233 research outputs found
Non local parity transformations and anomalies
We present an alternative derivation of the parity anomaly for a massless
Dirac field in 2+1 dimensions coupled to a gauge field. The anomaly functional,
a Chern-Simons action for the gauge field, is obtained from the non-trivial
Jacobian corresponding to a non local symmetry of the Pauli-Villars regularized
action. That Jacobian is well-defined, finite, and yields the standard
Chern-Simons term when the cutoff tends to infinity.Comment: 10 pages, Latex fil
Electroweak and QCD corrections to Higgs production via vector-boson fusion at the LHC
The radiative corrections of the strong and electroweak interactions are
calculated at next-to-leading order for Higgs-boson production in the
weak-boson-fusion channel at hadron colliders. Specifically, the calculation
includes all weak-boson fusion and quark--antiquark annihilation diagrams to
Higgs-boson production in association with two hard jets, including all
corresponding interferences. The results on the QCD corrections confirm that
previously made approximations of neglecting s-channel diagrams and
interferences are well suited for predictions of Higgs production with
dedicated vector-boson fusion cuts at the LHC. The electroweak corrections,
which also include real corrections from incoming photons and leading
heavy-Higgs-boson effects at two-loop order, are of the same size as the QCD
corrections, viz. typically at the level of 5-10% for a Higgs-boson mass up to
\sim 700 GeV. In general, both types of corrections do not simply rescale
differential distributions, but induce distortions at the level of 10%. The
discussed corrections have been implemented in a flexible Monte Carlo event
generator.Comment: 33 pages, LaTeX, 24 postscript figure
Generalized parity transformations in the regularized Chern-Simons theory
We study renormalization effects in the Abelian Chern-Simons (CS) action.
These effects can be non-trivial when the gauge field is coupled to dynamical
matter, since the regularization of the UV divergences in the model forces the
introduction of a parity even piece in the gauge field action. This changes the
classical (odd) transformation properties of the pure CS action. This effect,
already discussed for the case of a lattice regularization by F. Berruto, M.C.
Diamantini and P. Sodano in hep-th/0004203, is also present when the theory is
defined in the continuum and, indeed, it is a manifestation of a more general
`anomalous' effect, since it happens for every regularization scheme. We
explore the physical consequences of this anomaly. We also show that
generalized, nonlocal parity transformations can be defined in such a way that
the regularized theory is odd, and that those transformations tend to the usual
ones when the cutoff is removed. These generalized transformations play a role
that is tantamount to the deformed symmetry corresponding to Ginsparg-Wilson
fermions [2] (in an even number of spacetime dimensions).Comment: 16 pages, LaTeX, references added and typos correcte
Fluoropyrimidine sensitivity of human MCF-7 breast cancer cells stably transfected with human uridinehosphorylase
The relationship between uridine phosphorylase (UP) expression level in cancer cells and the tumour sensitivity to fluoropyrimidines is unclear. In this study, we found that UP overexpression by gene transfer, and the subsequent efficient metabolic activation of 5-fluorouracil (5-FU) by the ribonucleotide pathway, does not increase the fluoropyrimidine sensitivity of MCF-7 human cancer cells. © 2001 Cancer Research Campaign http://www.bjcancer.co
Electroweak corrections to Higgs-strahlung off W/Z bosons at the Tevatron and the LHC with HAWK
The associate production of Higgs bosons with W or Z bosons, known as
Higgs-strahlung, is an important search channel for Higgs bosons at the hadron
colliders Tevatron and LHC for low Higgs-boson masses. We refine a previous
calculation of next-to-leading-order electroweak corrections (and recalculate
the QCD corrections) upon including the leptonic decay of the W/Z bosons,
thereby keeping the fully differential information of the 2-lepton + Higgs
final state. The gauge invariance of the W/Z-resonance treatment is ensured by
the use of the complex-mass scheme. The electroweak corrections, which are at
the level of -(5-10)% for total cross sections, further increase in size with
increasing transverse momenta p_T in differential cross sections. For instance,
for p_T,H >~ 200GeV, which is the interesting range at the LHC, the electroweak
corrections to WH production reach about -14% for M_H = 120GeV. The described
corrections are implemented in the HAWK Monte Carlo program, which was
initially designed for the vector-boson-fusion channel, and are discussed for
various distributions in the production channels pp / p \bar p -> H + l nu_l /
l^-l^+ / nu_l \bar nu_l + X.Comment: 22 p
In vitro and in vivo reversal of resistance to 5-fluorouracil in colorectal cancer cells with a novel stealth double-liposomal formulation
Drug resistance is a major cause of treatment failure in cancer chemotherapy, including that with the extensively prescribed antimetabolite, 5-fluorouracil (5-FU). In this study, we tried to reverse 5-FU resistance by using a double-punch strategy: combining 5-FU with a biochemical modulator to improve its tumoural activation and encapsulating both these agents in one same stealth liposome. Experiments carried out in the highly resistant, canonical SW620 human colorectal model showed a up to 80% sensitisation to 5-FU when these cells were treated with our liposomal formulation. Results with this formulation demonstrated 30% higher tumoural drug uptake, better activation with increased active metabolites including critical-5-fluoro-2-deoxyuridine-5-monophosphate, superior inhibition (98%) of tumour thymidylate synthase, and subsequently, higher induction of both early and late apoptosis. Drug monitoring showed that higher and sustained exposure was achieved in rats treated with liposomal formulation. When examined in a xenograft animal model, our dual-agent liposomal formulation caused a 74% reduction in tumour size with a mean doubling in survival time, whereas standard 5-FU failed to exhibit significant antiproliferative activity as well as to increase the lifespan of tumour-bearing mice. Taken collectively, our data suggest that resistance to 5-FU can be overcome through a better control of its intratumoural activation and the use of an encapsulated formulation
Higgs Physics: Theory
I review the theoretical aspects of the physics of Higgs bosons, focusing on
the elements that are relevant for the production and detection at present
hadron colliders. After briefly summarizing the basics of electroweak symmetry
breaking in the Standard Model, I discuss Higgs production at the LHC and at
the Tevatron, with some focus on the main production mechanism, the gluon-gluon
fusion process, and summarize the main Higgs decay modes and the experimental
detection channels. I then briefly survey the case of the minimal
supersymmetric extension of the Standard Model. In a last section, I review the
prospects for determining the fundamental properties of the Higgs particles
once they have been experimentally observed.Comment: 21 pages, 15 figures. Talk given at the XXV International Symposium
on Lepton Photon Interactions at High Energies (Lepton Photon 11), 22-27
August 2011, Mumbai, Indi
On Coordinate Transformations in Planar Noncommutative Theories
We consider planar noncommutative theories such that the coordinates verify a
space-dependent commutation relation. We show that, in some special cases, new
coordinates may be introduced that have a constant commutator, and as a
consequence the construction of Field Theory models may be carried out by an
application of the standard Moyal approach in terms of the new coordinates. We
apply these ideas to the concrete example of a noncommutative plane with a
curved interface. We also show how to extend this method to more general
situations.Comment: 20 pages, 1 figure. references adde
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