Magnetization steps in Zn_(1-x)Mn_xO: Four largest exchange constants and single-ion anisotropy

Magnetization steps (MST's) from Mn pairs in several single crystals of Zn_(1-x)Mn_xO (0.0056<=x<=0.030, and in one powder (x=0.029), were observed. The largest two exchange constants, J1/kB=-18.2+/-0.5K and J1'/kB=-24.3+/-0.6K, were obtained from large peaks in the differential susceptibility, dM/dH, measured in pulsed magnetic fields, H, up to 500 kOe. These two largest J's are associated with the two inequivalent classes of nearest neighbors (NN's) in the wurtzite structure. The 29% difference between J1 and J1' is substantially larger than 13% in CdS:Mn, and 15% in CdSe:Mn. The pulsed-field data also indicate that, despite the direct contact between the samples and a superfluid-helium bath, substantial departures from thermal equilibrium occurred during the 7.4 ms pulse. The third- and fourth-largest J's were determined from the magnetization M at 20 mK, measured in dc magnetic fields H up to 90 kOe. Both field orientations H||c and H||[10-10] were studied. (The [10-10] direction is perpendicular to the c-axis, [0001].) By definition, neighbors which are not NN's are distant neighbors (DN's). The largest DN exchange constant (third-largest overall), has the value J/kB=-0.543+/-0.005K, and is associated with the DN at r=c. Because this is not the closest DN, this result implies that the J's do not decrease monotonically with the distance r. The second-largest DN exchange constant (fourth-largest overall), has the value J/kB=-0.080 K. It is associated with one of the two classes of neighbors that have a coordination number z=12, but the evidence is insufficient for a definite unique choice. The dependence of M on the direction of H gives D/kB=-0.039+/-0.008K, in fair agreement with -0.031 K from earlier EPR work.Comment: 12 pages, 10 figures. Submitted to PR

Single Spin Asymmetry ANA_N in Polarized Proton-Proton Elastic Scattering at s=200\sqrt{s}=200 GeV

We report a high precision measurement of the transverse single spin asymmetry $A_N$ at the center of mass energy $\sqrt{s}=200$ GeV in elastic proton-proton scattering by the STAR experiment at RHIC. The $A_N$ was measured in the four-momentum transfer squared $t$ range $0.003 \leqslant |t| \leqslant 0.035$ \GeVcSq, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of $A_N$ and its $t$-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this $\sqrt{s}$, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure

Evolution of the differential transverse momentum correlation function with centrality in Au+Au collisions at sNN=200\sqrt{s_{NN}} = 200 GeV

We present first measurements of the evolution of the differential transverse momentum correlation function, {\it C}, with collision centrality in Au+Au interactions at $\sqrt{s_{NN}} = 200$ GeV. {\it C} exhibits a strong dependence on collision centrality that is qualitatively similar to that of number correlations previously reported. We use the observed longitudinal broadening of the near-side peak of {\it C} with increasing centrality to estimate the ratio of the shear viscosity to entropy density, $\eta/s$, of the matter formed in central Au+Au interactions. We obtain an upper limit estimate of $\eta/s$ that suggests that the produced medium has a small viscosity per unit entropy.Comment: 7 pages, 4 figures, STAR paper published in Phys. Lett.

Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology

notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations

J/ψ polarization in p+p collisions at s=200 GeV in STAR

AbstractWe report on a polarization measurement of inclusive J/ψ mesons in the di-electron decay channel at mid-rapidity at 2<pT<6 GeV/c in p+p collisions at s=200 GeV. Data were taken with the STAR detector at RHIC. The J/ψ polarization measurement should help to distinguish between different models of the J/ψ production mechanism since they predict different pT dependences of the J/ψ polarization. In this analysis, J/ψ polarization is studied in the helicity frame. The polarization parameter λθ measured at RHIC becomes smaller towards high pT, indicating more longitudinal J/ψ polarization as pT increases. The result is compared with predictions of presently available models

Measurement Of Charge Multiplicity Asymmetry Correlations In High-energy Nucleus-nucleus Collisions At Snn =200 Gev

A study is reported of the same- and opposite-sign charge-dependent azimuthal correlations with respect to the event plane in Au+Au collisions at sNN=200 GeV. The charge multiplicity asymmetries between the up/down and left/right hemispheres relative to the event plane are utilized. The contributions from statistical fluctuations and detector effects were subtracted from the (co-)variance of the observed charge multiplicity asymmetries. In the mid- to most-central collisions, the same- (opposite-) sign pairs are preferentially emitted in back-to-back (aligned on the same-side) directions. The charge separation across the event plane, measured by the difference, Δ, between the like- and unlike-sign up/down-left/right correlations, is largest near the event plane. The difference is found to be proportional to the event-by-event final-state particle ellipticity (via the observed second-order harmonic v2obs), where Δ=[1.3±1.4(stat)-1.0+4.0(syst)]×10- 5+[3.2±0.2(stat)-0.3+0.4(syst)]×10-3v2obs for 20-40% Au+Au collisions. The implications for the proposed chiral magnetic effect are discussed. © 2014 American Physical Society.894NRF-2012004024; National Research FoundationArsene, I., (2005) Nucl. Phys. A, 757, p. 1. , (BRAHMS Collaboration),. NUPABL 0375-9474 10.1016/j.nuclphysa.2005.02.130Back, B.B., (2005) Nucl. Phys. A, 757, p. 28. , (PHOBOS Collaboration),. NUPABL 0375-9474 10.1016/j.nuclphysa.2005.03.084Adams, J., (2005) Nucl. Phys. A, 757, p. 102. , (STAR Collaboration),. NUPABL 0375-9474 10.1016/j.nuclphysa.2005.03.085Adcox, K., (2005) Nucl. Phys. A, 757, p. 184. , (PHENIX Collaboration),. NUPABL 0375-9474 10.1016/j.nuclphysa.2005.03.086Lee, T.D., (1973) Phys. Rev. D, 8, p. 1226. , 0556-2821 10.1103/PhysRevD.8.1226Lee, T.D., Wick, G.C., (1974) Phys. Rev. D, 9, p. 2291. , 0556-2821 10.1103/PhysRevD.9.2291Morley, P.D., Schmidt, I.A., (1985) Z. Phys. C, 26, p. 627. , ZPCFD2 0170-9739 10.1007/BF01551807Kharzeev, D., Pisarski, R.D., Tytgat, M.H.G., (1998) Phys. Rev. Lett., 81, p. 512. , PRLTAO 0031-9007 10.1103/PhysRevLett.81.512Kharzeev, D., (2006) Phys. Lett. B, 633, p. 260. , PYLBAJ 0370-2693 10.1016/j.physletb.2005.11.075Kharzeev, D., Zhitnitsky, A., (2007) Nucl. Phys. A, 797, p. 67. , NUPABL 0375-9474 10.1016/j.nuclphysa.2007.10.001Fukushima, K., Kharzeev, D.E., Warringa, H.J., (2008) Phys. Rev. D, 78, p. 074033. , PRVDAQ 1550-7998 10.1103/PhysRevD.78.074033Kharzeev, D.E., McLerran, L.D., Warringa, H.J., (2008) Nucl. Phys. A, 803, p. 227. , NUPABL 0375-9474 10.1016/j.nuclphysa.2008.02.298Voloshin, S.A., (2004) Phys. Rev. C, 70, p. 057901. , PRVCAN 0556-2813 10.1103/PhysRevC.70.057901Abelev, B.I., (2009) Phys. Rev. Lett., 103, p. 251601. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.103.251601Abelev, B.I., (2010) Phys. Rev. C, 81, p. 054908. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.81.054908Abelev, B., (2013) Phys. Rev. Lett., 110, p. 012301. , (ALICE Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.110.012301Wang, Q., (2012), http://drupal.star.bnl.gov/STAR/theses/phd/quanwang, Ph.D. thesis, Purdue University, arXiv:1205.4638Ackermann, K.H., (2003) Nucl. Instrum. Methods A, 499, p. 624. , (STAR Collaboration),. NIMAER 0168-9002 10.1016/S0168-9002(02)01960-5Bieser, F.S., (2003) Nucl. Instrum. Methods A, 499, p. 766. , (STAR Collaboration),. NIMAER 0168-9002 10.1016/S0168-9002(02)01974-5Adler, C., (2003) Nucl. Instrum. Methods A, 499, p. 433. , NIMAER 0168-9002 10.1016/j.nima.2003.08.112Adams, J., (2004) Phys. Rev. Lett., 92, p. 112301. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.92.112301Abelev, B.I., (2009) Phys. Rev. C, 79, p. 034909. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.79.034909Ackermann, K.H., (1999) Nucl. Phys. A, 661, p. 681. , (STAR Collaboration),. NUPABL 0375-9474 10.1016/S0375-9474(99)85117-3Anderson, M., (2003) Nucl. Instrum. Methods A, 499, p. 659. , NIMAER 0168-9002 10.1016/S0168-9002(02)01964-2Poskanzer, A.M., Voloshin, S.A., (1998) Phys. Rev. C, 58, p. 1671. , PRVCAN 0556-2813 10.1103/PhysRevC.58.1671Wang, G., (2005), http://drupal.star.bnl.gov/STAR/theses/ph-d/gang-wang, Ph.D. thesis, UCLAAdamczyk, L., (2012) Phys. Rev. Lett., 108, p. 202301. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.108.202301Wang, F., (2010) Phys. Rev. C, 81, p. 064902. , PRVCAN 0556-2813 10.1103/PhysRevC.81.064902Pratt, S., Schlichting, S., Gavin, S., (2011) Phys. Rev. C, 84, p. 024909. , PRVCAN 0556-2813 10.1103/PhysRevC.84.024909Adams, J., (2005) Phys. Rev. Lett., 95, p. 152301. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.95.152301Aggarwal, M.M., (2010) Phys. Rev. C, 82, p. 024912. , (STAR collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.82.024912Abelev, B.I., (2009) Phys. Rev. Lett., 102, p. 052302. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.102.052302Abelev, B.I., (2009) Phys. Rev. C, 80, p. 064912. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.80.064912Abelev, B.I., (2010) Phys. Rev. Lett., 105, p. 022301. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.105.022301Agakishiev, H., (STAR Collaboration), arXiv:1010.0690Petersen, H., Renk, T., Bass, S.A., (2011) Phys. Rev. C, 83, p. 014916. , PRVCAN 0556-2813 10.1103/PhysRevC.83.014916Adamczyk, L., (2013) Phys. Rev. C, 88, p. 064911. , (STAR Collaboration),. 10.1103/PhysRevC.88.064911Asakawa, M., Majumder, A., Müller, B., (2010) Phys. Rev. C, 81, p. 064912. , PRVCAN 0556-2813 10.1103/PhysRevC.81.064912Bzdak, A., Koch, V., Liao, J., (2010) Phys. Rev. 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Fluctuations Of Charge Separation Perpendicular To The Event Plane And Local Parity Violation In S Nn = 200 Gev Au + Au Collisions At The Bnl Relativistic Heavy Ion Collider

Previous experimental results based on data (∼15×106 events) collected by the STAR detector at the BNL Relativistic Heavy Ion Collider suggest event-by-event charge-separation fluctuations perpendicular to the event plane in noncentral heavy-ion collisions. Here we present the correlator previously used split into its two component parts to reveal correlations parallel and perpendicular to the event plane. The results are from a high-statistics 200-GeV Au + Au collisions data set (57×106 events) collected by the STAR experiment. We explicitly count units of charge separation from which we find clear evidence for more charge-separation fluctuations perpendicular than parallel to the event plane. We also employ a modified correlator to study the possible P-even background in same- and opposite-charge correlations, and find that the P-even background may largely be explained by momentum conservation and collective motion. © 2013 American Physical Society.886NRF-2012004024; National Research FoundationLee, T.D., Yang, C.N., (1956) Phys. Rev., 104. , 1, 254. 0031-899X PHRVAO 10.1103/PhysRev.104.254Vafa, C., Witten, E., (1984) Phys. Rev. Lett., 53. , 2, 535. 0031-9007 PRLTAO 10.1103/PhysRevLett.53.535Lee, T.D., (1973) Phys. Rev. D, 8. , 3, 1226. 0556-2821 10.1103/PhysRevD.8.1226Lee, T.D., Wick, G.C., (1974) Phys. Rev. D, 9. , 4, 2291. 0556-2821 10.1103/PhysRevD.9.2291Kharzeev, D., Parity violation in hot QCD: Why it can happen, and how to look for it (2006) Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 633 (2-3), pp. 260-264. , DOI 10.1016/j.physletb.2005.11.075, PII S0370269305017430Kharzeev, D., Zhitnitsky, A., (2007) Nucl. Phys. A, 797. , 6, 67. 0375-9474 NUPABL 10.1016/j.nuclphysa.2007.10.001Kharzeev, D., McLerran, L.D., Warringa, H.J., (2008) Nucl. Phys. A, 803. , 7, 227. 0375-9474 NUPABL 10.1016/j.nuclphysa.2008.02.298Fukushima, K., Kharzeev, D.E., Warringa, H.J., (2008) Phys. Rev. D, 78. , 8, 074033. 1550-7998 PRVDAQ 10.1103/PhysRevD.78.074033Abelev, B.I., (2009) Phys. Rev. Lett., 103. , 9 (STAR Collaboration), 251601. 0031-9007 PRLTAO 10.1103/PhysRevLett.103. 251601Abelev, B.I., (2010) Phys. Rev. C, 81. , 10 (STAR Collaboration), 054908. 0556-2813 PRVCAN 10.1103/PhysRevC.81. 054908Abelev, B.I., (2013) Phys. Rev. Lett., 110. , 11 (ALICE Collaboration), 012301. 0031-9007 PRLTAO 10.1103/PhysRevLett. 110.012301Ackermann, K.H., Adams, N., Adler, C., Ahammed, Z., Ahmad, S., Allgower, C., Amonett, J., Harris, J.W., STAR detector overview (2003) Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 499 (2-3), pp. 624-632. , DOI 10.1016/S0168-9002(02)01960-5Adams, J., Aggarwal, M.M., Ahammed, Z., Amonett, J., Anderson, B.D., Arkhipkin, D., Averichev, G.S., Bai, Y., Directed flow in Au+Au collisions at sNN=62.4 GeV (2006) Physical Review C - Nuclear Physics, 73 (3), pp. 1-7. , http://oai.aps.org/oai?verb=GetRecord&Identifier=oai:aps.org: PhysRevC.73.034903&metadataPrefix=oai_apsmeta_2, DOI 10.1103/PhysRevC.73.034903, 034903Adamczyk, L., (2012) Phys. Rev. Lett., 108. , 14 (STAR Collaboration), 202301. 0031-9007 PRLTAO 10.1103/PhysRevLett. 108.202301Voloshin, S.A., Parity violation in hot QCD: How to detect it (2004) Physical Review C - Nuclear Physics, 70 (5), pp. 0579011-0579012. , DOI 10.1103/PhysRevC.70.057901, 057901Poskanzer, A.M., Voloshin, S.A., Methods for analyzing anisotropic flow in relativistic nuclear collisions (1998) Physical Review C - Nuclear Physics, 58 (3), pp. 1671-1678. , DOI 10.1103/PhysRevC.58.1671Ollitrault, J.-Y., Poskanzer, A.M., Voloshin, S.A., (2009) Phys. Rev. C, 80. , 17, 014904. 0556-2813 PRVCAN 10.1103/PhysRevC.80.014904Pratt, S., Schlichting, S., Gavin, S., (2011) Phys. Rev. C, 84. , 18, 024909. 0556-2813 PRVCAN 10.1103/PhysRevC.84.024909Schlichting, S., Pratt, S., (2011) Phys. Rev. C, 83. , 19, 014913. 0556-2813 PRVCAN 10.1103/PhysRevC.83.014913Selyuzhenkov, I., Voloshin, S., (2008) Phys. Rev. C, 77. , 20, 034904. 0556-2813 PRVCAN 10.1103/PhysRevC.77.034904Kisiel, A., (2006) Comput. Phys. Commun., 174. , 21, 669. 0010-4655 CPHCBZ 10.1016/j.cpc.2005.11.010Bzdak, A., Koch, V., Liao, J., (2011) Phys. Rev. C, 83. , 22, 014905. 0556-2813 PRVCAN 10.1103/PhysRevC.83.014905Adams, J., Aggarwal, M.M., Ahammed, Z., Amonett, J., Anderson, B.D., Arkhipkin, D., Averichev, G.S., Grebenyuk, O., Azimuthal anisotropy in Au+Au collisions at sNN=200GeV (2005) Physical Review C - Nuclear Physics, 72 (1), pp. 1-23. , http://oai.aps.org/oai/?verb=ListRecords&metadataPrefix= oai_apsmeta_2&set=journal:PRC:72, DOI 10.1103/PhysRevC.72.014904, 014904Ray, R.L., Longacre, R.S., 24, arXiv:nucl-ex/0008009 and private communicationKopylov, G.I., Podgoretsky, M.I., Kopylov, G.I., Podgoretsky, M.I., (1972) Sov. J. Nucl. Phys., 15. , 25a, 219 ()25b, Phys. Lett. B. 50, 472 (1974) 0370-2693 PYLBAJ 10.1016/0370-2693(74)90263-925c, Sov. J. Part. Nucl. 20, 266 (1989)Goldhaber, G., Goldhaber, S., Lee, W., Pais, A., (1960) Phys. Rev., 120. , 26, 325. 0031-899X PHRVAO 10.1103/PhysRev.120.32

Magnetic structure studies at Brookhaven National Laboratory

The present communication reports the results of several investigations of magnetic structure and magnetic transitions currently in progress or recently completed at Brookhaven National Laboratory. 1°- The intermetallic compound Ni5Er possesses a uniaxial ferromagnetic structure ; the magnetic scattering is consistent with the assignment of essentially zero moment to the nickel, as suggested by measurements of the saturation magnetization. 2°- The compound MnSn2 has been shown to exhibit a sharp transition from an antiferromagnetic structure to one in which the magnitude of the antiferromagnetically coupled moments exhibits a sinusoïdal spatial modulation. The effect of partial substitution of tin by indium is described. 3°- Results of a study of the temperature dependence of the antiferromagnetic reflections of MnSe2, undertaken at the suggestion of J. O. Dimmock, are compared with predictions based on the Landau-Lifshitz theory of second-order phase transitions. 4°- The magnetic structure of Cr2O3 has been reinvestigated, using both single crystals and powdered specimens, and is discussed in relation to current ideas and suggestions in the literature.La communication présenté rapporte les résultats de plusieurs études de structures magnétiques et de transitions magnétiques, actuellement en progrès ou récemment complétées au Laboratoire National de Brookhaven. 1°- Le composé intermétallique Ni5Er possède une structure ferromagnétique uniaxiale ; la diffraction magnétique est en accord avec un moment essentiellement nul du nickel comme les mesures d'aimantation le suggèrent. 2°- Le composé MnSn2 possède une transition brusque d'une structure antiferromagnétique vers une configuration où les amplitudes des moments, couplés antiferromagnétiquement, sont modulées sinusoïdalement. L'effet d'une substitution partielle de l'étain par l'indium est décrit. 3°- Les résultats d'une étude des réflexions antiferromagnétiques de MnSe2 en fonction de la température, étude entreprise sur la suggestion de J. O. Dimmock, sont comparés avec ses prédictions, basées sur la théorie des transitions de second ordre de Landau-Lifshitz. 4°- La structure magnétique de Cr2O3 a été réexaminée sur des poudres et sur un monocristal. Elle est discutée en relation avec les idées et suggestions actuelles de la science

MAGNETIC STRUCTURE STUDIES AT BROOKHAVEN NATIONAL LABORATORY

The results of some current or recently completed investigations of magnetic structure and magnetic transitio-ns in Ni/sub 5/Er, MnSn/sub 2/, MnSe/ sub 2/, and Cr/sub 2/O/sub 3/ are prese nted. (D.C.W.

Existence of fcc TiCr/sub 1/ /sub 8/H/sub 5/ /sub 3/

Originally an orthorhombic structure was assigned to the non-stoichiometric hydride TiCr/sub 1/ /sub 8/H/sub 3/ /sub 6/. Recent neutron and x-ray diffraction data indicated, however, that an alternate interpretation was possible, i.e. the solid consists of two hydride phases, an ..cap alpha..' Laves phase having a composition of TiCr/sub 1/ /sub 8/H/sub 2/ /sub 8/ and an fcc phase with a much higher hydrogen content. This proved to be the case and it has been determined that the high concentration phase has a disordered fluorite structure with a/sub o/=4.27 A. Its hydrogen content, as estimated from diffraction peak intensities, corresponds to TiCr/sub 1/ /sub 8/H/sub 5/ /sub 3/. We have not been able to produce single phase fcc material but have prepared a mixed phase sample with an overall composition of TiCr/sub 1/ /sub 8/H/sub 4/ /sub 8/. The high-pressure reaction leading to the formation of the fluorite phase is very sluggish and irreversible. Pressure-composition-temperature (p-c-T) properties of this system have been determined and are discussed and a revised phase diagram is proposed