Tue·Feb 27, 2018Tuesday·February 27, 2018

1. 01*

   Measurement of the normalized ${}^{238}$U(n,f)/${}^{235}$U(n,f) cross section ratio from threshold to 30 MeV with the fission Time Projection Chamber

   R. J. Casperson🇺🇸 · D. M. Asner🇺🇸 · J. Baker🇺🇸 · R. G. Baker🇺🇸 · J. S. Barrett🇺🇸 · N. S. Bowden🇺🇸 · C. Brune🇺🇸 · J. Bundgaard🇺🇸 · E. Burgett🇺🇸 · D. A. Cebra🇺🇸 · T. Classen🇺🇸 · M. Cunningham🇺🇸 and 52 other authors

   The normalized ${}^{238}$U(n,f)/${}^{235}$U(n,f) cross section ratio has been measured using the NIFFTE fission Time Projection Chamber from the reaction threshold to $30$~MeV. The fissionTPC is a two-volume MICROMEGAS time projection chamber that allows for full three-dimensional reconstruction of fission-fragment ionization profiles from neutron-induced fission. The measurement was performed at the Los Alamos Neutron Science Center, where the neutron energy is determined from neutron time-of-flight. The ${}^{238}$U(n,f)/${}^{235}$U(n,f) ratio reported here is the first cross section measurement made with the fissionTPC, and will provide new experimental data for evaluation of the ${}^{238}$U(n,f) cross section, an important standard used in neutron-flux measurements. Use of a development target in this work prevented the determination of an absolute normalization, to be addressed in future measurements. Instead, the measured cross section ratio has been normalized to ENDF/B-VIII.$\beta$5 at 14.5 MeV.

   nucl-exphysics.ins-detPRC(2018)·16 citations
2. 02*

   Transverse momentum spectra and nuclear modification factors of charged particles in pp, p-Pb and Pb-Pb collisions at the LHC

   ALICE Collaboration

   We report the measured transverse momentum ($p_{\mathrm{T}}$) spectra of primary charged particles from pp, p-Pb and Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV in the kinematic range of $0.15<p_{\mathrm{T}}<50$ GeV/$c$ and $|\eta |<0.8$. A significant improvement of systematic uncertainties motivated the reanalysis of data in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV, as well as in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV, which is also presented. Spectra from Pb-Pb collisions are presented in nine centrality intervals and are compared to a reference spectrum from pp collisions scaled by the number of binary nucleon-nucleon collisions. For central collisions, the $p_{\mathrm{T}}$ spectra are suppressed by more than a factor of 7 around 6-7 GeV/$c$ with a significant reduction in suppression towards higher momenta up to 30 GeV/$c$. The nuclear modification factor $R_{\mathrm{pPb}}$, constructed from the pp and p-Pb spectra measured at the same collision energy, is consistent with unity above 8 GeV/$c$. While the spectra in both pp and Pb-Pb collisions are substantially harder at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV compared to 2.76 TeV, the nuclear modification factors show no significant collision energy dependence. The obtained results should provide further constraints on the parton energy loss calculations to determine the transport properties of the hot and dense QCD matter.

   nucl-exhep-exJHEP(2018)·359 citations
3. 03*

   Measurement of the D-meson nuclear modification factor and elliptic flow in Pb-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 5.02 TeV with ALICE at the LHC

   Syaefudin Jaelani (for the ALICE Collaboration)🇳🇱

   Heavy-flavour hadrons are effective probes to study the Quark-Gluon Plasma (QGP) formed in ultra-relativistic heavy-ion collisions. The ALICE Collaboration measured the D-mesons (D${}^0$, D${}^{+}$, D*${}^{+}$ and D${}_{\text{s}}^{+}$) production in Pb-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 5.02 TeV. The in-medium energy loss can be studied by means of the nuclear modification factor ($R_{\text{AA}}$). The comparison between the D${}_{\text{s}}^{+}$ and the non-strange D-meson $R_{\text{AA}}$ can help to study the hadronisation mechanism of the charm quark in the QGP. In semi-central collisions the measurement of the D-meson elliptic flow, $v_2$, at low $p_{\text{T}}$ allows to investigate the participation of the heavy quarks in the collective expansion of the system while at high $p_{\text{T}}$ it constrains the path-length dependence of the energy loss. Furthermore the Event-Shape Engineering (ESE) technique is used to measure D-meson elliptic flow in order to study the coupling of the charm quarks to the light quarks of the underlying medium.

   nucl-exInt.J.Mod.Phys.Conf.Ser.(2018)·7 citations
4. 04*

   Ionization Electron Signal Processing in Single Phase LArTPCs I. Algorithm Description and Quantitative Evaluation with MicroBooNE Simulation

   MicroBooNE collaboration: C. Adams🇺🇸 · R. An🇺🇸 · J. Anthony🇬🇧 · J. Asaadi🇺🇸 · M. Auger🇨🇭 · L. Bagby🇺🇸 · S. Balasubramanian🇺🇸 · B. Baller🇺🇸 · C. Barnes🇺🇸 · G. Barr🇬🇧 · M. Bass🇬🇧 · F. Bay🇹🇷 and 156 other authors

   We describe the concept and procedure of drifted-charge extraction developed in the MicroBooNE experiment, a single-phase liquid argon time projection chamber (LArTPC). This technique converts the raw digitized TPC waveform to the number of ionization electrons passing through a wire plane at a given time. A robust recovery of the number of ionization electrons from both induction and collection anode wire planes will augment the 3D reconstruction, and is particularly important for tomographic reconstruction algorithms. A number of building blocks of the overall procedure are described. The performance of the signal processing is quantitatively evaluated by comparing extracted charge with the true charge through a detailed TPC detector simulation taking into account position-dependent induced current inside a single wire region and across multiple wires. Some areas for further improvement of the performance of the charge extraction procedure are also discussed.

   ↳ physics.ins-dethep-exnucl-exJINST(2018)·192 citations
5. 05*

   Backbendings of Superdeformed bands in ${}^{36,40}$Ar

   Xu-Hui Xiang · Xiao-Tao He🇨🇳

   Experimentally observed superdeformed (SD) rotational bands in ${}^{36}$Ar and ${}^{40}$Ar are studied by the cranked shell model (CSM) with the paring correlations treated by a particle-number-conserving (PNC) method. This is the first time the PNC-CSM calculations are performed on the light nuclear mass region around $A=40$. The experimental kinematic moments of inertia $J^{(1)}$ versus rotational frequency are reproduced well. The backbending of the SD band at frequency around $\hslash \omega =1.5$ MeV in ${}^{36}$Ar is attributed to the sharp rise of the simultaneous alignments of the neutron and proton $1d_{5/2}[202]5/2$ pairs and $1f_{7/2}[321]3/2$ pairs, which is the consequence of the band crossing between the $1d_{5/2}[202]5/2$ and $1f_{7/2}[321]3/2$ configuration states. The gentle upbending at the low frequency of the SD band in ${}^{40}$Ar is mainly effected by the alignments of the neutron $1f_{7/2}[321]3/2$ pairs and proton $1d_{5/2}[202]5/2$ pairs. The PNC-CSM calculations show that besides the diagonal parts, the off-diagonal parts of the alignments play an important role in the rotational behavior of the SD bands.

   ↳ nucl-thnucl-exCPC(2018)·6 citations
6. 06*

   ${\eta }^{\prime }$ Production in Nucleus-Nucleus collisions as a probe of chiral dynamics

   Giorgio Torrieri🇧🇷

   We argue that, because of the peculiar properties of the ${\eta }^{\prime }$ meson, it is a promising probe of "chiral" dynamics. In particular, we show that a rotating gluon-dominated plasma might lead to an enhanced production of ${\eta }^{\prime }$ w.r.t. statistical model expectations. The presence of a strong topological susceptibility might give a similar effect. In both cases, unlike the statistical model,we expect a non-trivial dependence on event geometry, such as initial volume and impact parameter. Hence, an observation of ${\eta }^{\prime }/{\pi }^0$ ratio depending strongly on impact parameter might be a good indication of chiral effects, either from vorticity or topological phases of QCD

   ↳ nucl-thhep-phnucl-exPRC(2018)·2 citations
7. 07*

   D-meson production in proton-proton collisions with ALICE at the LHC

   Julien Hamon (for the ALICE Collaboration)🇫🇷

   In this paper, an overview of recent ${\mathrm{D}}^0$, ${\mathrm{D}}^{+}$ and ${\mathrm{D}}^{\ast +}$ measurements, performed by ALICE in proton--proton collisions at $\sqrt{s}=2.76$, 5, 7, 8 and 13 TeV, is reported. The minimum-bias production cross sections, as well as their energy and species dependences, are compared to perturbative QCD calculations. The evolution of the D-meson yields with the event multiplicity is compared to phenomenological models.

   ↳ hep-exnucl-exNucl.Part.Phys.Proc.(2018)·5 citations
8. 08*

   Inclusive prompt photon production in electron-nucleus scattering at small x

   Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸

   We compute the differential cross-section for inclusive prompt photon production in deeply inelastic scattering (DIS) of electrons on nuclei at small $x$ in the framework of the Color Glass Condensate (CGC) effective theory. The leading order (LO) computation in this framework resums leading logarithms in $x$ as well as power corrections to all orders in $Q_{s,A}^2/Q^2$, where $Q_{s,A}(x)$ is the nuclear saturation scale. This LO result is proportional to universal dipole and quadrupole Wilson line correlators in the nucleus. In the soft photon limit, the Low-Burnett-Kroll theorem allows us to recover existing results on inclusive DIS dijet production. The $k_{\perp }$ and collinearly factorized expressions for prompt photon production in DIS are also recovered in a leading twist approximation to our result. In the latter case, our result corresponds to the dominant next-to-leading order (NLO) perturbative QCD contribution at small $x$. We next discuss the computation of the NLO corrections to inclusive prompt photon production in the CGC framework. In particular, we emphasize the advantages for higher order computations in inclusive photon production, and for fully inclusive DIS, arising from the simple momentum space structure of the dressed quark and gluon "shock wave" propagators in the "wrong" light cone gauge $A^{-}=0$ for a nucleus moving with $P_N^{+}\to \infty$.

   ↳ hep-phnucl-exnucl-thJHEP(2018)·43 citations
9. 09*

   Pion and kaon valence-quark quasiparton distributions

   Shu-Sheng Xu🇨🇳 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸 · Hong-Shi Zong🇨🇳

   Algebraic Ansaetze for the Poincaré-covariant Bethe-Salpeter wave functions of the pion and kaon are used to calculate their light-front wave functions (LFWFs), parton distribution amplitudes (PDAs), quasi-PDAs (qPDAs), valence parton distribution functions (PDFs), and quasi-PDFs (qPDFs). The LFWFs are broad, concave functions; and the scale of flavour-symmetry violation in the kaon is roughly 15%, being set by the ratio of emergent masses in the $s$-and $u$-quark sectors. qPDAs computed with longitudinal momentum $P_z=1.75$GeV provide a semiquantitatively accurate representation of the objective PDA; but even with $P_z=3$GeV, they cannot provide information about this amplitude's endpoint behaviour. On the valence-quark domain, similar outcomes characterise qPDFs. In this connection, however, the ratio of kaon-to-pion $u$-quark qPDFs is found to provide a good approximation to the true PDF ratio on $0.3\lesssim x\lesssim 0.8$, suggesting that with existing resources computations of ratios of quasi-parton-distributions can yield results that support empirical comparison.

   ↳ nucl-thhep-lathep-phnucl-exPRD(2018)·89 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.