Thu·Oct 12, 2023Thursday·October 12, 2023

1. 01*

   Exploring medium properties with hard transverse momentum splittings using groomed jet substructure measurements in Pb--Pb collisions with ALICE

   Raymond Ehlers (for the ALICE Collaboration)🇺🇸

   Jet substructure observables provide unique probes of the properties of the Quark-Gluon Plasma (QGP). In these proceedings we report new measurements of groomed jet substructure in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. We present the first application of dynamical grooming in heavy-ion collisions to search for excess $k_{\mathrm{T},\mathrm{g}}$ emissions, which is a signature of large-angle scattering of jets off quasi-particles in the QGP. We present additional measurements employing both the soft drop and dynamical grooming algorithms in 0-10% central Pb-Pb, 30-50% semicentral Pb-Pb, and proton-proton (pp) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. Results from the various grooming methods and parameters are compared. Comparisons to model calculations are also presented. The techniques developed for this measurement are more broadly applicable to jet substructure, which we likewise discussed.

   nucl-exPoS(2024)·4 citations
2. 02*

   Isospin symmetry in the $T=1,A=62$ triplet

   K. Wimmer🇯🇵 · P. Ruotsalainen🇫🇮 · S.M. Lenzi🇮🇹 · A. Poves🇪🇸 · T. Hüyük🇪🇸 · F. Browne🇯🇵 · P. Doornenbal🇯🇵 · T. Koiwai🇯🇵 · T. Arici🇩🇪 · K. Auranen🇫🇮 · M.A. Bentley🇬🇧 · M. L. Cortés🇮🇹 and 35 other authors

   Excited states in the $T_z=0,-1$ nuclei ${}^{62}$Ga and ${}^{62}$Ge were populated in direct reactions of relativistic radioactive ion beams at the RIBF. Coincident \grays were measured with the DALI2${}^{+}$ array and uniquely assigned to the $A=62$ isobars. In addition, ${}^{62}$Ge was also studied independently at JYFL-ACCLAB using the ${}^{24}$Mg(${}^{40}$Ca,$2n$)${}^{62}$Ge fusion-evaporation reaction. The first excited $T=1,J^{\pi }=2^{+}$ states in ${}^{62}$Ga and ${}^{62}$Ge were identified at $979(1)$ and $965(1)$~keV, respectively, resolving discrepant interpretations in the literature. States beyond the first $2^{+}$ state in ${}^{62}$Ge were also identified for the first time in the present work. The results are compared with shell-model calculations in the $fp$ model space. Mirror and triplet energy differences are analyzed in terms of individual charge-symmetry and charge-independence breaking contributions. The MED results confirm the shrinkage of the $p$-orbits' radii when they are occupied by at least one nucleon on average.

   nucl-exPLB(2023)·12 citations
3. 03*

   Charged-particle production as a function of the relative transverse activity classifier in pp, p$-$Pb, and Pb$-$Pb collisions at the LHC

   ALICE Collaboration

   Measurements of charged-particle production in pp, p$-$Pb, and Pb$-$Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum ($p_{\mathrm{T}}^{\mathrm{trig}}$) in the range $8<p_{\mathrm{T}}^{\mathrm{trig}}<15$ GeV$/c$. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier, $R_{\mathrm{T}}=N_{\mathrm{ch}}^{\mathrm{T}}/⟨N_{\mathrm{ch}}^{\mathrm{T}}⟩$, is used to group events according to their UE activity, where $N_{\mathrm{ch}}^{\mathrm{T}}$ is the charged-particle multiplicity per event in the transverse region and $⟨N_{\mathrm{ch}}^{\mathrm{T}}⟩$ is the mean value over the whole analysed sample. The energy dependence of the $R_{\mathrm{T}}$ distributions in pp collisions at $\sqrt{s}=2.76$, 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle $p_{\mathrm{T}}$ spectra as a function of $R_{\mathrm{T}}$ in the three azimuthal regions in pp, p$-$Pb, and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and p$-$Pb).

   nucl-exhep-exJHEP(2024)·16 citations
4. 04*

   Femtoscopic correlations of identical charged pions and kaons in pp collisions at $\sqrt{s}=13$ TeV with event-shape selection

   ALICE Collaboration

   Collective behavior has been observed in high-energy heavy-ion collisions for several decades. Collectivity is driven by the high particle multiplicities that are produced in these collisions. At the CERN Large Hadron Collider (LHC), features of collectivity have also been seen in high-multiplicity proton-proton collisions that can attain particle multiplicities comparable to peripheral Pb-Pb collisions. One of the possible signatures of collective behavior is the decrease of femtoscopic radii extracted from pion and kaon pairs emitted from high-multiplicity collisions with increasing pair transverse momentum. This decrease can be described in terms of an approximate transverse mass scaling. In the present work, femtoscopic analyses are carried out by the ALICE Collaboration on charged pion and kaon pairs produced in pp collisions at $\sqrt{s}=13$ TeV from the LHC to study possible collectivity in pp collisions. The event-shape analysis method based on transverse sphericity is used to select for spherical versus jet-like events, and the effects of this selection on the femtoscopic radii for both charged pion and kaon pairs are studied. This is the first time this selection method has been applied to charged kaon pairs. An approximate transverse-mass scaling of the radii is found in all multiplicity ranges studied when the difference in the Lorentz boost for pions and kaons is taken into account. This observation does not support the hypothesis of collective expansion of hot and dense matter that should only occur in high-multiplicity events. A possible alternate explanation of the present results is based on a scenario of common emission conditions for pions and kaons in pp collisions for the multiplicity ranges studied.

   nucl-exhep-exPRC(2024)·11 citations
5. 05*

   Dynamically generated states from the $\eta K^{\ast }{\bar{K}}^{\ast }$, $\pi K^{\ast }{\bar{K}}^{\ast }$, and $K{K}^{\ast }{\bar{K}}^{\ast }$ systems within the fixed-center approximation

   Qing-Hua Shen🇨🇳 · Xu Zhang🇨🇳 · Xiang Liu🇨🇳 · Ju-Jun Xie🇨🇳

   The three-body systems $\eta K^{\ast }{\bar{K}}^{\ast }$, $\pi K^{\ast }{\bar{K}}^{\ast }$, and $K{K}^{\ast }{\bar{K}}^{\ast }$ are further investigated within the framework of fixed-center approximation, where $K^{\ast }{\bar{K}}^{\ast }$ is treated as the fixed-center, corresponding to the possible scalar meson $a_0(1780)$ or the tensor meson $f_2^{\prime }(1525)$. The interactions between $\eta$, $\pi$, $K$, and $K^{\ast }$ are taken from the chiral unitary approach. The resonance structures appear in the modulus squared of the three-body scattering amplitude and suggest that $\eta /\pi /K$-$(K^{\ast }{\bar{K}}^{\ast }{)}_{a_0(1780)/f_2^{\prime }(1525)}$ hadron state can be formed. By scattering the $\eta$ meson on the fixed-center $(K^{\ast }{\bar{K}}^{\ast }{)}_{a_0(1780)}$, it is found that there is a distinct peak around 2100 MeV, as shown in the modulus squared of the three-body scattering amplitude, which can be associated with the meson $\pi (2070)$. For the scattering of the $\eta$ meson on the $(K^{\ast }{\bar{K}}^{\ast }{)}_{f_2^{\prime }(1525)}$, a resonance structure around 1890 MeV is found and it can be associated with the ${\eta }_2(1870)$ meson. Other resonance structures are also found and can be associated with ${\pi }_2(1880)$ and $\eta (2010)$.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2024)·2 citations
6. 06*

   Multi-particle Integral and Differential Correlation Functions

   Claude Pruneau🇺🇸 · Victor Gonzalez🇺🇸 · Ana Marin🇩🇪 · Sumit Basu🇸🇪

   This paper formalizes the use of integral and differential cumulants for measurements of multi-particle event-by-event transverse momentum fluctuations, rapidity fluctuations, as well as net charge fluctuations. This enables the introduction of multi-particle balance functions, defined based on differential correlation functions (factorial cumulants), that suppress two and three prong resonance decays effects and enable measurements of underlying long range correlations obeying quantum number conservation constraints. These multi-particle balance functions satisfy simple sum rules determined by quantum number conservation. It is additionally shown that these multi-particle balance functions arise as an intrinsic component of high-order net charge cumulants. This implies that the magnitude of these cumulants, measured in a specific experimental acceptance, is strictly constrained by charge conservation and primarily determined by the rapidity and momentum width of these balance functions. The paper also presents techniques to reduce the computation time of differential correlation functions up to order $n=$10 based on the methods of moments.

   ↳ hep-exnucl-exPRC(2024)·6 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.