Combining QED and QCD transverse-momentum resummation for Z boson production at hadron colliders

We consider the transverse-momentum ($q_T$) distribution of $Z$ bosons produced in hadronic collisions. At small values of $q_T$, we perform the analytic resummation of the logarithmically enhanced QED contributions up to next-to-leading logarithmic accuracy, including the mixed QCD-QED contributions at leading logarithmic accuracy. Resummed results are consistently matched with the next-to-leading fixed-order results (i.e. $\mathcal{O}(\alpha^2)$) at small, intermediate and large values of $q_T$. We combine the QED corrections with the known QCD results at next-to-next-to-leading order ($\mathcal{O}(\alpha_S^2)$) and next-to-next-to-leading logarithmic accuracy. We show numerical results at LHC and Tevatron energies, studying the impact of the QED corrections and providing an estimate of the corresponding perturbative uncertainty. Our analytic results for the combined QED and QCD resummation, obtained through an extension of the $q_T$ resummation formalism in QCD, are valid for the production of generic neutral and colourless high-mass systems in hadronic collision.Comment: 13 pages, 3 figure

Airbag Products Liability Litigation: State Common Law Tort Claims Are Not Automatically Preempted by Federal Legislation

This article addresses an important and recurring issue of federalism, and attempts to resolve the tensions that exist between federal and state laws in the context of recent automobile airbag litigation. The authors trace the evolution of the preemption doctrine as it relates to airbag litigation, and write further as to how manufacturers adapt, developing business and ethical strategies of compliance to concurrent state and federal regulation. Two recent important decisions involving no airbag litigation, Tebbetts v. Ford Motor Co. and Wilson v. Pleasant, are interpretive of two provisions of the Safety Act. The former case discussed a preemption clause, and the latter a state common law savings clause. These cases have posed important and controversial legal and ethical issues that have an enormous impact on auto manufacturers\u27 exposure to liability. This article will discuss the issues emanating from the decisions in Tebbetts and Wilson with major emphasis on the doctrine of preemption, the Supremacy Clause of the U.S. Constitution, state police powers, the potential of the judiciary to shape business policy, and the ethical obligations of auto manufacturers to the many stakeholders involved. In addition, the authors proffer suggestions regarding the best road to travel when there are different options for meeting the overlapping layers of federal and state safety requirements

Threshold Resummed Spectra in B -> Xu l nu Decays in NLO (I)

We evaluate thresholds resummed spectra in B -> Xu l nu decays in next-to-leading order. We present results for the distribution in E_X and in m_X^2/E_X^2, for the distribution in E_X and E_l and for the distribution in E_X, where E_X and m_X are the energy and the invariant mass of the final hadronic state Xu respectively and E_l is the energy of the charged lepton. We explicitly show that all these spectra (where there is no integration over the hadronic energy) can be directly related to the photon spectrum in B -> Xs gamma via short-distance coefficient functions.Comment: 33 pages, no figures. The section on the double distribution in the hadron and electron energies has been largely rewritten with an improved resummation scheme. Small stylistic changes in the remaining sections. References adde

100 Gbps PON L-band downstream transmission using IQ-MZM CD digital pre-compensation and DD ONU receiver

We propose a downstream direct-detection 100G-PON solution aided by chromatic dispersion digital pre-compensation using an IQ-MZM, allowing L-band operation and 29 dB power budget with low ONU complexity and without requiring single-sideband modulation

Polarization proximity effect in isolator crystal pairs

We experimentally studied the polarization dynamics (orientation and ellipticity) of near infrared light transmitted through magnetooptic Yttrium Iron Garnet crystal pairs using a modified balanced detection scheme. When the pair separation is in the sub-millimeter range, we observed a proximity effect in which the saturation field is reduced by up to 20%. 1D magnetostatic calculations suggest that the proximity effect originates from magnetostatic interactions between the dipole moments of the isolator crystals. This substantial reduction of the saturation field is potentially useful for the realization of low-power integrated magneto-optical devices.Comment: submitted to Optics Letter

100 Gbps/λ PON downstream O- And C-band alternatives using direct-detection and linear-impairment equalization [Invited]

The future-generation passive optical network (PON) physical layer, targeting 100 Gbps/wavelength, will have to deal with severe optoelectronics bandwidth and chromatic dispersion limitations. In this paper, largely extending our Optical Fiber Communication Conference (OFC) 2020 invited paper, we review 100 Gbps/wavelength PON downstream alternatives over standard single-mode fiber in the O- and C-bands, analyzing three modulation formats (PAM-4, partial-response PAM-4, and PAM-8), two types of direct-detection receivers (APD- and SOA $+$+ PIN-based), and three digital reception strategies (unequalized, feed-forward equalized, and decision-feedback equalized). We evaluate by means of simulations the performance of these alternatives under different optoelectronics bandwidth and dispersion scenarios, identifying O-band feasible solutions able to reach 20 km of fiber and an optical path loss of at least 29 dB over a wide wavelength range of operation. Finally, we compare two digitally precompensated modulation schemes that are highly tolerant of chromatic dispersion, showing a possible extension to C-band operation, preserving direct-detection and linear-impairment equalization at the optical network unit side