6594228
Scattering of gauge, matter, and moduli fields from intersecting branes
Abstract We calculate various tree-level (disk) scattering amplitudes involving gauge, matter and moduli fields in IIB toroidal orbifold/orientifold backgrounds with D9-, D5- respectively D7-, D3-branes or via T -duality D6-branes in type IIA compactifications. In type IIB the D-branes may have non-vanishing fluxes on their world-volume. From these results we extract the moduli and flux dependence of the tree-level gauge couplings, the metrics for the moduli and matter fields. The non-vanishing fluxes correspond in the T -dual type IIA description to intersecting D6-branes. This allows us to determine the moduli dependence of the tree-level matter field metrics in the effective action of intersecting D6-brane models. In addition we derive the physical Yukawa couplings with their correct normalization.
117476620
On closed-string twist-field correlators and their open-string descendants
In a recent paper we have proposed the possibility that the lightest massive string states could be identified with open strings living at intersections of D-branes forming small angles. In this note, we reconsider the relevant twist-field correlation functions and perform the analysis of the sub-dominant physical poles in the various channels. Our derivation is new in that it is based on the algebraic procedure for the construction of open string models starting from their closed-string `parents' rather than on the stress-tensor method. We also indicate possible generalizations and diverse applications of our approach.
5682028
Computation of D-brane instanton induced superpotential couplings: Majorana masses from string theory
We perform a detailed conformal field theory analysis of D2-brane instanton effects in four-dimensional type IIA string vacua with intersecting D6-branes. In particular, we explicitly compute instanton induced fermion two-point couplings which play the role of perturbatively forbidden Majorana mass terms for right-handed neutrinos or MSSM {mu} terms. These results can readily be extended to higher-dimensional operators. In concrete realizations of such nonperturbative effects, the Euclidean D2-brane has to wrap a rigid, supersymmetric cycle with strong constraints on the zero-mode structure. Their implications for type IIA compactifications on the T{sup 6}/(Z{sub 2}xZ{sub 2}) orientifold with discrete torsion are analyzed. We also construct a local supersymmetric GUT-like model allowing for a class of Euclidean D2-branes whose fermionic zero modes meet all the constraints for generating Majorana masses in the phenomenologically allowed regime. Together with perturbatively realized Dirac masses, these nonperturbative couplings give rise to the seesaw mechanism.
118374533
Dynamical supersymmetry breaking in intersecting brane models
In this paper we study dynamical supersymmetry breaking in absence of gravity with the matter content of the minimal supersymmetric standard model. The hidden sector of the theory is a strongly coupled gauge theory, realized in terms of microscopic variables which condensate to form mesons. The supersymmetry breaking scalar potential combines F, D terms with instanton generated interactions in the Higgs-mesons sector. We show that for a large region in parameter space the vacuum breaks in addition to supersymmetry also electroweak gauge symmetry. We furthermore present local D-brane configurations that realize these supersymmetry breaking patterns.
53533600
String constraints on discrete symmetries in MSSM type II quivers
A bstractWe study the presence of discrete gauge symmetries in D-brane semi-realistic compactifications. After establishing the constraints on the transformation behaviour of the chiral matter for the presence of a discrete gauge symmetry we perform a systematic search for discrete gauge symmetries within local semi-realistic D-brane realizations, based on four D-brane stacks, of the MSSM and the MSSM with three right-handed neutrinos. The systematic search reveals that Proton hexality, a discrete symmetry which ensures the absence of R-parity violating terms as well as the absence of dangerous dimension 5 proton decay operators, is only rarely realized. Moreover, none of the semi-realistic local D-brane configurations exhibit any family dependent discrete gauge symmetry.
118063728
Mass Hierarchies versus proton Decay in MSSM Orientifold Compactifications
We review two systematic bottom-up analyses of MSSM quivers recently performed by the authors. We extend the analysis of arXiv:0905.3379 by including constraints arising from proton decay via dimension 5 operators and present all four-stack quivers in the Madrid embedding which satisfy this additional constraint. Furthermore, we investigate and make precise the interplay between mass hierarchies obtained via factorizable Yukawa textures and the presence of dimension 5 proton decay operators in MSSM orientifold compactifications. We discuss this issue in a five-stack quiver, first presented in arXiv:0909.4292, which exhibits proper mass hierarchies and no rapid proton decay.
110604426
Strip detector design for ATLAS and HERA-B using two-dimensional device simulation
Abstract Irradiation scenarios were simulated in order to evaluate different technology and design options for silicon strip detectors exposed to a high luminosity environment. Two-dimensional process and device simulations were performed to get an insight into the device behaviour. The boundary condition of the free oxide regions between the strips was evaluated thoroughly to obtain correct field distributions. Using these results the formation of electron accumulation layers on the surface of the p-side and the depletion voltage dependence on the strip geometry can be explained. We investigated the “blocking implant” and the “spray implant” techniques as promising candidates for the n-side isolation of irradiated detectors. The main drawback of the “blocking implanted” devices is the increase of the electric field with increasing oxide charges. This implies the danger of impact ionization in irradiated devices. A “spray implanted” isolation layer leads to the highest electric field in the non-irradiated state which has the advantage of a better testability. Small gaps between strips as used in charge division readout reduce electric fields and leakage currents.
55210719
DEPFET—detectors: new developments
Abstract The Depleted Field Effect Transistor (DEPFET) detector–amplifier structure forms the basis of a variety of detectors being developed at the MPI semiconductor laboratory. These detectors are foreseen to be used in astronomy and particle physics as well as other fields of science. The detector developments are described together with some intended applications. They comprise the X-ray astronomy missions XEUS and SIMBOL-X as well as the vertex detector of the planned International Linear Collider (ILC). All detectors are produced in the MPI semiconductor laboratory that has a complete silicon technology available.
120421514
GAS SYSTEM FOR ALEPH TPC
Abstract Operation of the time projection chamber of the ALEPH experiment at LEP requires a high-purity argon/methane gas mixture supplied to the detector under stable conditions to ensure minimum signal attenuation throughout the 43 m 3 detector volume (max. 2.2 m drift length) and maintain near-constant electron drift velocity in the gas over extended periods of time. Design considerations for a gas system to fulfil these conditions are presented and details given of the construction, operational aspects and of the achieved performance.
50340039
Observation of a Narrow Resonance at 10.02-GeV in e+ e- Annihilations
Abstract The ϒ′ state has been observed as a narrow resonance at M ( ϒ ′) = 10.02 ± 0.02 GeV in e + e − annihilations, using a NaI and lead-glass detector in the DORIS storage ring at DESY. The ratio Г ee Г had /Г tot of electronic, hadronic, and total widths has been measured to be 0.32 ± 0.13 keV. The parameters of the Г particle have also been determined to be/ M (Г)
120584442
Modelling of the space-to-drift-time relationship of the ATLAS monitored drift-tube chambers in the presence of magnetic fields
Abstract The ATLAS muon spectrometer uses tracking chambers consisting of up to 5 m long drift tubes filled with Ar : CO 2 ( 93 : 7 ) at 3 bar. The chambers are run in a average toroidal magnetic field of 0.4 T created by 8 air core coils. They provide a track-point accuracy of 40 μ m if the space-to-drift-time relationship r ( t ) is known with 20 μ m accuracy. The magnetic field B influences the electron drift inside the tubes: the maximum drift time t max = 700 ns increases by ≈ 70 ns / T 2 B 2 . B varies by up to ± 0.4 T along the tubes of the chambers mounted near the magnet coils which translates into a variation of t max of up to 45 ns. The dependence of r ( t ) on B must be taken into account. Test-beam measurements show that the electron drift in case of B ≠ 0 can be modelled with the required accuracy by a Langevin equation with a friction term which is slightly non-linear in the drift velocity.