></mrow></math>. Using a state-of-the-art momentum space method, we rule out the presence of a bound di-nucleon in both the isospin 0 (deuteron) and 1 (di-neutron) channels, in contrast with many previous results that made use of compact hexaquark creation operators. To diagnose the discrepancy, we add such hexaquark interpolating operators to our basis and find that they do not affect the determination of the two-nucleon finite-volume spectrum, and thus they do not couple to deeply bound di-nucleons that are missed by the momentum-space operators. Furthermore, we perform a high-statistics calculation of the HAL QCD potential on the same gauge ensembles and find qualitative agreement with our main results. We conclude that di-nucleons do not form bound states at heavy pion masses and that previous identification of deeply bound di-nucleons must have arisen from a misidentification of the spectrum from off-diagonal elements of a correlation function.

John Bulava

M.A. Clark

Arjun S. Gambhir

Andrew D. Hanlon

Ben Hörz

Bálint Joó

Christopher Körber

Ken McElvain

Aaron S. Meyer

Henry Monge-Camacho

Colin Morningstar

Joseph Moscoso

Amy Nicholson

Switzerland

Fernando Romero-López

Ermal Rrapaj

Andrea Shindler

Sarah Skinner

Pavlos M. Vranas

André Walker-Loud

Di-nucleons do not form bound states at heavy pion mass

Ultrarelativistic collisions of heavy ions provide a rich spectrum of possibilities to discuss the response of the nucleus to photons. Newly published neutron and proton multiplicities measured in the ALICE experiment in ultraperipheral collisions allow us to investigate the influence of the electromagnetic fields on colliding nuclei for the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mmultiscripts><mi>Pb</mi><mprescripts></mprescripts><none></none><mn>208</mn></mmultiscripts><mo>+</mo><mmultiscripts><mi>Pb</mi><mprescripts></mprescripts><none></none><mn>208</mn></mmultiscripts></mrow></math> at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>5.02</mn></mrow></math> TeV. The theoretical predictions are done within a hybrid model including equivalent photon approximations, GiBUU modeling of preequilibrium processes, and generation of the excited nuclear remnants, where decay is modeled by a statistical approach: GEM2 or <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mtext>GEMINI</mtext><mo>+</mo><mo>+</mo></mrow></math>. The cross sections of the mass-charge distributions of nuclear remnants as well as the neutron, proton, and other charged particle multiplicities are estimated. We concentrate on production of protons and isotopes coming from the electromagnetic dissociation. Special attention is devoted to emission of a single proton. It is explained in the paper that cross section for <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>1</mn><mi>p</mi></mrow></math> emission is very close to maximal available one based on reactions of photon with individual nucleons (protons or neutrons) inside the nucleus.

Poland

P. Jucha

K. Mazurek

A. Szczurek

K. Pysz

Impact of new results from ultraperipheral collisions on modeling the proton and neutron emission in photon-induced nuclear processes