Wed·Sep 23, 2015Wednesday·September 23, 2015

1. 01*

   $\varphi$ meson production in the forward/backward rapidity region in Cu$+$Au collisions at $\sqrt{s_{NN}}=200$ GeV

   A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · J. Alexander · M. Alfred · H. Al-Ta'ani · K.R. Andrews · A. Angerami · K. Aoki · N. Apadula and 501 other authors

   The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured $\varphi$ meson production and its nuclear modification in asymmetric Cu$+$Au heavy-ion collisions at $\sqrt{s_{NN}}=200$ GeV at both forward Cu-going direction ($1.2<y<2.2$) and backward Au-going direction ($-2.2<y<-1.2$), rapidities. The measurements are performed via the dimuon decay channel and reported as a function of the number of participating nucleons, rapidity, and transverse momentum. In the most central events, 0\%--20\% centrality, the $\varphi$ meson yield integrated over $1<p_T<5$ GeV/$c$ prefers a smaller value, which means a larger nuclear modification, in the Cu-going direction compared to the Au-going direction. Additionally, the nuclear-modification factor in Cu$+$Au collisions averaged over all centrality is measured to be similar to the previous PHENIX result in $d$$+$Au collisions for these rapidities.

   nucl-exPRC(2016)·22 citations
2. 02*

   Neutrons on a surface of liquid helium

   P. D. Grigoriev🇷🇺 · O. Zimmer🇫🇷 · T. Ziman · A. D. Grigoriev

   We investigate the possibility of ultracold neutron (UCN) storage in quantum states defined by the combined potentials of the Earth's gravity and the neutron optical repulsion by a horizontal surface of liquid helium. We analyse the stability of the lowest quantum state, which is most susceptible to perturbations due to surface excitations, against scattering by helium atoms in the vapor and by excitations of the liquid, comprised of ripplons, phonons and surfons. This is an unusual scattering problem since the kinetic energy of the neutron parallel to the surface may be much greater than the binding energies perpendicular. The total scattering time constant of these UCNs at 0.7 K is found to exceed one hour, and rapidly increasing with decreasing temperature. Such low scattering rates should enable high-precision measurements of the scheme of discrete energy levels, thus providing improved access to short-range gravity. The system might also be useful for neutron beta-decay experiments. We also sketch new experimental concepts for level population and trapping of UCNs above a flat horizontal mirror.

   nucl-excond-mat.othernucl-thPRC(2016)·6 citations
3. 03*

   Measurement of jpsi production in p+p collisions at \sqrts = 500 GeV at STAR experiment

   Rongrong Ma (on behalf of the STAR Collaboration)🇺🇸

   Quarkonium measurements in heavy-ion collisions play an essential role in understanding the hot, dense medium created in such collisions. As a reference, their production mechanism in p+p collisions needs to be thoroughly understood. In this paper, we report the measurement of inclusive cross section of jpsi with transverse momentum (pT) above 4 GeV/c at mid-rapidity in p+p collisions at \sqrts = 500 GeV by the STAR experiment. The ratio of the yield of psi(2S) to jpsi integrated over 4 < pT < 12 GeV/c is also presented. Furthermore, the jpsi yields are studied in different event multiplicity bins in different jpsi pT regions, where the low pT measurement is enabled by the newly installed Muon Telescope Detector. A strong increase of the relative jpsi yield with the event multiplicity is observed for all pT with significant pT dependence.

   nucl-exNucl.Part.Phys.Proc.(2016)·15 citations
4. 04*

   Self-similarity of negative particle production from the Beam Energy Scan Program at STAR

   M.V. Tokarev (on behalf of STAR Collaboration)🇷🇺

   We present the spectra of negative charged particle production in Au+Au collisions from STAR for the first phase of the RHIC Beam Energy Scan Program measured over a wide range of collision energy sqrt s{NN}=7.7-200 GeV, and transverse momentum of produced particle in different centralities at |eta|<0.5. The spectra demonstrate strong dependence on collision energy which enhances with pT. An indication of self-similarity of negative charged particle production in Au+Au collisions is found. The constituent energy loss as a function of energy and centrality of collisions and transverse momentum of inclusive particle was estimated in the $z$-scaling approach. The energy dependence of the model parameters - the fractal and fragmentation dimensions and "specific heat", was studied.

   nucl-exInt.J.Mod.Phys.Conf.Ser.(2015)·9 citations
5. 05*

   Results from Pion-Carbon Interactions Measured by NA61/SHINE for Improved Understanding of Extensive Air Showers

   Alexander E. Hervé (for the NA61 Collaboration)🇩🇪

   The interpretation of extensive air shower measurements, produced by ultra-high energy cosmic rays, relies on the correct modeling of the hadron-air interactions that occur during the shower development. The majority of hadronic particles are produced at equivalent beam energies below the TeV range. NA61/SHINE is a fixed target experiment using secondary beams produced at CERN at the SPS. Hadron-hadron interactions have been recorded at beam momenta between 13 and 350 GeV/c with a wide-acceptance spectrometer. In this contribution we present measurements of the spectra of charged pions and the ${\rho }^0$ production in pion-carbon interactions, which are essential for modeling of air showers.

   nucl-exastro-ph.HEPoS(2016)·18 citations
6. 06*

   Measurements of Branching Ratios for $\eta$ Decays into Charged Particles

   P. Adlarson🇸🇪 · W. Augustyniak🇵🇱 · W. Bardan🇵🇱 · M. Bashkanov🇩🇪 · F.S. Bergmann🇩🇪 · M. Berłowski🇵🇱 · H. Bhatt🇮🇳 · A. Bondar🇷🇺 · M. Büscher🇩🇪 · H. Calén🇸🇪 · I. Ciepał🇵🇱 · H. Clement🇩🇪 and 87 other authors

   The WASA-at-COSY experiment has collected $3\times 10^7$ events with $\eta$-mesons produced via the reaction $pd\to {}^3\text{He}\eta$ at $\text{T}=1.0\text{GeV}$. Using this data set, we evaluate the branching ratios of the decays $\eta \to {\pi }^{+}{\pi }^{-}\gamma$, $\eta \to e^{+}{e}^{-}\gamma$, $\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ and $\eta \to e^{+}{e}^{-}{e}^{+}{e}^{-}$. The branching ratios are normalized to the $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay. In addition an upper limit on a $CP$-violating asymmetry in $\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ is extracted.

   nucl-exPRC(2016)·28 citations
7. 07*

   Precision Electron-Beam Polarimetry using Compton Scattering at 1 GeV

   A. Narayan · D. Jones · J. C. Cornejo · M. M. Dalton · W. Deconinck · D. Dutta · D. Gaskell · J. W. Martin · K.D. Paschke · V. Tvaskis · A. Asaturyan · J. Benesch and 24 other authors

   We report on the highest precision yet achieved in the measurement of the polarization of a low energy, $\mathcal{O}$(1 GeV), electron beam, accomplished using a new polarimeter based on electron-photon scattering, in Hall~C at Jefferson Lab. A number of technical innovations were necessary, including a novel method for precise control of the laser polarization in a cavity and a novel diamond micro-strip detector which was able to capture most of the spectrum of scattered electrons. The data analysis technique exploited track finding, the high granularity of the detector and its large acceptance. The polarization of the $180\mu$A, $1.16$~GeV electron beam was measured with a statistical precision of $<$~1\% per hour and a systematic uncertainty of 0.59\%. This exceeds the level of precision required by the \qweak experiment, a measurement of the vector weak charge of the proton. Proposed future low-energy experiments require polarization uncertainty $<$~0.4\%, and this result represents an important demonstration of that possibility. This measurement is also the first use of diamond detectors for particle tracking in an experiment.

   nucl-exhep-phnucl-thphysics.acc-ph+1PRX(2016)·48 citations
8. 08*

   Are Electron Scattering Data Consistent with a Small Proton Radius?

   Keith Griffioen🇺🇸 · Carl Carlson🇺🇸 · Sarah Maddox🇺🇸

   We determine the charge radius of the proton by analyzing the published low momentum transfer electron-proton scattering data from Mainz. We note that polynomial expansions of the form factor converge for momentum transfers squared below $4m_{\pi }^2$, where $m_{\pi }$ is the pion mass. Expansions with enough terms to fit the data, but few enough not to overfit, yield proton radii smaller than the CODATA or Mainz values and in accord with the muonic atom results. We also comment on analyses using a wider range of data, and overall obtain a proton radius $R_E=0.840(16$) fm.

   nucl-exhep-phPRC(2016)·94 citations
9. 09*

   Photoproduction of the $f_2^{\prime }(1525)$ and $K_2^{\ast }(1430)$

   Ju-Jun Xie🇨🇳 · Eulogio Oset🇪🇸 · Li-Sheng Geng🇨🇳

   Assuming that the $f_2^{\prime }(1525)$ and $K_2^{\ast }(1430)$ resonances are dynamically generated states from the vector meson-vector meson interactions in $S$-wave with spin $S=2$, we study the $\gamma p\to f_2^{\prime }(1525)p$ and $\gamma p\to K_2^{\ast }(1430)\Lambda (\Sigma )$ reactions. These reactions proceed in the following way: the incoming photon first mutates into a ${\rho }^0$, $\omega$, or $\varphi$ meson via vector meson dominance, which then interacts with the ${\rho }^0$, $\omega$ or $K^{\ast }$ emitted by the incoming proton to form the tensor mesons $f_2^{\prime }(1525)$ and $K_2^{\ast }(1430)$. The picture is simple and has no free parameters, as all the parameters of the mechanism have been fixed in previous studies. We predict the differential and total cross sections of these reactions. The results can be tested in future experiments and therefore offer new clues on the nature of these tensor states.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·17 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.