Thu·Aug 10, 2023Thursday·August 10, 2023

1. 01*

   STAR Experimental Highlights at Hard Probes 2023

   Nihar Ranjan Sahoo (for the STAR Collaboration)🇨🇳

   We highlight the STAR experiment's hard probes results, including jets and heavy flavor production in heavy-ion collisions to study the properties of the quark-gluon plasma. Various jet-substructure observables in proton-proton collisions are presented to explore both perturbative and non-perturbative regimes of quantum chromodynamics. Finally, we discuss the STAR experiment's hard probes physics program for ongoing data taking.

   nucl-exhep-exhep-phnucl-thPoS(2024)·2 citations
2. 02*

   Simulation of the 2E Technique on neutron multiplicity measurement as a function of fragment mass in spontaneous fission of 252Cf

   Modesto Montoya

   A Monte Carlo simulation algorithm to investigate the measurement of the average prompt neutron multiplicity as a function of pre-neutron mass, for fragments from the spontaneous fission of 252Cf is presented. The input data consist of experimental measurements of the kinetic energy and mass distributions obtained by Gook et al. and the values calculated using the FIFRELIN model by Piau et al. We analyze the output curve obtained by simulation of the 2E technique, which should ideally match the theoretical curve. However, we find that the simulated as experiential curve exhibits a maximum value at A=122, close to mass symmetry, while the pre-neutron curve has a maximum at A=118. Additionally, we observe that que the simulated as pre neutron values are higher than the theoretical values for A<90 and A>162, respectively. We attribute this discrepancy to inaccuracies in the relationship between provisional mass and the pre-neutron mass used in the 2E technique for data processing in each fission event.

   ↳ nucl-thnucl-exRev.Mex.Fis.(2024)·0 citations
3. 03*

   UPCs as probes of partonic structure -- exclusive and inclusive processes

   V. Guzey (Jyvaskyla U. and Helsinki U.)🇫🇮

   Ultraperipheral collisions (UPCs) at the LHC and RHIC provide important new information on the partonic structure of the proton and nuclei and small-$x$ dynamics in QCD. We review phenomenological applications of the collinear factorization at leading and next-to-leading orders of perturbative QCD and the dipole model to coherent and incoherent $J/\psi$ photoproduction in Pb-Pb UPCs at the LHC emphasizing the strong leading twist gluon nuclear shadowing, the role of quark-antiquark-gluon dipoles, and a possible onset the gluon saturation in nuclei. We also discuss inclusive and diffractive dijet photoproduction in UPCs, which give complementary constraints on nuclear parton distributions and the pattern of factorization breaking in diffraction.

   ↳ hep-phhep-exnucl-exPoS(2024)·1 citation
4. 04*

   Meson cloud contributions to the Dalitz decays of decuplet to octet baryons

   G. Ramalho🇰🇷 · K. Tsushima🇧🇷

   We study the role of the meson cloud on the electromagnetic transitions from decuplet ($B^{\prime }$) to octet ($B$) baryons in terms of the squared four-momentum transfer $q^2$. In the quark model framework, the meson cloud dressing of the quark cores gives important contributions to the ${\gamma }^{\ast }N\to \Delta (1232)$ transition form factors. In the present work, we estimate the meson cloud contributions of all decuplet to octet baryon transitions (${\gamma }^{\ast }B\to B^{\prime }$ or $B^{\prime }\to {\gamma }^{\ast }B$). Models that combine valence quark effects with pion and kaon cloud dressing provide a fair description of the radiative decays of decuplet to octet baryons, namely the ${\Sigma }^0(1385)\to \gamma \Lambda (1116)$ and ${\Sigma }^{+}(1385)\to \gamma {\Sigma }^{+}(1193)$ decays. Previous studies indicated the relevance of the pion cloud effects on the $B^{\prime }\to {\gamma }^{\ast }B$ transition, but also suggested that the kaon cloud contributions may be important in the timelike region. We combine then the contributions of the bare core, estimated by a covariant quark model, with $q^2$-dependent contributions of pion and kaon clouds. We use the framework to calculate the Dalitz decay rates and the Dalitz decay widths of decuplet baryons in octet baryons with di-electrons ($B^{\prime }\to e^{+}{e}^{-}B$) or di-muons ($B^{\prime }\to {\mu }^{+}{\mu }^{-}B$). We conclude, based on the magnitude of our results, that most estimates of the $B^{\prime }\to e^{+}{e}^{-}B$ Dalitz decay widths may be tested at HADES and PANDA (GSI) in a near future. We discuss also the possibility of measuring the $\Delta (1232)\to {\mu }^{+}{\mu }^{-}N$ and ${\Sigma }^0(1385)\to {\mu }^{+}{\mu }^{-}\Lambda (1116)$ decay widths in some facilities, based on the estimated branching ratios.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2023)·9 citations
5. 05*

   Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at $\sqrt{s}=13$ TeV

   ALICE Collaboration

   The production cross sections of ${\mathrm{D}}^0$ and ${\Lambda }_{\mathrm{c}}^{+}$ hadrons originating from beauty-hadron decays (i.e. non-prompt) were measured for the first time at midrapidity ($|y|<0.5$) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy $\sqrt{s}=13$ TeV. They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The $\mathrm{b}\overline{\mathrm{b}}$ production cross section per unit of rapidity at midrapidity, estimated from these measurements, is $\mathrm{d}{\sigma }_{\mathrm{b}\overline{\mathrm{b}}}/\mathrm{d}y{|}_{|y|<0.5}=83.1\pm 3.5(stat.)\pm 5.4(syst.{)}_{-3.2}^{+12.3}(extrap.)\mu$b. The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The non-prompt ${\Lambda }_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the p$/{\pi }^{+}$ and $\Lambda /{\mathrm{K}}_{\mathrm{S}}^0$ ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The $p_{\mathrm{T}}$-integrated non-prompt ${\Lambda }_{\mathrm{c}}/{\mathrm{D}}^0$ ratio is found to be significantly higher than the one measured in e${}^{+}$e${}^{-}$ collisions.

   ↳ hep-exnucl-exPRD(2023)·33 citations
6. 06*

   Charm production and fragmentation fractions at midrapidity in pp collisions at $\sqrt{s}=13$ TeV

   ALICE Collaboration

   Measurements of the production cross sections of prompt ${\mathrm{D}}^0$, ${\mathrm{D}}^{+}$, ${\mathrm{D}}^{\ast +}$, ${\mathrm{D}}_{\mathrm{s}}^{+}$, ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$, and ${\mathrm{\Xi }}_{\mathrm{c}}^{+}$ charm hadrons at midrapidity in proton$-$proton collisions at $\sqrt{s}=13$ TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum ($p_{\mathrm{T}}$) are provided with improved precision and granularity. The ratios of $p_{\mathrm{T}}$-differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken-$x$ ($10^{-5}-10^{-4}$). The measurements of ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ (${\mathrm{\Xi }}_{\mathrm{c}}^{+}$) baryon production extend the measured $p_{\mathrm{T}}$ intervals down to $p_{\mathrm{T}}=0(3)$~GeV$/c$. These measurements are used to determine the charm-quark fragmentation fractions and the $\mathrm{c}\overline{\mathrm{c}}$ production cross section at midrapidity ($|y|<0.5$) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons ${\mathrm{D}}^0$, ${\mathrm{D}}^{+}$, ${\mathrm{D}}_{\mathrm{s}}^{+}$, ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$, ${\mathrm{\Xi }}_{\mathrm{c}}^0$ and, for the first time, ${\mathrm{\Xi }}_{\mathrm{c}}^{+}$, and of the strongly-decaying J/$psi$ mesons. The first measurements of ${\mathrm{\Xi }}_{\mathrm{c}}^{+}$ and ${\mathrm{\Sigma }}_{\mathrm{c}}^{0,++}$ fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to e${}^{+}$e${}^{-}$ and ep collisions. The $\mathrm{c}\overline{\mathrm{c}}$ production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations.

   ↳ hep-exnucl-exJHEP(2023)·78 citations
7. 07*

   Search for a Non-Relativistic Boson in Two-Body Antimuon Decay

   J. I. Collar🇺🇸 · P. S. Cooper🇺🇸 · C. M. Lewis🇺🇸

   We demonstrate the feasibility of probing the charged lepton flavor violating decay ${\mu }^{+}\to e^{+}{X}^0$ for the presence of a slow-moving neutral boson $X^0$ capable of undergoing gravitational binding to large structures, and as such able to participate in some cosmological scenarios. A short exposure to surface antimuons from beamline M20 at TRIUMF generates a branching ratio limit of $\lesssim 10^{-5}$. This is comparable or better than previous searches for this channel, although in a thus-far unexplored region of $X^0$ phase space very close to the kinematic limit of the decay. The future improved sensitivity of the method using a customized p-type point contact germanium detector is described.

   ↳ hep-phastro-ph.GAhep-exnucl-exPRL(2023)·0 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.