5,715 research outputs found
Forward Physics at the LHC: within and beyond the Standard Model
We review the detection capabilities in the forward direction of the various
LHC experiments together with the associated physics programme. A selection of
measurements accessible with near-beam instrumentation in various sectors (and
extensions) of the Standard Model (SM) is outlined, including QCD (diffractive
and elastic scattering, low-x parton dynamics, hadronic Monte Carlos for
cosmic-rays), electroweak processes in gamma-gamma interactions, and Higgs
physics (vector-boson-fusion and central exclusive production).Comment: 9 pages, 18 figs. Lectures given at the LAWHEP'07 School (Sao Miguel
das Missoes, Brazil, 3-7 Dec 2007) to appear in Braz. J. Phys. Also presented
in HLPW08 (Spa, Belgium, 6-8 Mar 2008) AIP Conf. Proceeds, to appear; and in
HANUC European Grad. School (Jyvaskyla, Finland, 25-29 Aug. 2008
Drosophila as a model system to study nonautonomous mechanisms affecting tumour growth and cell death
The study of cancer has represented a central focus in medical research for over a century. The great complexity and constant evolution of the pathology require the use of multiple research model systems and interdisciplinary approaches. This is necessary in order to achieve a comprehensive understanding into the mechanisms driving disease initiation and progression, to aid the development of appropriate therapies. In recent decades, the fruit fly Drosophila melanogaster and its associated powerful genetic tools have become a very attractive model system to study tumour-intrinsic and non-tumour-derived processes that mediate tumour development in vivo. In this review, we will summarize recent work on Drosophila as a model system to study cancer biology. We will focus on the interactions between tumours and their microenvironment, including extrinsic mechanisms affecting tumour growth and how tumours impact systemic host physiology
A synthetic model of the gravitational wave background from evolving binary compact objects
Modeling the stochastic gravitational wave background from various
astrophysical sources is a key objective in view of upcoming observations with
ground- and space-based gravitational wave observatories such as Advanced LIGO,
VIRGO, eLISA and PTA. We develop a synthetic model framework that follows the
evolution of single and binary compact objects in an astrophysical context. We
describe the formation and merger rates of binaries, the evolution of their
orbital parameters with time and the spectrum of emitted gravitational waves at
different stages of binary evolution. Our approach is modular and allows us to
test and constrain different ingredients of the model, including stellar
evolution, black hole formation scenarios and the properties of binary systems.
We use this framework in the context of a particularly well-motivated
astrophysical setup to calculate the gravitational wave background from several
types of sources, including inspiraling stellar-mass binary black holes that
have not merged during a Hubble time. We find that this signal, albeit weak,
has a characteristic shape that can help constrain the properties of binary
black holes in a way complementary to observations of the background from
merger events. We discuss possible applications of our framework in the context
of other gravitational wave sources, such as supermassive black holes.Comment: 13 pages, 6 figures. Accepted for publication in Phys. Rev. D.
Revised to reflect final versio
The charge conjugation quantum number in multiquark systems
We discuss the charge conjugation quantum number for tetraquarks or
meson-meson molecules, seen as possible interpretations of the newly found
charmonium-like resonances.Comment: 7 pages, 1 figure, based on a talk given at the Joint Meeting
Heidelberg-Liege-Paris-Wroclaw (HLPW08): Three Days of Strong Interactions
and Astrophysics, Spa, March 6-8, 2008, Eqs. (18)-(25) corrected, text
slightly polished, conclusions unchange
Integral equation for gauge invariant quark Green's function
We consider gauge invariant quark two-point Green's functions in which the
gluonic phase factor follows a skew-polygonal line. Using a particular
representation for the quark propagator in the presence of an external gluon
field, functional relations between Green's functions with different numbers of
segments of the polygonal lines are established. An integral equation is
obtained for the Green's function having a phase factor along a single straight
line. The related kernels involve Wilson loops with skew-polygonal contours and
with functional derivatives along the sides of the contours.Comment: 7 pages; talk given at the Joint Meeting
Heidelberg-Liege-Paris-Wroclaw, Spa, 6-8 March 2008; to appear in the
Proceedings (AIP
Core-collapse supernova neutrinos and neutrino properties
Core-collapse supernovae are powerful neutrino sources. The observation of a
future (extra-)galactic supernova explosion or of the relic supernova neutrinos
might provide important information on the supernova dynamics, on the supernova
formation rate and on neutrino properties. One might learn more about unknown
neutrino properties either from indirect effects in the supernova (e.g. on the
explosion or on in the r-process) or from modifications of the neutrino time or
energy distributions in a detector on Earth. Here we will discuss in particular
possible effects of CP violation in the lepton sector. We will also mention the
interest of future neutrino-nucleus interaction measurements for the precise
knowledge of supernova neutrino detector response to electron neutrinos.Comment: 9 pages, 5 figures, Proceedings to "Three days of Strong Interactions
& Astrophysics HLPW08", 6-8 March 2008, SP
Two-photon decay of pseudoscalar quarkonia
We report on our recent evaluation of the two-photon width of the
pseudoscalar quarkonia, eta_c(nS) and eta_b(nS) in an approach based on
Heavy-Quark Spin Symmetry (HQSS). To what concerns the 1S state eta_c, our
parameter-free computation agrees with experiments, as well as most of other
theoretical works. On the other hand, our computation for the 2S-state looks 2S
like a confirmation that there may exist an anomaly related to the decay of
eta_c(2S), especially in the light of the new preliminary result of the Belle
collaboration. We also point out that the essentially model-independent ratio
of eta_b two-photon width to the Upsilon leptonic width and the eta_b
two-photon width could be used to extract the strong coupling constant alpha_s.Comment: Presented by T.N. Pham at the Joint Meeting
Heidelberg-Liege-Paris-Wroclaw (HLPW08), Spa, Belgium, 6-8 March 2008, 9
pages, 2 figures, LaTeX, uses aip-6s.clo, aipproc.cls and aipxfm.sty
(included
Pions in the quark matter phase diagram
The relationship between mesonic correlations and quantum condensates in the
quark matter phase diagram is explored within a quantum field theoretical
approach of the Nambu and Jona-Lasinio (NJL) type. Mean-field values in the
scalar meson and diquark channels are order parameters signalling the
occurrence of quark condensates, entailing chiral symmetry breaking (chi SB)
and color superconductivity (2SC) in quark matter. We investigate the spectral
properties of scalar and pseudoscalar meson excitations in the phase diagram in
Gaussian approximation and show that outside the chi SB region where the pion
is a zero-width bound state, there are two regions where it can be considered
as a quasi-bound state with a lifetime exceeding that of a typical heavy-ion
collision fireball: (A) the high-temperature chi SB crossover region at low
densities and (B) the high-density color superconducting phase at temperatures
below 100 MeV.Comment: presented by D. Zablocki at the Joint Meeting
Heidelberg-Liege-Paris-Wroclaw (HLPW08), Spa, Belgium, 6-8 March 2008, 10
pages, 5 figures, LaTeX, uses aip-6s.clo, aipproc.cls and aipxfm.sty
(included
Axions and polarisation of quasars
We present results showing that, thanks to axion-photon mixing in external
magnetic fields, it is actually possible to produce an effect similar to the
one needed to explain the large-scale coherent orientations of quasar
polarisation vectors in visible light that have been observed in some regions
of the sky.Comment: Contributed to "Three days of Strong Interactions & Astrophysics,
Heidelberg-Liege-Paris-Wroclaw", 6/3/2008-8/3/2008, Spa, Belgium. To be
published in AIP proceeding
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