Wed·Nov 26, 2014Wednesday·November 26, 2014

1. 01*

   Close to threshold eta' meson production in proton-proton collisions at COSY-11

   E. Czerwiński🇵🇱 · P. Moskal🇵🇱 · M. Silarski🇵🇱

   Intensive quest for the eta and eta' bound states is currently ongoing at both theoretical and experimental levels e.g. at COSY, ELSA, GSI, JINR, JPARC, LPI, and MAMI. These studies were already supported by data provided by the COSY-11 collaboration including determination of the total width of the eta' meson. In addition, the first rough estimation of the eta'-N interaction from the excitation function of the cross section for the pp-->pp eta' reaction was also performed. Recent precise measurement in this field from the COSY-11 experiment allows to summarize results on the eta' meson production cross section in proton-proton collisions at COSY-11.

   nucl-exEPJ Web Conf.(2014)·0 citations
2. 02*

   Recent KLOE results on kaon physics

   E. Czerwiński🇵🇱

   A short review of two measurements recently published by KLOE/KLOE-2 collaborations is presented. Namely the most stringent limits of the CPT-violating parameters Delta a_mu for neutral kaons, and the absolute branching ratio of K+ --> pi+pi-pi+(gamma) decay. In addition a discussion of starting KLOE-2 project is performed.

   nucl-exhep-exNucl.Part.Phys.Proc.(2016)·0 citations
3. 03*

   Observation of the "$K^{-}pp$"-like structure in the $d({\pi }^{+},K^{+})$ reaction at 1.69 GeV/$c$

   Yudai Ichikawa · Tomofumi Nagae🇯🇵 · Hiroyuki Fujioka🇯🇵 · Hyoungchan Bhang🇰🇷 · Stefania Bufalino🇮🇹 · Hiroyuki Ekawa🇯🇵 · Petr Evtoukhovitch🇷🇺 · Alessandro Feliciello🇮🇹 · Shoichi Hasegawa🇯🇵 · Shuhei Hayakawa · Ryotaro Honda🇯🇵 · Kenji Hosomi🇯🇵 and 32 other authors

   We have observed a "$K^{-}pp$"-like structure in the $d({\pi }^{+},K^{+})$ reaction at 1.69 GeV/$c$. In this reaction $\Lambda (1405)$ hyperon resonance is expected to be produced as a doorway to form the $K^{-}pp$ through the ${\Lambda }^{\ast }p\to K^{-}pp$ process. However, most of the produced $\Lambda (1405)$'s would escape from deuteron without secondary reactions. Therefore, coincidence of high-momentum ($>$ 250~MeV/$c$) proton(s) in large emission angles ($39^{\circ }<{\theta }_{lab.}<122^{\circ }$) was requested to enhance the signal-to-background ratio. A broad enhancement in the proton coincidence spectra are observed around the missing-mass of 2.27 GeV/$c^2$, which corresponds to the $K^{-}pp$ binding energy of 95 ${}_{-17}^{+18}$ (stat.) ${}_{-21}^{+30}$ (syst.) MeV and the width of 162 ${}_{-45}^{+87}$ (stat.) ${}_{-78}^{+66}$ (syst.) MeV.

   nucl-exPTEP(2015)·84 citations
4. 04*

   Towards a resolution of the proton form factor problem: new electron and positron scattering data

   D. Adikaram · D. Rimal · L.B. Weinstein · B. Raue · P. Khetarpal · R.P. Bennett · J. Arrington · W.K. Brooks · K.P. Adhikari · A.V. Afanasev · M.J. Amaryan · M.D. Anderson and 124 other authors

   There is a significant discrepancy between the values of the proton electric form factor, $G_E^p$, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of $G_E^p$ from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization ($\epsilon$) and momentum transfer ($Q^2$) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing $\epsilon$ at $Q^2=1.45{\text{ GeV}}^2$. This measurement is consistent with the size of the form factor discrepancy at $Q^2\approx 1.75$ GeV${}^2$ and with hadronic calculations including nucleon and $\Delta$ intermediate states, which have been shown to resolve the discrepancy up to $2-3$ GeV${}^2$.

   nucl-exPRL(2015)·113 citations
5. 05*

   Probing superfast quarks in nuclei through dijet production at the LHC

   Adam J. Freese🇺🇸 · Misak M. Sargsian🇺🇸 · Mark I. Strikman🇺🇸

   We investigate dijet production from proton-nucleus collisions at the Large Hadron Collider (LHC) as a means for observing superfast quarks in nuclei with Bjorken $x>1$. Kinematically, superfast quarks can be identified through directly measurable jet kinematics. Dynamically, their description requires understanding several elusive properties of nuclear QCD, such as nuclear forces at very short distances, as well as medium modification of parton distributions in nuclei. In the present work, we develop a model for nuclear parton distributions at large $x$ in which the nuclear dynamics at short distance scales are described by two- and three-nucleon short range correlations (SRCs). Nuclear modifications are accounted for using the color screening model, and an improved description of the EMC effect is reached by using a structure function parametrization that includes higher-twist contributions. We apply QCD evolution at the leading order to obtain nuclear parton distributions in the kinematic regime of the LHC, and based on the obtained distributions calculate the cross section for dijet production. We find not only that superfast quarks can be observed at the LHC, but also that they provide sensitivity to the practically unexplored three-nucleon SRCs in nuclei. Additionally, the LHC can extend our knowledge of the EMC effect to large $Q^2$ where higher-twist effects are negligible.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2015)·19 citations
6. 06*

   Femtoscopy with identified hadrons in pp, pPb, and peripheral PbPb collisions in CMS

   Ferenc Siklér (for the CMS Collaboration)🇭🇺

   Short range correlations of identified charged hadrons in pp (sqrt(s) = 0.9, 2.76, and 7 TeV), pPb (sqrt(sNN) = 5.02 TeV), and peripheral PbPb collisions (sqrt(sNN) = 2.76 TeV) are studied with the CMS detector at the LHC. Charged pions, kaons, and protons at low pT and in laboratory pseudorapidity |eta| < 1 are identified via their energy loss in the silicon tracker. The two-particle correlation functions show effects of quantum statistics, Coulomb interaction, and also indicate the role of multi-body resonance decays and mini-jets. The characteristics of the one-, two-, and three-dimensional correlation functions are studied as a function of pair momentum and the charged-particle multiplicity of the event. The extracted radii are in the range 1-5 fm, reaching highest values for very high multiplicity pPb, also for similar multiplicity PbPb collisions, and decrease with increasing kT. The dependence of radii on multiplicity and kT largely factorizes and appears to be insensitive to the type of the colliding system and center-of-mass energy.

   ↳ hep-exnucl-ex3 citations
7. 07*

   Sketching the pion's valence-quark generalised parton distribution

   C. Mezrag🇫🇷 · L. Chang🇦🇺 · H. Moutarde🇫🇷 · C. D. Roberts🇺🇸 · J. Rodriguez-Quintero🇪🇸 · F. Sabatie🇫🇷 · S. M. Schmidt🇩🇪

   In order to learn effectively from measurements of generalised parton distributions (GPDs), it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD, $H_{\pi }^{\mathrm{v}}(x,\xi ,t)$. Our analysis focuses primarily on $\xi =0$, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting $H_{\pi }^{\mathrm{v}}(x,\xi =\pm 1,t)$ with the pion's valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for $H_{\pi }^{\mathrm{v}}(x,0,t)$, expressed as the Radon transform of a single amplitude. Therewith we obtain results for $H_{\pi }^{\mathrm{v}}(x,0,t)$ and the associated impact-parameter dependent distribution, $q_{\pi }^{\mathrm{v}}(x,|{\vec{b}}_{\perp }|)$, which provide a qualitatively sound picture of the pion's dressed-quark structure at an hadronic scale. We evolve the distributions to a scale $\zeta =2$GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.

   ↳ nucl-thhep-lathep-phnucl-exPLB(2015)·83 citations
8. 08*

   Progress in developing a spiral fiber tracker for the J-PARC E36 experiment

   Makoto Tabata🇯🇵 · Keito Horie🇯🇵 · Youichi Igarashi🇯🇵 · Jun Imazato🇯🇵 · Hiroshi Ito🇯🇵 · Alexander Ivashkin🇷🇺 · Hideyuki Kawai🇯🇵 · Yury Kudenko🇷🇺 · Oleg Mineev🇷🇺 · Suguru Shimizu🇯🇵 · Akihisa Toyoda🇯🇵 · Hirohito Yamazaki🇯🇵

   This paper reports the recent progress made in developing a spiral fiber tracker (SFT) for use in the E36 experiment scheduled at the Japan Proton Accelerator Research Complex (J-PARC). The primary goal of this positive kaon decay experiment, which uses a stopped kaon beam, is to test lepton flavor universality to search for physics beyond the Standard Model of particle physics. For this experiment, we are currently upgrading the E246 apparatus, which consists of the superconducting toroidal spectrometer previously used at the High Energy Accelerator Research Organization (KEK), Japan. Conducting high-precision measurements will rely on efficiently detecting and tracking charged particles (i.e., positive muons and positrons) from kaon decays. Combined with the three existing layers of multiwire proportional chambers, the SFT comprises four layers of ribbons, with each layer containing 1-mm-diameter double-clad plastic scintillating fibers; the ribbons are spirally wound in two helicities around the kaon stopping target at the center of the detector system. Scintillation photons are read out by multipixel photon counters connected to the scintillating fibers by clear optical fiber extensions. A preliminary bench test shows that a prototype two-layer fiber ribbon exhibits 99.6% detection efficiency at the 1-photoelectron threshold. Finally, the SFT was successfully assembled around the target holder.

   ↳ physics.ins-dethep-exnucl-exPoS(2014)·1 citation
9. 09*

   Thick-target yields of radioactive targets deduced from inverse kinematics

   Masayuki Aikawa · Shuichiro Ebata🇯🇵 · Shotaro Imai🇯🇵

   The thick-target yield (TTY) is a macroscopic quantity reflected by nuclear reactions and matter properties of targets. In order to evaluate TTYs on radioactive targets, we suggest a conversion method from inverse kinematics corresponding to the reaction of radioactive beams on stable targets. The method to deduce the TTY is theoretically derived from inverse kinematics. We apply the method to the natCu(12C,X)24Na reaction to confirm availability. In addition, it is applied to the 137Cs + 12C reaction as an example of a radioactive system and discussed a conversion coefficient of a TTY measurement.

   ↳ nucl-thnucl-exNucl.Instrum.Meth.B(2015)·4 citations
10. 10*

    Hidden pseudospin and spin symmetries and their origins in atomic nuclei

    Haozhao Liang🇯🇵 · Jie Meng🇨🇳 · Shan-Gui Zhou🇨🇳

    Symmetry plays a fundamental role in physics. The quasi-degeneracy between single-particle orbitals $(n,l,j=l+1/2)$ and $(n-1,l+2,j=l+3/2)$ indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry (PSS). Since the introduction of the concept of PSS in atomic nuclei, there have been comprehensive efforts to understand its origin. Both splittings of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with radioactive ion beam facilities. Since the PSS was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry (SS) for anti-nucleon, and many new concepts have been introduced. In the present Review, we focus on the recent progress on the PSS and SS in various systems and potentials, including extensions of the PSS study from stable to exotic nuclei, from non-confining to confining potentials, from local to non-local potentials, from central to tensor potentials, from bound to resonant states, from nucleon to anti-nucleon spectra, from nucleon to hyperon spectra, and from spherical to deformed nuclei. Open issues in this field are also discussed in detail, including the perturbative nature, the supersymmetric representation with similarity renormalization group, and the puzzle of intruder states.

    ↳ nucl-thnucl-exphysics.atom-phquant-phPhys.Rept.(2015)·293 citations
11. 11*

    On the collectivity of Pygmy Dipole Resonance within schematic TDA and RPA models

    V. Baran · D.I. Palade · M. Colonna🇮🇹 · M. Di Toro · A. Croitoru · A.I. Nicolin

    Within schematic models based on the Tamm-Dancoff Approximation and the Random-Phase Approximation with separable interactions, we investigate the physical conditions which determine the emergence of the Pygmy Dipole Resonance in the E1 response of atomic nuclei. We find that if some particle-hole excitation manifests a different, weaker residual interaction, an additional mode will appear, with an energy centroid closer to the distance between two major shells and therefore well below the Giant Dipole Resonance. This state, together with Giant Dipole Resonance, exhausts all the transition strength in the Tamm-Dancoff Approximation and all the Energy Weighted Sum Rule in the Random-Phase Approximation. Thus, within our scheme, this mode, which could be associated with the Pygmy Dipole Resonance, is of collective nature. By relating the coupling constants appearing in the separable interaction to the symmetry energy value at and below saturation density we explore the role of the density dependence of the symmetry energy on the low energy dipole response.

    ↳ nucl-thnucl-ex1 citation

* 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.