6,785 research outputs found
Unravelling an Extra Neutral Gauge Boson at the LHC using Third Generation Fermions
We study the potential to use measurements of extra neutral gauge bosons (Z')
properties in pp collisions at the Large Hadron Collider to unravel the
underlying physics. We focus on the usefulness of third generation final states
(tau, b, t) in distinguishing between models with non-universal Z'-fermion
couplings. We present an update of discovery limits of Z's including the
2010-2011 LHC run and include models with non-universal couplings. We show how
ratios of sigma(pp -> Z' -> ttbar), sigma(pp -> Z' -> bbbar), and sigma(pp ->
Z' -> tau^+tau^-) to sigma(pp -> Z' -> mu^+mu^-) can be used to distinguish
between models and measure parameters of the models. Of specific interest are
models with preferential couplings, such as models with generation dependent
couplings. We also find that forward-backward asymmetry measurements with third
generation fermions in the final state could provide important input to
understanding the nature of the Z'. Understanding detector resolution and
efficiencies will be crucial for extracting results
Two gamma quarkonium and positronium decays with Two-Body Dirac equations of constraint dynamics
Two-Body Dirac equations of constraint dynamics provide a covariant framework
to investigate the problem of highly relativistic quarks in meson bound states.
This formalism eliminates automatically the problems of relative time and
energy, leading to a covariant three dimensional formalism with the same number
of degrees of freedom as appears in the corresponding nonrelativistic problem.
It provides bound state wave equations with the simplicity of the
nonrelativistic Schroedinger equation. Unlike other three-dimensional
truncations of the Bethe-Salpeter equation, this covariant formalism has been
thoroughly tested in nonperturbatives contexts in QED, QCD, and nucleon-nucleon
scattering. Here we continue the important studies of this formalism by
extending a method developed earlier for positronium decay into two photons to
tests on the sixteen component quarkonium wave function solutions obtained in
meson spectroscopy. We examine positronium decay and then the two-gamma
quarkonium decays of eta_c, eta'_c, chi_0c, chi_2c, and pi-zero The results for
the pi-zero, although off the experimental rate by 13%, is much closer than the
usual expectations from a potential model.Comment: 4 pages. Presented at Second Meeting of APS Topical Group on Hadron
Physics, Nashville, TN, Oct 22-24. Proceedings to be published by Journal of
Physics (UK), Conference Serie
Using Final State Pseudorapidities to Improve s-channel Resonance Observables at the LHC
We study the use of final state particle pseudorapidity for measurements of
s-channel resonances at the LHC. Distinguishing the spin of an s-channel
resonance can, in principle, be accomplished using angular distributions in the
centre-of-mass frame, possibly using a centre-edge asymmetry measurement, A_CE.
In addition, forward-backward asymmetry measurements, A_FB, can be used to
distinguish between models of extra neutral gauge bosons. In this note we show
how these measurements can be improved by using simple methods based on the
pseudorapidity of the final state particles and present the expected results
for A_FB and A_CE for several representative models.Comment: 6 pages, 4 figures, 1 table; typos fixed, improved visibility of
figures for greyscale printin
Strategic Experimentation: The Case of Poisson Bandits
This paper studies a game of strategic experimentation in which the players have access to two-armed bandits where the risky arm distributes lumpsum payoffs according to a Poisson process with unknown intensity. Because of free-riding, there is an inefficiently low level of experimentation in any equilibrium where the players use stationary Markovian strategies. We characterize the unique symmetric Markovian equilibrium of the game, which is in mixed strategies. A variety of asymmetric pure-strategy equilibria is then constructed for the special case where there are two players and the arrival of the first lump-sum fully reveals the quality of the risky arm. Equilibria where players switch finitely often between the roles of experimenter and free-rider all lead to the same pattern of information acquisition; the efficiency of these equilibria depends on the way players share the burden of experimentation among them. We show that at least for relatively pessimistic beliefs, even the worst asymmetric equilibrium is more efficient than the symmetric one. In equilibria where players switch roles infinitely often, they can acquire an approximately efficient amount of information, but the rate at which it is acquired still remains inefficient.strategic experimentation, two-armed bandit, poisson process, Bayesian learning, Markov perfect equilibrium, public goods
Many accelerating black holes
We show how the Weyl formalism allows metrics to be written down which
correspond to arbitrary numbers of collinear accelerating neutral black holes
in 3+1 dimensions. The black holes have arbitrary masses and different
accelerations and share a common acceleration horizon. In the general case, the
black holes are joined by cosmic strings or struts that provide the necessary
forces that, together with the inter black hole gravitational attractions,
produce the acceleration. In the cases of two and three black holes, the
parameters may be chosen so that the outermost black hole is pulled along by a
cosmic string and the inner black holes follow behind accelerated purely by
gravitational forces. We conjecture that similar solutions exist for any number
of black holes.Comment: 12 pages, LaTe
Pigs may need more protein
Results of trials indicate that meatmeal based rations of 18 to 20 per cent protein may improve carcase quality and give better returns
The Importance of the Temple in Understanding the Latter-Day Saint Nauvoo Experience: Then and Now
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