Wed·Nov 23, 2022Wednesday·November 23, 2022

1. 01*

   Exploring jet interactions in the quark-gluon plasma using jet substructure measurements in Pb-Pb collisions with ALICE

   Raymond Ehlers (for the ALICE Collaboration)🇺🇸

   Jets are generated in hard interactions in high-energy nuclear collisions. Jets propagate through the quark-gluon plasma (QGP) as the jet shower evolves; their interaction with the QGP, known as jet quenching, generates observable phenomena that provide incisive probes of the structure and dynamics of the QGP. For instance, medium-induced modification of jet substructure probes color coherence, and may be sensitive to differences in quark and gluon energy loss due to their different Casimir factors. Jet grooming can be used to focus on specific regions of phase space, isolating medium-induced effects on hard splittings in the jet shower. ALICE is well suited for such substructure measurements due to its precise charged-particle tracking, which enables high-efficiency measurements of narrow splittings in jets down to low transverse momentum. In these proceedings several recent jet substructure measurements in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV are reported, for both ungroomed jets and jets that have been groomed using the Soft Drop and Dynamical Grooming algorithms. Measurements of the groomed jet radius, ${\theta }_g\equiv R_g/R$; the groomed jet momentum fraction, $z_g$; and the groomed relative transverse momentum, $k_{\mathrm{T},\mathrm{g}}$ are reported. These measurements show direct evidence of modification of the angular structure of jets in the QGP, and provide new constraints on the search for large-angle scattering of jets off of quasi-particles by interaction with the QGP. New measurements of sub-jet fragmentation, generalized jet angularities, and jet-axis differences, which provide insight into the angular and momentum structure of modified jets are also presented. Comparisons to model calculations are discussed.

   nucl-exPoS·4 citations
2. 02*

   Real and virtual direct photon measurements with ALICE

   Sebastian Scheid (for the ALICE Collaboration)🇨🇭

   In this contribution the latest measurements of real and virtual photons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV from the ALICE Collaboration are presented. The extracted photon spectra are compared to predictions from state-of-the-art models that explicitly include the whole evolution of the heavy-ion collision as well as measurements at lower energies. Experimental developments that in the future will help to extend the range and procession of the measurements are introduced before concluding with an outlook to possible future measurements at the LHC.

   nucl-exJ.Phys.Conf.Ser.(2023)·0 citations
3. 03*

   Measurement of global spin alignment of vector mesons at RHIC

   Subhash Singha (For STAR collaboration)🇨🇳

   We report the measurements of spin alignment (${\rho }_{00}$) for $K^{\ast 0}$, $\overline{K^{\ast 0}}$, $K^{\ast +}$, and $K^{\ast -}$ vector mesons in RHIC isobar collisions (Zr+Zr and Ru+Ru) at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV. We observe the first non-zero spin alignment for $K^{\ast \pm }$ in heavy-ion collisions. The $K^{\ast \pm }$ ${\rho }_{00}$ is about 3.9$\sigma$ larger than that of $K^{\ast 0}$. The observed difference and the ordering between $K^{\ast \pm }$ and $K^{\ast 0}$ are surprising, and require further inputs from theory. When comparing between the isobar and Au+Au collisions, no significant system size dependence in $K^{\ast 0}$ ${\rho }_{00}$ is observed within uncertainties.

   nucl-exhep-exnucl-thActa Phys.Polon.Supp.(2023)·4 citations
4. 04*

   Investigation of octupole collectivity near the $A=72$ shape-transitional point

   M. Spieker🇺🇸 · L.A. Riley🇺🇸 · P.D. Cottle · K.W. Kemper🇺🇸 · D. Bazin🇺🇸 · S. Biswas🇫🇷 · P.J. Farris · A. Gade🇺🇸 · T. Ginter · S. Giraud🇫🇷 · J. Li🇨🇳 · S. Noji🇺🇸 and 4 other authors

   Enhanced octupole collectivity is expected in the neutron-deficient Ge, Se and Kr isotopes with neutron number $N\approx 40$ and has indeed been observed for ${}^{70,72}$Ge. Shape coexistence and configuration mixing are, however, a notorious challenge for theoretical models trying to reliably predict octupole collectivity in this mass region, which is known to feature rapid shape changes with changing nucleon number and spin of the system. To further investigate the microscopic configurations causing the prolate-oblate-triaxial shape transition at $A\approx 72$ and their influence on octupole collectivity, the rare isotopes ${}^{72}$Se and ${}^{74,76}$Kr were studied via inelastic proton scattering in inverse kinematics. While significantly enhanced octupole strength of $\sim 32$ Weisskopf units (W.u.) was observed for ${}^{72}$Se, only strengths of $\sim 15$ W.u. were observed for ${}^{74,76}$Kr. In combination with existing data, the new data clearly question a simple origin of enhanced octupole strengths around $N=40$. The present work establishes two regions of distinct octupole strengths with a sudden strength increase around the $A=72$ shape transitional point.

   nucl-exnucl-thPRC(2022)·9 citations
5. 05*

   Recoil Proton Telescopes and Parallel Plate Avalanche Counters for the ${}^{235}$U(n,f) cross section measurement relative to H(n,n)H between 10 and 450 MeV neutron energy

   A. Manna🇮🇹 · E. Pirovano🇩🇪 · O. Aberle🇨🇭 · S. Amaducci🇮🇹 · M. Barbagallo🇮🇹 · D.M. Castelluccio🇮🇹 · N. Colonna🇮🇹 · P. Console Camprini🇮🇹 · L. Cosentino🇮🇹 · M. Dietz🇩🇪 · Q. Ducasse🇩🇪 · P. Finocchiaro🇮🇹 and 14 other authors

   With the aim of measuring the ${}^{235}$U(n,f) cross section at the n\_TOF facility at CERN over a wide neutron energy range, a detection system consisting of two fission detectors and three detectors for neutron flux determination was realized. The neutron flux detectors are Recoil Proton Telescopes (RPT), based on scintillators and solid state detectors, conceived to detect recoil protons from the neutron-proton elastic scattering reaction. This system, along with a fission chamber and an array of parallel plate avalanche counters for fission event detection, was installed for the measurement at the n\_TOF facility in 2018, at CERN. An overview of the performances of two RPTs - especially developed for this measurement - and of the parallel plate avalanche counters are described in this article. In particular, the characterization in terms of detection efficiency by Monte Carlo simulations and response to neutron beam, the study of the background, dead time correction and characterization of the samples, are reported. The results of the present investigation show that the performances of these detectors are suitable for accurate measurements of fission reaction cross sections in the range from 10 to 450~MeV.

   nucl-exphysics.ins-detJINST(2023)·4 citations
6. 06*

   Status of the X17 search in Montreal

   G. Azuelos · B. Broerman · D. Bryman · W.C. Chen · H.N. da Luz · L. Doria · A. Gupta · L-A. Hamel · M. Laurin · K. Leach · G. Lefebvre · J-P. Martin and 6 other authors

   At the Montreal Tandem accelerator, an experiment is being set up to measure internal pair creation from the decay of nuclear excited states using a multiwire proportional chamber and scintillator bars surrounding it from the DAPHNE experiment. The acceptance covers a solid angle of nearly 4$\pi$. Preamplifiers and the data acquisition hardware have been designed and tested. The water-cooled ${}^7$LiF target, mounted on an Al foil is in a thin carbon fiber section of the beamline. The experiment will focus at first on a measurement of the internal pair creation from the 18.15 MeV state of ${}^8$Be. Assuming the ATOMKI evaluation of the electron-pair production rate from X17, a Geant4 simulation predicts observation of a clear signal after about two weeks of data taking with a 2 $\mu$A proton beam. The IPC measurement could eventually be extended to the giant dipole resonance of ${}^8$Be, as well as to other nuclei, in particular to ${}^{10}$B.

   ↳ physics.ins-detnucl-exJ.Phys.Conf.Ser.(2022)·23 citations
7. 07*

   EOS: a demonstrator of hybrid optical detector technology

   T. Anderson🇺🇸 · E. Anderssen🇺🇸 · M. Askins🇺🇸 · A. J. Bacon🇺🇸 · Z. Bagdasarian🇺🇸 · A. Baldoni🇺🇸 · N. Barros🇵🇹 · L. Bartoszek🇺🇸 · M. Bergevin🇺🇸 · A. Bernstein🇺🇸 · E. Blucher🇺🇸 · J. Boissevain🇺🇸 and 52 other authors

   EOS is a technology demonstrator, designed to explore the capabilities of hybrid event detection technology, leveraging both Cherenkov and scintillation light simultaneously. With a fiducial mass of four tons, EOS is designed to operate in a high-precision regime, with sufficient size to utilize time-of-flight information for full event reconstruction, flexibility to demonstrate a range of cutting edge technologies, and simplicity of design to facilitate potential future deployment at alternative sites. Results from EOS can inform the design of future neutrino detectors for both fundamental physics and nonproliferation applications.

   ↳ physics.ins-dethep-exnucl-exJINST(2023)·34 citations
8. 08*

   Two-particle azimuthal correlations in $e^{+}{e}^{-}$ collisions at 91--209 GeV with archived ALEPH data at LEP-2

   Yen-Jie Lee (1)🇺🇸 · Yu-Chen Chen (1)🇺🇸 · Yi Chen (1)🇺🇸 · Paoti Chang (2)🇹🇼 · Marcello Maggi (3) ((1) Massachusetts Institute of Technology, (2) National Taiwan University, (3) INFN Bari)🇮🇹

   We present the first measurement of two-particle angular correlations of charged particles produced in $e^{+}{e}^{-}$ annihilation up to $\sqrt{s}=$ 209 GeV. This analysis utilized the archived hadronic $e^{+}{e}^{-}$ data at center-of-mass energy between 91 and 209 GeV collected with the ALEPH detector at LEP between 1992 and 2000. The angular correlation functions are measured over a broad range of pseudorapidity and full azimuth as a function of charged particle multiplicity for the first time with LEP-2 data. At 91 GeV, no significant long-range correlation is observed in either the beam coordinate analysis or the thrust coordinate analysis, where the latter is sensitive to a medium expanding transverse to the color string between the outgoing $q\bar{q}$ pair from the Z boson decays. Results with $e^{+}{e}^{-}$ data at higher collision energy than 91 GeV, providing higher event multiplicity reach up to around 50, are presented for the first time. The thrust axis analysis shows a long-range near-side excess in the two-particle correlation function. We performed Fourier series decomposition of the two-particle correlation functions. In high multiplicity events with more than 50 particles, the extracted Fourier coefficients $v_2$ and $v_3$ magnitudes in data are larger than the MC reference.

   ↳ hep-exnucl-exPoS·0 citations
9. 09*

   Pseudoscalar and Scalar Meson Photoproduction Interpreted by Regge Phenomenology

   Igor I. Strakovsky (GWU)🇺🇸 · William J. Briscoe (GWU)🇺🇸 · Olga Cortes Becerra (GWU)🇺🇸 · Michael Dugger (ASU)🇺🇸 · Gary Goldstein (Tufts U.)🇺🇸 · Victor L. Kashevarov (Mainz U.)🇩🇪 · Axel Schmidt (GWU)🇺🇸 · Peter Solazzo (GWU)🇺🇸 · Byung-Geel Yu (Korea Aerospace U.)🇰🇷

   We have evaluated pseudoscalar and scalar neutral pion photoproduction in $\vec{\gamma }p\to {\pi }^{0}p$ and $\vec{\gamma }p\to a_0^{0}p$ above the resonance region and within Regge phenomenology. Our fit, including GlueX $\Sigma$ pseudoscalar photoproduction data, shows that previous SLAC $\Sigma$ measurements for $\vec{\gamma }p\to {\pi }^{0}p$ above $E_{\gamma }=4\mathrm{GeV}$ are at variance with SLAC data with more recent measurements made by GlueX in vicinity of $E_{\gamma }=9\mathrm{GeV}$. The Regge model predicts that the beam polarization asymmetry $\Sigma$ of the scalar meson is opposite to that of pseudoscalar meson photoproduction, however, the cross sections are similar. While the vector natural parity meson exchange is dominant in both cases, the contribution of the pseudovector unnatural parity meson exchange is very small. Using Regge phenomenology, we predicted high energy behavior for double polarized observables $\mathbb{E}$, $\mathbb{F}$, $\mathbb{G}$, and $\mathbb{H}$ for the reactions $\gamma p\to {\pi }^{0}p$ and $\gamma p\to a_0^{0}p$.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2023)·3 citations
10. 10*

    Role of neutron transfer in the reaction mechanism of ${}^9$Be+${}^{169}$Tm, ${}^{181}$Ta, ${}^{187}$Re and ${}^{197}$Au systems

    Prasanna M. · V. V. Parkar · V. Jha🇮🇳 · A. Parmar · Bhushan A. Kanagalekar · B. G. Hegde

    The contribution of one neutron stripping cross section to the total reaction cross section has been studied for ${}^9$Be projectile incident on ${}^{169}$Tm, ${}^{181}$Ta, ${}^{187}$Re and ${}^{197}$Au targets around Coulomb barrier energy. The measured one neutron stripping cross sections for these systems have been compared with the coupled channel calculations. The recently developed global set of optical model potential parameters for ${}^9$Be projectile has been used in the present calculations. The cumulative of measured complete fusion (CF), incomplete fusion (ICF), one neutron stripping and calculated non-capture breakup (NCBU) cross sections is found to explain almost the reaction cross sections for all the targets. A very small contribution from target inelastic states and elastic breakup may contribute to the remaining part. The percentage fraction of cross section for CF, ICF, one neutron stripping, and NCBU over reaction cross section show the dominance of neutron transfer and NCBU at below barrier energies while CF and ICF processes have the major contribution at above barrier energies.

    ↳ nucl-thnucl-exNPA(2023)·9 citations
11. 11*

    Characterization of ultracold neutron production in thin solid deuterium films at the PSI Ultracold Neutron source

    G. Bison🇨🇭 · B. Blau · W. Chen🇨🇭 · P.-J. Chiu🇨🇭 · M. Daum🇨🇭 · C. Doorenbos🇨🇭 · N. Hild🇨🇭 · K. Kirch🇨🇭 · V. Kletzl🇨🇭 · B. Lauss🇨🇭 · D. Pais🇨🇭 · I. Rienäcker🇨🇭 and 4 other authors

    We determined the ultracold neutron (UCN) production rate by superthermal conversion in the solid deuterium (sD${}_2$) moderator of the UCN source at the Paul Scherrer Institute (PSI). In particular, we considered low amounts of less than $20$mol of D${}_2$, deposited on the cooled moderator vessel surfaces in thin films of a few mm thickness. We measured the isotopic ($c_{\text{HD}}<0.2\%$) and isomeric ($c_{\text{para}}\le 2.7\%$) purity of the deuterium to conclude that absorption and up-scattering at $5$K have a negligible effect on the UCN yield from the thin films. We compared the calculated UCN yield based on the previously measured thermal neutron flux from the heavy water thermal moderator with measurements of the UCN count rates at the beamports. We confirmed our results and thus demonstrate an absolute characterization of the UCN production and transport in the source by simulations.

    ↳ physics.ins-detnucl-exphysics.acc-phPRC(2023)·5 citations
12. 12*

    Charmed hadron production in high-energy nuclear collisions

    Andrea Beraudo🇮🇹 · Arturo De Pace🇮🇹 · Marco Monteno🇮🇹 · Marzia Nardi🇮🇹 · Daniel Pablos🇮🇹 · Francesco Prino🇮🇹

    We present a new model for the description of heavy-flavor hadronization in high-energy nuclear (and possibly hadronic) collisions, where the process takes place not in the vacuum, but in the presence of other color charges. We explore its effect on the charmed hadron yields and kinematic distributions once the latter is applied at the end of transport calculations used to simulate the propagation of heavy quarks in the deconfined fireball produced in nuclear collisions. The model is based on the formation of color-singlet clusters through the recombination of charm quarks with light antiquarks or diquarks from the same fluid cell. This local mechanism of color neutralization leads to a strong space-momentum correlation, which provides a substantial enhancement of charmed baryon production -- with respect to expectations based on $e^{+}{e}^{-}$ collisions -- and of the collective flow of all charmed hadrons. We also discuss the similarities between our model and recently developed mechanisms implemented in QCD event generators to simulate medium corrections to hadronization in the presence of other nearby color charges.

    ↳ hep-phnucl-exnucl-th0 citations
13. 13*

    Signatures of the $\Delta$ isobar in spin observables of ${}^3\mathrm{He}$ electrodisintegration

    A. Deltuva🇱🇹

    The electrodisintegration of ${}^3\mathrm{He}$ is considered focusing on the effects of the $\Delta$ isobar excitation which is treated dynamically on the same footing as nucleons. In the region beyond the quasi-elastic peak the predicted transverse response functions $R_T$ and $R_{T^{\prime }}$ are visibly affected. This leads to sizable $\Delta$ isobar effects for inclusive and exclusive electron polarization asymmetries in particular kinematic regions. A measurement performed in the proposed regime could provide judgment for models of nuclear forces and currents.

    ↳ nucl-thnucl-exPLB(2022)·1 citation
14. 14*

    A detector system for 'absolute' measurements of fission cross sections at n_TOF in the energy range below 200 MeV

    E. Pirovano🇩🇪 · A. Manna🇮🇹 · O. Aberle🇨🇭 · S. Amaducci🇮🇹 · N. Colonna🇮🇹 · P. Console Camprini🇮🇹 · L. Cosentino🇮🇹 · M. Dietz🇩🇪 · Q. Ducasse🇩🇪 · P. Finocchiaro🇮🇹 · C. Massimi🇮🇹 · A. Mengoni🇮🇹 and 5 other authors

    A new measurement of the ${}^{235}$U(n,f) cross section was performed at the neutron time-of-flight facility n_TOF at CERN. The experiment focused on neutron energies from 20 MeV to several hundred MeV, and was normalized to neutron scattering on hydrogen. This is a measurement first of its kind at this facility, in an energy range that was until now not often explored, so the detector development phase was crucial for its success. Two detectors are presented, a parallel plate fission chamber (PPFC) and a recoil proton telescope (RPT), both dedicated to perform measurements in the incident neutron energy range from 30 MeV to 200 MeV. The experiment was designed to minimize statistical uncertainties in the allocated run time. Several efforts were made to ensure that the systematic effects were understood and under control. The results show that the detectors are suited for measurements at n_TOF above 30 MeV, and indicate the path for possible future lines of development.

    ↳ physics.ins-detnucl-exJINST(2023)·3 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.