Tue·Feb 16, 2016Tuesday·February 16, 2016

1. 01*

   Updates on the Studies of $N^{\ast }$ Structure with CLAS and the Prospects with CLAS12

   V. I. Mokeev🇺🇸

   The recent results on ${\gamma }_{v}p{N}^{\ast }$ electrocouplings from analyses of the data on exclusive meson electroproduction off protons measured with the CLAS detector at Jefferson Lab are presented. The impact of these results on the exploration of the excited nucleon state structure and non-perturbative strong interaction dynamics behind its formation is outlined. The future extension of these studies in the experiments with the CLAS12 detector in the upgraded Hall-B at JLab will provide for the first time ${\gamma }_{v}p{N}^{\ast }$ electrocouplings of all prominent resonances at the still unexplored distance scales that correspond to extremely low (0.05 GeV${}^2<Q^2<$ 0.5 GeV${}^2$) and the highest photon virtualities (5.0 GeV${}^2<Q^2<$ 12.0 GeV${}^2$) ever achieved in the exclusive electroproduction measurements. The expected results will address the most important open problems of the Standard Model: on the nature of more than 98\% of hadron mass, quark-gluon confinement and emergence of the excited nucleon state structure from the QCD Lagrangian, as well as allowing a search for the new states of hadron matter predicted from the first principles of QCD, the so-called hybrid baryons.

   nucl-exhep-exhep-phFew Body Syst.(2016)·8 citations
2. 02*

   Centrality dependence of subthreshold $\varphi$ meson production in Ni+Ni collisions at 1.9A GeV

   K. Piasecki🇵🇱 · Z. Tymiński🇵🇱 · N. Herrmann🇩🇪 · R. Averbeck🇩🇪 · A. Andronic🇩🇪 · V. Barret🇫🇷 · Z. Basrak🇭🇷 · N. Bastid🇫🇷 · M.L. Benabderrahmane🇩🇪 · M. Berger🇩🇪 · P. Buehler🇦🇹 · M. Cargnelli🇦🇹 and 61 other authors

   We analysed the $\varphi$ meson production in central Ni+Ni collisions at the beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found the production probability per event of $[8.6\pm 1.6(\text{stat})\pm 1.5(\text{syst})]\times 10^{-4}$. This new data point allows for the first time to inspect the centrality dependence of the subthreshold $\varphi$ meson production in heavy-ion collisions. The rise of $\varphi$ meson multiplicity per event with mean number of participants can be parameterized by the power function with exponent $\alpha =1.8\pm 0.6$. The ratio of $\varphi$ to ${\text{K}}^{-}$ production yields seems not to depend within the experimental uncertainties on the collision centrality, and the average of measured values was found to be $0.36\pm 0.05$.

   nucl-exPRC(2016)·15 citations
3. 03*

   PHENIX results on Bose-Einstein correlation functions

   Dániel Kincses (for the PHENIX Collaboration)🇭🇺

   Measurement of Bose-Einstein or HBT correlations of identified charged particles provide insight into the space-time structure of particle emitting sources in heavy-ion collisions. In this paper we present the latest results from the RHIC PHENIX experiment on such measurements.

   nucl-exActa Phys.Polon.Supp.(2016)·2 citations
4. 04*

   Evolution of the jet opening angle distribution in holographic plasma

   Krishna Rajagopal🇺🇸 · Andrey V. Sadofyev🇺🇸 · Wilke van der Schee🇺🇸

   We use holography to analyze the evolution of an ensemble of jets, with an initial probability distribution for their energy and opening angle as in proton-proton (pp) collisions, as they propagate through an expanding cooling droplet of strongly coupled plasma as in heavy ion collisions. We identify two competing effects: (i) each individual jet widens as it propagates; (ii) the opening angle distribution for jets emerging from the plasma within any specified range of energies has been pushed toward smaller angles, comparing to pp jets with the same energies. The second effect arises because small-angle jets suffer less energy loss and because jets with a higher initial energy are less probable in the ensemble. We illustrate both effects in a simple two-parameter model, and find that their consequence in sum is that the opening angle distribution for jets in any range of energies contains fewer narrow and wide jets. Either effect can dominate in the mean opening angle, for not unreasonable values of the parameters. So, the mean opening angle for jets with a given energy can easily shift toward smaller angles, as experimental data may indicate, even while every jet in the ensemble broadens.

   ↳ nucl-thhep-phhep-thnucl-exPRL(2016)·70 citations
5. 05*

   Combined analysis of the ${\pi }^{-}p\to K^0\Lambda$, $\eta n$ reactions in a chiral quark model

   Li-Ye Xiao · Fan Ouyang · Xian-Hui Zhong

   A combined analysis of the reactions ${\pi }^{-}p\to K^0\Lambda$ and $\eta n$ is carried out with a chiral quark model. The data in the center-of-mass (c.m.) energy range from threshold up to $W\simeq 1.8$ GeV are reasonably described. For ${\pi }^{-}p\to K^0\Lambda$, it is found that $N(1535)S_{11}$ and $N(1650)S_{11}$ paly crucial roles near threshold. The $N(1650)S_{11}$ resonance contributes to the reaction through configuration mixing with $N(1535)S_{11}$. The constructive interference between $N(1535)S_{11}$ and $N(1650)S_{11}$ is responsible for the peak structure around threshold in the total cross section. The $n$-pole, $u$- and $t$-channel backgrounds provide significant contributions to the reaction as well. While, for the ${\pi }^{-}p\to \eta n$ process, the "first peak" in the total cross section is dominant by $N(1535)S_{11}$, which has a sizeable destructive interference with $N(1650)S_{11}$. Around $P_{\pi }\simeq$ 1.0 GeV/c ($W\simeq 1.7$ GeV), there seems to be a small bump structure in the total cross section, which might be explained by the interference between the $u$-channel and $N(1650)S_{11}$. The $N(1520)D_{13}$ resonance notably affects the angle distributions of the cross sections, although less effects are seen in the total cross section. The role of $P$-wave state $N(1720)P_{13}$ should be further confirmed by future experiments. If $N(1720)P_{13}$ has a narrow width of $\Gamma \simeq 120$ MeV as found in our previous work by a study of the ${\pi }^0$ photoproduction processes, obvious evidence should be seen in the ${\pi }^{-}p\to K^0\Lambda$ and $\eta n$ processes as well.

   ↳ nucl-thhep-phnucl-exPRC(2016)·8 citations
6. 06*

   Precision measurement of the nuclear polarization in laser-cooled, optically pumped ${}^{37}\mathrm{K}$

   Benjamin Fenker · John A. Behr · Dan Melconian · Rhys M. A. Anderson · Melissa Anholm · Daniel Ashery · Richard S. Behling · Iuliana Cohen · Ioana Craiciu · John M. Donohue · Christian Farfan · Daniel Friesen and 9 other authors

   We report a measurement of the nuclear polarization of laser-cooled, optically-pumped ${}^{37}\mathrm{K}$ atoms which will allow us to precisely measure angular correlation parameters in the beta-decay of the same atoms. These results will be used to test the $V-A$ framework of the weak interaction at high precision. At the TRIUMF Neutral Atom Trap (TRINAT), a magneto-optical trap (MOT) confines and cools neutral ${}^{37}\mathrm{K}$ atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of $P=0.9913\pm 0.0008$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the beta-asymmetry has $0.2\%$ statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to $<0.1\%$, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.

   ↳ physics.atom-phnucl-exNew J.Phys.(2016)·18 citations
7. 07*

   Nuclear binding near a quantum phase transition

   Serdar Elhatisari🇩🇪 · Ning Li🇩🇪 · Alexander Rokash🇩🇪 · Jose Manuel Alarcón🇩🇪 · Dechuan Du🇩🇪 · Nico Klein🇩🇪 · Bing-nan Lu🇩🇪 · Ulf-G. Meißner🇩🇪 · Evgeny Epelbaum🇩🇪 · Hermann Krebs🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Gautam Rupak🇺🇸

   How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (4He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.

   ↳ nucl-thcond-mat.quant-gashep-latnucl-exPRL(2016)·123 citations
8. 08*

   Jet tomography in heavy-ion collisions -- Challenges, Results, and Open Problems

   Barbara Betz🇩🇪

   Over the past 30 years, jet observables have proven to provide important information about the quark-gluon plasma created in heavy-ion collisions. I review the challenges, results, and open problems of jet physics in heavy-ion collisions, discussing the main ideas as well as some most recent results focussing on two major jet observables, the nuclear modification factor and the high-pT elliptic flow.

   ↳ hep-phnucl-exnucl-th0 citations
9. 09*

   Applied Antineutrino Physics 2015 -- Conference Summary

   N. S. Bowden🇺🇸 · K. M. Heeger🇺🇸 · P. Huber🇺🇸 · C. Mariani🇺🇸 · R. B. Vogelaar🇺🇸

   This is a brief summary of the 11th Applied Antineutrino Physics 2015 workshop held at the Virginia Tech Arlington Research Facility from December 7-8, 2015.

   ↳ hep-exhep-phnucl-exphysics.ins-det8 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.