Department of Physics and Astronomy
Permanent link for this collectionhttps://hdl.handle.net/2022/22354
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Item A Dynamical Study of the Non-Star Forming Translucent Molecular Cloud MBM16: Evidence for Shear Driven Turbulence in the Interstellar Medium(IOP Publishing, 1998-09) LaRosa, Theodore N.; Shore, Steven N.; Magnani, Loris AlbertoWe present the results of a velocity correlation study of the high latitude cloud MBM16 using a fully sampled 12CO map, supplemented by new 13CO data. We find a correlation length of 0.4 pc. This is similar in size to the formaldehyde clumps described in our previous study. We associate this correlated motion with coherent structures within the turbulent flow. Such structures are generated by free shear flows. Their presence in this non-star forming cloud indicates that kinetic energy is being supplied to the internal turbulence by an external shear flow. Such large scale driving over long times is a possible solution to the dissipation problem for molecular cloud turbulence.Item Landau–Ginzburg Vacua of String, M- and F-Theory at c = 12(Elsevier [Commercial Publisher], 1998-12) Lynker, Monika; Schimmrigk, Rolf; Wisskirchen, AndreasTheories in more than ten dimensions play an important role in understanding nonperturbative aspects of string theory. Consistent compactifications of such theories can be constructed via Calabi-Yau fourfolds. These models can be analyzed particularly efficiently in the Landau-Ginzburg phase of the linear σ-model, when available. In the present paper we focus on those σ-models which have both a Landau-Ginzburg phase and a geometric phase described by hypersurfaces in weighted projective five-space. We describe some of the pertinent properties of these models, such as the cohomology, the connectivity of the resulting moduli space, and mirror symmetry among the 1,100,055 configurations which we have constructed.Item Evidence for nonequilibrium proton emission in a low-energy heavy-ion reaction(American Physical Society, 1999) DeYoung, Paul A.; Hinnefeld, JerryCorrelation functions for p-p, p-d, p-α, d-α, and α-α were measured for the 16O+27Al system at a beam energy of 72 MeV. The detector array was centered at laboratory angle of 20°. Compared to published data obtained at larger scattering angles, an unexpected dependence on angle is seen for the p-p channel. The observed anticorrelation is stronger at more forward angles, which suggests that correlation functions are sensitive to the specific reaction mechanisms producing the light-charged particles.Item Proton elastic scattering from 7Be at low energies.(American Physical Society, 2001-01) Rogachev, Grigoriy V.; Hinnefeld, JerryThe elastic scattering of protons on 7Be has been measured in the energy region from 1-3.3 MeV via the thick-target technique. The data conclusively demonstrate the existence of a 2− state at an excitation energy of approximately 3.5 MeV in 8B, and rule out a predicted 1+ state near 1.4 MeV. The relevance of these results for the 7Be (p,γ) reaction, of interest in solar neutrino physics, is discussed.Item Evolution of Li, Be and B in the Galaxy(American Astronomical Society, 2001-10) Valle, Giada; Ferrini, Federico; Galli, Daniele; Shore, Steven N.In this paper we study the production of Li, Be and B nuclei by Galactic cosmic ray spallation processes. We include three kinds of processes: (i ) spallation by light cosmic rays impinging on interstellar CNO nuclei (direct processes); (ii ) spallation by CNO cosmic ray nuclei impinging on interstellar p and 4He (inverse processes); and (iii ) α–α fusion reactions. The latter dominate the production of 6,7Li. We calculate production rates for a closed-box Galactic model, verifying the quadratic dependence of the Be and B abundances for low values of Z. These are quite general results and are known to disagree with observations. We then show that the multi-zone multi-population model we used previously for other aspects of Galactic evolution produces quite good agreement with the linear trend observed at low metallicities without fine tuning. We argue that reported discrepancies between theory and observations do not represent a nucleosynthetic problem, but instead are the consequences of inaccurate treatments of Galactic evolution.Item New developments and recent results in nuclear astrophysics at Louvain-la-Neuve(American Physical Society, 2002-04) Cherubini, S.; Hinnefeld, JerryNuclear astrophysics using radioactive nuclear beams is one of the major research topics in Louvain-la-Neuve. Recently, experiment aiming at the measurement of (α,γ), and (α, p) reactions have been performed. The 15O(α,γ)19Ne reaction was studied using an indirect method based on the study of the 18Ne(d, p)19Ne*. Preliminary results of a new analysis of this experiment are presented here. The new mass recoil separator ARES, coupled to the new cyclotron CYCLONE-44, is now operational. The ARES project status and results of performance tests are reported here.Item Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory(American Physical Society, 2002-07) Ahmad, Q. R.; Levine, IlanObservations of neutral-current n interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current (NC), elastic scattering, and charged current reactions and assuming the standard 8B shape, the ne component of the 8B solar flux is Φe = 1.76 +0.05 -0.05 (stat)+0.09 -0.09(syst) x 10^6 cm^-2 s^-1 for a kinetic energy threshold of 5 MeV. The non-ve component is Φe = 3.41 +0.45 -0.45(stat) +0.48 -0.45(syst) x 10^6 cm^-2 s^-1, 5.3o greater than zero, providing strong evidence for solar ve flavor transformation. The total flux measured with the NC reaction is ΦNC = 5.09 +0.44 -0.43(stat) =0.46 -0.43(syst) x 10^6 cm^-2 s^-1, consistent with solar models.Item Complex Multiplication Symmetry of Black Hole Attractors(Elsevier, 2003) Lynker, Monika; Periwal, Vipul; Schimmrigk, RolfWe show how Moore’s observation, in the context of toroidal compactifications in type IIB string theory, concerning the complex multiplication structure of black hole attractor varieties, can be generalized to Calabi-Yau compactifications with finite fundamental groups. This generalization leads to an alternative general framework in terms of motives associated to a Calabi-Yau variety in which it is possible to address the arithmetic nature of the attractor varieties in a universal way via Deligne’s period conjecture.Item Final state interaction or a 3H excited state?(American Physical Society, 2003) Rogachev, Grigoriy V.; Hinnefeld, JerryAn inclusive a-particle spectrum from the 1H(6He,a) reaction has been measured at a 6He laboratory energy of 23.9 MeV. A resonancelike structure is observed at an a-particle lab energy of about 20 MeV, which corresponds to an energy of End50.6 MeV in the n-d channel. An analysis of the spectrum shows that it cannot be explained by the effect of binary final-state interactions. The hypotheses that this structure represents ~a! a new excited state of tritium or ~b! a three-body final-state interaction are discussed.Item Electron Antineutrino Search at the Sudbury Neutrino Observatory(American Physical Society, 2004) Aharmin, Bassam; Levine, IlanUpper limits on the v¯e flux at the Sudbury Neutrino Observatory have been set based on the v¯e charged-current reaction on deuterium. The reaction produces a positron and two neutrons in coincidence. This distinctive signature allows a search with very low background for v¯e’s from the Sun and other potential sources. Both differential and integral limits on the v¯e flux have been placed in the energy range from 4 – 14.8 MeV. For an energy-independent ve -> v¯e conversion mechanism, the integral limit on the flux of solar v¯e’s in the energy range from 4 – 14.8 MeV is found to be Φv¯e ≤ 3.4 × 104cm−2s−1 (90% C.L.), which corresponds to 0.81% of the standard solar model 8B e flux of 5.05 × 106cm−2s−1, and is consistent with the more sensitive limit from KamLAND in the 8.3 – 14.8 MeV range of 3.7×102cm−2s−1 (90% C.L.). In the energy range from 4 – 8 MeV, a search for v¯e’s is conducted using coincidences in which only the two neutrons are detected. Assuming a v¯e spectrum for the neutron induced fission of naturally occurring elements, a flux limit of Φv¯e 2.0 × 106cm−2s−1 (90% C.L.) is obtained.Item Measurement of the Total Active 8B Solar Neutrino Flux at the Sudbury Neutrino Observatory with Enhanced Neutral Current Sensitivity(American Physical Society, 2004) Ahmed, S. N.; Levine, IlanThe Sudbury Neutrino Observatory (SNO) has precisely determined the total active (nu_x) 8B solar neutrino flux without assumptions about the energy dependence of the nu_e survival probability. The measurements were made with dissolved NaCl in the heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21 +/- 0.27 (stat) +/- 0.38 (syst) x10^6 cm^{-2}s^{-1}, in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Delta m^{2} = 7.1^{+1.2}_{-0.6}x10^{-5} ev^2 and theta = 32.5^{+2.4}_{-2.3} degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviationsItem Constraints on Nucleon Decay via “Invisible” Modes from the Sudbury Neutrino Observatory(Physical Review, 2004) Ahmed, S. N.; Anthony, A. E.; Beier, E. W.; Bellerive, A.; Biller, S. D.; Boger, J.; Boulay, M. G.; Bowler, M. G.; Bowles, T. J.; Brice, S. J.; Bullard, T. V.; Chan, Y. D.; Chen, M.; Chen, X.; Cleveland, B. T.; Cox, G. A.; Dai, X.; Dalnoki-Veress, F.; Doe, P. J.; Dosanjh, R. S.; Doucas, G.; Dragowsky, M. R.; Duba, C. A.; Duncan, F. A.; Dunford, M.; Dunmore, J. A.; Earle, E. D.; Elliott, S. R.; Evans, H. C.; Ewan, G. T.; Farine, J.; Fergani, H.; Fleurot, F.; Formaggio, J. A.; Fowler, M. M.; Frame, K.; Frati, W.; Fulsom, B. G.; Gagnon, N.; Graham, K.; Grant, D. R.; Hahn, R. L.; Hall, J. C.; Hallin, A. L.; Hallman, E. D.; Hamer, A. S.; Handler, W. B.; Hargrove, C. K.; Harvey, P. J.; Hazama, R.; Heeger, K. M.; Heintzelman, W. J.; Heise, J.; Helmer, R. L.; Hemingway, R. J.; Hime, A.; Howe, M. A.; Jagam, P.; Jelley, N. A.; Klein, J. R.; Kos, M. S.; Krumins, A. V.; Kutter, T.; Kyba, C. C. M.; Labranche, H.; Lange, R.; Law, J.; Lawson, I. T.; Lesko, K. T.; Leslie, J. R.; Levine, Ilan; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H. B.; Maneira, J.; Marino, A. D.; McCauley, N.; McDonald, A. B.; McGee, S.; McGregor, G.; Mifflin, C.; Miknaitis, K. K. S.; Miller, G. G.; Moffat, B. A.; Nally, C. W.; Neubauer, M. S.; Nickel, B. G.; Noble, A. J.; Norman, E. B.; Oblath, N. S.; Okada, C. E.; Ollerhead, R. W.; Orrell, J. L.; Oser, S. M.; Ouellet, C.; Peeters, S. J. M.; Poon, A. W. P.; Robertson, B. C.; Robertson, R. G. H.; Rollin, E.; Rosendahl, S. S. E.; Rusu, V. L.; Schwendener, M. H.; Simard, O.; Simpson, J. J.; Sims, C. J.; Sinclair, D.; Skensved, P.; Smith, M. W. E.; Starinsky, N.; Stokstad, R. G.; Stonehill, L. C.; Tafirout, R.; Takeuchi, Y.; Tešić, G.; Thomson, M.; Thorman, M.; Van Berg, R.; Van de Water, R. G.; Virtue, C. J.; Wall, B. L.; Waller, D.; Waltham, C. E.; Wan Chan Tseung, H.; Wark, D. L.; West, N.; Wilhelmy, J. B.; Wilkerson, J. F.; Wilson, J. R.; Wittich, P.; Wouters, J. M.; Yeh, M.; Zuber, K.Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to “invisible” modes, such as n -> 3v. The analysis was based on a search for y-rays from the de-excitation of the residual nucleus that would result from the disappearance of either a proton or neutron from ^16O. A limit of t inv > 2×1029 years is obtained at 90% confidence for either neutron or proton decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton decay modes and 400 times more stringent than similar neutron modes.Item Observation and Properties of the X(3872) Decaying to J/ψπ+π− in p¯p Collisions at √s = 1.96 TeV(American Physical Society, 2004-09) Abazov, V. M.; Luo, C.; Lynker, MonikaWe report the observation of the X(3872) in the J/psi pi+pi- channel, with J/psi decaying to mu+mu- in p-p(bar) collisions at sqrt(s) = 1.96 TeV. Using approximately 230 pb^-1 of data collected with the Run II D0 detector, we observe 522 +/- 100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9 +/- 3.1 (stat.) +/- 3.0 (syst.) MeV/c^2. We have investigated the production and decay characteristics of the X(3872), and find them to be similar to those of the psi(2S) state.Item Fabrication of a Nodular Neutron Array: A Collaborative Approach to Undergraduate Research(American Association of Physics Teachers, 2005-02) Howes, R. H.; Hinnefeld, J.The construction of the modular neutron array, a highly efficient time-of-flight detector, for use with the recently upgraded coupled cyclotron facility at the National Superconducting Cyclotron Laboratory has been accomplished by a collaboration of undergraduate physics departments. The collaboration presents an opportunity for involving faculty and students from undergraduate physics programs in state-of-the-art physics experiments at large user facilities.Item Improved Spin Dependent Limits from the PICASSO Dark Matter Search Experiment(Elsevier, 2005-09) Barnabe-Heider, Marik; Behnke, Joshua; Feighery, William.; Levine, Ilan; Muthusi, CynthiaThe PICASSO experiment reports an improved limit for the existence of cold dark matter WIMPs interacting via spin-dependent interactions with nuclei. The experiment is installed in the Sudbury Neutrino Observatory at a depth of 2070 m. With superheated C4F10 droplets as the active material, and an exposure of 1.98±0.19 kgd, no evidence for a WIMP signal was found. For a WIMP mass of 29 GeV/c2, limits on the spin-dependent cross section on protons of σp = 1.31 pb and on neutrons of σn = 21.5 pb have been obtained at 90% C.L. In both cases, some new parameter space in the region of WIMP masses below 20 GeV/c2 has now been ruled out. The results of these measurements are also presented in terms of limits on the effective WIMP-proton and neutron coupling strengths ap and an.Item A Search for Periodicities in the 8B Solar Neutrino Flux Measured by the Sudbury Neutrino Observatory(American Physical Society, 2005-10) Levine, IlanA search has been made for sinusoidal periodic variations in the 8B solar neutrino flux using data collected by the Sudbury Neutrino Observatory over a 4-year time interval. The variation at a period of one year is consistent with modulation of the 8B neutrino flux by the Earth’s orbital eccentricity. No significant sinusoidal periodicities are found with periods between 1 day and 10 years with either an unbinned maximum likelihood analysis or a Lomb-Scargle periodogram analysis. The data are inconsistent with the hypothesis that the results of the recent analysis by Sturrock et al., based on elastic scattering events in Super-Kamiokande, can be attributed to a 7% sinusoidal modulation of the total 8B neutrino flux.Item The Langlands Program and String Modular K3 Surfaces(Nuclear Physics B, 2006-03) Schimmrigk, RolfA number theoretic approach to string compactification is developed for Calabi-Yau hypersurfaces in arbitrary dimensions. The motivic strategy involved is illustrated by showing that the Hecke eigenforms derived from Galois group orbits of the holomorphic two-form of a particular type of K3 surfaces can be expressed in terms of modular forms constructed from the worldsheet theory. The process of deriving string physics from spacetime geometry can be reversed, allowing the construction of K3 surface geometry from the string characters of the partition function. A general argument for K3 modularity follows from mirror symmetry, in combination with the proof of the Shimura-Taniyama conjecture.Item Selective Population and Neutron Decay of the First Excited State of Semi-Magic 23O(American Physical Society, 2006-12) Schiller, Andreas; Hinnefeld, JerryWe have observed an excited state in the neutron-rich semi-magic nucleus 23O for the first time. No such states have been found in previous searches using y-ray spectroscopy. The observation of a resonance in n-fragment coincidence measurements confirms the speculation in the literature that the lowest excited state is neutron unbound and establishes positive evidence for a 2.8(1) MeV excitation energy of the first excited state in 23O. The non-observation of a predicted second excited state is explained assuming selectivity of inner-shell knockout reactions.Item A modularity test for elliptic mirror symmetry(Physics Letters B, 2007) Schimmrigk, RolfIn this Letter a previously initiated program to construct space from modular forms on the string worldsheet is applied to mirror symmetry. Predictions of an algebraic mirror construction are confirmed for elliptic curves of Brieskorn–Pham type by showing that the string theoretic modular forms associated to the Hasse–Weil L-series of mirror pairs of such curves are identical.Item Equation of state and high-pressure stability of Fe3P-schreibersite: Implications for phosphorus storage in planetary cores(Wiley, 2007) Scott, Henry P.; Huggins, Sabrina; Frank, Mark R.; Maglio, Steven J.; Martin, C. David; Meng, Yue; Santillán, Javier; Williams, QuentinWe have collected in situ X-ray diffraction patterns of end-member Fe3P-schreibersite in a diamond anvil cell to pressures of 30 GPa at 300 K. Some samples of Fe3P were also laser heated at high pressure to temperatures of ~2000 K and examined following thermal quench. Below 8 GPa, variation of the schreibersite unit cell delineates a smooth pressure-volume curve corresponding to a second order Birch-Murnaghan equation of state with bulk modulus, K0T, of 159(1) GPa. Above 8 GPa, however, the schreibersite structure shows substantial stiffening, and an unidentified structure develops between 17 and 30 GPa; upon decompression to ambient pressure the schreibersite structure returns. Therefore, although ubiquitous in iron-rich meteorites, it is unlikely that schreibersite is the stable phosphorus-bearing phase in deep planetary cores.
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