Exponential behavior of the interlayer exchange coupling across non-magnetic metallic superlattices

It is shown that the coupling between magnetic layers separated by non-magnetic metallic superlattices can decay exponentially as a function of the spacer thickness $N$, as opposed to the usual $N^{-2}$ decay. This effect is due to the lack of constructive contributions to the coupling from extended states across the spacer. The exponential behavior is obtained by properly choosing the distinct metals and the superlattice unit cell composition.Comment: To appear in Phys. Rev.

Search for microscopic black holes in pp collisions at √s=8 TeV

This is the pre-print version of the final published paper that is available from the link below.A search for microscopic black holes and string balls is presented, based on a data sample of pp collisions at √s = 8TeV recorded by the CMS experiment at the Large Hadron Collider and corresponding to an integrated luminosity of 12 fb-1. No excess of events with energetic multiparticle _nal states, typical of black hole production or of similar new physics processes, is observed. Given the agreement of the observations with the expected standard model background, which is dominated by QCD multijet production, 95% con_dence level limits are set on the production of semiclassical or quantum black holes, or of string balls, corresponding to the exclusions of masses below 4.3 to 6.2TeV, depending on model assumptions. In addition, model-independent limits are set on new physics processes resulting in energetic multiparticle _nal states

Empirical Studies on Cash Payments

Cash is still the most common means of daily payments. The large number of cash payments is supported by a costly distribution system in which retailers, banks and central banks participate. Currency is issued in a range of bank note and coin denominations to facilitate efficiency in cash payments. The purpose of this thesis is to study the performance of a currency range in practice. It presents a number of empirical studies on cash payments at the individual payment level, whereby cash payments are viewed as the outcome of a choice process. This type of analysis calls for labor-intensive data collection methods and the development of a sophisticated econometric model. This thesis introduces such a model for cash payments, and it reviews its application to three unique data sets of cash payments. The data concern payments in the Netherlands before and after the transition from the guilder to the euro in 2002, and payments in an experimental setting. The estimation results allow for an assessment of the use of different bank note and coin denominations in cash payments, and of possible preferences for one of more denominations. Currency research generally approaches currency use from a macroeconomic point of view. The novelty of this thesis is that it contributes to currency research by focusing on individual cash payments.Jeanine Kippers (1973) obtained her master´s degree in econometrics from the Erasmus University Rotterdam in 1997. In the same year she was employed by De Nederlandsche Bank. She participated in the preparations of the cash changeover from guilder to euro in 2002, and contributed to the development of a European cash distribution system and the restructuring of the national distribution system. During her employment at the central bank she started her research on currency use, which resulted in several papers that have been published or are currently under review. In January 2004 she joined the Pensionand Insurance Supervisory authority, as a policy advisor in the (international) field of insurance supervision

Study of exclusive two-photon production of W+W- in pp collisions at √s=7 TeV and constraints on anomalous quartic gauge couplings

A search for exclusive or quasi-exclusive W+W- production by photon-photon interactions, pp -> p(*)W(+)W(-)p(*), at \/s = 7 TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 fb(-1). Events are selected by requiring a mu(+/-)mu(-/+) vertex with no additional associated charged tracks and dilepton transverse momentum p(T)(mu(+/-)mu(-/+)) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.2 +/- 0.4 signal events with 0.84 +/- 0.15 background. The tail of the dilepton p(T) distribution is studied for deviations from the standard model. No events are observed with p(T) > 100 GeV. Model-independent upper limits are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters a(0,c)(W)/A(2) with a dipole form factor and an energy cutoff A(cutoff) = 500 GeV are of the order of 10(-4)

Searches for long-lived charged particles in pp collisions at √s =7 and 8 TeV

Results of searches for heavy stable charged particles produced in pp collisions at √s =7 and 8 TeV are presented corresponding to an integrated luminosity of 5.0 fb⁻¹ and 18.8 fb⁻¹, respectively. Data collected with the CMS detector are used to study the momentum, energy deposition, and time-of-flight of signal candidates. Leptons with an electric charge between e/3 and 8e, as well as bound states that can undergo charge exchange with the detector material, are studied. Analysis results are presented for various combinations of signatures in the inner tracker only, inner tracker and muon detector, and muon detector only. Detector signatures utilized are long time-of-flight to the outer muon system and anomalously high (or low) energy deposition in the inner tracker. The data are consistent with the expected background, and upper limits are set on the production cross section of long-lived gluinos, scalar top quarks, and scalar τ leptons, as well as pair produced long-lived leptons. Corresponding lower mass limits, ranging up to 1322 GeV/c² for gluinos, are the most stringent to date

Measurement of the top-quark mass in all-jets tt events in pp collisions at root = 7 TeV

The mass of the top quark is measured using a sample of tt¯ candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at s√=7 TeV in 2011 and corresponds to an integrated luminosity of 3.54 fb−1 . The mass is reconstructed for each event employing a kinematic fit of the jets to a tt¯ hypothesis. The top-quark mass is measured to be 173.49±0.69(stat.)±1.21(syst.) GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of 173.54±0.33(stat.)±0.96(syst.) GeV

Measurement of the ratio of the inclusive 3-jet cross section to the inclusive 2-jet cross section in pp collisions at root s=7 TeV and first determination of the strong coupling constant in the TeV range

A measurement is presented of the ratio of the inclusive 3-jet cross section to the inclusive 2-jet cross section as a function of the average transverse momentum, , of the two leading jets in the event. The data sample was collected during 2011 at a proton-proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 5.0 fb(-1). The strong coupling constant at the scale of the Z boson mass is determined to be alpha(S)(M-Z) = 0.1148 +/- 0.0014 (exp.) +/- 0.0018 (PDF) +/- 0.0050 (theory), by comparing the ratio in the range 0.42 < 1.39 TeV to the predictions of perturbative QCD at next-to-leading order. This is the first determination of alpha(S)(M-Z) from measurements at momentum scales beyond 0.6 TeV. The predicted ratio depends only indirectly on the evolution of the parton distribution functions of the proton such that this measurement also serves as a test of the evolution of the strong coupling constant. No deviation from the expected behaviour is observed