The Pattern of the Mineralization of Enamel

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68291/2/10.1177_00220345610400050101.pd

Pion photoproduction on the nucleon in the quark model

We present a detailed quark-model study of pion photoproduction within the effective Lagrangian approach. Cross sections and single-polarization observables are investigated for the four charge channels, $\gamma p\to \pi^+ n$, $\gamma n\to \pi^- p$, $\gamma p\to \pi^0 p$, and $\gamma n\to \pi^0 n$. Leaving the $\pi N\Delta$ coupling strength to be a free parameter, we obtain a reasonably consistent description of these four channels from threshold to the first resonance region. Within this effective Lagrangian approach, strongly constrainted by the quark model, we consider the issue of double-counting which may occur if additional {\it t}-channel contributions are included.Comment: Revtex, 35 pages, 16 eps figures; version to appear on PR

Angular analysis of the decay B0→K*0μ+μ- from pp collisions at s=8 TeV

The angular distributions and the differential branching fraction of the decay B0→K⁎(892)0μ+μ− are studied using data corresponding to an integrated luminosity of 20.5 fb −1 collected with the CMS detector at the LHC in pp collisions at s=8 TeV . From 1430 signal decays, the forward–backward asymmetry of the muons, the K⁎(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions

Search for the production of an excited bottom quark decaying to tW in proton-proton collisions at root s=8 TeV

Peer reviewe

Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at √sNN=2.76 TeV

Interactions between jets and the quark-gluon plasma produced in heavy ion collisions are studied via the angular distributions of summed charged-particle transverse momenta (pT) with respect to both the leading and subleading jet axes in high-pT dijet events. The contributions of charged particles in different momentum ranges to the overall event pT balance are decomposed into short-range jet peaks and a long-range azimuthal asymmetry in charged-particle pT. The results for PbPb collisions are compared to those in pp collisions using data collected in 2011 and 2013, at collision energy √ sNN = 2.76 TeV with integrated luminosities of 166 µb −1 and 5.3 pb−1 , respectively, by the CMS experiment at the LHC. Measurements are presented as functions of PbPb collision centrality, charged-particle pT, relative azimuth, and radial distance from the jet axis for balanced and unbalanced dijets

Search for supersymmetry in the vector-boson fusion topology in proton-proton collisions at √s = 8 TeV

The first search for supersymmetry in the vector-boson fusion topology is presented. The search targets final states with at least two leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 19.7 fb −1 of proton-proton collisions at s = 8 s√=8 TeV collected with the CMS detector at the CERN LHC. The observed dijet invariant mass spectrum is found to be consistent with the expected standard model prediction. Upper limits are set on the cross sections for chargino and neutralino production with two associated jets, assuming the supersymmetric partner of the τ lepton to be the lightest slepton and the lightest slepton to be lighter than the charginos. For a so-called compressed-mass-spectrum scenario in which the mass difference between the lightest supersymmetric particle χ ˜ 1 0 χ~01 and the next lightest, mass-degenerate, gaugino particles χ ˜ 2 0 χ~02 and χ ˜ 1 ± χ~±1 is 50 GeV, a mass lower limit of 170 GeV is set for these latter two particles

Meson factories, pi meson delivery, and pi meson dosimetry for cancer therapy

The meson therapy research program at the Los Alamos Meson Physics Facility (LAMPF) is briefly described. It is stated that tests will start on a magnetic collection channel for pions at LAMPF within one or two months, and the biomedical pion channel is described. The problems encountered in pion dosimetry are briefly discussed. (WDK

Possible pion sources for radiotherapy

From second meeting on fundamental and practical aspects of the application of fast neutrons in clinical radiotherapy; The Hague, Netherlands (3 Oct 1973). Recently great interest has been shown in pi-meson irradiation as a possible modality for cancer radiation therapy. In order for this short-lived particle to be more than an idle laboratory curiosity, it must be demonstrated that economical pion sources can be built, which satisfy the necessary flux requirements for therapy within reasonable space and cost limitations. Protons have a much higher probability for producing pions per unit target mass than do electrons, so if there were no other consideration it is clear that proton accelerators would be superior to electron accelerators as pion sources. Unfortunately, proton accelerators are considerably more difficult to build than electron accelerators, requiring more precise control, more rf power, and probably more length than their counterparts. At 500-MeV the advantage of protons over electrons for production is about a factor of 50, that is, for the same total yield of pions, an electron accelerator must have 50 times the beam power required of an equivalent proton machine. One possible way around this problem is to design a much more efficient magnetic channel to collect the pions and focus them on the patient being treated. Such a system has been designed that utilizes 60 parallel magnetic spectrometers to focus a total of 1/12 the total pions produced in the pion production target on the patient. This system requires a more sophisticated control system, but is certainly an indicator of a direction to go to reduce source cost. This approach also reduces the beam current requirements on a proton accelerator by a factor of 30 making a 30 microamp accelerator a possibility. A brief description of four accelerator systems that might be suitable for hospital use, two electron accelerators, and two proton accelerators, is given to illustrate the problems involved. (CH