Wed·May 31, 2023Wednesday·May 31, 2023

1. 01*

   Energy dependence of coherent photonuclear production of J/$\psi$ mesons in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$=5.02 TeV

   ALICE Collaboration

   The cross section for coherent photonuclear production of J/$\psi$ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. Cross sections are presented in five different J/$\psi$ rapidity ranges within $|y|<4$, with the J/$\psi$ reconstructed via its dilepton decay channels. In some events the J/$\psi$ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range $17<W_{\gamma \mathrm{Pb},\mathrm{n}}<920$ GeV, where $W_{\gamma \mathrm{Pb},\mathrm{n}}$ is the centre-of-mass energy per nucleon of the $\gamma \mathrm{Pb}$ system. This range corresponds to a Bjorken-$x$ interval spanning about three orders of magnitude: $1.1\times 10^{-5}<x<3.3\times 10^{-2}$. In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies.

   nucl-exhep-exJHEP(2023)·95 citations
2. 02*

   Accessing the strong interaction between $\Lambda$ baryons and charged kaons with the femtoscopy technique at the LHC

   ALICE Collaboration

   The interaction between $\Lambda$ baryons and kaons/antikaons is a crucial ingredient for the strangeness $S=0$ and $S=-2$ sector of the meson$-$baryon interaction at low energies. In particular, the $\Lambda \overline{\mathrm{K}}$ might help in understanding the origin of states such as the $\Xi (1620)$, whose nature and properties are still under debate. Experimental data on $\Lambda$$-$$\mathrm{K}$ and $\Lambda$$-$$\overline{\mathrm{K}}$ systems are scarce, leading to large uncertainties and tension between the available theoretical predictions constrained by such data. In this Letter we present the measurements of $\Lambda$$-$K${}^{+}\oplus \overline{\Lambda }$$-$K${}^{-}$ and $\Lambda$$-$K${}^{-}\oplus \overline{\Lambda }$$-$K${}^{+}$ correlations obtained in the high-multiplicity triggered data sample in pp collisions at $\sqrt{s}=13$ TeV recorded by ALICE at the LHC. The correlation function for both pairs is modeled using the Lednicky$-$Lyuboshits analytical formula and the corresponding scattering parameters are extracted. The $\Lambda$$-$K${}^{-}\oplus \overline{\Lambda }$$-$K${}^{+}$ correlations show the presence of several structures at relative momenta $k^{\ast }$ above 200 MeV/$c$, compatible with the $\Omega$ baryon, the $\Xi (1690)$, and $\Xi (1820)$ resonances decaying into $\Lambda$$-$K${}^{-}$ pairs. The low $k^{\ast }$ region in the $\Lambda$$-$K${}^{-}\oplus \overline{\Lambda }$$-$K${}^{+}$ also exhibits the presence of the $\Xi (1620)$ state, expected to strongly couple to the measured pair. The presented data allow to access the $\Lambda$K${}^{+}$ and $\Lambda$K${}^{-}$ strong interaction with an unprecedented precision and deliver the first experimental observation of the $\Xi (1620)$ decaying into $\Lambda$K${}^{-}$.

   nucl-exhep-exPLB(2023)·47 citations
3. 03*

   Forward-backward correlations with the $\Sigma$ quantity in the wounded constituent framework at LHC energies

   Iwona Anna Sputowska🇵🇱

   $\Sigma$ is a new correlation measure, quite recently introduced to heavy-ion physics. This measure, defined in the independent source model as a strongly intensive quantity, is expected to be free of the effects of system volume and volume fluctuations. This paper discusses the forward-backward correlation quantified with the $\Sigma$ observable calculated in the framework of the wounded nucleon model (WNM) and wounded quark model (WQM). Findings show that the wounded constituent approach outperforms the commonly used heavy-ion Monte Carlo generators, such as HIJING, AMPT or EPOS, by accurately describing the experimental data on FB correlations with $\Sigma$ measured by ALICE in Xe--Xe reactions at $\sqrt{s_{\mathrm{NN}}}$=5.44 TeV and in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 2.76 and 5.02 TeV. This paper demonstrates that $\Sigma$ can be a unique tool for determining the fragmentation function of a wounded constituent in a symmetric nucleus-nucleus collision. However, in the wounded constituent framework, it is no longer a strongly intensive quantity.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2023)·3 citations
4. 04*

   Mean range bunching of exotic nuclei produced by in-flight fragmentation and fission -- Stopped-beam experiments with increased efficiency

   Timo Dickel · Christine Hornung · Daler Amanbayev · Samuel Ayet San Andres · Soenke Beck · Julian Bergmann · Hans Geissel · Juergen Gerl · Magdalena Gorska · Lizzy Groef · Emma Haettner · Jan-Paul Hucka and 15 other authors

   The novel technique of mean range bunching has been developed and applied at the projectile fragment separator FRS at GSI in four experiments of the FAIR phase-0 experimental program. Using a variable degrader system at the final focal plane of the FRS, the ranges of the different nuclides can be aligned, allowing to efficiently implant a large number of different nuclides simultaneously in a gas-filled stopping cell or an implantation detector. Stopping and studying a cocktail beam overcomes the present limitations of stopped-beam experiments. The conceptual idea of mean range bunching is described and illustrated using simulations. In a single setting of the FRS, 37 different nuclides were stopped in the cryogenic stopping cell and were measured in a single setting broadband mass measurement with the multiple-reflection time-of-flight mass spectrometer of the FRS Ion Catcher.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.B(2023)·5 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.