172 research outputs found
Diphoton Production at Hadron Colliders and New Contact Interactions
We explore the capability of the Tevatron and LHC to place limits on the
possible existence of flavor-independent contact
interactions which can lead to an excess of diphoton events with large
invariant masses. Assuming no departure from the Standard Model is observed, we
show that the Tevatron will eventually be able to place a lower bound of
0.5-0.6 TeV on the scale associated with this new contact interaction. At the
LHC, scales as large as 3-6 TeV may be probed with suitable detector cuts and
an integrated luminosity of .Comment: LaTex, 12pages plus 5 figures(available on request), SLAC-PUB-657
Louis-Ferdinand CĂ©line, literary genius or national pariah? Defining moral parameters for influential cultural figures, post- Charlie Hebdo
In January 2011 the French Minister of Culture, FrĂ©dĂ©ric Mitterrand, withdrew Louis-Ferdinand CĂ©line from a list of famous French authors specifically selected for a national celebration of culture. This bold decision polarized opinion: while many welcomed Mitterrandâs intervention, a number of prominent writers, some of them Jewish, opposed it on the grounds that CĂ©lineâs abhorrent political beliefs â expressed in three anti-Semitic pamphlets and his flirtation with Nazism- should in no way detract from his literary genius. In the light of this controversy, and of the rise in anti-Semitism following the Charlie Hebdo attacks of January 2015, this paper proposes CĂ©line as a vital case study of the moral parameters a democratic nation should apply to a culturally important figure whose political views are deemed unacceptably reactionary
Proanthocyanidin oxidation of Arabidopsis seeds is altered in mutant of the high-affinity nitrate transporter NRT2.7
This article appears in:Special Issue: Nutrient Sensing and SignallingNRT2.7 is a seed-specific high-affinity nitrate transporter controlling nitrate content in Arabidopsis mature seeds. The objective of this work was to analyse further the consequences of the nrt2.7 mutation for the seed metabolism. This work describes a new phenotype for the nrt2.7-2 mutant allele in the Wassilewskija accession, which exhibited a distinctive pale-brown seed coat that is usually associated with a defect in flavonoid oxidation. Indeed, this phenotype resembled those of tt10 mutant seeds defective in the laccase-like enzyme TT10/LAC15, which is involved in the oxidative polymerization of flavonoids such as the proantocyanidins (PAs) (i.e. epicatechin monomers and PA oligomers) and flavonol glycosides. nrt2.7-2 and tt10-2 mutant seeds displayed the same higher accumulation of PAs, but were partially distinct, since flavonol glycoside accumulation was not affected in the nrt2.7-2 seeds. Moreover, measurement of in situ laccase activity excluded a possibility of the nrt2.7-2 mutation affecting the TT10 enzymic activity at the early stage of seed development. Functional complementation of the nrt2.7-2 mutant by overexpression of a full-length NRT2.7 cDNA clearly demonstrated the link between the nrt2.7 mutation and the PA phenotype. However, the PA-related phenotype of nrt2.7-2 seeds was not strictly correlated to the nitrate content of seeds. No correlation was observed when nitrate was lowered in seeds due to limited nitrate nutrition of plants or to lower nitrate storage capacity in leaves of clca mutants deficient in the vacuolar anionic channel CLCa. All together, the results highlight a hitherto-unknown function of NRT2.7 in PA accumulation/oxidation.Laure C. David, Julie Dechorgnat, Patrick Berquin, Jean Marc Routaboul, Isabelle Debeaujon, Françoise Daniel-Vedele and Sylvie Ferrario-Mér
First Measurement of Pure Electron Shakeoff in the ÎČ Decay of Trapped 6He+ Ions
ExpĂ©rience GANIL/SPIRAL/LIRATThe electron shakeoff probability of 6Li2+ ions resulting from the ÎČ- decay of 6He+ ions has been measured with high precision using a specially designed recoil ion spectrometer. This is the first measurement of a pure electron shakeoff following nuclear ÎČ decay, not affected by multielectron processes such as Auger cascades. In this ideal textbook case for the application of the sudden approximation, the experimental ionization probability was found to be Psoexp=0.023â39(36) in perfect agreement with simple quantum mechanical calculations
Constraints on Four Fermion Contact Interactions from Precise Electroweak Measurements
We establish constraints on a general four-fermion contact interaction from
precise measurements of electroweak parameters. We compute the one-loop
contribution for the leptonic width, anomalous magnetic, weak-magnetic,
electric and weak dipole moments of leptons in order to extract bounds on the
energy scale of these effective interactions.Comment: 16 pages, RevTeX, two figure
Uses and Abuses of Effective Lagrangians
Motivated by past and recent analyses we critically re-examine the use of
effective lagrangians in the literature to constrain new physics and to
determine the `physics reach' of future experiments. We demonstrate that many
calculations, such as those involving anomalous trilinear gauge-boson
couplings, either considerably overestimate loop-induced effects, or give
ambiguous answers. The source of these problems is the use of cutoffs to
evaluate the size of such operators in loop diagrams. In contrast to other
critics of these loop estimates, we prove that the inclusion of
nonlinearly-realized gauge invariance into the low-energy lagrangian is
irrelevant to this conclusion. We use an explicit example using known
multi-Higgs physics above the weak scale to underline these points. We show how
to draw conclusions regarding the nature of the unknown high-energy physics
without making reference to low-energy cutoffs.Comment: 36 page
Primary processes: from atoms to diatomic molecules and clusters
International audienceThis article presents a short review of the main progresses achieved at the GANIL facilities during the last thirty years in the field of ion-atom and ion-diatomic molecule collisions. Thanks to the wide range of projectile energies and species available on the different beam lines of the facility, elementary processes such as electron capture, ionization and excitation have been extensively studied. Beside primary collision mechanisms, the relaxation processes of the collision partners after the collision have been another specific source of interest. Progresses on other fundamental processes such as Young type interferences induced by ion-molecule collisions or shake off ionization resulting from nuclear beta decay are also presented. 1. Introduction For the electronic structures of atoms and molecules, precise theoretical knowledge and high-resolution experimental data are available. But the complete understanding of dynamic processes in atomic collisions remains a challenge, due to large theoretical problems in describing time-dependent many-particle reactions, and to experimental difficulties in performing complete experiments in which all relevant quantities are accessible. Elementary collisions involving ions, atoms and molecules play an important role in many gaseous and plasma environments, where they provide both the heating and cooling mechanisms. The study of such collisions is thus not only of fundamental importance, it is also essential for the understanding of large-scale systems such as astrophysical plasmas, planetary atmospheres, gas discharge lasers, semiconductor processing plasmas, and fusion plasmas. Collisions between ions and atoms (or simple molecules) give also access to the elementary processes responsible for energy transfer in ion-matter and ion-biological molecule collisions. Complete knowledge of these elementary processes is thus of primordial importance for ion induced modification of materials as well as for radiolysis, radiotherapy and biological damages due to radiation exposure
Effective-Lagrangian approach to precision measurements: the anomalous magnetic moment of the muon
We investigate the use of effective Lagrangians to describe the effects on
high-precision observables of physics beyond the Standard Model. Using the
anomalous magnetic moment of the muon as an example, we detail the use of
effective vertices in loop calculations. We then provide estimates of the
sensitivity of new experiments measuring the muon's to the scale of
physics underlying the Standard Model.Comment: 22 pages, 1 figure, PHYZZX & EPSF, report #s UCRHEP-T98, UM_TH-92-17,
and NSF-ITP-92-122I Revision: The paper will now TeX properly; the content is
unchange
QCD Corrections and Non-standard Three Vector Boson Couplings in Production at Hadron Colliders
The process p\,p\hskip-7pt\hbox{^{^{(\!-\!)}}} \rightarrow W^{+} W^{-} + X
\rightarrow \ell^+_1 \nu_1 \ell^-_2 \bar \nu_2 + X is calculated to for general and conserving couplings (). The prospects for probing the couplings in this reaction are
explored. The impact of QCD corrections and various
background processes on the observability of non-standard couplings in
production at the Tevatron and the Large Hadron Collider (LHC) is
discussed in detail. Sensitivity limits for anomalous couplings are
derived at next-to-leading order for the Tevatron and LHC center of mass
energies, and are compared to the bounds which can be achieved in other
processes. Unless a jet veto or a cut on the total transverse momentum of the
hadrons in the event is imposed, the QCD corrections and
the background from top quark production decrease the sensitivity of
p\,p\hskip-7pt\hbox{^{^{(\!-\!)}}} \rightarrow W^{+} W^{-} + X \rightarrow
\ell^+_1 \nu_1 \ell^-_2 \bar \nu_2 + X to anomalous couplings by a
factor two to five.Comment: REVTEX 3, 62 pages, 21 Figures (not included available upon request),
the postscript file of the complete paper is available at
ftp://ucdhep.ucdavis.edu/han/ww/ww_paper.p
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