Wed·Dec 21, 2016Wednesday·December 21, 2016

1. 01*

   First measurement of proton's charge form factor at very low $Q^2$ with initial state radiation

   M. Mihovilovič🇸🇮 · A. B. Weber🇩🇪 · P. Achenbach🇩🇪 · T. Beranek🇩🇪 · J. Beričič🇸🇮 · J. C. Bernauer🇺🇸 · R. Böhm🇩🇪 · D. Bosnar🇭🇷 · M. Cardinali🇩🇪 · L. Correa🇫🇷 · L. Debenjak🇸🇮 · A. Denig🇩🇪 and 27 other authors

   We report on a new experimental method based on initial-state radiation (ISR) in e-p scattering, in which the radiative tail of the elastic e-p peak contains information on the proton charge form factor ($G_E^p$) at extremely small $Q^2$. The ISR technique was validated in a dedicated experiment using the spectrometers of the A1-Collaboration at the Mainz Microtron (MAMI). This provided first measurements of $G_E^p$ for $0.001\le Q^2\le 0.004(GeV/c{)}^2$.

   nucl-exhep-exPLB(2017)·69 citations
2. 02*

   Separation of the Charm and Beauty Production in p--Pb and Pb--Pb Collisions with ALICE

   Martin Völkl (for the ALICE Collaboration)🇩🇪

   Measurements of heavy (charm and beauty) quarks provide useful insights into the properties of the quark--gluon plasma. The good particle identification capabilities of ALICE make a measurement based on the electrons from semi-leptonic decays of heavy-flavour hadrons feasible. This approach makes use of the large branching ratios ($\approx 10-20\%$) of heavy--flavour hadrons into electrons. Separation of the contribution from beauty-hadron decay electrons was achieved by utilizing the large decay length of the associated hadrons, making the investigation of beauty quarks in the medium possible. By comparing measurements in p--Pb and Pb--Pb collisions, it is possible to disentangle effects of cold nuclear matter from those of the hot and dense medium. The results show a strong change in the transverse momentum distribution of electrons from beauty-hadron decays in central Pb--Pb collisions with respect to the proton--proton case. No significant change from proton--proton collisions can be seen in the p--Pb case, suggesting that the modification is a final state effect.

   nucl-exJ.Phys.Conf.Ser.(2017)·0 citations
3. 03*

   Effects of volume corrections and resonance decays on cumulants of net-charge distributions in a Monte Carlo hadron resonance gas model

   Hao-jie Xu🇨🇳

   The effects of volume corrections and resonance decays (the resulting correlations between positive charges and negative charges) on cumulants of net-proton distributions and net-charge distributions are investigated by using a Monte Carlo hadron resonance gas ({\tt MCHRG}) model. The required volume distributions are generated by a Monte Carlo Glauber ({\tt MC-Glb}) model. Except the variances of net-charge distributions, the {\tt MCHRG} model with more realistic simulations of volume corrections, resonance decays and acceptance cuts can reasonably explain the data of cumulants of net-proton distributions and net-charge distributions reported by the STAR collaboration. The {\tt MCHRG} calculations indicate that both the volume corrections and resonance decays make the cumulant products of net-charge distributions deviate from the Skellam expectations: the deviations of $S\sigma$ and $\kappa {\sigma }^2$ are dominated by the former effect while the deviations of $\omega$ are dominated by the latter one.

   ↳ nucl-thhep-phnucl-exPLB(2017)·25 citations
4. 04*

   Determining reactor fuel type from continuous antineutrino monitoring

   Patrick Jaffke🇺🇸 · Patrick Huber🇺🇸

   We investigate the ability of an antineutrino detector to determine the fuel type of a reactor. A hypothetical 5t antineutrino detector is placed 25m from the core and measures the spectral shape and rate of antineutrinos emitted by fission fragments in the core for a number of 90 day periods. Our results indicate that four major fuel types can be differentiated from the variation of fission fractions over the irradiation time with a true positive probability of detection at 95%. In addition, we demonstrate that antineutrinos can identify the burn-up at which weapons-grade mixed-oxide (MOX) fuel would be reduced to reactor-grade MOX on average, providing assurance that plutonium disposition goals are met. In addition, we investigate removal scenarios where plutonium is purposefully diverted from a mixture of MOX and low-enriched uranium (LEU) fuel. Finally, we discuss how our analysis is impacted by a spectral distortion around 6MeV observed in the antineutrino spectrum measured from commercial power reactors.

   ↳ physics.ins-dethep-exhep-phnucl-exPhys.Rev.Applied(2017)·17 citations
5. 05*

   Jet and heavy flavor production in heavy-ion collisions

   Zhong-Bo Kang🇺🇸 · Felix Ringer🇺🇸 · Ivan Vitev🇺🇸

   We review recent progress in the theoretical description of hard probes in heavy-ion collisions within the framework of Soft Collinear Effective Theory (SCET). Firstly, we consider the inclusive production of heavy flavor mesons and jets with a small radius parameter in proton-proton collisions. Secondly, we describe how in-medium effects can be incorporated consistently with the proton-proton baseline calculations. The in-medium interactions are described by Glauber gluon interactions. We present results for the nuclear modification factor $R_{AA}$ which is most commonly used to study the quenching of hadron or jet production yields in heavy-ion collisions and we compare to recent data from the LHC.

   ↳ hep-phnucl-exnucl-thNucl.Part.Phys.Proc.(2017)·0 citations
6. 06*

   Monopole transition strength function of ${}^{12}$C in three-$\alpha$ model

   Souichi Ishikawa

   The energy level structure of ${}^{12}$C nucleus at a few MeV above the three-$\alpha$ threshold is still unsatisfactory known. For instance, most microscopic calculations predicted that there exist one $0^{+}$-state in this energy region besides the well known Hoyle state, while some experimental and theoretical studies show the existing of two $0^{+}$-states. In this paper, I will take a three-$\alpha$-boson (3$\alpha$) model for bound and continuum states in ${}^{12}$C, and study a transition process from the ${}^{12}$C($0_1^{+}$) ground state to 3$\alpha$ $0^{+}$ continuum states by the electric monopole ($E0$) operator. The strength distribution of the process will be calculated as a function of $3\alpha$ energy using the Faddeev three-body theory. The Hamiltonian for the $3\alpha$ system consists of two- and three-$\alpha$ potentials, and some three-$\alpha$ potentials with different range parameters will be examined. Results of the strength function show a double-peaked bump at low energy region, which can be considered as two $0^{+}$-states. The peak at higher energy may originate from a 3$\alpha$ resonant state. However, it is unlikely that the peak at the lower energy is related to a resonant state, which suggests that it may be due to so called "ghost anomaly". Distributions of decaying particles are also calculated.

   ↳ nucl-thnucl-exPRC(2016)·4 citations
7. 07*

   Two-dimensional solid state gaseous detector based on ${}^{10}B$ layer for thermal and cold neutrons

   S Potashev · Yu Burmistrov · A Drachev · S Karaevsky · E Konobeevski · S Zuyev

   Two-dimensional solid state gaseous detector for thermal and cold neutrons is created. The detector has active area of 128 x 128 $m{m}^2$, ${}^{10}B$ neutron converter, and gas chamber with thin windows. The resistive charge-division readout is applied to determine the neutron position. The detector was tested using $W-Be$ photoneutron source at the Institute for Nuclear Research, Moscow. The detector efficiency is estimated as ~4% at neutron wavelength $\lambda =1.82\mathring{A}$ and 8% at $\lambda =8\mathring{A}$. The efficiency of the background detection was less than $10^{-5}$ of that for thermal neutrons. The resulting pulse height resolution and the spatial resolution are estimated as $\approx 15\%$ and $\approx 2.5mm$, respectively.

   ↳ physics.ins-detnucl-exJ.Phys.Conf.Ser.(2017)·2 citations
8. 08*

   ${\rm Y}$ production in p-Pb and Pb-Pb collisions with ALICE at the LHC

   Gabriele Gaetano Fronzé🇮🇹

   ALICE (A Large Ion Collider Experiment) is devoted to the study of heavy-ion collisions at LHC energies. In such collisions a deconfined state of nuclear matter, the Quark-Gluon Plasma (QGP), is formed. Due to their early production, quarkonium states are good probes to study the QGP evolution. Such states are affected by suppression mechanisms which lead to reduced yields with respect to pp and p-Pb collisions, while regeneration phenomena might lead to an enhancement of their production. The latter effects are expected to be negligible at LHC for bottomonium states. The recent ALICE results on ${\rm Y}$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{T}\mathrm{e}\mathrm{V}$ will be presented and compared with previous measurements at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{T}\mathrm{e}\mathrm{V}$. A comparison with theoretical calculations will be performed as well. Results obtained in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{T}\mathrm{e}\mathrm{V}$ will also be discussed.

   ↳ hep-exnucl-exNucl.Part.Phys.Proc.(2017)·8 citations
9. 09*

   Structure of the Energy-Momentum Tensor and Applications

   Jonathan Hudson (UConn)🇺🇸 · Irina A. Perevalova (Irkutsk State U.)🇷🇺 · Maxim V. Polyakov (St. Petersburg, INP & Ruhr U., Bochum)🇷🇺 · Peter Schweitzer (UConn)🇺🇸

   The probably most fundamental information about a particle is contained in the matrix elements of its energy momentum tensor (EMT) which are accessible from hard-exclusive reactions via generalized parton distribution functions. The spin decomposition of the nucleon and Ji sum rule are one example. Less prominent but equally important information is encoded in the stress tensor, related to the spatial components of the EMT, which shows in detail how the strong forces inside the nucleon balance to form a bound state. This provides not only unique insights on nucleon structure. It also leads to fascinating new applications to hadron spectroscopy which allow us to formulate new interpretations of the charmonium-nucleon pentaquarks discovered by LHCb. Recent progress is reviewed in this short overview article.

   ↳ hep-phhep-exnucl-exnucl-thPoS(2017)·8 citations
10. 10*

    Rapidity-dependent jet energy loss in small systems with finite-size effects and running coupling

    Chanwook Park🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    Longitudinal dynamics of particle production and rapidity-dependent jet energy loss are investigated in small and asymmetric colliding systems. We utilize an improved version of \textsc{martini} in which two improvements are implemented to calculate the effect of the strongly coupled QGP droplet on jet energy loss. We show that those realistic prescriptions improve the results of nuclear modification factor calculations. We also observe visible energy loss of jets in a thermal background of high-multiplicity p-Pb collisions, and a clear correlation between the energy loss and elliptic flow coefficients for energetic particles. We conclude that systematic measurements of jet quenching in central collisions of small systems can support the formation of the QGP droplet.

    ↳ nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2017)·23 citations
11. 11*

    Extracting $\hat{q}$ from single inclusive data at RHIC and at the LHC for different centralities: a new puzzle?

    Carlota Andres🇪🇸 · Nestor Amesto🇪🇸 · Matthew Luzum🇪🇸 · Carlos A. Salgado🇪🇸 · Pia Zurita🇺🇸

    We present here an extraction of the jet transport coefficient, $\hat{q}$, using RHIC and LHC single-inclusive high-$p_T$ data for different centralities. We fit a $K$-factor that determines the deviation of this coefficient from an ideal estimate, $K\equiv \hat{q}/(2{ϵ}^{3/4})$, where $ϵ$ is given by hydrodynamic simulations. As obtained already in previous studies, this $K$-factor is found to be larger at RHIC than at the LHC. However it is, unexpectedly, basically no-dependent on the centrality of the collision. Taken at face value this result, the $K$-factor would not depend on local properties of the QGP as temperature, but on global collision variables such as the center of mass energy.

    ↳ nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2017)·5 citations
12. 12*

    Angular decay coefficients of $J/\psi$ mesons at forward rapidity from $p+p$ collisions at $\sqrt{s}=510$ GeV

    A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · M. Alfred · V. Andrieux · K. Aoki · N. Apadula · Y. Aramaki · H. Asano · E.T. Atomssa and 379 other authors

    We report the first measurement of the full angular distribution for inclusive $J/\psi \to {\mu }^{+}{\mu }^{-}$ decays in $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV. The measurements are made for $J/\psi$ transverse momentum $2<p_T<10$ GeV/$c$ and rapidity $1.2<y<2.2$ in the Helicity, Collins-Soper, and Gottfried-Jackson reference frames. In all frames the polar coefficient ${\lambda }_{\theta }$ is strongly negative at low $p_T$ and becomes close to zero at high $p_T$, while the azimuthal coefficient ${\lambda }_{\varphi }$ is close to zero at low $p_T$, and becomes slightly negative at higher $p_T$. The frame-independent coefficient $\tilde{\lambda }$ is strongly negative at all $p_T$ in all frames. The data are compared to the theoretical predictions provided by nonrelativistic quantum chromodynamics models.

    ↳ hep-exnucl-exPRD(2017)·6 citations
13. 13*

    Machine learning and multivariate goodness of fit

    Constantin Weisser🇺🇸 · Mike Williams🇺🇸

    Multivariate goodness-of-fit and two-sample tests are important components of many nuclear and particle physics analyses. While a variety of powerful methods are available if the dimensionality of the feature space is small, such tests rapidly lose power as the dimensionality increases and the data inevitably become sparse. Machine learning classifiers are powerful tools capable of reducing highly multivariate problems into univariate ones, on which commonly used tests such as ${\chi }^2$ or Kolmogorov-Smirnov may be applied. We explore applying both traditional and machine-learning-based tests to several example problems, and study how the power of each approach depends on the dimensionality. A pedagogical discussion is provided on which types of problems are best suited to using traditional versus machine-learning-based tests, and on the how to properly employ the machine-learning-based approach.

    ↳ physics.data-anhep-exnucl-ex16 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.