12,680 research outputs found
Polarized semi-inclusive electroweak structure functions at next-to-leading-order
We present a next-to-leading order (NLO) computation of the full set of
polarized and unpolarized electroweak semi-inclusive DIS (SIDIS) structure
functions, whose knowledge is crucial for a precise extraction of polarized
parton distributions. We focus on the phenomenology of the polarized structure
functions for the kinematical conditions that could be reached in an
Electron-Ion-Collider.
We show that the NLO corrections are sizeable, particularly in the small-
range. We test the sensitivity of these structure functions on certain quark
distributions and compare it to the situation of inclusive DIS and
electromagnetic SIDIS.Comment: 17 pages, 5 figure
Target Fragmentation and Fracture Functions
We analyse recent data on the production of forward neutrons in deep
inelastic scattering at HERA in the framework of a perturbative QCD description
for semi-inclusive processes, which includes fracture functions.Comment: To be published in Proceedings of the Madrid low-x Workshop,
Miraflores de la Sierra, June 18-21, 199
Improved unitarity constraints in Two-Higgs-Doublet-Models
Two-Higgs-Doublet-Models (THDMs) are among the simplest extensions of the
standard model and are intensively studied in the literature. Using on-shell
parameters such as the masses of the additional scalars as input, corresponds
often to large quartic couplings in the underlying Lagrangian. Therefore, it is
important to check if these couplings are for instance in agreement with
perturbative unitarity. The common approach for doing this check is to consider
the two-particle scattering matrix of scalars in the large centre-of-mass
energy limit where only point interactions contribute. We show that this is not
always a valid approximation: the full calculation including all tree-level
contributions at finite energy can lead to much more stringent constraints. We
show how the allowed regions in the parameter space are affected. In
particular, the light Higgs window with a second Higgs below 125 GeV completely
closes for large values of the breaking parameter . We also
compare against the loop corrected constraints, which use also the large
approximation, and find that (effective) cubic couplings are often
more important than radiative corrections.Comment: 8 pages, 6 figure
Spin-Photon Dynamics of Quantum Dots in Two-mode Cavities
A quantum dot interacting with two resonant cavity modes is described by a
two-mode Jaynes-Cummings model. Depending on the quantum dot energy level
scheme, the interaction of a singly doped quantum dot with a cavity photon
generates entanglement of electron spin and cavity states or allows one to
implement a SWAP gate for spin and photon states. An undoped quantum dot in the
same structure generates pairs of polarization entangled photons from an
initial photon product state. For realistic cavity loss rates, the fidelity of
these operations is of order 80%.Comment: 6 pages, 4 figures; extended discussion of experimental
implementatio
The Higgs mass in the CP violating MSSM, NMSSM, and beyond
We discuss the automatised calculation of the Higgs mass in renormalisable
supersymmetric models with complex parameters at the two-loop level. Our setup
is based on the public codes SARAH and SPheno, which can now compute the
two-loop corrections to masses of all neutral scalars in such theories. The
generic ansatz for these calculations and the handling of the `Goldstone Boson
catastrophe' is described. It is shown that we find perfect agreement with
other existing two-loop calculations performed in the DR-bar scheme. We also
use the functionality to derive results for the MSSM and NMSSM not available
before: the Higgs mass in the constrained version of the complex MSSM, and the
impact of CP phases in the two-loop corrections beyond order alpha-strong
alpha-top for the scale invariant NMSSM are briefly analysed.Comment: 19 pages, 14 figure
On Kaon production in e+e- and Semi-inclusive DIS reactions
We consider semi-inclusive unpolarized DIS for the production of charged
kaons and the different possibilities to test the conventionally used
assumptions s-\bar=0 and D_d^{K^+-K^-}=0. The considered tests have the
advantage that they do not require any knowledge of the fragmentation
functions. We also show that measurements of both charged and neutral kaons
would allow the determination of the kaon FFs D_q^{K^++K^-} solely from SIDIS
measurements, and discuss the comparison of (D_u-D_d)^{K^+-K^-} obtained
independently in SIDIS and e+e- reactions. All analysis are performed in LO and
NLO in QCD. The feasibility of the tests to HERMES SIDIS data is considered.Comment: 7 pages, NLO analysis for all presented tests and feasibility to
HERMES data adde
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