Fri·Mar 29, 2019Friday·March 29, 2019

1. 01*

   Beam energy dependence of (anti-)deuteron production in Au+Au collisions at RHIC

   J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · R. Aoyama · A. Aparin · D. Arkhipkin and 336 other authors

   We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $\sqrt{s_{\text{NN}}}=$7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at RHIC. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter $B_2$ are discussed. We find that the values of $B_2$ for anti-deuterons are systematically lower than those for deuterons, indicating that the correlation volume of anti-baryons is larger than that of baryons at $\sqrt{s_{\text{NN}}}$ from 19.6 to 39 GeV. In addition, values of $B_2$ are found to vary with collision energy and show a broad minimum around $\sqrt{s_{\text{NN}}}=$20 to 40 GeV, which might imply a change of the equation of state of the medium in these collisions.

   nucl-exhep-exnucl-thPRC(2019)·141 citations
2. 02*

   Ionoacoustic detection of swift heavy ions

   Sebastian Lehrack · Walter Assmann · Markus Bender · Daniel Severin · Christina Trautmann · Jörg Schreiber · Katia Parodi

   The maximum energy loss (Bragg peak) located near the end of range is a characteristic feature of ion stopping in matter, which generates an acoustic pulse, if ions are deposited into a medium in adequately short bunches. This so-called ionoacoustic effect has been studied for decades, mainly for astrophysical applications, and it has recently found renewed interest in proton therapy for precise range measurements in tissue. After detailed preparatory studies with 20 MeV protons at the MLL tandem accelerator, ionoacoustic range measurements were performed in water at the upgraded SIS18 synchrotron of GSI with 238U and 124Xe ion beams of energy about 300 MeV/u, and 12C ions of energy about 200 MeV/u using fast beam extraction to get 1 microsecond pulse lengths. Acoustic signals were recorded in axial geometry by standard piezo-based transducers at a 500 kHz mean frequency and evaluated in both the time and frequency domains. The resulting ranges for the different ions and energies were found to agree with Geant4 simulations as well as previous measurements to better than 1%. Given the high accuracy provided by ionoacoustic range measurements in water and their relative simplicity, we propose this new method for stopping power measurements for heavy ions at GeV energies and above. Our experimental results clearly demonstrate the potential of an ionoacoustic particle monitor especially for very intense heavy ion beams foreseen at future accelerator facilities.

   nucl-exphysics.ins-detNucl.Instrum.Meth.A(2020)·0 citations
3. 03*

   Multiplicity dependence for the production of strange hadrons and charged particles in proton-proton collisions

   Prabhakar Palni (for the ALICE Collaboration)🇵🇱

   In this contribution, the production rates and the transverse momentum distributions of strange hadrons are reported as a function of charged particle multiplicity. In this analysis, the data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ALICE detector at the LHC are used. It is found that the production rate of $K_S^0$, $\Lambda$, ${\Xi }^{\pm }$, and $\Omega$ increases with multiplicity faster than that for charged particles. The higher the strangeness content of the hadron, the more pronounced is the increase. Moreover, the energy and multiplicity dependence of charged particle production in pp collisions are presented and the results are compared to predictions from Monte Carlo (MC) event generators. It turns out that the average multiplicity density increases steeply with center-of-mass energy for high multiplicity classes.

   nucl-exActa Phys.Polon.B(2019)·4 citations
4. 04*

   A prototype for SANDD: A highly-segmented pulse-shape-sensitive plastic scintillator detector incorporating silicon photomultiplier arrays

   Viacheslav A. Li🇺🇸 · Timothy M. Classen🇺🇸 · Steven A. Dazeley🇺🇸 · Mark J. Duvall🇺🇸 · Igor Jovanovic🇺🇸 · Andrew N. Mabe🇺🇸 · Edward T. E. Reedy🇺🇸 · Felicia Sutanto🇺🇸

   We report the first clear observation of neutron/gamma-ray pulse-shape sensitivity of a fully-instrumented 8 $\times$ 8 array of plastic scintillator segments coupled to two 5 cm $\times$ 5 cm 64-channel SiPM arrays as part of a study of the key metrics of a prototype antineutrino detector module designed for directional sensitivity. SANDD (a Segmented AntiNeutrino Directional Detector) will eventually comprise a central module of 64 elongated segments of ${}^6$Li-doped pulse-shape-sensitive scintillator rods, each with a square cross section of 5.4 mm $\times$ 5.4 mm, surrounded by larger cross section bars of the same material. The most important metrics with the potential to impact the performance of the central module of SANDD are neutron and gamma-ray pulse-shape sensitivity using silicon photomultipliers (SiPMs), particle identification via scintillator rod multiplicity, and energy and position resolution. As a first step, we constructed a prototype detector to investigate the performance of a central SANDD-like module using two 64-channel SiPM arrays and rods of undoped pulse-shape-sensitive plastic scintillator.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2019)·15 citations
5. 05*

   Delta mass shift as a thermometer of kinetic decoupling in Au+Au reactions at 1.23 AGeV

   Tom Reichert🇩🇪 · Paula Hillmann🇩🇪 · Ayut Limphirat🇹🇭 · Christoph Herold🇹🇭 · Marcus Bleicher🇩🇪

   The HADES experiment at GSI will soon provide data on the production and properties of $\Delta$(1232) baryons from Au+Au reactions at 1.23 AGeV. Using the UrQMD model, we predict the yield and spectra of $\Delta$(1232) resonances. In addition we show that one expects to observe a mass shift of the $\Delta$(1232) resonance on the order of 50 MeV in the reconstructable $\Delta$(1232) mass distribution. This mass shift can be understood in terms of late stage $\Delta$(1232) formation with limited kinetic energy. We show how the mass shift can be used to constrain the kinetic decoupling temperature of the system.

   ↳ nucl-thnucl-exJ.Phys.G(2019)·20 citations
6. 06*

   Measurements of the jet internal sub-structure and its relevance to parton shower evolution in p+p and Au+Au collisions at STAR

   Raghav Kunnawalkam Elayavalli (for the STAR Collaboration)🇺🇸

   Recent measurements of jet structure modifications at RHIC and LHC highlight the importance of differential measurements to study the nature of jet quenching. Since these jet structure observables are intimately dependent on parton evolution in both the angular and energy scales, measurements are needed to disentangle these two scales in order to probe the medium at different length scales to study its characteristic properties such as the coherence length. To that effect, the STAR collaboration presents fully unfolded results of a jet's sub-structure via the SoftDrop shared momentum fraction ($z_g$) and the groomed jet radius ($R_g$) in p+p collisions at $\sqrt{s}=$ 200 GeV as a function of jet momenta. Having established the p+p baseline, we present the first measurement of the jet's inherent angular structure in Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV via an experimentally robust observable related to the SoftDrop $R_g$: the opening angle between the two leading sub-jets (${\theta }_{SJ}$). In Au+Au collisions at STAR, we utilize a specific di-jet selection as introduced in our previous momentum imbalance ($A_J$) measurement and the recoil jet spectra differentially as a function of jet transverse momentum belonging to particular angular lasses based on the ${\theta }_{SJ}$ observable. With such measurements, we probe the medium response to jets at a particular resolution scale and find no significant differences in quenching for jets of different angular scales as given by ${\theta }_{SJ}$.

   ↳ hep-exnucl-exPoS(2018)·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.