A parton shower based on factorization of the quantum density matrix 414 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/45/031/45031525.pdf - Text Version by Nagy, Zoltan (Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)); Soper,
Davison E. (Oregon Univ., Eugene, OR (United States). Inst. of Theoretical Science); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany) Read MoreCollapse

[en]

We present rst results from a new parton shower event generator, DEDUCTOR. Anticipating
a need for an improved treatment of parton color and spin, the structure of the generator
is based on the quantum density matrix in color and spin space. So far, DEDUCTOR implements
only a standard spin-averaged treatment of spin in parton splittings. Although DEDUCTOR
implements an improved treatment of color, in this paper we present results in the
standard leading color approximation so that we can compare to the generator PYTHIA.
The algorithms used incorporate a virtuality based shower ordering parameter and massive
initial state bottom and charm quarks.$$$$

We present searches for the standard model Higgs boson using up to 9.7 fb^{-1}
of pp-bar collisions collected with the D0 detector at Fermi lab. The analyses consist
in a series of distinct final states and are sensitive to Higgs boson masses (M_{H})
ranging from 90 GeV to 200 GeV. These analyses are combined and allow to exclude a
standard model Higgs boson at 95% Confidence Level (C.L.) in the range 90 GeV < M_{H}
< 101 GeV and 157 GeV < M_{H} < 178 GeV, with an expected exclusion in the
range 155 GeV < M_{H} < 175 GeV. An excess of data of about two Gaussian standard
deviations is seen in the range 120 GeV < M_{H} < 145 GeV, consistent with
the observation of a boson with a mass of 125 GeV at the Large Hadron Collider and
with the evidence for a particle decaying to bb-bar at the Tevatron. (authors)$$$$

Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs.
experimental data by Actis, S. (Paul-Scherrer-Institute Wuerenlingen and Villigen, Villigen (Switzerland));
Arbuzov, A. (Joint Institute for Nuclear Research, Dubna (Russian Federation). Bogoliubov
Lab. of Theoretical Physics); Balossini, G. (Pavia Univ. (Italy). Dipt. di Fisica
Nucleare e Teorica; INFN, Pavia (Italy)) (and others); Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Working group on radiative
corrections and Monte Carlo generators for low energies Read MoreCollapse

[en]

We present the achievements of the last years of the experimental and theoretical
groups working on hadronic cross section measurements at the low energy e^{+}e^{-}
colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on τ
decays. We sketch the prospects in these fields for the years to come. We emphasise
the status and the precision of the Monte Carlo generators used to analyse the hadronic
cross section measurements obtained as well with energy scans as with radiative return,
to determine luminosities and τ decays. The radiative corrections fully or approximately
implemented in the various codes and the contribution of the vacuum polarisation are
discussed. (orig.)$$$$

Based on the external field approach and the differential form of Ward identity, we
derive a more compact formula for the particle-number susceptibility in QED_{3}
at finite temperature. Using the zero frequency approximation the numerical value
of the particle-number susceptibility is calculated in the Dyson–Schwinger approach
for the case that the number of fermion flavours equals one and two, respectively.
An enhanced fluctuation of the particle-number density is observed across the transition
temperature, which should be an essential characteristic of chiral phase transition
in QED_{3} (the physics of elementary particles and fields)$$$$

Cosmological horizons and reconstruction of quantum field theories 643 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/39/011/39011696.pdf - Text Version by Dappiaggi, C.; Pinamonti, N. (Hamburg Univ. (Germany). 2. Inst. fuer Theoretische
Physik; Trento Univ., Povo (Italy). Istituto Nazionale di Alta Matematica ''F. Severi''
- GNFM); Moretti, V. (Trento Univ. (Italy). Dipt. di Matematica; Istituto Nazionale
di Fisica Nucleare - Gruppo Collegato di Trento, Povo (Italy)); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany) Read MoreCollapse

[en]

As a starting point for this manuscript, we remark how the cosmological horizon of
a certain class of Friedmann-Robertson-Walker backgrounds shares some non trivial
geometric properties with null infinity in an asymptotically flat spacetime. Such
a feature is generalized to a larger class of expanding spacetimes M admitting a geodesically
complete cosmological horizon J^{-} common to all co-moving observers. This
property is later exploited in order to recast, in a cosmological background, some
recent results for a linear scalar quantum field theory in spacetimes asymptotically
flat at null infinity. Under suitable hypotheses on M - valid for de Sitter spacetime
and some other FRW spacetimes obtained by perturbing deSitter space - the algebra
of observables for a Klein-Gordon field is mapped into a subalgebra of the algebra
of observables W(J^{-}) constructed on the cosmological horizon. There is
exactly one pure quasifree state λ on W(J^{-}) which fulfills a suitable energy
positivity condition with respect to a generator related with the cosmological time
displacements. Furthermore λ induces a preferred physically meaningful quantum state
λ_{M} for the quantum theory in the bulk. If M admits a timelike Killing generator
preserving J^{-}, then the associated self-adjoint generator in the GNS representation
of λ_{M} has positive spectrum (i.e. energy). Moreover λ_{M} turns
out to be invariant under every symmetry of the bulk metric which preserves the cosmological
horizon. In the case of an expanding de Sitter spacetime, λ_{M} coincides
with the Euclidean (Bunch-Davies) vacuum state, hence being Hadamard in this case.
Remarks on the validity of the Hadamard property for λ_{M} in more general
spacetimes are presented. (orig.)$$$$

Production of charged ρ meson in bottom hadron charmed decays and the effect of the
finite width correction of the ρ meson by Zhang, Zhen-Hua (University of South China, School of Nuclear Science and Technology,
Hengyang, Hunan (China); Huazhong Normal University, Institute of Particle Physics,
Wuhan (China)); Yang, Ya-Dong (Huazhong Normal University, Institute of Particle Physics,
Wuhan (China)); Guo, Xin-Heng (Beijing Normal University, College of Nuclear Science
and Technology, Beijing (China)); Lue, Gang (Henan University of Technology, College
of Science, Zhengzhou (China)); Wiranata, Anton (University of South China, School
of Nuclear Science and Technology, Hengyang, Hunan (China); Lawrence Berkeley National
Laboratory, Nuclear Science Division, MS 70R0319, Berkeley, CA (United States)) Read MoreCollapse

[en]

We calculate the branching ratio of a bottom hadron decaying into a charmed hadron
and a charged ρ meson within the QCD factorization approach. We consider the effect
of the finite width correction of the ρ meson. Our numerical calculation shows an
obvious correction because of this effect. We find that the finite width effect of
the ρ meson reduces the branching ratios by about 9 % to 11 % for bottom meson decay
channels: B^{+} → D^{0}ρ^{+}, B^{0} → D^{-}ρ^{+},
and B^{0}_{s} → D^{-}_{s}ρ^{+}, and increases
the branching ratio by about 10 % for Λ_{b}^{0} → Λ_{c}^{+}ρ^{-}.
(orig.)$$$$

Looking for meson molecules in B decays by Nielsen, Marina; Navarra, Fernando S. (Universidade de Sao Paulo (IF/USP), SP (Brazil).
Inst. de Fisica); Bediaga, Ignacio (Centro Brasileiro de Pesquisas Fisicas (CBPF),
Rio de Janeiro, RJ (Brazil)); Sociedade Brasileira de Fisica, Sao Paulo, SP (Brazil) Read MoreCollapse

[en]

Full text: We discuss the possibility of observing a loosely bound molecular state
in a B three-body hadronic decay. In particular we use the QCD sum rule approach to
study a η' - π molecular current. We consider an isovector- scalar I^{G} J^{PC}
= 1^{-} 0^{++} molecular current and we use the two-point and three-point
functions to study the mass and decay width of such state. We consider the contributions
of condensates up to dimension six and we work at leading order in α_{s}.
We found a mass a little bigger than the η' - π threshold, indicating the possibility
of a loosely bound molecular state. We got a small width for the η' - π → K^{+}K^{-}
decay around 10 MeV. We have proposed that a loosely bound molecular state should
leave a particular signal in the Dalitz plot. A loosely bound molecular state of two
particles can only exist when the relative momentum between these two particles is
small. Therefore, one expect a small line in the middle of the Dalitz plot, approximately
in the region where there is a hole in the line characterizing a vector resonance.
This signal is different from any signal characterizing the normal quark-antiquark
mesons, and could be used to identify the existence of loosely bound molecular states.
(author)$$$$

Cosmic string interactions in a Lorentz invariance violation framework 44 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/41/131/41131115.pdf - Text Version by Ferreira, Cristine Nunes (Instituto Federal de Educacao, Ciencia e Tecnologia Fluminense,
Campos dos Goytacases, RJ (Brazil)); Helayel Neto, Jose Abdalla; Lima, Carlos Eduardo
Campos (Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)); Sociedade Brasileira de Fisica (SBF), Sao Paulo, SP (Brazil) Read MoreCollapse

Angular correlations in three-jet events in ep collisions at HERA 931 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/39/112/39112429.pdf - Text Version by Chekanov, S.; Derrick, M.; Magill, B. (Argonne National Laboratory, Illinois (United
States)) (and others); Deutsches Elektronen-Synchrotron (DESY). Hamburg (Germany); ZEUS Collaboration Read MoreCollapse

[en]

Three-jet production in deep inelastic ep scattering and photoproduction was investigated
with the ZEUS detector at HERA using an integrated luminosity of 127 pb^{-1}.
Measurements of differential cross sections are presented as functions of angular
correlations between the three jets in the final state and the proton-beam direction.
These correlations provide a stringent test of perturbative QCD and show sensitivity
to the contributions from different colour configurations. Fixed-order perturbative
QCD calculations assuming the values of the colour factors C_{F}, C_{A}
and T_{F} as derived from a variety of gauge groups were compared to the measurements
to study the underlying gauge group symmetry. The measured angular correlations in
the deep inelastic ep scattering and photoproduction regimes are consistent with the
admixture of colour configurations as predicted by SU(3) and disfavour other symmetry
groups, such as SU(N) in the limit of large N$$$$

Right-handed sector lepto-genesis by Frigerio, M. (CEA Saclay, Service de Physique Theorique, 91 - Gif-sur-Yvette (France));
Hambye, Th. (Madrid Universidad Autonoma, Instituto de F sica Te rica, Cantoblanco
(Spain)); Ma, E. (California Univ., Physics Dept., Riverside, California (United States)); CEA Saclay, Service de Physique Theorique, 91 - Gif-sur-Yvette (France) Read MoreCollapse

[en]

Instead of creating the observed baryon asymmetry of the universe by the decay of
right-handed (RH) neutrinos to left-handed leptons, we propose to generate it dominantly
by the decay of the RH neutrinos to RH leptons. This mechanism turns out to be successful
in large regions of the parameter space. It may work, in particular, at a scale as
low as a few TeV, with no need to invoke quasi-degenerate RH neutrino masses to resonantly
enhance the asymmetry. Such a possibility can be probed experimentally by the observation
at colliders of a singlet charged Higgs particle and of RH neutrinos. Other mechanisms
which may lead to successful lepton-genesis from the RH lepton sector interactions
are also briefly presented. The incorporation of these scenarios in left-right symmetric
and unified models is discussed. (authors)$$$$