6,696 research outputs found
Production of scalar and pseudo-scalar Higgs bosons to next-to-next-to-leading order at hadron colliders
We consider the production of intermediate-mass CP-even and CP-odd Higgs
bosons in proton-proton and proton-anti-proton collisions. We extend the
recently published results for the complete next-to-next-to-leading order
calculation for a scalar Higgs boson to the pseudo-scalar case and present
details of the calculation that might be useful for similar future
investigations. The result is based on an expansion in the limit of a heavy top
quark mass and a subsequent matching to the expression obtained in the limit of
infinite energy. For a Higgs boson mass of 120 GeV the deviation from the
infinite-top quark mass result is small. For 300 GeV, however, the
next-to-next-to-leading order corrections for a scalar Higgs boson exceed the
effective-theory result by about 9% which increases to 22% in the pseudo-scalar
case. Thus in this mass range the effect on the total cross section amounts to
about 2% and 6%, respectively, which may be relevant in future precision
studies.Comment: 29 page
Finite top quark mass effects in NNLO Higgs boson production at LHC
We present next-to-next-to-leading order corrections to the inclusive
production of the Higgs bosons at the CERN Large Hadron Collider (LHC)
including finite top quark mass effects. Expanding our analytic results for the
partonic cross section around the soft limit we find agreement with a very
recent publication by Harlander and Ozeren \cite{Harlander:2009mq}.Comment: 15 page
Molecules Near Absolute Zero and External Field Control of Atomic and Molecular Dynamics
This article reviews the current state of the art in the field of cold and
ultracold molecules and demonstrates that chemical reactions, inelastic
collisions and dissociation of molecules at subKelvin temperatures can be
manipulated with external electric or magnetic fields. The creation of
ultracold molecules may allow for spectroscopy measurements with extremely high
precision and tests of fundamental symmetries of nature, quantum computation
with molecules as qubits, and controlled chemistry. The probability of chemical
reactions and collisional energy transfer can be very large at temperatures
near zero Kelvin. The collision energy of ultracold atoms and molecules is much
smaller than perturbations due to interactions with external electric or
magnetic fields available in the laboratory. External fields may therefore be
used to induce dissociation of weakly bound molecules, stimulate forbidden
electronic transitions, suppress the effect of centrifugal barriers in outgoing
reaction channels or tune Feshbach resonances that enhance chemical reactivity
Top-mass effects in differential Higgs production through gluon fusion at order \alpha_s^4
Effects from a finite top quark mass on differential distributions in the
Higgs+jet production cross section through gluon fusion are studied at
next-to-leading order in the strong coupling, i.e. . Terms
formally subleading in are calculated, and their influence on the
transverse momentum and rapidity distribution of the Higgs boson are evaluated.
We find that, for the differential K-factor, the heavy-top limit is valid at
the 2-3% level as long as the transverse momentum of the Higgs remains below
about 150 GeV.Comment: 21 pages, 12 figure
Heavy-quark mass effects in Higgs boson production at the LHC
We study the impact of heavy-quark masses in Higgs boson production through
gluon fusion at the LHC. We extend previous computations of the fully
differential cross section and of the transverse momentum spectrum of the Higgs
boson by taking into account the finite top- and bottom-quark masses up to
O(alpha_S^3). We also discuss the issues arising when the heavy-quark mass is
much smaller than the Higgs mass. Our results are implemented in updated
versions of the HNNLO and HRes numerical programs.Comment: Minor modifications, results unchanged. Discussion on uncertainties
added. Version published on JHE
NLO QCD bottom corrections to Higgs boson production in the MSSM
We present a calculation of the two-loop bottom-sbottom-gluino contributions
to Higgs boson production via gluon fusion in the MSSM. The calculation is
based on an asymptotic expansion in the masses of the supersymmetric particles,
which are assumed to be much heavier than the bottom quark and the Higgs
bosons. We obtain explicit analytic results that allow for a straightforward
identification of the dominant contributions in the NLO bottom corrections. We
emphasize the interplay between the calculations of the masses and the
production cross sections of the Higgs bosons, discussing sensible choices of
renormalization scheme for the parameters in the bottom/sbottom sector.Comment: 25 pages, 4 figures. v2: references and two figures added, version
published in JHE
COMPARATIVE EVALUATION OF ORAL MICROBIOTA OF CHILDREN WITH AND WITHOUT EARLY CHILDHOOD CARIES BORN TO CARIES FREE MOTHERS
Objectives: To compare the level of mutans streptococci in children with and without Early childhood caries (ECC) born to caries free mothers.Methods: Twenty children aged between 3 and 6 years were selected depending on their caries experience, and the mother should be caries free inboth the groups. The children were divided into two groups. Group I had an active carious lesion and Group II were caries free. Saliva samples werecollected from the child and the mother in a sterile tube and bacterial culture was carried out to estimate the colony count.Results: There was a highly significant difference in the colony forming unit (CFU) between the 2 groups, indicating higher CFU in children with ECC.Conclusions: Even though there are higher chances of vertical transmission of MS from mother to their child, this study provides a new view thatmother alone is not a potential factor for mutans streptococci transmission to their child.Keywords: Mutans streptocci, Early childhood caries, Colony forming unit
NNLO phase space master integrals for two-to-one inclusive cross sections in dimensional regularization
We evaluate all phase space master integrals which are required for the total
cross section of generic 2 -> 1 processes at NNLO as a series expansion in the
dimensional regulator epsilon. Away from the limit of threshold production, our
expansion includes one order higher than what has been available in the
literature. At threshold, we provide expressions which are valid to all orders
in terms of Gamma functions and hypergeometric functions. These results are a
necessary ingredient for the renormalization and mass factorization of
singularities in 2 -> 1 inclusive cross sections at NNNLO in QCD.Comment: 37 pages, plus 3 ancillary files containing analytic expressions in
Maple forma
Self-Modification of Policy and Utility Function in Rational Agents
Any agent that is part of the environment it interacts with and has versatile
actuators (such as arms and fingers), will in principle have the ability to
self-modify -- for example by changing its own source code. As we continue to
create more and more intelligent agents, chances increase that they will learn
about this ability. The question is: will they want to use it? For example,
highly intelligent systems may find ways to change their goals to something
more easily achievable, thereby `escaping' the control of their designers. In
an important paper, Omohundro (2008) argued that goal preservation is a
fundamental drive of any intelligent system, since a goal is more likely to be
achieved if future versions of the agent strive towards the same goal. In this
paper, we formalise this argument in general reinforcement learning, and
explore situations where it fails. Our conclusion is that the self-modification
possibility is harmless if and only if the value function of the agent
anticipates the consequences of self-modifications and use the current utility
function when evaluating the future.Comment: Artificial General Intelligence (AGI) 201
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