Thu·Jul 25, 2019Thursday·July 25, 2019

1. 01*

   Measurement of $W^{\pm }$ boson production in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ATLAS detector

   ATLAS Collaboration

   A measurement of $W^{\pm }$ boson production in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is reported using data recorded by the ATLAS experiment at the LHC in 2015, corresponding to a total integrated luminosity of $0.49\mathrm{n}{\mathrm{b}}^{-1}$. The $W^{\pm }$ bosons are reconstructed in the electron or muon leptonic decay channels. Production yields of leptonically decaying $W^{\pm }$ bosons, normalised by the total number of minimum-bias events and the nuclear thickness function, are measured within a fiducial region defined by the detector acceptance and the main kinematic requirements. These normalised yields are measured separately for $W^{+}$ and $W^{-}$ bosons, and are presented as a function of the absolute value of pseudorapidity of the charged lepton and of the collision centrality. The lepton charge asymmetry is also measured as a function of the absolute value of lepton pseudorapidity. In addition, nuclear modification factors are calculated using the $W^{\pm }$ boson production cross-sections measured in $pp$ collisions. The results are compared with predictions based on next-to-leading-order calculations with CT14 parton distribution functions as well as with predictions obtained with the EPPS16 and nCTEQ15 nuclear parton distribution functions. No dependence of normalised production yields on centrality and a good agreement with predictions are observed for mid-central and central collisions. For peripheral collisions, the data agree with predictions within 1.7 (0.9) standard deviations for $W^{-}$ ($W^{+}$) bosons.

   nucl-exhep-exEPJC(2019)·65 citations
2. 02*

   Towards a consistent understanding of the exotic nucleus ${}_{14}^{42}S{i}_{28}$

   Syed Afsar Abbas🇮🇳 · Anisul Ain Usmani🇮🇳 · Usuf Rahaman🇮🇳 · Mohammad Ikram

   The issue of whether ${}_{14}^{42}S{i}_{28}$ is doubly magical or not has been a contentious one. Fridmann {\it et al.} (Nature 435 (2005) 922) through studies of two-proton knockout reaction ${}_{16}^{44}{S}_{28}{\to }_{14}^{42}S{i}_{28}$, presented a strong empirical evidence in support of magicity and sphericity of ${}_{14}^{42}S{i}_{28}$. However in complete conflict with this, Bastin {\it et al.} (Phys. Rev. Lett. 99 (2007) 022503) gave equally strong empirical evidences, to show that the N = 28 magicity had completely collapsed, and that ${}_{14}^{42}S{i}_{28}$ was a well deformed nucleus. At present the popular consensus (Gade {\it et al.}, Phys. Rev. Lett. 122 (2019) 222501) strongly supports the latter one and discards the former one. Here, while we accept the latter experiment as being fine and good, through a careful study of an RMF model calculation, we show that actually the experimental results of Fridmann are also independently good and consistent. As per the Fridmann experiment, the sphericity and magicity of ${}_{14}^{42}S{i}_{28}$ is manifested only through proton number Z=14 being a strong magic number, while the neutron magic number N=28 disappears (or goes into hiding); and still this nucleus is spherical. This is a new and amazing property manifesting itself in this exotic nucleus ${}_{14}^{42}S{i}_{28}$. In this paper we provide a consistent understanding of this novel reality within a QCD based model. This model, which has been successful in explanation of the halo phenomenon in exotic nuclei, comes forward to provide the physical reason as to why the Fridmann experiment is correct. This QCD based model shows that it is tritons, as elementary entity making up ${}_{14}^{42}S{i}_{28}$, which then provides consistency to the above amazing conclusions arising from the Fridmann experiment.

   ↳ nucl-thnucl-exIndian J.Pure Appl.Phys.(2020)·2 citations
3. 03*

   Inclusive Jet Longitudinal Double-spin Asymmetry $A_{LL}$ Measurements in 510 GeV Polarized $pp$ Collisions at STAR

   Zilong Chang🇺🇸

   In this analysis, I perform the first ever measurement of \(A_{LL}\) for inclusive jet production in \(pp\) collisions at the higher beam energy of \(\sqrt{s}\) = 510 GeV, based on data that STAR recorded during 2012. The higher beam energy extends the sensitivity to gluon polarization down to \(x \sim 0.02\). The high statistics of the data set and the small size of the physics asymmetries, compared to the previous measurements at 200 GeV, required the development of several new or improved analysis procedures in order to minimize the systematic uncertainties. These include: the first implementation by STAR of an underlying event subtraction during jet reconstruction, a much improved technique to estimate the trigger and reconstruction bias effects, a detailed optimization of the PYTHIA tune that provides a much better match between the experimental data and simulated Monte Carlo events, and a new procedure to estimate the uncertainties associated with the PYTHIA tune parameters. The results for inclusive jet \(A_{LL}\) \textit{vs}.\@ jet \(p_T\) in 510 GeV \(pp\) collisions are presented. They are found to be consistent with predictions from recent global analyses of the polarized PDFs that included prior RHIC data in the fit. They are also consistent with the previous STAR inclusive jet \(A_{LL}\) measurements at \(\sqrt{s}\) = 200 GeV in the region where the kinematics for the two beam energies overlap. These results will provide important new constraints on the gluon polarization in the proton in the \(x\) region below that sampled in 200 GeV \(pp\) collisions.

   ↳ hep-exnucl-ex0 citations
4. 04*

   Cascade Calculations with Schematic Interactions

   Levering Wolfe🇺🇸 · Larry Zamick🇺🇸

   In previous works we considered schematic Hamiltonians represented by simplified matrices. We defined 2 transition operators and calculated transition strengths from the ground state to all exited states. In many cases the strengths decreased nearly exponentially with excitation energy. Now we do the reverse We start with the highest energy state and calculate the cascade of transitions until the ground states is reached. On a log plot we show the average transition strength as a function of the number of energy intervals that were crossed. We give an analytic proof of exponential behavior for transition strength in the weak coupling limit for the T2 transition operator.

   ↳ nucl-thnucl-exIJMPE(2019)·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.