P. Cushman

Final report of the E821 muon anomalous magnetic moment measurement at BNL

We present the final report from a series of precision measurements of the muon anomalous magnetic moment, a(mu)=(g-2)/2. The details of the experimental method, apparatus, data taking, and analysis are summarized. Data obtained at Brookhaven National Laboratory, using nearly equal samples of positive and negative muons, were used to deduce a(mu)(Expt)=11659208.0(5.4)(3.3)x10(-10), where the statistical and systematic uncertainties are given, respectively. The combined uncertainty of 0.54 ppm represents a 14-fold improvement compared to previous measurements at CERN. The standard model value for a(mu) includes contributions from virtual QED, weak, and hadronic processes. While the QED processes account for most of the anomaly, the largest theoretical uncertainty, approximate to 0.55 ppm, is associated with first-order hadronic vacuum polarization. Present standard model evaluations, based on e(+)e(-) hadronic cross sections, lie 2.2-2.7 standard deviations below the experimental result.

Dark matter search results from the CDMS II experiment.

News from the Dark Side? Dark matter is thought to represent 85% of all matter in the universe and to have been responsible for the formation of structure in the early universe, but its nature is still a mystery. Ahmed et al. (p. 1619, published online 11 February; see the Perspective by Lang) describe the results from the completed Cryogenic Dark Matter Search (CDMS II) experiment, which searched for dark matter in the form of weakly interacting massive particles (WIMP). Two candidate signals were observed, whereas only one background event was expected. The probability of having two or more events from the background would have been 23%. The results of this analysis cannot be interpreted with confidence as evidence for WIMP interactions, but, at the same time, neither event can be ruled out as representing signal. Details of possible, but unlikely, detection events produced by dark matter are reported. Astrophysical observations indicate that dark matter constitutes most of the mass in our universe, but its nature remains unknown. Over the past decade, the Cryogenic Dark Matter Search (CDMS II) experiment has provided world-leading sensitivity for the direct detection of weakly interacting massive particle (WIMP) dark matter. The final exposure of our low-temperature germanium particle detectors at the Soudan Underground Laboratory yielded two candidate events, with an expected background of 0.9 ± 0.2 events. This is not statistically significant evidence for a WIMP signal. The combined CDMS II data place the strongest constraints on the WIMP-nucleon spin-independent scattering cross section for a wide range of WIMP masses and exclude new parameter space in inelastic dark matter models.Z. Ahmed, D.S. Akerib, S. Arrenberg, C.N. Bailey, D. Balakishiyeva, L. Baudis, D.A. Bauer, P.L. Brink, T. Bruch, R. Bunker, B. Cabrera, D.O. Caldwell, J. Cooley, P. Cushman, M. Daal, F. DeJongh, M.R. Dragowsky, L. Duong, S. Fallows, E. Figueroa-Feliciano, J. Filippini, M. Fritts, S.R. Golwala, D.R. Grant, J. Hall, R. Hennings-Yeomans, S.A. Hertel, D. Holmgren, L. Hsu, M.E. Huber, O. Kamaev, M. Kiveni, M. Kos, S.W. Leman, R. Mahapatra, V. Mandic, K.A. McCarthy, N. Mirabolfathi, D. Moore, H. Nelson, R.W. Ogburn, A. Phipps, M. Pyle, X. Qiu, E. Ramberg, W. Rau, A. Reisetter, 7 T. Saab, B. Sadoulet, 13 J. Sander, R.W. Schnee, D.N. Seitz, B. Serfass, K.M. Sundqvist, M. Tarka, P. Wikus, S. Yellin, 14 J. Yoo, B.A. Young, and J. Zhang (CDMS Collaboration) Division of Physics, Mathematics & Astronomy, California Institute of Technology, Pasadena, CA 91125, USA Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA Fermi National Accelerator Laboratory, Batavia, IL 60510, USA Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA Department of Physics, Queen’s University, Kingston, ON, Canada, K7L 3N6 Department of Physics, St. Olaf College, Northfield, MN 55057 USA Department of Physics, Santa Clara University, Santa Clara, CA 95053, USA Department of Physics, Southern Methodist University, Dallas, TX 75275, USA Department of Physics, Stanford University, Stanford, CA 94305, USA Department of Physics, Syracuse University, Syracuse, NY 13244, USA Department of Physics, Texas A & M University, College Station, TX 77843, USA Department of Physics, University of California, Berkeley, CA 94720, USA Department of Physics, University of California, Santa Barbara, CA 93106, USA Departments of Phys. & Elec. Engr., University of Colorado Denver, Denver, CO 80217, USA Department of Physics, University of Florida, Gainesville, FL 32611, USA School of Physics & Astronomy, University of Minnesota, Minneapolis, MN 55455, USA Physics Institute, University of Zürich, Winterthurerstr. 190, CH-8057, Switzerland Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA

Measurement of the negative muon anomalous magnetic moment to 0.7 ppm

The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 ppm (ppm) at the Brookhaven Alternating Gradient Synchrotron. This result is based on data collected in 2001, and is over an order of magnitude more precise than the previous measurement for the negative muon. The result a(mu(-))=11 659 214(8)(3) x 10(-10) (0.7 ppm), where the first uncertainty is statistical and the second is systematic, is consistent with previous measurements of the anomaly for the positive and the negative muon. The average of the measurements of the muon anomaly is a(mu)(exp)=11 659 208(6) x 10(-10) (0.5 ppm).

Results from a Low-Energy Analysis of the CDMS II Germanium Data

We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from weakly interacting massive particles (WIMPs) with masses below ∼10  GeV/c(2). This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9  GeV/c(2) and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments.

Precise Measurement of the Positive Muon Anomalous Magnetic Moment

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 10(-10) (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value.

Limits on Spin-Independent Interactions of Weakly Interacting Massive Particles with Nucleons from the Two-Tower Run of the Cryogenic Dark Matter Search

We report new results from the Cryogenic Dark Matter Search (CDMS II) at the Soudan Underground Laboratory. Two towers, each consisting of six detectors, were operated for 74.5 live days, giving spectrum-weighted exposures of 34 kg-d for germanium and 12 kg-d for silicon targets after cuts, averaged over recoil energies 10-100 keV for a WIMP mass of 60 GeV. A blind analysis was conducted, incorporating improved techniques for rejecting surface events. No WIMP signal exceeding expected backgrounds was observed. When combined with our previous results from Soudan, the 90% C.L. upper limit on the spin-independent WIMP-nucleon cross section is 1.6 x 10^{-43} cm^2 from Ge, and 3 x 10^{-42} cm^2 from Si, for a WIMP mass of 60 GeV. The combined limit from Ge (Si) is a factor of 2.5 (10) lower than our previous results, and constrains predictions of supersymmetric models.

Search for low-mass weakly interacting massive particles with SuperCDMS.

We report a first search for weakly interacting massive particles (WIMPs) using the background rejection capabilities of SuperCDMS. An exposure of 577 kg-days was analyzed for WIMPs with mass < 30 GeV/c2, with the signal region blinded. Eleven events were observed after unblinding. We set an upper limit on the spin-independent WIMP-nucleon cross section of 1.2e-42 cm2 at 8 GeV/c2. This result is in tension with WIMP interpretations of recent experiments and probes new parameter space for WIMP-nucleon scattering for WIMP masses < 6 GeV/c2.

First Results from the Cryogenic Dark Matter Search in the Soudan Underground Laboratory

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg-d of Ge net exposure after cuts for recoil energies between 10--100 keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. Using the standard dark-matter halo and nuclear-physics WIMP model, these data set the worlds lowest exclusion limits on the coherent WIMP-nucleon scalar cross-section for all WIMP masses above 15 GeV, ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4 x 10^{-43} cm^2 at a WIMP mass of 60 GeV.

New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment

R. Agnese, A.J. Anderson, T. Aramaki, M. Asai, W. Baker, D. Balakishiyeva, D. Barker, R. Basu Thakur, 23 D.A. Bauer, J. Billard, A. Borgland, M.A. Bowles, P.L. Brink, R. Bunker, B. Cabrera, D.O. Caldwell, R. Calkins, D.G. Cerdeno, H. Chagani, Y. Chen, J. Cooley, B. Cornell, P. Cushman, M. Daal, P.C.F. Di Stefano, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, M. Ghaith, G.L. Godfrey, S.R. Golwala, J. Hall, H.R. Harris, T. Hofer, D. Holmgren, L. Hsu, M.E. Huber, D. Jardin, A. Jastram, O. Kamaev, B. Kara, M.H. Kelsey, A. Kennedy, A. Leder, B. Loer, E. Lopez Asamar, P. Lukens, R. Mahapatra, V. Mandic, N. Mast, N. Mirabolfathi, R.A. Moffatt, J.D. Morales Mendoza, S.M. Oser, K. Page, W.A. Page, R. Partridge, M. Pepin, ∗ A. Phipps, K. Prasad, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, Y. Ricci, A. Roberts, H.E. Rogers, T. Saab, B. Sadoulet, 4 J. Sander, K. Schneck, R.W. Schnee, S. Scorza, B. Serfass, B. Shank, D. Speller, D. Toback, R. Underwood, S. Upadhyayula, A.N. Villano, B. Welliver, J.S. Wilson, D.H. Wright, S. Yellin, J.J. Yen, B.A. Young, and J. Zhang

Improved limit on the muon electric dipole moment

G.W. Bennett, B. Bousquet, H.N. Brown, G. Bunce, R.M. Carey, P. Cushman, G.T. Danby, P.T. Debevec, M. Deile, H. Deng, W. Deninger, S.K. Dhawan, V.P. Druzhinin, L. Duong, E. Efstathiadis, F.J.M. Farley, G.V. Fedotovich, S. Giron, F.E. Gray, D. Grigoriev, M. Grosse-Perdekamp, A. Grossmann, M.F. Hare, D.W. Hertzog, X. Huang, V.W. Hughes, M. Iwasaki, K. Jungmann, D. Kawall, M. Kawamura, B.I. Khazin, J. Kindem, F. Krienen, I. Kronkvist, A. Lam, R. Larsen, Y.Y. Lee, I. Logashenko, R. McNabb, W. Meng, J. Mi, J.P. Miller, Y. Mizumachi, W.M. Morse, D. Nikas, C.J.G. Onderwater, Y. Orlov, C.S. Özben, J.M. Paley, Q. Peng, C.C. Polly, J. Pretz, R. Prigl, G. zu Putlitz, T. Qian, S.I. Redin, O. Rind, B.L. Roberts, N. Ryskulov, S. Sedykh, Y.K. Semertzidis, P. Shagin, Yu.M. Shatunov, E.P. Sichtermann, E. Solodov, M. Sossong, A. Steinmetz, L.R. Sulak, C. Timmermans, A. Trofimov, D. Urner, P. von Walter, D. Warburton, D. Winn, A. Yamamoto and D. Zimmerman (Muon (g − 2) Collaboration) Department of Physics, Boston University, Boston, MA 02215 Brookhaven National Laboratory, Upton, NY 11973 Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia LEPP, Cornell University, Ithaca, NY 14853 Fairfield University, Fairfield, CT 06430 6 Kernfysisch Versneller Instituut, University of Groningen, NL-9747 AA, Groningen, The Netherlands 7 Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany 8 Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801 9 KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan Department of Physics, University. of Minnesota., Minneapolis, MN 55455 11 Science University of Tokyo, Tokyo, 153-8902, Japan 12 Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan 13 Department of Physics, Yale University, New Haven, CT 06520 † Deceased