2,077 research outputs found
Intrinsic bottom and its impact on heavy new physics at the LHC
Heavy quark parton distribution functions (PDFs) play an important role in
several Standard Model and New Physics processes. Most analyses rely on the
assumption that the charm and bottom PDFs are generated perturbatively by gluon
splitting and do not involve any non-perturbative degrees of freedom. On the
other hand, non- perturbative, intrinsic heavy quark parton distributions have
been predicted in the literature. We demonstrate that to a very good
approximation the scale-evolution of the intrinsic heavy quark content of the
nucleon is governed by non-singlet evolution equations. This allows to analyze
the intrinsic heavy quark distributions without having to resort to a
full-fledged global analysis of parton distribution functions. We exploit this
freedom to model intrinsic bottom distributions which are so far missing in the
literature. We estimate the impact of the non-perturbative contribution to the
charm and bottom-quark PDFs and on several important parton-parton luminosities
at the LHC.Comment: 6 pages, proceedings of POETIC VI: 6th International conference on
Physics Opportunities at Electron-Ion collider. arXiv admin note: substantial
text overlap with arXiv:1507.0893
The lessons from QE and other 'unconventional' monetary policies - evidence from the Bank of England
This paper investigates the effectiveness of the ‘quantitative easing’ policy, as implemented by the Bank of England in March 2009. Similar policies had been previously implemented in Japan, the U.S. and the Eurozone. The effectiveness is measured by the impact of Bank of England policies (including, but not limited to QE) on nominal GDP growth – the declared goal of the policy, according to the Bank of England. Unlike the majority of the literature on the topic, the general-to-specific econometric modeling methodology (a.k.a. the ‘Hendry’ or ‘LSE’ methodology) is employed for this purpose. The empirical analysis indicates that QE as defined and announced in March 2009 had no apparent effect on the UK economy. Meanwhile, it is found that a policy of ‘quantitative easing’ defined in the original sense of the term (Werner, 1994) is supported by empirical evidence: a stable relationship between a lending aggregate (disaggregated M4 lending, i.e. bank credit for GDP transactions) and nominal GDP is found. The findings imply that BoE policy should more directly target the growth of bank credit for GDP-transactions
PyR@TE: Renormalization Group Equations for General Gauge Theories
Although the two-loop renormalization group equations for a general gauge
field theory have been known for quite some time, deriving them for specific
models has often been difficult in practice. This is mainly due to the fact
that, albeit straightforward, the involved calculations are quite long, tedious
and prone to error. The present work is an attempt to facilitate the practical
use of the renormalization group equations in model building. To that end, we
have developed two completely independent sets of programs written in Python
and Mathematica, respectively. The Mathematica scripts will be part of an
upcoming release of SARAH 4. The present article describes the collection of
Python routines that we dubbed PyR@TE which is an acronym for "Python
Renormalization group equations At Two-loop for Everyone". In PyR@TE, once the
user specifies the gauge group and the particle content of the model, the
routines automatically generate the full two-loop renormalization group
equations for all (dimensionless and dimensionful) parameters. The results can
optionally be exported to Latex and Mathematica, or stored in a Python data
structure for further processing by other programs. For ease of use, we have
implemented an interactive mode for PyR@TE in form of an IPython Notebook. As a
first application, we have generated with PyR@TE the renormalization group
equations for several non-supersymmetric extensions of the Standard Model and
found some discrepancies with the existing literature.Comment: 33 page
Electroweak top-quark pair production at the LHC with bosons to NLO QCD in POWHEG
We present the calculation of the NLO QCD corrections to the electroweak
production of top-antitop pairs at the CERN LHC in the presence of a new
neutral gauge boson. The corrections are implemented in the parton shower Monte
Carlo program POWHEG. Standard Model (SM) and new physics interference effects
are properly taken into account. QED singularities, first appearing at this
order, are consistently subtracted. Numerical results are presented for SM and
total cross sections and distributions in invariant mass, transverse
momentum, azimuthal angle and rapidity of the top-quark pair. The remaining
theoretical uncertainty from scale and PDF variations is estimated, and the
potential of the charge asymmetry to distinguish between new physics models is
investigated for the Sequential SM and a leptophobic topcolor model.Comment: 33 pages, 15 figures, 1 table. Discussion added on uncertainties from
parton showers and NLL contribution
Frontiers of QCD with Precision nPDFs
Searches for new physics will increasingly depend on identifying deviations
from precision Standard Model (SM) predictions. Quantum Chromodynamics (QCD)
will necessarily play a central role in this endeavor as it provides the
framework for the parton model. However, as we move to higher orders and into
extreme kinematic regions, we begin to see the full complexities of the QCD
theory. Recent theoretical developments improve our ability to analyze both
proton and nuclear PDFs across the full kinematic range. These developments are
incorporated into the new nCTEQ15 PDFs, and we review these developments with
respect to future measurements, and identify areas where additional effort is
required.Comment: Published in the "6th International conference on Physics
Opportunities at Electron-Ion colliders (POETIC6)
NLO+NLL limits on and gauge boson masses
QCD resummation predictions for the production of new charged () and
neutral () heavy gauge bosons decaying leptonically are presented. These
results are obtained with our resummation code at next-to-leading order and
next-to-leading logarithmic (NLO+NLL) accuracy. Our predictions are compared to
PYTHIA at leading order (LO) supplemented with parton showers (PS) and FEWZ at
NLO and next-to-next-to-leading order (NNLO) for the -differential and
total cross sections in the Sequential Standard Model (SSM) and general
SU(2)SU(2)U(1) models. We show that the importance of
resummation for total cross sections increases with the gauge boson mass.
Finally, the latest ATLAS and CMS results are reinterpreted to derive new
limits at NLO+NLL on and boson masses in general extensions of the
Standard Model.Comment: Proceeding of the XXIII International Workshop on Deep Inelastic
Scattering and Related Subjects, April 27 - May 1, 2015, Southern Methodist
University, Dallas, Texa
St. Paul: Liberty and Law
Stanislas Lyonnet, S.J., reflects on St. Paul\u27s doctrine of Christian liberty and his attitude toward the Law
Can new heavy gauge bosons be observed in ultra-high energy cosmic neutrino events?
A wide range of models beyond the Standard Model predict charged and neutral
resonances, generically called - and -bosons, respectively. In this
paper we study the impact of such resonances on the deep inelastic scattering
of ultra-high energy neutrinos as well as on the resonant charged current
scattering (Glashow resonance). We find that the effects of
such resonances can not be observed with the Pierre Auger Observatory or any
foreseeable upgrade of it.Comment: 5 pages, 2 figure
L'opposition contre les brevets de Myriad Genetics et leur révocation totale ou partielle en Europe : Premiers enseignements
Les procédures d'opposition contre les brevets de Myriad Genetics sur le gène BRCA1 ont débouché sur la révocation totale d'un premier brevet sur la méthode de diagnostic génétique du cancer du sein, décision de l'Office européen des brevets (OEB) du 18 mai 2004, puis sur la révocation de l'essentiel du second brevet qui portait sur le gène lui-même, le 21 janvier 2005. Ce brevet ne porte plus que sur quelques fragments du gène utilisés comme sondes, les revendications sur les applications diagnostiques ayant été supprimées. Enfin, le 25 janvier 2005, L'OEB a fortement réduit les revendications d'un troisième brevet qui portait sur des mutations particulières du gène. Au lieu des 34 mutations accordées initialement par l'OEB, ce brevet ne porte plus que sur une sonde étroitement définie pour détecter une seule mutation. Et l'usage de cette sonde n'est pas un point de passage obligé. Ces décisions mettent fin au monopole juridique revendiqué par Myriad Genetics sur le gène BRCA1 dans sa totalité et sur le diagnostic génétique du cancer du sein. Elles laissent le champ libre aux généticiens européens qui peuvent développer et mettre en oeuvre leurs méthodes de tests dans le cadre d'une organisation clinique et à caractère non lucratif.The proceedings instituted against three European patents held by the US company Myriad Genetics, on the BRCA1 gene and the breast cancer diagnosis gene, resulted in the total or partial revocation of these patents. These decisions put an end to the legal monopoly claimed by Myriad Genetics on the BRCA1 gene and on breast cancer gene tests, and left the field open to European geneticists to develop and implement their test methods within the framework of a clinical not-for-profit organization. The opposition procedure, through which any actor is allowed to challenge European patents, was used by geneticists doctors in Europe to refuse the emergence of an industrial monopoly on a medical service offered in a clinical context. The decision to revoke or strongly limit these patents was based on the European Patent Office's refusal to establish an invention priority on a sequence that had errors at the time the application was filed by the patent holder, in September 1994. The patent holder was granted an invention priority only on 24 March 1995, when it filed an application for a corrected sequence of the gene. But by then the BRCA1 gene sequence had already been divulged in a public data base, Genbank, from October 1994, notably by Myriad. Myriad Genetics' patents were thus victims of the patent race that prompted the firm to file multiple patent applications on insufficiently validated sequences, and of the conflict between diffusion in the public domain and the novelty requirement. Opposition to the patents, undertaken by a coalition of medical institutions, human genetic societies, two States, Holland and Austria, an environmental protection organization (Greenpeace), and the Swiss Labour Party, made it possible to preserve and develop the clinical economy of genetic tests in Europe. It resulted in amendments to intellectual property laws in France and thus extended the possibility of using compulsory licences for public health purposes to in vitro diagnosis
- …