| Date | Speaker |
|---|---|
| Special Seminar Wednesday, September 28 1:30 p.m. |
Areg Danagoulian, University of Illinois "Measurements of Real Compton Scattering Cross Sections at Jefferson Lab" Similar to elastic electron scattering, Compton Scattering on the proton at high momentum transfers (and high $p_\bot$) can be an effective method to study its short-distance structure. An experiment has been carried out to measure the cross sections for Real Compton Scattering (RCS) on the proton for 2.3-5.7 GeV electron beam energies and a wide distribution of large scattering angles. The 25 kinematic settings sampled a domain of $s=5-11 (GeV/c)^2$, $-t=2-7 (GeV/c)^2$ and $-u=0.5-6.5 (GeV/c)^2$. In addition, a measurement of longitudinal and transverse polarization transfer asymmetries was made at a $3.48~ GeV$ beam energy and a scattering angle of $\theta _{cm}=120^o$. These measurements were performed to test the existing theoretical mechanisms for this process as well as to determine RCS form factors, which are the first moments of the Generalized Parton Distributions (GPD). The experiment was conducted in Hall A of Thomas Jefferson National Accelerator Facility(Jefferson Lab). It used a polarized and unpolarized electron beam, a $6 \% $ copper radiator (to produce a photon beam), the Hall A liquid hydrogen target, a high resolution spectrometer with a focal plane polarimeter, and a photon hodoscope calorimeter. Results of the cross sections and polarization transfer measurements will be presented. |
| September 30 | Jianglai Liu, University of Maryland "The Strange Vector Current in the Nucleon - the G0 Forward Angle Experiment" The electro-magnetic (vector) current of strange quarks inside the nucleon is described by the strange electric and magnetic form factors, $G_E^s$ and $G_M^s$. They give the contributions of strange quarks to the charge and magnetization distributions of the nucleon, which solely arise from the sea of $s\bar s$. Elastic electron-proton scattering carries a small parity-violating (PV) asymmetry (typically a few ppm), arising from the interference between the electromagnetic and neutral weak interactions. This asymmetry is directly related to $G_{E}^s$ and $G_M^s$. $G^0$ is an experiment at Jefferson lab making precise measurements of this PV effect. Its forward angle phase was concluded last spring. This measurement yields linear combinations of $G_E^s$ and $G_M^s$ in 18 different $Q^2$ bins in the range of 0.12-1.0~(GeV/c)$^2$. The $G^0$ results, combined with measurements from other experiments, indicate that $G_E^s$ and $G_M^s$ are both likely non-zero. In this talk I will give a brief overview the PV electron-proton scattering program, then focus on the $G^0$ forward angle measurement, and present the data analysis and the results. The physics implications of the measurement will also be discussed. |
| October 14 | Prof. Guy Savard, University of Chicago and Argonne National Laboratory "High-precision mass measurements, Vud, and the CKM matrix unitarity" Superallowed Fermi decays yield the most precise value of Vud, the up-down quark mixing matrix element of the Cabbibo-Kobayashi- Maskawa (CKM) matrix. This rotation matrix between the weak eigenstates and the mass eigenstates of the quark is unitary within the 3-generation Standard Model and the most accurate test of its unitarity is coming from its top row. Critical to this test are the values of Vud and Vus, the accepted value of the latter having changed significantly over the last few years to improve the agreement with the unitarity condition. New capabilities in high-precision mass measurements on short- lived isotopes available with the CPT spectrometer at Argonne have allowed the Q-value of a number of these superallowed decays to be measured to high accuracy and yield significant discrepancies with the previously accepted Q value for these decays determined by nuclear reactions. All new measured Q values are higher than previously determined, increasing the ft value, and reducing the extracted Vud value. The status and consistency of these new measurements, together with the resulting changes in the value of Vud and the unitarity condition, will be reviewed. The conclusions that can be drawn at this point about the nuclear structure dependent corrections that are present in this determination of Vud will also be given. Additional measurements on the other superallowed emitters in the data set are in preparation and the expected near-term evolution of the acuracy of this CKM unitarity test will be presented. |
| October 21 | Prof. Gail McLaughlin, North Carolina State University "Neutrinos and the r-process" While the mechanism for producing the heaviest elements has been understood for half a century, the astrophysical site remains a mystery. I will consider and compare two possible sites - the neutrino driven wind of the type II supernovae and the outflow from accretion disks surrounding black holes. These disks are likely to form from either neutron star mergers or from the collapse of rapidly rotating massive stars. In either case there is a significant flux of neutrinos which will impact the neutron-to-proton ratio and thus the nucleosynthesis. I will discuss the role of the neutrinos and the prospects for obtaining an r-process in each environment. |
| Special Seminar Friday, October 28 3:00 p.m. |
Peter Fierlinger, LANL "Development of a Ultra-Cold Neutron Source at PSI" |
| November 4 | Dr. Richard Kessler, University of Chicago "The KTeV Measurement of |Vus|" |
| November 11 | Prof. Stanley Brodsky, Stanford University and SLAC "Novel QCD Phenomena and the Impact of AdS/CFT" |
| November 18 | Dr. Christopher Mauger, CIT "Studying geoneutrinos with KamLAND" |
| December 2 | Prof. Thomas Blum, University of Connecticut "Lattice calculation of hadronic contributions to the muon anomalous magnetic moment" |
| January 6 | Prof. Dan-Olof Riska, Helsinki Institute of Physics "Strangeness spin and magnetic moment and the s bar s components of the proton" |
| Special Seminar Wednesday, January 11 1:30 p.m. |
Prof. Bira van Kolck, University of Arizona "Hadronic Time-Reversal Violation" |
| January 13 | Prof. Yuri Kovchegov, Ohio State University "Saturation Physics Meets RHIC Data" |
| Special Seminar Wednesday, January 18 1:30 p.m. |
Prof. Keh-Fei Liu, University of Kentucky "Update of Finite Density and Mesoniums" |
| January 20 | Prof. Krishna Rajagopal, MIT "Cold, Dense (but not asymptotically dense) Quark Matter" |
| Special Seminar Tuesday, January 24 1:30 p.m. |
Prof. Gerry Garvey, Los Alamos National Laboratory "Status of MiniBooNE" |
| Special Seminar Wednesday, January 25 1:30 p.m. |
Prof. Gerry Brown, SUNY-Stony Brook "A Renormalization Group Approach to the Analysis of the CERN NA60 Dimuon Results" |
| February 3 | Dr. Jeffrey Nico, National Institute of Standards and Technology "Neutron Physics at NIST" |
| February 10 | Dr. William Marciano, Brookhaven National Laboratory "Neutron Decay, CKM Unitarity and the Bjorken Sum Rule" |
| February 17 | Prof. Dmitry Budker, UC Berkeley "Crossing the P's and T's and dotting the alpha - testing fundamental symmetries at Berkeley" |
| February 24 | Prof. Ryoichi Seki, CSUN and CIT "Many-body lattice calculation with effective field theory: thermal properties of low-density neutron matter" |
| Special Seminar Monday, February 27 12:00 p.m. |
Prof. Howard Baer, Florida State University "Direct, indirect and collider detection of neutralino dark matter" |
| March 10 | Prof. John Beacom, Ohio State University "The Diffuse Supernova Neutrino Background" The cosmic stellar birth rate can be measured by standard astronomical techniques. It can also be probed via the cosmic stellar death rate, though until recently, this was much less precise. However, recent results based on measured supernova rates, and importantly, also on the attendant diffuse fluxes of neutrinos and gamma rays, have become competitive, and a concordant history of stellar birth and death is emerging. The neutrino flux from all past core-collapse supernovae, while faint, is realistically within reach of detection in Super-Kamiokande, and a useful limit has already been set. I will discuss predictions for this flux, the prospects for neutrino detection, the implications for understanding core-collapse supernovae, and a new limit on the contribution of type-Ia supernovae to the diffuse gamma-ray background. |
| March 17 | Dr. Dan Melconian, University of Washington "Standard Model Tests of the Weak Interaction Using the Beta-decay of Laser-cooled Potassium" |
| March 31 | Prof. Maxim Pospelov, University of Victoria and Perimeter Institute "Electric dipole moments and particle physics: accessing TeV-scales at low energies" |
| April 7 | Prof. Michael Wiescher, University of Notre Dame "Break-out from the hot CNO cycles, the trigger of X-ray bursts" |
| April 14 | Prof. Andre de Gouvea, Northwestern University "On Determining the Neutrino Mass Hierarchy" Is the relatively isolated member of the neutrino mass spectrum heavier or lighter than the two closely-spaced members? This question --- the character of the neutrino mass hierarchy --- is of great theoretical interest. I will first review the "standard" method for addressing it via neutrino oscillations. This method requires that the currently unknown size of the U_{e3} element of the leptonic mixing matrix be sufficiently large, and will utterly fail in the limit U_{e3} very small. For this reason, I will explore alternative oscillation approaches that would still succeed even if U_{e3} vanishes. I describe several alternatives that require neither a nonzero U_{e3} nor the presence of significant matter effects. All include multiple percent-level neutrino oscillation measurements, usually involving muon-neutrino (or antineutrino) disappearance and very long baselines. Before concluding, I will also briefly discuss "non-oscillation" probes of the neutrino mass hierarchy. |
| April 21 | Prof. Sunil Golwala, CIT "Searching for WIMPs with CDMS and MKIDs" Weakly interacting massive particles (WIMPs) are one of the best candidates for the dark matter that makes up almost one-third of the universe's energy density. Direct searches for WIMP dark matter particles have become increasingly more sensitive in the past decade and will be an important probe of supersymmetry in the LHC era. We review the evidence for dark matter and discuss some of the techniques used to look for it, with a focus on recent results from the Cryogenic Dark Matter Search (CDMS). We also discuss new concepts we are exploring for dark matter detectors using microwave kinetic inductance detectors |
| April 28 | Prof. Tony Thomas, Jefferson Laboratory "Precision Electron Scattering at JLab: Recent Achievements and Future Plans" Precise studies with high energy electrons are essential if we are to understand how QCD gives rise to hadron and nuclear structure, if indeed it does! The program of research at Jefferson Lab is therefore a central component of the worldwide effort in nuclear physics. I will review some of the recent results obtained at Jefferson Lab as well as some of the exciting new measurements one may anticipate in the near future and following the 12 GeV Upgrade. |
| May 5 | Dr. Yannis Semertzidis, Brookhaven National Laboratory "Electric dipole moments in storage ring: the next generation of hadronic EDM experiments" EDM searches are great probes of physics beyond the standard model and of new CP-violating sources at high energy scales. A new method searching for an EDM in storage rings will be presented, applicable to deuteron, proton, ^3He, etc. The expected sensitivity is 10^-29 e-cm for the deuteron and about an order of magnitude smaller for the proton. |
| May 26 | Prof. Kai Martens, University of Utah From HiRes to TA: The Cosmic Ray Frontier in Utah The High Resolution Fly's Eye (HiRes) stopped taking data at the beginning of April this year. The Telescope Array (TA) will start taking data at the beginning of next year. Results from HiRes will be discussed as well as the status of TA. HiRes has seen the GZK cutoff, but not found large or small scale anisotropies in its data. A possible correlation with BL Lac objects need further investigation. |
| June 2 | Prof. Chen-Yu Liu, Indiana University |
| Special Seminar Monday, July 24 |
Dr. Keith Lee, MIT "Shape-Function Effects and Universality in B-> Xs 1+ 1-" |
| Special Seminar Wednesday, July 26 |
Dr. Brent Nelson, Northeastern University "Signatures of Exotic Quarks at the LHC" |
Leona Kershaw, 13 July 2006