Department of Physics and Astronomy

Permanent link for this collectionhttps://hdl.handle.net/2022/22354

Browse

Now showing 1 - 20 of 44

Big Physics At Small Places: The Mongol Horde Model Of Undergraduate Research
(Clute Institute [Commercial Publisher], 2008-02) Voss, Philip J.; Finck, Joseph E.; Howes, Ruth H.; Brown, James; Baumann, Thomas; Schiller, Andreas; Thoennessen, Michael; DeYoung, Paul. A.; Peaslee, Graham F.; Hinnefeld, Jerry; Luther, Bryan; Pancella, Paul V.; Rogers, Warren F.
A model for engaging undergraduates in cutting-edge experimental nuclear physics research at a national user facility is discussed. Methods to involve students and examples of their success are presented.
Complex Multiplication Symmetry of Black Hole Attractors
(Elsevier, 2003) Lynker, Monika; Periwal, Vipul; Schimmrigk, Rolf
We 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.
Constraints on low-mass WIMP interactions on 19F from PICASSO
(Elsevier, 2012) Archambault, Simon; Behnke, Ed; Grace, Emily A.; Levine, Ilan
Recent results from the PICASSO dark matter search experiment at SNOLAB are reported. These results were obtained using a subset of 10 detectors with a total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be obtained which results in an increased sensitivity to interactions from Weakly Interacting Massive Particles (WIMPs) with masses below 10 GeV/c2. No dark matter signal was found. Best exclusion limits in the spin dependent sector were obtained for WIMP masses of 20 GeV/c2 with a cross section on protons of σ SD p = 0.032 pb (90% C.L.). In the spin independent sector close to the low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections larger than σ S I p = 1.41 × 10−4 pb (90% C.L.) are excluded. Keywords: Dark matter, WIMPs, Superheated droplets, SNOLAB
Constraints on Neutrino Lifetime from the Sudbury Neutrino Observatory
(American Physical Society, 2019-02) Aharmin, Bassam; Levine, Ilan
The long baseline between Earth and the Sun makes solar neutrinos an excellent test beam for exploring possible neutrino decay. The signature of such decay would be an energy-dependent distortion of the traditional survival probability which can be fit for using well-developed and high-precision analysis methods. Here a model including neutrino decay is fit to all three phases of 8B solar neutrino data taken by the Sudbury Neutrino Observatory (SNO). This fit constrains the lifetime of neutrino mass state ν2 to be >8.08×10−5 s/eV at 90% confidence. An analysis combining this SNO result with those from other solar neutrino experiments results in a combined limit for the lifetime of mass state ν2 of >1.92×10−3 s/eV at 90% confidence.
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.
Cosmogenic Neutron Production at the Sudbury Neutrino Observatory
(American Physical Society, 2019-12) Aharmin, Bassam; Levine, Ilan
Neutrons produced in nuclear interactions initiated by cosmic-ray muons present an irreducible background to many rare-event searches, even in detectors located deep underground. Models for the production of these neutrons have been tested against previous experimental data, but the extrapolation to deeper sites is not well understood. Here we report results from an analysis of cosmogenically produced neutrons at the Sudbury Neutrino Observatory. A specific set of observables are presented, which can be used to benchmark the validity of geant4 physics models. In addition, the cosmogenic neutron yield, in units of 10−4 cm2/(g⋅μ), is measured to be 7.28±0.09(stat)+1.59−1.12(syst) in pure heavy water and 7.30±0.07(stat)+1.40−1.02(syst) in NaCl-loaded heavy water. These results provide unique insights into this potential background source for experiments at SNOLAB
Dark Matter Search Results from the Complete Exposure of the PICO-60 C3F8 Bubble Chamber
(American Physical Society, 2019-07) Amole, Chanpreet; Levine, Ilan
Final results are reported from operation of the PICO-60 C3F8 dark matter detector, a bubble chamber filled with 52 kg of C3F8 located in the SNOLAB underground laboratory. The chamber was operated at thermodynamic thresholds as low as 1.2 keV without loss of stability. A new blind 1404-kg-day exposure at 2.45 keV threshold was acquired with approximately the same expected total background rate as the previous 1167-kg-day exposure at 3.3 keV. This increased exposure is enabled in part by a new optical tracking analysis to better identify events near detector walls, permitting a larger fiducial volume. These results set the most stringent direct-detection constraint to date on the weakly interacting massive particle (WIMP)-proton spin-dependent cross section at 3.2×10-41 cm2 for a 25 GeV WIMP, improving on previous PICO results for 3-5 GeV WIMPs by an order of magnitude.
Dark Matter Spin-Dependent Limits for WIMP Interactions on 19F by PICASSO
(Elsevier, 2009-11) Archambault, S.; Aubin, F.; Auger, M.; Behnke, Ed; Beltran, B.; Clark, K.; Dai, X.; Davour, A.; Farine, J.; Faust, R.; Genest, M.-H.; Giroux, G.; Gornea, R.; Krauss, C.; Kumaratunga, S.; Lawson, I.; Leroy, C.; Lessard, L.; Levy, C.; Levine, Ilan; MacDonald, R.; Martin, J.-P.; Nadeau, P.; Noble, A.; Piro, M.-C.; Pospisil, S.; Shephed, T.; Starinski, N.; Stekl, I.; Storey, C.; Wichoski, U.; Zacek, V.
The PICASSO experiment at SNOLAB reports new results for spin-dependent WIMP interactions on 19F using the superheated droplet technique. A new generation of detectors and new features which enable background discrimination via the rejection of non-particle induced events are described. First results are presented for a subset of two detectors with target masses of 19F of 65 g and 69 g respectively and a total exposure of 13.75 ± 0.48 kgd. No dark matter signal was found and for WIMP masses around 24 GeV/c2 new limits have been obtained on the spin-dependent cross section on 19F of oF = 13.9 pb (90% C.L.) which can be converted into cross section limits on protons and neutrons of op = 0.16 pb and on = 2.60 pb respectively (90% C.L). The obtained limits on pro-tons restrict recent interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent interactions. Keywords: dark matter, WIMPS, superheated droplets, NOLABPACS:95.35.+d, 29.40.-n, 34.50.BW
Data-driven Modeling of Electron Recoil Nucleation in PICO C3F8 Bubble Chambers
(American Physical Society, 2019-10) Amole, Chanpreet; Levine, Ilan
The primary advantage of moderately superheated bubble chamber detectors is their simultaneous sensitivity to nuclear recoils from weakly interacting massive particle (WIMP) dark matter and insensitivity to electron recoil backgrounds. A comprehensive analysis of PICO gamma calibration data demonstrates for the first time that electron recoils in C3F8 scale in accordance with a new nucleation mechanism, rather than one driven by a hot spike as previously supposed. Using this semiempirical model, bubble chamber nucleation thresholds may be tuned to be sensitive to lower energy nuclear recoils while maintaining excellent electron recoil rejection. The PICO-40L detector will exploit this model to achieve thermodynamic thresholds as low as 2.8 keV while being dominated by single-scatter events from coherent elastic neutrino-nucleus scattering of solar neutrinos. In one year of operation, PICO-40L can improve existing leading limits from PICO on spin-dependent WIMP-proton coupling by nearly an order of magnitude for WIMP masses greater than 3 GeV c-2 and will have the ability to surpass all existing non-xenon bounds on spin-independent WIMP-nucleon coupling for WIMP masses from 3 to 40 GeV c-2
Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory
(American Physical Society, 2002-07) Ahmad, Q. R.; Levine, Ilan
Observations 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.
Discrimination of nuclear recoils from alpha particles with superheated liquids
(New Journal of Physics, 2008) Aubin, F.; Auger, M.; Genest, M.-H.; Giroux, G.; Gornea, R.; Faust, R.; Leroy, C.; Lessard, L.; Martin, J.-P.; Morlat, T.; Piro, M.-C.; Starinski, N.; Zacek, V.; Beltran, B.; Krauss, C. B.; Behnke, Ed; Levine, Ilan; Shepherd, T.; Nadeau, P.; Wichoski, U.; Pospisil, S.; Stekl, I.; Sodomka, J.; Clark, K.; Dai, X.; Davour, A.; Levy, C.; Noble, A. J.; Storey, C.
The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron induced recoils.
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 Alberto
We 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.
Electron Antineutrino Search at the Sudbury Neutrino Observatory
(American Physical Society, 2004) Aharmin, Bassam; Levine, Ilan
Upper 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.
Emergent Spacetime from Modular Motives
(Springer, 2008-12) Schimmrigk, Rolf
The program of constructing spacetime geometry from string theoretic modular forms is extended to Calabi-Yau varieties of dimensions two, three, and four, as well as higher rank motives. Modular forms on the worldsheet can be constructed from the geometry of spacetime by computing the L-functions associated to omega motives of Calabi-Yau varieties, generated by their holomorphic n−forms via Galois representations. The modular forms that emerge from the Ω−motive and other motives of the intermediate cohomology are related to characters of the underlying rational conformal field theory. The converse problem of constructing space from string theory proceeds in the class of diagonal theories by determining the motives associated to modular forms in the category of pure motives with complex multiplication. The emerging picture indicates that the L-function can be interpreted as a map from the geometric category of motives to the category of conformal field theories on the worldsheet.
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, Quentin
We 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.
Evidence for nonequilibrium proton emission in a low-energy heavy-ion reaction
(American Physical Society, 1999) DeYoung, Paul A.; Hinnefeld, Jerry
Correlation 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.
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.
Exploring the Low-Z Shore of the Island of Inversion at N=19
(American Physical Society, 2012-01) Christian, Gregory A.; Hinnefeld, Jerry
The technique of invariant mass spectroscopy has been used to measure, for the first time, the ground state energy of neutron-unbound 28F, determined to be a resonance in the 27F+n continuum at 220(50) keV. States in 28F were populated by the reactions of a 62MeV/u 29Ne beam impinging on a 288 mg/cm2 beryllium target. The measured 28F ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that p f shell intruder configurations play only a small role in the ground state structure of 28F and establishing a low-Z boundary of the island of inversion for N = 19 isotones. Keywords: Binding energies and masses; Single-particle levels and strength functions
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.
Final state interaction or a 3H excited state?
(American Physical Society, 2003) Rogachev, Grigoriy V.; Hinnefeld, Jerry
An 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.

Browse

Browsing Department of Physics and Astronomy by Type "Article"