23,830 research outputs found

### Double transverse spin asymmetries in vector boson production

We investigate a helicity non-flip double transverse spin asymmetry in vector
boson production in hadron-hadron scattering, which was first considered by
Ralston and Soper at the tree level. It does not involve transversity functions
and in principle also arises in W-boson production for which we present the
expressions. The asymmetry requires observing the transverse momentum of the
vector boson, but it is not suppressed by explicit inverse powers of a large
energy scale. However, as we will show, inclusion of Sudakov factors causes
suppression of the asymmetry, which increases with energy. Moreover, the
asymmetry is shown to be approximately proportional to x_1 g_1(x_1) x_2 \bar
g_1(x_2), which gives rise to additional suppression at small values of the
light cone momentum fractions. This implies that it is negligible for Z or W
production and is mainly of interest for \gamma^* at low energies. We also
compare the asymmetry with other types of double transverse spin asymmetries
and discuss how to disentangle them.Comment: 12 pages, Revtex, 2 Postscript figures, uses aps.sty, epsf.sty;
figures replaced, a few minor other correction

### Factorisation, Parton Entanglement and the Drell-Yan Process

We discuss the angular distribution of the lepton pair in the Drell-Yan
process, hadron+hadron -> \gamma^* X -> l^+ l^- X. This process gives
information on the spin-density matrix \rho^{(q,\bar{q})} of the annihilating
quark-antiquark pair in q+\bar{q} -> l^+ l^-. There is strong experimental
evidence that even for unpolarised initial hadrons \rho^{(q,\bar{q})} is
nontrivial, and therefore the quark-antiquark system is polarised. We discuss
the possibilities of a general \rho^{(q,\bar{q})} -which could be entangled-
and a factorising \rho^{(q,\bar{q})}. We argue that instantons may lead to a
nontrivial \rho^{(q,\bar{q})} of the type indicated by experiments.Comment: 14 pages, 2 figures, comments and references added; to appear in EPJ

### The impact of a 126 GeV Higgs on the neutralino mass

We highlight the differences of the dark matter sector between the
constrained minimal supersymmetric SM (CMSSM) and the next-to-minimal
supersymmetric SM (NMSSM) including the 126 GeV Higgs boson using GUT scale
parameters. In the dark matter sector the two models are quite orthogonal: in
the CMSSM the WIMP is largely a bino and requires large masses from the LHC
constraints. In the NMSSM the WIMP has a large singlino component and is
therefore independent of the LHC SUSY mass limits. The light NMSSM neutralino
mass range is of interest for the hints concerning light WIMPs in the Fermi
data. Such low mass WIMPs cannot be explained in the CMSSM. Furthermore,
prospects for discovery of XENON1T and LHC at 14 TeV are given.Comment: 18 pages, 5 figures, this version is accepted by PLB after
modifications including additional figure

### Spin asymmetries in jet-hyperon production at LHC

We consider polarized Lambda hyperon production in proton-proton scattering,
p p -> (\Lambda^\uparrow jet) jet X, in the kinematical region of the LHC
experiments, in particular the ALICE experiment. We present a new Lambda
polarization observable that arises from the Sivers effect in the fragmentation
process. It can be large even at midrapidity and therefore, is of interest for
high energy hadron collider experiments. Apart from its potential to shed light
on the mechanisms behind the phenomenon of Lambda polarization arising in
unpolarized hadronic collisions, the new observable in principle also allows to
test the possible color flow dependence of single spin asymmetries and the
(non)universality of transverse momentum dependent fragmentation functions.Comment: 11 pages, 10 eps figures; minor modifications, conclusions unchanged,
version to be publishe

### Distributed multilevel optimization for complex structures

Optimization problems concerning complex structures with many design variables may entail an unacceptable computational cost. This problem can be reduced considerably with a multilevel approach: A structure consisting of several components is optimized as a whole (global) as well as on the component level. In this paper, an optimization method is discussed with applications in the assessment of the impact of new design considerations in the development of a structure. A strategy based on fully stressed design is applied for optimization problems in linear statics. A global model is used to calculate the interactions (e.g., loads) for each of the components. These components are then optimized using the prescribed interactions, followed by a new global calculation to update the interactions. Mixed discrete and continuous design variables as well as different design configurations are possible. An application of this strategy is presented in the form of the full optimization of a vertical tail plane center box of a generic large passenger aircraft. In linear dynamics, the parametrization of the component interactions is problematic due to the frequency dependence. Hence, a modified method is presented in which the speed of component mode synthesis is used to avoid this parametrization. This method is applied to a simple test case that originates from noise control. \u

### Can we discover a light singlet-like NMSSM Higgs boson at the LHC?

In the next-to minimal supersymmetric standard model (NMSSM) one additional
singlet-like Higgs boson with small couplings to standard model (SM) particles
is introduced. Although the mass can be well below the discovered 125 GeV Higgs
boson mass its small couplings may make a discovery at the LHC difficult. We
use a novel scanning technique to efficiently scan the whole parameter space
and determine the range of cross sections and branching ratios for the light
singlet-like Higgs boson below 125 GeV. This allows to determine the
perspectives for the future discovery potential at the LHC. Specific LHC
benchmark points are selected representing the salient NMSSM features.Comment: 22 pages, 5 figures, this version is accepted by PLB after minor
modification

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