1,497 research outputs found
Diphoton Background to Higgs Boson Production at the LHC with Soft Gluon Effects
The detection and the measurement of the production cross section of a light
Higgs boson at the CERN Large Hadron Collider demand the accurate prediction of
the background distributions of photon pairs. To improve this theoretical
prediction, we present the soft-gluon resummed calculation of the cross section, including the exact one loop contribution. By incorporating the known fixed order results and the
leading terms in the higher order corrections, the resummed cross section
provides a reliable prediction for the inclusive diphoton invariant mass and
transverse momentum distributions. Given our results, we propose the search for
the Higgs boson in the inclusive diphoton mode with a cut on the transverse
momentum of the photon pair, without the requirement of an additional tagged
jet.Comment: 5 pages, 4 figures. A figure with discussion, and a reference added.
Minor improvements of wording. Conclusion unchange
Reentrant Kondo effect in Landau quantized graphene
We have studied the interplay of an Anderson impurity in Landau quantized
graphene, with special emphasis on the influence of the chemical potential.
Within the slave-boson mean-field theory, we found reentrant Kondo behaviour by
varying the chemical potential or gate voltage. Between Landau levels, the
density of states is suppressed, and by changing the graphene's Fermi energy,
we cross from metallic to semiconducting regions. Hence, the corresponding
Kondo behaviour is also influenced. The f-level spectral function reveals both
the presence of Landau levels in the conduction band and the Kondo resonance.Comment: 8 pages, 6 figure
Unusual hyperfine interaction of Dirac electrons and NMR spectroscopy in graphene
Theory of nuclear magnetic resonance (NMR) in graphene is presented. The
canonical form of the electron-nucleus hyperfine interaction is strongly
modified by the linear electronic dispersion. The NMR shift and spin-lattice
relaxation time are calculated as function of temperature, chemical potential,
and magnetic field and three distinct regimes are identified: Fermi-,
Dirac-gas, and extreme quantum limit behaviors. A critical spectrometer
assessment shows that NMR is within reach for fully 13C enriched graphene of
reasonable size.Comment: 5 pages, 3 figure
Higgs Boson Production at the LHC with Soft Gluon Effects
We present results of QCD corrections to Higgs boson production at the CERN Large Hadron Collider. Potentially large logarithmic contributions from multiple soft-gluon emission are summed up to all order in the strong coupling. Various kinematical distributions, including the Higgs transverse momentum, are predicted with O(alpha_s^3) precision. Comparison is made to outputs of the popular Monte Carlo event generator PYTHIA
The Fermi edge singularity in the SU(N) Wolff model
The low temperature properties of the SU(N) Wolff impurity model are studied
via Abelian bosonization. The path integral treatment of the problem allows for
an exact evaluation of low temperature properties of the model. The single
particle Green's function enhances due to the presence of local correlation.
The basic correlation function such as the charge or spin correlator are also
influenced by the presence of impurity, and show local Fermi liquid behaviour.
The X-ray absorption is affected by the presence of local Hubbard interaction.
The exponent is decreased (increased) for repulsive (attractive) interactions.Comment: 7 pages, 4 figure
Non-perturbative effects and the resummed Higgs transverse momentum distribution at the LHC
We investigate the form of the non-perturbative parameterization in both the
impact parameter (b) space and transverse momentum (p_T) space resummation
formalisms for the transverse momentum distribution of single massive bosons
produced at hadron colliders. We propose to analyse data on Upsilon
hadroproduction as a means of studying the non-perturbative contribution in
processes with two gluons in the initial state. We also discuss the theoretical
errors on the resummed Higgs transverse momentum distribution at the LHC
arising from the non-perturbative contribution.Comment: 22 pages, 10 figure
Broad metabolic sensitivity profiling of a prototrophic yeast deletion collection
Background: Genome-wide sensitivity screens in yeast have been immensely popular following the construction of a collection of deletion mutants of non-essential genes. However, the auxotrophic markers in this collection preclude experiments on minimal growth medium, one of the most informative metabolic environments. Here we present quantitative growth analysis for mutants in all 4,772 non-essential genes from our prototrophic deletion collection across a large set of metabolic conditions. Results: The complete collection was grown in environments consisting of one of four possible carbon sources paired with one of seven nitrogen sources, for a total of 28 different well-defined metabolic environments. The relative contributions to mutants' fitness of each carbon and nitrogen source were determined using multivariate statistical methods. The mutant profiling recovered known and novel genes specific to the processing of nutrients and accurately predicted functional relationships, especially for metabolic functions. A benchmark of genome-scale metabolic network modeling is also given to demonstrate the level of agreement between current in silico predictions and hitherto unavailable experimental data. Conclusions: These data address a fundamental deficiency in our understanding of the model eukaryote Saccharomyces cerevisiae and its response to the most basic of environments. While choice of carbon source has the greatest impact on cell growth, specific effects due to nitrogen source and interactions between the nutrients are frequent. We demonstrate utility in characterizing genes of unknown function and illustrate how these data can be integrated with other whole-genome screens to interpret similarities between seemingly diverse perturbation types
Gluon-gluon contributions to the production of continuum diphoton pairs at hadron colliders
We compute the contributions to continuum photon pair production at hadron
colliders from processes initiated by gluon-gluon and gluon-quark scattering
into two photons through a four-leg virtual quark loop. Complete two-loop cross
sections in perturbative quantum chromodynamics are combined with contributions
from soft parton radiation resummed to all orders in the strong coupling
strength. The structure of the resummed cross section is examined in detail,
including a new type of unintegrated parton distribution function affecting
azimuthal angle distributions of photons in the pair's rest frame. As a result
of this analysis, we predict diphoton transverse momentum distributions in
gluon-gluon scattering in wide ranges of kinematic parameters at the Fermilab
Tevatron collider and the CERN Large Hadron Collider.Comment: 28 pages, 11 figures; published versio
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