Fri·Nov 15, 2024Friday·November 15, 2024

1. 01*

   Probing the QCD Critical End Point with Finite-Size Scaling of Net-Baryon Cumulant Ratios

   Roy A. Lacey (Department of Chemistry, Stony Brook University, Stony Brook, NY, USA)🇺🇸

   Finite-size scaling (FSS) is applied to net-baryon cumulant ratios $C_2/C_1$, $C_3/C_2$, $C_4/C_2$, $C_3/C_1$, and $C_4/C_1$ measured in Au+Au collisions over the Beam Energy Scan Phase~I range $\sqrt{s_{NN}}=7.7$--$200$~GeV to constrain the location and universality class of the QCD critical end point (CEP). Although finite-size and finite-time effects suppress non-monotonic signatures in unscaled data, the FSS analysis reveals a collapse of measurements from different beam energies and centralities onto universal scaling functions. All cumulant ratios collapse under a single, common set of critical exponents and exhibit divergence patterns characteristic o 3D Ising critical behavior. The scaling results indicate a CEP at ${\sqrt{s}}_{\mathrm{CEP}}\approx 33.0$~GeV, corresponding to ${\mu }_{B,\mathrm{CEP}}\approx 130$~MeV and $T_{\mathrm{CEP}}\approx 158.5$~MeV. These findings demonstrate that finite-size scaling provides a robust, model-independent framework for accessing critical behavior in finite, dynamically evolving systems, where non-equilibrium baryon-number transport can enhance the experimental visibility of susceptibility-driven fluctuations without modifying the underlying universality class.

   nucl-exhep-exhep-thnucl-th2 citations
2. 02*

   Observation of partonic flow in proton-proton and proton-nucleus collisions

   ALICE Collaboration

   Quantum Chromodynamics predicts a phase transition from ordinary hadronic matter to the quark-gluon plasma (QGP) at high temperatures and energy densities, where quarks and gluons (partons) are not confined within hadrons. The QGP is generated in ultrarelativistic heavy-ion collisions. Anisotropic flow coefficients, quantifying the anisotropic azimuthal expansion of the produced matter, provide a unique tool to unravel QGP properties. Flow measurements in high-energy heavy-ion collisions show a distinctive grouping of anisotropic flow for baryons and mesons at intermediate transverse momentum, a feature associated with flow being imparted at the quark level, confirming the existence of the QGP. The observation of QGP-like features in relativistic proton-proton and proton-ion collisions has sparked debate about possible QGP formation in smaller collision systems, which remains unresolved. In this article, we demonstrate for the first time the distinctive grouping of anisotropic flow for baryons and mesons in high-multiplicity proton-lead and proton-proton collisions at the Large Hadron Collider (LHC). These results are described by a model that includes hydrodynamic flow followed by hadron formation via quark coalescence, replicating features observed in heavy-ion collisions. This observation is consistent with the formation of a partonic flowing system in proton-proton and proton-lead collisions at the LHC.

   nucl-exhep-exnucl-thNature Commun.(2026)·32 citations
3. 03*

   System size and energy dependence of the mean transverse momentum fluctuations at the LHC

   ALICE Collaboration

   Event-by-event fluctuations of the event-wise mean transverse momentum, $⟨p_{\mathrm{T}}⟩$, of charged particles produced in proton$-$proton (pp) collisions at $\sqrt{s}$ = 5.02 TeV, Xe$-$Xe collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.44 TeV, and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.0 TeV are studied using the ALICE detector based on the integral correlator $⟨⟨\Delta p_{\mathrm{T}}\Delta p_{\mathrm{T}}⟩⟩$. The correlator strength is found to decrease monotonically with increasing produced charged-particle multiplicity measured at midrapidity in all three systems. In Xe$-$Xe and Pb$-$Pb collisions, the multiplicity dependence of the correlator deviates significantly from a simple power-law scaling as well as from the predictions of the HIJING and AMPT models. The observed deviation from power-law scaling is expected from transverse radial flow in semicentral to central Xe$-$Xe and Pb$-$Pb collisions. In pp collisions, the correlation strength is also studied by classifying the events based on the transverse spherocity, $S_0$, of the particle production at midrapidity, used as a proxy for the presence of a pronounced back-to-back jet topology. Low-spherocity (jetty) events feature a larger correlation strength than those with high spherocity (isotropic). The strength and multiplicity dependence of jetty and isotropic events are well reproduced by calculations with the PYTHIA 8 and EPOS LHC models.

   nucl-exhep-exEPJC(2025)·13 citations
4. 04*

   Mirror nucleon-transfer reactions from ${}^{18}$Ne and ${}^{18}$O

   F. Flavigny🇫🇷 · N. Keeley🇵🇱 · A. Gillibert🇫🇷 · V. Lapoux🇫🇷 · A. Lemasson🇫🇷 · L. Audirac🇫🇷 · B. Bastin🇫🇷 · S. Boissinot🇫🇷 · J. Caccitti🇫🇷 · A. Corsi🇫🇷 · S. Damoy🇫🇷 · S. Franchoo🇫🇷 and 17 other authors

   The ${}^{18}$Ne(d,t)${}^{17}$Ne and ${}^{18}$Ne(d,${}^3$He)${}^{17}$F single-nucleon pickup reactions were measured at 16.5 MeV/nucleon in inverse kinematics together with elastic and inelastic scattering channels. The full set of measured exclusive differential cross sections was compared with the mirror reaction channels on stable ${}^{18}$O after consistent reanalysis using coupled reaction channels calculations. Within this interpretation scheme, most of the spectroscopic factors extracted for the population of unbound states in ${}^{17}$F match within uncertainties with their mirror partners in ${}^{17}$O. However, for the deeply-bound neutron removal channel to ${}^{17}$Ne, a significant symmetry breaking with the mirror proton-removal channel leading to ${}^{17}$N is evidenced by an overall single-particle strength reduction.

   nucl-exPRC(2024)·0 citations
5. 05*

   Measurement of $\varphi (1020)$ meson production in fixed-target $\text{p}$Ne collisions at $\sqrt{s_{NN}}$ = 68.5 GeV

   LHCb collaboration: R. Aaij🇳🇱 · A.S.W. Abdelmotteleb🇬🇧 · C. Abellan Beteta🇨🇭 · F. Abudinén🇬🇧 · T. Ackernley🇬🇧 · A. A. Adefisoye🇺🇸 · B. Adeva🇪🇸 · M. Adinolfi🇬🇧 · P. Adlarson🇸🇪 · C. Agapopoulou🇫🇷 · C.A. Aidala🇺🇸 · Z. Ajaltouni🇫🇷 and 1139 other authors

   The first measurement of $\varphi (1020)$ meson production in fixed-target $p$Ne collisions at $\sqrt{s_{NN}}=68.5$ GeV is presented. The $\varphi (1020)$ mesons are reconstructed in their $K^{+}{K}^{-}$ decay in a data sample consisting of proton collisions on neon nuclei at rest, corresponding to an integrated luminosity of $21.7\pm 1.4$ nb${}^{-1}$, collected by the LHCb detector at CERN. The $\varphi (1020)$ production cross-section in the centre-of-mass rapidity range of $-1.8<y^{\ast }<0$ and transverse momentum range of $800<p_T<6500$ MeV/c is found to be $\sigma =182.7\pm 2.7\text{(stat.)}\pm 14.1\text{(syst)}\mu$b/nucleon. A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the $\varphi (1020)$ meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.

   ↳ hep-exnucl-exJHEP(2025)·8 citations
6. 06*

   Measurement of $\omega$ meson production in pp collisions at $\sqrt{s}$ = 13 TeV

   ALICE Collaboration

   The $p_{\mathrm{T}}$-differential cross section of $\omega$ meson production in pp collisions at $\sqrt{s}=13$ TeV at midrapidity ($|y|<0.5$) was measured with the ALICE detector at the LHC, covering an unprecedented transverse-momentum range of $1.6<p_{\mathrm{T}}<50$ GeV/$c$. The meson is reconstructed via the $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay channel. The results are compared with various theoretical calculations: PYTHIA8.2 with the Monash 2013 tune overestimates the data by up to 50%, whereas good agreement is observed with Next-to-Leading Order (NLO) calculations incorporating $\omega$ fragmentation using a broken SU(3) model. The $\omega /{\pi }^0$ ratio is presented and compared with theoretical calculations and the available measurements at lower collision energies. The presented data triples the $p_{\mathrm{T}}$ ranges of previously available measurements. A constant ratio of $C^{\omega /{\pi }^0}=0.578\pm 0.006\text{(stat.)}\pm 0.013\text{(syst.)}$ is found above a transverse momentum of $4$ GeV/$c$, which is in agreement with previous findings at lower collision energies within the systematic and statistical uncertainties.

   ↳ hep-exnucl-exJHEP(2025)·2 citations
7. 07*

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

   ALICE Collaboration

   The momentum-differential invariant cross sections of ${\pi }^0$ and $\eta$ 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 $0.2<p_{\mathrm{T}}<200$ GeV/$c$ and $0.4<p_{\mathrm{T}}<60$ GeV/$c$ for the ${\pi }^0$ and $\eta$, respectively, extending the $p_{\mathrm{T}}$ 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 $x$ ($x_{\mathrm{T}}$) scaling of the ${\pi }^0$ cross sections at LHC energies is fulfilled with a power-law exponent of $n=5.01\pm 0.05$, 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 ${\pi }^0$ 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 ${\pi }^0$ and are not able to describe the shape and magnitude of the $\eta$ spectrum. The charged-particle multiplicity dependent ${\pi }^0$ and $\eta$ $p_{\mathrm{T}}$ 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 $\eta /{\pi }^0$ ratio depends on the charged-particle multiplicity for $p_{\mathrm{T}}<4$ GeV/$c$. PYTHIA8 and EPOS LHC qualitatively explain this behavior with an increasing contribution from the feed-down of heavier particles to the ${\pi }^0$ spectrum.

   ↳ hep-exnucl-exJHEP(2025)·12 citations
8. 08*

   The lowest-radiation environments in the Solar System: new opportunities for underground rare-event searches

   Xilin Zhang🇺🇸 · Jason Detwiler🇺🇸 · Clint Wiseman🇺🇸

   We study neutrino, muon, and gamma-ray fluxes in extraterrestrial environments in our Solar System via semi-analytical estimates and Monte Carlo simulations. In sites with negligible atmosphere, we find a strong reduction in the cosmic-ray-induced neutrino and muon fluxes relative to their intensities on Earth. Neutrinos with energies between 50 MeV and 100 TeV show particularly strong suppression, by as much as 10${}^3$, even at shallow depths. The solar neutrino suppression increases as the square of the site's distance from the Sun. Natural radiation due to nuclear decay is also expected to be lower in many of these locations and may be reduced to effectively negligible levels in the liquid water environments. The sites satisfying these characteristics represent an opportunity for greatly extending the physics reach of underground searches in fundamental physics, such as searches for WIMP Dark Matter, neutrinoless double-beta decay, the diffuse supernova neutrinos, and neutrinos from nearby supernova. As a potential near-term target, we propose a measurement of muon and gamma-ray fluxes in an accessible underground lunar site such as the Mare Tranquillitatis Pit to perform a first measurement of the prompt component in cosmic-ray-induced particle production, and to constrain lunar evolution models.

   ↳ hep-exastro-ph.EPhep-phnucl-ex+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.