245 research outputs found
Peer Pressure, Incentives, and Gender: an Experimental Analysis of Motivation in the Workplace
We present results from a real-effort experiment, simulating actual work-place conditions, comparing the productivity of workers under fixed wages and piece rates. Workers, who were paid to enter data, were exposed to different degrees of peer pressure under both payment systems. The peer pressure was generated in the form of private information about the productivity of their peers. We have two main results. First, we find no level of peer pressure for which the productivity of either male or female workers is significantly higher than productivity without peer pressure. Second, we find that very low and very high levels of peer pressure can significantly decrease productivity (particularly for men paid fixed wages). These results are consistent with models of conformism and self-motivation.Peer effects, fixed wages, piece rates, gender
Improved Nonrelativistic QCD for Heavy Quark Physics
We construct an improved version of nonrelativistic QCD for use in lattice
simulations of heavy quark physics, with the goal of reducing systematic errors
from all sources to below 10\%. We develop power counting rules to assess the
importance of the various operators in the action and compute all leading order
corrections required by relativity and finite lattice spacing. We discuss
radiative corrections to tree level coupling constants, presenting a procedure
that effectively resums the largest such corrections to all orders in
perturbation theory. Finally, we comment on the size of nonperturbative
contributions to the coupling constants.Comment: 40 pages, 2 figures (not included), in LaTe
Invariant Operators in Collinear Effective Theory
We consider processes which produce final state hadrons whose energy is much
greater than their mass. In this limit interactions involving collinear
fermions and gluons are constrained by a symmetry, and we give a general set of
rules for constructing leading and subleading invariant operators. Wilson
coefficients C(mu,P) are functions of a label operator P, and do not commute
with collinear fields. The symmetry is used to reproduce a two-loop result for
factorization in B -> D pi in a simple way.Comment: 11 pages, 2 figs, journal versio
Power corrections in e+ e- --> pi+ pi-, K+ K- and B --> K pi, pi pi
CLEO-c measurements of the timelike form factors F_pi, F_K at \sqrt{s}=3.671
GeV provide a direct probe of power corrections (PC's) at energies near m_B.
PC's in F_pi, F_K and B \to K pi, pi pi are separated into perturbative and
soft parts. In F_pi, F_K the latter are \ge O(10) larger. A PC fit to the B \to
K pi, pi pi data also yields a \ge O(10) soft-to-perturbative hierarchy for the
QCD penguin PC's. Hence, both can be attributed to dominance of the soft-ovelap
between energetic (approximately) back-to-back collinear partons, and
consistency of the B\to K pi, pi pi fit with the Standard Model appears to be
naturally realized. The CP asymmetries S_{K_s pi^0}, C_{K_s pi^0} are well
determined, providing a clean test for new physics.Comment: 4 pages, 4 figures, version published in Eur. Phys. J. C; elaborated
on the connection between power corrections in e+e- ->M1 M2 and the B-> M1 M2
QCD penguin amplitudes; removed speculation that soft-overlaps are much
larger for PP than for VP and VV final states, this is not supported by a new
analysis in preparatio
Nonleptonic B decays into two light mesons in soft-collinear effective theory
We consider nonleptonic B decays into two light mesons at leading order in
soft-collinear effective theory, and show that the decay amplitudes are
factorized to all orders in alpha_s. The operators for nonleptonic B decays in
the full theory are first matched to the operators in SCET_I, which is the
effective theory appropriate for sqrt{m_b Lambda} <mu <m_b with Lambda~0.5 GeV.
We evolve the operators and the relevant time-ordered products in SCET_I to
SCET_II, which is appropriate for mu < sqrt{m_b Lambda}. Using the
gauge-invariant operators in SCET_II, we compute nonleptonic B decays in SCET,
including the nonfactorizable spectator contributions and spectator
contributions to the heavy-to-light form factor. As an application, we present
the decay amplitudes for B ->pi,pi in soft-collinear effective theory.Comment: 42 pages, 5 figures, 2 tables Major revision of the manuscript. The
idea of using SCET_I, and SCET_II is clearly presented. Some of the
calculational steps are explicitly show
Quantum Newtonian Dynamics on a Light Front
We recall the special features of quantum dynamics on a light-front (in an
infinite momentum frame) in string and field theory. The reason this approach
is more effective for string than for fields is stressed: the light-front
dynamics for string is that of a true Newtonian many particle system, since a
string bit has a fixed Newtonian mass. In contrast, each particle of a field
theory has a variable Newtonian mass P^+, so the Newtonian analogy actually
requires an infinite number of species of elementary Newtonian particles. This
complication substantially weakens the value of the Newtonian analogy in
applying light-front dynamics to nonperturbative problems. Motivated by the
fact that conventional field theories can be obtained as infinite tension
limits of string theories, we propose a way to recast field theory as a
standard Newtonian system. We devise and analyze some simple quantum mechanical
systems that display the essence of the proposal, and we discuss prospects for
applying these ideas to large N_c QCD.Comment: 13 pages, 3 figures, LaTex, psfig, references added, APS copyrigh
Status of heavy quark physics from the lattice
In this short review, I present a summary of various methods used to simulate
heavy quarks on the lattice. I mainly focus on effectives theories, and give
some physical results.Comment: Talk given at QCD06, Montpellier July 06, 6 pages, 2 figures,
espcrc2.st
Symmetry-breaking corrections to heavy-to-light B meson form factors at large recoil
Recently it has been shown that symmetries emerging in the heavy quark and
large recoil energy limit impose various relations on form factors that
parametrise the decay of B mesons into light mesons. These symmetries are
broken by perturbative effects. In this paper we discuss the structure of
heavy-to-light form factors including such effects and compute
symmetry-breaking corrections to first order in the strong coupling. As an
application of our results we consider the forward-backward asymmetry zero in
the rare decay B -> V l^+ l^- and the possibility to constrain potential new
physics contributions to the Wilson coefficient C_9.Comment: 30 pages, LaTeX (typos in eq. (44), (46) corrected
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