682 research outputs found
Size Matters: Origin of Binomial Scaling in Nuclear Fragmentation Experiments
The relationship between measured transverse energy, total charge recovered
in the detector, and size of the emitting system is investigated. Using only
very simple assumptions, we are able to reproduce the observed binomial
emission probabilities and their dependences on the transverse energy.Comment: 14 pages, including 4 figure
Nonperturbative and perturbative aspects of photo- and electroproduction of vector mesons
We discuss various aspects of vector meson production, first analysing the
interplay between perturbative and nonperturbative aspects of the QCD
calculation. Using a general method adapted to incorporate both perturbative
and nonpertubative aspects, we show that nonperturbative effects are important
for all experimentally available values of the photon virtuality Q2. We compare
the huge amount of experimental information now available with our theoretical
results obtained using a specific nonperturbative model without free
parameters, showing that quite simple features are able to explain the data.Comment: 19 page
Nonlinear spin wave excitations at low magnetic bias fields
Nonlinear magnetization dynamics is essential for the operation of numerous spintronic devices ranging from magnetic memory to spin torque microwave generators. Examples are microwave assisted switching of magnetic structures and the generation of spin currents at low bias fields by high amplitude ferromagnetic resonance. Here we use X ray magnetic circular dichroism to determine the number density of excited magnons in magnetically soft Ni80Fe20 thin films. Our data show that the common model of nonlinear ferromagnetic resonance is not adequate for the description of the nonlinear behaviour in the low magnetic field limit. Here we derive a model of parametric spin wave excitation, which correctly predicts nonlinear threshold amplitudes and decay rates at high and at low magnetic bias fields. In fact, a series of critical spin wave modes with fast oscillations of the amplitude and phase is found, generalizing the theory of parametric spin wave excitation to large modulation amplitude
Nonperturbative \gamma^* p Interaction in the Diffractive Regime
One of the challenging aspects of electroproduction at high-energy is the
understanding of the transition from real photons to virtual photons in the
GeV^2 region. We study inclusive electroproduction on the proton at small x_B
using a nonperturbative dipole-proton cross section calculated from the gauge
invariant gluon field correlators as input. By quark-hadron duality, we
construct a photon light cone wave function which links the ``hadronic''
behavior at small Q^2 to the ``perturbative'' behavior at large Q^2. It
contains quark masses which implement the transition from constituent quarks at
low Q^2 to current quarks at high Q^2. Our calculation gives a good description
of the structure function at fixed energy for Q^2<=10 GeV^2. Indications for a
chiral transition may already have been seen in the photon-proton cross
section.Comment: 28 pages, LaTeX, eps
Applicability of perturbative QCD to decays
We develop perturbative QCD factorization theorem for the semileptonic heavy
baryon decay , whose form factors are
expressed as the convolutions of hard quark decay amplitudes with universal
and baryon wave functions. Large logarithmic
corrections are organized to all orders by the Sudakov resummation, which
renders perturbative expansions more reliable. It is observed that perturbative
QCD is applicable to decays for velocity transfer
greater than 1.2. Under requirement of heavy quark symmetry, we predict the
branching ratio , and determine
the and baryon wave functions.Comment: 12 pages in Latex file, 3 figures in postscript files, some results
are changed, but the conclusion is the sam
Force-Extension Relations for Polymers with Sliding Links
Topological entanglements in polymers are mimicked by sliding rings
(slip-links) which enforce pair contacts between monomers. We study the
force-extension curve for linear polymers in which slip-links create additional
loops of variable size. For a single loop in a phantom chain, we obtain exact
expressions for the average end-to-end separation: The linear response to a
small force is related to the properties of the unstressed chain, while for a
large force the polymer backbone can be treated as a sequence of Pincus--de
Gennes blobs, the constraint effecting only a single blob. Generalizing this
picture, scaling arguments are used to include self-avoiding effects.Comment: 4 pages, 5 figures; accepted to Phys. Rev. E (Brief Report
Rare Decays of \Lambda_b->\Lambda + \gamma and \Lambda_b ->\Lambda + l^{+} l^{-} in the Light-cone Sum Rules
Within the Standard Model, we investigate the weak decays of and with the light-cone
sum rules approach. The higher twist distribution amplitudes of
baryon to the leading conformal spin are included in the sum rules for
transition form factors. Our results indicate that the higher twist
distribution amplitudes almost have no influences on the transition form
factors retaining the heavy quark spin symmetry, while such corrections can
result in significant impacts on the form factors breaking the heavy quark spin
symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of
baryon are also employed in the sum rules for a comparison, which can
give rise to the form factors approximately 5 times larger than that in terms
of conformal expansion. Utilizing the form factors calculated in LCSR, we then
perform a careful study on the decay rate, polarization asymmetry and
forward-backward asymmetry, with respect to the decays of , .Comment: 38 pages, 15 figures, some typos are corrected and more references
are adde
A phase II study of a human anti-PDGFR alpha monoclonal antibody (olaratumab, IMC-3G3) in previously treated patients with metastatic gastrointestinal stromal tumors
Experimentele farmacotherapi
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
- …