Mon·Oct 1, 2018Monday·October 1, 2018

1. 01*

   Weak-Interaction Tests via Precision Superallowed $\beta$-Decay Studies at TRIUMF

   Kyle G. Leach🇺🇸 · Jason D. Holt🇨🇦

   Superallowed $\beta$-decay studies provide some of the best constraints on the possibility of additional quark generations, as well as limits on exotic currents in the weak interaction. The three experimental quantities that are required for performing these tests using $0^{+}\to 0^{+}$ nuclear decays (branching ratio, half-life, and $Q$-value) can all be measured to high-precision with rare-isotope beams at the TRIUMF-ISAC facility in Vancouver, Canada. This proceeding presents a brief outline of the general experimental techniques used at TRIUMF over the past 15 years, as well as recent theoretical advances towards {\it ab-initio} isospin-symmetry-breaking corrections to superallowed nuclear decays.

   nucl-exnucl-th3 citations
2. 02*

   ${\Lambda }_{\mathrm{c}}^{+}$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   A measurement of the production of prompt ${\Lambda }_{\mathrm{c}}^{+}$ baryons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC is reported. The ${\Lambda }_{\mathrm{c}}^{+}$ and ${\overline{\Lambda }}_{\mathrm{c}}^{-}$ were reconstructed at midrapidity ($|y|<0.5$) via the hadronic decay channel ${\Lambda }_{\mathrm{c}}^{+}\to \mathrm{p}{\mathrm{K}}_{\mathrm{S}}^0$ (and charge conjugate) in the transverse momentum and centrality intervals $6<p_{\mathrm{T}}<12$ GeV/$c$ and 0-80%. The ${\Lambda }_{\mathrm{c}}^{+}$/D${}^0$ ratio, which is sensitive to the charm quark hadronisation mechanisms in the medium, is measured and found to be larger than the ratio measured in minimum-bias pp collisions at $\sqrt{s}=7$ TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. In particular, the values in p-Pb and Pb-Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties in the common $p_{\mathrm{T}}$ interval covered by the measurements in the two collision system. The ${\Lambda }_{\mathrm{c}}^{+}$/D${}^0$ ratio is also compared with model calculations including different implementations of charm quark hadronisation. The measured ratio is reproduced by models implementing a pure coalescence scenario, while adding a fragmentation contribution leads to an underestimation. The ${\Lambda }_{\mathrm{c}}^{+}$ nuclear modification factor, $R_{\mathrm{AA}}$, is also presented. The measured values of the $R_{\mathrm{AA}}$ of ${\Lambda }_{\mathrm{c}}^{+}$, D${}_{\mathrm{s}}$ and non-strange D mesons are compatible within the combined statistical and systematic uncertainties. They show, however, a hint of a hierarchy $(R_{\mathrm{AA}}^{{\mathrm{D}}^0}<R_{\mathrm{AA}}^{{\mathrm{D}}_{\mathrm{s}}}<R_{\mathrm{AA}}^{{\Lambda }_{\mathrm{c}}^{+}})$, conceivable with a contribution of recombination mechanisms to charm hadron formation in the medium.

   nucl-exhep-exPLB(2019)·104 citations
3. 03*

   Binding-energy independence of reduced single particle strengths derived from $(p,d)$ reactions

   Y.P. Xu🇺🇸 · D.Y. Pang🇨🇳 · X.Y. Yun · C. Wen🇨🇳 · C.X. Yuan🇨🇳 · J.L. Lou🇨🇳

   An overall reduction factor (ORF) is introduced for studying the quenching of single particle strengths through nucleon transfer reactions. The ORF includes contributions of all the probed bound states of the residual nucleus in a transfer reaction and permits a proper comparison with results of inclusive knockout reactions. A systematic analysis is made with 103 sets of angular distribution data of $(p,d)$ reactions on 21 even-even targets with atomic mass numbers from 8 to 56 using the consistent three-body model reaction methodology proposed in [J. Lee, J.A. Tostevin, B.A. Brown, et al., Phys. Rev. C 73, 044608 (2006)]. The extracted ORFs are found to be nearly independent on the nuclear isospin asymmetry, which is different from the systematics of inclusive knockout reactions but is consistent with the recent measurement of $(d,t)$, $(d,3He)$, $(p,2p)$, and $(p,pn)$ reactions on nitrogen and oxygen isotopes and \textit{ab initio} calculations.

   nucl-exnucl-th0 citations
4. 04*

   Jet shape modifications in holographic dijet systems

   Jasmine Brewer🇺🇸 · Andrey Sadofyev🇺🇸 · Wilke van der Schee🇺🇸

   We present a coherent model that combines jet production from perturbative QCD with strongly-coupled jet-medium interactions described in holography. We use this model to study the modification of an ensemble of jets upon propagation through a quark-gluon plasma resembling central heavy ion collisions. Here the modification of the dijet asymmetry depends strongly on the subleading jet width, which can therefore be an important observable for studying jet-medium interactions. We furthermore show that the modification of the shape of the leading jet is relatively insensitive to the dijet asymmetry, whereas the subleading jet shape modification is much larger for more imbalanced dijets. Finally, we compare the results of our holographic model to a recent CMS measurement.

   ↳ hep-phhep-thnucl-exnucl-thPLB(2021)·23 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.