http://prc.aps.org/ Physical Review C Editor Selections (a selection of abstracts from the physics journals of the American Physical Society) en-us Copyright (c) 2008 The American Physical Society 2008-05-09T09:36:09-04:00 assocpub@aps.org rss@aps.org hourly 4 2008-05-09T09:36:09-04:00 rss@aps.org http://link.aps.org/doi/10.1103/PhysRevD.77.094005 Author(s): Xiao-Hai Liu, Qiang Zhao, and Frank E. Close<br/>We propose a search for the newly discovered tetraquark candidate Z(4430) in photoproduction. Based on the Belle results, we show that if Z(4430) is a genuine resonance, its significantly large coupling to ψ^{′} π will cause it to stand out above the background in γp→Z^{+} (4430)n→ψ^{′} π^{+} n. We consider the dependence of the cross section for the quantum numbers (J^{P} =1^{-} , 1^{+} , or 0^{-} ).<br/>[Phys. Rev. D 77, 094005] Published Thu May 08, 2008 Xiao-Hai Liu, Qiang Zhao, and Frank E. Close 2008-05-08T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.094005 Phys. Rev. D 77, 094005 text/html article Physical Review D 77 9 2008-05-08T00:00:00-04:00 094005 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.181803 Author(s): Bin Gong and Jian-Xiong Wang<br/>Next-to-leading-order (NLO) QCD corrections to double J/ψ production in e^{+} e^{-} annihilation at sqrt[s] =10.6  GeV are calculated. We find that they greatly decrease the cross section, with a K factor (NLO/LO) ranging from -0.31 to 0.25 depending on the renormalization scale. Although the renormalization scale dependence indicates a large uncertainty, when combined with the NLO QCD corrections to J/ψ+η_{c} production, it can explain why the double J/ψ production could not be found at B factories while the J/ψ+η_{c} production could, despite the fact that cross section of the former is larger than that of the latter at LO by a factor of 1.8.<br/>[Phys. Rev. Lett. 100, 181803] Published Wed May 07, 2008 Bin Gong and Jian-Xiong Wang 2008-05-07T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.181803 Phys. Rev. Lett. 100, 181803 text/html article Physical Review Letters 100 18 2008-05-07T00:00:00-04:00 181803 Elementary Particles and Fields Elementary Particles and Fields http://link.aps.org/doi/10.1103/PhysRevD.77.093002 Author(s): Carlo Giunti and Marco Laveder<br/>The anomalous excess of low-energy ν_{e} events measured in the MiniBooNE experiment is explained through a renormalization of the absolute neutrino flux and a simultaneous disappearance of the ν_{e} ’s in the beam, which is compatible with that indicated by the results of gallium radioactive source experiments. We present the results of the fit of MiniBooNE data (P_{ν_{e} →ν_{e} } =0.64_{-0.07}^{+0.08} ) and the combined fit of MiniBooNE data and the ν_{e} disappearance measured in the gallium radioactive source experiments, which gives P_{ν_{e} →ν_{e} } =0.82±0.04. We show that our interpretation of the data is also compatible with an old indication in favor of ν_{e} disappearance found from the analysis of the results of beam-dump experiments, leading to P_{ν_{e} →ν_{e} } =0.80_{-0.04}^{+0.03} .<br/>[Phys. Rev. D 77, 093002] Published Wed May 07, 2008 Carlo Giunti and Marco Laveder 2008-05-07T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.093002 Phys. Rev. D 77, 093002 text/html article Physical Review D 77 9 2008-05-07T00:00:00-04:00 093002 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.182501 Author(s): C. Bachelet, G. Audi, C. Gaulard, C. Guénaut, F. Herfurth, D. Lunney, M. de Saint Simon, and C. Thibault<br/>The extended radius of a halo nuclide is very sensitive to the minute binding energy of its valence nucleons. The binding energy of ^{11} Li has been measured with high precision by using the radio-frequency spectrometer MISTRAL at CERN’s ISOLDE facility. The new two-neutron separation energy of 378±5  keV is 25% higher than the previously accepted value with an uncertainty 5 times smaller.<br/>[Phys. Rev. Lett. 100, 182501] Published Tue May 06, 2008 C. Bachelet, G. Audi, C. Gaulard, C. Guénaut, F. Herfurth, D. Lunney, M. de Saint Simon, and C. Thibault 2008-05-06T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.182501 Phys. Rev. Lett. 100, 182501 text/html article Physical Review Letters 100 18 2008-05-06T00:00:00-04:00 182501 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevD.77.094004 Author(s): Amir H. Fariborz, Renata Jora, and Joseph Schechter<br/>It is well known that the instanton approach to QCD generates an effective term which looks like a three-flavor determinant of quark bilinears. This has the right behavior to explain the unusual mass and mixing of the η(958) meson, as is often simply illustrated with the aid of a linear SU(3) sigma model. It is less well known that the instanton analysis generates another term which has the same transformation property but does not have a simple interpretation in terms of this usual linear sigma model. Here we point out that this term has an interpretation in a generalized linear sigma model containing two chiral nonets. The second chiral nonet is taken to correspond to mesons having two quarks and two antiquarks in their makeup. The generalized model seems to be useful for learning about the spectrum of low-lying scalar mesons which have been emerging in the last few years. The physics of the new term is shown to be related to the properties of an excited η^{′} state present in the generalized model and for which there are some experimental candidates.<br/>[Phys. Rev. D 77, 094004] Published Tue May 06, 2008 Amir H. Fariborz, Renata Jora, and Joseph Schechter 2008-05-06T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.094004 Phys. Rev. D 77, 094004 text/html article Physical Review D 77 9 2008-05-06T00:00:00-04:00 094004 D1 D1 http://link.aps.org/doi/10.1103/PhysRevD.77.094502 Author(s): Ph. Hägler, W. Schroers, J. Bratt, J. W. Negele, A. V. Pochinsky, R. G. Edwards, D. G. Richards, M. Engelhardt, G. T. Fleming, B. Musch, K. Orginos, and D. B. Renner LHPC Collaboration<br/>We present a comprehensive study of the lowest moments of nucleon generalized parton distributions in N_{f} =2+1 lattice QCD using domain-wall valence quarks and improved staggered sea quarks. Our investigation includes helicity dependent and independent generalized parton distributions for pion masses as low as 350 MeV and volumes as large as (3.5  fm)^{3} , for a lattice spacing of 0.124 fm. We use perturbative renormalization at one-loop level with an improvement based on the nonperturbative renormalization factor for the axial vector current, and only connected diagrams are included in the isosinglet channel.<br/>[Phys. Rev. D 77, 094502] Published Tue May 06, 2008 Ph. Hägler, W. Schroers, J. Bratt, J. W. Negele, A. V. Pochinsky, R. G. Edwards, D. G. Richards, M. Engelhardt, G. T. Fleming, B. Musch, K. Orginos, and D. B. Renner LHPC Collaboration 2008-05-06T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.094502 Phys. Rev. D 77, 094502 text/html article Physical Review D 77 9 2008-05-06T00:00:00-04:00 094502 D1 D1 http://link.aps.org/doi/10.1103/PhysRevD.77.091501 Author(s): D. J. Cecile and Shailesh Chandrasekharan<br/>The dimensionless parameter ξ=M_{π}^{2} /(16π^{2} F_{π}^{2} ), where F_{π} is the pion decay constant and M_{π} is the pion mass, is expected to control the convergence of chiral perturbation theory applicable to QCD. Here we demonstrate that a strongly coupled lattice gauge theory model with the same symmetries as two-flavor QCD but with a much lighter σ-resonance is different. We first confirm that the leading low-energy constants appearing in the chiral Lagrangian are the same when calculated from the p-regime and the ϵ-regime as expected. However, ξ≲0.002 is necessary before 1-loop chiral perturbation theory predicts the data within 1%. For ξ>0.0035 the data begin to deviate dramatically from 1-loop chiral perturbation theory predictions. We argue that this qualitative change is due to the presence of a light σ-resonance in our model. Our findings may be useful for lattice QCD studies.<br/><img src="http://prola.aps.org/graphics/rapid30x30.gif" width="30" height="30" alt="Rapid Communication"/><br/>[Phys. Rev. D 77, 091501] Published Mon May 05, 2008 D. J. Cecile and Shailesh Chandrasekharan 2008-05-05T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.091501 Phys. Rev. D 77, 091501 text/html article Physical Review D 77 9 2008-05-05T00:00:00-04:00 091501 D1 D1 http://link.aps.org/doi/10.1103/PhysRevD.77.094003 Author(s): Martin M. Block, Loyal Durand, and Douglas W. McKay<br/>We derive a second-order linear differential equation for the leading-order gluon distribution function G(x,Q^{2} )=xg(x,Q^{2} ) which determines G(x,Q^{2} ) directly from the proton structure function F_{2}^{p} (x,Q^{2} ). This equation is derived from the leading-order evolution equation for F_{2}^{p} (x,Q^{2} ), and does not require knowledge of either the individual quark distributions or the gluon evolution equation. Given an analytic expression that successfully reproduces the known experimental data for F_{2}^{p} (x,Q^{2} ) in a domain x_{min⁡} (Q^{2} )≤x≤x_{max⁡} (Q^{2} ), Q_{min⁡}^{2} ≤Q^{2} ≤Q_{max⁡}^{2} of the Bjorken variable x and the virtuality Q^{2} in deep inelastic scattering, G(x,Q^{2} ) is uniquely determined in the same domain. We give the general solution and illustrate the method using the recently proposed Froissart-bound-type parametrization of F_{2}^{p} (x,Q^{2} ) of E. L. Berger, M. M. Block and C.-I. Tan [Phys. Rev. Lett. 98, 242001 (2007)]. Existing leading-order gluon distributions based on power-law descriptions of individual parton distributions agree roughly with the new distributions for x≳10^{-3} as they should, but are much larger for x≲10^{-3} .<br/>[Phys. Rev. D 77, 094003] Published Mon May 05, 2008 Martin M. Block, Loyal Durand, and Douglas W. McKay 2008-05-05T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.094003 Phys. Rev. D 77, 094003 text/html article Physical Review D 77 9 2008-05-05T00:00:00-04:00 094003 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.172502 Author(s): E. Gomez, S. Aubin, L. A. Orozco, G. D. Sprouse, E. Iskrenova-Tchoukova, and M. S. Safronova<br/>We measure the hyperfine splitting of the 9S_{1/2} level of ^{210} Fr, and find a magnetic dipole hyperfine constant A=622.25(36)  MHz. The theoretical value, obtained using the relativistic all-order method from the electronic wave function at the nucleus, allows us to extract a nuclear magnetic moment of 4.38(5)μ_{N} for this isotope, which represents a factor of 2 improvement in precision over previous measurements. The same method can be applied to other rare isotopes and elements.<br/>[Phys. Rev. Lett. 100, 172502] Published Fri May 02, 2008 E. Gomez, S. Aubin, L. A. Orozco, G. D. Sprouse, E. Iskrenova-Tchoukova, and M. S. Safronova 2008-05-02T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.172502 Phys. Rev. Lett. 100, 172502 text/html article Physical Review Letters 100 17 2008-05-02T00:00:00-04:00 172502 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevD.77.085030 Author(s): Youngman Kim, Chang-Hwan Lee, and Ho-Ung Yee<br/>We study the physics at finite nuclear density in the framework of the AdS/QCD model with a holographic baryon field included. Based on a mean field type approach, we introduce the nucleon density as a bi-fermion condensate of the lowest mode of the baryon field and calculate the density dependence of the chiral condensate and the nucleon mass. We observe that the chiral condensate as well as the mass of nucleon decrease with increasing nuclear density. The resulting density dependence is, however, much weaker than those obtained in earlier studies based on other QCD effective theories. We also consider the mass splitting of charged vector mesons in isospin asymmetric nuclear matter.<br/>[Phys. Rev. D 77, 085030] Published Wed Apr 30, 2008 Youngman Kim, Chang-Hwan Lee, and Ho-Ung Yee 2008-04-30T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.085030 Phys. Rev. D 77, 085030 text/html article Physical Review D 77 8 2008-04-30T00:00:00-04:00 085030 D15 D15 http://link.aps.org/doi/10.1103/PhysRevLett.100.172301 Author(s): Zhe Xu and Carsten Greiner<br/>The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio η/s for a gluon gas, which involves elastic gg→gg perturbative QCD (PQCD) scatterings as well as inelastic gg↔ggg PQCD bremsstrahlung. For α_{s} =0.3 we find η/s=0.13 and for α_{s} =0.6, η/s=0.076. The small η/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.<br/>[Phys. Rev. Lett. 100, 172301] Published Tue Apr 29, 2008 Zhe Xu and Carsten Greiner 2008-04-29T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.172301 Phys. Rev. Lett. 100, 172301 text/html article Physical Review Letters 100 17 2008-04-29T00:00:00-04:00 172301 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevD.77.074022 Author(s): Carlo Ewerz, Andreas von Manteuffel, and Otto Nachtmann<br/>We derive correlated bounds on ratios of deep inelastic structure functions from the dipole picture of photon-hadron scattering at high energies. In particular we consider ratios of the longitudinal structure function, the total structure function, and the charm part of the latter. We also consider ratios of total structure functions taken at the same energy but at three different photon virtualities. It is shown that by confronting these bounds with experimental data we can significantly constrain the range of validity of the dipole picture.<br/>[Phys. Rev. D 77, 074022] Published Tue Apr 29, 2008 Carlo Ewerz, Andreas von Manteuffel, and Otto Nachtmann 2008-04-29T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.074022 Phys. Rev. D 77, 074022 text/html article Physical Review D 77 7 2008-04-29T00:00:00-04:00 074022 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.171602 Author(s): T. Yamazaki, Y. Aoki, T. Blum, H. W. Lin, M. F. Lin, S. Ohta, S. Sasaki, R. J. Tweedie, and J. M. Zanotti RBC+UKQCD Collaborations<br/>We present results for the nucleon axial charge g_{A} at a fixed lattice spacing of 1/a=1.73(3)  GeV using 2+1 flavors of domain wall fermions on size 16^{3} ×32 and 24^{3} ×64 lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of the Monte Carlo trajectory at the lightest m_{π} is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at m_{π} =330  MeV. We also find a scaling with the single variable m_{π} L which can also be seen in previous two-flavor domain wall and Wilson fermion calculations. Using this scaling to eliminate the finite-volume effect, we obtain g_{A} =1.20(6)(4) at the physical pion mass, m_{π} =135  MeV, where the first and second errors are statistical and systematic. The observed finite-volume scaling also appears in similar quenched simulations, but disappear when V≥(2.4  fm)^{3} . We argue this is a dynamical quark effect.<br/>[Phys. Rev. Lett. 100, 171602] Published Mon Apr 28, 2008 T. Yamazaki, Y. Aoki, T. Blum, H. W. Lin, M. F. Lin, S. Ohta, S. Sasaki, R. J. Tweedie, and J. M. Zanotti RBC+UKQCD Collaborations 2008-04-28T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.171602 Phys. Rev. Lett. 100, 171602 text/html article Physical Review Letters 100 17 2008-04-28T00:00:00-04:00 171602 Elementary Particles and Fields Elementary Particles and Fields http://link.aps.org/doi/10.1103/PhysRevLett.100.172501 Author(s): N. Ryezayeva, H. Arenhövel, O. Burda, A. Byelikov, M. Chernykh, J. Enders, H. W. Grießhammer, Y. Kalmykov, P. von Neumann-Cosel, B. Özel, I. Poltoratska, I. Pysmenetska, C. Rangacharyulu, S. Rathi, A. Richter, G. Schrieder, A. Shevchenko, and O. Yevetska<br/>Inclusive inelastic electron scattering off the deuteron under 180° has been studied at the S-DALINAC close to the breakup threshold at momentum transfers q=0.27  fm^{-1} and 0.74  fm^{-1} with good energy resolution sufficient to map in detail the spin flip M1 response, which governs the starting reaction pn→dγ of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for q=0.27  fm^{-1} ) from pionless nuclear effective field theory are in excellent agreement with the data.<br/>[Phys. Rev. Lett. 100, 172501] Published Mon Apr 28, 2008 N. Ryezayeva, H. Arenhövel, O. Burda, A. Byelikov, M. Chernykh, J. Enders, H. W. Grießhammer, Y. Kalmykov, P. von Neumann-Cosel, B. Özel, I. Poltoratska, I. Pysmenetska, C. Rangacharyulu, S. Rathi, A. Richter, G. Schrieder, A. Shevchenko, and O. Yevetska 2008-04-28T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.172501 Phys. Rev. Lett. 100, 172501 text/html article Physical Review Letters 100 17 2008-04-28T00:00:00-04:00 172501 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevD.77.074021 Author(s): Gorazd Cvetič and Cristián Valenzuela<br/>We present a specific class of models for an infrared-finite analytic QCD coupling, such that at large spacelike energy scales the coupling differs from the perturbative one by less than any inverse power of the energy scale. This condition is motivated by the Institute for Theoretical and Experimental Physics operator product expansion philosophy. Allowed by the ambiguity in the analytization of the perturbative coupling, the proposed class of couplings has three parameters. In the intermediate energy region, the proposed coupling has low loop-level and renormalization scheme dependence. The present modification of perturbative QCD must be considered as a phenomenological attempt, with the aim of enlarging the applicability range of the theory of the strong interactions at low energies.<br/>[Phys. Rev. D 77, 074021] Published Mon Apr 28, 2008 Gorazd Cvetič and Cristián Valenzuela 2008-04-28T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.074021 Phys. Rev. D 77, 074021 text/html article Physical Review D 77 7 2008-04-28T00:00:00-04:00 074021 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.162003 Author(s): Nick Evans and Andrew Tedder<br/>We study hadronization of the final state in a particle-antiparticle annihilation using a holographic gravity dual description of QCD. At the point of hadronization we match the events to a simple (Gaussian) energy distribution in the five dimensional theory. The final state multiplicities are then modeled by calculating the overlap between the Gaussian and a set of functions in the fifth dimension which represent each hadron. We compare our results to those measured in e^{+} e^{-} collisions. Hadron production numbers over a range of 4 orders of magnitude are reproduced well.<br/>[Phys. Rev. Lett. 100, 162003] Published Fri Apr 25, 2008 Nick Evans and Andrew Tedder 2008-04-25T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162003 Phys. Rev. Lett. 100, 162003 text/html article Physical Review Letters 100 16 2008-04-25T00:00:00-04:00 162003 Elementary Particles and Fields Elementary Particles and Fields http://link.aps.org/doi/10.1103/PhysRevLett.100.162503 Author(s): M. Alvioli, C. Ciofi degli Atti, and H. Morita<br/>A detailed analysis of the effect of short-range and tensor correlations on one- and two-nucleon momentum distributions of medium-weight nuclei (12≤A≤40) is carried out. Although our Letter is primarily aimed at understanding the role of the tensor force on nucleon momentum distributions of medium-weight nuclei, the possible relevance of our results for the interpretation of (e,e^{′} N) and (e,e^{′} 2N) processes at high Q^{2} , aimed at investigating nucleon-nucleon correlations, is discussed.<br/>[Phys. Rev. Lett. 100, 162503] Published Fri Apr 25, 2008 M. Alvioli, C. Ciofi degli Atti, and H. Morita 2008-04-25T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162503 Phys. Rev. Lett. 100, 162503 text/html article Physical Review Letters 100 16 2008-04-25T00:00:00-04:00 162503 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevD.77.074018 Author(s): H. Abuki, M. Ciminale, R. Gatto, G. Nardulli, and M. Ruggieri<br/>We study how the charge neutrality affects the phase structure of the three-flavor Polyakov-loop Nambu–Jona-Lasinio (PNJL) model. We point out that, within the conventional PNJL model at finite density, the color neutrality is missing because the Wilson line serves as an external colored field coupled to dynamical quarks. In this paper we heuristically assume that the model may still be applicable. To get color neutrality, one has then to allow nonvanishing color chemical potentials. We study how the quark matter phase diagram in (T,m_{s}^{2} /μ)-plane is affected by imposing neutrality and by including the Polyakov-loop dynamics. Although these two effects are correlated in a nonlinear way, the impact of the Polyakov loop turns out to be significant in the T direction, while imposing neutrality brings a remarkable effect in the m_{s}^{2} /μ direction. In particular, we find a novel unlocking transition, when the temperature is increased, even in the chiral SU(3) limit. We clarify how and why this is possible once the dynamics of the colored Polyakov loop is taken into account. Also we succeed in giving an analytic expression for T_{c} for the transition from two-flavor pairing (2SC) to unpaired quark matter in the presence of the Polyakov loop.<br/>[Phys. Rev. D 77, 074018] Published Fri Apr 25, 2008 H. Abuki, M. Ciminale, R. Gatto, G. Nardulli, and M. Ruggieri 2008-04-25T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.074018 Phys. Rev. D 77, 074018 text/html article Physical Review D 77 7 2008-04-25T00:00:00-04:00 074018 D1 D1 http://link.aps.org/doi/10.1103/PhysRevD.77.085022 Author(s): G. F. Burgio and S. Plumari<br/>We investigate the structure of protoneutron stars (PNS) formed by hadronic and quark matter in β-equilibrium described by appropriate equations of state (EOS). For the hadronic matter, we use a finite temperature EOS based on the Brueckner-Bethe-Goldstone many-body theory, with realistic two- and three-body forces. For the quark sector, we employ the Nambu–Jona-Lasinio model. We find that the allowed maximum masses are comprised in a narrow range around 1.8 solar masses, with a slight dependence on the temperature. Metastable hybrid protoneutron stars are not found.<br/>[Phys. Rev. D 77, 085022] Published Fri Apr 25, 2008 G. F. Burgio and S. Plumari 2008-04-25T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.085022 Phys. Rev. D 77, 085022 text/html article Physical Review D 77 8 2008-04-25T00:00:00-04:00 085022 D15 D15 http://link.aps.org/doi/10.1103/PhysRevLett.100.162502 Author(s): H. Utsunomiya, S. Goriely, T. Kondo, T. Kaihori, A. Makinaga, S. Goko, H. Akimune, T. Yamagata, H. Toyokawa, T. Matsumoto, H. Harano, S. Hohara, Y.-W. Lui, S. Hilaire, S. Péru, and A. J. Koning<br/>Photoneutron cross sections were measured for ^{91} Zr, ^{92} Zr, and ^{94} Zr near the neutron separation energy with quasimonochromatic γ rays. The data exhibit some extra components around the neutron threshold. A coherent analysis of the photoneutron data for ^{92} Zr together with the neutron capture on ^{91} Zr based on the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation model for the E1 strength has revealed the presence of an M1 resonance at 9 MeV. The microscopic approach systematically shows the same M1 strength in the photoneutron cross section for ^{91} Zr and ^{94} Zr. The total M1 strength is about 75% larger than the strength predicted by the systematics, being qualitatively consistent with the giant M1 resonance observed in the inelastic proton scattering.<br/>[Phys. Rev. Lett. 100, 162502] Published Thu Apr 24, 2008 H. Utsunomiya, S. Goriely, T. Kondo, T. Kaihori, A. Makinaga, S. Goko, H. Akimune, T. Yamagata, H. Toyokawa, T. Matsumoto, H. Harano, S. Hohara, Y.-W. Lui, S. Hilaire, S. Péru, and A. J. Koning 2008-04-24T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162502 Phys. Rev. Lett. 100, 162502 text/html article Physical Review Letters 100 16 2008-04-24T00:00:00-04:00 162502 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevLett.100.162001 Author(s): Harvey B. Meyer<br/>We perform a lattice Monte Carlo calculation of the trace-anomaly two-point function at finite temperature in the SU(3) gauge theory. We obtain the long distance properties of the correlator in the continuum limit and extract the bulk viscosity ζ via a Kubo formula. Unlike the tensor correlator relevant to the shear viscosity, the scalar correlator depends strongly on temperature. If s is the entropy density, we find that ζ/s becomes rapidly small at high T, ζ/s<0.15 at 1.65T_{c} , and ζ/s<0.015 at 3.2T_{c} . However, ζ/s rises dramatically just above T_{c} , with 0.5<ζ/s<2.0 at 1.02T_{c} .<br/>[Phys. Rev. Lett. 100, 162001] Published Wed Apr 23, 2008 Harvey B. Meyer 2008-04-23T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162001 Phys. Rev. Lett. 100, 162001 text/html article Physical Review Letters 100 16 2008-04-23T00:00:00-04:00 162001 Elementary Particles and Fields Elementary Particles and Fields http://link.aps.org/doi/10.1103/PhysRevLett.100.162002 Author(s): F. X. Girod et al. CLAS Collaboration<br/>The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (e [over →] p→epγ) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (x_{B} from 0.11 to 0.58, Q^{2} from 1 to 4.8  GeV^{2} , -t from 0.09 to 1.8  GeV^{2} ), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A≃asin⁡ϕ/(1+ccos⁡ϕ). This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector.<br/>[Phys. Rev. Lett. 100, 162002] Published Wed Apr 23, 2008 F. X. Girod et al. CLAS Collaboration 2008-04-23T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162002 Phys. Rev. Lett. 100, 162002 text/html article Physical Review Letters 100 16 2008-04-23T00:00:00-04:00 162002 Elementary Particles and Fields Elementary Particles and Fields http://link.aps.org/doi/10.1103/PhysRevLett.100.162501 Author(s): Alexander Volya<br/>An ensemble with random n-body interactions is investigated in the presence of symmetries. A striking emergence of regularities in the spectra, ground state spins, and isospins is discovered. In even-particle systems the strong preponderance of spin zero ground states is observed with three, four, and higher-order random many-body interactions, and similar trends are discovered in systems that possess both rotational and isospin symmetry. Various types of correlations from pairing to spectral sequences and correlations across different masses are explored. A search for an interpretation is presented.<br/>[Phys. Rev. Lett. 100, 162501] Published Tue Apr 22, 2008 Alexander Volya 2008-04-22T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162501 Phys. Rev. Lett. 100, 162501 text/html article Physical Review Letters 100 16 2008-04-22T00:00:00-04:00 162501 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevLett.100.164801 Author(s): M. Wakasugi, T. Emoto, Y. Furukawa, K. Ishii, S. Ito, T. Koseki, K. Kurita, A. Kuwajima, T. Masuda, A. Morikawa, M. Nakamura, A. Noda, T. Ohnishi, T. Shirai, T. Suda, H. Takeda, T. Tamae, H. Tongu, S. Wang, and Y. Yano<br/>A novel internal target has been developed, which will make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. An “ion trapping” phenomenon in the electron storage ring was successfully utilized for the first time to form the target for electron scattering. Approximately 7×10^{6} stable ^{133} Cs ions were trapped along the electron beam axis for 85 ms at an electron beam current of 80 mA. The collision luminosity between the stored electrons and trapped Cs ions was determined to be 2.4(8)×10^{25}   cm^{-2}  s^{-1} by measuring elastically scattered electrons.<br/>[Phys. Rev. Lett. 100, 164801] Published Tue Apr 22, 2008 M. Wakasugi, T. Emoto, Y. Furukawa, K. Ishii, S. Ito, T. Koseki, K. Kurita, A. Kuwajima, T. Masuda, A. Morikawa, M. Nakamura, A. Noda, T. Ohnishi, T. Shirai, T. Suda, H. Takeda, T. Tamae, H. Tongu, S. Wang, and Y. Yano 2008-04-22T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.164801 Phys. Rev. Lett. 100, 164801 text/html article Physical Review Letters 100 16 2008-04-22T00:00:00-04:00 164801 Plasma and Beam Physics Plasma and Beam Physics http://link.aps.org/doi/10.1103/PhysRevD.77.074016 Author(s): Swarup Kumar Majee and Amitava Raychaudhuri<br/>The purported observation of a state Θ^{+} with strangeness S=+1 led to its quark model interpretation in terms of a pentaquark combination involving a triquark-diquark structure—the Karliner-Lipkin model. In this work, the proper color-spin symmetry properties for the qqq [over ¯] triquark are elucidated by calculating the SU(6) unitary scalar factors and Racah coefficients. Using these results, the color-spin hyperfine interactions, including flavor symmetry breaking therein, become straightforward to incorporate and the pentaquark masses are readily obtained. We examine the effect on the pentaquark mass of (a) deviations from the flavor symmetric limit and (b) different strengths of the doublet and triplet hyperfine interactions. Reference values of these parameters yield a Θ^{+} mass prediction of 1601 MeV but it can comfortably accommodate 1540 MeV for alternate choices. In the same framework, other pentaquark states Ξ(S=-2) and Θ^{c} (with charm C=-1) are expected at 1783 MeV and 2757 MeV, respectively.<br/>[Phys. Rev. D 77, 074016] Published Tue Apr 22, 2008 Swarup Kumar Majee and Amitava Raychaudhuri 2008-04-22T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.074016 Phys. Rev. D 77, 074016 text/html article Physical Review D 77 7 2008-04-22T00:00:00-04:00 074016 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.162301 Author(s): Jörg Ruppert, Charles Gale, Thorsten Renk, Peter Lichard, and Joseph I. Kapusta<br/>The NA60 experiment has measured low mass muon pair production in In-In collisions at 158A  GeV with unprecedented precision. We show that these data are reproduced very well by a dynamical model with parameters scaled from fits to measurements of hadronic transverse mass spectra and Hanbury Brown–Twiss correlations in Pb-Pb and Pb-Au collisions at the same energy. The data are consistent with in-medium properties of ρ and ω mesons at finite temperature and density as deduced from empirical forward-scattering amplitudes. Inclusion of the vacuum decay of the ρ meson after freeze-out is necessary for an understanding of the mass and transverse momentum spectrum of dimuons with M≲0.9  GeV/c^{2} .<br/>[Phys. Rev. Lett. 100, 162301] Published Mon Apr 21, 2008 Jörg Ruppert, Charles Gale, Thorsten Renk, Peter Lichard, and Joseph I. Kapusta 2008-04-21T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.162301 Phys. Rev. Lett. 100, 162301 text/html article Physical Review Letters 100 16 2008-04-21T00:00:00-04:00 162301 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevD.77.074015 Author(s): Micaela Oertel and Michael Urban<br/>Surface effects in strange-quark matter play an important role for certain observables which have been proposed in order to identify strange stars, and color superconductivity can strongly modify these effects. We study the surface of color superconducting strange-quark matter by solving the Hartree-Fock-Bogoliubov equations for finite systems (“strangelets”) within the MIT bag model, supplemented with a pairing interaction. Because of the bag-model boundary condition, the strange-quark density is suppressed at the surface. This leads to a positive surface charge, concentrated in a layer of ∼1  fm below the surface, even in the color-flavor locked (CFL) phase. However, since in the CFL phase all quarks are paired, this positive charge is compensated by a negative charge, which turns out to be situated in a layer of a few tens of fm below the surface, and the total charge of CFL strangelets is zero. We also study the surface and curvature contributions to the total energy. Because of the strong pairing, the energy as a function of the mass number is very well reproduced by a liquid-drop type formula with curvature term.<br/>[Phys. Rev. D 77, 074015] Published Mon Apr 21, 2008 Micaela Oertel and Michael Urban 2008-04-21T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevD.77.074015 Phys. Rev. D 77, 074015 text/html article Physical Review D 77 7 2008-04-21T00:00:00-04:00 074015 D1 D1 http://link.aps.org/doi/10.1103/PhysRevLett.100.151102 Author(s): Jes Madsen<br/>Electron-positron pair creation in supercritical electric fields limits the net charge of any static, spherical object, such as superheavy nuclei, strangelets, and Q balls, or compact stars like neutron stars, quark stars, and black holes. For radii between 4×10^{2} and 10^{4}   fm the upper bound on the net charge is given by the universal relation Z=0.71R_{fm} , and for larger radii (measured in femtometers or kilometers) Z=7×10^{-5} R_{fm}^{2} =7×10^{31} R_{km}^{2} . For objects with nuclear density the relation corresponds to Z≈0.7A^{1/3} (10^{8} <A<10^{12} ) and Z≈7×10^{-5} A^{2/3} (A>10^{12} ), where A is the baryon number. For some systems this universal upper bound improves existing charge limits in the literature.<br/>[Phys. Rev. Lett. 100, 151102] Published Thu Apr 17, 2008 Jes Madsen 2008-04-17T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.151102 Phys. Rev. Lett. 100, 151102 text/html article Physical Review Letters 100 15 2008-04-17T00:00:00-04:00 151102 Gravitation and Astrophysics Gravitation and Astrophysics http://link.aps.org/doi/10.1103/PhysRevLett.100.152301 Author(s): X. Zhu, N. Xu, and P. Zhuang<br/>In high-energy collisions, massive heavy quarks are produced back to back initially and they are sensitive to early dynamical conditions. The strong collective partonic wind from the fast expanding quark-gluon plasma created in high-energy nuclear collisions modifies the correlation pattern significantly. While the hot and dense medium in collisions at the BNL Relativistic Heavy Ion Collider ( sqrt[s_{NN} ] =200  GeV) can only smear the initial back-to-back DD [over ¯] correlation, a clear and strong near side DD [over ¯] correlation is expected at the CERN Large Hadron Collider ( sqrt[s_{NN} ] =5500  GeV). This is considered as a signature for the strongly coupled quark-gluon plasma.<br/>[Phys. Rev. Lett. 100, 152301] Published Thu Apr 17, 2008 X. Zhu, N. Xu, and P. Zhuang 2008-04-17T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.152301 Phys. Rev. Lett. 100, 152301 text/html article Physical Review Letters 100 15 2008-04-17T00:00:00-04:00 152301 Nuclear Physics Nuclear Physics http://link.aps.org/doi/10.1103/PhysRevLett.100.152502 Author(s): C. R. Hoffman, T. Baumann, D. Bazin, J. Brown, G. Christian, P. A. DeYoung, J. E. Finck, N. Frank, J. Hinnefeld, R. Howes, P. Mears, E. Mosby, S. Mosby, J. Reith, B. Rizzo, W. F. Rogers, G. Peaslee, W. A. Peters, A. Schiller, M. J. Scott, S. L. Tabor, M. Thoennessen, P. J. Voss, and T. Williams<br/>The neutron unbound ground state of ^{25} O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a ^{26} F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770_{-10}^{+20}   keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the ν1s_{1/2} and ν0d_{3/2} orbitals. The neutron separation energies for ^{25} O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an ^{26} O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of ^{26} O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.<br/>[Phys. Rev. Lett. 100, 152502] Published Thu Apr 17, 2008 C. R. Hoffman, T. Baumann, D. Bazin, J. Brown, G. Christian, P. A. DeYoung, J. E. Finck, N. Frank, J. Hinnefeld, R. Howes, P. Mears, E. Mosby, S. Mosby, J. Reith, B. Rizzo, W. F. Rogers, G. Peaslee, W. A. Peters, A. Schiller, M. J. Scott, S. L. Tabor, M. Thoennessen, P. J. Voss, and T. Williams 2008-04-17T00:00:00-04:00 Personal use only, all commercial or other reuse prohibited 10.1103/PhysRevLett.100.152502 Phys. Rev. Lett. 100, 152502 text/html article Physical Review Letters 100 15 2008-04-17T00:00:00-04:00 152502 Nuclear Physics Nuclear Physics