47 research outputs found
Expected Performance of CryoArray
WIMP-nucleon cross sections below 10^(-9) pb may be probed by ton-scale
experiments with low thresholds and background rates ~20 events per year. An
array of cryogenic detectors ("CryoArray") could perform well enough to reach
this goal. Sufficient discrimination and background suppression of photons has
already been demonstrated. Reduction of neutron backgrounds may be achieved by
siting the experiment deep enough. Removal of the surface-electron backgrounds
alone has not yet been demonstrated, but the reductions required even for this
troublesome background are quite modest and appear achieveable.Comment: 4 pages, 2 figures. Talk at DM2002 Conference, Marina del Rey, CA,
Feb 20-22, 200
Accurate spline solutions of the Dirac equation with parity-nonconserving potential
The complete system of the B-spline solutions for the Dirac equation with the
parity-nonconserving (PNC) weak interaction effective potential is obtained.
This system can be used for the accurate evaluation of the radiative
corrections to the PNC amplitudes in the multicharged ions and neutral atoms.
The use of the scaling procedure allows for the evaluation of the PNC matrix
elements with relative accuracy .Comment: 7 page
Yet Another Extension of the Standard Model: Oases in the Desert?
We have searched for conceptually simple extensions of the standard model,
and describe here a candidate model which we find attractive. Our starting
point is the assumption that off-diagonal CKM mixing matrix elements are
directly related by lowest order perturbation theory to the quark mass
matrices. This appears to be most easily and naturally implemented by assuming
that all off-diagonal elements reside in the down-quark mass matrix. This
assumption is in turn naturally realized by introducing three generations of
heavy, electroweak-singlet down quarks which couple to the Higgs sector
diagonally in flavor, while mass-mixing off-diagonally with the light
down-quarks. Anomaly cancellation then naturally leads to inclusion of
electroweak vector-doublet leptons. It is then only a short step to completing
the extension to three generations of fundamental representations of E(6).
Assuming only that the third generation B couples to the Higgs sector at least
as strongly as does the top quark, the mass of the B is roughly estimated to
lie between 1.7 TeV and 10 TeV, with lower-generation quarks no heavier. The
corresponding guess for the new leptons is a factor two lower. Within the
validity of the model, flavor and CP violation are ``infrared'' in nature,
induced by semi-soft mass mixing terms, not Yukawa couplings. If the Higgs
couplings of the new quarks are flavor symmetric, then there necessarily must
be at least one ``oasis'' in the desert, induced by new radiative corrections
to the top quark and Higgs coupling constants, and roughly at 1000 TeV.Comment: LaTex, 40 page
Observation of a New J(PC)=1(+-) Isoscalar State in the Reaction Pi- Proton -> Omega Eta Neutron at 18 GeV/c
Results are presented on a partial wave analysis of the Omega Eta final state
produced in Pi- Proton interactions at 18 GeVc where Omega -> Pi+ Pi- Pi0, Pi0
-> 2 Gammas, and Eta -> 2 Gammas. We observe the previously unreported decay
mode Omega(1650) -> Omega Eta and a new 1(+-) meson state h1(1595) with a mass
M=1594(15)(+10)(-60) MeV/c^2 and a width Gamma=384(60)(+70)(-100) MeV/c^2. The
h1(1595) state exhibits resonant-like phase motion relative to the Omega(1650).Comment: Submitted to Physics Letters B Eight total pages including 11 figures
and 1 tabl
Relativistic Calculation of the Meson Spectrum: a Fully Covariant Treatment Versus Standard Treatments
A large number of treatments of the meson spectrum have been tried that
consider mesons as quark - anti quark bound states. Recently, we used
relativistic quantum "constraint" mechanics to introduce a fully covariant
treatment defined by two coupled Dirac equations. For field-theoretic
interactions, this procedure functions as a "quantum mechanical transform of
Bethe-Salpeter equation". Here, we test its spectral fits against those
provided by an assortment of models: Wisconsin model, Iowa State model,
Brayshaw model, and the popular semi-relativistic treatment of Godfrey and
Isgur. We find that the fit provided by the two-body Dirac model for the entire
meson spectrum competes with the best fits to partial spectra provided by the
others and does so with the smallest number of interaction functions without
additional cutoff parameters necessary to make other approaches numerically
tractable. We discuss the distinguishing features of our model that may account
for the relative overall success of its fits. Note especially that in our
approach for QCD, the resulting pion mass and associated Goldstone behavior
depend sensitively on the preservation of relativistic couplings that are
crucial for its success when solved nonperturbatively for the analogous
two-body bound-states of QED.Comment: 75 pages, 6 figures, revised content
An improved method for measuring muon energy using the truncated mean of dE/dx
The measurement of muon energy is critical for many analyses in large
Cherenkov detectors, particularly those that involve separating
extraterrestrial neutrinos from the atmospheric neutrino background. Muon
energy has traditionally been determined by measuring the specific energy loss
(dE/dx) along the muon's path and relating the dE/dx to the muon energy.
Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in
dE/dx values is quite large, leading to a typical energy resolution of 0.29 in
log10(E_mu) for a muon observed over a 1 km path length in the IceCube
detector. In this paper, we present an improved method that uses a truncated
mean and other techniques to determine the muon energy. The muon track is
divided into separate segments with individual dE/dx values. The elimination of
segments with the highest dE/dx results in an overall dE/dx that is more
closely correlated to the muon energy. This method results in an energy
resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This
technique is applicable to any large water or ice detector and potentially to
large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure
Lambda and Sigma0 Pair Production in Two-Photon Collisions at LEP
Strange baryon pair production in two-photon collisions is studied with the
L3 detector at LEP. The analysis is based on data collected at e+e-
centre-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated
luminosity of 844 pb-1. The processes gamma gamma -> Lambda Anti-lambda and
gamma gamma -> Sigma0 Anti-sigma0 are identified. Their cross sections as a
function of the gamma gamma centre-of-mass energy are measured and results are
compared to predictions of the quark-diquark model
Determination of alphaS from Hadronic Event Shapes in e+e- Annihilation at 192 < sqrt(s) < 208 GeV
Results are presented from a study of the structure of high energy hadronic
events recorded by the L3 detector at sqrt(s)>192 GeV. The distributions of
several event shape variables are compared to resummed O(alphaS^2) QCD
calculations. We determine the strong coupling constant at three average
centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements,
combined with previous L3 measurements at lower energies, demonstrate the
running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +-
0.0058, where the first uncertainty is experimental and the second is
theoretical
Inclusive D* Production in Two-Photon Collisions at LEP
Inclusive D^{*+-} production in two-photon collisions is studied with the L3
detector at LEP, using 683 pb^{-1} of data collected at centre-of-mass energies
from 183 to 208 GeV. Differential cross sections are determined as functions of
the transverse momentum and pseudorapidity of the D^{*+-} mesons in the
kinematic region 1 GeV < P_T < 12 GeV and |eta| < 1.4. The cross sections
sigma(e^+e^- -> e^+e^-D^{*+-}X) in this kinematical region is measured and the
sigma(e^+e^- -> e^+e^- cc{bar}X) cross section is derived. The measurements are
compared with next-to-leading order perturbative QCD calculations
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at sqrt(s) up to 209 GeV
A search for the lightest neutral CP-even and neutral CP-odd Higgs bosons of
the Minimal Supersymmetric Standard Model is performed using 216.6 pb-1 of data
collected with the L3 detector at LEP at centre-of-mass energies between 203
and 209 GeV. No indication of a signal is found. Including our results from
lower centre-of-mass energies, lower limits on the Higgs boson masses are set
as a function of tan(beta) for several scenarios. For tan(beta) greater than
0.7 they are mh > 84.5 GeV and mA > 86.3 GeV at 95% confidence level