Fri·Jun 26, 2015Friday·June 26, 2015

1. 01*

   Search for weakly decaying $\overline{\Lambda \mathrm{n}}$ and $\Lambda \Lambda$ exotic bound states in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV

   ALICE Collaboration

   We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible $\overline{\Lambda \mathrm{n}}$ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV, by invariant mass analysis in the decay modes $\overline{\Lambda \mathrm{n}}\to \bar{\mathrm{d}}{\pi }^{+}$ and H-dibaryon $\to \Lambda \mathrm{p}{\pi }^{-}$. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.

   nucl-exhep-exPLB(2016)·55 citations
2. 02*

   Probing Parton Dynamics of QCD Matter with $\Omega$ and $\varphi$ Production

   STAR Collaboration: L. Adamczyk🇵🇱 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · J. Alford🇺🇸 · A. Aparin🇷🇺 · D. Arkhipkin🇺🇸 · E. C. Aschenauer🇺🇸 · G. S. Averichev🇷🇺 · V. Bairathi🇮🇳 and 321 other authors

   We present measurements of $\Omega$ and $\varphi$ production at mid-rapidity from Au+Au collisions at nucleon-nucleon center-of-mass energies $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27 and 39 GeV by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Motivated by the coalescence formation mechanism for these strange hadrons, we study the ratios of $N({\Omega }^{-}+{\Omega }^{+})/(2N(\varphi ))$. These ratios as a function of transverse momentum ($p_T$) fall on a consistent trend at high collision energies, but start to show deviations in peripheral collisions at $\sqrt{s_{NN}}$ = 19.6, 27 and 39 GeV, and in central collisions at 11.5 GeV in the intermediate $p_T$ region of 2.4-3.6 GeV/c. We further evaluate empirically the strange quark $p_T$ distributions at hadronization by studying the $\Omega /\varphi$ ratios scaled by the number of constituent quarks. The NCQ-scaled $\Omega /\varphi$ ratios show a suppression of strange quark production in central collisions at 11.5 GeV compared to $\sqrt{s_{NN}}>=19.6$ GeV. The shapes of the presumably thermal strange quark distributions in 0-60% most central collisions at 7.7 GeV show significant deviations from those in 0-10% most central collisions at higher energies. These features suggest that there is likely a change of the underlying strange quark dynamics in the transition from quark-matter to hadronic matter at collision energies below 19.6 GeV.

   nucl-exPRC(2016)·84 citations
3. 03*

   Experimental study of ultracold neutron production in pressurized superfluid helium

   P. Schmidt-Wellenburg🇨🇭 · J. Bossy · E. Farhi · M. Fertl🇺🇸 · K.K.H. Leung🇫🇷 · A. Rahli · T. Soldner🇫🇷 · O. Zimmer🇫🇷

   We have investigated experimentally the pressure dependence of the production of ultracold neutrons (UCN) in superfluid helium in the range from saturated vapor pressure to 20bar. A neutron velocity selector allowed the separation of underlying single-phonon and multiphonon pro- cesses by varying the incident cold neutron (CN) wavelength in the range from 3.5 to 10Å. The predicted pressure dependence of UCN production derived from inelastic neutron scattering data was confirmed for the single-phonon excitation. For multiphonon based UCN production we found no significant dependence on pressure whereas calculations from inelastic neutron scattering data predict an increase of 43(6)% at 20bar relative to saturated vapor pressure. From our data we conclude that applying pressure to superfluid helium does not increase the overall UCN production rate at a typical CN guide.

   nucl-exphysics.ins-detPRC(2015)·16 citations
4. 04*

   Measurement of higher cumulants of net-charge multiplicity distributions in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=7.7-200$ GeV

   A. Adare · S. Afanasiev · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · H. Al-Bataineh · J. Alexander · H. Al-Ta'ani · A. Angerami · K. Aoki · N. Apadula and 501 other authors

   We report the measurement of cumulants ($C_n,n=1\dots 4$) of the net-charge distributions measured within pseudorapidity ($|\eta |<0.35$) in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=7.7-200$ GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider. The ratios of cumulants (e.g. $C_1/C_2$, $C_3/C_1$) of the net-charge distributions, which can be related to volume independent susceptibility ratios, are studied as a function of centrality and energy. These quantities are important to understand the quantum-chromodynamics phase diagram and possible existence of a critical end point. The measured values are very well described by expectation from negative binomial distributions. We do not observe any nonmonotonic behavior in the ratios of the cumulants as a function of collision energy. The measured values of $C_1/C_2=\mu /{\sigma }^2$ and $C_3/C_1=S{\sigma }^3/\mu$ can be directly compared to lattice quantum-chromodynamics calculations and thus allow extraction of both the chemical freeze-out temperature and the baryon chemical potential at each center-of-mass energy.

   nucl-exPRC(2016)·110 citations
5. 05*

   Modeling proton- and light ion-induced reactions at low energies in the MARS15 code

   I.L. Rakhno · N.V. Mokhov (Fermilab) K.K. Gudima (IAP, Chisinau)

   An implementation of both ALICE code and TENDL evaluated nuclear data library in order to describe nuclear reactions induced by low-energy projectiles in the Monte Carlo code MARS15 is presented. Comparisons between results of modeling and experimental data on reaction cross sections and secondary particle distributions are shown.

   ↳ physics.acc-phnucl-ex0 citations
6. 06*

   Measurement of absorption and charge exchange of ${\pi }^{+}$ on carbon

   K. Ieki🇯🇵 · E. S. Pinzon Guerra🇨🇦 · S. Berkman🇨🇦 · S. Bhadra🇨🇦 · C. Cao🇨🇦 · P. de Perio🇨🇦 · Y. Hayato🇯🇵 · M. Ikeda🇯🇵 · Y. Kanazawa🇯🇵 · J. Kim🇨🇦 · P. Kitching🇨🇦 · K. Mahn🇺🇸 and 10 other authors

   The combined cross section for absorption and charge exchange interactions of positively charged pions with carbon nuclei for the momentum range 200 MeV/c to 300 MeV/c have been measured with the DUET experiment at TRIUMF. The uncertainty is reduced by nearly half compared to previous experiments. This result will be a valuable input to existing models to constrain pion interactions with nuclei.

   ↳ hep-exnucl-exphysics.ins-detPRC(2015)·17 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.